Sample records for nanoparticle 2d arrays

  1. Conductance based characterization of structure and hopping site density in 2D molecule-nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    McCold, Cliff E.; Fu, Qiang; Howe, Jane Y.; Hihath, Joshua

    2015-09-01

    Composite molecule-nanoparticle hybrid systems have recently emerged as important materials for applications ranging from chemical sensing to nanoscale electronics. However, creating reproducible and repeatable composite materials with precise properties has remained one of the primary challenges to the implementation of these technologies. Understanding the sources of variation that dominate the assembly and transport behavior is essential for the advancement of nanoparticle-array based devices. In this work, we use a combination of charge-transport measurements, electron microscopy, and optical characterization techniques to determine the role of morphology and structure on the charge transport properties of 2-dimensional monolayer arrays of molecularly-interlinked Au nanoparticles. Using these techniques we are able to determine the role of both assembly-dependent and particle-dependent defects on the conductivities of the films. These results demonstrate that assembly processes dominate the dispersion of conductance values, while nanoparticle and ligand features dictate the mean value of the conductance. By performing a systematic study of the conductance of these arrays as a function of nanoparticle size we are able to extract the carrier mobility for specific molecular ligands. We show that nanoparticle polydispersity correlates with the void density in the array, and that because of this correlation it is possible to accurately determine the void density within the array directly from conductance measurements. These results demonstrate that conductance-based measurements can be used to accurately and non-destructively determine the morphological and structural properties of these hybrid arrays, and thus provide a characterization platform that helps move 2-dimensional nanoparticle arrays toward robust and reproducible electronic systems.Composite molecule-nanoparticle hybrid systems have recently emerged as important materials for applications ranging from

  2. Terasonic Excitations in 2D Gold Nanoparticle Arrays in a Water Matrix as Revealed by Atomistic Simulations

    DOE PAGES

    Bolmatov, Dima; Zhernenkov, Mikhail; Zav’yalov, Dmitry; ...

    2016-08-19

    Here in this work we report on terahertz phononic excitations in 2D gold nanoparticle arrays in a water matrix through a series of large-scale molecular dynamics simulations. For the first time, we observe acoustic Dirac-like crossings in H (H 2O) atomic (molecular) networks which emerge due to an intraband phononic scattering. These crossings are the phononic fingerprints of ice-like arrangements of H (H 2O) atomic (molecular) networks at nanometer scale. We reveal how phononic excitations in metallic nanoparticles and the water matrix reciprocally impact on one another providing the mechanism for the THz phononics manipulation via structural engineering. In addition,more » we show that by tuning the arrangement of 2D gold nanoparticle assemblies the Au phononic polarizations experience sub-terahertz hybridization (Kohn anomaly) due to surface electron-phonon relaxation processes. This opens the way for the sound control and manipulation in soft matter metamaterials at nanoscale.« less

  3. Optical diffraction in ordered VO2 nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Lopez, Rene; Feldman, Leonard; Haglund, Richard

    2006-03-01

    The potential of oxide electronic materials as multifunctional building blocks is one of the driving concepts of the field. In this presentation, we show how nanostructured particle arrays with long-range order can be used to modulate an optical response through exploiting the metal-insulator transition of vanadium dioxide. Arrays of VO2 nanoparticles with long-range order were fabricated by pulsed laser deposition in an arbitrary pattern defined by focused ion-beam lithography. The interaction of light with the nanoparticles is controlled by the nanoparticle size, spacing and geometrical arrangement and by switching between the metallic and semiconducting phases of VO2. In addition to the near-infrared surface plasmon response observed in previous VO2 studies, the VO2 nanoparticle arrays exhibit size-dependent optical resonances in the visible region that likewise show an enhanced optical contrast between the semiconducting and metallic phases. The collective optical response as a function of temperature gives rise to an enhanced scattering state during the evolving phase transition, while the incoherent coupling between the nanoparticles produces an order-disorder-order transition.

  4. Deterministic Coupling of Quantum Emitters in 2D Materials to Plasmonic Nanocavity Arrays.

    PubMed

    Tran, Toan Trong; Wang, Danqing; Xu, Zai-Quan; Yang, Ankun; Toth, Milos; Odom, Teri W; Aharonovich, Igor

    2017-04-12

    Quantum emitters in two-dimensional materials are promising candidates for studies of light-matter interaction and next generation, integrated on-chip quantum nanophotonics. However, the realization of integrated nanophotonic systems requires the coupling of emitters to optical cavities and resonators. In this work, we demonstrate hybrid systems in which quantum emitters in 2D hexagonal boron nitride (hBN) are deterministically coupled to high-quality plasmonic nanocavity arrays. The plasmonic nanoparticle arrays offer a high-quality, low-loss cavity in the same spectral range as the quantum emitters in hBN. The coupled emitters exhibit enhanced emission rates and reduced fluorescence lifetimes, consistent with Purcell enhancement in the weak coupling regime. Our results provide the foundation for a versatile approach for achieving scalable, integrated hybrid systems based on low-loss plasmonic nanoparticle arrays and 2D materials.

  5. Optical properties of anisotropic 3D nanoparticles arrays

    NASA Astrophysics Data System (ADS)

    Santiago, E. Y.; Esquivel-Sirvent, R.

    2017-07-01

    The optical properties of 3D periodic arrays of spheroidal Au nanoparticles are calculated using a Bruggeman effective medium approximation. The optical response of the supra-crystal depends on the volume fraction of the nanoparticles and their aspect or size ratio (major/minor axis). All the nanoparticles have the same orientation, and this defines an anisotropic dielectric function of the crystal. As a function of the filling fraction, while keeping the size ratio fixed, the maximum in the extinction spectra along the major and minor axes does not show a significant change. However, for a fixed filling fraction, varying the aspect ratio of the particles induces a shift of several hundred of nanometers in the maximum of the extinction spectra along the major axis and almost no changes along the minor axis. Depending on the aspect ratio and the filling fraction, we show that the supra-crystal has three regimes with different values of an effective plasma frequency. Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

  6. Optical Epitaxial Growth of Gold Nanoparticle Arrays.

    PubMed

    Huang, Ningfeng; Martínez, Luis Javier; Jaquay, Eric; Nakano, Aiichiro; Povinelli, Michelle L

    2015-09-09

    We use an optical analogue of epitaxial growth to assemble gold nanoparticles into 2D arrays. Particles are attracted to a growth template via optical forces and interact through optical binding. Competition between effects determines the final particle arrangements. We use a Monte Carlo model to design a template that favors growth of hexagonal particle arrays. We experimentally demonstrate growth of a highly stable array of 50 gold particles with 200 nm diameter, spaced by 1.1 μm.

  7. Ordered Array of Gold Nanoparticles Promoted by Functional Peptides

    NASA Astrophysics Data System (ADS)

    Matsukawa, Nozomu; Yamashita, Ichiro

    2011-05-01

    It was successfully demonstrated that 5-nm-diameter gold nanoparticles (GNPs) with 15% size distribution, the surface of which was modified by the synthesized peptides composed of the carbonaceous material affinity peptide (NHBP-1), linker of 11 amino acids and C-terminal cysteine, self-assembled into a two-dimensional (2D) ordered array on a silicon substrate in a spin drying process. NHBP-1 generated an attractive force large enough for the GNP to make 2D collections of GNPs in the course of the spin drying process, and the long linker of 11 amino acids cancelled out the ill effect of size distribution of GNP on the 2D ordered array formation.

  8. Formation of precise 2D Au particle arrays via thermally induced dewetting on pre-patterned substrates

    PubMed Central

    Ji, Ran

    2011-01-01

    Summary The fabrication of precise 2D Au nanoparticle arrays over a large area is presented. The technique was based on pre-patterning of the substrate before the deposition of a thin Au film, and the creation of periodic particle arrays by subsequent dewetting induced by annealing. Two types of pre-patterned substrates were used: The first comprised an array of pyramidal pits and the second an array of circular holes. For the dewetting of Au films on the pyramidal pit substrate, the structural curvature-driven diffusion cooperates with capillarity-driven diffusion, resulting in the formation of precise 2D particle arrays for films within a structure dependent thickness-window. For the dewetting of Au films on the circular hole substrate, the periodic discontinuities in the films, induced by the deposition, can limit the diffusion paths and lead to the formation of one particle per individual separated region (holes or mesas between holes), and thus, result in the evolution of precise 2D particle arrays. The influence of the pre-patterned structures and the film thickness is analyzed and discussed. For both types of pre-patterned substrate, the Au film thickness had to be adjusted in a certain thickness-window in order to achieve the precise 2D particle arrays. PMID:21977445

  9. Au-coated 3-D nanoporous titania layer prepared using polystyrene-b-poly(2-vinylpyridine) block copolymer nanoparticles.

    PubMed

    Shin, Won-Jeong; Basarir, Fevzihan; Yoon, Tae-Ho; Lee, Jae-Suk

    2009-04-09

    New nanoporous structures of Au-coated titania layers were prepared by using amphiphilic block copolymer nanoparticles as a template. A 3-D template composed of self-assembled quaternized polystyrene-b-poly(2-vinylpyridine) (Q-PS-b-P2VP) block copolymer nanoparticles below 100 nm was prepared. The core-shell-type nanoparticles were well ordered three-dimensionally using the vertical immersion method on the substrate. The polar solvents were added to the polymer solution to prevent particle merging at 40 degrees C when considering the interaction between polymer nanoparticles and solvents. Furthermore, Au-coated PS-b-P2VP nanoparticles were prepared using thiol-capped Au nanoparticles (3 nm). The 3-D arrays with Au-coated PS-b-P2VP nanoparticles as a template contributed to the preparation of the nanoporous Au-coated titania layer. Therefore, the nanoporous Au-coated titania layer was fabricated by removing PS-b-P2VP block copolymer nanoparticles by oxygen plasma etching.

  10. Tumor stroma-containing 3D spheroid arrays: A tool to study nanoparticle penetration.

    PubMed

    Priwitaningrum, Dwi L; Blondé, Jean-Baptiste G; Sridhar, Adithya; van Baarlen, Joop; Hennink, Wim E; Storm, Gert; Le Gac, Séverine; Prakash, Jai

    2016-12-28

    Nanoparticle penetration through tumor tissue after extravasation is considered as a key issue for tumor distribution and therapeutic effects. Most tumors possess abundant stroma, a fibrotic tissue composed of cancer-associated fibroblasts (CAFs) and extracellular matrix (ECM), which acts as a barrier for nanoparticle penetration. There is however a lack of suitable in vitro systems to study the tumor stroma penetration of nanoparticles. In the present study, we developed and thoroughly characterized a 3D co-culture spheroidal array to mimic tumor stroma and investigated the penetration of silica and PLGA nanoparticles in these spheroids. First, we examined human breast tumor patient biopsies to characterize the content and organization of stroma and found a high expression of alpha-smooth muscle actin (α-SMA; 40% positive area) and collagen-1 (50% positive area). Next, we prepared homospheroids of 4T1 mouse breast cancer cells or 3T3 mouse fibroblasts alone as well as heterospheroids combining 3T3 and 4T1 cells in different ratios (1:1 and 5:1) using a microwell array platform. Confocal live imaging revealed that fibroblasts distributed and reorganized within 48h in heterospheroids. Furthermore, immunohistochemical staining and gene expression analysis showed a proportional increase of α-SMA and collagen in heterospheroids with higher fibroblast ratios attaining 35% and 45% positive area at 5:1 (3T3:4T1) ratio, in a good match with the clinical breast tumor stroma. Subsequently, we studied the penetration of high and low negatively charged fluorescent silica nanoparticles (30nm; red and 100 or 70nm; green; zeta potential: -40mV and -20mV) and as well as Cy5-conjugated pegylated PLGA nanoparticles (200nm, -7mV) in both homo- and heterospheroid models. Fluorescent microscopy on spheroid cryosections after incubation with silica nanoparticles showed that 4T1 homospheroids allowed a high penetration of about 75-80% within 24h, with higher penetration in case of the

  11. Enhanced photoelectrochemical properties of TiO2 nanorod arrays decorated with CdS nanoparticles

    PubMed Central

    Xie, Zheng; Liu, Xiangxuan; Wang, Weipeng; Liu, Can; Li, Zhengcao; Zhang, Zhengjun

    2014-01-01

    TiO2 nanorod arrays (TiO2 NRAs) sensitized with CdS nanoparticles were fabricated via successive ion layer adsorption and reaction (SILAR), and TiO2 NRAs were obtained by oxidizing Ti NRAs obtained through oblique angle deposition. The TiO2 NRAs decorated with CdS nanoparticles exhibited excellent photoelectrochemical and photocatalytic properties under visible light, and the one decorated with 20 SILAR cycles CdS nanoparticles shows the best performance. This can be attributed to the enhanced separation of electrons and holes by forming heterojunctions of CdS nanoparticles and TiO2 NRAs. This provides a promising way to fabricate the material for solar energy conversion and wastewater degradation. PMID:27877718

  12. Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells

    PubMed Central

    Zan, Xiaoli; Wang, Chenxu

    2016-01-01

    Abstract To circumvent the bottlenecks of non‐flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil–water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm−2 μm −1, up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nm, and a wide linear range of 87 nm to 100 μm. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well‐tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil–water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society. PMID:26918612

  13. Nanoparticle Langmuir-Blodgett Arrays for Sensing of CO and NO2 Gases

    NASA Astrophysics Data System (ADS)

    Luby, Stefan; Jergel, Matej; Majkova, Eva; Siffalovic, Peter; Chitu, Livia; Rella, Roberto; Manera, Maria Grazia; Caricato, Anna-Paola; Luches, Armando; Martino, Maurizio

    Metal oxide sensors with active Fe2O3 and CoFe2O4 nanoparticle arrays were studied. Sensing nanoparticle films from 1, 2, 4 or 7 monolayers were deposited by Langmuir-Blodgett technique. Sensors are formed on the alumina substrates equipped with heating meander. Langmuir-Blodgett layers were heated or UV irradiated to remove the insulating surfactant. Sensing properties were studied towards CO or NO2 gases in concentrations between 0.5 and 100 ppm in mixture with the dry air. Best response values Igas/Iair were obtained with CoFe2O4 device being 3 for 100 ppm of CO and with Fe2O3 device being (38)-1 for 0.5 ppm of NO2.

  14. Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells.

    PubMed

    Zan, Xiaoli; Bai, Hongwei; Wang, Chenxu; Zhao, Faqiong; Duan, Hongwei

    2016-04-04

    To circumvent the bottlenecks of non-flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil-water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm(-2) μM(-1), up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nM, and a wide linear range of 87 nM to 100 μM. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well-tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil-water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  15. Nanoscale coupling of photons to vibrational excitation of Ag nanoparticle 2D array studied by scanning tunneling microscope light emission spectroscopy.

    PubMed

    Katano, Satoshi; Toma, Koji; Toma, Mana; Tamada, Kaoru; Uehara, Yoichi

    2010-11-28

    Scanning tunneling microscope light emission (STM-LE) spectroscopy has been utilized to elucidate the luminescence phenomena of Ag nanoparticles capped with myristate (myristate-capped AgNP) and 2-methyl-1-propanethiolate (C(4)S-capped AgNP) on the dodecanethiol-precovered Au substrate. The STM imaging revealed that myristate-capped AgNPs form an ordered hexagonal array whereas C(4)S-capped AgNPs show imperfect ordering, indicating that a shorter alkyl chain of C(4)S-capped AgNP is not sufficient to form rigid interdigitation. It should be noted that such a nanoparticle ordering affects the luminescence properties of the Ag nanoparticle. We found that the STM-LE is only detected from the Ag nanoparticles forming the two-dimensional superlattice. This indicates that the STM-LE of the Ag nanoparticle is radiated via the collective excitation of the local surface plasmon resonance (LSPR) spread over the Ag nanoparticles. Note that the STM-LE spectra of the Ag nanoparticles exhibit spike-like peaks superimposed on the broad light emission peak. Using Raman spectroscopy, we concluded that the spike-like structure appearing in the STM-LE spectra is associated with the vibrational excitation of the molecule embedded between Ag nanoparticles.

  16. Chemical growth of ZnO nanorod arrays on textured nanoparticle nanoribbons and its second-harmonic generation performance

    NASA Astrophysics Data System (ADS)

    Gui, Zhou; Wang, Xian; Liu, Jian; Yan, Shanshan; Ding, Yanyan; Wang, Zhengzhou; Hu, Yuan

    2006-07-01

    On the basis of the highly oriented ZnO nanoparticle nanoribbons as the growth seed layer (GSL) and solution growth technique, we have synthesized vertical ZnO nanorod arrays with high density over a large area and multi-teeth brush nanostructure, respectively, according to the density degree of the arrangement of nanoparticle nanoribbons GSL on the glass substrate. This controllable and convenient technique opens the possibility of creating nanostructured film for industrial fabrication and may represent a facile way to get similar structures of other compounds by using highly oriented GSL to promote the vertical arrays growth. The growth mechanism of the formation of the ordered nanorod arrays is also discussed. The second-order nonlinear optical coefficient d31 of the vertical ZnO nanorod arrays measured by the Maker fringes technique is 11.3 times as large as that of d36 KH 2PO 4 (KDP).

  17. Three-dimensional scanning near field optical microscopy (3D-SNOM) imaging of random arrays of copper nanoparticles: implications for plasmonic solar cell enhancement.

    PubMed

    Ezugwu, Sabastine; Ye, Hanyang; Fanchini, Giovanni

    2015-01-07

    In order to investigate the suitability of random arrays of nanoparticles for plasmonic enhancement in the visible-near infrared range, we introduced three-dimensional scanning near-field optical microscopy (3D-SNOM) imaging as a useful technique to probe the intensity of near-field radiation scattered by random systems of nanoparticles at heights up to several hundred nm from their surface. We demonstrated our technique using random arrays of copper nanoparticles (Cu-NPs) at different particle diameter and concentration. Bright regions in the 3D-SNOM images, corresponding to constructive interference of forward-scattered plasmonic waves, were obtained at heights Δz ≥ 220 nm from the surface for random arrays of Cu-NPs of ∼ 60-100 nm in diameter. These heights are too large to use Cu-NPs in contact of the active layer for light harvesting in thin organic solar cells, which are typically no thicker than 200 nm. Using a 200 nm transparent spacer between the system of Cu-NPs and the solar cell active layer, we demonstrate that forward-scattered light can be conveyed in 200 nm thin film solar cells. This architecture increases the solar cell photoconversion efficiency by a factor of 3. Our 3D-SNOM technique is general enough to be suitable for a large number of other applications in nanoplasmonics.

  18. Vortex unbinding in 2D classical JJ arrays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Minnhagen, Petter

    1998-05-15

    Vortices for 2D superfluids are introduced and are described in terms of a 2D Coulomb gas. The 2D classical JJ array is modeled by a 2D XY-model and a mapping between the XY-model and the Coulomb gas is given. The physical properties of a JJ array are then given in terms of the corresponding Coulomb gas properties. First aspects of the Kosterlitz-Thouless vortex unbinding transitions are reviewed. Consequences for the resistance as well as the frequency dependent conductivity are described. Next the vortex unbinding induced by an external current is considered with Consequencies for the non-linear IV-characteristics. Finally some somemore » effects of a perpendicular magnetic field are discussed in terms of an interplay between free vortices and bound vortex pairs.« less

  19. Interactions of DNA coated upconversion nanoparticles with 2D materials

    NASA Astrophysics Data System (ADS)

    Giust, Davide; Lucío, María. Isabel; Muskens, Otto L.; Kanaras, Antonios G.

    2018-02-01

    In this work we investigated the nature of quenching between different types of 2D materials (WS2, MoS2 and graphene oxide) and oligonucleotide coated-upconversion nanoparticles. This study contributes towards the efficient design of biosensors based on 2D materials and DNA-coated upconversion nanoparticles.

  20. 2D Ruddlesden-Popper Perovskites Microring Laser Array.

    PubMed

    Zhang, Haihua; Liao, Qing; Wu, Yishi; Zhang, Zhaoyi; Gao, Qinggang; Liu, Peng; Li, Meili; Yao, Jiannian; Fu, Hongbing

    2018-04-01

    3D organic-inorganic hybrid perovskites have featured high gain coefficients through the electron-hole plasma stimulated emission mechanism, while their 2D counterparts of Ruddlesden-Popper perovskites (RPPs) exhibit strongly bound electron-hole pairs (excitons) at room temperature. High-performance solar cells and light-emitting diodes (LEDs) are reported based on 2D RPPs, whereas light-amplification devices remain largely unexplored. Here, it is demonstrated that ultrafast energy transfer along cascade quantum well (QW) structures in 2D RPPs concentrates photogenerated carriers on the lowest-bandgap QW state, at which population inversion can be readily established enabling room-temperature amplified spontaneous emission and lasing. Gain coefficients measured for 2D RPP thin-films (≈100 nm in thickness) are found about at least four times larger than those for their 3D counterparts. High-density large-area microring arrays of 2D RPPs are fabricated as whispering-gallery-mode lasers, which exhibit high quality factor (Q ≈ 2600), identical optical modes, and similarly low lasing thresholds, allowing them to be ignited simultaneously as a laser array. The findings reveal that 2D RPPs are excellent solution-processed gain materials potentially for achieving electrically driven lasers and ideally for on-chip integration of nanophotonics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Nanoparticle sorting in silicon waveguide arrays

    NASA Astrophysics Data System (ADS)

    Zhao, H. T.; Zhang, Y.; Chin, L. K.; Yap, P. H.; Wang, K.; Ser, W.; Liu, A. Q.

    2017-08-01

    This paper presents the optical fractionation of nanoparticles in silicon waveguide arrays. The optical lattice is generated by evanescent coupling in silicon waveguide arrays. The hotspot size is tunable by changing the refractive index of surrounding liquids. In the experiment, 0.2-μm and 0.5-μm particles are separated with a recovery rate of 95.76%. This near-field approach is a promising candidate for manipulating nanoscale biomolecules and is anticipated to benefit the biomedical applications such as exosome purification, DNA optical mapping, cell-cell interaction, etc.

  2. Plasmon-induced optical switching of electrical conductivity in porous anodic aluminum oxide films encapsulated with silver nanoparticle arrays.

    PubMed

    Huang, Chen-Han; Lin, Hsing-Ying; Lau, Ben-Chao; Liu, Chih-Yi; Chui, Hsiang-Chen; Tzeng, Yonhua

    2010-12-20

    We report on plasmon induced optical switching of electrical conductivity in two-dimensional (2D) arrays of silver (Ag) nanoparticles encapsulated inside nanochannels of porous anodic aluminum oxide (AAO) films. The reversible switching of photoconductivity greatly enhanced by an array of closely spaced Ag nanoparticles which are isolated from each other and from the ambient by thin aluminum oxide barrier layers are attributed to the improved electron transport due to the localized surface plasmon resonance and coupling among Ag nanoparticles. The photoconductivity is proportional to the power, and strongly dependent on the wavelength of light illumination. With Ag nanoparticles being isolated from the ambient environments by a thin layer of aluminum oxide barrier layer of controlled thickness in nanometers to tens of nanometers, deterioration of silver nanoparticles caused by environments is minimized. The electrochemically fabricated nanostructured Ag/AAO is inexpensive and promising for applications to integrated plasmonic circuits and sensors.

  3. Perovskite nanoparticle-sensitized Ga 2O 3 nanorod arrays for CO detection at high temperature

    DOE PAGES

    Lin, Hui -Jan; Baltrus, John P.; Gao, Haiyong; ...

    2016-04-04

    Here, noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La 0.8Sr 0.2FeO 3 (LSFO) nanoparticle surface decoration on Ga 2O 3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts wasmore » of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga 2O 3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga 2O 3 nanorod surfaces with faster surface CO oxidation reactions.« less

  4. Perovskite Nanoparticle-Sensitized Ga2O3 Nanorod Arrays for CO Detection at High Temperature.

    PubMed

    Lin, Hui-Jan; Baltrus, John P; Gao, Haiyong; Ding, Yong; Nam, Chang-Yong; Ohodnicki, Paul; Gao, Pu-Xian

    2016-04-13

    Noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La(0.8)Sr(0.2)FeO3 (LSFO) nanoparticle surface decoration on Ga2O3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts was of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga2O3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga2O3 nanorod surfaces with faster surface CO oxidation reactions.

  5. A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

    PubMed

    Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

    2018-04-03

    In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

  6. Negative differential photoconductance in gold nanoparticle arrays in the Coulomb blockade regime.

    PubMed

    Mangold, Markus A; Calame, Michel; Mayor, Marcel; Holleitner, Alexander W

    2012-05-22

    We investigate the photoconductance of gold nanoparticle arrays in the Coulomb blockade regime. Two-dimensional, hexagonal crystals of nanoparticles are produced by self-assembly. The nanoparticles are weakly coupled to their neighbors by a tunneling conductance. At low temperatures, the single electron charging energy of the nanoparticles dominates the conductance properties of the array. The Coulomb blockade of the nanoparticles can be lifted by optical excitation with a laser beam. The optical excitation leads to a localized heating of the arrays, which in turn gives rise to a local change in conductance and a redistribution of the overall electrical potential in the arrays. We introduce a dual-beam optical excitation technique to probe the distribution of the electrical potential in the nanoparticle array. A negative differential photoconductance is the direct consequence of the redistribution of the electrical potential upon lifting of the Coulomb blockade. On the basis of our model, we calculate the optically induced current from the dark current-voltage characteristics of the nanoparticle array. The calculations closely reproduce the experimental observations.

  7. Predicting plasmonic coupling with Mie-Gans theory in silver nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Ranjan, M.

    2013-09-01

    Plasmonic coupling is observed in the self-aligned arrays of silver nanoparticles grown on ripple-patterned substrate. Large differences observed in the plasmon resonance wavelength, measured and calculated using Mie-Gans theory, predict that strong plasmonic coupling exists in the nanoparticles arrays. Even though plasmonic coupling exists both along and across the arrays, but it is found to be much stronger along the arrays due to shorter interparticle gap and particle elongation. This effect is responsible for observed optical anisotropy in such arrays. Measured red-shift even in the transverse plasmon resonance mode with the increasing nanoparticles aspect ratio in the arrays, deviate from the prediction of Mie-Gans theory. This essentially means that plasmonic coupling is dominating over the shape anisotropy. Plasmon resonance tuning is presented by varying the plasmonic coupling systematically with nanoparticles aspect ratio and ripple wavelength. Plasmon resonance red-shifts with the increasing aspect ratio along the ripple, and blue-shifts with the increasing ripple wavelength across the ripple. Therefore, reported bottom-up approach for fabricating large area-coupled nanoparticle arrays can be used for various field enhancement-based plasmonic applications.

  8. Coating graphene paper with 2D-assembly of electrocatalytic nanoparticles: a modular approach toward high-performance flexible electrodes.

    PubMed

    Xiao, Fei; Song, Jibin; Gao, Hongcai; Zan, Xiaoli; Xu, Rong; Duan, Hongwei

    2012-01-24

    The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact energy devices. We report a modular approach to fabricating high-performance flexible electrodes by structurally integrating 2D-assemblies of nanoparticles with freestanding graphene paper. We have shown that the 2D array of gold nanoparticles at oil-water interfaces can be transferred on freestanding graphene oxide paper, leading to a monolayer of densely packed gold nanoparticles of uniform sizes loaded on graphene oxide paper. One major finding is that the postassembly electrochemical reduction of graphene oxide paper restores the ordered structure and electron-transport properties of graphene, and gives rise to robust and biocompatible freestanding electrodes with outstanding electrocatalytic activities, which have been manifested by the sensitive and selective detection of two model analytes: glucose and hydrogen peroxide (H(2)O(2)) secreted by live cells. The modular nature of this approach coupled with recent progress in nanocrystal synthesis and surface engineering opens new possibilities to systematically study the dependence of catalytic performance on the structural parameters and chemical compositions of the nanocrystals. © 2011 American Chemical Society

  9. Enhanced interfacial contact between PbS and TiO2 layers in quantum dot solar cells using 2D-arrayed TiO2 hemisphere nanostructures

    NASA Astrophysics Data System (ADS)

    Lee, Wonseok; Ryu, Ilhwan; Lee, Haein; Yim, Sanggyu

    2018-02-01

    Two-dimensionally (2D) arrayed hemispherical nanostructures of TiO2 thin films were successfully fabricated using a simple procedure of spin-coating or dip-coating TiO2 nanoparticles onto 2D close-packed polystyrene (PS) nanospheres, followed by PS extraction. The nanostructured TiO2 film was then used as an n-type layer in a lead sulfide (PbS) colloidal quantum dot solar cell. The TiO2 nanostructure could provide significantly increased contacts with subsequently deposited PbS quantum dot layer. In addition, the periodically arrayed nanostructure could enhance optical absorption of the cell by redirecting the path of the incident light and increasing the path length passing though the active layer. As a result, the power conversion efficiency (PCE) reached 5.13%, which is approximately a 1.7-fold increase over that of the control cell without nanostructuring, 3.02%. This PCE enhancement can mainly be attributed to the increase of the short-circuit current density from 19.6 mA/cm2 to 30.6 mA/cm2, whereas the open-circuit voltage and fill factor values did not vary significantly.

  10. Inspection design using 2D phased array, TFM and cueMAP software

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McGilp, Ailidh; Dziewierz, Jerzy; Lardner, Tim

    2014-02-18

    A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imagingmore » performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.« less

  11. Time-dependent optical response of three-dimensional Au nanoparticle arrays formed on silica nanowires

    NASA Astrophysics Data System (ADS)

    Di Mario, Lorenzo; Otomalo, Tadele Orbula; Catone, Daniele; O'Keeffe, Patrick; Tian, Lin; Turchini, Stefano; Palpant, Bruno; Martelli, Faustino

    2018-03-01

    We present stationary and transient absorption measurements on 3D Au nanoparticle (NP)-decorated Si O2 nanowire arrays. The 3D NP array has been produced by the dewetting of a thin Au film deposited on silica nanowires produced by oxidation of silicon nanowires. The experimental behaviors of the spectral and temporal dynamics observed in the experiment are accurately described by a two-step, three-temperature model. Using an arbitrary set of Au NPs with different aspect ratios, we demonstrate that the width of the experimental spectra, the energy shift of their position with time, and the asymmetry between the two positive wings in the dynamical variation of absorption can all be attributed to the nonuniform shape distribution of the Au NPs in the sample.

  12. 1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

    PubMed

    Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

    2017-12-13

    Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

  13. Optical invisibility through metasurfaces made of plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Monti, A.; Alù, A.; Toscano, A.; Bilotti, F.

    2015-03-01

    In this paper, we investigate the application of the mantle cloaking technique to near-infrared and visible frequencies, analyzing and designing thin covers consisting of 2D arrays of plasmonic nanoparticles. First, we validate and generalize an analytical model recently appeared in the literature to describe a 2D array of plasmonic nanoparticles as a metasurface characterized by its homogenized surface reactance. We prove that the proposed model allows to efficiently design 2D mantle cloaks with an assigned surface reactance, enabling, thus, the extension of the mantle cloaking technique to optical frequencies. Then, we design realistic optical mantle cloaks made of 2D arrays of spheroidal plasmonic nanoparticles with a high eccentricity. We show that the proposed cloaks allow significant, moderately broadband cloaking effects at visible frequencies. In our designs, we consider realistic losses and non-critical nanoparticle dimensions to envision a practical realization of the proposed cloaks.

  14. Anomalous complete opaqueness in a sparse array of gold nanoparticle chains

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bai Benfeng; Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084; Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu

    2011-08-22

    We report on an anomalous polarization-switching extinction effect in a sparse array of gold nanoparticle chains: under normal incidence of light, the array is almost transparent for one polarization; whereas it is fully opaque (with nearly zero transmittance) for the orthogonal polarization within a narrow band, even though the nanoparticles cover only a tiny fraction (say, 3.5%) of the transparent substrate surface. We reveal that the strong polarization-dependent short-range dipolar coupling and long-range radiative coupling of gold nanoparticles in this highly asymmetric array is responsible for this extraordinary effect.

  15. Tailor-made Au@Ag core-shell nanoparticle 2D arrays on protein-coated graphene oxide with assembly enhanced antibacterial activity

    NASA Astrophysics Data System (ADS)

    Wang, Huiqiao; Liu, Jinbin; Wu, Xuan; Tong, Zhonghua; Deng, Zhaoxiang

    2013-05-01

    Water-dispersible two-dimensional (2D) assemblies of Au@Ag core-shell nanoparticles are obtained through a highly selective electroless silver deposition on pre-assembled gold nanoparticles on bovine serum albumin (BSA)-coated graphene oxide (BSA-GO). While neither BSA-GO nor AuNP-decorated BSA-GO shows any antibacterial ability, the silver-coated GO@Au nanosheets (namely GO@Au@Ag) exhibit an enhanced antibacterial activity against Gram-negative Escherichia coli (E. coli) bacteria, superior to unassembled Au@Ag nanoparticles and even ionic Ag. Such an improvement may be attributed to the increased local concentration of silver nanoparticles around a bacterium and a polyvalent interaction with the bacterial surface. In addition, the colloidal stability of this novel nano-antimicrobial against the formation of random nanoparticle aggregates guarantees a minimized activity loss of the Au@Ag nanoparticles. The antibacterial efficacy of GO@Au@Ag is less sensitive to the existence of Cl-, in comparison with silver ions, providing another advantage for wound dressing applications. Our research unambiguously reveals a strong and very specific interaction between the GO@Au@Ag nanoassembly and E. coli, which could be an important clue toward a rational design, synthesis and assembly of innovative and highly active antibacterial nanomaterials.

  16. Molecular dynamics study of the growth of a metal nanoparticle array by solid dewetting

    NASA Astrophysics Data System (ADS)

    Luan, Yanhua; Li, Yanru; Nie, Tiaoping; Yu, Jun; Meng, Lijun

    2018-03-01

    We investigated the effect of the substrate and the ambient temperature on the growth of a metal nanoparticle array (nanoarray) on a solid-patterned substrate by dewetting a Au liquid film using an atomic simulation technique. The patterned substrate was constructed by introducing different interaction potentials for two atom groups ( C 1 and C 2) in the graphene-like substrate. The C 1 group had a stronger interaction between the Au film and the substrate and was composed of regularly distributed circular disks with radius R and distance D between the centers of neighboring disks. Our simulation results demonstrate that R and D have a strikingly different influence on the growth of the nanoparticle arrays. The degree of order of the nanoarray increases first before it reaches a peak and then decreases for increasing R at fixed D. However, the degree of order increases monotonously when D is increased and reaches a saturated value beyond a critical value of D for a fixed R. Interestingly, a labyrinth-like structure appeared during the dewetting process of the metal film. The simulation results also indicated that the temperature was an important factor in controlling the properties of the nanoarray. An appropriate temperature leads to an optimized nanoarray with a uniform grain size and well-ordered particle distribution. These results are important for understanding the dewetting behaviors of metal films on solid substrates and understanding the growth of highly ordered metal nanoarrays using a solid-patterned substrate method.

  17. A Conductometric Indium Oxide Semiconducting Nanoparticle Enzymatic Biosensor Array

    PubMed Central

    Lee, Dongjin; Ondrake, Janet; Cui, Tianhong

    2011-01-01

    We report a conductometric nanoparticle biosensor array to address the significant variation of electrical property in nanomaterial biosensors due to the random network nature of nanoparticle thin-film. Indium oxide and silica nanoparticles (SNP) are assembled selectively on the multi-site channel area of the resistors using layer-by-layer self-assembly. To demonstrate enzymatic biosensing capability, glucose oxidase is immobilized on the SNP layer for glucose detection. The packaged sensor chip onto a ceramic pin grid array is tested using syringe pump driven feed and multi-channel I–V measurement system. It is successfully demonstrated that glucose is detected in many different sensing sites within a chip, leading to concentration dependent currents. The sensitivity has been found to be dependent on the channel length of the resistor, 4–12 nA/mM for channel lengths of 5–20 μm, while the apparent Michaelis-Menten constant is 20 mM. By using sensor array, analytical data could be obtained with a single step of sample solution feeding. This work sheds light on the applicability of the developed nanoparticle microsensor array to multi-analyte sensors, novel bioassay platforms, and sensing components in a lab-on-a-chip. PMID:22163696

  18. Degradation of 2,4-D in soils by Fe₃O₄ nanoparticles combined with stimulating indigenous microbes.

    PubMed

    Fang, Guodong; Si, Youbin; Tian, Chao; Zhang, Gangya; Zhou, Dongmei

    2012-03-01

    Degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in soils by Fe₃O₄ nanoparticles combined with soil indigenous microbes was investigated, and the effects of Fe₃O₄ nanoparticles on soil microbial populations and enzyme activities were also studied. The soils contaminated with 2,4-D were treated with Fe₃O₄ nanoparticles. The microbial populations and enzyme activities were analyzed by dilution plate method and chemical assay, respectively, and the concentration of 2,4-D in soil was determined by high-performance liquid chromatography (HPLC). The results indicated that Fe₃O₄ nanoparticles combined with soil indigenous microbes led to a higher degradation efficiency of 2,4-D than the treatments with Fe₃O₄ nanoparticles or indigenous microbes alone. The degradation of 2,4-D in soils followed the pseudo first-order kinetic. The half-lives of 2,4-D degradation (DT₅₀) of the combined treatments were 0.9, 1.9 and 3.1 days in a Red soil, Vertisol and Alfisol, respectively, which implied that the DT₅₀ of the combination treatments were significantly shorter than that of the treatments Fe₃O₄ nanoparticles or indigenous microbes alone. The effects of Fe₃O₄ nanoparticles on soil microbial populations and enzyme activities were also investigated and compared with the α-Fe₂O₃ nanoparticles. The results suggested that the α-Fe₂O₃ nanoparticles had only comparatively small effects on degradation of 2,4-D in soils, while the Fe₃O₄ nanoparticles not only degraded 2,4-D in soils but also increased the soil microbial populations and enzyme activities; the maximum increase in enzyme activities were 67.8% (amylase), 53.8% (acid phosphatase), 26.5% (catalase) and 38.0% (urease), compared with the untreated soil. Moreover, the introduction of Fe₃O₄ nanoparticles at the different dosage resulted in a variable degradation efficiency of 2,4-D in soil. The method of combining Fe₃O₄ nanoparticles with indigenous soil microbes may

  19. Design of a front-end integrated circuit for 3D acoustic imaging using 2D CMUT arrays.

    PubMed

    Ciçek, Ihsan; Bozkurt, Ayhan; Karaman, Mustafa

    2005-12-01

    Integration of front-end electronics with 2D capacitive micromachined ultrasonic transducer (CMUT) arrays has been a challenging issue due to the small element size and large channel count. We present design and verification of a front-end drive-readout integrated circuit for 3D ultrasonic imaging using 2D CMUT arrays. The circuit cell dedicated to a single CMUT array element consists of a high-voltage pulser and a low-noise readout amplifier. To analyze the circuit cell together with the CMUT element, we developed an electrical CMUT model with parameters derived through finite element analysis, and performed both the pre- and postlayout verification. An experimental chip consisting of 4 X 4 array of the designed circuit cells, each cell occupying a 200 X 200 microm2 area, was formed for the initial test studies and scheduled for fabrication in 0.8 microm, 50 V CMOS technology. The designed circuit is suitable for integration with CMUT arrays through flip-chip bonding and the CMUT-on-CMOS process.

  20. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    PubMed

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-08

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

  1. Fast Noncircular 2D-DOA Estimation for Rectangular Planar Array

    PubMed Central

    Xu, Lingyun; Wen, Fangqing

    2017-01-01

    A novel scheme is proposed for direction finding with uniform rectangular planar array. First, the characteristics of noncircular signals and Euler’s formula are exploited to construct a new real-valued rectangular array data. Then, the rotational invariance relations for real-valued signal space are depicted in a new way. Finally the real-valued propagator method is utilized to estimate the pairing two-dimensional direction of arrival (2D-DOA). The proposed algorithm provides better angle estimation performance and can discern more sources than the 2D propagator method. At the same time, it has very close angle estimation performance to the noncircular propagator method (NC-PM) with reduced computational complexity. PMID:28417926

  2. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.

    2015-05-18

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation timesmore » (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.« less

  3. Characterization of nonlinear ultrasound fields of 2D therapeutic arrays

    PubMed Central

    Yuldashev, Petr V.; Kreider, Wayne; Sapozhnikov, Oleg A.; Farr, Navid; Partanen, Ari; Bailey, Michael R.; Khokhlova, Vera

    2015-01-01

    A current trend in high intensity focused ultrasound (HIFU) technologies is to use 2D focused phased arrays that enable electronic steering of the focus, beamforming to avoid overheating of obstacles (such as ribs), and better focusing through inhomogeneities of soft tissue using time reversal methods. In many HIFU applications, the acoustic intensity in situ can reach thousands of W/cm2 leading to nonlinear propagation effects. At high power outputs, shock fronts develop in the focal region and significantly alter the bioeffects induced. Clinical applications of HIFU are relatively new and challenges remain for ensuring their safety and efficacy. A key component of these challenges is the lack of standard procedures for characterizing nonlinear HIFU fields under operating conditions. Methods that combine low-amplitude pressure measurements and nonlinear modeling of the pressure field have been proposed for axially symmetric single element transducers but have not yet been validated for the much more complex 3D fields generated by therapeutic arrays. Here, the method was tested for a clinical HIFU source comprising a 256-element transducer array. A numerical algorithm based on the Westervelt equation was used to enable 3D full-diffraction nonlinear modeling. With the acoustic holography method, the magnitude and phase of the acoustic field were measured at a low power output and used to determine the pattern of vibrations at the surface of the array. This pattern was then scaled to simulate a range of intensity levels near the elements up to 10 W/cm2. The accuracy of modeling was validated by comparison with direct measurements of the focal waveforms using a fiber-optic hydrophone. Simulation results and measurements show that shock fronts with amplitudes up to 100 MPa were present in focal waveforms at clinically relevant outputs, indicating the importance of strong nonlinear effects in ultrasound fields generated by HIFU arrays. PMID:26203345

  4. An integrated circuit with transmit beamforming flip-chip bonded to a 2-D CMUT array for 3-D ultrasound imaging.

    PubMed

    Wygant, Ira O; Jamal, Nafis S; Lee, Hyunjoo J; Nikoozadeh, Amin; Oralkan, Omer; Karaman, Mustafa; Khuri-Yakub, Butrus T

    2009-10-01

    State-of-the-art 3-D medical ultrasound imaging requires transmitting and receiving ultrasound using a 2-D array of ultrasound transducers with hundreds or thousands of elements. A tight combination of the transducer array with integrated circuitry eliminates bulky cables connecting the elements of the transducer array to a separate system of electronics. Furthermore, preamplifiers located close to the array can lead to improved receive sensitivity. A combined IC and transducer array can lead to a portable, high-performance, and inexpensive 3-D ultrasound imaging system. This paper presents an IC flip-chip bonded to a 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array for 3-D ultrasound imaging. The IC includes a transmit beamformer that generates 25-V unipolar pulses with programmable focusing delays to 224 of the 256 transducer elements. One-shot circuits allow adjustment of the pulse widths for different ultrasound transducer center frequencies. For receiving reflected ultrasound signals, the IC uses the 32-elements along the array diagonals. The IC provides each receiving element with a low-noise 25-MHz-bandwidth transimpedance amplifier. Using a field-programmable gate array (FPGA) clocked at 100 MHz to operate the IC, the IC generated properly timed transmit pulses with 5-ns accuracy. With the IC flip-chip bonded to a CMUT array, we show that the IC can produce steered and focused ultrasound beams. We present 2-D and 3-D images of a wire phantom and 2-D orthogonal cross-sectional images (Bscans) of a latex heart phantom.

  5. Self-assembled nanoparticle arrays as nanomasks for pattern transfer

    NASA Astrophysics Data System (ADS)

    Sachan, M.; Bonnoit, C.; Hogg, C.; Evarts, E.; Bain, J. A.; Majetich, S. A.; Park, J.-H.; Zhu, J.-G.

    2008-07-01

    Argon ion milling was used to transfer the pattern of sparse 12 nm iron oxide nanoparticles into underlying thin films of Pt and magnetic tunnel junction stacks and quantify their etching rates and morphological evolution. Under typical milling conditions, Pt milled at 10 nm min-1, while the isolated particles of iron oxide used for the mask milled at 5 nm min-1. Dilute dispersions of nanoparticles were used to produce the sparse nanomasks, and high resolution scanning electron microscopy (SEM) and atomic force microscopy were used to monitor the evolution of etched structures as a function of milling time. SEM measurements indicate an apparent 20% increase in feature diameter before the features began to diminish under additional milling, suggesting redeposition as a limiting feature in the milling of dense arrays. Simulations of the milling process in nanoparticle arrays that include redeposition are consistent with this observation. These simulations predict that an edge-to-edge spacing of 3 nm in a dense array is feasible, but that redeposition reduces the final structure aspect ratio from that of the masking array by as much as a factor of two.

  6. Physical vapor deposition of one-dimensional nanoparticle arrays on graphite: seeding the electrodeposition of gold nanowires.

    PubMed

    Cross, C E; Hemminger, J C; Penner, R M

    2007-09-25

    One-dimensional (1D) ensembles of 2-15 nm diameter gold nanoparticles were prepared using physical vapor deposition (PVD) on highly oriented pyrolytic graphite (HOPG) basal plane surfaces. These 1D Au nanoparticle ensembles (NPEs) were prepared by depositing gold (0.2-0.6 nm/s) at an equivalent thickness of 3-4 nm onto HOPG surfaces at 670-690 K. Under these conditions, vapor-deposited gold nucleated selectively at the linear step edge defects present on these HOPG surfaces with virtually no nucleation of gold particles on terraces. The number density of 2-15 nm diameter gold particles at step edges was 30-40 microm-1. These 1D NPEs were up to a millimeter in length and organized into parallel arrays on the HOPG surface, following the organization of step edges. Surprisingly, the deposition of more gold by PVD did not lead to the formation of continuous gold nanowires at step edges under the range of sample temperature or deposition flux we have investigated. Instead, these 1D Au NPEs were used as nucleation templates for the preparation by electrodeposition of gold nanowires. The electrodeposition of gold occurred selectively on PVD gold nanoparticles over the potential range from 700-640 mV vs SCE, and after optimization of the electrodeposition parameters continuous gold nanowires as small as 80-90 nm in diameter and several micrometers in length were obtained.

  7. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  8. (Bio)Sensing Using Nanoparticle Arrays: On the Effect of Analyte Transport on Sensitivity.

    PubMed

    Lynn, N Scott; Homola, Jiří

    2016-12-20

    There has recently been an extensive amount of work regarding the development of optical, electrical, and mechanical (bio)sensors employing planar arrays of surface-bound nanoparticles. The sensor output for these systems is dependent on the rate at which analyte is transported to, and interacts with, each nanoparticle in the array. There has so far been little discussion on the relationship between the design parameters of an array and the interplay of convection, diffusion, and reaction. Moreover, current methods providing such information require extensive computational simulation. Here we demonstrate that the rate of analyte transport to a nanoparticle array can be quantified analytically. We show that such rates are bound by both the rate to a single NP and that to a planar surface (having equivalent size as the array), with the specific rate determined by the fill fraction: the ratio between the total surface area used for biomolecular capture with respect to the entire sensing area. We characterize analyte transport to arrays with respect to changes in numerous parameters relevant to experiment, including variation of the nanoparticle shape and size, packing density, flow conditions, and analyte diffusivity. We also explore how analyte capture is dependent on the kinetic parameters related to an affinity-based biosensor, and furthermore, we classify the conditions under which the array might be diffusion- or reaction-limited. The results obtained herein are applicable toward the design and optimization of all (bio)sensors based on nanoparticle arrays.

  9. A 1-MHz 2-D CMUT array for HIFU thermal ablation

    NASA Astrophysics Data System (ADS)

    Yoon, Hyo-Seon; Vaithilingam, Srikant; Park, Kwan Kyu; Nikoozadeh, Amin; Firouzi, Kamyar; Choe, Jung Woo; Watkins, Ronald D.; Oguz, Huseyin Kagan; Kupnik, Mario; Pauly, Kim Butts; Khuri-Yakub, Pierre

    2017-03-01

    We developed a fully-populated 2-D capacitive micromachined ultrasonic transducer (CMUT) array for high intensity focused ultrasound (HIFU) treatment. The 2-D CMUT array, which consists of 20 × 20 square CMUT elements with an element-to-element pitch of 1 mm, was designed and fabricated using the thick-buried-oxide (BOX) fabrication process. It was then assembled on a custom interface board that can provide various array configurations depending on the desired applications. In this study, the interface board groups the CMUT array elements into eight channels, based on the phase delay from the element to the targeted focal point at a 20-mm distance from the array surface, which corresponds to an F-number of 1. An 8-channel phase generating system supplies continuous waves with eight different phases to the eight channels of the CMUT array through bias-tees and amplifiers. This array aperture, grouped into eight channels, gives a focusing gain of 6.09 according to field simulation using Field II. Assuming a peak-to-peak pressure of 1 MPa at the surface of the array, our custom temperature simulator predicts successful tissue ablation at the focus. During the measurements, each channel was tuned with a series inductor for an operational frequency of 1 MHz. With a CMUT DC bias of 100 V and a 1-MHz AC input voltage of 55 V, we achieved peak-to-peak output pressures of 173.9 kPa and 568.7 kPa at the array surface and at the focus, respectively. The focusing gain calculated from this measurement is 3.27, which is lower than the simulated gain of 6.09 because of the mutual radiation impedance among the CMUT cells. Further optimization of the operating condition of this array and design improvements for reducing the effect of mutual radiation impedance are currently on-going.

  10. Measuring the electromagnetic chirality of 2D arrays under normal illumination.

    PubMed

    Garcia-Santiago, X; Burger, S; Rockstuhl, C; Fernandez-Corbaton, I

    2017-10-15

    We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, which further allows a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.

  11. A 2D/3D hybrid integral imaging display by using fast switchable hexagonal liquid crystal lens array

    NASA Astrophysics Data System (ADS)

    Lee, Hsin-Hsueh; Huang, Ping-Ju; Wu, Jui-Yi; Hsieh, Po-Yuan; Huang, Yi-Pai

    2017-05-01

    The paper proposes a new display which could switch 2D and 3D images on a monitor, and we call it as Hybrid Display. In 3D display technologies, the reduction of image resolution is still an important issue. The more angle information offer to the observer, the less spatial resolution would offer to image resolution because of the fixed panel resolution. Take it for example, in the integral photography system, the part of image without depth, like background, will reduce its resolution by transform from 2D to 3D image. Therefore, we proposed a method by using liquid crystal component to quickly switch the 2D image and 3D image. Meanwhile, the 2D image is set as a background to compensate the resolution.. In the experiment, hexagonal liquid crystal lens array would be used to take the place of fixed lens array. Moreover, in order to increase lens power of the hexagonal LC lens array, we applied high resistance (Hi-R) layer structure on the electrode. Hi-R layer would make the gradient electric field and affect the lens profile. Also, we use panel with 801 PPI to display the integral image in our system. Hence, the consequence of full resolution 2D background with the 3D depth object forms the Hybrid Display.

  12. Inclusion of Cu nano-cluster 1D arrays inside a C3-symmetric artificial oligopeptide via co-assembly

    NASA Astrophysics Data System (ADS)

    Gong, Ruiying; Li, Fei; Yang, Chunpeng; Wan, Xiaobo

    2015-12-01

    A peptide sequence N3-GVGV-OMe (G: glycine; V: valine) was attached to a benzene 1,3,5-tricarboxamide (BTA) derivative via ``click chemistry'' to afford a C3-symmetric artificial oligopeptide. The key feature of this oligopeptide is that the binding sites (triazole groups formed by click reaction) are located at the center, while the three oligopeptide arms with a strong tendency to assemble are located around it, which provides inner space to accommodate nanoparticles via self-assembly. The inclusion of Cu nanoclusters and the formation of one-dimensional (1D) arrays inside the nanofibers of the C3-symmetric artificial oligopeptide assembly were observed, which is quite different from the commonly observed nanoparticle growth on the surface of the pre-assembled oligopeptide nanofibers via the coordination sites located outside. Our finding provides an instructive concept for the design of other stable organic-inorganic hybrid 1D arrays with the inorganic nanoparticles inside.A peptide sequence N3-GVGV-OMe (G: glycine; V: valine) was attached to a benzene 1,3,5-tricarboxamide (BTA) derivative via ``click chemistry'' to afford a C3-symmetric artificial oligopeptide. The key feature of this oligopeptide is that the binding sites (triazole groups formed by click reaction) are located at the center, while the three oligopeptide arms with a strong tendency to assemble are located around it, which provides inner space to accommodate nanoparticles via self-assembly. The inclusion of Cu nanoclusters and the formation of one-dimensional (1D) arrays inside the nanofibers of the C3-symmetric artificial oligopeptide assembly were observed, which is quite different from the commonly observed nanoparticle growth on the surface of the pre-assembled oligopeptide nanofibers via the coordination sites located outside. Our finding provides an instructive concept for the design of other stable organic-inorganic hybrid 1D arrays with the inorganic nanoparticles inside. Electronic

  13. Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

    2017-03-01

    A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

  14. Characterization and electrochemical response of DNA functionalized 2nm gold nanoparticles confined in a nanochannel array.

    PubMed

    Peinetti, Ana S; Ceretti, Helena; Mizrahi, Martín; González, Graciela A; Ramírez, Silvana A; Requejo, Félix G; Montserrat, Javier M; Battaglini, Fernando

    2018-06-01

    Polyvalent gold nanoparticle oligonucleotide conjugates are subject of intense research. Even though 2nm diameter AuNPs have been previously modified with DNA, little is known about their structure and electrochemical behavior. In this work, we examine the influence of different surface modification strategies on the interplay between the meso-organization and the molecular recognition properties of a 27-mer DNA strand. This DNA strand is functionalized with different sulfur-containing moieties and immobilized on 2nm gold nanoparticles confined on a nanoporous alumina, working the whole system as an electrode array. Surface coverages were determined by EXAFS and the performance as recognition elements for impedance-based sensors is evaluated. Our results prove that low DNA coverages on the confined nanoparticles prompt to a more sensitive response, showing the relevance in avoiding the DNA strand overcrowding. The system was able to determine a concentration as low as 100pM of the complementary strand, thus introducing the foundations for the construction of label-free genosensors at the nanometer scale. Copyright © 2018 Elsevier B.V. All rights reserved.

  15. ON THE FREEZING AND IDENTIFICATION OF LIPID MONOLAYER 2-D ARRAYS FOR CRYOELECTRON MICROSCOPY

    PubMed Central

    Taylor, Dianne W.; Kelly, Deborah F.; Cheng, Anchi; Taylor, Kenneth A.

    2008-01-01

    Lipid monolayers provide a convenient vehicle for the crystallization of biological macromolecules for 3-D electron microscopy. Although numerous examples of 3-D images from 2-D protein arrays have been described from negatively stained specimens, only six structures have been done from frozen hydrated specimens. We describe here a method that makes high quality frozen-hydrated specimens of lipid monolayer arrays for cryoelectron microscopy. The method uses holey carbon films with patterned holes for monolayer recovery, blotting and plunge freezing to produce thin aqueous films which cover >90% of the available grid area. With this method, even specimens with relatively infrequent crystals can be screened using automated data collection techniques. Though developed for microscopic examination of 2-D arrays, the method may have wider application to the preparation of single particle specimens for 3-D image reconstruction. PMID:17561414

  16. Simulated near-field mapping of ripple pattern supported metal nanoparticles arrays for SERS optimization

    NASA Astrophysics Data System (ADS)

    Arya, Mahima; Bhatnagar, Mukul; Ranjan, Mukesh; Mukherjee, Subroto; Nath, Rabinder; Mitra, Anirban

    2017-11-01

    An analytical model has been developed using a modified Yamaguchi model along with the wavelength dependent plasmon line-width correction. The model has been used to calculate the near-field response of random nanoparticles on the plane surface, elongated and spherical silver nanoparticle arrays supported on ion beam produced ripple patterned templates. The calculated near-field mapping for elongated nanoparticles arrays on the ripple patterned surface shows maximum number of hot-spots with a higher near-field enhancement (NFE) as compared to the spherical nanoparticle arrays and randomly distributed nanoparticles on the plane surface. The results from the simulations show a similar trend for the NFE when compared to the far field reflection spectra. The nature of the wavelength dependent NFE is also found to be in agreement with the observed experimental results from surface enhanced Raman spectroscopy (SERS). The calculated and the measured optical response unambiguously reveal the importance of interparticle gap and ordering, where a high intensity Raman signal is obtained for ordered elongated nanoparticles arrays case as against non-ordered and the aligned configuration of spherical nanoparticles on the rippled surface.

  17. Self-leveling 2D DPN probe arrays

    NASA Astrophysics Data System (ADS)

    Haaheim, Jason R.; Val, Vadim; Solheim, Ed; Bussan, John; Fragala, J.; Nelson, Mike

    2010-02-01

    Dip Pen Nanolithography® (DPN®) is a direct write scanning probe-based technique which operates under ambient conditions, making it suitable to deposit a wide range of biological and inorganic materials. Precision nanoscale deposition is a fundamental requirement to advance nanoscale technology in commercial applications, and tailoring chemical composition and surface structure on the sub-100 nm scale benefits researchers in areas ranging from cell adhesion to cell-signaling and biomimetic membranes. These capabilities naturally suggest a "Desktop Nanofab" concept - a turnkey system that allows a non-expert user to rapidly create high resolution, scalable nanostructures drawing upon well-characterized ink and substrate pairings. In turn, this system is fundamentally supported by a portfolio of MEMS devices tailored for microfluidic ink delivery, directed placement of nanoscale materials, and cm2 tip arrays for high-throughput nanofabrication. Massively parallel two-dimensional nanopatterning is now commercially available via NanoInk's 2D nano PrintArray™, making DPN a high-throughput (>3×107 μm2 per hour), flexible and versatile method for precision nanoscale pattern formation. However, cm2 arrays of nanoscopic tips introduce the nontrivial problem of getting them all evenly touching the surface to ensure homogeneous deposition; this requires extremely precise leveling of the array. Herein, we describe how we have made the process simple by way of a selfleveling gimbal attachment, coupled with semi-automated software leveling routines which bring the cm^2 chip to within 0.002 degrees of co-planarity. This excellent co-planarity yields highly homogeneous features across a square centimeter, with <6% feature size standard deviation. We have engineered the devices to be easy to use, wire-free, and fully integrated with both of our patterning tools: the DPN 5000, and the NLP 2000.

  18. Strong light extraction enhancement using TiO2 nanoparticles-based microcone arrays embossed on III-Nitride light emitting diodes

    NASA Astrophysics Data System (ADS)

    Désières, Yohan; Chen, Ding Yuan; Visser, Dennis; Schippers, Casper; Anand, Srinivasan

    2018-06-01

    Colloidal TiO2 nanoparticles were used for embossing of composite microcone arrays on III-Nitride vertical-thin-film blue light emitting diodes (LEDs) as well as on silicon, glass, gallium arsenide, and gallium nitride surfaces. Ray tracing simulations were performed to optimize the design of microcones for light extraction and to explain the experimental results. An optical power enhancement of ˜2.08 was measured on III-Nitride blue LEDs embossed with a hexagonal array of TiO2 microcones of ˜1.35 μm in height and ˜2.6 μm in base width, without epoxy encapsulation. A voltage increase in ˜70 mV at an operating current density of ˜35 A/cm2 was measured for the embossed LEDs. The TiO2 microcone arrays were embossed on functioning LEDs, using low pressures (˜100 g/cm2) and temperatures ≤100 °C.

  19. Formation of 2D and 3D superlattices of silver nanoparticles inside an emulsion droplet

    NASA Astrophysics Data System (ADS)

    Hussain Shaik, Aabid; Srinivasa Reddy, D.

    2017-03-01

    This work is aimed at the formation of 2D and 3D superlattices (SL) of silver nanoparticles inside an emulsion droplet. The monodisperse nanoparticles required for SL formation were prepared by a digestive ripening technique. Digestive ripening is a post processing technique where polydisperse colloids are refluxed with excess surface-active ligands to prepare a monodisperse colloid. More uniform silver nanoparticles (~3.6  ±  0.5 nm) were formed by slow evaporation of organosols on a carbon-coated copper grid. The best 3D silver superlattices have been formed using an oil in water (o/w) emulsion method by aging the monodisperse particles in a confined environment like o/w emulsion at different temperatures ranging from 5 °C-4 °C. The kinetics of the formation of superlattices inside an emulsion droplet were investigated by controlling various parameters. The kinetics were found to be dependent on the emulsion aging period (30 d) and storage temperature of the emulsion (-4 °C).

  20. Polarization-driven self-organization of silver nanoparticles in 1D and 2D subwavelength gratings for plasmonic photocatalysis.

    PubMed

    Baraldi, G; Bakhti, S; Liu, Z; Reynaud, S; Lefkir, Y; Vocanson, F; Destouches, N

    2017-01-20

    One of the main challenges in plasmonics is to conceive large-scale, low-cost techniques suitable for the fabrication of metal nanoparticle patterns showing precise spatial organization. Here, we introduce a simple method based on continuous-wave laser illumination to induce the self-organization of silver nanoparticles within high-index thin films. We show that highly regular and homogeneous nanoparticle gratings can be produced on large areas using laser-controlled self-organization processes. This very versatile technique can provide 1D and 2D patterns at a subwavelength scale with tunable features. It does not need any stabilization or expensive devices, such as those required by optical or electron lithography, and is rapid to implement. Accurate in-plane and in-depth characterizations provide valuable information to explain the mechanisms that lead to pattern formation and especially how 2D self-organization can fall into place with successive laser scans. The regular and homogeneous 2D self-organization of metallic NPs with a single laser scan is also reported for the first time in this article. As the reported nanostructures are embedded in porous TiO 2 , we also theoretically explore the interesting potential of organization on the photocatalytic activity of Ag-NP-containing TiO 2 porous films, which is one of the most promising materials for self-cleaning or remediation applications. Realistic electromagnetic simulations demonstrate that the periodic organization of silver nanoparticles can increase the light intensity within the film more than ten times that produced with randomly distributed nanoparticles, leading as expected to enhanced photocatalytic efficiency.

  1. Polarization-driven self-organization of silver nanoparticles in 1D and 2D subwavelength gratings for plasmonic photocatalysis

    NASA Astrophysics Data System (ADS)

    Baraldi, G.; Bakhti, S.; Liu, Z.; Reynaud, S.; Lefkir, Y.; Vocanson, F.; Destouches, N.

    2017-01-01

    One of the main challenges in plasmonics is to conceive large-scale, low-cost techniques suitable for the fabrication of metal nanoparticle patterns showing precise spatial organization. Here, we introduce a simple method based on continuous-wave laser illumination to induce the self-organization of silver nanoparticles within high-index thin films. We show that highly regular and homogeneous nanoparticle gratings can be produced on large areas using laser-controlled self-organization processes. This very versatile technique can provide 1D and 2D patterns at a subwavelength scale with tunable features. It does not need any stabilization or expensive devices, such as those required by optical or electron lithography, and is rapid to implement. Accurate in-plane and in-depth characterizations provide valuable information to explain the mechanisms that lead to pattern formation and especially how 2D self-organization can fall into place with successive laser scans. The regular and homogeneous 2D self-organization of metallic NPs with a single laser scan is also reported for the first time in this article. As the reported nanostructures are embedded in porous TiO2, we also theoretically explore the interesting potential of organization on the photocatalytic activity of Ag-NP-containing TiO2 porous films, which is one of the most promising materials for self-cleaning or remediation applications. Realistic electromagnetic simulations demonstrate that the periodic organization of silver nanoparticles can increase the light intensity within the film more than ten times that produced with randomly distributed nanoparticles, leading as expected to enhanced photocatalytic efficiency.

  2. Preparation and UV-Vis photodegradation of gaseous benzene by TiO2 nanotube arrays supporting V2O5 nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhao, Chunxia; Song, Yanbao; Yang, Yunxia; Chen, Wen; Li, Xiaoyu; Wang, Zongsheng

    2015-07-01

    TiO2-based catalysts effective in visible radiation for eliminating organic pollutants have attracted intense research activity as a future generation photocatalytic material. However, recombination of electron-hole pairs through trapping/de-trapping as well as the disadvantages of recycling and separation/filtration of powders lead to the limitation of powder TiO2 materials. TiO2 nanotube array films supporting vanadium pentoxide nanoparticles (VTNTs) were synthesized by electrophoresis deposition method with the prepared TiO2 nanotube arrays as the cathode and V2O5 sol as the electrolyte. The results indicate that the formation of Ti-O-V bonds and intimate interaction between host-guest interfaces help to enhance the hybrids’ photodegradation activity of gaseous benzene. Importantly, hybrid film catalysts prepared with 0.05 mol/L V2O5 sol for 10 min electrophoresis deposition perform a 98% conversion rate of benzene and 1028.8 mg/m3CO2 production in 80 min under UV-Vis irradiation.

  3. Effects of Functionalization of TiO2 Nanotube Array Sensors with Pd Nanoparticles on Their Selectivity

    PubMed Central

    Park, Sunghoon; Kim, Soohyun; Park, Suyoung; Lee, Wan In; Lee, Chongmu

    2014-01-01

    This study compared the responses of Pd-functionalized and pristine titanate (TiO2) nanotube arrays to ethanol with those to acetone to determine the effects of functionalization of TiO2 nanotubes with Pd nanoparticles on the sensitivity and selectivity. The responses of pristine and Pd-functionalized TiO2 nanotube arrays to ethanol gas at 200 °C were ∼2877% and ∼21,253%, respectively. On the other hand, the responses of pristine and Pd-functionalized TiO2 nanotube arrays to acetone gas at 250 °C were ∼1636% and 8746% respectively. In the case of ethanol sensing, the response and recovery times of Pd-functionalized TiO2 nanotubes (10.2 and 7.1 s) were obviously shorter than those of pristine TiO2 nanotubes (14.3 and 8.8 s), respectively. In contrast, in the case of acetone sensing the response and recovery times of Pd-functionalized TiO2 nanotubes (42.5 and 19.7 s) were almost the same as those of pristine TiO2 nanotubes (47.2 and 17.9 s). TiO2 nanotube arrays showed the strongest response to ethanol and Pd functionalization was the most effective in improving the response of TiO2 nanotubes to ethanol among six different types of gases: ethanol, acetone, CO, H2, NH3 and NO2. The origin of the superior sensing properties of Pd-functionalized TiO2 nanotubes toward ethanol to acetone is also discussed. PMID:25166499

  4. Delivery of human NKG2D-IL-15 fusion gene by chitosan nanoparticles to enhance antitumor immunity.

    PubMed

    Yan, Chen; Jie, Leng; Yongqi, Wang; Weiming, Xiao; Juqun, Xi; Yanbing, Ding; Li, Qian; Xingyuan, Pan; Mingchun, Ji; Weijuan, Gong

    2015-07-31

    Nanoparticles are becoming promising carriers for gene delivery because of their high capacity in gene loading and low cell cytotoxicity. In this study, a chitosan-based nanoparticle encapsulated within a recombinant pcDNA3.1-dsNKG2D-IL-15 plasmid was generated. The fused dsNKG2D-IL-15 gene fragment consisted of double extracellular domains of NKG2D with IL-15 gene at downstream. The average diameter of the gene nanoparticles ranged from 200 nm to 400 nm, with mean zeta potential value of 53.8 ± 6.56 mV. The nanoparticles which were loaded with the dsNKG2D-IL-15 gene were uptaken by tumor cells with low cytotoxicity. Tumor cells pre-transfected by gene nanopartilces stimulated NK and T cells in vitro. Intramuscular injection of gene nanoparticles suppressed tumor growth and prolonged survival of tumor-bearing mice through activation of NK and CD8(+) T cells. Thus, chitosan-based nanoparticle delivery of dsNKG2D-IL-15 gene vaccine can be potentially used for tumor therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Tunable laser interference lithography preparation of plasmonic nanoparticle arrays tailored for SERS.

    PubMed

    Gisbert Quilis, Nestor; Lequeux, Médéric; Venugopalan, Priyamvada; Khan, Imran; Knoll, Wolfgang; Boujday, Souhir; Lamy de la Chapelle, Marc; Dostalek, Jakub

    2018-05-23

    The facile preparation of arrays of plasmonic nanoparticles over a square centimeter surface area is reported. The developed method relies on tailored laser interference lithography (LIL) that is combined with dry etching and it offers means for the rapid fabrication of periodic arrays of metallic nanostructures with well controlled morphology. Adjusting the parameters of the LIL process allows for the preparation of arrays of nanoparticles with a diameter below hundred nanometers independently of their lattice spacing. Gold nanoparticle arrays were precisely engineered to support localized surface plasmon resonance (LSPR) with different damping at desired wavelengths in the visible and near infrared part of the spectrum. The applicability of these substrates for surface enhanced Raman scattering is demonstrated where cost-effective, uniform and reproducible substrates are of paramount importance. The role of deviations in the spectral position and the width of the LSPR band affected by slight variations of plasmonic nanostructures is discussed.

  6. Gold nanoparticle array formation on dimpled Ta templates using pulsed laser-induced thin film dewetting.

    PubMed

    El-Sayed, Hany A; Horwood, Corie A; Owusu-Ansah, Ebenezer; Shi, Yujun J; Birss, Viola I

    2015-04-28

    Here we show that pulsed laser-induced dewetting (PLiD) of a thin Au metallic film on a nano-scale ordered dimpled tantalum (DT) surface results in the formation of a high quality Au nanoparticle (NP) array. In contrast to thermal dewetting, PLiD does not result in deformation of the substrate, even when the Au film is heated to above its melting point. PLiD causes local heating of only the metal film and thus thermal oxidation of the Ta substrate can be avoided, also because of the high vacuum (low pO2) environment employed. Therefore, this technique can potentially be used to fabricate NP arrays composed of high melting point metals, such as Pt, not previously possible using conventional thermal annealing methods. We also show that the Au NPs formed by PLiD are more spherical in shape than those formed by thermal dewetting, likely demonstrating a different dewetting mechanism in the two cases. As the metallic NPs formed on DT templates are electrochemically addressable, a longer-term objective of this work is to determine the effect of NP size and shape (formed by laser vs. thermal dewetting) on their electrocatalytic properties.

  7. A 2-D Array of Superconducting Magnesium Diboride (MgB2) Far-IR Thermal Detectors for Planetary Exploration

    NASA Technical Reports Server (NTRS)

    Lakew, Brook

    2009-01-01

    A 2-D array of superconducting Magnesium Diboride(MgB2) far IR thermal detectors has been fabricated. Such an array is intended to be at the focal plane of future generation thermal imaging far-IR instruments that will investigate the outer planets and their icy moons. Fabrication and processing of the pixels of the array as well as noise characterization of architectured MgB2 thin films will be presented. Challenges and solutions for improving the performance of the array will be discussed.

  8. Pattern transfer from nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Hogg, Charles R., III

    This project contributes to the long-term extensibility of bit-patterned media (BPM), by removing obstacles to using a new and smaller class of self-assembling materials: surfactant-coated nanoparticles. Self-assembly rapidly produces regular patterns of small features over large areas. If these patterns can be used as templates for magnetic bits, the resulting media would have both high capacity and high bit density. The data storage industry has identified block copolymers (BCP) as the self-assembling technology for the first generation of BPM. Arrays of surfactant-coated nanoparticles have long shown higher feature densities than BCP, but their patterns could not previously be transferred into underlying substrates. I identify one key obstacle that has prevented this pattern transfer: the particles undergo a disordering transition during etching which I have called "cracking". I compare several approaches to measuring the degree of cracking, and I develop two novel techniques for preventing it and allowing pattern transfer. I demonstrate two different kinds of pattern transfer: positive (dots) and negative (antidots). To make dots, I etch the substrate between the particles with a directional CF4-based reactive ion etch (RIE). I find the ultrasmall gaps (just 2 nm) cause a tremendous slowdown in the etch rate, by a factor of 10 or more---an observation of fundamental significance for any pattern transfer at ultrahigh bit densities. Antidots are made by depositing material in the interstices, then removing the particles to leave behind a contiguous inorganic lattice. This lattice can itself be used as an etch mask for CF4-based RIE, in order to increase the height contrast. The antidot process promises great generality in choice of materials, both for the antidot lattice and the particles themselves; here, I present lattices of Al and Cr, ternplated from arrays of 13.7 nm-diameter Fe3O4 or 30 nm-diameter MnO nanoparticles. The fidelity of transfer is also

  9. Ultrafast dynamics of metal plasmons induced by 2D semiconductor excitons in hybrid nanostructure arrays

    DOE PAGES

    Boulesbaa, Abdelaziz; Babicheva, Viktoriia E.; Wang, Kai; ...

    2016-11-17

    With the advanced progress achieved in the field of nanotechnology, localized surface plasmons resonances (LSPRs) are actively considered to improve the efficiency of metal-based photocatalysis, photodetection, and photovoltaics. Here, we report on the exchange of energy and electric charges in a hybrid composed of a two-dimensional tungsten disulfide (2D-WS 2) monolayer and an array of aluminum (Al) nanodisks. Femtosecond pump-probe spectroscopy results indicate that within ~830 fs after photoexcitation of the 2D-WS 2 semiconductor, energy transfer from the 2D-WS 2 excitons excites the plasmons of the Al array. Then, upon the radiative and/or nonradiative damping of these excited plasmons, energymore » and/or electron transfer back to the 2D-WS 2 semiconductor takes place as indicated by an increase in the reflected probe at the 2D exciton transition energies at later time-delays. This simultaneous exchange of energy and charges between the metal and the 2D-WS 2 semiconductor resulted in an extension of the average lifetime of the 2D-excitons from ~15 to ~58 ps in absence and presence of the Al array, respectively. Furthermore, the indirectly excited plasmons were found to live as long as the 2D-WS 2 excitons exist. Furthermore, the demonstrated ability to generate exciton-plasmons coupling in a hybrid nanostructure may open new opportunities for optoelectronic applications such as plasmonic-based photodetection and photocatalysis.« less

  10. Programmed Nanoparticle-Loaded Nanoparticles for Deep-Penetrating 3D Cancer Therapy.

    PubMed

    Kim, Jinhwan; Jo, Changshin; Lim, Won-Gwang; Jung, Sungjin; Lee, Yeong Mi; Lim, Jun; Lee, Haeshin; Lee, Jinwoo; Kim, Won Jong

    2018-05-18

    Tumors are 3D, composed of cellular agglomerations and blood vessels. Therapies involving nanoparticles utilize specific accumulations due to the leaky vascular structures. However, systemically injected nanoparticles are mostly uptaken by cells located on the surfaces of cancer tissues, lacking deep penetration into the core cancer regions. Herein, an unprecedented strategy, described as injecting "nanoparticle-loaded nanoparticles" to address the long-lasting problem is reported for effective surface-to-core drug delivery in entire 3D tumors. The "nanoparticle-loaded nanoparticle" is a silica nanoparticle (≈150 nm) with well-developed, interconnected channels (diameter of ≈30 nm), in which small gold nanoparticles (AuNPs) (≈15 nm) with programmable DNA are located. The nanoparticle (AuNPs)-loaded nanoparticles (silica): (1) can accumulate in tumors through leaky vascular structures by protecting the inner therapeutic AuNPs during blood circulation, and then (2) allow diffusion of the AuNPs for penetration into the entire surface-to-core tumor tissues, and finally (3) release a drug triggered by cancer-characteristic pH gradients. The hierarchical "nanoparticle-loaded nanoparticle" can be a rational design for cancer therapies because the outer large nanoparticles are effective in blood circulation and in protection of the therapeutic nanoparticles inside, allowing the loaded small nanoparticles to penetrate deeply into 3D tumors with anticancer drugs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Chemiresistive Sensor Arrays from Conductive 2D Metal–Organic Frameworks

    DOE PAGES

    Campbell, Michael G.; Liu, Sophie F.; Swager, Timothy M.; ...

    2015-10-11

    Applications of porous metal–organic frameworks (MOFs) in electronic devices are rare, owing in large part to a lack of MOFs that display electrical conductivity. Here, we describe the use of conductive two-dimensional (2D) MOFs as a new class of materials for chemiresistive sensing of volatile organic compounds (VOCs). We demonstrate that a family of structurally analogous 2D MOFs can be used to construct a cross-reactive sensor array that allows for clear discrimination between different categories of VOCs. Lastly, experimental data show that multiple sensing mechanisms are operative with high degrees of orthogonality, establishing that the 2D MOFs used here aremore » mechanistically unique and offer advantages relative to other known chemiresistor materials.« less

  12. Synthesis, characterization, and 3D-FDTD simulation of Ag@SiO2 nanoparticles for shell-isolated nanoparticle-enhanced Raman spectroscopy.

    PubMed

    Uzayisenga, Viviane; Lin, Xiao-Dong; Li, Li-Mei; Anema, Jason R; Yang, Zhi-Lin; Huang, Yi-Fan; Lin, Hai-Xin; Li, Song-Bo; Li, Jian-Feng; Tian, Zhong-Qun

    2012-06-19

    Au-seed Ag-growth nanoparticles of controllable diameter (50-100 nm), and having an ultrathin SiO(2) shell of controllable thickness (2-3 nm), were prepared for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Their morphological, optical, and material properties were characterized; and their potential for use as a versatile Raman signal amplifier was investigated experimentally using pyridine as a probe molecule and theoretically by the three-dimensional finite-difference time-domain (3D-FDTD) method. We show that a SiO(2) shell as thin as 2 nm can be synthesized pinhole-free on the Ag surface of a nanoparticle, which then becomes the core. The dielectric SiO(2) shell serves to isolate the Raman-signal enhancing core and prevent it from interfering with the system under study. The SiO(2) shell also hinders oxidation of the Ag surface and nanoparticle aggregation. It significantly improves the stability and reproducibility of surface-enhanced Raman scattering (SERS) signal intensity, which is essential for SERS applications. Our 3D-FDTD simulations show that Ag-core SHINERS nanoparticles yield at least 2 orders of magnitude greater enhancement than Au-core ones when excited with green light on a smooth Ag surface, and thus add to the versatility of our SHINERS method.

  13. Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.

    PubMed

    Rey, By Marcel; Elnathan, Roey; Ditcovski, Ran; Geisel, Karen; Zanini, Michele; Fernandez-Rodriguez, Miguel-Angel; Naik, Vikrant V; Frutiger, Andreas; Richtering, Walter; Ellenbogen, Tal; Voelcker, Nicolas H; Isa, Lucio

    2016-01-13

    We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.

  14. High precision and high yield fabrication of dense nanoparticle arrays onto DNA origami at statistically independent binding sites

    NASA Astrophysics Data System (ADS)

    Takabayashi, Sadao; Klein, William P.; Onodera, Craig; Rapp, Blake; Flores-Estrada, Juan; Lindau, Elias; Snowball, Lejmarc; Sam, Joseph T.; Padilla, Jennifer E.; Lee, Jeunghoon; Knowlton, William B.; Graugnard, Elton; Yurke, Bernard; Kuang, Wan; Hughes, William L.

    2014-10-01

    High precision, high yield, and high density self-assembly of nanoparticles into arrays is essential for nanophotonics. Spatial deviations as small as a few nanometers can alter the properties of near-field coupled optical nanostructures. Several studies have reported assemblies of few nanoparticle structures with controlled spacing using DNA nanostructures with variable yield. Here, we report multi-tether design strategies and attachment yields for homo- and hetero-nanoparticle arrays templated by DNA origami nanotubes. Nanoparticle attachment yield via DNA hybridization is comparable with streptavidin-biotin binding. Independent of the number of binding sites, >97% site-occupation was achieved with four tethers and 99.2% site-occupation is theoretically possible with five tethers. The interparticle distance was within 2 nm of all design specifications and the nanoparticle spatial deviations decreased with interparticle spacing. Modified geometric, binomial, and trinomial distributions indicate that site-bridging, steric hindrance, and electrostatic repulsion were not dominant barriers to self-assembly and both tethers and binding sites were statistically independent at high particle densities.High precision, high yield, and high density self-assembly of nanoparticles into arrays is essential for nanophotonics. Spatial deviations as small as a few nanometers can alter the properties of near-field coupled optical nanostructures. Several studies have reported assemblies of few nanoparticle structures with controlled spacing using DNA nanostructures with variable yield. Here, we report multi-tether design strategies and attachment yields for homo- and hetero-nanoparticle arrays templated by DNA origami nanotubes. Nanoparticle attachment yield via DNA hybridization is comparable with streptavidin-biotin binding. Independent of the number of binding sites, >97% site-occupation was achieved with four tethers and 99.2% site-occupation is theoretically possible with five

  15. High-density arrays of titania nanoparticles using monolayer micellar films of diblock copolymers as templates.

    PubMed

    Li, Xue; Lau, King Hang Aaron; Kim, Dong Ha; Knoll, Wolfgang

    2005-05-24

    Highly dense arrays of titania nanoparticles were fabricated using surface micellar films of poly(styrene-block-2-vinylpyridine) diblock copolymers (PS-b-P2VP) as reaction scaffolds. Titania could be introduced selectively within P2VP nanodomains in PS-b-P2VP films through the binary reaction between water molecules trapped in the P2VP domains and the TiCl(4) vapor precursors. Subsequent UV exposure or oxygen plasma treatment removed the organic matrix, leading to titania nanoparticle arrays on the substrate surface. The diameter of the titania domains and the interparticle distance were defined by the lateral scale present in the microphase-separated morphology of the initial PS-b-P2VP films. The typical diameter of titania nanoparticles obtained by oxygen plasma treatment was of the order of approximately 23 nm. Photoluminescence (PL) properties were investigated for films before and after plasma treatment. Both samples showed PL properties with major physical origin due to self-trapped excitons, indicating that the local environment of the titanium atoms is similar.

  16. Low temperature synthesis and sintering of d-UO2 nanoparticles.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nenoff, Tina Maria; Ferreira, Summer Rhodes; Robinson, David B.

    We report on the novel room temperature method of synthesizing advanced nuclear fuels; a method that virtually eliminates any volatility of components. This process uses radiolysis to form stable nanoparticle (NP) nuclear transuranic (TRU) fuel surrogates and in-situ heated stage TEM to sinter the NPs. The radiolysis is performed at Sandia's Gamma Irradiation Facility (GIF) 60Co source (3 x 10{sup 6} rad/hr). Using this method, sufficient quantities of fuels for research purposes can be produced for accelerated advanced nuclear fuel development. We are focused on both metallic and oxide alloy nanoparticles of varying compositions, in particular d-U, d-U/La alloys andmore » d-UO2 NPs. We present detailed descriptions of the synthesis procedures, the characterization of the NPs, the sintering of the NPs, and their stability with temperature. We have employed UV-vis, HRTEM, HAADF-STEM imaging, single particle EDX and EFTEM mapping characterization techniques to confirm the composition and alloying of these NPs.« less

  17. Fabrication of uniformly dispersed Ag nanoparticles loaded TiO{sub 2} nanotube arrays for enhancing photoelectrochemical and photocatalytic performances under visible light irradiation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yi, Junhui; Zhang, Shengsen; Wang, Hongjuan

    2014-12-15

    Graphical abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method, which exhibited the enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation due to the more effective separation of photo-generated electron–hole pairs and faster interfacial charge transfer. - Highlights: • Highly dispersed Ag nanoparticles (NPs) are successfully prepared by polyol method. • Ag NPs are uniformly loaded on the surface of the TiO{sub 2} nanotube arrays (NTs). • Ag/TiO{sub 2}-NTs exhibit the enhanced photocatalytic activity under visible-light. • The enhanced photocurrent ismore » explained by electrochemical impedance spectroscopy. - Abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO{sub 2}-NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO{sub 2}-NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO{sub 2}-NTs is more than 5 times higher than that of pure TiO{sub 2} NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO{sub 2}-NTs prepared by polyol method has been obviously increased.« less

  18. Prescribed nanoparticle cluster architectures and low-dimensional arrays built using octahedral DNA origami frames

    DOE PAGES

    Tian, Ye; Wang, Tong; Liu, Wenyan; ...

    2015-05-25

    Three-dimensional mesoscale clusters that are formed from nanoparticles spatially arranged in pre-determined positions can be thought of as mesoscale analogues of molecules. These nanoparticle architectures could offer tailored properties due to collective effects, but developing a general platform for fabricating such clusters is a significant challenge. Here, we report a strategy for assembling 3D nanoparticle clusters that uses a molecular frame designed with encoded vertices for particle placement. The frame is a DNA origami octahedron and can be used to fabricate clusters with various symmetries and particle compositions. Cryo-electron microscopy is used to uncover the structure of the DNA framemore » and to reveal that the nanoparticles are spatially coordinated in the prescribed manner. We show that the DNA frame and one set of nanoparticles can be used to create nanoclusters with different chiroptical activities. We also show that the octahedra can serve as programmable interparticle linkers, allowing one- and two-dimensional arrays to be assembled that have designed particle arrangements.« less

  19. Small nickel nanoparticle arrays from long chain imidazolium ionic liquids

    DOE PAGES

    Yang, Mei; Campbell, Paul S.; Santini, Catherine C.; ...

    2013-11-08

    A series of six long chain alkyl mono- and bi-cationic imidazolium based salts with bis(trifluoromethylsulfonyl)imide (NTf 2–) as the anion were synthesized and characterized. Single crystal structure of 1-methyl-3-octadecylimidazolium bis(trifluoromethylsulfonyl)imide could be obtained by X-ray analysis. All these long chain alkyl imidazolium based ILs were applied in the synthesis of nickel nanoparticles via chemical decomposition of an organometallic precursor of nickel. In these media, spontaneous decomposition of Ni(COD) 2 (COD = 1,5-cyclooctadiene) in the absence of H 2 occurred giving small NPs (≤4 nm) with narrow size distributions. Interestingly, formation of regularly interspaced NP arrays was also observed in longmore » chain ILs. Lastly, such array formation could be interesting for potential applications such as carbon nanotube growth.« less

  20. Suppression of ITI by array head reading and 2D-equalization

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Suzuto, R.; Osawa, H.; Okamoto, Y.; Kanai, Y.; Muraoka, H.

    2017-05-01

    Two-dimensional magnetic recording (TDMR) by shingled magnetic recording (SMR) draws attention as a next generation technology to increase the recording density in hard disk drive (HDD). It is shown that the two-dimensional finite impulse response (2D-FIR) filter provides gain the reproducing waveforms from an array head with 3 readers in the TDMR under a specification of 4 Tbit/inch.2 We evaluate the effect of the intertrack interference (ITI) reduction by 2D-FIR using the correlation between the real FIR filter output and the partial response class-I (PR1) signal corresponding to recording sequence by the computer simulation. The results show that the 2D-FIR filter is effective to mitigate ITI and improves the signal-to-noise ratio at the discriminate point by about 0.6 dB.

  1. Controllability of the Coulomb charging energy in close-packed nanoparticle arrays.

    PubMed

    Duan, Chao; Wang, Ying; Sun, Jinling; Guan, Changrong; Grunder, Sergio; Mayor, Marcel; Peng, Lianmao; Liao, Jianhui

    2013-11-07

    We studied the electronic transport properties of metal nanoparticle arrays, particularly focused on the Coulomb charging energy. By comparison, we confirmed that it is more reasonable to estimate the Coulomb charging energy using the activation energy from the temperature-dependent zero-voltage conductance. Based on this, we systematically and comprehensively investigated the parameters that could be used to tune the Coulomb charging energy in nanoparticle arrays. We found that four parameters, including the particle core size, the inter-particle distance, the nearest neighboring number, and the dielectric constant of ligand molecules, could significantly tune the Coulomb charging energy.

  2. Time-resolved second-harmonic generation from gold nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Ferrara, D. W.; Tetz, K. A.; McMahon, M. D.; Haglund, R. F., Jr.

    2007-09-01

    We have studied the effects of planar inversion symmetry and particle-coupling of gold nanoparticle (NP) arrays by angle dependent second-harmonic generation (SHG). Time- and angle- resolved measurements were made using a mode-locked Ti:sapphire 800 nm laser onto gold NP arrays with plasmon resonance tuned to match the laser wavelength in order to produce maximum SHG signal. Finite-difference time domain simulations are used to model the near-field distributions for the various geometries and compared to experiment. The arrays were fabricated by focused ion-beam lithography and metal vapor deposition followed by standard lift-off protocols, producing NPs approximately 20nm high with various in-plane dimensions and interparticle gaps. Above a threshold fluence of ~ 7.3 × 10 -5 mJ/cm2 we find that the SHG scales with the third power of intensity, rather than the second, and atomic-force microscopy shows that the NPs have undergone a reshaping process leading to more nearly spherical shapes.

  3. SU-E-T-758: To Determine the Source Dwell Positions of HDR Brachytherapy Using 2D 729 Ion Chamber Array

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Syam; Sitha

    2015-06-15

    Purpose: Determination of source dwell positions of HDR brachytherapy using 2D 729 ion chamber array Methods: Nucletron microselectron HDR and PTW 2D array were used for the study. Different dwell positions were assigned in the HDR machine. Rigid interstitial needles and vaginal applicator were positioned on the 2D array. The 2D array was exposed for this programmed dwell positions. The positional accuracy of the source was analyzed after the irradiation of the 2D array. This was repeated for different dwell positions. Different test plans were transferred from the Oncentra planning system and irradiated with the same applicator position on themore » 2D array. The results were analyzed using the in house developed excel program. Results: Assigned dwell positions versus corresponding detector response were analyzed. The results show very good agreement with the film measurements. No significant variation found between the planned and measured dwell positions. Average dose response with 2D array between the planned and nearby dwell positions was found to be 0.0804 Gy for vaginal cylinder applicator and 0.1234 Gy for interstitial rigid needles. Standard deviation between the doses for all the measured dwell positions for interstitial rigid needle for 1 cm spaced positions were found to be 0.33 and 0.37 for 2cm spaced dwell positions. For intracavitory vaginal applicator this was found to be 0.21 for 1 cm spaced dwell positions and 0.06 for 2cm spaced dwell positions. Intracavitory test plans reproduced on the 2D array with the same applicator positions shows the ideal dose distribution with the TPS planned. Conclusion: 2D array is a good tool for determining the dwell position of HDR brachytherapy. With the in-house developed program in excel it is easy and accurate. The traditional way with film analysis can be replaced by this method, as the films will be more costly.« less

  4. A Dual-Layer Transducer Array for 3-D Rectilinear Imaging

    PubMed Central

    Yen, Jesse T.; Seo, Chi Hyung; Awad, Samer I.; Jeong, Jong S.

    2010-01-01

    2-D arrays for 3-D rectilinear imaging require very large element counts (16,000–65,000). The difficulties in fabricating and interconnecting 2-D arrays with a large number of elements (>5,000) have limited the development of suitable transducers for 3-D rectilinear imaging. In this paper, we propose an alternative solution to this problem by using a dual-layer transducer array design. This design consists of two perpendicular 1-D arrays for clinical 3-D imaging of targets near the transducer. These targets include the breast, carotid artery, and musculoskeletal system. This transducer design reduces the fabrication complexity and the channel count making 3-D rectilinear imaging more realizable. With this design, an effective N × N 2-D array can be developed using only N transmitters and N receivers. This benefit becomes very significant when N becomes greater than 128, for example. To demonstrate feasibility, we constructed a 4 × 4 cm prototype dual-layer array. The transmit array uses diced PZT-5H elements, and the receive array is a single sheet of undiced P[VDF-TrFE] copolymer. The receive elements are defined by the copper traces on the flexible interconnect circuit. The measured −6 dB fractional bandwidth was 80% with a center frequency of 4.8 MHz. At 5 MHz, the nearest neighbor crosstalk of the PZT array and PVDF array was −30.4 ± 3.1 dB and −28.8 ± 3.7 dB respectively. This dual-layer transducer was interfaced with an Ultrasonix Sonix RP system, and a synthetic aperture 3-D data set was acquired. We then performed off-line 3-D beamforming to obtain volumes of nylon wire targets. The theoretical lateral beamwidth was 0.52 mm compared to measured beamwidths of 0.65 mm and 0.67 mm in azimuth and elevation respectively. 3-D images of an 8 mm diameter anechoic cyst phantom were also acquired. PMID:19213647

  5. Oxide-confined 2D VCSEL arrays for high-density inter/intra-chip interconnects

    NASA Astrophysics Data System (ADS)

    King, Roger; Michalzik, Rainer; Jung, Christian; Grabherr, Martin; Eberhard, Franz; Jaeger, Roland; Schnitzer, Peter; Ebeling, Karl J.

    1998-04-01

    We have designed and fabricated 4 X 8 vertical-cavity surface-emitting laser (VCSEL) arrays intended to be used as transmitters in short-distance parallel optical interconnects. In order to meet the requirements of 2D, high-speed optical links, each of the 32 laser diodes is supplied with two individual top contacts. The metallization scheme allows flip-chip mounting of the array modules junction-side down on silicon complementary metal oxide semiconductor (CMOS) chips. The optical and electrical characteristics across the arrays with device pitch of 250 micrometers are quite homogeneous. Arrays with 3 micrometers , 6 micrometers and 10 micrometers active diameter lasers have been investigated. The small devices show threshold currents of 600 (mu) A, single-mode output powers as high as 3 mW and maximum wavelength deviations of only 3 nm. The driving characteristics of all arrays are fully compatible to advanced 3.3 V CMOS technology. Using these arrays, we have measured small-signal modulation bandwidths exceeding 10 GHz and transmitted pseudo random data at 8 Gbit/s channel over 500 m graded index multimode fiber. This corresponds to a data transmission rate of 256 Gbit/s per array of 1 X 2 mm2 footprint area.

  6. Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Zhang, Mingling; Lan, Xu; Weng, Xiaokang; Shu, Qijiang; Wang, Rongfei; Qiu, Feng; Wang, Chong; Yang, Yu

    2018-06-01

    Polystyrene (PS) nanoparticle films with non-close-packed arrays were prepared by using ion beam etching technology. The effects of etching time, beam current, and voltage on the size reduction of PS particles were well investigated. A slow etching rate, about 9.2 nm/min, is obtained for the nanospheres with the diameter of 100 nm. The rate does not maintain constant with increasing the etching time. This may result from the thermal energy accumulated gradually in a long-time bombardment of ion beam. The etching rate increases nonlinearly with the increase of beam current, while it increases firstly then reach its saturation with the increase of beam voltage. The diameter of PS nanoparticles can be controlled in the range from 34 to 88 nm. Based on the non-close-packed arrays of PS nanoparticles, the ordered silicon (Si) nanopillars with their average diameter of 54 nm are fabricated by employing metal-assisted chemical etching technique. Our results pave an effective way to fabricate the ordered nanostructures with the size less than 100 nm.

  7. Formation of Monocrystalline 1D and 2D Architectures via Epitaxial Attachment: Bottom-Up Routes through Surfactant-Mediated Arrays of Oriented Nanocrystals.

    PubMed

    Nakagawa, Yoshitaka; Kageyama, Hiroyuki; Oaki, Yuya; Imai, Hiroaki

    2015-06-09

    Monocrystalline architectures with well-defined shapes were achieved by bottom-up routes through epitaxial attachment of Mn3O4 nanocrystals. The crystallographically continuous 1D chains elongated in the a axis and 2D panels having large a or c faces were obtained by removal of the organic mediator from surfactant-mediated 1D and 2D arrays of Mn3O4 nanocrystals, respectively. Our basal approach indicates that the epitaxial attachment through the surfactant-mediated arrays is utilized for fabrication of a wide variety of micrometric architectures from nanometric crystalline units.

  8. 2D Array of Far-infrared Thermal Detectors: Noise Measurements and Processing Issues

    NASA Technical Reports Server (NTRS)

    Lakew, B.; Aslam, S.; Stevenson, T.

    2008-01-01

    A magnesium diboride (MgB2) detector 2D array for use in future space-based spectrometers is being developed at GSFC. Expected pixel sensitivities and comparison to current state-of-the-art infrared (IR) detectors will be discussed.

  9. Systematic Approach to Electrostatically Induced 2D Crystallization of Nanoparticles at Liquid Interfaces

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fukuto, M.; Kewalramani, S.; Wang, S.

    2011-02-07

    We report an experimental demonstration of a strategy for inducing two-dimensional (2D) crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situ X-ray scattering measurements at the liquid-vapor interface. The assembly was studied as a function ofmore » the solution pH, which was used to vary the charge on CPMV, and of the mole fraction of the cationic lipid in the binary lipid monolayer, which set the interface charge density. The 2D crystallization of CPMV occurred in a narrow pH range just above the particle's isoelectric point, where the particle charge was weakly negative, and only when the cationic-lipid fraction in the monolayer exceeded a threshold. The observed 2D crystals exhibited nearly the same packing density as the densest lattice plane within the known 3D crystals of CPMV. The above electrostatic approach of maximizing interfacial adsorption may provide an efficient route to the crystallization of nanoparticles at aqueous interfaces.« less

  10. Mechanical control of the plasmon coupling with Au nanoparticle arrays fixed on the elastomeric film via chemical bond

    NASA Astrophysics Data System (ADS)

    Bedogni, Elena; Kaneko, Satoshi; Fujii, Shintaro; Kiguchi, Manabu

    2017-03-01

    We have fabricated Au nanoparticle arrays on the flexible poly(dimethylsiloxane) (PDMS) film. The nanoparticles were bound to the film via a covalent bond by a ligand exchange reaction. Thanks to the strong chemical bonding, highly stable and uniformly dispersed Au nanoparticle arrays were fixed on the PDMS film. The Au nanoparticle arrays were characterized by the UV-vis, scanning electron microscope (SEM) and surface enhanced Raman scattering (SERS). The UV-vis and SEM measurements showed the uniformity of the surface-dispersed Au nanoparticles, and SERS measurement confirmed the chemistry of the PDMS film. Reflecting the high stability and the uniformity of the Au nanoparticle arrays, the plasmon wavelength of the Au nanoparticles reversely changed with modulation of the interparticle distance, which was induced by the stretching of the PDMS film. The plasmon wavelength linearly decreased from 664 to 591 nm by stretching of 60%. The plasmon wavelength shift can be explained by the change in the strength of the plasmon coupling which is mechanically controlled by the mechanical strain.

  11. Fresnel Lorentz Microscopy Imaging of Domains in Fe3O4 Nanoparticle Arrays

    NASA Astrophysics Data System (ADS)

    Majetich, S. A.; Evarts, E. R.; Hogg, C.; Yamamoto, K.; Hirayama, T.

    2009-03-01

    Fresnel Lorentz microscopy was used to study the magnetic domain structures of self-assembled nanoparticle arrays as a function of temperature, from 24 to 605 C. 11 nm diameter Fe3O4 nanoparticles with an edge-to-edge spacing of 2.5 nm form magnetic domains through magnetostatic interactions alone. At room temperature stripe domains were evident in monolayer arrays. The average domain size in monolayer regions is larger than that in bilayers. Mean field theories predict a reduced stabilization energy for bilayers, relative to that for monolayers. The domain wall positions were fairly stable up to 500 C, though the contrast in the walls diminished, indicating reduced magnetic order. Above 500 C there were large temperature-dependent changes. The walls surrounding the smaller domains disappeared at lower temperatures than those of the larger domains. Some magnetic contrast was visible up to 575 C, close to the Curie temperature of Fe3O4 (585 C). Transmission electron microscopy after cooling showed that the particle shape and position in the ordered arrays had been preserved during the high temperature imaging experiments.

  12. A Type-2 Block-Component-Decomposition Based 2D AOA Estimation Algorithm for an Electromagnetic Vector Sensor Array.

    PubMed

    Gao, Yu-Fei; Gui, Guan; Xie, Wei; Zou, Yan-Bin; Yang, Yue; Wan, Qun

    2017-04-27

    This paper investigates a two-dimensional angle of arrival (2D AOA) estimation algorithm for the electromagnetic vector sensor (EMVS) array based on Type-2 block component decomposition (BCD) tensor modeling. Such a tensor decomposition method can take full advantage of the multidimensional structural information of electromagnetic signals to accomplish blind estimation for array parameters with higher resolution. However, existing tensor decomposition methods encounter many restrictions in applications of the EMVS array, such as the strict requirement for uniqueness conditions of decomposition, the inability to handle partially-polarized signals, etc. To solve these problems, this paper investigates tensor modeling for partially-polarized signals of an L-shaped EMVS array. The 2D AOA estimation algorithm based on rank- ( L 1 , L 2 , · ) BCD is developed, and the uniqueness condition of decomposition is analyzed. By means of the estimated steering matrix, the proposed algorithm can automatically achieve angle pair-matching. Numerical experiments demonstrate that the present algorithm has the advantages of both accuracy and robustness of parameter estimation. Even under the conditions of lower SNR, small angular separation and limited snapshots, the proposed algorithm still possesses better performance than subspace methods and the canonical polyadic decomposition (CPD) method.

  13. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    PubMed Central

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

    2017-01-01

    Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles. PMID:28287183

  14. 2D Traveling Wave Array Employing a Trapezoidal Dielectric Wedge for Beam Steering

    NASA Technical Reports Server (NTRS)

    Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranada, Felix A.

    2014-01-01

    This presentation addresses the progress made so far in the development of an antenna array with reconfigurable transmission line feeds connecting each element in series. In particular, 2D traveling wave array employing trapezoidal Dielectric Wedge for Beam Steering will be discussed. The presentation includes current status of the effort and suggested future work. The work is being done as part of the NASA Office of the Chief Technologist's Space Technology Research Fellowship (NSTRF).

  15. Microfluidic separation of magnetic nanoparticles on an ordered array of magnetized micropillars

    NASA Astrophysics Data System (ADS)

    Orlandi, G.; Kuzhir, P.; Izmaylov, Y.; Alves Marins, J.; Ezzaier, H.; Robert, L.; Doutre, F.; Noblin, X.; Lomenech, C.; Bossis, G.; Meunier, A.; Sandoz, G.; Zubarev, A.

    2016-06-01

    Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 μ L /min . Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ ∝M a-1.78 within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ ∝M a-1.7 , close to the experimental findings.

  16. Thermal dewetting with a chemically heterogeneous nano-template for self-assembled L1(0) FePt nanoparticle arrays.

    PubMed

    Wang, Liang-Wei; Cheng, Chung-Fu; Liao, Jung-Wei; Wang, Chiu-Yen; Wang, Ding-Shuo; Huang, Kuo-Feng; Lin, Tzu-Ying; Ho, Rong-Ming; Chen, Lih-Juann; Lai, Chih-Huang

    2016-02-21

    A design for the fabrication of metallic nanoparticles is presented by thermal dewetting with a chemically heterogeneous nano-template. For the template, we fabricate a nanostructured polystyrene-b-polydimethylsiloxane (PS-b-PDMS) film on a Si|SiO2 substrate, followed by a thermal annealing and reactive ion etching (RIE) process. This gives a template composed of an ordered hexagonal array of SiOC hemispheres emerging in the polystyrene matrix. After the deposition of a FePt film on this template, we utilize the rapid thermal annealing (RTA) process, which provides in-plane stress, to achieve thermal dewetting and structural ordering of FePt simultaneously. Since the template is composed of different composition surfaces with periodically varied morphologies, it offers more tuning knobs to manipulate the nanostructures. We show that both the decrease in the area of the PS matrix and the increase in the strain energy relaxation transfer the dewetted pattern from the randomly distributed nanoparticles into a hexagonal periodic array of L10 FePt nanoparticles. Transmission electron microscopy with the in situ heating stage reveals the evolution of the dewetting process, and confirms that the positions of nanoparticles are aligned with those of the SiOC hemispheres. The nanoparticles formed by this template-dewetting show an average diameter and center-to-center distance of 19.30 ± 2.09 nm and 39.85 ± 4.80 nm, respectively. The hexagonal array of FePt nanoparticles reveals a large coercivity of 1.5 T, much larger than the nanoparticles fabricated by top-down approaches. This approach offers an efficient pathway toward self-assembled nanostructures in a wide range of material systems.

  17. Array of nanoparticles coupling with quantum-dot: Lattice plasmon quantum features

    NASA Astrophysics Data System (ADS)

    Salmanogli, Ahmad; Gecim, H. Selcuk

    2018-06-01

    In this study, we analyze the interaction of lattice plasmon with quantum-dot in order to mainly examine the quantum features of the lattice plasmon containing the photonic/plasmonic properties. Despite optical properties of the localized plasmon, the lattice plasmon severely depends on the array geometry, which may influence its quantum features such as uncertainty and the second-order correlation function. To investigate this interaction, we consider a closed system containing an array of the plasmonic nanoparticles and quantum-dot. We analyze this system with full quantum theory by which the array electric far field is quantized and the strength coupling of the quantum-dot array is analytically calculated. Moreover, the system's dynamics are evaluated and studied via the Heisenberg-Langevin equations to attain the system optical modes. We also analytically examine the Purcell factor, which shows the effect of the lattice plasmon on the quantum-dot spontaneous emission. Finally, the lattice plasmon uncertainty and its time evolution of the second-order correlation function at different spatial points are examined. These parameters are dramatically affected by the retarded field effect of the array nanoparticles. We found a severe quantum fluctuation at points where the lattice plasmon occurs, suggesting that the lattice plasmon photons are correlated.

  18. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    DOE PAGES

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; ...

    2017-03-13

    There are many challenges to overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. We report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers, in order to begin addressing these challenges (and others). The tethered array of nanoparticles, MnO in this case, bound directly to amore » gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). Our strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles.« less

  19. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Kelly, Daniel P.; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    Electrostatically actuated microshutter arrays consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutters demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  20. A Type-2 Block-Component-Decomposition Based 2D AOA Estimation Algorithm for an Electromagnetic Vector Sensor Array

    PubMed Central

    Gao, Yu-Fei; Gui, Guan; Xie, Wei; Zou, Yan-Bin; Yang, Yue; Wan, Qun

    2017-01-01

    This paper investigates a two-dimensional angle of arrival (2D AOA) estimation algorithm for the electromagnetic vector sensor (EMVS) array based on Type-2 block component decomposition (BCD) tensor modeling. Such a tensor decomposition method can take full advantage of the multidimensional structural information of electromagnetic signals to accomplish blind estimation for array parameters with higher resolution. However, existing tensor decomposition methods encounter many restrictions in applications of the EMVS array, such as the strict requirement for uniqueness conditions of decomposition, the inability to handle partially-polarized signals, etc. To solve these problems, this paper investigates tensor modeling for partially-polarized signals of an L-shaped EMVS array. The 2D AOA estimation algorithm based on rank-(L1,L2,·) BCD is developed, and the uniqueness condition of decomposition is analyzed. By means of the estimated steering matrix, the proposed algorithm can automatically achieve angle pair-matching. Numerical experiments demonstrate that the present algorithm has the advantages of both accuracy and robustness of parameter estimation. Even under the conditions of lower SNR, small angular separation and limited snapshots, the proposed algorithm still possesses better performance than subspace methods and the canonical polyadic decomposition (CPD) method. PMID:28448431

  1. Effect of Refractive Index of Substrate on Fabrication and Optical Properties of Hybrid Au-Ag Triangular Nanoparticle Arrays

    PubMed Central

    Liu, Jing; Chen, Yushan; Cai, Haoyuan; Chen, Xiaoyi; Li, Changwei; Yang, Cheng-Fu

    2015-01-01

    In this study, the nanosphere lithography (NSL) method was used to fabricate hybrid Au-Ag triangular periodic nanoparticle arrays. The Au-Ag triangular periodic arrays were grown on different substrates, and the effect of the refractive index of substrates on fabrication and optical properties was systematically investigated. At first, the optical spectrum was simulated by the discrete dipole approximation (DDA) numerical method as a function of refractive indexes of substrates and mediums. Simulation results showed that as the substrates had the refractive indexes of 1.43 (quartz) and 1.68 (SF5 glass), the nanoparticle arrays would have better refractive index sensitivity (RIS) and figure of merit (FOM). Simulation results also showed that the peak wavelength of the extinction spectra had a red shift when the medium’s refractive index n increased. The experimental results also demonstrated that when refractive indexes of substrates were 1.43 and 1.68, the nanoparticle arrays and substrate had better adhesive ability. Meanwhile, we found the nanoparticles formed a large-scale monolayer array with the hexagonally close-packed structure. Finally, the hybrid Au-Ag triangular nanoparticle arrays were fabricated on quartz and SF5 glass substrates and their experiment extinction spectra were compared with the simulated results.

  2. Toxicity testing of four silver nanoparticle-coated dental castings in 3-D LO2 cell cultures.

    PubMed

    Zhao, Yi-Ying; Chu, Qiang; Shi, Xu-Er; Zheng, Xiao-Dong; Shen, Xiao-Ting; Zhang, Yan-Zhen

    To address the controversial issue of the toxicity of dental alloys and silver nanoparticles in medical applications, an in vivo-like LO2 3-D model was constructed within polyvinylidene fluoride hollow fiber materials to mimic the microenvironment of liver tissue. The use of microscopy methods and the measurement of liver-specific functions optimized the model for best cell performances and also proved the superiority of the 3-D LO2 model when compared with the traditional monolayer model. Toxicity tests were conducted using the newly constructed model, finding that four dental castings coated with silver nanoparticles were toxic to human hepatocytes after cell viability assays. In general, the toxicity of both the castings and the coated silver nanoparticles aggravated as time increased, yet the nanoparticles attenuated the general toxicity by preventing metal ion release, especially at high concentrations.

  3. A distance-controlled nanoparticle array using PEGylated ferritin

    NASA Astrophysics Data System (ADS)

    He, Chao; Uenuma, Mutsunori; Okamoto, Naofumi; Kamitake, Hiroki; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

    2014-12-01

    A distance-controlled nanoparticle (NP) array was investigated using a simple spin coating process. It was found that the separation distance of NPs was controlled at the nanoscale by using polyethylene glycols (PEGs). Ferritin was used to synthesize NPs and carry them to a substrate by using the different molecular weight of PEGs. In order to control the distance of the NPs, PEGs with molecular weights of 2k, 5k, 10k and 20k were modified on ferritin with 10 mM ion strength and 0.01 mg ml-1 ferritin concentration. The separated distances of NPs increased along with increase in PEG molecular weight.

  4. LC-lens array with light field algorithm for 3D biomedical applications

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Pai; Hsieh, Po-Yuan; Hassanfiroozi, Amir; Martinez, Manuel; Javidi, Bahram; Chu, Chao-Yu; Hsuan, Yun; Chu, Wen-Chun

    2016-03-01

    In this paper, liquid crystal lens (LC-lens) array was utilized in 3D bio-medical applications including 3D endoscope and light field microscope. Comparing with conventional plastic lens array, which was usually placed in 3D endoscope or light field microscope system to record image disparity, our LC-lens array has higher flexibility of electrically changing its focal length. By using LC-lens array, the working distance and image quality of 3D endoscope and microscope could be enhanced. Furthermore, the 2D/3D switching ability could be achieved if we turn off/on the electrical power on LClens array. In 3D endoscope case, a hexagonal micro LC-lens array with 350um diameter was placed at the front end of a 1mm diameter endoscope. With applying electric field on LC-lens array, the 3D specimen would be recorded as from seven micro-cameras with different disparity. We could calculate 3D construction of specimen with those micro images. In the other hand, if we turn off the electric field on LC-lens array, the conventional high resolution 2D endoscope image would be recorded. In light field microscope case, the LC-lens array was placed in front of the CMOS sensor. The main purpose of LC-lens array is to extend the refocusing distance of light field microscope, which is usually very narrow in focused light field microscope system, by montaging many light field images sequentially focusing on different depth. With adjusting focal length of LC-lens array from 2.4mm to 2.9mm, the refocusing distance was extended from 1mm to 11.3mm. Moreover, we could use a LC wedge to electrically shift the optics axis and increase the resolution of light field.

  5. Suspension arrays based on nanoparticle-encoded microspheres for high-throughput multiplexed detection

    PubMed Central

    Leng, Yuankui

    2017-01-01

    Spectrometrically or optically encoded microsphere based suspension array technology (SAT) is applicable to the high-throughput, simultaneous detection of multiple analytes within a small, single sample volume. Thanks to the rapid development of nanotechnology, tremendous progress has been made in the multiplexed detecting capability, sensitivity, and photostability of suspension arrays. In this review, we first focus on the current stock of nanoparticle-based barcodes as well as the manufacturing technologies required for their production. We then move on to discuss all existing barcode-based bioanalysis patterns, including the various labels used in suspension arrays, label-free platforms, signal amplification methods, and fluorescence resonance energy transfer (FRET)-based platforms. We then introduce automatic platforms for suspension arrays that use superparamagnetic nanoparticle-based microspheres. Finally, we summarize the current challenges and their proposed solutions, which are centered on improving encoding capacities, alternative probe possibilities, nonspecificity suppression, directional immobilization, and “point of care” platforms. Throughout this review, we aim to provide a comprehensive guide for the design of suspension arrays, with the goal of improving their performance in areas such as multiplexing capacity, throughput, sensitivity, and cost effectiveness. We hope that our summary on the state-of-the-art development of these arrays, our commentary on future challenges, and some proposed avenues for further advances will help drive the development of suspension array technology and its related fields. PMID:26021602

  6. Optical diffraction by ordered 2D arrays of silica microspheres

    NASA Astrophysics Data System (ADS)

    Shcherbakov, A. A.; Shavdina, O.; Tishchenko, A. V.; Veillas, C.; Verrier, I.; Dellea, O.; Jourlin, Y.

    2017-03-01

    The article presents experimental and theoretical studies of angular dependent diffraction properties of 2D monolayer arrays of silica microspheres. High-quality large area defect-free monolayers of 1 μm diameter silica microspheres were deposited by the Langmuir-Blodgett technique under an accurate optical control. Measured angular dependencies of zeroth and one of the first order diffraction efficiencies produced by deposited samples were simulated by the rigorous Generalized Source Method taking into account particle size dispersion and lattice nonideality.

  7. 2D biological representations with reduced speckle obtained from two perpendicular ultrasonic arrays.

    PubMed

    Rodriguez-Hernandez, Miguel A; Gomez-Sacristan, Angel; Sempere-Payá, Víctor M

    2016-04-29

    Ultrasound diagnosis is a widely used medical tool. Among the various ultrasound techniques, ultrasonic imaging is particularly relevant. This paper presents an improvement to a two-dimensional (2D) ultrasonic system using measurements taken from perpendicular planes, where digital signal processing techniques are used to combine one-dimensional (1D) A-scans were acquired by individual transducers in arrays located in perpendicular planes. An algorithm used to combine measurements is improved based on the wavelet transform, which includes a denoising step during the 2D representation generation process. The inclusion of this new denoising stage generates higher quality 2D representations with a reduced level of speckling. The paper includes different 2D representations obtained from noisy A-scans and compares the improvements obtained by including the denoising stage.

  8. Strain induced plasmon tuning in planar square-shaped aluminum nanoparticles array

    NASA Astrophysics Data System (ADS)

    Mokkath, Junais Habeeb

    2018-06-01

    Metal nanoparticle aggregate is an exciting platform for manipulating light-matter interactions at the nanoscale, thanks to the optically driven free electrons couple electrically across the inter-particle gap region. We use time dependent density functional theory calculations to investigate the optical response modulations in planar square-shaped aluminum nanoparticles array via morphology deformation (varying the inter-particle gap distance in the range of 2-20 Å) separately along one and two directions. We report the surprising observation that irrespective of the different morphology deformations, there exists a unique inter-particle gap distance of 12 Å for which, a maximum optical field enhancement can be achieved. We remark that plasmonic interaction between metal nanoparticles in an aggregate is controlled to a large extent by the size of the inter-particle gap distance. We believe that our quantum mechanical calculations will inspire and contribute to the design, control, and exploitation of aluminum based plasmonic devices.

  9. Design a New Strategy Based on Nanoparticle-Enhanced Chemiluminescence Sensor Array for Biothiols Discrimination

    NASA Astrophysics Data System (ADS)

    Shahrajabian, Maryam; Hormozi-Nezhad, M. Reza

    2016-08-01

    Array-based sensor is an interesting approach that suggests an alternative to expensive analytical methods. In this work, we introduce a novel, simple, and sensitive nanoparticle-based chemiluminescence (CL) sensor array for discrimination of biothiols (e.g., cysteine, glutathione and glutathione disulfide). The proposed CL sensor array is based on the CL efficiencies of four types of enhanced nanoparticle-based CL systems. The intensity of CL was altered to varying degrees upon interaction with biothiols, producing unique CL response patterns. These distinct CL response patterns were collected as “fingerprints” and were then identified through chemometric methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). The developed array was able to successfully differentiate between cysteine, glutathione and glutathione disulfide in a wide concentration range. Moreover, it was applied to distinguish among the above analytes in human plasma.

  10. Fabrication of Al2O3 coated 2D TiO2 nanoparticle photonic crystal layers by reverse nano-imprint lithography and plasma enhanced atomic layer deposition.

    PubMed

    Kim, Ki-Kang; Ko, Ki-Young; Ahn, Jinho

    2013-10-01

    This paper reports simple process to enhance the extraction efficiency of photoluminescence (PL) from Eu-doped yttrium oxide (Y2O3:Eu3+) thin-film phosphor (TFP). Two-dimensional (2D) photonic crystal layer (PCL) was fabricated on Y2O3:Eu3+ phosphor films by reverse nano-imprint method using TiO2 nanoparticle solution as a nano-imprint resin and a 2D hole-patterned PDMS stamp. Atomic scale controlled Al2O3 deposition was performed onto this 2D nanoparticle PCL for the optimization of the photonic crystal pattern size and stabilization of TiO2 nanoparticle column structure. As a result, the light extraction efficiency of the Y2O3:Eu3+ phosphor film was improved by 2.0 times compared to the conventional Y2O3:Eu3+ phosphor film.

  11. Joint estimation of 2D-DOA and frequency based on space-time matrix and conformal array.

    PubMed

    Wan, Liang-Tian; Liu, Lu-Tao; Si, Wei-Jian; Tian, Zuo-Xi

    2013-01-01

    Each element in the conformal array has a different pattern, which leads to the performance deterioration of the conventional high resolution direction-of-arrival (DOA) algorithms. In this paper, a joint frequency and two-dimension DOA (2D-DOA) estimation algorithm for conformal array are proposed. The delay correlation function is used to suppress noise. Both spatial and time sampling are utilized to construct the spatial-time matrix. The frequency and 2D-DOA estimation are accomplished based on parallel factor (PARAFAC) analysis without spectral peak searching and parameter pairing. The proposed algorithm needs only four guiding elements with precise positions to estimate frequency and 2D-DOA. Other instrumental elements can be arranged flexibly on the surface of the carrier. Simulation results demonstrate the effectiveness of the proposed algorithm.

  12. Ultrafast Pulse Generation in an Organic Nanoparticle-Array Laser.

    PubMed

    Daskalakis, Konstantinos S; Väkeväinen, Aaro I; Martikainen, Jani-Petri; Hakala, Tommi K; Törmä, Päivi

    2018-04-11

    Nanoscale coherent light sources offer potentially ultrafast modulation speeds, which could be utilized for novel sensors and optical switches. Plasmonic periodic structures combined with organic gain materials have emerged as promising candidates for such nanolasers. Their plasmonic component provides high intensity and ultrafast nanoscale-confined electric fields, while organic gain materials offer fabrication flexibility and a low acquisition cost. Despite reports on lasing in plasmonic arrays, lasing dynamics in these structures have not been experimentally studied yet. Here we demonstrate, for the first time, an organic dye nanoparticle-array laser with more than a 100 GHz modulation bandwidth. We show that the lasing modulation speed can be tuned by the array parameters. Accelerated dynamics is observed for plasmonic lasing modes at the blue side of the dye emission.

  13. Programming Nanoparticles in Multiscale: Optically Modulated Assembly and Phase Switching of Silicon Nanoparticle Array.

    PubMed

    Wang, Letian; Rho, Yoonsoo; Shou, Wan; Hong, Sukjoon; Kato, Kimihiko; Eliceiri, Matthew; Shi, Meng; Grigoropoulos, Costas P; Pan, Heng; Carraro, Carlo; Qi, Dongfeng

    2018-03-27

    Manipulating and tuning nanoparticles by means of optical field interactions is of key interest for nanoscience and applications in electronics and photonics. We report scalable, direct, and optically modulated writing of nanoparticle patterns (size, number, and location) of high precision using a pulsed nanosecond laser. The complex nanoparticle arrangement is modulated by the laser pulse energy and polarization with the particle size ranging from 60 to 330 nm. Furthermore, we report fast cooling-rate induced phase switching of crystalline Si nanoparticles to the amorphous state. Such phase switching has usually been observed in compound phase change materials like GeSbTe. The ensuing modification of atomic structure leads to dielectric constant switching. Based on these effects, a multiscale laser-assisted method of fabricating Mie resonator arrays is proposed. The number of Mie resonators, as well as the resonance peaks and dielectric constants of selected resonators, can be programmed. The programmable light-matter interaction serves as a mechanism to fabricate optical metasurfaces, structural color, and multidimensional optical storage devices.

  14. QCM-D study of nanoparticle interactions.

    PubMed

    Chen, Qian; Xu, Shengming; Liu, Qingxia; Masliyah, Jacob; Xu, Zhenghe

    2016-07-01

    Quartz crystal microbalance with dissipation monitoring (QCM-D) has been proven to be a powerful research tool to investigate in situ interactions between nanoparticles and different functionalized surfaces in liquids. QCM-D can also be used to quantitatively determine adsorption kinetics of polymers, DNA and proteins from solutions on various substrate surfaces while providing insights into conformations of adsorbed molecules. This review aims to provide a comprehensive overview on various important applications of QCM-D, focusing on deposition of nanoparticles and attachment-detachment of nanoparticles on model membranes in complex fluid systems. We will first describe the working principle of QCM-D and DLVO theory pertinent to understanding nanoparticle deposition phenomena. The interactions between different nanoparticles and functionalized surfaces for different application areas are then critically reviewed. Finally, the potential applications of QCM-D in other important fields are proposed and knowledge gaps are identified. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Design of hybrid two-dimensional and three-dimensional nanostructured arrays for electronic and sensing applications

    NASA Astrophysics Data System (ADS)

    Ko, Hyunhyub

    This dissertation presents the design of organic/inorganic hybrid 2D and 3D nanostructured arrays via controlled assembly of nanoscale building blocks. Two representative nanoscale building blocks such as carbon nanotubes (one-dimension) and metal nanoparticles (zero-dimension) are the core materials for the study of solution-based assembly of nanostructured arrays. The electrical, mechanical, and optical properties of the assembled nanostructure arrays have been investigated for future device applications. We successfully demonstrated the prospective use of assembled nanostructure arrays for electronic and sensing applications by designing flexible carbon nanotube nanomembranes as mechanical sensors, highly-oriented carbon nanotubes arrays for thin-film transistors, and gold nanoparticle arrays for SERS chemical sensors. In first section, we fabricated highly ordered carbon nanotube (CNT) arrays by tilted drop-casting or dip-coating of CNT solution on silicon substrates functionalized with micropatterned self-assembled monolayers. We further exploited the electronic performance of thin-film transistors based on highly-oriented, densely packed CNT micropatterns and showed that the carrier mobility is largely improved compared to randomly oriented CNTs. The prospective use of Raman-active CNTs for potential mechanical sensors has been investigated by studying the mechano-optical properties of flexible carbon nanotube nanomembranes, which contain freely-suspended carbon nanotube array encapsulated into ultrathin (<50 nm) layer-by-layer (LbL) polymer multilayers. In second section, we fabricated 3D nano-canal arrays of porous alumina membranes decorated with gold nanoparticles for prospective SERS sensors. We showed extraordinary SERS enhancement and suggested that the high performance is associated with the combined effects of Raman-active hot spots of nanoparticle aggregates and the optical waveguide properties of nano-canals. We demonstrated the ability of this

  16. Indium vacancy induced d0 ferromagnetism in Li-doped In2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Cao, Haiming; Xing, Pengfei; Zhou, Wei; Yao, Dongsheng; Wu, Ping

    2018-04-01

    Li-doped In2O3 nanoparticles with room temperature d0 ferromagnetism were prepared by a sol-gel method. X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence were carried out to investigate the effects of Li incorporation on the lattice defects. As the content of Li increases, non-monotonic changes in shifts of XRD peak (2 2 2) and the intensity ratios of indium vacancies related photoluminescence peak (PII) with respect to oxygen vacancies related peak (PI) are observed. Results show that at low doping level (≤2 at.%) Li prefers to occupy In sites, while with further doping the interstitial sites are more favorable for Li. Combined with the consistent non-monotonic change in saturation magnetization, we think that indium vacancies resulting from Li-doping play an important role in inducing d0 ferromagnetism in our Li-doped In2O3 nanoparticles, and the FM coupling is mainly mediated by the LiIn-ONN-VIn-ONN-LiIn chains.

  17. Hydrothermal solid-gas route to TiO2 nanoparticles/nanotube arrays for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Fan, Haowen; Zhang, He; Luo, Xiaolei; Liao, Maoying; Zhu, Xufei; Ma, Jing; Song, Ye

    2017-07-01

    Although TiO2 nanotube arrays (TNTAs) have shown great promise as supercapacitor materials, their specific capacitances are still not comparable with some typical materials. Here, TiO2 nanoparticles (NPs)/TNTAs hybrid structure has been derived from the anodized TNTAs by a facile hydrothermal solid-gas method (HSGM), which can avoid cracking or curling of the TNTAs from Ti substrate. The obtained NPs/TNTAs hybrid structure can exhibit a ∼4.90 times increase in surface area and a ∼5.49 times increase in areal specific capacitance compared to the TNTAs without HSGM treatment. Besides, the argon-atmosphere annealing can offer improved areal capacitance and cycling stability relative to the air-atmosphere annealing. The hydrothermal vapor pressure is a key factor for controlling microscopic morphologies of TNTAs, the morphology transformations of TNTAs during the HSGM treatment can be accelerated under enhanced vapor pressures. The highest areal capacitance of HSGM-treated TNTAs is up to 76.12 mF cm-2 at 0.5 mA cm-2, well above that of any TiO2 materials reported to date.

  18. Skin Dendritic Cell Targeting via Microneedle Arrays Laden with Antigen-Encapsulated Poly-d,l-lactide-co-Glycolide Nanoparticles Induces Efficient Antitumor and Antiviral Immune Responses

    PubMed Central

    2013-01-01

    The efficacious delivery of antigens to antigen-presenting cells (APCs), in particular, to dendritic cells (DCs), and their subsequent activation remains a significant challenge in the development of effective vaccines. This study highlights the potential of dissolving microneedle (MN) arrays laden with nanoencapsulated antigen to increase vaccine immunogenicity by targeting antigen specifically to contiguous DC networks within the skin. Following in situ uptake, skin-resident DCs were able to deliver antigen-encapsulated poly-d,l-lactide-co-glycolide (PGLA) nanoparticles to cutaneous draining lymph nodes where they subsequently induced significant expansion of antigen-specific T cells. Moreover, we show that antigen-encapsulated nanoparticle vaccination via microneedles generated robust antigen-specific cellular immune responses in mice. This approach provided complete protection in vivo against both the development of antigen-expressing B16 melanoma tumors and a murine model of para-influenza, through the activation of antigen-specific cytotoxic CD8+ T cells that resulted in efficient clearance of tumors and virus, respectively. In addition, we show promising findings that nanoencapsulation facilitates antigen retention into skin layers and provides antigen stability in microneedles. Therefore, the use of biodegradable polymeric nanoparticles for selective targeting of antigen to skin DC subsets through dissolvable MNs provides a promising technology for improved vaccination efficacy, compliance, and coverage. PMID:23373658

  19. Surface-enhanced Raman scattering active gold nanoparticle/nanohole arrays fabricated through electron beam lithography

    NASA Astrophysics Data System (ADS)

    Wu, Tsunghsueh; Lin, Yang-Wei

    2018-03-01

    Effective surface-enhanced Raman scattering (SERS)-active substrates from gold nanoparticle and gold nanohole arrays were successfully fabricated through electron beam lithography with precise computer-aided control of the unit size and intergap distance. Their SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA). These gold arrays yielded strong SERS signals under 785 nm laser excitation. The enhancement factors for 4-MBA molecules on the prepared gold nanoparticle and nanohole arrays maxed at 1.08 × 107 and 8.61 × 106, respectively. The observed increase in SERS enhancement was attributed to the localized surface plasmon resonance (LSPR) wavelength shifting toward the near-infrared regime when the gold nanohole diameter increased, in agreement with the theoretical prediction in this study. The contribution of LSPR to the Raman enhancement from nanohole arrays deposited on fluorine-doped tin oxide glass was elucidated by comparing SERS and transmission spectra. This simple fabrication procedure, which entails employing electron beam lithography and the controllability of the intergap distance, suggests highly promising uses of nanohole arrays as functional components in sensing and photonic devices.

  20. A comparison of 1D and 1.5D arrays for imaging volumetric flaws in small bore pipework

    NASA Astrophysics Data System (ADS)

    Barber, T. S.; Wilcox, P. D.; Nixon, A. D.

    2015-03-01

    1.5D arrays can be seen as a potentially ideal compromise between 1D arrays and 2D matrix arrays in terms of focusing capability, element density, weld coverage and data processing time. This paper presents an initial study of 1D and 1.5D arrays for high frequency (15MHz) imaging of volumetric flaws in small-bore (30-60mm outer diameter) thin-walled (3-8mm) pipework. A combination of 3D modelling and experimental work is used to determine Signal to Noise Ratio (SNR) improvement with a strong relationship between SNR and the longer dimension of element size observed. Similar behavior is demonstrated experimentally rendering a 1mm diameter Flat Bottom Hole (FBH) in Copper-Nickel alloy undetectable using a larger array element. A 3-5dB SNR increase is predicted when using a 1.5D array assuming a spherical reflector and a 2dB increase was observed on experimental trials with a FBH. It is argued that this improvement is likely to be a lower bound estimate due to the specular behavior of a FBH with future trials planned on welded samples with realistic flaws.

  1. Diversity of chimera-like patterns from a model of 2D arrays of neurons with nonlocal coupling

    NASA Astrophysics Data System (ADS)

    Tian, Chang-Hai; Zhang, Xi-Yun; Wang, Zhen-Hua; Liu, Zong-Hua

    2017-06-01

    Chimera states have been studied in 1D arrays, and a variety of different chimera states have been found using different models. Research has recently been extended to 2D arrays but only to phase models of them. Here, we extend it to a nonphase model of 2D arrays of neurons and focus on the influence of nonlocal coupling. Using extensive numerical simulations, we find, surprisingly, that this system can show most types of previously observed chimera states, in contrast to previous models, where only one or a few types of chimera states can be observed in each model. We also find that this model can show some special chimera-like patterns such as gridding and multicolumn patterns, which were previously observed only in phase models. Further, we present an effective approach, i.e., removing some of the coupling links, to generate heterogeneous coupling, which results in diverse chimera-like patterns and even induces transformations from one chimera-like pattern to another.

  2. Nanohole-array-based device for 2D snapshot multispectral imaging

    PubMed Central

    Najiminaini, Mohamadreza; Vasefi, Fartash; Kaminska, Bozena; Carson, Jeffrey J. L.

    2013-01-01

    We present a two-dimensional (2D) snapshot multispectral imager that utilizes the optical transmission characteristics of nanohole arrays (NHAs) in a gold film to resolve a mixture of input colors into multiple spectral bands. The multispectral device consists of blocks of NHAs, wherein each NHA has a unique periodicity that results in transmission resonances and minima in the visible and near-infrared regions. The multispectral device was illuminated over a wide spectral range, and the transmission was spectrally unmixed using a least-squares estimation algorithm. A NHA-based multispectral imaging system was built and tested in both reflection and transmission modes. The NHA-based multispectral imager was capable of extracting 2D multispectral images representative of four independent bands within the spectral range of 662 nm to 832 nm for a variety of targets. The multispectral device can potentially be integrated into a variety of imaging sensor systems. PMID:24005065

  3. Collective photonic-plasmonic resonances in noble metal - dielectric nanoparticle hybrid arrays

    DOE PAGES

    Hong, Yan; Reinhard, Björn M.

    2014-10-27

    Coherent scattering of gold and silver nanoparticles (NPs) in regular arrays can generate Surface Lattice Resonances (SLRs) with characteristically sharp spectral features. Herein, we investigate collective resonances in compositionally more complex arrays comprising NP clusters and NPs with different chemical compositions at pre-defined lattice sites. We first characterize the impact of NP clustering by exchanging individual gold NPs in the array through dimers of electromagnetically strongly coupled gold NPs. Then, we analyze hybrid arrays that contain both gold metal NP dimers and high refractive index dielectric NPs as building blocks. We demonstrate that the integration of gold NP clusters andmore » dielectric NPs into one array enhances E-field intensities not only in the vicinity of the NPs but also in the ambient medium of the entire array. In addition, this work shows that the ability to integrate multiple building blocks with different resonance conditions in one array provides new degrees of freedom for engineering optical fields in the array plane with variable amplitude and phase.« less

  4. Ordered nanoparticle arrays formed on engineered chaperonin protein templates

    NASA Technical Reports Server (NTRS)

    McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

    2002-01-01

    Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

  5. Engineered spin-spin interactions on a 2D array of trapped ions

    NASA Astrophysics Data System (ADS)

    Britton, Joe; Sawyer, Brian; Bollinger, John

    2013-05-01

    We work with laser cooled 9Be+ ions confined in a Penning trap to simulate quantum magnetic interactions. The valence electron of each ion behaves as an ideal spin- 1 / 2 particle. We recently demonstrated a uniform anti-ferromagnetic Ising interaction on a naturally occurring two-dimensional (2D) triangular crystal of 100 < N < 350 ions. The Ising interaction is generated by a spin-dependent optical dipole force (ODF). For spins separated by distance d, we show that the range can be tuned according to (d / d 0)-a, for 0 < a < 3 . For different operating parameters we can also generate an infinite range ferromagnetic Ising interaction. We also use the ODF for spectroscopy and thermometry of the normal modes of the trapped ion array. A detailed understanding of the modes is important because they mediate the spin-spin interactions. This work is supported by NIST and the DARPA OLE program.

  6. Guided Lamb wave based 2-D spiral phased array for structural health monitoring of thin panel structures

    NASA Astrophysics Data System (ADS)

    Yoo, Byungseok

    2011-12-01

    In almost all industries of mechanical, aerospace, and civil engineering fields, structural health monitoring (SHM) technology is essentially required for providing the reliable information of structural integrity of safety-critical structures, which can help reduce the risk of unexpected and sometimes catastrophic failures, and also offer cost-effective inspection and maintenance of the structures. State of the art SHM research on structural damage diagnosis is focused on developing global and real-time technologies to identify the existence, location, extent, and type of damage. In order to detect and monitor the structural damage in plate-like structures, SHM technology based on guided Lamb wave (GLW) interrogation is becoming more attractive due to its potential benefits such as large inspection area coverage in short time, simple inspection mechanism, and sensitivity to small damage. However, the GLW method has a few critical issues such as dispersion nature, mode conversion and separation, and multiple-mode existence. Phased array technique widely used in all aspects of civil, military, science, and medical industry fields may be employed to resolve the drawbacks of the GLW method. The GLW-based phased array approach is able to effectively examine and analyze complicated structural vibration responses in thin plate structures. Because the phased sensor array operates as a spatial filter for the GLW signals, the array signal processing method can enhance a desired signal component at a specific direction while eliminating other signal components from other directions. This dissertation presents the development, the experimental validation, and the damage detection applications of an innovative signal processing algorithm based on two-dimensional (2-D) spiral phased array in conjunction with the GLW interrogation technique. It starts with general backgrounds of SHM and the associated technology including the GLW interrogation method. Then, it is focused on the

  7. Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting

    PubMed Central

    Lee, Sun-Kyu; Hwang, Sori; Kim, Yoon-Kee

    2017-01-01

    We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol–gel (IGSG) resist on glass using a two-layer polydimethylsiloxane (PDMS) stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures. The microstructural and mechanical characteristics that developed during the processes were discussed. The results are promising for low-cost mass fabrication of devices for several photonic applications. PMID:28546899

  8. Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting.

    PubMed

    Lee, Sun-Kyu; Hwang, Sori; Kim, Yoon-Kee; Oh, Yong-Jun

    2017-01-01

    We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol-gel (IGSG) resist on glass using a two-layer polydimethylsiloxane (PDMS) stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures. The microstructural and mechanical characteristics that developed during the processes were discussed. The results are promising for low-cost mass fabrication of devices for several photonic applications.

  9. Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals.

    PubMed

    Li, Yunfeng; Prince, Elisabeth; Cho, Sangho; Salari, Alinaghi; Mosaddeghian Golestani, Youssef; Lavrentovich, Oleg D; Kumacheva, Eugenia

    2017-02-28

    An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two self-assembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids.

  10. SU-F-T-281: Monte Carlo Investigation of Sources of Dosimetric Discrepancies with 2D Arrays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Afifi, M; Deiab, N; El-Farrash, A

    2016-06-15

    Purpose: Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA). Understanding the limitations and use of dosimeters to measure these dose distributions is critical to safe IMRT implementation. In this work, we used Monte Carlo simulations to investigate the possible sources of discrepancy between our measurement with 2D array system and our dose calculation using our treatment planning system (TPS). Material and Methods: MCBEAM and MCSIM Monte Carlo codes were used for treatment head simulation and phantom dose calculation. Accurate modeling of a 6MV beam from Varian trilogy machine wasmore » verified by comparing simulated and measured percentage depth doses and profiles. Dose distribution inside the 2D array was calculated using Monte Carlo simulations and our TPS. Then Cross profiles for different field sizes were compared with actual measurements for zero and 90° gantry angle setup. Through the analysis and comparison, we tried to determine the differences and quantify a possible angular calibration factor. Results: Minimum discrepancies was seen in the comparison between the simulated and the measured profiles for the zero gantry angles at all studied field sizes (4×4cm{sup 2}, 10×10cm{sup 2}, 15×15cm{sup 2}, and 20×20cm{sup 2}). Discrepancies between our measurements and calculations increased dramatically for the cross beam profiles at the 90° gantry angle. This could ascribe mainly to the different attenuation caused by the layer of electronics at the base behind the ion chambers in the 2D array. The degree of attenuation will vary depending on the angle of beam incidence. Correction factors were implemented to correct the errors. Conclusion: Monte Carlo modeling of the 2D arrays and the derivation of angular dependence correction factors will allow for improved accuracy of the device for IMRT QA.« less

  11. Photochemical induced growth and aggregation of metal nanoparticles in diode-array spectrophotometer via excited dimethyl-sulfoxide.

    PubMed

    Zidki, Tomer; Cohen, Haim; Meyerstein, Dan

    2010-10-21

    Ag(0) and Au(0) nanoparticles suspended in dilute aqueous solutions containing (CH(3))(2)SO are photochemically unstable. The light source of a diode-array spectrophotometer induces, within less than a minute, particle growth and aggregation. The results indicate that this process is triggered by UV light absorption by the (CH(3))(2)SO.

  12. Characterization of anisotropically shaped silver nanoparticle arrays via spectroscopic ellipsometry supported by numerical optical modeling

    NASA Astrophysics Data System (ADS)

    Gkogkou, Dimitra; Shaykhutdinov, Timur; Oates, Thomas W. H.; Gernert, Ulrich; Schreiber, Benjamin; Facsko, Stefan; Hildebrandt, Peter; Weidinger, Inez M.; Esser, Norbert; Hinrichs, Karsten

    2017-11-01

    The present investigation aims to study the optical response of anisotropic Ag nanoparticle arrays deposited on rippled silicon substrates by performing a qualitative comparison between experimental and theoretical results. Spectroscopic ellipsometry was used along with numerical calculations using finite-difference time-domain (FDTD) method and rigorous coupled wave analysis (RCWA) to reveal trends in the optical and geometrical properties of the nanoparticle array. Ellipsometric data show two resonances, in the orthogonal x and y directions, that originate from localized plasmon resonances as demonstrated by the calculated near-fields from FDTD calculations. The far-field calculations by RCWA point to decoupled resonances in x direction and possible coupling effects in y direction, corresponding to the short and long axis of the anisotropic nanoparticles, respectively.

  13. Collective mechanical behavior of multilayer colloidal arrays of hollow nanoparticles.

    PubMed

    Yin, Jie; Retsch, Markus; Thomas, Edwin L; Boyce, Mary C

    2012-04-03

    The collective mechanical behavior of multilayer colloidal arrays of hollow silica nanoparticles (HSNP) is explored under spherical nanoindentation through a combination of experimental, numerical, and theoretical approaches. The effective indentation modulus E(ind) is found to decrease with an increasing number of layers in a nonlinear manner. The indentation force versus penetration depth behavior for multilayer hollow particle arrays is predicted by an approximate analytical model based on the spring stiffness of the individual particles and the multipoint, multiparticle interactions as well as force transmission between the layers. The model is in good agreement with experiments and with detailed finite element simulations. The ability to tune the effective indentation modulus, E(ind), of the multilayer arrays by manipulating particle geometry and layering is revealed through the model, where E(ind) = (0.725m(-3/2) + 0.275)E(mon) and E(mon) is the monolayer modulus and m is number of layers. E(ind) is seen to plateau with increasing m to E(ind_plateau) = 0.275E(mon) and E(mon) scales with (t/R)(2), t being the particle shell thickness and R being the particle radius. The scaling law governing the nonlinear decrease in indentation modulus with an increase in layer number (E(ind) scaling with m(-3/2)) is found to be similar to that governing the indentation modulus of thin solid films E(ind_solid) on a stiff substrate (where E(ind_solid) scales with h(-1.4) and also decreases until reaching a plateau value) which also decreases with an increase in film thickness h. However, the mechanisms underlying this trend for the colloidal array are clearly different, where discrete particle-to-particle interactions govern the colloidal array behavior in contrast to the substrate constraint on deformation, which governs the thickness dependence of the continuous thin film indentation modulus.

  14. High optical switching speed and flexible electrochromic display based on WO3 nanoparticles with ZnO nanorod arrays' supported electrode

    NASA Astrophysics Data System (ADS)

    Wang, Mingjun; Fang, Guojia; Yuan, Longyan; Huang, Huihui; Sun, Zhenhua; Liu, Nishuang; Xia, Shanhong; Zhao, Xingzhong

    2009-05-01

    The electrochromic (EC) property of WO3 nanoparticles grown on vertically self-aligned ZnO nanorods (ZNRs) is reported. An electrochromic character display based on WO3 nanoparticle-modified ZnO nanorod arrays on a flexible substrate has been fabricated and demonstrated. The ZNRs were first synthesized on ZnO-seed-coated In2O3:Sn (ITO) glass (1 cm2 cell) and polyethylene terephthalate (PET) (4 cm2 cell) substrates by a low temperature hydrothermal method, and then amorphous WO3 nanoparticles were grown directly on the surface of the ZNRs by the pulsed laser deposition (PLD) method. The ZNR-based EC device shows high transparence, good electrochromic stability and fast switching speed (4.2 and 4 s for coloration and bleaching, respectively, for a 1 cm2 cell). The good performance of the ZNR electrode-based EC display can be attributed to the large surface area, high crystallinity and good electron transport properties of the ZNR arrays. Its high contrast, fast switching, good memory and flexible characteristics indicate it is a promising candidate for flexible electrochromic displays or electronic paper.

  15. Peptide Modified ZnO Nanoparticles as Gas Sensors Array for Volatile Organic Compounds (VOCs)

    PubMed Central

    Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

    2018-01-01

    In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modeled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modeled demonstrated a nice fitting of modeling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability, and discrimination ability of the array was achieved. PMID:29713626

  16. Peptide Modified ZnO Nanoparticles as Gas Sensors Array for Volatile Organic Compounds (VOCs).

    PubMed

    Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

    2018-01-01

    In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modeled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modeled demonstrated a nice fitting of modeling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability, and discrimination ability of the array was achieved.

  17. Peptide modified ZnO nanoparticles as gas sensors array for volatile organic compounds (VOCs)

    NASA Astrophysics Data System (ADS)

    Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

    2018-04-01

    In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modelled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modelled demonstrated a nice fitting of modelling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability and discrimination ability of the array was achieved.

  18. Experimental implementations of 2D IR spectroscopy through a horizontal pulse shaper design and a focal plane array detector

    PubMed Central

    Ghosh, Ayanjeet; Serrano, Arnaldo L.; Oudenhoven, Tracey A.; Ostrander, Joshua S.; Eklund, Elliot C.; Blair, Alexander F.; Zanni, Martin T.

    2017-01-01

    Aided by advances in optical engineering, two-dimensional infrared spectroscopy (2D IR) has developed into a promising method for probing structural dynamics in biophysics and material science. We report two new advances for 2D IR spectrometers. First, we report a fully reflective and totally horizontal pulse shaper, which significantly simplifies alignment. Second, we demonstrate the applicability of mid-IR focal plane arrays (FPAs) as suitable detectors in 2D IR experiments. FPAs have more pixels than conventional linear arrays and can be used to multiplex optical detection. We simultaneously measure the spectra of a reference beam, which improves the signal-to-noise by a factor of 4; and two additional beams that are orthogonally polarized probe pulses for 2D IR anisotropy experiments. PMID:26907414

  19. Application of X-Y Separable 2-D Array Beamforming for Increased Frame Rate and Energy Efficiency in Handheld Devices

    PubMed Central

    Owen, Kevin; Fuller, Michael I.; Hossack, John A.

    2015-01-01

    Two-dimensional arrays present significant beamforming computational challenges because of their high channel count and data rate. These challenges are even more stringent when incorporating a 2-D transducer array into a battery-powered hand-held device, placing significant demands on power efficiency. Previous work in sonar and ultrasound indicates that 2-D array beamforming can be decomposed into two separable line-array beamforming operations. This has been used in conjunction with frequency-domain phase-based focusing to achieve fast volume imaging. In this paper, we analyze the imaging and computational performance of approximate near-field separable beamforming for high-quality delay-and-sum (DAS) beamforming and for a low-cost, phaserotation-only beamforming method known as direct-sampled in-phase quadrature (DSIQ) beamforming. We show that when high-quality time-delay interpolation is used, separable DAS focusing introduces no noticeable imaging degradation under practical conditions. Similar results for DSIQ focusing are observed. In addition, a slight modification to the DSIQ focusing method greatly increases imaging contrast, making it comparable to that of DAS, despite having a wider main lobe and higher side lobes resulting from the limitations of phase-only time-delay interpolation. Compared with non-separable 2-D imaging, up to a 20-fold increase in frame rate is possible with the separable method. When implemented on a smart-phone-oriented processor to focus data from a 60 × 60 channel array using a 40 × 40 aperture, the frame rate per C-mode volume slice increases from 16 to 255 Hz for DAS, and from 11 to 193 Hz for DSIQ. Energy usage per frame is similarly reduced from 75 to 4.8 mJ/ frame for DAS, and from 107 to 6.3 mJ/frame for DSIQ. We also show that the separable method outperforms 2-D FFT-based focusing by a factor of 1.64 at these data sizes. This data indicates that with the optimal design choices, separable 2-D beamforming can

  20. Dosimetric verification for intensity-modulated arc therapy plans by use of 2D diode array, radiochromic film and radiosensitive polymer gel.

    PubMed

    Hayashi, Naoki; Malmin, Ryan L; Watanabe, Yoichi

    2014-05-01

    Several tools are used for the dosimetric verification of intensity-modulated arc therapy (IMAT) treatment delivery. However, limited information is available for composite on-line evaluation of these tools. The purpose of this study was to evaluate the dosimetric verification of IMAT treatment plans using a 2D diode array detector (2D array), radiochromic film (RCF) and radiosensitive polymer gel dosimeter (RPGD). The specific verification plans were created for IMAT for two prostate cancer patients by use of the clinical treatment plans. Accordingly, the IMAT deliveries were performed with the 2D array on a gantry-mounting device, RCF in a cylindrical acrylic phantom, and the RPGD in two cylindrical phantoms. After the irradiation, the planar dose distributions from the 2D array and the RCFs, and the 3D dose distributions from the RPGD measurements were compared with the calculated dose distributions using the gamma analysis method (3% dose difference and 3-mm distance-to-agreement criterion), dose-dependent dose difference diagrams, dose difference histograms, and isodose distributions. The gamma passing rates of 2D array, RCFs and RPGD for one patient were 99.5%, 96.5% and 93.7%, respectively; the corresponding values for the second patient were 97.5%, 92.6% and 92.9%. Mean percentage differences between the RPGD measured and calculated doses in 3D volumes containing PTVs were -0.29 ± 7.1% and 0.97 ± 7.6% for the two patients, respectively. In conclusion, IMAT prostate plans can be delivered with high accuracy, although the 3D measurements indicated less satisfactory agreement with the treatment plans, mainly due to the dosimetric inaccuracy in low-dose regions of the RPGD measurements.

  1. Fast Confocal Raman Imaging Using a 2-D Multifocal Array for Parallel Hyperspectral Detection.

    PubMed

    Kong, Lingbo; Navas-Moreno, Maria; Chan, James W

    2016-01-19

    We present the development of a novel confocal hyperspectral Raman microscope capable of imaging at speeds up to 100 times faster than conventional point-scan Raman microscopy under high noise conditions. The microscope utilizes scanning galvomirrors to generate a two-dimensional (2-D) multifocal array at the sample plane, generating Raman signals simultaneously at each focus of the array pattern. The signals are combined into a single beam and delivered through a confocal pinhole before being focused through the slit of a spectrometer. To separate the signals from each row of the array, a synchronized scan mirror placed in front of the spectrometer slit positions the Raman signals onto different pixel rows of the detector. We devised an approach to deconvolve the superimposed signals and retrieve the individual spectra at each focal position within a given row. The galvomirrors were programmed to scan different focal arrays following Hadamard encoding patterns. A key feature of the Hadamard detection is the reconstruction of individual spectra with improved signal-to-noise ratio. Using polystyrene beads as test samples, we demonstrated not only that our system images faster than a conventional point-scan method but that it is especially advantageous under noisy conditions, such as when the CCD detector operates at fast read-out rates and high temperatures. This is the first demonstration of multifocal confocal Raman imaging in which parallel spectral detection is implemented along both axes of the CCD detector chip. We envision this novel 2-D multifocal spectral detection technique can be used to develop faster imaging spontaneous Raman microscopes with lower cost detectors.

  2. D-sorbitol-induced phase control of TiO2 nanoparticles and its application for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Shaikh, Shoyebmohamad F.; Mane, Rajaram S.; Min, Byoung Koun; Hwang, Yun Jeong; Joo, Oh-Shim

    2016-02-01

    Using a simple hydrothermal synthesis, the crystal structure of TiO2 nanoparticles was controlled from rutile to anatase using a sugar alcohol, D-sorbitol. Adding small amounts of D-sorbitol to an aqueous TiCl4 solution resulted in changes in the crystal phase, particle size, and surface area by affecting the hydrolysis rate of TiCl4. These changes led to improvements of the solar-to-electrical power conversion efficiency (η) of dye-sensitized solar cells (DSSC) fabricated using these nanoparticles. A postulated reaction mechanism concerning the role of D-sorbitol in the formation of rutile and anatase was proposed. Fourier-transform infrared spectroscopy, 13C NMR spectroscopy, and dynamic light scattering analyses were used to better understand the interaction between the Ti precursor and D-sorbitol. The crystal phase and size of the synthesized TiO2 nanocrystallites as well as photovoltaic performance of the DSSC were examined using X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and photocurrent density-applied voltage spectroscopy measurement techniques. The DSSC fabricated using the anatase TiO2 nanoparticles synthesized in the presence of D-sorbitol, exhibited an enhanced η (6%, 1.5-fold improvement) compared with the device fabricated using the rutile TiO2 synthesized without D-sorbitol.

  3. IMRT plan verification with EBT2 and EBT3 films compared to PTW 2D-ARRAY seven29

    NASA Astrophysics Data System (ADS)

    Hanušová, Tereza; Horáková, Ivana; Koniarová, Irena

    2017-11-01

    The aim of this study was to compare dosimetry with Gafchromic EBT2 and EBT3 films to the ion chamber array PTW seven29 in terms of their performance in clinical IMRT plan verification. A methodology for film processing and calibration was developed. Calibration curves were obtained in MATLAB and in FilmQA Pro. The best calibration curve was then used to calibrate EBT2 and EBT3 films for IMRT plan verification measurements. Films were placed in several coronal planes into an RW3 slab phantom and irradiated with a clinical IMRT plan for prostate and lymph nodes using 18 MV photon beams. Individual fields were tested and irradiated with gantry at 0°. Results were evaluated using gamma analysis with 3%/3 mm criteria in OmniPro I'mRT version 1.7. The same measurements were performed with the ion chamber array PTW seven29 in RW3 slabs (different depths) and in the OCTAVIUS II phantom (isocenter depth only; both original and nominal gantry angles). Results were evaluated in PTW VeriSoft version 3.1 using the same criteria. Altogether, 45 IMRT planes were tested with film and 25 planes with the PTW 2D-ARRAY seven29. Film measuerements showed different results than ion chamber matrix measurements. With PTW 2D-ARRAY seven29, worse results were obtained when the detector was placed into the OCTAVIUS phantom than into the RW3 slab phantom, and the worst pass rates were seen for rotational measurements. EBT2 films showed inconsistent results and could differ significantly for different planes in one field. EBT3 films seemed to give the best results of all the tested configurations.

  4. Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

    PubMed

    Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

    2012-11-30

    A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Enhanced photoelectrochemical performance of TiO2 nanotube arrays with coexisted Pt nanoparticles and Co-Pi cocatalysts

    NASA Astrophysics Data System (ADS)

    Li, Yanfang; Cao, Chang; Xie, Xinxin; Zhang, Li; Lin, Shiwei

    2018-04-01

    Highly-ordered TiO2 nanotube arrays (TNTAs) were prepared by electrochemical anodization. Cobalt-phosphate (Co-Pi) film fabricated by electrodeposition and Pt nanoparticles (Pt NPs) fabricated by photochemical reduction were decorated onto TNTAs to enhance the photoelectrochemical (PEC) performance together. The photocurrent density of the TNTAs/Co-Pi/Pt photoelectrode could reach 0.185 mA/cm2 at 1.23 V versus reversible hydrogen electrode under UV lamp illumination (1 mW/cm2), which is 2.65 times compared to that of the pure TNTAs photoelectrode. Electrochemistry impedance spectroscopy and Mott-Schottky analysis were conducted to explore the reasons for the enhancement of the PEC performance. Pt NPs could promote the reduction of Co(Ⅳ)-oxo intermediate to Co(II) or Co(Ⅲ) which facilitated the charge transfer in the PEC performance. The result provides a promising guideline to design a simple and efficient photoelectrode for the PEC water-splitting system.

  6. h-BN Nanosheets as 2D Substrates to Load 0D Fe3O4 Nanoparticles: A Hybrid Anode Material for Lithium-Ion Batteries.

    PubMed

    Duan, Zhi-Qiang; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying; Zhu, Xiao-Dong

    2016-03-18

    h-BN, as an isoelectronic analogue of graphene, has improved thermal mechanical properties. Moreover, the liquid-phase production of h-BN is greener since harmful oxidants/reductants are unnecessary. Here we report a novel hybrid architecture by employing h-BN nanosheets as 2D substrates to load 0D Fe3O4 nanoparticles, followed by phenol/formol carbonization to form a carbon coating. The resulting carbon-encapsulated h-BN@Fe3O4 hybrid architecture exhibits synergistic interactions: 1) The h-BN nanosheets act as flexible 2D substrates to accommodate the volume change of the Fe3O4 nanoparticles; 2) The Fe3O4 nanoparticles serve as active materials to contribute to a high specific capacity; and 3) The carbon coating not only protects the hybrid architecture from deformation but also keeps the whole electrode highly conductive. The synergistic interactions translate into significantly enhanced electrochemical performances, laying a basis for the development of superior hybrid anode materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Nonlinear chiro-optical amplification by plasmonic nanolens arrays formed via directed assembly of gold nanoparticles.

    PubMed

    Biswas, Sushmita; Liu, Xiaoying; Jarrett, Jeremy W; Brown, Dean; Pustovit, Vitaliy; Urbas, Augustine; Knappenberger, Kenneth L; Nealey, Paul F; Vaia, Richard A

    2015-03-11

    Metal nanoparticle assemblies are promising materials for nanophotonic applications due to novel linear and nonlinear optical properties arising from their plasmon modes. However, scalable fabrication approaches that provide both precision nano- and macroarchitectures, and performance commensurate with design and model predictions, have been limiting. Herein, we demonstrate controlled and efficient nanofocusing of the fundamental and second harmonic frequencies of incident linearly and circularly polarized light using reduced symmetry gold nanoparticle dimers formed by surface-directed assembly of colloidal nanoparticles. Large ordered arrays (>100) of these C∞v heterodimers (ratio of radii R1/R2 = 150 nm/50 nm = 3; gap distance l = 1 ± 0.5 nm) exhibit second harmonic generation and structure-dependent chiro-optic activity with the circular dichroism ratio of individual heterodimers varying less than 20% across the array, demonstrating precision and uniformity at a large scale. These nonlinear optical properties were mediated by interparticle plasmon coupling. Additionally, the versatility of the fabrication is demonstrated on a variety of substrates including flexible polymers. Numerical simulations guide architecture design as well as validating the experimental results, thus confirming the ability to optimize second harmonic yield and induce chiro-optical responses for compact sensors, optical modulators, and tunable light sources by rational design and fabrication of the nanostructures.

  8. Duplex-imprinted nano well arrays for promising nanoparticle assembly

    NASA Astrophysics Data System (ADS)

    Li, Xiangping; Manz, Andreas

    2018-02-01

    A large area nano-duplex-imprint technique is presented in this contribution using natural cicada wings as stamps. The glassy wings of the cicada, which are abundant in nature, exhibit strikingly interesting nanopillar structures over their membrane. This technique, with excellent performance despite the nonplanar surface of the wings, combines both top-down and bottom-up nanofabrication techniques. It transitions micro-nanofabrication from a cleanroom environment to the bench. Two different materials, dicing tape with an acrylic layer and a UV optical adhesive, are used to make replications at the same time, thus achieving duplex imprinting. The promise of a large volume of commercial manufacturing of these nanostructure elements can be envisaged through this contribution to speeding up the fabrication process and achieving a higher throughput. The contact angle of the replicated nanowell arrays before and after oxygen plasma was measured. Gold nanoparticles (50 nm) were used to test how the nanoparticles behaved on the untreated and plasma-treated replica surface. The experiments show that promising nanoparticle self-assembly can be obtained.

  9. FDD Massive MIMO Channel Estimation With Arbitrary 2D-Array Geometry

    NASA Astrophysics Data System (ADS)

    Dai, Jisheng; Liu, An; Lau, Vincent K. N.

    2018-05-01

    This paper addresses the problem of downlink channel estimation in frequency-division duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. The existing methods usually exploit hidden sparsity under a discrete Fourier transform (DFT) basis to estimate the cdownlink channel. However, there are at least two shortcomings of these DFT-based methods: 1) they are applicable to uniform linear arrays (ULAs) only, since the DFT basis requires a special structure of ULAs, and 2) they always suffer from a performance loss due to the leakage of energy over some DFT bins. To deal with the above shortcomings, we introduce an off-grid model for downlink channel sparse representation with arbitrary 2D-array antenna geometry, and propose an efficient sparse Bayesian learning (SBL) approach for the sparse channel recovery and off-grid refinement. The main idea of the proposed off-grid method is to consider the sampled grid points as adjustable parameters. Utilizing an in-exact block majorization-minimization (MM) algorithm, the grid points are refined iteratively to minimize the off-grid gap. Finally, we further extend the solution to uplink-aided channel estimation by exploiting the angular reciprocity between downlink and uplink channels, which brings enhanced recovery performance.

  10. Targeting multiple types of tumors using NKG2D-coated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Ru; Cook, W. James; Zhang, Tong; Sentman, Charles L.

    2014-11-01

    Iron oxide nanoparticles (IONPs) hold great potential for cancer therapy. Actively targeting IONPs to tumor cells can further increase therapeutic efficacy and decrease off-target side effects. To target tumor cells, a natural killer (NK) cell activating receptor, NKG2D, was utilized to develop pan-tumor targeting IONPs. NKG2D ligands are expressed on many tumor types and its ligands are not found on most normal tissues under steady state conditions. The data showed that mouse and human fragment crystallizable (Fc)-fusion NKG2D (Fc-NKG2D) coated IONPs (NKG2D/NPs) can target multiple NKG2D ligand positive tumor types in vitro in a dose dependent manner by magnetic cell sorting. Tumor targeting effect was robust even under a very low tumor cell to normal cell ratio and targeting efficiency correlated with NKG2D ligand expression level on tumor cells. Furthermore, the magnetic separation platform utilized to test NKG2D/NP specificity has the potential to be developed into high throughput screening strategies to identify ideal fusion proteins or antibodies for targeting IONPs. In conclusion, NKG2D/NPs can be used to target multiple tumor types and magnetic separation platform can facilitate the proof-of-concept phase of tumor targeting IONP development.

  11. Gold Nanoparticle Chemiresistor Arrays for Micro-Gas Chromatography Applications

    NASA Astrophysics Data System (ADS)

    Covington, Elizabeth Laura

    Thiolate-monolayer-protected gold nanoparticle (MPN) chemiresistors were studied as the sensing devices for micro-gas chromatography (microGC) systems. Because transport through chemiresistors is dominated by tunneling, they are highly sensitive. In order to improve their limit of detection, their fundamental noise was studied. Chemiresistors exhibit 1/f type noise where noise scales inversely with frequency. Chemiresistor noise was found to scale inversely with MPN film thickness. We lowered the noise prefactor of a 50x60 microm2 chemiresistor by coating a thick rather than monolayer MPN film. Electron beam induced crosslinking (EBIX) of the MPN film slightly reduced chemiresistor noise. A technique for patterning chemiresistor arrays with MPN films using EBIX was developed, and an array with four distinct MPNs was fabricated in an area ˜600 microm 2. This is the smallest chemiresistor array reported to date. Chemiresistors were exposed to vapors and provided differential sensitivities comparable to those from larger uncrosslinked chemiresistors. Chemiresistors were studied to assess their long term stability. Chemiresistors exhibited decreases in resistance over time that is likely caused by loss of MPN ligands. Temperature dependent current-voltage measurements verified the resistance change was not due to changes in the size of the MPN core. While resistance could change by orders of magnitude, vapor sensitivity did not show significant changes. Heating increased the change in resistance, but chemiresistors remained responsive after being held at 80°C for a cumulative 400 hours. It was unknown whether tunneling in the MPN film is through the highest unoccupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO). A new technique was explored to distinguish tunneling through the HOMO and LUMO by measuring the induced thermoelectric voltage caused by a temperature difference across the MPN film. For integration into a microGC system, we

  12. A 2D silicon detector array for quality assurance in small field dosimetry: DUO.

    PubMed

    Shukaili, Khalsa Al; Petasecca, Marco; Newall, Matthew; Espinoza, Anthony; Perevertaylo, Vladimir L; Corde, Stéphanie; Lerch, Michael; Rosenfeld, Anatoly B

    2017-02-01

    Nowadays, there are many different applications that use small fields in radiotherapy treatments. The dosimetry of small radiation fields is not trivial due to the problems associated with lateral disequilibrium and source occlusion and requires reliable quality assurance (QA). Ideally such a QA tool should provide high spatial resolution, minimal beam perturbation and real time fast measurements. Many different types of silicon diode arrays are used for QA in radiotherapy; however, their application in small filed dosimetry is limited, in part, due to a lack of spatial resolution. The Center of Medical Radiation Physics (CMRP) has developed a new generation of a monolithic silicon diode array detector that will be useful for small field dosimetry in SRS/SRT. The objective of this study is to characterize a monolithic silicon diode array designed for dosimetry QA in SRS/SRT named DUO that is arranged as two orthogonal 1D arrays with 0.2 mm pitch. DUO is two orthogonal 1D silicon detector arrays in a monolithic crystal. Each orthogonal array contains 253 small pixels with size 0.04 × 0.8 mm 2 and three central pixels are with a size of 0.18 × 0.18 mm 2 each. The detector pitch is 0.2 mm and total active area is 52 × 52 mm 2 . The response of the DUO silicon detector was characterized in terms of dose per pulse, percentage depth dose, and spatial resolution in a radiation field incorporating high gradients. Beam profile of small fields and output factors measured on a Varian 2100EX LINAC in a 6 MV radiation fields of square dimensions and sized from 0.5 × 0.5 cm 2 to 5 × 5 cm 2 . The DUO response was compared under the same conditions with EBT3 films and an ionization chamber. The DUO detector shows a dose per pulse dependence of 5% for a range of dose rates from 2.7 × 10 -4 to 1.2 × 10 -4 Gy/pulse and 23% when the rate is further reduced to 2.8 × 10 -5 Gy/pulse. The percentage depth dose measured to 25 cm depth in solid water phantom beyond the surface and

  13. Array-based sensing using nanoparticles: an alternative approach for cancer diagnostics.

    PubMed

    Le, Ngoc D B; Yazdani, Mahdieh; Rotello, Vincent M

    2014-07-01

    Array-based sensing using nanoparticles (NPs) provides an attractive alternative to specific biomarker-focused strategies for cancer diagnosis. The physical and chemical properties of NPs provide both the recognition and transduction capabilities required for biosensing. Array-based sensors utilize a combined response from the interactions between sensors and analytes to generate a distinct pattern (fingerprint) for each analyte. These interactions can be the result of either the combination of multiple specific biomarker recognition (specific binding) or multiple selective binding responses, known as chemical nose sensing. The versatility of the latter array-based sensing using NPs can facilitate the development of new personalized diagnostic methodologies in cancer diagnostics, a necessary evolution in the current healthcare system to better provide personalized treatments. This review will describe the basic principle of array-based sensors, along with providing examples of both invasive and noninvasive samples used in cancer diagnosis.

  14. Optical spectroscopy of arrays of Ag-Au nanoparticles obtained by vacuum-thermal evaporation

    NASA Astrophysics Data System (ADS)

    Gromov, D. G.; Mel'nikov, I. V.; Savitskii, A. I.; Trifonov, A. Yu.; Redichev, E. N.; Astapenko, V. A.

    2017-03-01

    The possibility of creating irregular arrays of bimetallic Ag-Au nanoparticles is investigated. The ability to manipulate their optical properties based on the simple engineering processes of thermal spraying followed by low-temperature annealing is demonstrated.

  15. Directed-assembly of ordered nanoparticle arrays exploiting multiple adsorption mechanisms on a self-assembling biological template

    NASA Astrophysics Data System (ADS)

    Shindel, Matthew M.

    Developing processes to fabricate inorganic architectures with designer functionalities at increasingly minute length-scales is of chief concern in the fields of nanotechnology and nanoscience. This enterprise requires assembly mechanisms with the capacity to tailor both the spatial arrangement and material composition of a system's constituent building blocks. To this end, significant advances can be made by turning to biology, as the natural world has evolved the ability to generate intricate nanostructures, which can potentially be employed as templates for inorganic nanosystems. We explore this biotemplating methodology using two-dimensional streptavidin crystals, investigating the ability of the protein lattice to direct the assembly of ordered metallic nanoparticle arrays. We demonstrate that the adsorption of nanoparticles on the protein monolayer can be induced through both electrostatic and molecular recognition (ligand-receptor) interactions. Furthermore, the dynamics of adsorption can be modulated through both environmental factors (e.g. pH), and by tailoring particle surface chemistry. When the characteristic nanoparticle size is on the order of the biotemplate's unit-cell dimension, electrostatically-mediated adsorption occurs in a site-specific manner. The nanoparticles exhibit a pronounced preference for adhering to the areas between protein molecules. The two-dimensional structure of the resultant nanoparticle ensemble consequently conforms to that of the underlying protein crystal. Through theoretical calculations, simulation and experiment, we show that interparticle spacing in the templated array is influenced by the screened-coulombic repulsion between particles, and can thus be tuned by controlling ionic strength during deposition. Templating ordered nanoparticle arrays via ligand-receptor mediated adsorption, and the constrained growth of metallic nanoparticles directly on the protein lattice from ionic precursors are also examined. Overall

  16. Comparison of different sets of array configurations for multichannel 2D ERT acquisition

    NASA Astrophysics Data System (ADS)

    Martorana, R.; Capizzi, P.; D'Alessandro, A.; Luzio, D.

    2017-02-01

    Traditional electrode arrays such Wenner-Schlumberger or dipole-dipole are still widely used thanks to their well-known properties but the array configurations are generally not optimized for multi-channel resistivity measures. Synthetic datasets relating to four different arrays, dipole-dipole (DD), pole-dipole (PD), Wenner-Schlumberger (WS) and a modified version of multiple gradient (MG), have been made for a systematic comparison between 2D resistivity models and their inverted images. Different sets of array configurations generated from simple combinations of geometric parameters (potential dipole lengths and dipole separation factors) were tested with synthetic and field data sets, even considering the influence of errors and the acquisition velocity. The purpose is to establish array configurations capable to provide reliable results but, at the same time, not involving excessive survey costs, even linked to the acquiring time and therefore to the number of current dipoles used. For DD, PD and WS arrays a progression of different datasets were considered increasing the number of current dipoles trying to get about the same amount of measures. A multi-coverage MG array configuration is proposed by increasing the lateral coverage and so the number of current dipoles. Noise simulating errors both on the electrode positions and on the electric potential was added. The array configurations have been tested on field data acquired in the landfill site of Bellolampo (Palermo, Italy), to detect and locate the leachate plumes and to identify the HDPE bottom of the landfill. The inversion results were compared using a quantitative analysis of data misfit, relative model resolution and model misfit. The results show that the trends of the first two parameters are linked on the array configuration and that a cumulative analysis of these parameters can help to choose the best array configuration in order to obtain a good resolution and reliability of a survey, according

  17. Fabrication of disposable topographic silicon oxide from sawtoothed patterns: control of arrays of gold nanoparticles.

    PubMed

    Cho, Heesook; Yoo, Hana; Park, Soojin

    2010-05-18

    Disposable topographic silicon oxide patterns were fabricated from polymeric replicas of sawtoothed glass surfaces, spin-coating of poly(dimethylsiloxane) (PDMS) thin films, and thermal annealing at certain temperature and followed by oxygen plasma treatment of the thin PDMS layer. A simple imprinting process was used to fabricate the replicated PDMS and PS patterns from sawtoothed glass surfaces. Next, thin layers of PDMS films having different thicknesses were spin-coated onto the sawtoothed PS surfaces and annealed at 60 degrees C to be drawn the PDMS into the valley of the sawtoothed PS surfaces, followed by oxygen plasma treatment to fabricate topographic silicon oxide patterns. By control of the thickness of PDMS layers, silicon oxide patterns having various line widths were fabricated. The silicon oxide topographic patterns were used to direct the self-assembly of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer thin films via solvent annealing process. A highly ordered PS-b-P2VP micellar structure was used to let gold precursor complex with P2VP chains, and followed by oxygen plasma treatment. When the PS-b-P2VP thin films containing gold salts were exposed to oxygen plasma environments, gold salts were reduced to pure gold nanoparticles without changing high degree of lateral order, while polymers were completely degraded. As the width of trough and crest in topographic patterns increases, the number of gold arrays and size of gold nanoparticles are tuned. In the final step, the silicon oxide topographic patterns were selectively removed by wet etching process without changing the arrays of gold nanoparticles.

  18. Silica-sandwiched Au nanoparticle arrays by a soft PE-CVD/RF sputtering approach

    NASA Astrophysics Data System (ADS)

    Barreca, Davide; Gasparotto, Alberto; Maccato, Chiara; Tondello, Eugenio

    2008-06-01

    This work is focused on the development of an innovative synthetic route to SiO2-sandwiched Au nanoparticle arrays. The adopted strategy consists of: (i) the radio frequency sputtering of gold on thermally oxidized Si(100) and silica substrates from Ar plasmas; (ii) the plasma enhanced chemical vapor deposition of a SiO2 overlayer using tetramethoxysilane as precursor from Ar-O2 plasmas. A common feature of both preparative stages is the use of very soft processing conditions at temperatures close to room temperature, in order to tailor the Au nanoparticle morphology and to preserve it upon SiO2 coverage. In situ monitoring of gold deposition was accomplished by means of laser reflection interferometry. Valuable information on the system morphology before and after SiO2 coverage was provided by field emission-scanning electron microscopy for samples with different Au content. Additional important information on the system chemical composition, structure and optical response was gained by the combined use of x-ray photoelectron spectroscopy, glancing incidence x-ray diffraction and UV-visible absorption spectroscopy. The results obtained highlight the formation of high-purity SiO2/Au/SiO2-sandwiched stacks, in which the gold content and distribution, as well as the nanoparticle morphology, could be tailored by the sole variation of the sputtering time, without any further ex situ treatment.

  19. A facile one-step synthesis of Mn{sub 3}O{sub 4} nanoparticles-decorated TiO{sub 2} nanotube arrays as high performance electrode for supercapacitors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Jianfang; Wang, Yan; Key Laboratory of Advance Functional Materials and Devices of Anhui Province, Hefei 230009

    Via a facile one-step chemical bath deposition route, homogeneously dispersed Mn{sub 3}O{sub 4} nanoparticles have been successfully deposited onto the inner surface of TiO{sub 2} nanotube arrays (TNAs). The content and size of Mn{sub 3}O{sub 4} can be controlled by changing the deposition time. Field emission scanning electron microscopy and transmission electron microscopy analysis reveal the morphologies structures of Mn{sub 3}O{sub 4}/TNAs composites. The crystal-line structures are characterized by the X-ray diffraction patterns and Raman spectra. X-ray photoelectron spectroscopy further confirms the valence states of the sample elements. The electrochemical properties of Mn{sub 3}O{sub 4}/TNAs electrodes are systematically investigated bymore » the combine use of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The resulting Mn{sub 3}O{sub 4}/TNAs electrode prepared by deposition time of 3 h shows the highest specific capacitance of 570 F g{sup −1} at a current density of 1 A g{sup −1}. And it also shows an excellent long-term cycling stability at a current density of 5 A g{sup −1}, which remaining 91.8% of the initial capacitance after 2000 cycles. Thus this kind of Mn{sub 3}O{sub 4} nanoparticles decorated TNAs may be considered as an alternative promising candidate for high performance supercapacitor electrodes. - Graphical abstract: Mn{sub 3}O{sub 4} nanoparticles have been uniformly deposited onto the inner surfaces of TiO{sub 2} nanotube arrays through a facile one-step chemical bath deposition method. As electrodes for supercapacitors, they exhibit a relatively high specific capacity and excellent cycling stability. - Highlights: • Mn{sub 3}O{sub 4} nanoparticles have been deposited onto TiO{sub 2} nanotube arrays by chemical bath deposition. • The Mn{sub 3}O{sub 4}/TNAs exhibits a highest specific capacitance of 570 F g{sup –1} at a current density of 1 A g{sup –1}. • The Mn{sub 3}O{sub 4

  20. Synergism of Dewetting and Self-Wrinkling To Create Two-Dimensional Ordered Arrays of Functional Microspheres.

    PubMed

    Han, Xue; Hou, Jing; Xie, Jixun; Yin, Jian; Tong, Yi; Lu, Conghua; Möhwald, Helmuth

    2016-06-29

    Here we report a simple, novel, yet robust nonlithographic method for the controlled fabrication of two-dimensional (2-D) ordered arrays of polyethylene glycol (PEG) microspheres. It is based on the synergistic combination of two bottom-up processes enabling periodic structure formation for the first time: dewetting and the mechanical wrinkle formation. The deterministic dewetting results from the hydrophilic polymer PEG on an incompatible polystyrene (PS) film bound to a polydimethylsiloxane (PDMS) substrate, which is directed both by a wrinkled template and by the template-directed in-situ self-wrinkling PS/PDMS substrate. Two strategies have been introduced to achieve synergism to enhance the 2-D ordering, i.e., employing 2-D in-situ self-wrinkling substrates and boundary conditions. As a result, we achieve highly ordered 2-D arrays of PEG microspheres with desired self-organized microstructures, such as the array location (e.g., selectively on the crest/in the valley of the wrinkles), diameter, spacing of the microspheres, and array direction. Additionally, the coordination of PEG with HAuCl4 is utilized to fabricate 2-D ordered arrays of functional PEG-HAuCl4 composite microspheres, which are further converted into different Au nanoparticle arrays. This simple versatile combined strategy could be extended to fabricate highly ordered 2-D arrays of other functional materials and achieve desirable properties and functionalities.

  1. Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation

    DOE PAGES

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; ...

    2014-10-19

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor phase synthesis. Here, we demonstrate a new route to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe 2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substratemore » by pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (~ 100 m lateral sizes) of GaSe and MoSe 2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This novel PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area, metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.« less

  2. Multienzyme-nanoparticles amplification for sensitive virus genotyping in microfluidic microbeads array using Au nanoparticle probes and quantum dots as labels.

    PubMed

    Zhang, He; Liu, Lian; Li, Cheuk-Wing; Fu, Huayang; Chen, Yao; Yang, Mengsu

    2011-11-15

    A novel microfluidic device with microbeads array was developed and sensitive genotyping of human papillomavirus was demonstrated using a multiple-enzyme labeled oligonucleotide-Au nanoparticle bioconjugate as the detection tool. This method utilizes microbeads as sensing platform that was functionalized with the capture probes and modified electron rich proteins, and uses the horseradish peroxidase (HRP)-functionalized gold nanoparticles as label with a secondary DNA probe. The functionalized microbeads were independently introduced into the arrayed chambers using the loading chip slab. A single channel was used to generate weir structures to confine the microbeads and make the beads array accessible by microfluidics. Through "sandwich" hybridization, the enzyme-functionalized Au nanoparticles labels were brought close to the surface of microbeads. The oxidation of biotin-tyramine by hydrogen peroxide resulted in the deposition of multiple biotin moieties onto the surface of beads. This deposition is markedly increased in the presence of immobilized electron rich proteins. Streptavidin-labeled quantum dots were then allowed to bind to the deposited biotin moieties and displayed the signal. Enhanced detection sensitivity was achieved where the large surface area of Au nanoparticle carriers increased the amount HRP bound per sandwiched hybridization. The on-chip genotyping method could discriminate as low as 1fmol/L (10zmol/chip, SNR>3) synthesized HPV oligonucleotides DNA. The chip-based signal enhancement of the amplified assay resulted in 1000 times higher sensitivity than that of off-chip test. In addition, this on-chip format could discriminate and genotype 10copies/μL HPV genomic DNA using the PCR products. These results demonstrated that this on-chip approach can achieve highly sensitive detection and genotyping of target DNA and can be further developed for detection of disease-related biomolecules at the lowest level at their earliest incidence. Copyright

  3. Wideband aperture array using RF channelizers and massively parallel digital 2D IIR filterbank

    NASA Astrophysics Data System (ADS)

    Sengupta, Arindam; Madanayake, Arjuna; Gómez-García, Roberto; Engeberg, Erik D.

    2014-05-01

    Wideband receive-mode beamforming applications in wireless location, electronically-scanned antennas for radar, RF sensing, microwave imaging and wireless communications require digital aperture arrays that offer a relatively constant far-field beam over several octaves of bandwidth. Several beamforming schemes including the well-known true time-delay and the phased array beamformers have been realized using either finite impulse response (FIR) or fast Fourier transform (FFT) digital filter-sum based techniques. These beamforming algorithms offer the desired selectivity at the cost of a high computational complexity and frequency-dependant far-field array patterns. A novel approach to receiver beamforming is the use of massively parallel 2-D infinite impulse response (IIR) fan filterbanks for the synthesis of relatively frequency independent RF beams at an order of magnitude lower multiplier complexity compared to FFT or FIR filter based conventional algorithms. The 2-D IIR filterbanks demand fast digital processing that can support several octaves of RF bandwidth, fast analog-to-digital converters (ADCs) for RF-to-bits type direct conversion of wideband antenna element signals. Fast digital implementation platforms that can realize high-precision recursive filter structures necessary for real-time beamforming, at RF radio bandwidths, are also desired. We propose a novel technique that combines a passive RF channelizer, multichannel ADC technology, and single-phase massively parallel 2-D IIR digital fan filterbanks, realized at low complexity using FPGA and/or ASIC technology. There exists native support for a larger bandwidth than the maximum clock frequency of the digital implementation technology. We also strive to achieve More-than-Moore throughput by processing a wideband RF signal having content with N-fold (B = N Fclk/2) bandwidth compared to the maximum clock frequency Fclk Hz of the digital VLSI platform under consideration. Such increase in bandwidth is

  4. Wafer-Scale Hierarchical Nanopillar Arrays Based on Au Masks and Reactive Ion Etching for Effective 3D SERS Substrate.

    PubMed

    Men, Dandan; Wu, Yingyi; Wang, Chu; Xiang, Junhuai; Yang, Ganlan; Wan, Changjun; Zhang, Honghua

    2018-02-04

    Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO₂ nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO₂ nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO₂ nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO₂ nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density "hotspots" derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods.

  5. Electrophoretic build-up of multi nanoparticle array for a highly sensitive immunoassay

    PubMed Central

    Han, Jin-Hee; Kim, Hee-Joo; Sudheendra, L.; Hass, Elizabeth A.; Gee, Shirley J.; Hammock, Bruce D.; Kennedy, Ian M.

    2012-01-01

    One of the challenges in shrinking immunoassays to smaller sizes is to immobilize the biological molecules to nanometer-scaled spots. To overcome this complication, we have employed a particle-based immunoassay to create a nanostructured platform with a regular array of sensing elements. The technique makes use of an electrophoretic particle entrapment system (EPES) to immobilize nanoparticles that are coated with biological reagents into wells using a very small trapping potential. To provide useful information for controlling the trapping force and optimal design of the nanoarray, electrophoretic trapping of a nanoparticle was modeled numerically. The trapping efficiency, defined as the fraction of wells occupied by a single particle, was 91%. The performance of the array was demonstrated with a competitive immunoassay for a small molecule analyte, 3-phenoxybenzoic acid (214.2 g mole−1). The limit of detection determined with a basic fluorescence microscope was 0.006 μg l−1 (30 pM); this represented a sixteen-fold improvement in sensitivity compared to a standard 96-well plate-based ELISA; the improvement was attributed to the small size of the sample volume and the presence of light diffraction among factors unique to this structure. The EPES/nanoarray system promises to offer a new standard in applications that require portable, point-of-care and real-time monitoring with high sensitivity. PMID:23021853

  6. Array servo scanning micro EDM of 3D micro cavities

    NASA Astrophysics Data System (ADS)

    Tong, Hao; Li, Yong; Yi, Futing

    2011-05-01

    Micro electro discharge machining (Micro EDM) is a non-traditional processing technology with the special advantages of low set-up cost and few cutting force in machining any conductive materials regardless of their hardness. As well known, die-sinking EDM is unsuitable for machining the complex 3D micro cavity less than 1mm due to the high-priced fabrication of 3D microelectrode itself and its serous wear during EDM process. In our former study, a servo scanning 3D micro-EDM (3D SSMEDM) method was put forward, and our experiments showed it was available to fabricate complex 3D micro-cavities. In this study, in order to improve machining efficiency and consistency accuracy for array 3D micro-cavities, an array-servo-scanning 3D micro EDM (3D ASSMEDM) method is presented considering the complementary advantages of the 3D SSMEDM and the array micro electrodes with simple cross-section. During 3D ASSMEDM process, the array cavities designed by CAD / CAM system can be batch-manufactured by servo scanning layer by layer using array-rod-like micro tool electrodes, and the axial wear of the array electrodes is compensated in real time by keeping discharge gap. To verify the effectiveness of the 3D ASSMEDM, the array-triangle-micro cavities (side length 630 μm) are batch-manufactured on P-doped silicon by applying the array-micro-electrodes with square-cross-section fabricated by LIGA process. Our exploratory experiment shows that the 3D ASSMEDM provides a feasible approach for the batch-manufacture of 3D array-micro-cavities of conductive materials.

  7. Graphite-like carbon nitride coupled with tiny Bi2S3 nanoparticles as 2D/0D heterojunction with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zhu, Chengzhang; Gong, Tingting; Xian, Qiming; Xie, Jimin

    2018-06-01

    Novel well-dispersed tiny Bi2S3 nanoparticles (NPs) with an average sizes of approximately 16.2 nm were used to decorate layered g-C3N4 nanosheets (NSs), with the purpose of constructing highly efficient 0D/2D heterojunction photocatalyst by a simple hydrothermal method in one step. The fabricated Bi2S3/g-C3N4 heterostructures exhibited superior visible-light-driven photocatalytic activity toward methyl orange (MO) degradation in contrast to that of individual Bi2S3 and g-C3N4, which could be mainly ascribed to the synergistic effect of the tiny size effect of 0D Bi2S3 NPs and 2D g-C3N4 NSs, the matched energy level positions, and the abundant coupling heterointerfaces between two moieties. More importantly, the photodegradation of methylene blue (MB), rhodamine B (RhB) and colorless tetracycline (TC), ciprofloxacin (CIP) further revealed the broad-spectrum photodegradation capacities of the heterojunction materials. The possible photoinduced charge transfer and pollutant degradation process over Bi2S3/g-C3N4 heterojunctions under visible-light irradiation were proposed. This work may provide a platform for constructing new visible light 0D/2D intimate contact heterostructures with stable and efficient photocatalytic performance.

  8. Development of a Magnetic Nanoparticle Susceptibility Magnitude Imaging Array

    PubMed Central

    Ficko, Bradley W.; Nadar, Priyanka M.; Hoopes, P. Jack; Diamond, Solomon G.

    2014-01-01

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over 5 dilutions (R2 > 0.98, p <0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 nm and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe/ml mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution. PMID:24504184

  9. 2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

    2014-05-01

    Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

  10. Cu-PDC-bpa solid coordination frameworks (PDC=2,5-pyrindinedicarboxylate; bpa=1,2-DI(4-pyridil)ethane)): 2D and 3D structural flexibility producing a 3-c herringbone array next to ideal

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Llano-Tomé, Francisco, E-mail: francisco.llano@ehu.eus; Bazán, Begoña, E-mail: bego.bazan@ehu.eus; BCMaterials Parque Tecnológico de Zamudio, Ibaizabal Bidea, Edificio 500–Planta 1, 48160 Derio

    Combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce solid coordination frameworks (SCF) which are crystalline materials based on connections between metal ions through organic ligands. In this context, this work is focused on two novel Cu{sup II}-based SCFs exhibiting PDC (2,5-pyridinedicarboxylate) and bpa (1,2-di(4-pyridyl)ethane), being the first structures reported in literature containing both ligands. Chemical formula are [Cu{sub 2}[(PDC){sub 2}(bpa)(H{sub 2}O){sub 2}]·3H{sub 2}O·DMF (1), and [Cu{sub 2}(PDC){sub 2}(bpa)(H{sub 2}O){sub 2}]·7H{sub 2}O (2), where DMF is dimethylformamide. Compounds 1 and 2 have been characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric (TG) analysis,more » differential thermal analysis (DTA) and dielectric measurements. The crystallographic analysis revealed that compounds 1 and 2 can be described as herringbone-type layers formed by helicoidal Cu-PDC-Cu chains connected through bpa ligands. Solvent molecules are crystallized between the layers, providing the inter-layer connections through hydrogen bonds. Differences between both compounds are attributable to the flexibility of bpa (in 2D) as well as to the 3D packing of the layers which is solvent dependent. This fact results in the fact that compound 2 is the most regular 3-c herringbone array reported so far. The structural dynamism of these networks is responsible for the crystalline to-amorphous to-crystalline (CAC) transformation from compound 1 to compound 2. Crystallochemical features for both compounds have also been studied and compared to similar 3-connected herringbone-arrays. - Graphical abstract: Cu-PDC-bpa 3-c herringbone arrays. - Highlights: • The most ideal herringbone array reported so far is a Cu-PDC-bpa SCF. • Conformational freedom of bpa results in 2D and 3D flexibility of the SCFs. • The flexibility of the SCFs is related to a phase transformation.

  11. Fabrication of highly ordered 2D metallic arrays with disc-in-hole binary nanostructures via a newly developed nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Yang, Xi; Guo, Wei; Wang, Xixi; Liao, Mingdun; Gao, Pingqi; Ye, Jichun

    2017-11-01

    2D metallic arrays with binary nanostructures derived from a nanosphere lithography (NSL) method have been rarely reported. Here, we demonstrate a novel NSL strategy to fabricate highly ordered 2D gold arrays with disc-in-hole binary (DIHB) nanostructures in large scale by employing a sacrificing layer combined with a three-step lift-off process. The structural parameters of the resultant DIHB arrays, such as periodicity, hole diameter, disc diameter and thicknesses can be facilely controlled by tuning the nanospheres size, etching condition, deposition angle and duration, respectively. Due to the intimate interactions between two subcomponents, the DIHB arrays exhibit both an extraordinary high surface-enhanced Raman scattering enhancement factor up to 5 × 108 and a low sheet resistance down to 1.7 Ω/sq. Moreover, the DIHB array can also be used as a metal catalyzed chemical etching catalytic pattern to create vertically-aligned Si nano-tube arrays for anti-reflectance application. This strategy provides a universal route for synthesizing other diverse binary nanostructures with controlled morphology, and thus expands the applications of the NSL to prepare ordered nanostructures with multi-function.

  12. Accelerated short-TE 3D proton echo-planar spectroscopic imaging using 2D-SENSE with a 32-channel array coil.

    PubMed

    Otazo, Ricardo; Tsai, Shang-Yueh; Lin, Fa-Hsuan; Posse, Stefan

    2007-12-01

    MR spectroscopic imaging (MRSI) with whole brain coverage in clinically feasible acquisition times still remains a major challenge. A combination of MRSI with parallel imaging has shown promise to reduce the long encoding times and 2D acceleration with a large array coil is expected to provide high acceleration capability. In this work a very high-speed method for 3D-MRSI based on the combination of proton echo planar spectroscopic imaging (PEPSI) with regularized 2D-SENSE reconstruction is developed. Regularization was performed by constraining the singular value decomposition of the encoding matrix to reduce the effect of low-value and overlapped coil sensitivities. The effects of spectral heterogeneity and discontinuities in coil sensitivity across the spectroscopic voxels were minimized by unaliasing the point spread function. As a result the contamination from extracranial lipids was reduced 1.6-fold on average compared to standard SENSE. We show that the acquisition of short-TE (15 ms) 3D-PEPSI at 3 T with a 32 x 32 x 8 spatial matrix using a 32-channel array coil can be accelerated 8-fold (R = 4 x 2) along y-z to achieve a minimum acquisition time of 1 min. Maps of the concentrations of N-acetyl-aspartate, creatine, choline, and glutamate were obtained with moderate reduction in spatial-spectral quality. The short acquisition time makes the method suitable for volumetric metabolite mapping in clinical studies. (c) 2007 Wiley-Liss, Inc.

  13. Modulation of physiological responses with TiO2 nano-particle in Azolla pinnata R.Br. under 2,4-D toxicity.

    PubMed

    De, Arnab Kumar; Ghosh, Arijit; Debnath, Subhas Chandra; Sarkar, Bipul; Saha, Indraneel; Adak, Malay Kumar

    2018-06-05

    The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO 2 nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO 2 -NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO 2 -NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO 2 -NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid-nitrate pool, but no changes with glutamine synthase activity with TiO 2 -NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO 2 -NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO 2 supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO 2 -NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation.

  14. Cross-linked hierarchical arrays of Ni2P nanoflakes prepared via directional phosphorization and their applications for advanced alkaline batteries

    NASA Astrophysics Data System (ADS)

    Mai, Yong-jin; Xia, Xinhui; Jie, Xiao-hua

    2017-11-01

    In this work, we report a facile directional phosphorization method for construction of hierarchical cross-linked Ni2P arrays, which show a multileveled porous architecture. The basic building blocks are numerous nanoflakes with thicknesses of 15-20 nm, which are self-assembled with each other forming the primary porous mushroom-like structure with 1-3 μm. Impressively, the 3D porous channels run through the whole Ni2P arrays. The secondary nanoflakes consist of interconnected nanoparticles of 10-30 nm and lots of nanopores of 10-50 nm. The electrochemical performance of the as-prepared Ni2P arrays is investigated as cathode of alkaline batteries and demonstrated with higher capacities (127 mAhh g-1 at 2.5 A g-1) and better high-rate cycling stability (123 mAhh g-1 2.5 A g-1 after 9000 cycles) than the preformed Ni(OH)2 arrays counterparts (80 mAhh g-1 2.5 A g-1 and 66 mAhh g-1 after 9000 cycles). The enhanced performance is mainly due to the improved surface area & porosity as well as reinforced electrical conductivity.

  15. Quantum simulation of 2D topological physics in a 1D array of optical cavities

    PubMed Central

    Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei

    2015-01-01

    Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration. PMID:26145177

  16. Quantum simulation of 2D topological physics in a 1D array of optical cavities.

    PubMed

    Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei

    2015-07-06

    Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration.

  17. Noninvasive noble metal nanoparticle arrays for surface-enhanced Raman spectroscopy of proteins

    NASA Astrophysics Data System (ADS)

    Inya-Agha, Obianuju; Forster, Robert J.; Keyes, Tia E.

    2007-02-01

    Noble metal nanoparticles arrays are well established substrates for surface enhanced Raman spectroscopy (SERS). Their ability to enhance optical fields is based on the interaction of their surface valence electrons with incident electromagnetic radiation. In the array configuration, noble metal nanoparticles have been used to produce SER spectral enhancements of up to 10 8 orders of magnitude, making them useful for the trace analysis of physiologically relevant analytes such as proteins and peptides. Electrostatic interactions between proteins and metal surfaces result in the preferential adsorption of positively charged protein domains onto metal surfaces. This preferential interaction has the effect of disrupting the native conformation of the protein fold, with a concomitant loss of protein function. A major historic advantage of Raman microspectroscopy has been is its non-invasive nature; protein denaturation on the metal surfaces required for SER spectroscopy renders it a much more invasive technique. Further, part of the analytical power of Raman spectroscopy lies in its use as a secondary conformation probe. The protein structural loss which occurs on the metal surface results in secondary conformation readings which are not true to the actual native state of the analyte. This work presents a method for chemical fabrication of noble metal SERS arrays with surface immobilized layers which can protect protein native conformation without excessively mitigating the electromagnetic enhancements of spectra. Peptide analytes are used as model systems for proteins. Raman spectra of alpha lactalbumin on surfaces and when immobilized on these novel arrays are compared. We discuss the ability of the surface layer to protect protein structure whilst improving signal intensity.

  18. 2D Metal-Organic Frameworks Derived Nanocarbon Arrays for Substrate Enhancement in Flexible Supercapacitors.

    PubMed

    Liu, Ximeng; Guan, Cao; Hu, Yating; Zhang, Lei; Elshahawy, Abdelnaby M; Wang, John

    2017-10-27

    Direct assembling of active materials on carbon cloth (CC) is a promising way to achieve flexible electrodes for energy storage. However, the overall surface area and electrical conductivity of such electrodes are usually limited. Herein, 2D metal-organic framework derived nanocarbon nanowall (MOFC) arrays are successfully developed on carbon cloth by a facile solution + carbonization process. Upon growth of the MOFC arrays, the sites for growth of the active materials are greatly increased, and the equivalent series resistance is decreased, which contribute to the enhancement of the bare CC substrate. After decorating ultrathin flakes of MnO 2 and Bi 2 O 3 on the flexible CC/MOFC substrate, the hierarchical electrode materials show an abrupt improvement of areal capacitances by around 50% and 100%, respectively, compared to those of the active materials on pristine carbon cloth. A flexible supercapacitor can be further assembled using two hierarchical electrodes, which demonstrates an energy density of 124.8 µWh cm -2 at the power density of 2.55 mW cm -2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

    PubMed

    Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

    2014-02-01

    One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. RIE-based Pattern Transfer Using Nanoparticle Arrays as Etch Masks

    NASA Astrophysics Data System (ADS)

    Hogg, Chip; Majetich, Sara A.; Bain, James A.

    2009-03-01

    Nanomasking is used to transfer the pattern of a self-assembled array of nanoparticles into an underlying thin film, for potential use as bit-patterned media. We have used this process to investigate the limits of pattern transfer, as a function of gap size in the pattern. Reactive Ion Etching (RIE) is our chosen process, since the gaseous reaction products and high chemical selectivity are ideal features for etching very small gaps. Interstitial surfactant is removed with an O2 plasma, allowing the etchants to penetrate between the particles. Their pattern is transferred into an intermediate SiO2 mask using a CH4-based RIE. This patterned SiO2 layer is finally used as a mask for the MeOH-based RIE which patterns the magnetic film. We present cross-sectional TEM characterization of the etch profiles, as well as magnetic characterization of the film before and after patterning.

  1. 2D-3D switchable display based on a passive polymeric lenticular lens array and electrically suppressed ferroelectric liquid crystal.

    PubMed

    Shi, Liangyu; Srivastava, Abhishek Kumar; Wai Tam, Alwin Ming; Chigrinov, Vladimir Grigorievich; Kwok, Hoi Sing

    2017-09-01

    We reveal a 2D-3D switchable lens unit that is based on a polarization-sensitive microlens array and a polarization selector unit made of an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) cell. The ESHFLCs offer a high contrast ratio (∼10k∶1) between the crossed polarizers at a low applied electric field (∼1.7  V/μm) with a small switching time (<50  μs). A special driving scheme, to switch between a 2D and 3D mode, has been developed to avoid unwanted issues related to DC accumulation in the ferroelectric liquid crystal without affecting its optical quality. The proposed lens unit is characterized by low power consumption, ultrafast response, and 3D crosstalk <5%, and can therefore find application in TVs, cell phones, etc.

  2. Decrease of reactive oxygen species-related biomarkers in the tissue-mimic 3D spheroid culture of human lung cells exposed to zinc oxide nanoparticles.

    PubMed

    Kim, Eunjoo; Jeon, Won Bae; Kim, Soonhyun; Lee, Soo-Keun

    2014-05-01

    Common 2-dimensional (2D) cell cultures do not adequately represent cell-cell and cell-matrix signaling and substantially different diffusion/transport pathways. To obtain tissue-mimic information on nanoparticle toxicity from in vitro cell tests, we used a 3-dimensional (3D) culture of human lung cells (A549) prepared with elastin-like peptides modified with an arginine-glycine-aspartate motif. The 3D cells showed different cellular phenotypes, gene expression profiles, and functionalities compared to the 2D cultured cells. In gene array analysis, 3D cells displayed the induced extracellular matrix (ECM)-related biological functions such as cell-to-cell signaling and interaction, cellular function and maintenance, connective tissue development and function, molecular transport, and tissue morphology. Additionally, the expression of ECM-related molecules, such as laminin, fibronectin, and insulin-like growth factor binding protein 3 (IGFBP3), was simultaneously induced at both mRNA and protein levels. When 0.08-50 microg/ml zinc oxide nanoparticles (ZnO-NPs) were administered to 2D and 3D cells, the cell proliferation was not significantly changed. The level of molecular markers for oxidative stress, such as superoxide dismutase (SOD), Bcl-2, ATP synthase, and Complex IV (cytochrome C oxidase), was significantly reduced in 2D culture when exposed to 10 microg/ml ZnO-NPs, but no significant decrease was detected in 3D culture when exposed to the same concentration of ZnO-NPs. In conclusion, the tissue-mimic phenotype and functionality of 3D cells could be achieved through the elevated expression of ECM components. The 3D cells were expected to help to better predict the nanotoxicity of ZnO-NPs at tissue-level by increased cell-cell and cell-ECM adhesion and signaling. The tissue-mimic morphology would also be useful to simulate the diffusion/transport of the nanoparticles in vitro.

  3. Nonlinear Photochromic Switching in the Plasmonic Field of a Nanoparticle Array

    NASA Astrophysics Data System (ADS)

    Otolski, Christopher J.; Argyropoulos, Christos; Elles, Christopher G.

    2017-06-01

    Plasmonic nanostructures provide unique environments for non-resonant excitation and switching of photochromic compounds. In this study, photochromic diarylethene molecules were deposited on top of a periodically ordered array of gold nanorods (170 x 80 nm) and then irradiated with <100 fs laser pulses. Irradiation at 800 nm drives the plasmon resonance of the nanoparticle array and induces the photochromic conversion of molecules via non-resonant two-photon excitation. Transmission measurements using broadband continuum laser pulses probe the progress of the photochemical cycloreversion reaction as molecules switch from a visible-absorbing closed-ring structure to a transparent open-ring structure. The spatial dependence of the two-photon conversion of molecules in the plasmonic near field of the array is modeled using calculated field enhancements, and compared with similar measurements for a film of molecules on a glass substrate. Wavelength-dependent polarization effects in the near field of the array lead to interesting anisotropy results in the transmission signal. The results emphasize the importance of both the spatial dependence and anisotropy of the enhanced electric fields in driving non-resonant photochromic reactions.

  4. Stacked 3D RRAM Array with Graphene/CNT as Edge Electrodes.

    PubMed

    Bai, Yue; Wu, Huaqiang; Wang, Kun; Wu, Riga; Song, Lin; Li, Tianyi; Wang, Jiangtao; Yu, Zhiping; Qian, He

    2015-09-08

    There are two critical challenges which determine the array density of 3D RRAM: 1) the scaling limit in both horizontal and vertical directions; 2) the integration of selector devices in 3D structure. In this work, we present a novel 3D RRAM structure using low-dimensional materials, including 2D graphene and 1D carbon nanotube (CNT), as the edge electrodes. A two-layer 3D RRAM with monolayer graphene as edge electrode is demonstrated. The electrical results reveal that the RRAM devices could switch normally with this very thin edge electrode at nanometer scale. Meanwhile, benefited from the asymmetric carrier transport induced by Schottky barrier at metal/CNT and oxide/CNT interfaces, a selector built-in 3D RRAM structure using CNT as edge electrode is successfully fabricated and characterized. Furthermore, the discussion of high array density potential is presented.

  5. Martensitic and austenitic transformations in core-surface cubic nanoparticles

    NASA Astrophysics Data System (ADS)

    Özüm, S.; Yalçın, O.; Erdem, R.; Bayrakdar, H.; Eker, H. N.

    2015-01-01

    As a continuation of our recently published work, we have used the pair approximation in Kikuchi version to investigate martensitic and austenitic transformations in homogeneous (HM) and composite (CM) cubic nanoparticles (CNPs) based on the Blume-Emery-Griffiths model. A single cubic nanoparticle made of a core surrounded by a surface is considered as shaped in two dimensional (2D) square arrays instead of hexagonal array. From the phase diagrams of HM and CM-CNPs it has been observed that the martensitic-austenitic transformations (MT-AT) occurred. The influence of the exchange coupling and single-ion anisotropy parameters in the model Hamiltonian on the MT-AT is studied and analyzed in comparison with the results for hexagonal nanoparticles. Significant changes of the phase transition points and hysteresis behaviours depending upon the particle structure have been discussed.

  6. ScintSim1: A new Monte Carlo simulation code for transport of optical photons in 2D arrays of scintillation detectors.

    PubMed

    Mosleh-Shirazi, Mohammad Amin; Zarrini-Monfared, Zinat; Karbasi, Sareh; Zamani, Ali

    2014-01-01

    Two-dimensional (2D) arrays of thick segmented scintillators are of interest as X-ray detectors for both 2D and 3D image-guided radiotherapy (IGRT). Their detection process involves ionizing radiation energy deposition followed by production and transport of optical photons. Only a very limited number of optical Monte Carlo simulation models exist, which has limited the number of modeling studies that have considered both stages of the detection process. We present ScintSim1, an in-house optical Monte Carlo simulation code for 2D arrays of scintillation crystals, developed in the MATLAB programming environment. The code was rewritten and revised based on an existing program for single-element detectors, with the additional capability to model 2D arrays of elements with configurable dimensions, material, etc., The code generates and follows each optical photon history through the detector element (and, in case of cross-talk, the surrounding ones) until it reaches a configurable receptor, or is attenuated. The new model was verified by testing against relevant theoretically known behaviors or quantities and the results of a validated single-element model. For both sets of comparisons, the discrepancies in the calculated quantities were all <1%. The results validate the accuracy of the new code, which is a useful tool in scintillation detector optimization.

  7. [The Dose Effect of Isocenter Selection during IMRT Dose Verification with the 2D Chamber Array].

    PubMed

    Xie, Chuanbin; Cong, Xiaohu; Xu, Shouping; Dai, Xiangkun; Wang, Yunlai; Han, Lu; Gong, Hanshun; Ju, Zhongjian; Ge, Ruigang; Ma, Lin

    2015-03-01

    To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as P(o), P(x) and P(y). P(o) was fixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0 degrees. The γ-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate of γ-analysis was highest in the P(o) group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in P(y) group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.

  8. Spectroscopic Imaging of NIR to Visible Upconversion from NaYF4:Yb3+, Er3+ Nanoparticles on Au Nano-cavity Arrays

    NASA Astrophysics Data System (ADS)

    Fisher, Jon; Zhao, Bo; Lin, Cuikun; Berry, Mary; May, P. Stanley; Smith, Steve

    2015-03-01

    We use spectroscopic imaging to assess the spatial variations in upconversion luminescence from NaYF4:Er3+,Yb3+ nanoparticles embedded in PMMA on Au nano-cavity arrays. The nano-cavity arrays support a surface plasmon (SP) resonance at 980nm, coincident with the peak absorption of the Yb3+ sensitizer. Spatially-resolved upconversion spectra show a 30X to 3X luminescence intensity enhancement on the nano-cavity array compared to the nearby smooth Au surface, corresponding to excitation intensities from 1 W/cm2 to 300kW/cm2. Our analysis shows the power dependent enhancement in upconversion luminescence can be almost entirely accounted for by a constant shift in the effective excitation intensity, which is maintained over five orders of magnitude variation in excitation intensity. The variations in upconversion luminescence enhancement with power are modeled by a 3-level-system near the saturation limit, and by simultaneous solution of a system of coupled nonlinear differential equations, both analyses agree well with the experiments. Analysis of the statistical distribution of emission intensities in the spectroscopic images on and off the nano-cavity arrays provides an estimate of the average enhancement factor independent of fluctuations in nano-particle density. Funding provided by NSF Award # 0903685 (IGERT).

  9. Plasmonic nanoparticle lithography: Fast resist-free laser technique for large-scale sub-50 nm hole array fabrication

    NASA Astrophysics Data System (ADS)

    Pan, Zhenying; Yu, Ye Feng; Valuckas, Vytautas; Yap, Sherry L. K.; Vienne, Guillaume G.; Kuznetsov, Arseniy I.

    2018-05-01

    Cheap large-scale fabrication of ordered nanostructures is important for multiple applications in photonics and biomedicine including optical filters, solar cells, plasmonic biosensors, and DNA sequencing. Existing methods are either expensive or have strict limitations on the feature size and fabrication complexity. Here, we present a laser-based technique, plasmonic nanoparticle lithography, which is capable of rapid fabrication of large-scale arrays of sub-50 nm holes on various substrates. It is based on near-field enhancement and melting induced under ordered arrays of plasmonic nanoparticles, which are brought into contact or in close proximity to a desired material and acting as optical near-field lenses. The nanoparticles are arranged in ordered patterns on a flexible substrate and can be attached and removed from the patterned sample surface. At optimized laser fluence, the nanohole patterning process does not create any observable changes to the nanoparticles and they have been applied multiple times as reusable near-field masks. This resist-free nanolithography technique provides a simple and cheap solution for large-scale nanofabrication.

  10. 2D array transducers for real-time 3D ultrasound guidance of interventional devices

    NASA Astrophysics Data System (ADS)

    Light, Edward D.; Smith, Stephen W.

    2009-02-01

    We describe catheter ring arrays for real-time 3D ultrasound guidance of devices such as vascular grafts, heart valves and vena cava filters. We have constructed several prototypes operating at 5 MHz and consisting of 54 elements using the W.L. Gore & Associates, Inc. micro-miniature ribbon cables. We have recently constructed a new transducer using a braided wiring technology from Precision Interconnect. This transducer consists of 54 elements at 4.8 MHz with pitch of 0.20 mm and typical -6 dB bandwidth of 22%. In all cases, the transducer and wiring assembly were integrated with an 11 French catheter of a Cook Medical deployment device for vena cava filters. Preliminary in vivo and in vitro testing is ongoing including simultaneous 3D ultrasound and x-ray fluoroscopy.

  11. One-step electrodeposition of Co0·12Ni1·88S2@Co8S9 nanoparticles on highly conductive TiO2 nanotube arrays for battery-type electrodes with enhanced energy storage performance

    NASA Astrophysics Data System (ADS)

    Yu, Cuiping; Wang, Yan; Zhang, Jianfang; Yang, Wanfen; Shu, Xia; Qin, Yongqiang; Cui, Jiewu; Zheng, Hongmei; Zhang, Yong; Ajayan, Pulickel M.; Wu, Yucheng

    2017-10-01

    High-performance battery-type electrodes based on TiO2 nanotube arrays decorated with Co0·12Ni1·88S2@Co8S9 (CNCS) nanoparticles have been successfully prepared in this paper. The highly conductive TiO2 nanotube arrays modified with carbon and oxygen vacancies (Ti3+ defects) (m-TNAs) are selected as the three-dimensional backbones to support electroactive materials and offer direct pathways for electron and ions transport. Then CNCS nanoparticles are electrodeposited on each nanotube uniformly, and the loading mass of nanoparticles can be controlled through adjusting electrodeposition cycles. After optimization, a remarkable specific capacity of 680.1 C g-1 is achieved at 2 A g -1 as a result of the intrinsic synergetic contributions from structural/compositional/componental merits. This specific capacity is much higher than most of the TNAs-based energy storage electrodes. In addition, an asymmetric supercapacitor device is assembled by applying the optimized CNCS/m-TNAs and commercial active carbon as positive and negative electrode, respectively. It displays a high energy density of 45.5 Wh kg-1 at a power density of 400.5 W kg-1, after cycling for 3000 cycles at a high current density of 4 A g-1, the specific capacitance could still remain 85.7%. This self-supported and binder-free CNCS/m-TNAs electrode will be a competitive and promising candidate for the application in energy storage.

  12. Pattern transfer with stabilized nanoparticle etch masks

    NASA Astrophysics Data System (ADS)

    Hogg, Charles R.; Picard, Yoosuf N.; Narasimhan, Amrit; Bain, James A.; Majetich, Sara A.

    2013-03-01

    Self-assembled nanoparticle monolayer arrays are used as an etch mask for pattern transfer into Si and SiOx substrates. Crack formation within the array is prevented by electron beam curing to fix the nanoparticles to the substrate, followed by a brief oxygen plasma to remove excess carbon. This leaves a dot array of nanoparticle cores with a minimum gap of 2 nm. Deposition and liftoff can transform the dot array mask into an antidot mask, where the gap is determined by the nanoparticle core diameter. Reactive ion etching is used to transfer the dot and antidot patterns into the substrate. The effect of the gap size on the etching rate is modeled and compared with the experimental results.

  13. Stacked 3D RRAM Array with Graphene/CNT as Edge Electrodes

    PubMed Central

    Bai, Yue; Wu, Huaqiang; Wang, Kun; Wu, Riga; Song, Lin; Li, Tianyi; Wang, Jiangtao; Yu, Zhiping; Qian, He

    2015-01-01

    There are two critical challenges which determine the array density of 3D RRAM: 1) the scaling limit in both horizontal and vertical directions; 2) the integration of selector devices in 3D structure. In this work, we present a novel 3D RRAM structure using low-dimensional materials, including 2D graphene and 1D carbon nanotube (CNT), as the edge electrodes. A two-layer 3D RRAM with monolayer graphene as edge electrode is demonstrated. The electrical results reveal that the RRAM devices could switch normally with this very thin edge electrode at nanometer scale. Meanwhile, benefited from the asymmetric carrier transport induced by Schottky barrier at metal/CNT and oxide/CNT interfaces, a selector built-in 3D RRAM structure using CNT as edge electrode is successfully fabricated and characterized. Furthermore, the discussion of high array density potential is presented. PMID:26348797

  14. 2-D Ultrasound Sparse Arrays Multidepth Radiation Optimization Using Simulated Annealing and Spiral-Array Inspired Energy Functions.

    PubMed

    Roux, Emmanuel; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Robini, Marc C; Liebgott, Herve

    2016-12-01

    Full matrix arrays are excellent tools for 3-D ultrasound imaging, but the required number of active elements is too high to be individually controlled by an equal number of scanner channels. The number of active elements is significantly reduced by the sparse array techniques, but the position of the remaining elements must be carefully optimized. This issue is faced here by introducing novel energy functions in the simulated annealing (SA) algorithm. At each iteration step of the optimization process, one element is freely translated and the associated radiated pattern is simulated. To control the pressure field behavior at multiple depths, three energy functions inspired by the pressure field radiated by a Blackman-tapered spiral array are introduced. Such energy functions aim at limiting the main lobe width while lowering the side lobe and grating lobe levels at multiple depths. Numerical optimization results illustrate the influence of the number of iterations, pressure measurement points, and depths, as well as the influence of the energy function definition on the optimized layout. It is also shown that performance close to or even better than the one provided by a spiral array, here assumed as reference, may be obtained. The finite-time convergence properties of SA allow the duration of the optimization process to be set in advance.

  15. SERS of Methylene Blue induced by plasmonic coupled nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Kaydashev, V. E.; Lyanguzov, N. V.; Anokhin, A. S.; Chernishov, A.; Kaidashev, E. M.

    2018-04-01

    We study the surface enhanced Raman scattering of Methylene Blue (MB) dye molecules induced by large quasihomogeneous arrays of plasmon coupled 5-8 nm Au nanoparticle separated by distances less than 10 nm. Also, the variation of the fluorescence enhancement/SERS properties for as-prepared coupled particles and agglomerated particles obtained upon heat treatment and percolation-like films is analyzed for two measurement protocols, i.e. when measured through the solution and for a monolayer of MB molecules chemisorbed on a surface.

  16. Investigation of magnetization dynamics in 2D Ni80Fe20 diatomic nanodot arrays

    NASA Astrophysics Data System (ADS)

    De, Anulekha; Mondal, Sucheta; Banerjee, Chandrima; Chaurasiya, Avinash K.; Mandal, Ruma; Otani, Yoshichika; Mitra, Rajib K.; Barman, Anjan

    2017-09-01

    Magnetization dynamics in Ni80Fe20 (Py) diatomic nanodots (nanodots of the same thickness but with large and small diameters that are closely placed to each other so as to act as a diatomic basis structure) embedded in 2D arrays have been investigated by the Brillouin light scattering technique. A distinct variation of resonant mode characteristics for different in-plane bias magnetic field applied along two different orientations of the lattice has been observed. Micromagnetic simulations reproduced the observed dynamical behaviour and revealed the variation of spatial distribution of collective modes of constituent single nanodots with different diameter and a diatomic unit forming the large array to understand the evolution of the magnetization dynamics from a single dot to the large array via a diatomic unit. The changes in mode frequency, spatial profiles of the modes, and appearance of new modes in a diatomic unit and its array from that of the constituent single dots indicate the strong magnetostatic interaction among the dots within the diatomic unit. Also, the occurrence of the new interacting mode at different frequencies for different orientations of the bias field indicates the change in the nature of interaction among the dots within the diatomic unit with bias magnetic field. The mode profiles also show distinct behaviour for smooth and rough-edged dots. This work motivates the study of magnonic band structure formation of such a dipolarly coupled nanodot array containing a complex double-dot unit cell.

  17. Prescribed nanoparticle cluster architectures and low-dimensional arrays built using octahedral DNA origami frames

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Wang, Tong; Liu, Wenyan; Xin, Huolin L.; Li, Huilin; Ke, Yonggang; Shih, William M.; Gang, Oleg

    2015-07-01

    Three-dimensional mesoscale clusters that are formed from nanoparticles spatially arranged in pre-determined positions can be thought of as mesoscale analogues of molecules. These nanoparticle architectures could offer tailored properties due to collective effects, but developing a general platform for fabricating such clusters is a significant challenge. Here, we report a strategy for assembling three-dimensional nanoparticle clusters that uses a molecular frame designed with encoded vertices for particle placement. The frame is a DNA origami octahedron and can be used to fabricate clusters with various symmetries and particle compositions. Cryo-electron microscopy is used to uncover the structure of the DNA frame and to reveal that the nanoparticles are spatially coordinated in the prescribed manner. We show that the DNA frame and one set of nanoparticles can be used to create nanoclusters with different chiroptical activities. We also show that the octahedra can serve as programmable interparticle linkers, allowing one- and two-dimensional arrays to be assembled with designed particle arrangements.

  18. Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian

    2013-05-01

    Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions (>100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings, facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled 9Be+ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be+ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, d, may be varied continuously from 1 /d0 to 1 /d3. An effective transverse magnetic field is applied via microwave radiation at the ~124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states. We acknowledge support from NIST and the DARPA-OLE program.

  19. Improved 2-D resistivity imaging of features in covered karst terrain with arrays of implanted electrodes

    NASA Astrophysics Data System (ADS)

    Kiflu, H. G.; Kruse, S. E.; Harro, D.; Loke, M. H.; Wilkinson, P. B.

    2013-12-01

    Electrical resistivity tomography is commonly used to identify geologic features associated with sinkhole formation. In covered karst terrain, however, it can be difficult to resolve the depth to top of limestone with this method. This is due to the fact that array lengths, and hence depth of resolution, are often limited by residential or commercial lot dimensions in urban environments. Furthermore, the sediments mantling the limestone are often clay-rich and highly conductive. The resistivity method has limited sensitivity to resistive zones beneath conductive zones. This sensitivity can be improved significantly with electrodes implanted at depth in the cover sediments near the top of limestone. An array of deep electrodes is installed with direct push technology in the karst cover. When combined with a surface array in which each surface electrode is underlain by a deep electrode, the array geometry is similar to a borehole array turned on its side. This method, called the Multi-Electrode Resistivity Implant Technique (MERIT), offers the promise of significantly improved resolution of epikarst and cover collapse development zones in the overlying sediment, the limestone or at the sediment-bedrock interface in heterogeneous karst environments. With a non-traditional array design, the question of optimal array geometries arises. Optimizing array geometries is complicated by the fact that many plausible 4-electrode readings will produce negative apparent resistivity values, even in homogeneous terrain. Negative apparent resistivities cannot be used in inversions based on the logarithm of the apparent resistivity. New algorithms for seeking optimal array geometries have been developed by modifying the 'Compare R' method of Wilkinson and Loke. The optimized arrays show significantly improved resolution over basic arrays adapted from traditional 2D surface geometries. Several MERIT case study surveys have been conducted in covered karst in west-central Florida, with

  20. ScintSim1: A new Monte Carlo simulation code for transport of optical photons in 2D arrays of scintillation detectors

    PubMed Central

    Mosleh-Shirazi, Mohammad Amin; Zarrini-Monfared, Zinat; Karbasi, Sareh; Zamani, Ali

    2014-01-01

    Two-dimensional (2D) arrays of thick segmented scintillators are of interest as X-ray detectors for both 2D and 3D image-guided radiotherapy (IGRT). Their detection process involves ionizing radiation energy deposition followed by production and transport of optical photons. Only a very limited number of optical Monte Carlo simulation models exist, which has limited the number of modeling studies that have considered both stages of the detection process. We present ScintSim1, an in-house optical Monte Carlo simulation code for 2D arrays of scintillation crystals, developed in the MATLAB programming environment. The code was rewritten and revised based on an existing program for single-element detectors, with the additional capability to model 2D arrays of elements with configurable dimensions, material, etc., The code generates and follows each optical photon history through the detector element (and, in case of cross-talk, the surrounding ones) until it reaches a configurable receptor, or is attenuated. The new model was verified by testing against relevant theoretically known behaviors or quantities and the results of a validated single-element model. For both sets of comparisons, the discrepancies in the calculated quantities were all <1%. The results validate the accuracy of the new code, which is a useful tool in scintillation detector optimization. PMID:24600168

  1. Analysis of the scattering and absorption properties of ellipsoidal nanoparticle arrays for the design of full-color transparent screens

    NASA Astrophysics Data System (ADS)

    Monti, Alessio; Toscano, Alessandro; Bilotti, Filiberto

    2017-06-01

    The introduction of nanoparticles-based screens [C. W. Hsu, Nat. Commun. 5, 3152 (2014)] has paved the way to the realization of low-cost transparent displays with a wide viewing angle and scalability to large size. Despite the huge potentialities of this approach, the design of a nanoparticles array exhibiting a sharp scattering response in the optical spectrum is still a challenging task. In this manuscript, we investigate the suitability of ellipsoidal plasmonic nanoparticles for this purpose. First, we show that some trade-offs between the sharpness of the scattering response of the array and its absorption level apply. Starting from these considerations, we prove that prolate nanoparticles may be a plausible candidate for achieving the peculiar features required in transparent screen applications. An example of a full-color and almost-isotropic transparent screen is finally proposed and its robustness towards the geometrical inaccuracies that may arise during the fabrication process is assessed. All the analytical considerations, carried out through an analytical model taking into account the surface dispersion effect affecting the nanoparticles, are supported by a proper set of full-wave simulations.

  2. Formation of embedded plasmonic Ga nanoparticle arrays and their influence on GaAs photoluminescence

    NASA Astrophysics Data System (ADS)

    Kang, M.; Jeon, S.; Jen, T.; Lee, J.-E.; Sih, V.; Goldman, R. S.

    2017-07-01

    We introduce a novel approach to the seamless integration of plasmonic nanoparticle (NP) arrays into semiconductor layers and demonstrate their enhanced photoluminescence (PL) efficiency. Our approach utilizes focused ion beam-induced self-assembly of close-packed arrays of Ga NPs with tailorable NP diameters, followed by overgrowth of GaAs layers using molecular beam epitaxy. Using a combination of PL spectroscopy and electromagnetic computations, we identify a regime of Ga NP diameter and overgrown GaAs layer thickness where NP-array-enhanced absorption in GaAs leads to enhanced GaAs near-band-edge (NBE) PL efficiency, surpassing that of high-quality epitaxial GaAs layers. As the NP array depth and size are increased, the reduction in spontaneous emission rate overwhelms the NP-array-enhanced absorption, leading to a reduced NBE PL efficiency. This approach provides an opportunity to enhance the PL efficiency of a wide variety of semiconductor heterostructures.

  3. Uncooled Terahertz real-time imaging 2D arrays developed at LETI: present status and perspectives

    NASA Astrophysics Data System (ADS)

    Simoens, François; Meilhan, Jérôme; Dussopt, Laurent; Nicolas, Jean-Alain; Monnier, Nicolas; Sicard, Gilles; Siligaris, Alexandre; Hiberty, Bruno

    2017-05-01

    As for other imaging sensor markets, whatever is the technology, the commercial spread of terahertz (THz) cameras has to fulfil simultaneously the criteria of high sensitivity and low cost and SWAP (size, weight and power). Monolithic silicon-based 2D sensors integrated in uncooled THz real-time cameras are good candidates to meet these requirements. Over the past decade, LETI has been studying and developing such arrays with two complimentary technological approaches, i.e. antenna-coupled silicon bolometers and CMOS Field Effect Transistors (FET), both being compatible to standard silicon microelectronics processes. LETI has leveraged its know-how in thermal infrared bolometer sensors in developing a proprietary architecture for THz sensing. High technological maturity has been achieved as illustrated by the demonstration of fast scanning of large field of view and the recent birth of a commercial camera. In the FET-based THz field, recent works have been focused on innovative CMOS read-out-integrated circuit designs. The studied architectures take advantage of the large pixel pitch to enhance the flexibility and the sensitivity: an embedded in-pixel configurable signal processing chain dramatically reduces the noise. Video sequences at 100 frames per second using our 31x31 pixels 2D Focal Plane Arrays (FPA) have been achieved. The authors describe the present status of these developments and perspectives of performance evolutions are discussed. Several experimental imaging tests are also presented in order to illustrate the capabilities of these arrays to address industrial applications such as non-destructive testing (NDT), security or quality control of food.

  4. Engineering electric and magnetic dipole coupling in arrays of dielectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Jiaqi; Verellen, Niels; Van Dorpe, Pol

    2018-02-01

    Dielectric nanoparticles with both strong electric and magnetic dipole (ED and MD) resonances offer unique opportunities for efficient manipulation of light-matter interactions. Here, based on numerical simulations, we show far-field diffractive coupling of the ED and MD modes in a periodic rectangular array. By using unequal periodicities in the orthogonal directions, each dipole mode is separately coupled and strongly tuned. With this method, the electric and magnetic response of the dielectric nanoparticles can be deliberately engineered to accomplish various optical functionalities. Remarkably, an ultra-sharp MD resonance with sub-10 nm linewidth is achieved with a large enhancement factor for the magnetic field intensity on the order of ˜103. Our results will find useful applications for the detection of chemical and biological molecules as well as the design of novel photonic metadevices.

  5. Biologically Derived Nanoparticle Arrays via a Site-Specific Reconstitution of Ferritin and their Electrochemistry

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Choi, Sang H.; Lillehei, Peter T.; King, Glen C.; Elliott, James R.; Chu, Sang-Hyon; Park, Yeonjoon; Watt, Gerald D.

    2004-01-01

    Nanoparticle arrays biologically derived from an electrochemically-controlled site-specific biomineralization were fabricated on a gold substrate through the immobilization process of biomolecules. The work reported herein includes the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritins with different inorganic cores, the fabrication of self-assembled arrays with the immobilized ferritin, and the electrochemical characterization of various core materials. Protein immobilization on the substrate is achieved by anchoring ferritins with dithiobis-N-succinimidyl propionate (DTSP). A reconstitution process of electrochemical site-specific biomineralization with a protein cage loads ferritins with different core materials such as Pt, Co, Mn, and Ni. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. The nano-sized metalcored ferritins on a gold substrate displayed a good electrochemical activity for the electron transport and storage, which is suitable for bioelectronics applications such as biofuel cell, bionanobattery, biosensors, etc. Keywords: Ferritin, immobilization, site-specific reconstitution, biomineralization, and bioelectronics

  6. An optimized nanoparticle separator enabled by electron beam induced deposition

    NASA Astrophysics Data System (ADS)

    Fowlkes, J. D.; Doktycz, M. J.; Rack, P. D.

    2010-04-01

    Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.

  7. Deep Tissue Photoacoustic Imaging Using a Miniaturized 2-D Capacitive Micromachined Ultrasonic Transducer Array

    PubMed Central

    Kothapalli, Sri-Rajasekhar; Ma, Te-Jen; Vaithilingam, Srikant; Oralkan, Ömer

    2014-01-01

    In this paper, we demonstrate 3-D photoacoustic imaging (PAI) of light absorbing objects embedded as deep as 5 cm inside strong optically scattering phantoms using a miniaturized (4 mm × 4 mm × 500 µm), 2-D capacitive micromachined ultrasonic transducer (CMUT) array of 16 × 16 elements with a center frequency of 5.5 MHz. Two-dimensional tomographic images and 3-D volumetric images of the objects placed at different depths are presented. In addition, we studied the sensitivity of CMUT-based PAI to the concentration of indocyanine green dye at 5 cm depth inside the phantom. Under optimized experimental conditions, the objects at 5 cm depth can be imaged with SNR of about 35 dB and a spatial resolution of approximately 500 µm. Results demonstrate that CMUTs with integrated front-end amplifier circuits are an attractive choice for achieving relatively high depth sensitivity for PAI. PMID:22249594

  8. Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks.

    PubMed

    Li, Z P; Xu, Z M; Qu, X P; Wang, S B; Peng, J; Mei, L H

    2017-03-03

    How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

  9. Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks

    NASA Astrophysics Data System (ADS)

    Li, Z. P.; Xu, Z. M.; Qu, X. P.; Wang, S. B.; Peng, J.; Mei, L. H.

    2017-03-01

    How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

  10. Computational Design of Tunable UV-Vis-IR Filters Based on Silver Nanoparticle Arrays

    NASA Astrophysics Data System (ADS)

    Waters, Michael; Shi, Guangsha; Kioupakis, Emmanouil

    We propose design strategies to develop selective optical filters in the UV-Vis-IR spectrum using the surface plasmon response of silver nanoparticle arrays. Our finite-difference time-domain simulations allow us to rapidly evaluate many nanostructures comprising simple geometries while varying their shape, height, width, and spacing. Our results allow us to identify trends in the filtering spectra as well as the relative amount of absorption and reflection. Optical filtering with nanoparticles is applicable to any transparent substrate and can be easily adapted to existing manufacturing processes while keeping the total cost of materials low. This work was supported by Guardian Industries Corp.

  11. Electrochemical and in vitro neuronal recording characteristics of multi-electrode arrays surface-modified with electro-co-deposited gold-platinum nanoparticles.

    PubMed

    Kim, Yong Hee; Kim, Ah Young; Kim, Gook Hwa; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

    2016-02-01

    In order to complement the high impedance electrical property of gold nanoparticles (Au NPs) we have performed electro-co-deposition of gold-platinum nanoparticles (Au-Pt NPs) onto the Au multi-electrode array (MEA) and modified the Au-Pt NPs surface with cell adhesive poly-D-lysine via thiol chemistry based covalent binding. The Au-Pt NPs were analyzed to have bimetallic nature not the mixture of Au NPs and Pt NPs by X-ray diffraction analysis and to have impedance value (4.0 × 10(4) Ω (at 1 kHz)) comparable to that of Pt NPs. The performance of Au-Pt NP-modified MEAs was also checked in relation to neuronal signal recording. The noise level in Au-Pt NP-modified MEAs was lower than in that of Au NP-modified MEA.

  12. Probing the Interaction of Dielectric Nanoparticles with Supported Lipid Membrane Coatings on Nanoplasmonic Arrays

    PubMed Central

    Ferhan, Abdul Rahim; Ma, Gamaliel Junren; Jackman, Joshua A.; Sut, Tun Naw; Park, Jae Hyeon; Cho, Nam-Joon

    2017-01-01

    The integration of supported lipid membranes with surface-based nanoplasmonic arrays provides a powerful sensing approach to investigate biointerfacial phenomena at membrane interfaces. While a growing number of lipid vesicles, protein, and nucleic acid systems have been explored with nanoplasmonic sensors, there has been only very limited investigation of the interactions between solution-phase nanomaterials and supported lipid membranes. Herein, we established a surface-based localized surface plasmon resonance (LSPR) sensing platform for probing the interaction of dielectric nanoparticles with supported lipid bilayer (SLB)-coated, plasmonic nanodisk arrays. A key emphasis was placed on controlling membrane functionality by tuning the membrane surface charge vis-à-vis lipid composition. The optical sensing properties of the bare and SLB-coated sensor surfaces were quantitatively compared, and provided an experimental approach to evaluate nanoparticle–membrane interactions across different SLB platforms. While the interaction of negatively-charged silica nanoparticles (SiNPs) with a zwitterionic SLB resulted in monotonic adsorption, a stronger interaction with a positively-charged SLB resulted in adsorption and lipid transfer from the SLB to the SiNP surface, in turn influencing the LSPR measurement responses based on the changing spatial proximity of transferred lipids relative to the sensor surface. Precoating SiNPs with bovine serum albumin (BSA) suppressed lipid transfer, resulting in monotonic adsorption onto both zwitterionic and positively-charged SLBs. Collectively, our findings contribute a quantitative understanding of how supported lipid membrane coatings influence the sensing performance of nanoplasmonic arrays, and demonstrate how the high surface sensitivity of nanoplasmonic sensors is well-suited for detecting the complex interactions between nanoparticles and lipid membranes. PMID:28644423

  13. Enhanced Optical Transmission Mediated by Localized Plasmons in Anisotropic, 3D Nanohole Arrays

    PubMed Central

    Yang, Jiun-Chan; Gao, Hanwei; Suh, Jae Yong; Zhou, Wei; Lee, Min Hyung; Odom, Teri W.

    2010-01-01

    This paper describes 3D nanohole arrays whose high optical transmission is mediated more by localized surface plasmon (LSP) excitations than by surface plasmon polaritons (SPPs). First, LSPs on 3D hole arrays lead to optical transmission an order of magnitude higher than 2D planar hole arrays. Second, LSP-mediated transmission is broadband and more tunable than SPP-enhanced transmission which is restricted by Bragg coupling. Third, for the first time, two types of surface plasmons can be selectively excited and manipulated on the same plasmonic substrate. This new plasmonic substrate fabricated by high-throughput nanolithography techniques paves the way for cutting-edge optoelectronic and biomedical applications. PMID:20698633

  14. A High-Frequency Linear Ultrasonic Array Utilizing an Interdigitally Bonded 2-2 Piezo-Composite

    PubMed Central

    Cannata, Jonathan M.; Williams, Jay A.; Zhang, Lequan; Hu, Chang-Hong; Shung, K. Kirk

    2011-01-01

    This paper describes the development of a high-frequency 256-element linear ultrasonic array utilizing an interdigitally bonded (IB) piezo-composite. Several IB composites were fabricated with different commercial and experimental piezoelectric ceramics and evaluated to determine a suitable formulation for use in high-frequency linear arrays. It was found that the fabricated fine-scale 22 IB composites outperformed 1–3 IB composites with identical pillar- and kerf-widths. This result was not expected and lead to the conclusion that dicing damage was likely the cause of the discrepancy. Ultimately, a 22 composite fabricated using a fine-grain piezoelectric ceramic was chosen for the array. The composite was manufactured using one IB operation in the azimuth direction to produce approximately 19-μm-wide pillars separated by 6-μm-wide kerfs. The array had a 50 μm (one wavelength in water) azimuth pitch, two matching layers, and 2 mm elevation length focused to 7.3 mm using a polymethylpentene (TPX) lens. The measured pulse-echo center frequency for a representative array element was 28 MHz and −6-dB band-width was 61%. The measured single-element transmit −6-dB directivity was estimated to be 50°. The measured insertion loss was 19 dB after compensating for the effects of attenuation and diffraction in the water bath. A fine-wire phantom was used to assess the lateral and axial resolution of the array when paired with a prototype system utilizing a 64-channel analog beamformer. The −6-dB lateral and axial resolutions were estimated to be 125 and 68 μm, respectively. An anechoic cyst phantom was also imaged to determine the minimum detectable spherical inclusion, and thus the 3-D resolution of the array and beamformer. The minimum anechoic cyst detected was approximately 300 μm in diameter. PMID:21989884

  15. One-dimensional ferromagnetic array compound [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate)

    NASA Astrophysics Data System (ADS)

    Honda, Zentaro; Nomoto, Naoyuki; Fujihara, Takashi; Hagiwara, Masayuki; Kida, Takanori; Sawada, Yuya; Fukuda, Takeshi; Kamata, Norihiko

    2018-06-01

    We report on the syntheses, crystal structure, and magnetic properties of the transition metal coordination polymer [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate) in which CoO6 octahedra are linked through their edges, forming one-dimensional (1D) Co(II) arrays running along the crystal a-axis. These arrays are further perpendicularly bridged by SBA ligand to construct a three-dimensional framework. Its magnetic properties have been investigated, and ferromagnetic interactions within the arrays have been found. From heat capacity measurements, we have found that this compound exhibits a three-dimensional ferromagnetic phase transition at TC = 1.54 K, and the specific heat just above TC shows a Schottky anomaly which originates from an energy gap caused by uniaxial magnetic anisotropy. These results suggest that [Co3(SBA)2(OH)2(H2O)2]n consists of weakly coupled 1D ferromagnetic Ising arrays.

  16. Toward 2D and 3D imaging of magnetic nanoparticles using EPR measurements.

    PubMed

    Coene, A; Crevecoeur, G; Leliaert, J; Dupré, L

    2015-09-01

    Magnetic nanoparticles (MNPs) are an important asset in many biomedical applications. An effective working of these applications requires an accurate knowledge of the spatial MNP distribution. A promising, noninvasive, and sensitive technique to visualize MNP distributions in vivo is electron paramagnetic resonance (EPR). Currently only 1D MNP distributions can be reconstructed. In this paper, the authors propose extending 1D EPR toward 2D and 3D using computer simulations to allow accurate imaging of MNP distributions. To find the MNP distribution belonging to EPR measurements, an inverse problem needs to be solved. The solution of this inverse problem highly depends on the stability of the inverse problem. The authors adapt 1D EPR imaging to realize the imaging of multidimensional MNP distributions. Furthermore, the authors introduce partial volume excitation in which only parts of the volume are imaged to increase stability of the inverse solution and to speed up the measurements. The authors simulate EPR measurements of different 2D and 3D MNP distributions and solve the inverse problem. The stability is evaluated by calculating the condition measure and by comparing the actual MNP distribution to the reconstructed MNP distribution. Based on these simulations, the authors define requirements for the EPR system to cope with the added dimensions. Moreover, the authors investigate how EPR measurements should be conducted to improve the stability of the associated inverse problem and to increase reconstruction quality. The approach used in 1D EPR can only be employed for the reconstruction of small volumes in 2D and 3D EPRs due to numerical instability of the inverse solution. The authors performed EPR measurements of increasing cylindrical volumes and evaluated the condition measure. This showed that a reduction of the inherent symmetry in the EPR methodology is necessary. By reducing the symmetry of the EPR setup, quantitative images of larger volumes can be

  17. High-performance 3D printing of hydrogels by water-dispersible photoinitiator nanoparticles.

    PubMed

    Pawar, Amol A; Saada, Gabriel; Cooperstein, Ido; Larush, Liraz; Jackman, Joshua A; Tabaei, Seyed R; Cho, Nam-Joon; Magdassi, Shlomo

    2016-04-01

    In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)-visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode-based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents.

  18. Scalable, large area compound array refractive lens for hard X-rays

    NASA Astrophysics Data System (ADS)

    Reich, Stefan; dos Santos Rolo, Tomy; Letzel, Alexander; Baumbach, Tilo; Plech, Anton

    2018-04-01

    We demonstrate the fabrication of a 2D Compound Array Refractive Lens (CARL) for multi-contrast X-ray imaging. The CARL consists of six stacked polyimide foils with each displaying a 2D array of lenses with a 65 μm pitch aiming for a sensitivity on sub-micrometer structures with a (few-)micrometer resolution in sensing through phase and scattering contrast at multiple keV. The parabolic lenses are formed by indents in the foils by a paraboloid needle. The ability for fast single-exposure multi-contrast imaging is demonstrated by filming the kinetics of pulsed laser ablation in liquid. The three contrast channels, absorption, differential phase, and scattering, are imaged with a time resolution of 25 μs. By changing the sample-detector distance, it is possible to distinguish between nanoparticles and microbubbles.

  19. Quantitative 3-d diagnostic ultrasound imaging using a modified transducer array and an automated image tracking technique.

    PubMed

    Hossack, John A; Sumanaweera, Thilaka S; Napel, Sandy; Ha, Jun S

    2002-08-01

    An approach for acquiring dimensionally accurate three-dimensional (3-D) ultrasound data from multiple 2-D image planes is presented. This is based on the use of a modified linear-phased array comprising a central imaging array that acquires multiple, essentially parallel, 2-D slices as the transducer is translated over the tissue of interest. Small, perpendicularly oriented, tracking arrays are integrally mounted on each end of the imaging transducer. As the transducer is translated in an elevational direction with respect to the central imaging array, the images obtained by the tracking arrays remain largely coplanar. The motion between successive tracking images is determined using a minimum sum of absolute difference (MSAD) image matching technique with subpixel matching resolution. An initial phantom scanning-based test of a prototype 8 MHz array indicates that linear dimensional accuracy of 4.6% (2 sigma) is achievable. This result compares favorably with those obtained using an assumed average velocity [31.5% (2 sigma) accuracy] and using an approach based on measuring image-to-image decorrelation [8.4% (2 sigma) accuracy]. The prototype array and imaging system were also tested in a clinical environment, and early results suggest that the approach has the potential to enable a low cost, rapid, screening method for detecting carotid artery stenosis. The average time for performing a screening test for carotid stenosis was reduced from an average of 45 minutes using 2-D duplex Doppler to 12 minutes using the new 3-D scanning approach.

  20. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    PubMed Central

    Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr, Osman M.

    2011-01-01

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (ρP) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. PMID:21654635

  1. Sodium alginate/gelatin with silica nanoparticles a novel hydrogel for 3D printing

    NASA Astrophysics Data System (ADS)

    Soni, Raghav; Roopavath, Uday Kiran; Mahanta, Urbashi; Deshpande, A. S.; Rath, S. N.

    2018-05-01

    Sodium alginate/gelatin hydrogels are promising materials for 3D bio-printing due to its good biocompatibility and biodegradability. Gelatin is used for thermal crosslinking and its cell adhesion properties. Hence patient specific sodium alginate/gelatin hydrogel scaffolds can be bio-fabricated in a temperature range of 4-14 oC. In this study we made an attempt to introduce silica (SiO2) nanoparticles in the polymer network of sodium alginate (2.5%)/gelatin (8%) hydrogel at different concentrations (w/v) as 0%, 1.25%, 2.5%, 5%, and 7.5%. The effect of silica nanoparticles on viscosity, swelling behavior, and degradation rate are analyzed. Hydrogels with 5% silica nanoparticles show significantly less swelling and degradation when compared to other concentrations. The viscosity of the hydrogels gradually increases up to 5% addition of silica nanoparticles enhancing the stability of 3D printed structures.

  2. Incorporation of zinc oxide nanoparticles into chitosan-collagen 3D porous scaffolds: Effect on morphology, mechanical properties and cytocompatibility of 3D porous scaffolds.

    PubMed

    Ullah, Saleem; Zainol, Ismail; Idrus, Ruszymah Hj

    2017-11-01

    The zinc oxide nanoparticles (particles size <50nm) incorporated into chitosan-collagen 3D porous scaffolds and investigated the effect of zinc oxide nanoparticles incorporation on microstructure, mechanical properties, biodegradation and cytocompatibility of 3D porous scaffolds. The 0.5%, 1.0%, 2.0% and 4.0% zinc oxide nanoparticles chitosan-collagen 3D porous scaffolds were fabricated via freeze-drying technique. The zinc oxide nanoparticles incorporation effects consisting in chitosan-collagen 3D porous scaffolds were investigated by mechanical and swelling tests, and effect on the morphology of scaffolds examined microscopically. The biodegradation and cytocompatibility tests were used to investigate the effects of zinc oxide nanoparticles incorporation on the ability of scaffolds to use for tissue engineering application. The mean pore size and swelling ratio of scaffolds were decreased upon incorporation of zinc oxide nanoparticles however, the porosity, tensile modulus and biodegradation rate were increased upon incorporation of zinc oxide nanoparticles. In vitro culture of human fibroblasts and keratinocytes showed that the zinc oxide nanoparticles facilitated cell adhesion, proliferation and infiltration of chitosan-collagen 3D porous scaffolds. It was found that the zinc oxide nanoparticles incorporation enhanced porosity, tensile modulus and cytocompatibility of chitosan-collagen 3D porous scaffolds. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

    NASA Astrophysics Data System (ADS)

    Spirou, S. V.; Tsialios, P.; Loudos, G.

    2015-09-01

    In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

  4. A comparative study of the magnetization in transition metal ion doped CeO2, TiO2 and SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

    2018-05-01

    Using the microscopic s-d model taking into account anharmonic spin-phonon interactions we have studied the magnetic properties of Co and Cu ion doped CeO2 and TiO2 nanoparticles and compared them with those of SnO2. By Co-doping there is a maximum in the magnetization M(x) curve for all nanoparticles observed in the most transition metal doped ones. The s-d interaction plays an important role by the decrease of M at higher dopant concentration. We have discussed the magnetization in dependence of different model parameters. By small Cu-ion doping there are some differences. In CeO2M decreases with the Cu-concentration, whereas in TiO2 and SnO2M increases. For higher Cu dopant concentrations M(X) decreases in TiO2 nanoparticles. We obtain room temperature ferromagnetism also in Zn doped CeO2, TiO2 and SnO2 nanoparticles, i.e. in non-transition metal ion doped ones. The different behavior of M in Co and Cu doped nanoparticles is due to a combination effect of multivalent metal ions, oxygen vacancies, different radius of cation dopants, connection between lattice and magnetism, as well as competition between the s-d and d-d ferromagnetic or antiferromagnetic interactions.

  5. 3D Bi2S3/TiO2 cross-linked heterostructure: An efficient strategy to improve charge transport and separation for high photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Han, Minmin; Jia, Junhong

    2016-10-01

    A novel 3D cross-linked heterostructure of TiO2 nanorods connecting with each other via ultrathin Bi2S3 nanosheets is constructed by a facile and effective strategy. The growth mechanism has been investigated and proposed based on the evolution of microstructure by changing the reaction parameters. Benefiting from the unique cross-linked heterostructure, the as-prepared Bi2S3 nanosheets modified TiO2 nanorods arrays could achieve a high energy conversion efficiency of 3.29% which is the highest value to date for Bi2S3-only sensitized solar cells as the reported highest value is 2.23% and other reported values are less than 1%. Furthermore, the photoelectrochemical studies clearly reveal that the novel cross-linked heterostructure exhibits much better activity than 0D nanoparticles decorated TiO2 nanorods under visible light irradiation, which may be primarily ascribed to the efficient electron transfer from 2D ultrathin Bi2S3 nanosheets to 1D TiO2 nanorod arrays. The promising results in this work confirm the advantages of cross-linked heterostructure and also undoubtedly offer an attractive synthesis strategy to fabricate other nanorod-based hierarchical architecture as well as nano-devices for solar energy conversion.

  6. Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon microcolumn arrays

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Luo, Guanghong; Diao, Jiajie; Chornoguz, Olesya; Reeves, Mark; Vertes, Akos

    2007-04-01

    Due to their optical properties and morphology, thin films formed of nanoparticles are potentially new platforms for soft laser desorption/ionization (SLDI) mass spectrometry. Thin films of gold nanoparticles (with 12±1 nm particle size) were prepared by evaporation-driven vertical colloidal deposition and used to analyze a series of directly deposited polypeptide samples. In this new SLDI method, the required laser fluence for ion detection was equal or less than what was needed for matrix-assisted laser desorption/ionization (MALDI) but the resulting spectra were free of matrix interferences. A silicon microcolumn array-based substrate (a.k.a. black silicon) was developed as a new matrix-free laser desorption ionization surface. When low-resistivity silicon wafers were processed with a 22 ps pulse length 3×ω Nd:YAG laser in air, SF6 or water environment, regularly arranged conical spikes emerged. The radii of the spike tips varied with the processing environment, ranging from approximately 500 nm in water, to ~2 µm in SF6 gas and to ~5 µm in air. Peptide mass spectra directly induced by a nitrogen laser showed the formation of protonated ions of angiotensin I and II, substance P, bradykinin fragment 1-7, synthetic peptide, pro14-arg, and insulin from the processed silicon surfaces but not from the unprocessed areas. Threshold fluences for desorption/ionization were similar to those used in MALDI. Although compared to silicon nanowires the threshold laser pulse energy for ionization is significantly (~10×) higher, the ease of production and robustness of microcolumn arrays offer complementary benefits.

  7. bicep2/ KECK ARRAY . IV. OPTICAL CHARACTERIZATION AND PERFORMANCE OF THE bicep2 AND KECK ARRAY EXPERIMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ade, P. A. R.; Aikin, R. W.; Barkats, D.

    2015-06-18

    bicep2/KECK ARRAY. IV. OPTICAL CHARACTERIZATION AND PERFORMANCE OF THE bicep2 AND KECK ARRAY EXPERIMENTS P. A. R. Ade1, R. W. Aikin2, D. Barkats3, S. J. Benton4, C. A. Bischoff5, J. J. Bock2,6, K. J. Bradford5, J. A. Brevik2, I. Buder5, E. Bullock7Show full author list Published 2015 June 18 • © 2015. The American Astronomical Society. All rights reserved. The Astrophysical Journal, Volume 806, Number 2 Article PDF Figures Tables References Citations 273 Total downloads Cited by 6 articles Turn on MathJax Share this article Get permission to re-use this article Article information Abstract bicep2 and the Keck Array aremore » polarization-sensitive microwave telescopes that observe the cosmic microwave background (CMB) from the South Pole at degree angular scales in search of a signature of inflation imprinted as B-mode polarization in the CMB. bicep2 was deployed in late 2009, observed for three years until the end of 2012 at 150 GHz with 512 antenna-coupled transition edge sensor bolometers, and has reported a detection of B-mode polarization on degree angular scales. The Keck Array was first deployed in late 2010 and will observe through 2016 with five receivers at several frequencies (95, 150, and 220 GHz). bicep2 and the Keck Array share a common optical design and employ the field-proven bicep1 strategy of using small-aperture, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. Here we describe the optical design of both instruments and report a full characterization of the optical performance and beams of bicep2 and the Keck Array at 150 GHz.« less

  8. High-performance 3D printing of hydrogels by water-dispersible photoinitiator nanoparticles

    PubMed Central

    Pawar, Amol A.; Saada, Gabriel; Cooperstein, Ido; Larush, Liraz; Jackman, Joshua A.; Tabaei, Seyed R.; Cho, Nam-Joon; Magdassi, Shlomo

    2016-01-01

    In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)–visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode–based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents. PMID:27051877

  9. Can small hydrophobic gold nanoparticles inhibit β2-microglobulin fibrillation?

    NASA Astrophysics Data System (ADS)

    Brancolini, Giorgia; Toroz, Dimitrios; Corni, Stefano

    2014-06-01

    simulations at multiple levels (Classical Molecular Dynamics and Brownian Dynamics) that cover multiple length- and timescales. The results provide a model of the ensemble of structures constituting the protein-gold nanoparticle complexes, and insights into the driving forces for the binding of β2-microglobulin to hydrophobic small size gold nanoparticles. We have found that the small nanoparticles can bind the protein to form persistent complexes. This binding of nanoparticles is able to block the active sites of domains from binding to another protein, thus leading to potential inhibition of the fibrillation activity. A comparison with the binding patches identified for the interaction of the protein with a known inhibitor of fibrillation, supports our conclusion. Electronic supplementary information (ESI) available: Details on the molecular dynamics simulation results. Table S1 reports results of the MD trajectories with a single NP at different initial velocities (d1, d2, d3, and d4) (three-dimensional structures and contact residues). Table S2 reports results of the MD trajectories with a couple of NPs at different initial velocities (initial orientations, three-dimensional structures, contact residues and root-mean-square deviations). Table S3 reports root-mean-square fluctuations and divergence of the protein structure with respect to the NMR model. Table S4 describes the average energy of the final complexes. See DOI: 10.1039/c4nr01514b

  10. On the current drive capability of low dimensional semiconductors: 1D versus 2D

    DOE PAGES

    Zhu, Y.; Appenzeller, J.

    2015-10-29

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Lastly, our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  11. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-03-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

  12. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

    PubMed

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-01-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

  13. Targeted synthesis of novel hierarchical sandwiched NiO/C arrays as high-efficiency lithium ion batteries anode

    NASA Astrophysics Data System (ADS)

    Feng, Yangyang; Zhang, Huijuan; Li, Wenxiang; Fang, Ling; Wang, Yu

    2016-01-01

    In this contribution, the novel 2D sandwich-like NiO/C arrays on Ti foil are successfully designed and fabricated for the first time via simple and controllable hydrothermal process. In this strategy, we use green glucose as carbon source and ultrathin Ni(OH)2 nanosheet arrays as precursor for NiO nanoparticles and sacrificial templates for coupled graphitized carbon layers. This advanced sandwiched composite can not only provide large surface area for numerous active sites and continuous contact between active materials and electrolyte, but also protect the active nanoparticles from aggregation, pulverization and peeling off from conductive substrates. Furthermore, the porous structure derived from lots of substances loss under high-temperature calcinations can effectively buffer possible volume expansion and facilitate ion transfer. In this article, sandwiched NiO/C arrays, utilized as anode for LIBs, demonstrated high specific capacity (∼1458 mAh g-1 at 500 mA g-1) and excellent rate performance and cyclablity (∼95.7% retention after 300 cycles).

  14. Simulating nanoparticle transport in 3D geometries with MNM3D

    NASA Astrophysics Data System (ADS)

    Bianco, Carlo; Tosco, Tiziana; Sethi, Rajandrea

    2017-04-01

    The application of NP transport to real cases, such as the design of a field-scale injection or the prediction of the long term fate of nanoparticles (NPs) in the environment, requires the support of mathematical tools to effectively assess the expected NP mobility at the field scale. In general, micro- and nanoparticle transport in porous media is controlled by particle-particle and particle-porous media interactions, which are in turn affected by flow velocity and pore water chemistry. During the injection, a strong perturbation of the flow field is induced around the well, and the NP transport is mainly controlled by the consequent sharp variation of pore-water velocity. Conversely, when the injection is stopped, the particles are transported solely due to the natural flow, and the influence of groundwater geochemistry (ionic strength, IS, in particular) on the particle behaviour becomes predominant. Pore-water velocity and IS are therefore important parameters influencing particle transport in groundwater, and have to be taken into account by the numerical codes used to simulate NP transport. Several analytical and numerical tools have been developed in recent years to model the transport of colloidal particles in simplified geometry and boundary conditions. For instance, the numerical tool MNMs was developed by the authors of this work to simulate colloidal transport in 1D Cartesian and radial coordinates. Only few simulation tools are instead available for 3D colloid transport, and none of them implements direct correlations accounting for variations of groundwater IS and flow velocity. In this work a new modelling tool, MNM3D (Micro and Nanoparticle transport Model in 3D geometries), is proposed for the simulation of injection and transport of nanoparticle suspensions in generic complex scenarios. MNM3D implements a new formulation to account for the simultaneous dependency of the attachment and detachment kinetic coefficients on groundwater IS and velocity

  15. 3-D Vector Flow Estimation With Row-Column-Addressed Arrays.

    PubMed

    Holbek, Simon; Christiansen, Thomas Lehrmann; Stuart, Matthias Bo; Beers, Christopher; Thomsen, Erik Vilain; Jensen, Jorgen Arendt

    2016-11-01

    Simulation and experimental results from 3-D vector flow estimations for a 62 + 62 2-D row-column (RC) array with integrated apodization are presented. A method for implementing a 3-D transverse oscillation (TO) velocity estimator on a 3-MHz RC array is developed and validated. First, a parametric simulation study is conducted, where flow direction, ensemble length, number of pulse cycles, steering angles, transmit/receive apodization, and TO apodization profiles and spacing are varied, to find the optimal parameter configuration. The performance of the estimator is evaluated with respect to relative mean bias ~B and mean standard deviation ~σ . Second, the optimal parameter configuration is implemented on the prototype RC probe connected to the experimental ultrasound scanner SARUS. Results from measurements conducted in a flow-rig system containing a constant laminar flow and a straight-vessel phantom with a pulsating flow are presented. Both an M-mode and a steered transmit sequence are applied. The 3-D vector flow is estimated in the flow rig for four representative flow directions. In the setup with 90° beam-to-flow angle, the relative mean bias across the entire velocity profile is (-4.7, -0.9, 0.4)% with a relative standard deviation of (8.7, 5.1, 0.8)% for ( v x , v y , v z ). The estimated peak velocity is 48.5 ± 3 cm/s giving a -3% bias. The out-of-plane velocity component perpendicular to the cross section is used to estimate volumetric flow rates in the flow rig at a 90° beam-to-flow angle. The estimated mean flow rate in this setup is 91.2 ± 3.1 L/h corresponding to a bias of -11.1%. In a pulsating flow setup, flow rate measured during five cycles is 2.3 ± 0.1 mL/stroke giving a negative 9.7% bias. It is concluded that accurate 3-D vector flow estimation can be obtained using a 2-D RC-addressed array.

  16. Enhanced absorption with quantum dots, metal nanoparticles, and 2D materials

    NASA Astrophysics Data System (ADS)

    Simsek, Ergun; Mukherjee, Bablu; Guchhait, Asim; Chan, Yin Thai

    2016-03-01

    We fabricate and characterize mono- and few- layers of MoS2 and WSe2 on glass and SiO2/Si substrates. PbS quantum dots and/or Au nanoparticles are deposited on the fabricated thin metal dichalcogenide films by controlled drop casting and electron beam evaporation techniques. The reflection spectra of the fabricated structures are measured with a spatially resolved reflectometry setup. Both experimental and numerical results show that surface functionalization with metal nanoparticles can enhance atomically thin transition metal dichalcogenides' absorption and scattering capabilities, however semiconducting quantum dots do not create such effect.

  17. Freestanding two-dimensional Ni(OH)2 thin sheets assembled by 3D nanoflake array as basic building units for supercapacitor electrode materials.

    PubMed

    Song, Dianmei; Zhu, Jikui; Xuan, Liying; Zhao, Chenglan; Xie, Li; Chen, Lingyun

    2018-01-01

    Freestanding two dimensional (2D) porous nanostructures have great potential in electrical energy storage. In the present work, we reported the first synthesis of two-dimensional (2D) β-Ni(OH) 2 thin sheets (CQU-Chen-Ni-O-H-1) assembled by 3D nanoflake array as basic building units under acid condition by direct hydrothermal decomposition of the mixed solution of nickel nitrate (Ni(NO 3 ) 2 ) and acetic acid (CH 3 COOH, AA). The unique 3D nanoflake array assembled mesoporous 2D structures endow the thin sheets with a high specific capacitance of 1.78Fcm -2 (1747.5Fg -1 ) at the current density of 1.02mAcm -2 and good rate capability of 67.4% retain from 1.02 to 10.2mAcm -2 . The corresponding assembled asymmetric supercapacitor (ASC) achieves (CQU-Chen-Ni-O-H-1//active carbon (AC)) a high voltage of 1.8V and an energy density of 23.45Whkg -1 with a maximum power density of 9kWkg -1 , as well as cycability with 93.6% capacitance retention after 10,000 cycles. These results show the mesoporous thin sheets have great potential for SCs and other energy storage devices. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. CdS Nanoparticle-Modified α-Fe2O3/TiO2 Nanorod Array Photoanode for Efficient Photoelectrochemical Water Oxidation.

    PubMed

    Yin, Ruiyang; Liu, Mingyang; Tang, Rui; Yin, Longwei

    2017-09-02

    In this work, we demonstrate a facile successive ionic layer adsorption and reaction process accompanied by hydrothermal method to synthesize CdS nanoparticle-modified α-Fe 2 O 3 /TiO 2 nanorod array for efficient photoelectrochemical (PEC) water oxidation. By integrating CdS/α-Fe 2 O 3 /TiO 2 ternary system, light absorption ability of the photoanode can be effectively improved with an obviously broadened optical-response to visible light region, greatly facilitates the separation of photogenerated carriers, giving rise to the enhancement of PEC water oxidation performance. Importantly, for the designed abnormal type-II heterostructure between Fe 2 O 3 /TiO 2 , the conduction band position of Fe 2 O 3 is higher than that of TiO 2 , the photogenerated electrons from Fe 2 O 3 will rapidly recombine with the photogenerated holes from TiO 2 , thus leads to an efficient separation of photogenerated electrons from Fe 2 O 3 /holes from TiO 2 at the Fe 2 O 3 /TiO 2 interface, greatly improving the separation efficiency of photogenerated holes within Fe 2 O 3 and enhances the photogenerated electron injection efficiency in TiO 2 . Working as the photoanodes of PEC water oxidation, CdS/α-Fe 2 O 3 /TiO 2 heterostucture electrode exhibits improved photocurrent density of 0.62 mA cm - 2 at 1.23 V vs. reversible hydrogen electrode (RHE) in alkaline electrolyte, with an obviously negatively shifted onset potential of 80 mV. This work provides promising methods to enhance the PEC water oxidation performance of the TiO 2 -based heterostructure photoanodes.

  19. 3D Nanochannel Array Platform for High-throughput Cell Manipulation and Nano-electroporation

    NASA Astrophysics Data System (ADS)

    Chang, Lingqian

    Electroporation is one of the most common non-viral methods for gene delivery. Recent progress in gene therapy has offered special opportunities to electroporation for in vitro and in vivo applications. However, conventional bulk electroporation (BEP) inevitably causes serious cell damage and stochastic transfection between cells. Microfluidic electroporation (MEP) has been claimed to provide benign single cell transfection for the last decade. Nevertheless, the intracellular transport in both MEP and BEP systems is highly diffusion-dominant, which prevents precise dose control and high uniformity. In this Ph.D. research, we developed a 3D nanochannel-electroporation (3D NEP) platform for mass cell transfection. A silicon-based nanochannel array (3D NEP) chip was designed and fabricated for cell manipulation and electroporation. The chip, designed as Z-directional microchannel - nanochannel array, was fabricated by clean room techniques including projection photolithography and deep reactive-ion etching (DRIE). The fabricated 3D NEP chip is capable of handling 40,000 cells per 1 cm2, up to 1 million per wafer (100 mm diameter). High-throughput cell manipulation technologies were investigated for precise alignment of individual cells to the nanochannel array, a key step for NEP to achieve dose control. We developed three techniques for cell trapping in this work. (1) Magnetic tweezers (MTs) were integrated on the chip to remotely control cells under a programmed magnetic field. (2) A positive dielectrophoresis (pDEP) power system was built as an alternative to trap cells onto the nanochannel array using DEP force. (3) A novel yet simple 'dipping-trap' method was used to rapidly trap cells onto a nanochannel array, aligned by a micro-cap array pattern on the 3D NEP chip, which eventually offered 70 - 90 % trapping efficiency and 90 % specificity. 3D NEP platforms were assembled for cell transfection based on the Si-based nanochannel array chip and cell manipulation

  20. SU-E-T-82: A Study On Enhanced Dynamic Wedge (EDW) Dosimetry Using 2D Seven29 Ion Chamber Array Detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Syam; Aparna

    2015-06-15

    Purpose: To study the dosimetric properties of Enhanced Dynamic Wedge (EDW) using PTW Seven29 ion chamber array Methods: PTW Seven29 ion chamber array and Solid Water phantoms for different depths were used for the study. The study was carried out in Varian Clinac ix with photon energies, 6MV & 15MV. Primarily the solid water phantoms with the 2D array were scanned using a CT scanner (GE Optima 580) at different depths. These scanned images were used for EDW planning in an Eclipse treatment planning system (version 10). Planning was done for different wedge angles and for different depths for 6MVmore » & 15MV. A dose of 100 CGy was delivered in each cases. For each delivery, calculated the Monitoring Unit (MU) required. Same set-up was created before delivering the plans in Varian Clinac-ix. For each clinically relevant depth and for different wedge angles, the same MU was delivered as calculated. Different wedged dose distributions where reconstructed from the measured 2D array data using the in-house developed excel program. Results: It is observed that the shoulder like region in the profile which reduces as depth increases. For the same depth and energy, the percentage difference between planned and measured dose is lesser than 3%. For smaller wedge angles, the percentage difference is found to be greater than 3% for the largest wedge angle. Standard deviation between measured doses at shoulder region for planned and measured profiles is 0.08 and 0.02 respectively. Standard deviations between planned and measured wedge factors for different depths (2.5cm, 5cm, 10cm, and 15cm) are (0.0021, 0.0007, 0.0050, 0.0001) for 6MV and (0.0024, 0.0191, 0.0013, 0.0005) for 15MV respectively. Conclusion: The 2D Seven29 ion chamber array is a good tool for the Enhanced Dynamic Wedge (EDW) dosimetry.« less

  1. Effect of metallic silver nanoparticles on the alignment and relaxation behaviour of liquid crystalline material in smectic C* phase

    NASA Astrophysics Data System (ADS)

    Vimal, Tripti; Kumar Gupta, Swadesh; Katiyar, Rohit; Srivastava, Atul; Czerwinski, Michal; Krup, Katarzyna; Kumar, Sandeep; Manohar, Rajiv

    2017-09-01

    The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro-optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other material parameters, significantly. A noteworthy change in DC conductivity articulates our proposed idea of the formation of 2D array of NPs perpendicular to the direction of rubbing. This comprehensive study endorses the importance of dopant concentration in modifying the properties of the host LC material.

  2. Ordering nanoparticles with polymer brushes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

    Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

  3. Ordering nanoparticles with polymer brushes

    NASA Astrophysics Data System (ADS)

    Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

    2017-12-01

    Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a single layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. An interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.

  4. Ordering nanoparticles with polymer brushes

    DOE PAGES

    Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

    2017-12-08

    Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

  5. Quantitative 3D evolution of colloidal nanoparticle oxidation in solution

    DOE PAGES

    Sun, Yugang; Zuo, Xiaobing; Sankaranarayanan, Subramanian K. R. S.; ...

    2017-04-21

    Real-time tracking three-dimensional (3D) evolution of colloidal nanoparticles in solution is essential for understanding complex mechanisms involved in nanoparticle growth and transformation. We simultaneously use time-resolved small-angle and wide-angle x-ray scattering to monitor oxidation of highly uniform colloidal iron nanoparticles, enabling the reconstruction of intermediate 3D morphologies of the nanoparticles with a spatial resolution of ~5 Å. The in-situ probing combined with large-scale reactive molecular dynamics simulations reveals the transformational details from the solid metal nanoparticles to hollow metal oxide nanoshells via nanoscale Kirkendall process, for example, coalescence of voids upon their growth, reversing of mass diffusion direction depending onmore » crystallinity, and so forth. In conclusion, our results highlight the complex interplay between defect chemistry and defect dynamics in determining nanoparticle transformation and formation.« less

  6. Quantitative 3D evolution of colloidal nanoparticle oxidation in solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sun, Yugang; Zuo, Xiaobing; Sankaranarayanan, Subramanian K. R. S.

    Real-time tracking three-dimensional (3D) evolution of colloidal nanoparticles in solution is essential for understanding complex mechanisms involved in nanoparticle growth and transformation. We simultaneously use time-resolved small-angle and wide-angle x-ray scattering to monitor oxidation of highly uniform colloidal iron nanoparticles, enabling the reconstruction of intermediate 3D morphologies of the nanoparticles with a spatial resolution of ~5 Å. The in-situ probing combined with large-scale reactive molecular dynamics simulations reveals the transformational details from the solid metal nanoparticles to hollow metal oxide nanoshells via nanoscale Kirkendall process, for example, coalescence of voids upon their growth, reversing of mass diffusion direction depending onmore » crystallinity, and so forth. In conclusion, our results highlight the complex interplay between defect chemistry and defect dynamics in determining nanoparticle transformation and formation.« less

  7. Ambient Vehicular Noise recorded on a 2D Distributed Fiber Optic Sensing Array :Applications to Permafrost Thaw Detection and Imaging

    NASA Astrophysics Data System (ADS)

    Ajo Franklin, J. B.; Lindsey, N.; Wagner, A. M.; Dou, S.; Martin, E. R.; Ekblaw, I.; Ulrich, C.; James, S. R.; Freifeld, B. M.; Daley, T. M.

    2016-12-01

    Distributed Acoustic Sensing (DAS) is a recently developed technique that allows the spatially dense ( 1m) continuous recording of seismic signals on long strands of commercial fiber optic cables. The availability of continuous recording on dense arrays offers unique possibilities for long-term timelapse monitoring of environmental processes in arctic environments. In the absence of a repeatable semi-permanent seismic source, the use of ambient surface wave noise from infrastructure use (e.g. moving vehicles) for seismic imaging allows tomographic monitoring of evolving subsurface systems. Challenges in such scenarios include (1) the processing requirements for dense (1000+ channel) arrays recording weeks to months of seismic data, (2) appropriate methods to retrieve empirical noise correlation functions (NCFs) in environments with non-optimal array geometries and both coherent as well as incoherent noise, and (3) semi-automated approaches to invert timelapse NCFs for near-surface soil properties.We present an exploratory study of data from a sparse 2D DAS array acquisition on 4000 linear meters of trenched fiber deployed in 10 crossing profiles. The dataset, collected during July and August of 2016, covers a zone of permafrost undergoing a controlled thaw induced by an array of resistive heaters. The site, located near a heavily used road, has a high level of infrastructure noise but exhibits distance-dependent variation in both noise amplitude and spectrum. We apply seismic interferometry to retrieve the empirical NCF across array subsections, and use collocated geophone and broadband sensors to measure the NCF against the true impulse response function of the medium. We demonstrate that the combination of vehicle tracking and data windowing allows improved reconstruction of stable NCFs appropriate for dispersion analysis and inversion. We also show both spatial and temporal patterns of background noise at the site using 2D beamforming and spectral analysis. Our

  8. A Novel Crosstalk Suppression Method of the 2-D Networked Resistive Sensor Array

    PubMed Central

    Wu, Jianfeng; Wang, Lei; Li, Jianqing; Song, Aiguo

    2014-01-01

    The 2-D resistive sensor array in the row–column fashion suffered from the crosstalk problem for parasitic parallel paths. Firstly, we proposed an Improved Isolated Drive Feedback Circuit with Compensation (IIDFCC) based on the voltage feedback method to suppress the crosstalk. In this method, a compensated resistor was specially used to reduce the crosstalk caused by the column multiplexer resistors and the adjacent row elements. Then, a mathematical equivalent resistance expression of the element being tested (EBT) of this circuit was analytically derived and verified by the circuit simulations. The simulation results show that the measurement method can greatly reduce the influence on the EBT caused by parasitic parallel paths for the multiplexers' channel resistor and the adjacent elements. PMID:25046011

  9. Fabrication of Thickness-Controllable Micropatterned Polyelectrolyte-Film/Nanoparticle Surfaces by Using the Plasma Oxidation Method.

    PubMed

    Zhu, Chun-Tao; Ma, Sheng-Hua; Zhang, Ying; Wang, Xue-Jing; Lv, Peng; Han, Xiao-Jun

    2016-04-05

    We have demonstrated a novel way to form thickness-controllable polyelectrolyte-film/nanoparticle patterns by using a plasma etching technique to form, first, a patterned self-assembled monolayer surface, followed by layer-by-layer assembly of polyelectrolyte-films/nanoparticles. Octadecyltrimethoxysilane (ODS) and (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayers (SAMs) were used for polyelectrolyte-film and nanoparticle patterning, respectively. The resolution of the proposed patterning method can easily reach approximately 2.5 μm. The height of the groove structure was tunable from approximately 2.5 to 150 nm. The suspended lipid membrane across the grooves was fabricated by incubating the patterned polyelectrolyte groove arrays in solutions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs). The method demonstrated here reveals a new path to create patterned 2D or 3D structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Computationally Efficient 2D DOA Estimation with Uniform Rectangular Array in Low-Grazing Angle.

    PubMed

    Shi, Junpeng; Hu, Guoping; Zhang, Xiaofei; Sun, Fenggang; Xiao, Yu

    2017-02-26

    In this paper, we propose a computationally efficient spatial differencing matrix set (SDMS) method for two-dimensional direction of arrival (2D DOA) estimation with uniform rectangular arrays (URAs) in a low-grazing angle (LGA) condition. By rearranging the auto-correlation and cross-correlation matrices in turn among different subarrays, the SDMS method can estimate the two parameters independently with one-dimensional (1D) subspace-based estimation techniques, where we only perform difference for auto-correlation matrices and the cross-correlation matrices are kept completely. Then, the pair-matching of two parameters is achieved by extracting the diagonal elements of URA. Thus, the proposed method can decrease the computational complexity, suppress the effect of additive noise and also have little information loss. Simulation results show that, in LGA, compared to other methods, the proposed methods can achieve performance improvement in the white or colored noise conditions.

  11. Computationally Efficient 2D DOA Estimation with Uniform Rectangular Array in Low-Grazing Angle

    PubMed Central

    Shi, Junpeng; Hu, Guoping; Zhang, Xiaofei; Sun, Fenggang; Xiao, Yu

    2017-01-01

    In this paper, we propose a computationally efficient spatial differencing matrix set (SDMS) method for two-dimensional direction of arrival (2D DOA) estimation with uniform rectangular arrays (URAs) in a low-grazing angle (LGA) condition. By rearranging the auto-correlation and cross-correlation matrices in turn among different subarrays, the SDMS method can estimate the two parameters independently with one-dimensional (1D) subspace-based estimation techniques, where we only perform difference for auto-correlation matrices and the cross-correlation matrices are kept completely. Then, the pair-matching of two parameters is achieved by extracting the diagonal elements of URA. Thus, the proposed method can decrease the computational complexity, suppress the effect of additive noise and also have little information loss. Simulation results show that, in LGA, compared to other methods, the proposed methods can achieve performance improvement in the white or colored noise conditions. PMID:28245634

  12. Dextran and Polymer Polyethylene Glycol (PEG) Coating Reduce Both 5 and 30 nm Iron Oxide Nanoparticle Cytotoxicity in 2D and 3D Cell Culture

    PubMed Central

    Yu, Miao; Huang, Shaohui; Yu, Kevin Jun; Clyne, Alisa Morss

    2012-01-01

    Superparamagnetic iron oxide nanoparticles are widely used in biomedical applications, yet questions remain regarding the effect of nanoparticle size and coating on nanoparticle cytotoxicity. In this study, porcine aortic endothelial cells were exposed to 5 and 30 nm diameter iron oxide nanoparticles coated with either the polysaccharide, dextran, or the polymer polyethylene glycol (PEG). Nanoparticle uptake, cytotoxicity, reactive oxygen species (ROS) formation, and cell morphology changes were measured. Endothelial cells took up nanoparticles of all sizes and coatings in a dose dependent manner, and intracellular nanoparticles remained clustered in cytoplasmic vacuoles. Bare nanoparticles in both sizes induced a more than 6 fold increase in cell death at the highest concentration (0.5 mg/mL) and led to significant cell elongation, whereas cell viability and morphology remained constant with coated nanoparticles. While bare 30 nm nanoparticles induced significant ROS formation, neither 5 nm nanoparticles (bare or coated) nor 30 nm coated nanoparticles changed ROS levels. Furthermore, nanoparticles were more toxic at lower concentrations when cells were cultured within 3D gels. These results indicate that both dextran and PEG coatings reduce nanoparticle cytotoxicity, however different mechanisms may be important for different size nanoparticles. PMID:22754315

  13. Experimental results for a prototype 3-D acoustic imaging system using an ultra-sparse planar array

    NASA Astrophysics Data System (ADS)

    Impagliazzo, John M.; Chiang, Alice M.; Broadstone, Steven R.

    2002-11-01

    A handheld high resolution sonar has been under development to provide Navy Divers with a 3-D acoustic imaging system for mine reconnaissance. An ultra-sparse planar array, consisting of 121 1 mm x1 mm, 2 MHz elements, was fabricated to provide 3-D acoustic images. The array was 10 cm x10 cm. A full array at this frequency with elements at half-wavelength spacing would consist of 16384 elements. The first phase of testing of the planar array was completed in September 2001 with the characterization of the array in the NUWC Acoustic Test Facility (ATF). The center frequency was 2 MHz with a 667 kHz bandwidth. A system-level technology demonstration will be conducted in July 2002 with a real-time beamformer and near real-time 3-D imaging software. The demonstration phase consists of imaging simple targets at a range of 3 m in the ATF. Experimental results obtained will be reported on. [Work supported by the Defense Applied Research Project Agency, Advance Technology Office, Dr. Theo Kooij, Program Manager.

  14. Poster - Thurs Eve-09: Evaluation of a commercial 2D ion-chamber array for intensity modulated radiation therapy dose measurements.

    PubMed

    Mei, X; Bracken, G; Kerr, A

    2008-07-01

    Experimental verification of calculated dose from a treatment planning system is often essential for quality assurance (QA) of intensity modulated radiation therapy (IMRT). Film dosimetry and single ion chamber measurements are commonly used for IMRT QA. Film dosimetry has very good spatial resolution, but is labor intensive and absolute dose is not reliable. Ion chamber measurements are still required for absolute dose after measurements using films. Dosimeters based on 2D detector arrays that can measure 2D dose in real-time are gaining wider use. These devices provide a much easier and reliable tool for IMRT QA. We report the evaluation of a commercial 2D ion chamber array, including its basic performance characteristics, such as linearity, reproducibility and uniformity of relative ion chamber sensitivities, and comparisons between measured 2D dose and calculated dose with a commercial treatment planning system. Our analysis shows this matrix has excellent linearity and reproducibility, but relative sensitivities are tilted such that the +Y region is over sensitive, while the -Y region is under sensitive. Despite this behavior, our results show good agreement between measured 2D dose profiles and Eclipse planned data for IMRT test plans and a few verification plans for clinical breast field-in-field plans. The gamma values (3% or 3 mm distance-to-agreement) are all less than 1 except for one or two pixels at the field edge This device provides a fast and reliable stand-alone dosimeter for IMRT QA. © 2008 American Association of Physicists in Medicine.

  15. Effect of the Fabrication Parameters of the Nanosphere Lithography Method on the Properties of the Deposited Au-Ag Nanoparticle Arrays

    PubMed Central

    Liu, Jing; Chen, Chaoyang; Yang, Guangsong; Chen, Yushan; Yang, Cheng-Fu

    2017-01-01

    The nanosphere lithography (NSL) method can be developed to deposit the Au-Ag triangle hexagonal nanoparticle arrays for the generation of localized surface plasmon resonance. Previously, we have found that the parameters used to form the NSL masks and the physical methods required to deposit the Au-Ag thin films had large effects on the geometry properties of the nanoparticle arrays. Considering this, the different parameters used to grow the Au-Ag triangle hexagonal nanoparticle arrays were investigated. A single-layer NSL mask was formed by using self-assembly nano-scale polystyrene (PS) nanospheres with an average radius of 265 nm. At first, the concentration of the nano-scale PS nanospheres in the solution was set at 6 wt %. Two coating methods, drop-coating and spin-coating, were used to coat the nano-scale PS nanospheres as a single-layer NSL mask. From the observations of scanning electronic microscopy (SEM), we found that the matrixes of the PS nanosphere masks fabricated by using the drop-coating method were more uniform and exhibited a smaller gap than those fabricated by the spin-coating method. Next, the drop-coating method was used to form the single-layer NSL mask and the concentration of nano-scale PS nanospheres in a solution that was changed from 4 to 10 wt %, for further study. The SEM images showed that when the concentrations of PS nanospheres in the solution were 6 and 8 wt %, the matrixes of the PS nanosphere masks were more uniform than those of 4 and 10 wt %. The effects of the one-side lifting angle of substrates and the vaporization temperature for the solvent of one-layer self-assembly PS nanosphere thin films, were also investigated. Finally, the concentration of the nano-scale PS nanospheres in the solution was set at 8 wt % to form the PS nanosphere masks by the drop-coating method. Three different physical deposition methods, including thermal evaporation, radio-frequency magnetron sputtering, and e-gun deposition, were used to

  16. Effect of the Fabrication Parameters of the Nanosphere Lithography Method on the Properties of the Deposited Au-Ag Nanoparticle Arrays.

    PubMed

    Liu, Jing; Chen, Chaoyang; Yang, Guangsong; Chen, Yushan; Yang, Cheng-Fu

    2017-04-03

    The nanosphere lithography (NSL) method can be developed to deposit the Au-Ag triangle hexagonal nanoparticle arrays for the generation of localized surface plasmon resonance. Previously, we have found that the parameters used to form the NSL masks and the physical methods required to deposit the Au-Ag thin films had large effects on the geometry properties of the nanoparticle arrays. Considering this, the different parameters used to grow the Au-Ag triangle hexagonal nanoparticle arrays were investigated. A single-layer NSL mask was formed by using self-assembly nano-scale polystyrene (PS) nanospheres with an average radius of 265 nm. At first, the concentration of the nano-scale PS nanospheres in the solution was set at 6 wt %. Two coating methods, drop-coating and spin-coating, were used to coat the nano-scale PS nanospheres as a single-layer NSL mask. From the observations of scanning electronic microscopy (SEM), we found that the matrixes of the PS nanosphere masks fabricated by using the drop-coating method were more uniform and exhibited a smaller gap than those fabricated by the spin-coating method. Next, the drop-coating method was used to form the single-layer NSL mask and the concentration of nano-scale PS nanospheres in a solution that was changed from 4 to 10 wt %, for further study. The SEM images showed that when the concentrations of PS nanospheres in the solution were 6 and 8 wt %, the matrixes of the PS nanosphere masks were more uniform than those of 4 and 10 wt %. The effects of the one-side lifting angle of substrates and the vaporization temperature for the solvent of one-layer self-assembly PS nanosphere thin films, were also investigated. Finally, the concentration of the nano-scale PS nanospheres in the solution was set at 8 wt % to form the PS nanosphere masks by the drop-coating method. Three different physical deposition methods, including thermal evaporation, radio-frequency magnetron sputtering, and e-gun deposition, were used to

  17. Using surface lattice resonances to engineer nonlinear optical processes in metal nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Huttunen, Mikko J.; Rasekh, Payman; Boyd, Robert W.; Dolgaleva, Ksenia

    2018-05-01

    Collective responses of localized surface plasmon resonances, known as surface lattice resonances (SLRs) in metal nanoparticle arrays, can lead to high quality factors (˜100 ), large local-field enhancements, and strong light-matter interactions. SLRs have found many applications in linear optics, but little work of the influence of SLRs on nonlinear optics has been reported. Here we show how SLRs could be utilized to enhance nonlinear optical interactions. We devote special attention to the sum-frequency, difference-frequency, and third-harmonic generation processes because of their potential for the realization of novel sources of light. We also demonstrate how such arrays could be engineered to enhance higher-order nonlinear optical interactions through cascaded nonlinear processes. In particular, we demonstrate how the efficiency of third-harmonic generation could be engineered via cascaded second-order responses.

  18. Metal-semiconductor phase transition of order arrays of VO2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Lopez, Rene; Suh, Jae; Feldman, Leonard; Haglund, Richard

    2004-03-01

    The study of solid-state phase transitions at nanometer length scales provides new insights into the effects of material size on the mechanisms of structural transformations. Such research also opens the door to new applications, either because materials properties are modified as a function of particle size, or because the nanoparticles interact with a surrounding matrix material, or with each other. In this paper, we describe the formation of vanadium dioxide nanoparticles in silicon substrates by pulsed laser deposition of ion beam lithographically selected sites and thermal processing. We observe the collective behavior of 50 nm diameter VO2 oblate nanoparticles, 10 nm high, and ordered in square arrays with arbitrary lattice constant. The metal-semiconductor-transition of the VO2 precipitates shows different features in each lattice spacing substrate. The materials are characterized by electron microscopy, x-ray diffraction, Rutherford backscattering. The features of the phase transition are studied via infrared optical spectroscopy. Of particular interest are the enhanced scattering and the surface plasmon resonance when the particles reach the metallic state. This resonance amplifies the optical contrast in the range of near-infrared optical communication wavelengths and it is altered by the particle-particle coupling as in the case of noble metals. In addition the VO2 nanoparticles exhibit sharp transitions with up to 50 K of hysteresis, one of the largest values ever reported for this transition. The optical properties of the VO2 nanoarrays are correlated with the size of the precipitates and their inter-particle distance. Nonlinear and ultra fast optical measurements have shown that the transition is the fastest known solid-solid transformation. The VO2 nanoparticles show the same bulk property, transforming in times shorter than 150 fs. This makes them remarkable candidates for ultrafast optical and electronic switching applications.

  19. Droplet Array-Based 3D Coculture System for High-Throughput Tumor Angiogenesis Assay.

    PubMed

    Du, Xiaohui; Li, Wanming; Du, Guansheng; Cho, Hansang; Yu, Min; Fang, Qun; Lee, Luke P; Fang, Jin

    2018-03-06

    Angiogenesis is critical for tumor progression and metastasis, and it progresses through orchestral multicellular interactions. Thus, there is urgent demand for high-throughput tumor angiogenesis assays for concurrent examination of multiple factors. For investigating tumor angiogenesis, we developed a microfluidic droplet array-based cell-coculture system comprising a two-layer polydimethylsiloxane chip featuring 6 × 9 paired-well arrays and an automated droplet-manipulation device. In each droplet-pair unit, tumor cells were cultured in 3D in one droplet by mixing cell suspensions with Matrigel, and in the other droplet, human umbilical vein endothelial cells (HUVECs) were cultured in 2D. Droplets were fused by a newly developed fusion method, and tumor angiogenesis was assayed by coculturing tumor cells and HUVECs in the fused droplet units. The 3D-cultured tumor cells formed aggregates harboring a hypoxic center-as observed in vivo-and secreted more vascular endothelial growth factor (VEGF) and more strongly induced HUVEC tubule formation than did 2D-cultured tumor cells. Our single array supported 54 assays in parallel. The angiogenic potentials of distinct tumor cells and their differential responses to antiangiogenesis agent, Fingolimod, could be investigated without mutual interference in a single array. Our droplet-based assay is convenient to evaluate multicellular interaction in high throughput in the context of tumor sprouting angiogenesis, and we envision that the assay can be extensively implementable for studying other cell-cell interactions.

  20. ZnO/perovskite core–shell nanorod array based monolithic catalysts with enhanced propane oxidation and material utilization efficiency at low temperature

    DOE PAGES

    Wang, Sibo; Ren, Zheng; Song, Wenqiao; ...

    2015-04-24

    Here, a hydrothermal strategy combined with colloidal deposition synthesis was successfully used to grow ZnO/perovskite (LaBO 3, B=Mn, Co, Ni) core-shell nanorod arrays within three dimensional (3-D) honeycomb cordierite substrates. A facile sonication assisted colloidal wash coating process is able to coat a uniformly dispersed perovskite nanoparticles onto the large scale ZnO nanorod arrays rooted on the channel surfaces of the 3D cordierite substrate achieved by hydrothermal synthesis. Compared to traditional wash-coated perovskite catalysts, an enhanced catalytic performance was observed for propane oxidation with 25°C lower light-off temperature than wash-coated perovskite catalyst of similar LaMnO 3 loading (4.3mg). Temperature programmedmore » reduction and desorption under H 2 and O 2 atmosphere, respectively, were used to study the reducibility and oxygen activity of these core-shell nanorod arrays based monolithic catalysts, revealing a catalytic activity sequence of LaCoO 3>LaMnO 3>La 2NiO 4 at the initial stage of catalytic reaction. The good dispersion and size control in La-based perovskite nanoparticles and their interfaces to ZnO nanorod arrays support may contribute to the enhancement of catalytic performance. Lastly, this work may provide a new type of Pt-group metals (PGM) free catalysts with improved catalytic performance for hydrocarbon oxidations at low temperatures.« less

  1. Analysis and Optimization of a Novel 2-D Magnet Array with Gaps and Staggers for a Moving-Magnet Planar Motor

    PubMed Central

    Chen, Xuedong; Zeng, Lizhan

    2018-01-01

    This paper presents a novel 2-D magnet array with gaps and staggers, which is especially suitable for magnetically levitated planar motor with moving magnets. The magnetic flux density distribution is derived by Fourier analysis and superposition. The influences of gaps and staggers on high-order harmonics and flux density were analyzed, and the optimized design is presented. Compared with the other improved structures based on traditional Halbach magnet arrays, the proposed design has the lowest high-order harmonics percentage, and the characteristics of flux density meet the demand of high acceleration in horizontal directions. It is also lightweight and easy to manufacture. The proposed magnet array was built, and the calculation results have been verified with experiment. PMID:29300323

  2. Numerical Investigations of the Thermal, Pressure and Size Effects on 2D Spin Crossover Nanoparticles

    NASA Astrophysics Data System (ADS)

    Harlé, C.; Allal, S. E.; Sohier, D.; Dufaud, T.; Caballero, R.; de Zela, F.; Dahoo, P. R.; Boukheddaden, K.; Linares, J.

    2017-12-01

    In the framework of the Ising-like model, the thermal and pressure effects on the spin crossover systems are evaluated through two-states fictitious spin operators σ with eigenvalues 𝜎 = -1 and 𝜎 = +1 respectively associated with the low-spin (LS) and highspin (HS) states of each spin-crossover (SCO) molecule. Based on each configurational state, the macroscopic SCO system, is described by the following variables: m=Σ σi, s=Σ σi σj and c=Σ σk standing respectively for the total magnetization, the short-range correlations and surface magnetization. To solve this problem, we first determine the density of macrostates d[m][s][c], giving the number of microscopic configurations with the same m, s and c values. In this contribution, two different ways have been performed to calculate this important quantity: (i) the entropic sampling method, based on Monte Carlo simulations and (ii) a new algorithm based on specific dynamic programming. These two methods were tested on the 2D SCO nanoparticles for which, we calculated the average magnetization < σ> taking into account for short-, long-range interactions as well as for the interaction between surface molecules with their surrounding matrix. We monitored the effect of the pressure, temperature and size on the properties of the SCO nanoparticles.

  3. A new water-equivalent 2D plastic scintillation detectors array for the dosimetry of megavoltage energy photon beams in radiation therapy.

    PubMed

    Guillot, Mathieu; Beaulieu, Luc; Archambault, Louis; Beddar, Sam; Gingras, Luc

    2011-12-01

    The objective of this work is to present a new 2D plastic scintillation detectors array (2D-PSDA) designed for the dosimetry of megavoltage (MV) energy photon beams in radiation therapy and to characterize its basic performance. We developed a 2D detector array consisting of 781 plastic scintillation detectors (PSDs) inserted into a plane of a water-equivalent phantom. The PSDs were distributed on a 26 × 26 cm(2) grid, with an interdetector spacing of 10 mm, except for two perpendicular lines centered on the detection plane, where the spacing was 5 mm. Each PSD was made of a 1 mm diameter by 3 mm long cylindrical polystyrene scintillating fiber coupled to a clear nonscintillating plastic optical fiber. All of the light signals emitted by the PSDs were read simultaneously with an optical system at a rate of one measurement per second. We characterized the performance of the optical system, the angular dependency of the device, and the perturbation of dose distributions caused by the hundreds of PSDs inserted into the phantom. We also evaluated the capacity of the system to monitor complex multileaf collimator (MLC) sequences such as those encountered in step-and-shoot intensity modulated radiation therapy (IMRT) plans. We compared our results with calculations performed by a treatment planning system and with measurements taken with a 2D ionization chamber array and with a radiochromic film. The detector array that we developed allowed us to measure doses with an average precision of better than 1% for cumulated doses equal to or greater than 6.3 cGy. Our results showed that the dose distributions produced by the 6-MV photon beam are not perturbed (within ±1.1%) by the presence of the hundreds of PSDs located into the phantom. The results also showed that the variations in the beam incidences have little effect on the dose response of the device. For all incidences tested, the passing rates of the gamma tests between the 2D-PSDA and the treatment planning

  4. Enhanced photocatalytic performance from NiS/TiO2 p-n heterojunction nanosheet arrays

    NASA Astrophysics Data System (ADS)

    Qian, Long-Long; Li, Yan; Li, Jian-feng; Wang, Cheng-Wei

    2018-05-01

    A novel p-n heterostructural film photocatalyst of oriented NiS/TiO2 nanosheet arrays were designed and successfully fabricated via a simple two-step hydrothermal process, and its photodegradation activities of methyl orange (MO) were detailedly investigated. Combining p-type NiS nanoparticles with n-type TiO2 nanosheets to construct distributed p-n heterojunctions, the absorption edge of NiS/TiO2 red-shifted to about 471 nm and its photoresponse in visible range significantly enhanced. Compared with pure TiO2 nanosheet arrays (NSAs), the assembled NiS/TiO2 p-n heterostructural arrays with 0.003 M NiS in hydrothermal precursor solution showed an optimal degradation rate of k = 0.7368 h-1 for MO, achieving 76.3% photocatalytic efficiency within 120 min, which is about 2.34 times higher than that of pure TiO2 nanosheet arrays (k = 0.3144 h-1). Such enhanced photocatalytic activities should be attributed to both the high efficiency of photogenerated charge separation by the built-in electric field at interfaces of NiS-TiO2 and the oriented thin nanosheet structures for smoothly charge transportation for redox reactions at surfaces of NiS/TiO2.

  5. 3D MHD Simulations of Radial Wire Array Z-pinches

    NASA Astrophysics Data System (ADS)

    Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V.; Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P.

    2009-01-01

    Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 μs) and SPHINX (4 MA, 700 ns)[1] facilities have shown the relatively high level of scalability of the Radial Wire Array Z-pinches. These configurations where the wires stretch radially outwards from a central cathode offer numerous advantages over standard cylindrical arrays. In particular, imploding in a very stable and compact way, they seem suitable for coupling to small scale hohlraums. Making use of the 3D resistive magneto-hydrodynamic code GORGON[2] developed at Imperial College, the dynamic of the radial wire arrays is investigated. Influence of the cathode hotspots and wires angle on the x-ray emissions is also discussed. Comparison with experiments is offered to validate the numerical studies.

  6. Conductive atomic force microscopy study of the photoexcitation effect on resistive switching in ZrO2(Y) films with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Novikov, A. S.; Filatov, D. O.; Antonov, D. A.; Antonov, I. N.; Shenina, M. E.; Gorshkov, O. N.

    2018-03-01

    We report on the experimental observation of the effect of optical excitation on resistive switching in ultrathin ZrO2(Y) films with single-layered arrays of Au nanoparticles. The samples were prepared by depositing nanometer-thick Au films sandwiched between two ZrO2(Y) layers by magnetron sputtering followed by annealing. Resistive switching was studied by conductive atomic force microscopy by measuring cyclic current-voltage curves of a probe-to-sample contact. The contact area was illuminated by radiation of a semiconductor laser diode with the wavelength corresponding to the plasmon resonance in an Au nanoparticle array. The enhancement of the hysteresis in cyclic current-voltage curves due to bipolar resistive switching under illumination was observed. The effect was attributed to heating of Au nanoparticles due to plasmonic optical absorption and a plasmon resonance, which enhances internal photoemission of electrons from the Fermi level in Au nanoparticles into the conduction band of ZrO2(Y). Both factors promote resistive switching in a ZrO2(Y) matrix.

  7. 2-D eddy resolving simulations of flow past a circular array of cylindrical plant stems

    NASA Astrophysics Data System (ADS)

    Chang, Kyoungsik; Constantinescu, George; Park, Sanghyun

    2018-04-01

    In the present study, 2-D large eddy simulations (LES) are conducted for flow past a porous circular array with a solid volume fraction (SVF) of 8.8%, 15.4% and 21.5%. Such simulations are relevant to understanding flow in natural streams and channels containing patches of emerged vegetation. In the simulations discussed in the paper, the porous cylinder of diameter D contains a variable number of identical solid circular cylinders (rigid plant stems) of diameter d = 0.048 D. Most of the simulations are conducted at a Reynolds number of 2 100 based on the diameter D and the velocity of the steady uniform incoming flow. Though in all cases wake billows are shed in the regions where the separated shear layers (SSLs) forming on the sides of the porous cylinder interact, the effect of these wake billows on the mean drag is different. While in the high SVF case (21.5%), the total drag force oscillates quasi-regularly in time, similar to the canonical case of a large solid cylinder, in the cases with a lower SVF the shedding of the wake billows takes place sufficiently far from the cylinder such that the unsteady component of the total drag force is negligible. The mean amplitude of the oscillations of the drag force on the individual cylinders is the largest in a streamwise band centered around the center of the porous cylinder, where the wake to wake interactions are the strongest. In all cases the maximum drag force on the individual cylinders is the largest for the cylinders directly exposed to the flow, but this force is always smaller than the one induced on a small isolated cylinder and the average magnitude of the force on the cylinders directly exposed to the flow decreases monotonically with the increase in the SVF. Predictions of the global drag coefficients, Strouhal numbers associated with the wake vortex shedding and individual forces on the cylinders in the array from the present LES are in very good agreement with those of 2-D direct numerical simulations

  8. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

    NASA Astrophysics Data System (ADS)

    Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

    2013-10-01

    Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

  9. Biocompatible nanoparticles sensing the matrix metallo-proteinase 2 for the on-demand release of anticancer drugs in 3D tumor spheroids.

    PubMed

    Cantisani, Marco; Guarnieri, Daniela; Biondi, Marco; Belli, Valentina; Profeta, Martina; Raiola, Luca; Netti, Paolo A

    2015-11-01

    The balance between dose-dependent tolerability, effectiveness and toxicity of systemically administered antitumor drugs is extremely delicate. This issue highlights the striking need for targeted release of chemotherapeutic drugs within tumors. In this work, a smart strategy of drug targeting to tumors relying upon biodegradable/biocompatible nanoparticles releasing cytotoxic drugs after sensing physiological variations intrinsic to the very nature of tumor tissues is exploited. Here, the well-known over-expression of matrix metallo-proteinase 2 (MMP2) enzyme in tumors has been chosen as a trigger for the release of a cytotoxic drug. Nanoparticles made up of a biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA)--block--polyethylene glycol (PEG) copolymer (namely PELGA), blended with a tumor-activated prodrug (TAP) composed of a MMP2-sensitive peptide bound to doxorubicin (Dox) and to PLGA chain have been produced. The obtained devices are able to release Dox specifically upon MMP2 cleavage of the TAP. More interestingly, they can sense the differences in the expression levels of endogenous MMP2 protein, thus modulating drug penetration within a three-dimensional (3D) tumor spheroid matrix, accordingly. Therefore, the proposed nanoparticles hold promise as a useful tool for in vivo investigations aimed at an improved therapeutic efficacy of the conjugated drug payload. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. A microfabricated platform with hydrogel arrays for 3D mechanical stimulation of cells.

    PubMed

    Liu, Haijiao; Usprech, Jenna; Sun, Yu; Simmons, Craig A

    2016-04-01

    Cellular microenvironments present cells with multiple stimuli, including not only soluble biochemical and insoluble matrix cues but also mechanical factors. Biomaterial array platforms have been used to combinatorially and efficiently probe and define two-dimensional (2D) and 3D microenvironmental cues to guide cell functions for tissue engineering applications. However, there are few examples of array platforms that include dynamic mechanical forces, particularly to enable stretching of 3D cell-seeded biomaterials, which is relevant to engineering connective and cardiovascular tissues. Here we present a deformable membrane platform that enables 3D dynamic mechanical stretch of arrayed biomaterial constructs. Cell-seeded polyethylene glycol norbornene (PEG-NB) hydrogels were bound to miniaturized deformable membranes via a thiol-ene reaction with off-stoichiometry thiol-ene based polydimethylsiloxane (OSTE-PDMS) as the membrane material. Bonding to OSTE-PDMS enabled the 3D hydrogel microconstructs to be cyclically deformed and stretched by the membrane. As a first demonstration, human mesenchymal stromal cells (MSCs) embedded in PEG-NB were stretched for several days. They were found to be viable, spread in the 3D hydrogels, and exhibited a contractile myofibroblast phenotype when exposed to dynamic 3D mechanical deformation. This platform, which is readily scalable to larger arrays, enables systematic interrogation of the relationships between combinations of 3D mechanobiological cues and cellular responses, and thus has the potential to identify strategies to predictably control the construction of functional engineered tissues. Current high-throughput biomaterial screening approaches fail to consider the effects of dynamic mechanical stimulation, despite its importance in a wide variety of regenerative medicine applications. To meet this need, we developed a deformable membrane platform that enables 3D dynamic stretch of arrayed biomaterial constructs. Our

  11. Update on the Fabrication and Performance of 2-D Arrays of Superconducting Magnesium Diboride (MgB2) Thermal Detectors for Outer-Planets Exploration

    NASA Technical Reports Server (NTRS)

    Lakew, Brook; Aslam, S.

    2011-01-01

    Detectors with better performance than the current thermopile detectors that operate at room temperature will be needed at the focal plane of far-infrared instruments on future planetary exploration missions. We will present an update on recent results from the 2-D array of MgB2 thermal detectors being currently developed at NASA Goddard. Noise and sensitivity results will be presented and compared to thermal detectors currently in use on planetary missions.

  12. One-step Synthesis of Ordered Pd@TiO2 Nanofibers Array Film as Outstanding NH3 Gas Sensor at Room Temperature.

    PubMed

    Wu, Hongyuan; Huang, Haitao; Zhou, Jiao; Hong, Dahai; Ikram, Muhammad; Rehman, Afrasiab Ur; Li, Li; Shi, Keying

    2017-11-07

    The one dimensional (1D) ordered porous Pd@TiO 2 nanofibers (NFs) array film have been fabricated via a facile one-step synthesis of the electrospinning approach. The Pd@TiO 2 NFs (PTND3) contained Pd (2.0 wt %) and C, N element (16.2 wt %) display high dispersion of Pd nanoparticles (NPs) on TiO 2 NFs. Adding Pd meshed with C, N element to TiO 2 based NFs might contribute to generation of Lewis acid sites and Brønsted acid sites, which have been recently shown to enhance NH 3 adsorption-desorption ability; Pd NPs could increase the quantity of adsorbed O 2 on the surface of TiO 2 based NFs, and accelerated the O 2 molecule-ion conversion rate, enhanced the ability of electron transmission. The response time of PTND3 sensor towards 100 ppm NH 3 is only 3 s at room temperature (RT). Meantime, the response and response time of the PTND3 to the NH 3 is 1 and 14s even at the concentration of 100 ppb. Therefore, the ordered Pd@TiO 2 NFs array NH 3 sensor display great potential for practical applications.

  13. Calculating electronic tunnel currents in networks of disordered irregularly shaped nanoparticles by mapping networks to arrays of parallel nonlinear resistors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aghili Yajadda, Mir Massoud

    2014-10-21

    We have shown both theoretically and experimentally that tunnel currents in networks of disordered irregularly shaped nanoparticles (NPs) can be calculated by considering the networks as arrays of parallel nonlinear resistors. Each resistor is described by a one-dimensional or a two-dimensional array of equal size nanoparticles that the tunnel junction gaps between nanoparticles in each resistor is assumed to be equal. The number of tunnel junctions between two contact electrodes and the tunnel junction gaps between nanoparticles are found to be functions of Coulomb blockade energies. In addition, the tunnel barriers between nanoparticles were considered to be tilted at highmore » voltages. Furthermore, the role of thermal expansion coefficient of the tunnel junction gaps on the tunnel current is taken into account. The model calculations fit very well to the experimental data of a network of disordered gold nanoparticles, a forest of multi-wall carbon nanotubes, and a network of few-layer graphene nanoplates over a wide temperature range (5-300 K) at low and high DC bias voltages (0.001 mV–50 V). Our investigations indicate, although electron cotunneling in networks of disordered irregularly shaped NPs may occur, non-Arrhenius behavior at low temperatures cannot be described by the cotunneling model due to size distribution in the networks and irregular shape of nanoparticles. Non-Arrhenius behavior of the samples at zero bias voltage limit was attributed to the disorder in the samples. Unlike the electron cotunneling model, we found that the crossover from Arrhenius to non-Arrhenius behavior occurs at two temperatures, one at a high temperature and the other at a low temperature.« less

  14. Supramolecular Control over the Interparticle Distance in Gold Nanoparticle Arrays by Cyclodextrin Polyrotaxanes

    PubMed Central

    Paulo Coelho, Joao; Osío Barcina, José; Aicart, Emilio; Tardajos, Gloria; Cruz-Gil, Pablo; Salgado, Cástor; Díaz-Núñez, Pablo

    2018-01-01

    Amphiphilic nonionic ligands, synthesized with a fixed hydrophobic moiety formed by a thiolated alkyl chain and an aromatic ring, and with a hydrophilic tail composed of a variable number of oxyethylene units, were used to functionalize spherical gold nanoparticles (AuNPs) in water. Steady-state and time-resolved fluorescence measurements of the AuNPs in the presence of α-cyclodextrin (α-CD) revealed the formation of supramolecular complexes between the ligand and macrocycle at the surface of the nanocrystals. The addition of α-CD induced the formation of inclusion complexes with a high apparent binding constant that decreased with the increasing oxyethylene chain length. The formation of polyrotaxanes at the surface of AuNPs, in which many α-CDs are trapped as hosts on the long and linear ligands, was demonstrated by the formation of large and homogeneous arrays of self-assembled AuNPs with hexagonal close packing, where the interparticle distance increased with the length of the oxyethylene chain. The estimated number of α-CDs per polyrotaxane suggests a high rigidization of the ligand upon complexation, allowing for nearly perfect control of the interparticle distance in the arrays. This degree of supramolecular control was extended to arrays formed by AuNPs stabilized with polyethylene glycol and even to binary arrays. Electromagnetic simulations showed that the enhancement and distribution of the electric field can be finely controlled in these plasmonic arrays. PMID:29547539

  15. A micro GC detector array based on chemiresistors employing various surface functionalized monolayer-protected gold nanoparticles.

    PubMed

    Jian, Rih-Sheng; Huang, Rui-Xuan; Lu, Chia-Jung

    2012-01-15

    Aspects of the design, fabrication, and characterization of a chemiresistor type of microdetector for use in conjunction with gas chromatograph are described. The detector was manufactured on silicon chips using microelectromechanical systems (MEMS) technology. Detection was based on measuring changes in resistance across a film comprised of monolayer-protected gold nanoclusters (MPCs). When chromatographic separated molecules entered the detector cell, the MPC film absorbed vapor and undergoes swelling, then the resistance changes accordingly. Thiolates were used as ligand shells to encapsulate the nano-gold core and to manipulate the selectivity of the detector array. The dimensions of the μ-detector array were 14(L)×3.9(W)×1.2(H)mm. Mixtures of eight volatile organic compounds with different functional groups and volatility were tested to characterize the selectivity of the μ-detector array. The detector responses were rapid, reversible, and linear for all of the tested compounds. The detection limits ranged from 2 to 111ng, and were related to both the compound volatility and the selectivity of the surface ligands on the gold nanoparticles. Design and operation parameters such as flow rate, detector temperature, and width of the micro-fluidic channel were investigated. Reduction of the detector temperature resulted in improved sensitivity due to increased absorption. When a wider flow channel was used, the signal-to-noise ratio was improved due to the larger sensing area. The extremely low power consumption and small size makes this μ-detector array potentially useful for the development of integrated μ-GC. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. A multiple-scattering polaritonic-operator method for hybrid arrays of metal nanoparticles and quantum emitters

    NASA Astrophysics Data System (ADS)

    Chatzidakis, Georgios D.; Yannopapas, Vassilios

    2018-05-01

    We present a new technique for the study of hybrid collections of quantum emitters (atoms, molecules, quantum dots) with nanoparticles. The technique is based on a multiple-scattering polaritonic-operator formalism in conjunction with an electromagnetic coupled dipole method. Apart from collections of quantum emitters and nanoparticles, the method can equally treat the interaction of a collection of quantum emitters with a single nano-object of arbitrary shape in which case the nano-object is treated as a finite three-dimensional lattice of point scatterers. We have applied our method to the case of linear array (chain) of dimers of quantum emitters and metallic nanoparticles wherein the corresponding (geometrical and physical) parameters of the dimers are chosen so as the interaction between the emitter and the nanoparticle lies in the strong-coupling regime in order to enable the formation of plexciton states in the dimer. In particular, for a linear chain of dimers, we show that the corresponding light spectra reveal a multitude of plexciton modes resulting from the hybridization of the plexciton resonances of each individual dimer in a manner similar to the tight-binding description of electrons in solids.

  17. Overcoming multidrug resistance in 2D and 3D culture models by controlled drug chitosan-graft poly(caprolactone)-based nanoparticles.

    PubMed

    Shi, Wei-Bin; Le, Van-Minh; Gu, Chun-Hua; Zheng, Yuan-Hong; Lang, Mei-Dong; Lu, Yan-Hua; Liu, Jian-Wen

    2014-04-01

    The principal limitations of chemotherapy are dose-limiting systemic toxicity and the development of multidrug-resistant phenotypes. The aim of this study was to investigate the efficiency of a new sustained drug delivery system based on chitosan and ε-caprolactone to overcome multidrug resistance in monolayer and drug resistance associated with the three-dimensional (3D) tumor microenvironment in our established 3D models. The 5-fluorouracil (5-FU)-loaded nanoparticles (NPs) were characterized by transmission electron microscope and dynamic light scattering, and its released property was determined at different pH values. 5-FU/NPs exhibited well-sustained release properties and markedly enhanced the cytotoxicity of 5-FU against HCT116/L-OHP or HCT8/VCR MDR cells in two-dimensional (2D) and its parental cells in 3D collagen gel culture with twofold to threefold decrease in the IC50 values, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Hoechst/propidium iodide staining and flow cytometry analysis. Furthermore, the possible mechanism was explored by high-performance liquid chromatography and rhodamine 123 accumulation experiment. Overall, the results demonstrated that 5-FU/NPs increase intracellular concentration of 5-FU and enhance its anticancer efficiency by inducing apoptosis. It was suggested that this novel NPs are a promising carrier to decrease toxic of 5-FU and has the potential to reverse the forms of both intrinsic and acquired drug resistance in 2D and 3D cultures. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  18. Ni nanoparticles@Ni-Mo nitride nanorod arrays: a novel 3D-network hierarchical structure for high areal capacitance hybrid supercapacitors.

    PubMed

    Ruan, Yunjun; Lv, Lin; Li, Zhishan; Wang, Chundong; Jiang, Jianjun

    2017-11-23

    Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni 0.2 Mo 0.8 N nanorod arrays on a nickel foam (Ni-Mo-N NRA/NF) from its NiMoO 4 precursor, which delivers a high areal capacity of 2446 mC cm -2 at a current density of 2 mA cm -2 and shows outstanding cycling stability. The superior performance of the Ni-Mo-N NRA/NF can be ascribed to the metallic conductive nature of the Ni-Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni-Mo-N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg -1 at a power density of 773 W kg -1 and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni-Mo-N NRA/NF have a promising potential for use in high-performance supercapacitors.

  19. Cu-PDC-bpa solid coordination frameworks (PDC=2,5-pyrindinedicarboxylate; bpa=1,2-DI(4-pyridil)ethane)): 2D and 3D structural flexibility producing a 3-c herringbone array next to ideal

    NASA Astrophysics Data System (ADS)

    Llano-Tomé, Francisco; Bazán, Begoña; Urtiaga, Miren-Karmele; Barandika, Gotzone; Antonia Señarís-Rodríguez, M.; Sánchez-Andújar, Manuel; Arriortua, María-Isabel

    2015-10-01

    Combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce solid coordination frameworks (SCF) which are crystalline materials based on connections between metal ions through organic ligands. In this context, this work is focused on two novel CuII-based SCFs exhibiting PDC (2,5-pyridinedicarboxylate) and bpa (1,2-di(4-pyridyl)ethane), being the first structures reported in literature containing both ligands. Chemical formula are [Cu2[(PDC)2(bpa)(H2O)2]·3H2O·DMF (1), and [Cu2(PDC)2(bpa)(H2O)2]·7H2O (2), where DMF is dimethylformamide. Compounds 1 and 2 have been characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric (TG) analysis, differential thermal analysis (DTA) and dielectric measurements. The crystallographic analysis revealed that compounds 1 and 2 can be described as herringbone-type layers formed by helicoidal Cu-PDC-Cu chains connected through bpa ligands. Solvent molecules are crystallized between the layers, providing the inter-layer connections through hydrogen bonds. Differences between both compounds are attributable to the flexibility of bpa (in 2D) as well as to the 3D packing of the layers which is solvent dependent. This fact results in the fact that compound 2 is the most regular 3-c herringbone array reported so far. The structural dynamism of these networks is responsible for the crystalline to-amorphous to-crystalline (CAC) transformation from compound 1 to compound 2. Crystallochemical features for both compounds have also been studied and compared to similar 3-connected herringbone-arrays.

  20. Gold nanoparticle capture within protein crystal scaffolds.

    PubMed

    Kowalski, Ann E; Huber, Thaddaus R; Ni, Thomas W; Hartje, Luke F; Appel, Karina L; Yost, Jarad W; Ackerson, Christopher J; Snow, Christopher D

    2016-07-07

    DNA assemblies have been used to organize inorganic nanoparticles into 3D arrays, with emergent properties arising as a result of nanoparticle spacing and geometry. We report here the use of engineered protein crystals as an alternative approach to biologically mediated assembly of inorganic nanoparticles. The protein crystal's 13 nm diameter pores result in an 80% solvent content and display hexahistidine sequences on their interior. The hexahistidine sequence captures Au25(glutathione)∼17 (nitrilotriacetic acid)∼1 nanoclusters throughout a chemically crosslinked crystal via the coordination of Ni(ii) to both the cluster and the protein. Nanoparticle loading was validated by confocal microscopy and elemental analysis. The nanoparticles may be released from the crystal by exposure to EDTA, which chelates the Ni(ii) and breaks the specific protein/nanoparticle interaction. The integrity of the protein crystals after crosslinking and nanoparticle capture was confirmed by single crystal X-ray crystallography.

  1. Significant enhancement of power conversion efficiency for dye sensitized solar cell using 1D/3D network nanostructures as photoanodes

    PubMed Central

    Wang, Hao; Wang, Baoyuan; Yu, Jichao; Hu, Yunxia; Xia, Chen; Zhang, Jun; Liu, Rong

    2015-01-01

    The single–crystalline TiO2 nanorod arrays with rutile phase have attracted much attention in the dye sensitized solar cells (DSSCs) applications because of their superior chemical stability, better electron transport properties, higher refractive index and low production cost. However, it suffers from a low surface area as compared with TiO2 nanoparticle films. In order to enlarge the surface area of TiO2 nanorod arrays, the 1D nanorods/3D nanotubes sample was synthesized using a facile two-step hydrothermal process involving hydrothermal growth 1D/3D nanorods and followed by post-etching treatment. In such bi-layer structure, the oriented TiO2 nanorods layer could provide direct pathway for fast electron transportation, and the 3D nanotubes layer offers a higher surface area for dye loading, therefore, the 1D nanorods/3D nanotubes photoanode exhibited faster electron transport and higher surface area than either 1D or 3D nanostructures alone, and an highest efficiency of 7.68% was achieved for the DSSCs based on 1D nanorods/3D nanotubes photoanode with further TiCl4 treatment. PMID:25800933

  2. Crab-shell induced synthesis of ordered macroporous carbon nanofiber arrays coupled with MnCo2O4 nanoparticles as bifunctional oxygen catalysts for rechargeable Zn-air batteries.

    PubMed

    Bin, Duan; Guo, Ziyang; Tamirat, Andebet Gedamu; Ma, Yuanyuan; Wang, Yonggang; Xia, Yongyao

    2017-08-10

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are traditionally carried out using noble metals (such as Pt) and metal oxides (such as RuO 2 and IrO 2 ) as catalysts, respectively. Nevertheless, several key issues such as high cost, poor stability, and detrimental environmental effects limit the catalytic activity of these noble metal- and metal oxide-based catalysts. Herein, we have designed and synthesized macroporous carbon nanofiber arrays by using a natural crab shell template. Subsequently, spinel MnCo 2 O 4 nanoparticles were embedded into the nitrogen-doped macroporous carbon nanofiber arrays (NMCNAs) by a hydrothermal method. Accompanied by the good conductivity, large surface area and doping of nitrogen, the as-prepared MnCo 2 O 4 /NMCNA exhibited remarkable catalytic performance and outstanding stability for both ORR and OER in alkaline media. The macroporous superstructures play vital role in reducing the ion transport resistance and facilitating the diffusion of gaseous products (O 2 ). Finally, rechargeable Zn-air batteries using the MnCo 2 O 4 /NMCNA catalyst displayed appreciably lower overpotentials, higher power density and better stability than commercial Pt/C, thus raising the prospect of functional low-cost, non-precious-metal bifunctional catalysts in metal-air batteries.

  3. Novel anti-reflection technology for GaAs single-junction solar cells using surface patterning and Au nanoparticles.

    PubMed

    Kim, Youngjo; Lam, Nguyen Dinh; Kim, Kangho; Kim, Sangin; Rotermund, Fabian; Lim, Hanjo; Lee, Jaejin

    2012-07-01

    Single-junction GaAs solar cell structures were grown by low-pressure MOCVD on GaAs (100) substrates. Micro-rod arrays with diameters of 2 microm, 5 microm, and 10 microm were fabricated on the surfaces of the GaAs solar cells via photolithography and wet chemical etching. The patterned surfaces were coated with Au nanoparticles using an Au colloidal solution. Characteristics of the GaAs solar cells with and without the micro-rod arrays and Au nanoparticles were investigated. The short-circuit current density of the GaAs solar cell with 2 microm rod arrays and Au nanoparticles increased up to 34.9% compared to that of the reference cell without micro-rod arrays and Au nanoparticles. The conversion efficiency of the GaAs solar cell that was coated with Au nanoparticles on the patterned surface with micro-rod arrays can be improved from 14.1% to 19.9% under 1 sun AM 1.5G illumination. These results show that micro-rod arrays and Au nanoparticle coating can be applied together in surface patterning to achieve a novel cost-effective anti-reflection technology.

  4. Ratchet Effects and Domain Wall Energy Landscapes in Amorphous Magnetic Films with 2D Arrays of Asymmetric Holes

    NASA Astrophysics Data System (ADS)

    Martin, J. I.; Alija, A.; Sobrado, I.; Perez-Junquera, A.; Rodriguez-Rodriguez, G.; Velez, M.; Alameda, J. M.; Marconi, V. I.; Kolton, A. B.; Parrondo, J. M. R.

    2009-03-01

    The driven motion of domain walls in extended magnetic films patterned with 2D arrays of asymmetric holes has been found to be subject to two different crossed ratchet effects [1] which results in an inversion of the sign of domain wall motion rectification as a function of the applied magnetic field. This effect can be understood in terms of the competition between drive, elasticity and asymmetric pinning as revealed by a simple 4̂-model. In order to optimize the asymmetric hole design, the relevant energy landscapes for domain wall motion across the array of asymmetric holes have been calculated by micromagnetic simulations as a function of array geometrical characteristics. The effects of a transverse magnetic field on these two crossed ratchet effects will also be discussed in terms of the decrease in domain wall energy per unit area and of the modifications in the magnetostatic barriers for domain wall pinning at the asymmetric inclusions. Work supported by Spanish MICINN.[1] A. Perez-Junquera et al, Phys. Rev. Lett. 100 (2008) 037203

  5. Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI-LINAC systems.

    PubMed

    Gargett, Maegan; Oborn, Brad; Metcalfe, Peter; Rosenfeld, Anatoly

    2015-02-01

    MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named "magic plate," for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. geant4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-line and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm(3)) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm(2) area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm(2) photon field size. The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI-linear accelerator systems. In the in-line orientation, the

  6. 3D-Printed Fluidic Devices for Nanoparticle Preparation and Flow-Injection Amperometry Using Integrated Prussian Blue Nanoparticle-Modified Electrodes

    PubMed Central

    Bishop, Gregory W.; Satterwhite, Jennifer E.; Bhakta, Snehasis; Kadimisetty, Karteek; Gillette, Kelsey M.; Chen, Eric; Rusling, James F.

    2015-01-01

    A consumer-grade fused filament fabrication (FFF) 3D printer was used to construct fluidic devices for nanoparticle preparation and electrochemical sensing. Devices were printed using poly(ethylene terephthalate) and featured threaded ports to connect polyetheretherketone (PEEK) tubing via printed fittings prepared from acrylonitrile butadiene styrene (ABS). These devices included channels designed to have 800 × 800 µm2 square cross sections and were semitransparent to allow visualization of the solution-filled channels. A 3D-printed device with a Y-shaped mixing channel was used to prepare Prussian blue nanoparticles (PBNPs) under flow rates of 100 to 2000 µL min−1. PBNPs were then attached to gold electrodes for hydrogen peroxide sensing. 3D-printed devices used for electrochemical measurements featured threaded access ports into which a fitting equipped with reference, counter, and PBNP-modified working electrodes could be inserted. PBNP-modified electrodes enabled amperometric detection of H2O2 in the 3D-printed channel by flow-injection analysis, exhibiting a detection limit of 100 nM and linear response up to 20 µM. These experiments show that a consumer-grade FFF printer can be used to fabricate low-cost fluidic devices for applications similar to those that have been reported with more expensive 3D-printing methods. PMID:25901660

  7. 3D plasmonic nanoarchitectures for extreme light concentration

    NASA Astrophysics Data System (ADS)

    Arnob, Md Masud Parvez; Zhao, Fusheng; Shih, Wei-Chuan

    2017-08-01

    Plasmonic nanomaterials are known to concentrate incident light to their surfaces by collective electron oscillation. Plasmonic hot-spot refers to locations where electromagnetic fields are particularly enhanced relative to the incident field. Traditional plasmonic nanomaterials are 1D (e.g., colloidal nanoparticles) or 2D (lithographically patterned nanostructure arrays) in nature, which typically result in sparse field concentration patterns. To improve efficiency and better utilization of hot-spots, we investigate 3D plasmonic nanoarchitecture where abundant hot-spots are formed in a 3D volumetric fashion, a feature drastically departing from traditional nanostructures.

  8. 2D Spin Crossover Nanoparticles described by the Ising-like model solved in Local Mean-Field Approximation

    NASA Astrophysics Data System (ADS)

    Eddine Allal, Salah; Linares, Jorge; Boukheddaden, K.; Dahoo, Pierre Richard; de Zela, F.

    2017-12-01

    Some six-coordinate iron (II) coordination compounds exhibit thermal-, optical-, electrical-, magnetic- and pressure-induced switching between the diamagnetic low-spin (LS, S=0) and the paramagnetic high-spin (HS; S=2) states [1]. This may lead to potential application of these complexes in molecular devices such as temperature and pressure sensors [2]. An Ising-like model has been proposed to explain the occurrence of the thermal hysteresis behaviour [3,4] of this switchable solids. In this contribution, the local mean field approximation is applied to solve the Hamiltonian modelling interactions pertaining to 2D nanoparticles embedded in a magnetically-inactive matrix.

  9. Time-dependent transport of a localized surface plasmon through a linear array of metal nanoparticles: Precursor and normal mode contributions

    NASA Astrophysics Data System (ADS)

    Compaijen, P. J.; Malyshev, V. A.; Knoester, J.

    2018-02-01

    We theoretically investigate the time-dependent transport of a localized surface plasmon excitation through a linear array of identical and equidistantly spaced metal nanoparticles. Two different signals propagating through the array are found: one traveling with the group velocity of the surface plasmon polaritons of the system and damped exponentially, and the other running with the speed of light and decaying in a power-law fashion, as x-1 and x-2 for the transversal and longitudinal polarizations, respectively. The latter resembles the Sommerfeld-Brillouin forerunner and has not been identified in previous studies. The contribution of this signal dominates the plasmon transport at large distances. In addition, even though this signal is spread in the propagation direction and has the lateral dimension larger than the wavelength, the field profile close to the chain axis does not change with distance, indicating that this part of the signal is confined to the array.

  10. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

    PubMed Central

    Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

    2013-01-01

    Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

  11. Dipolar ferromagnetic phase transition in Fe3O4 nanoparticle arrays observed by Lorentz microscopy and electron holography

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kazuo; Hogg, Charles R.; Yamamuro, Saeki; Hirayama, Tsukasa; Majetich, Sara A.

    2011-02-01

    Dipolar ferromagnetism formed in Fe3O4 nanoparticle arrays is revealed by Fresnel Lorentz microscopy and electron holography. Dipolar domain walls do not lie preferentially along macrograin boundaries but depend on the overall shape of the assembly, meaning magnetostatic energy dominates. The domain structures are imaged at different temperatures for both monolayer and bilayer arrays. The domain wall contrast in the monolayer region is visible until 575 °C, and the magnetic order parameter steeply drops toward the temperature. In the bilayer region, finer and more complicated domains are formed.

  12. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    DOE PAGES

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; ...

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, asmore » an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.« less

  13. SERS Detection of Biomolecules by Highly Sensitive and Reproducible Raman-Enhancing Nanoparticle Array

    NASA Astrophysics Data System (ADS)

    Chan, Tzu-Yi; Liu, Ting-Yu; Wang, Kuan-Syun; Tsai, Kun-Tong; Chen, Zhi-Xin; Chang, Yu-Chi; Tseng, Yi-Qun; Wang, Chih-Hao; Wang, Juen-Kai; Wang, Yuh-Lin

    2017-05-01

    This paper describes the preparation of nanoarrays composed of silver nanoparticles (AgNPs: 20-50 nm) for use as surface-enhanced Raman scattering (SERS) substrates. The AgNPs were grown on porous anodic aluminum oxide (AAO) templates by electrochemical plating, and the inter-channel gap of AAO channels is between 10 and 20 nm. The size and interparticle gap of silver particles were adjusted in order to achieve optimal SERS signals and characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The fluctuation of SERS intensity is about 10-20% when measuring adenine solutions, showing a great reproducible SERS sensing. The nanoparticle arrays offer a large potential for practical applications as shown by the SERS-based quantitative detection and differentiation of adenine (A), thymine (T), cytosine (C), guanine (G), β-carotene, and malachite green. The respective detection limits are <1 ppb for adenine and <0.63 ppm for β-carotene and malachite green, respectively.

  14. Toward highly sensitive surface-enhanced Raman scattering: the design of a 3D hybrid system with monolayer graphene sandwiched between silver nanohole arrays and gold nanoparticles.

    PubMed

    Zhao, Yuan; Yang, Dong; Li, Xiyu; Liu, Yu; Hu, Xiang; Zhou, Dianfa; Lu, Yalin

    2017-01-19

    We report a novel graphene-metal hybrid system by introducing monolayer graphene between gold nanoparticles (Au NPs) and silver nanohole (Ag NH) arrays. The design incorporates three key advantages to promote the surface-enhanced Raman scattering (SERS) sensing capacity: (i) making full use of the single-atomic feature of graphene for generating uniform sub-nanometer spaces; (ii) maintaining the bottom layer of Ag nanoarrays with an ordered manner for facilitating the transfer of graphene films and assembly of the top layer of Au NPs; (iii) integrating the advantages of the strong plasmonic effect of Ag, the chemical stability of Au, as well as the mechanical flexibility and biological compatibility of graphene. In this configuration, the plasmonic properties can be fine-tuned by separately optimizing the horizontal or vertical gaps between the metal NPs. Exactly, sub-20 nm spaces between the horizontally patterned Ag tips constructed by adjacent Ag NHs, and sub-nanometer scale graphene gaps between the vertically distributed Au NP-Ag NH have been achieved. Finite element numerical simulations demonstrate that the multi-dimensional plasmonic couplings (including the Au NP-Au NP, Au NP-Ag NH and Ag NH-Ag NH couplings) promote for the hybrid platform an electric field enhancement up to 137 times. Impressively, the as-prepared 3D Au NP-graphene-Ag NH array hybrid structure manifests ultrahigh SERS sensitivity with a detection limit of 10 -13 M for R6G molecules, as well as good reproducibility and stability. This work represents a step towards high-performance SERS substrate fabrication, and opens up a new route for graphene-plasmonic hybrids in SERS applications.

  15. SU-E-T-644: Evaluation of Angular Dependence Correction for 2D Array Detector Using for Quality Assurance of Volumetric Modulated Arc Therapy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karthikeyan, N; Ganesh, K M; Vikraman, S

    2014-06-15

    Purpose: To evaluate the angular dependence correction for Matrix Evolution 2D array detector in quality assurance of volumetric modulated arc therapy(VMAT). Methods: Total ten patients comprising of different sites were planned for VMAT and taken for the study. Each plan was exposed on Matrix Evolution 2D array detector with Omnipro IMRT software based on the following three different methods using 6MV photon beams from Elekta Synergy linear accelerator. First method, VMAT plan was delivered on Matrix Evolution detector as it gantry mounted with dedicated holder with build-up of 2.3cm. Second, the VMAT plan was delivered with the static gantry anglemore » on to the table mounted setup. Third, the VMAT plan was delivered with actual gantry angle on Matrix Evolution detector fixed in Multicube phantom with gantry angle sensor and angular dependence correction were applied to quantify the plan quality. For all these methods, the corresponding QA plans were generated in TPS and the dose verification was done for both point and 2D fluence analysis with pass criteria of 3% dose difference and 3mm distance to agreement. Results: The measured point dose variation for the first method was observed as 1.58±0.6% of mean and SD with TPS calculated. For second and third method, the mean and standard deviation(SD) was observed as 1.67±0.7% and 1.85±0.8% respectively. The 2D fluence analysis of measured and TPS calculated has the mean and SD of 97.9±1.1%, 97.88±1.2% and 97.55±1.3% for first, second and third methods respectively. The calculated two-tailed Pvalue for point dose and 2D fluence analysis shows the insignificance with values of 0.9316 and 0.9015 respectively, among the different methods of QA. Conclusion: The qualitative evaluation of angular dependence correction for Matrix Evolution 2D array detector shows its competency in accuracy of quality assurance measurement of composite dose distribution of volumetric modulated arc therapy.« less

  16. Milligram-per-second femtosecond laser production of Se nanoparticle inks and ink-jet printing of nanophotonic 2D-patterns

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey; Ivanova, Anastasia; Khmel'nitskii, Roman; Klevkov, Yury; Kudryashov, Sergey; Mel'nik, Nikolay; Nastulyavichus, Alena; Rudenko, Andrey; Saraeva, Irina; Smirnov, Nikita; Zayarny, Dmitry; Baranov, Anatoly; Kirilenko, Demid; Brunkov, Pavel; Shakhmin, Alexander

    2018-04-01

    Milligram-per-second production of selenium nanoparticles in water sols was realized through 7-W, 2 MHz-rate femtosecond laser ablation of a crystalline trigonal selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of the corresponding crater depths and topographies. Deposited selenium particles were inspected by scanning and transmission electron microscopy, while their hydrosols (nanoinks) were characterized by optical transmission, Raman and dynamic light scattering spectroscopy. 2D patterns and coatings were ink-jet printed on thin supported silver films and their bare silica glass substrates, as well as on IR-transparent CaF2 substrates, and characterized by electron microscopy, energy-dispersive x-ray spectroscopy, and broadband (vis-mid IR) transmission spectroscopy, exhibiting crystalline selenium nanoparticles with high refractive index as promising all-dielectric sensing building nanoblocks in nanophotonics.

  17. Driving morphological changes in magnetic nanoparticle structures through the application of acoustic waves and magnetic fields

    NASA Astrophysics Data System (ADS)

    Huang, Ann; Miansari, Morteza; Friend, James

    The growing interest in acoustic manipulation of particles in micro to nanofluidics using surface acoustic waves (SAW), together with the many applications of magnetic nanoparticles-whether individual or in arrays-underpins our discovery of how these forces can be used to rapidly, easily, and irreversibly form 1D chains and 2D films. These films and chains are currently difficult to produce yet offer many advantages over individual nanoparticles in suspension. Making use of the scale of the structures formed, 10-9 to 10-5 m, and by taking a balance of the relevant external and interparticle forces, the underlying mechanisms responsible for the phenomena become apparent. For 1D chains, the magnetic field alone is sufficient, though applying an acoustic field drives a topology change from loosely connected chains to loops of 10 -100 particles. Adding the acoustic field drives a transition from these looped structures to dense 2D arrays via interparticle Bjerknes forces. Inter-particle drainage of the surrounding fluid leaves these structures intact after removal of the externally applied forces. Clear morphology transitions are present and depend on the relative amplitude of the incident Brownian, Bjerknes, and magnetic forces. UCSD: Frontiers of Innovation Scholars Program (U-1024).

  18. FIB-tomographic studies on chemical vapor deposition grown SnO2 nanowire arrays on TiO2 (001)

    NASA Astrophysics Data System (ADS)

    Chen, Haoyun; Liu, Yi; Wu, Hong; Xiong, Xiang; Pan, Jun

    2016-12-01

    Tin oxide nanowire arrays on titania (001) have been successfully fabricated by chemical vapor deposition of Sn(O t Bu)4 precursor. The morphologies and structures of ordered SnO2 nanowires (NWs) were analyzed by cross-sectional SEM, HR-TEM and AFM. An FIB-tomography technique was applied in order to reconstruct a 3D presentation of ordered SnO2 nanowires. The achieved 3D analysis showed the spatial orientation and angles of ordered SnO2 NWs can be obtained in a one-shot experiment, and the distribution of Au catalysts showed the competition between 1D and 2D growth. The SnO2 nanowire arrays can be potentially used as a diameter- and surface-dependent sensing unit for the detection of gas- and bio-molecules.

  19. Titanium mesh supported TiO2 nanowire arrays/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles novel composites for flexible dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Wenwu; Zhang, Huanyu; Wang, Hui-gang; Zhang, Mei; Guo, Min

    2017-11-01

    Ti-mesh supported TiO2 nanowire arrays (NWAs)/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles (UC-EY-TiO2 NPs) composite structured photoanodes for fully flexible dye sensitized solar cells (DSSCs) were firstly constructed via a hydrothermal and spin coating process. UV-vis-NIR absorption spectra of the TiO2 NWAs/UC-EY-TiO2 NPs composites exhibited strong absorption around near infrared (NIR) 980 nm. The composites excited by 980 nm NIR laser could emit upconversion fluorescence at 489, 526, 549 and 658 nm, which expanded the spectral response range and sunlight capturing capability of formed flexible DSSCs. Moreover, the TiO2 NWAs/UC-EY-TiO2 NPs was coated with an Nb2O5 thin layer to further suppress electron recombination losses. The complete flexible DSSCs based on Nb2O5 coated TiO2 NWAs/2.0 mol% Er3+-1.0 mol% Yb3+ codoped TiO2 NPs photoanode and Pt/ITO-PEN counter electrode exhibited an enhanced photon to current conversion efficiency of 8.10%, a 68% improvement compared to TiO2 NWAs/undoped TiO2 NPs based DSSCs (4.82%).

  20. 3D morphology reconstruction using linear array CCD binocular stereo vision imaging system

    NASA Astrophysics Data System (ADS)

    Pan, Yu; Wang, Jinjiang

    2018-01-01

    Binocular vision imaging system, which has a small field of view, cannot reconstruct the 3-D shape of the dynamic object. We found a linear array CCD binocular vision imaging system, which uses different calibration and reconstruct methods. On the basis of the binocular vision imaging system, the linear array CCD binocular vision imaging systems which has a wider field of view can reconstruct the 3-D morphology of objects in continuous motion, and the results are accurate. This research mainly introduces the composition and principle of linear array CCD binocular vision imaging system, including the calibration, capture, matching and reconstruction of the imaging system. The system consists of two linear array cameras which were placed in special arrangements and a horizontal moving platform that can pick up objects. The internal and external parameters of the camera are obtained by calibrating in advance. And then using the camera to capture images of moving objects, the results are then matched and 3-D reconstructed. The linear array CCD binocular vision imaging systems can accurately measure the 3-D appearance of moving objects, this essay is of great significance to measure the 3-D morphology of moving objects.

  1. Simulation of Mean Flow and Turbulence over a 2D Building Array Using High-Resolution CFD and a Distributed Drag Force Approach

    DTIC Science & Technology

    2016-06-16

    procedure. The predictive capabilities of the high-resolution computational fluid dynamics ( CFD ) simulations of urban flow are validated against a very...turbulence over a 2D building array using high-resolution CFD and a distributed drag force approach a Department of Mechanical Engineering, University

  2. Theory of tailorable optical response of two-dimensional arrays of plasmonic nanoparticles at dielectric interfaces.

    PubMed

    Sikdar, Debabrata; Kornyshev, Alexei A

    2016-09-22

    Two-dimensional arrays of plasmonic nanoparticles at interfaces are promising candidates for novel optical metamaterials. Such systems materialise from 'top-down' patterning or 'bottom-up' self-assembly of nanoparticles at liquid/liquid or liquid/solid interfaces. Here, we present a comprehensive analysis of an extended effective quasi-static four-layer-stack model for the description of plasmon-resonance-enhanced optical responses of such systems. We investigate in detail the effects of the size of nanoparticles, average interparticle separation, dielectric constants of the media constituting the interface, and the nanoparticle position relative to the interface. Interesting interplays of these different factors are explored first for normally incident light. For off-normal incidence, the strong effects of the polarisation of light are found at large incident angles, which allows to dynamically tune the reflectance spectra. All the predictions of the theory are tested against full-wave simulations, proving this simplistic model to be adequate within the quasi-static limit. The model takes seconds to calculate the system's optical response and makes it easy to unravel the effect of each system parameter. This helps rapid rationalization of experimental data and understanding of the optical signals from these novel 'metamaterials', optimised for light reflection or harvesting.

  3. Theory of tailorable optical response of two-dimensional arrays of plasmonic nanoparticles at dielectric interfaces

    PubMed Central

    Sikdar, Debabrata; Kornyshev, Alexei A.

    2016-01-01

    Two-dimensional arrays of plasmonic nanoparticles at interfaces are promising candidates for novel optical metamaterials. Such systems materialise from ‘top–down’ patterning or ‘bottom–up’ self-assembly of nanoparticles at liquid/liquid or liquid/solid interfaces. Here, we present a comprehensive analysis of an extended effective quasi-static four-layer-stack model for the description of plasmon-resonance-enhanced optical responses of such systems. We investigate in detail the effects of the size of nanoparticles, average interparticle separation, dielectric constants of the media constituting the interface, and the nanoparticle position relative to the interface. Interesting interplays of these different factors are explored first for normally incident light. For off-normal incidence, the strong effects of the polarisation of light are found at large incident angles, which allows to dynamically tune the reflectance spectra. All the predictions of the theory are tested against full-wave simulations, proving this simplistic model to be adequate within the quasi-static limit. The model takes seconds to calculate the system’s optical response and makes it easy to unravel the effect of each system parameter. This helps rapid rationalization of experimental data and understanding of the optical signals from these novel ‘metamaterials’, optimised for light reflection or harvesting. PMID:27652788

  4. Holographic method for site-resolved detection of a 2D array of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

    2016-08-01

    We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

  5. Genetic toxicity assessment of engineered nanoparticles using a 3D in vitro skin model (EpiDerm™).

    PubMed

    Wills, John W; Hondow, Nicole; Thomas, Adam D; Chapman, Katherine E; Fish, David; Maffeis, Thierry G; Penny, Mark W; Brown, Richard A; Jenkins, Gareth J S; Brown, Andy P; White, Paul A; Doak, Shareen H

    2016-09-09

    The rapid production and incorporation of engineered nanomaterials into consumer products alongside research suggesting nanomaterials can cause cell death and DNA damage (genotoxicity) makes in vitro assays desirable for nanosafety screening. However, conflicting outcomes are often observed when in vitro and in vivo study results are compared, suggesting more physiologically representative in vitro models are required to minimise reliance on animal testing. BASF Levasil® silica nanoparticles (16 and 85 nm) were used to adapt the 3D reconstructed skin micronucleus (RSMN) assay for nanomaterials administered topically or into the growth medium. 3D dose-responses were compared to a 2D micronucleus assay using monocultured human B cells (TK6) after standardising dose between 2D / 3D assays by total nanoparticle mass to cell number. Cryogenic vitrification, scanning electron microscopy and dynamic light scattering techniques were applied to characterise in-medium and air-liquid interface exposures. Advanced transmission electron microscopy imaging modes (high angle annular dark field) and X-ray spectrometry were used to define nanoparticle penetration / cellular uptake in the intact 3D models and 2D monocultured cells. For all 2D exposures, significant (p < 0.002) increases in genotoxicity were observed (≥100 μg/mL) alongside cell viability decreases (p < 0.015) at doses ≥200 μg/mL (16 nm-SiO2) and ≥100 μg/mL (85 nm-SiO2). In contrast, 2D-equivalent exposures to the 3D models (≤300 μg/mL) caused no significant DNA damage or impact on cell viability. Further increasing dose to the 3D models led to probable air-liquid interface suffocation. Nanoparticle penetration / cell uptake analysis revealed no exposure to the live cells of the 3D model occurred due to the protective nature of the skin model's 3D cellular microarchitecture (topical exposures) and confounding barrier effects of the collagen cell attachment layer (in-medium exposures). 2D

  6. Interdroplet bilayer arrays in millifluidic droplet traps from 3D-printed moulds.

    PubMed

    King, Philip H; Jones, Gareth; Morgan, Hywel; de Planque, Maurits R R; Zauner, Klaus-Peter

    2014-02-21

    In droplet microfluidics, aqueous droplets are typically separated by an oil phase to ensure containment of molecules in individual droplets of nano-to-picoliter volume. An interesting variation of this method involves bringing two phospholipid-coated droplets into contact to form a lipid bilayer in-between the droplets. These interdroplet bilayers, created by manual pipetting of microliter droplets, have proved advantageous for the study of membrane transport phenomena, including ion channel electrophysiology. In this study, we adapted the droplet microfluidics methodology to achieve automated formation of interdroplet lipid bilayer arrays. We developed a 'millifluidic' chip for microliter droplet generation and droplet packing, which is cast from a 3D-printed mould. Droplets of 0.7-6.0 μL volume were packed as homogeneous or heterogeneous linear arrays of 2-9 droplets that were stable for at least six hours. The interdroplet bilayers had an area of up to 0.56 mm(2), or an equivalent diameter of up to 850 μm, as determined from capacitance measurements. We observed osmotic water transfer over the bilayers as well as sequential bilayer lysis by the pore-forming toxin melittin. These millifluidic interdroplet bilayer arrays combine the ease of electrical and optical access of manually pipetted microdroplets with the automation and reproducibility of microfluidic technologies. Moreover, the 3D-printing based fabrication strategy enables the rapid implementation of alternative channel geometries, e.g. branched arrays, with a design-to-device time of just 24-48 hours.

  7. Interfacial self-assembled functional nanoparticle array: a facile surface-enhanced Raman scattering sensor for specific detection of trace analytes.

    PubMed

    Zhang, Kun; Ji, Ji; Li, Yixin; Liu, Baohong

    2014-07-01

    Surface-enhanced Raman scattering (SERS) has proven to be promising for the detection of trace analytes; however, the precise nanofabrication of a specific and sensitive plasmonic SERS-active substrate is still a major challenge that limits the scope of its applications. In this work, gold nanoparticles are self-assembled into densely packed two-dimensional arrays at a liquid/liquid interface between dimethyl carbonate and water in the absence of template controller molecules. Both the simulation and experiment results show that the particles within these film-like arrays exhibit strong electromagnetic coupling and enable large amplification of Raman signals. In order to realize the level of sensing specificity, the surface chemistry of gold nanoparticles (Au NPs) is rationally tailored by incorporating an appropriate chemical moiety that specifically captures molecules of interest. The ease of fabrication and good uniformity make this platform ideal for in situ SERS sensing of trace targets in complex samples.

  8. Hydrogenated TiO2 nanotube arrays for supercapacitors.

    PubMed

    Lu, Xihong; Wang, Gongming; Zhai, Teng; Yu, Minghao; Gan, Jiayong; Tong, Yexiang; Li, Yat

    2012-03-14

    We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors. © 2012 American Chemical Society

  9. Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI–LINAC systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gargett, Maegan, E-mail: mg406@uowmail.edu.au; Rosenfeld, Anatoly; Oborn, Brad

    2015-02-15

    Purpose: MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named “magic plate,” for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. Methods: GEANT4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-linemore » and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm{sup 3}) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm{sup 2} area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm{sup 2} photon field size. Results: The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. Conclusions: A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed

  10. Modal analysis of 2-D sedimentary basin from frequency domain decomposition of ambient vibration array recordings

    NASA Astrophysics Data System (ADS)

    Poggi, Valerio; Ermert, Laura; Burjanek, Jan; Michel, Clotaire; Fäh, Donat

    2015-01-01

    Frequency domain decomposition (FDD) is a well-established spectral technique used in civil engineering to analyse and monitor the modal response of buildings and structures. The method is based on singular value decomposition of the cross-power spectral density matrix from simultaneous array recordings of ambient vibrations. This method is advantageous to retrieve not only the resonance frequencies of the investigated structure, but also the corresponding modal shapes without the need for an absolute reference. This is an important piece of information, which can be used to validate the consistency of numerical models and analytical solutions. We apply this approach using advanced signal processing to evaluate the resonance characteristics of 2-D Alpine sedimentary valleys. In this study, we present the results obtained at Martigny, in the Rhône valley (Switzerland). For the analysis, we use 2 hr of ambient vibration recordings from a linear seismic array deployed perpendicularly to the valley axis. Only the horizontal-axial direction (SH) of the ground motion is considered. Using the FDD method, six separate resonant frequencies are retrieved together with their corresponding modal shapes. We compare the mode shapes with results from classical standard spectral ratios and numerical simulations of ambient vibration recordings.

  11. Dielectrophoretic immobilisation of nanoparticles as isolated singles in regular arrays

    NASA Astrophysics Data System (ADS)

    Knigge, Xenia; Wenger, Christian; Bier, Frank F.; Hölzel, Ralph

    2018-02-01

    We demonstrate the immobilisation of polystyrene nanoparticles on vertical nano-electrodes by means of dielectrophoresis. The electrodes have diameters of 500 nm or 50 nm, respectively, and are arranged in arrays of several thousand electrodes, allowing many thousands of experiments in parallel. At a frequency of 15 kHz, which is found favourable for polystyrene, several occupation patterns are observed, and both temporary and permanent immobilisation is achieved. In addition, a histogram method is applied, which allows to determine the number of particles occupying the electrodes. These results are validated with scanning electron microscopy images. Immobilising exactly one particle at each electrode tip is achieved for electrode tip diameters with half the particle size. Extension of this system down to the level of single molecules is envisaged, which will avoid ensemble averaging at still statistically large sample sizes.

  12. Micromirror Array Control of a Phase-Locked Laser Diode Array

    DTIC Science & Technology

    1995-12-01

    Micromirror Intensity-Voltage Curve . From the intensity plot, maxima (Ix) and minima (IMN) are noted. If IMAX and IMn are known, A4 can be calculated for...of the micromirror array used. Mirror 9 600 500 E 400- S300- C, -0200 lOO_ 0 0 5 10 15 20 25 30 Volts Figure 3b. Mirror Deflection Curve Corresponding...AFIT/GAP/ENP/95D-2 MICROMIRROR ARRAY CONTROL OF A PHASE-LOCKED LASER DIODE ARRAY THESIS Carl J. Christensen, Captain, USAF AFIT/GAP/ENP/95D-2

  13. 3D-fabrication of tunable and high-density arrays of crystalline silicon nanostructures

    NASA Astrophysics Data System (ADS)

    Wilbers, J. G. E.; Berenschot, J. W.; Tiggelaar, R. M.; Dogan, T.; Sugimura, K.; van der Wiel, W. G.; Gardeniers, J. G. E.; Tas, N. R.

    2018-04-01

    In this report, a procedure for the 3D-nanofabrication of ordered, high-density arrays of crystalline silicon nanostructures is described. Two nanolithography methods were utilized for the fabrication of the nanostructure array, viz. displacement Talbot lithography (DTL) and edge lithography (EL). DTL is employed to perform two (orthogonal) resist-patterning steps to pattern a thin Si3N4 layer. The resulting patterned double layer serves as an etch mask for all further etching steps for the fabrication of ordered arrays of silicon nanostructures. The arrays are made by means of anisotropic wet etching of silicon in combination with an isotropic retraction etch step of the etch mask, i.e. EL. The procedure enables fabrication of nanostructures with dimensions below 15 nm and a potential density of 1010 crystals cm-2.

  14. First data with the Hybrid Array of Gamma Ray Detector (HAGRiD)

    NASA Astrophysics Data System (ADS)

    Smith, K.; Baugher, T.; Burcher, S.; Carter, A. B.; Cizewski, J. A.; Chipps, K. A.; Febbraro, M.; Grzywacz, R.; Jones, K. L.; Munoz, S.; Pain, S. D.; Paulauskas, S. V.; Ratkiewicz, A.; Schmitt, K. T.; Thornsberry, C.; Toomey, R.; Walter, D.; Willoughby, H.

    2018-01-01

    The structure of nuclei provides insight into astrophysical reaction rates that are difficult to measure directly. These studies are often performed with transfer reactions and β-decay measurements. These experiments benefit from particle-γ coincidence measurements which provide information beyond that of particle detection alone. The Hybrid Array of Gamma Ray Detectors (HAGRiD) of LaBr3(Ce) scintillators has been designed with this purpose in mind. The design of the array permits it to be coupled with particle detector systems, such as the Oak Ridge Rutgers University Barrel Array (ORRUBA) of silicon detectors and the Versatile Array of Neutron Detectors at Low Energy (VANDLE). It is also designed to operate with the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) advanced target system. HAGRiD's design avoids compromising the charged-particle angular resolution due to compact geometries which are often used to increase the γ efficiency in other systems. First experiments with HAGRiD coupled to VANDLE as well as ORRUBA and JENSA are discussed.

  15. Infrared Speckle Interferometry with 2-D Arrays

    NASA Technical Reports Server (NTRS)

    Harvey, P. M.; Balkum, S. L.; Monin, J. L.

    1994-01-01

    We describe results from a program of speckle interferometry with two-dimensional infrared array detectors. Analysis of observations of eta Carinae made with 58 x 62 InSb detector are discussed. The data have been analyzed with both the Labeyrie autocorrelation, a deconvolution of shift-and-add data, and a phase restoration process. Development of a new camera based on a much lower noise HgCdTe detector will lead to a significant improvement i limiting magnitude for IR speckle interferometry.

  16. Nanoparticle imaging. 3D structure of individual nanocrystals in solution by electron microscopy.

    PubMed

    Park, Jungwon; Elmlund, Hans; Ercius, Peter; Yuk, Jong Min; Limmer, David T; Chen, Qian; Kim, Kwanpyo; Han, Sang Hoon; Weitz, David A; Zettl, A; Alivisatos, A Paul

    2015-07-17

    Knowledge about the synthesis, growth mechanisms, and physical properties of colloidal nanoparticles has been limited by technical impediments. We introduce a method for determining three-dimensional (3D) structures of individual nanoparticles in solution. We combine a graphene liquid cell, high-resolution transmission electron microscopy, a direct electron detector, and an algorithm for single-particle 3D reconstruction originally developed for analysis of biological molecules. This method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution. Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale. Copyright © 2015, American Association for the Advancement of Science.

  17. 3D Nanostructured materials: TiO2 nanoparticles incorporated gellan gum scaffold for photocatalyst and biomedical Applications

    NASA Astrophysics Data System (ADS)

    Hasmizam Razali, Mohd; Arifah Ismail, Nur; Zulkafli, Mohd Farhan Azly Mohd; Anuar Mat Amin, Khairul

    2018-03-01

    A unique three-dimensional (3D) nanostructured gellan gum (GG) is fabricated by incorporating TiO2 nanoparticles (GG + TiO2NPs) scaffold by freeze-drying. The fabricated GG + TiO2NPs were characterized using Fourier transform infrared (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) to study their physiochemical properties. FTIR was used to investigate the intermolecular interactions in the scaffolds. The crystal structure was determined by bulk analysis using XRD and SEM for microstructure observation of scaffold surfaces. The performance of synthesized GG + TiO2NPs scaffold 3D nanostructured materials was evaluated as a photocatalyst for methyl orange (MO) degradation and for biomedical applications. The results showed that the scaffold possessed good photocatalytic activity for removal of methyl orange with 88.24% degradation after 3 h of UV irradiation. The scaffold also induces the cell growth, thus offering a good candidate for biomedical applications.

  18. An ordered array of hierarchical spheres for surface-enhanced Raman scattering detection of traces of pesticide

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoye; Zheng, Peng; Meng, Guowen; Huang, Qing; Zhu, Chuhong; Han, Fangming; Huang, Zhulin; Li, Zhongbo; Wang, Zhaoming; Wu, Nianqiang

    2016-09-01

    An ordered array of hierarchically-structured core-nanosphere@space-layer@shell-nanoparticles has been fabricated for surface-enhanced Raman scattering (SERS) detection. To fabricate this hierarchically-structured chip, a long-range ordered array of Au/Ag-nanospheres is first patterned in the nano-bowls on the planar surface of ordered nanoporous anodic titanium oxide template. A ultra-thin alumina middle space-layer is then conformally coated on the Au/Ag-nanospheres, and Ag-nanoparticles are finally deposited on the surface of the alumina space-layer to form an ordered array of Au/Ag-nanosphere@Al2O3-layer@Ag-nanoparticles. Finite-difference time-domain simulation shows that SERS hot spots are created between the neighboring Ag-nanoparticles. The ordered array of hierarchical nanostructures is used as the SERS-substrate for a trial detection of methyl parathion (a pesticide) in water and a limit of detection of 1 nM is reached, indicating its promising potential in rapid monitoring of organic pollutants in aquatic environment.

  19. Water flattens graphene wrinkles: laser shock wrapping of graphene onto substrate-supported crystalline plasmonic nanoparticle arrays

    PubMed Central

    Hu, Yaowu; Lee, Seunghyun; Kumar, Prashant; Nian, Qiong; Wang, Wenqi; Irudayaraj, Joseph; Cheng, Gary J.

    2018-01-01

    Hot electron injection into an exceptionally high mobility material can be realized in graphene-plasmonic nanoantenna hybrid nanosystems, which can be exploited for several front-edge applications including photovoltaics, plasmonic waveguiding and molecular sensing at trace level. Wrinkling instabilities of graphene on these plasmonic nanostructures, however, would cause reactive oxygen or sulfur species diffuse and react with the materials, decrease charge transfer rate and block intense hot-spots. No ex-situ graphene wrapping technique has been explored so far to control these wrinkles. Here, we present a method to generate seamless integration by using water as a flyer to transfer the laser shock pressure to wrap graphene onto plasmonic nanocrystals. This technique decrease the interfacial gap between graphene and the covered substrate-supported plasmonic nanoparticle arrays, by exploiting a shock pressure generated by laser ablation of graphite and water impermeability nature of graphene. Graphene wrapping of chemically synthesized crystalline gold nanospheres, nanorods and bipyramids with different field confinement capabilities are investigated. A combined experimental and computational method, including SEM and AFM morphological investigation, molecular dynamics simulation, and Raman spectroscopy characterization, is used to demonstrate the effectiveness of this technique. Graphene covered gold bipyramid exhibits the best result among the hybrid nanosystems studied. We have shown that the hybrid system fabricated by laser shock can be used for enhanced molecular sensing. The technique developed has the characteristics of tight integration, chemical/thermal stability, instantaneous, scale and room temperature processing capability, and can be further extended to integrate other 2D material with various 0-3D nanomaterials. PMID:26394237

  20. All-solid-state Z-scheme system arrays of Fe2V4O13/RGO/CdS for visible light-driving photocatalytic CO2 reduction into renewable hydrocarbon fuel.

    PubMed

    Li, Ping; Zhou, Yong; Li, Haijin; Xu, Qinfeng; Meng, Xianguang; Meng, Xiangguang; Wang, Xiaoyong; Xiao, Min; Zou, Zhigang

    2015-01-14

    An all-solid-state Z-scheme system array consisting of an Fe2V4O13 nanoribbon (NR)/reduced graphene oxide (RGO)/CdS nanoparticle grown on the stainless-steel mesh was rationally designed for photoconversion of gaseous CO2 into renewable hydrocarbon fuels (methane: CH4).

  1. 3D imaging LADAR with linear array devices: laser, detector and ROIC

    NASA Astrophysics Data System (ADS)

    Kameyama, Shumpei; Imaki, Masaharu; Tamagawa, Yasuhisa; Akino, Yosuke; Hirai, Akihito; Ishimura, Eitaro; Hirano, Yoshihito

    2009-07-01

    This paper introduces the recent development of 3D imaging LADAR (LAser Detection And Ranging) in Mitsubishi Electric Corporation. The system consists of in-house-made key devices which are linear array: the laser, the detector and the ROIC (Read-Out Integrated Circuit). The laser transmitter is the high power and compact planar waveguide array laser at the wavelength of 1.5 micron. The detector array consists of the low excess noise Avalanche Photo Diode (APD) using the InAlAs multiplication layer. The analog ROIC array, which is fabricated in the SiGe- BiCMOS process, includes the Trans-Impedance Amplifiers (TIA), the peak intensity detectors, the Time-Of-Flight (TOF) detectors, and the multiplexers for read-out. This device has the feature in its detection ability for the small signal by optimizing the peak intensity detection circuit. By combining these devices with the one dimensional fast scanner, the real-time 3D range image can be obtained. After the explanations about the key devices, some 3D imaging results are demonstrated using the single element key devices. The imaging using the developed array devices is planned in the near future.

  2. N-doped carbon@Ni-Al2O3 nanosheet array@graphene oxide composite as an electrocatalyst for hydrogen evolution reaction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Qiu, Tian; Chen, Xu; Lu, Yanluo; Yang, Wensheng

    2015-10-01

    An NiAl-layered double-hydroxide (NiAl-LDH) nanosheet array is grown on a graphene oxide (GO) substrate (NiAl-LDH@GO) by the hydrothermal method. The NiAl-LDH@GO is used as the precursor to synthetize an N-doped carbon@Ni-Al2O3 nanosheet array@GO composite (N-C@Ni-Al2O3@GO) by coating with dopamine followed by calcination. The N-C@Ni-Al2O3@GO is used as a non-noble metal electrocatalyst for hydrogen evolution reaction in alkaline medium, and exhibits high electrocatalytic activity with low onset overpotential (-75 mV). The improved electrocatalytic performance of N-C@Ni-Al2O3@GO arises from its intrinsic features. First, it has a high specific surface area with the Ni nanoparticles in the composite dispersed well and the sizes of Ni nanoparticles are small, which lead to the exposure of more active sites for electrocatalysis. Second, there is a synergistic effect between the Ni nanoparticles and the N-C coating layer, which is beneficial to reduce the activation energy of the Volmer step and improve the electrocatalytic activity. Third, the N-C coating layer and the XC-72 additive can form an electrically conductive network, which serves as a bridge for the transfer of electrons from the electrode to the Ni nanoparticles.

  3. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

    PubMed

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-12-07

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  4. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

    NASA Astrophysics Data System (ADS)

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-11-01

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  5. Arrays of size and distance controlled platinum nanoparticles fabricated by a colloidal method

    NASA Astrophysics Data System (ADS)

    Manzke, Achim; Vogel, Nicolas; Weiss, Clemens K.; Ziener, Ulrich; Plettl, Alfred; Landfester, Katharina; Ziemann, Paul

    2011-06-01

    . Subsequent application of plasma etching and annealing steps allows complete removal of the PS carriers and in parallel nucleation and growth of Pt nanoparticles (NPs) which are located at the original center of the PS colloids. In this way, hexagonally arranged spherical Pt NPs are obtained with controlled size and interparticle distances demonstrating variability and precision with so far unknown parameter scalability. This control is demonstrated by the fabrication of Pt NP arrays at a fixed particle distance of 185 nm while systematically varying the diameters between 8 and 15 nm. Further progress could be achieved by seeded emulsion polymerization. Here, Pt loaded PS colloids of 130 nm were used as seeds for a subsequent additional emulsion polymerization, systematically enlarging the diameter of the PS particles. Applying the plasma and annealing steps as above, in this way hexagonally ordered arrays of 9 nm Pt NPs could be obtained at distances up to 260 nm. To demonstrate their stability, such Pt particles were used as etching masks during reactive ion etching thereby transferring their hexagonal pattern into the Si substrate resulting in corresponding arrays of nanopillars. Electronic supplementary information (ESI) available: Detailed description of the experimental part (S1-S4) platinum concentration inside the polymer particles synthesized by a seeded polymerization from the same seed particles measured by ICP-OES (Fig. S1 and S5); SEM image of Pt complex containing PS particles after oxygen plasma treatment (Fig. S2 and S6); effect of hydrofluoric acid treatment on silicon oxide elevation under Pt NPs (Fig. S3 and S6); SEM images demonstrating the variability of Pt NP distance while keeping the diameter constant (Fig. S4 and S8); results of experimental determination of Pt content by ICP-OES (Tables S1 and S9); diameter of the particles at different fabrication states (Tables S2 and S10). See DOI: 10.1039/c1nr10169b

  6. Self-assembled three-dimensional nanocrown array.

    PubMed

    Hong, Soongweon; Kang, Taewook; Choi, Dukhyun; Choi, Yeonho; Lee, Luke P

    2012-07-24

    Although an ordered nanoplasmonic probe array will have a huge impact on light harvesting, selective frequency response (i.e., nanoantenna), and quantitative molecular/cellular imaging, the realization of such an array is still limited by conventional techniques due to the serial processing or resolution limit by light diffraction. Here, we demonstrate a thermodynamically driven, self-assembled three-dimensional nanocrown array that consists of a core and six satellite gold nanoparticles (GNPs). Our ordered nanoprobe array is fabricated over a large area by thermal dewetting of thin gold film on hexagonally ordered porous anodic alumina (PAA). During thermal dewetting, the structural order of the PAA template dictates the periodic arrangement of gold nanoparticles, rendering the array of gold nanocrown. Because of its tunable size (i.e., 50 nm core and 20 nm satellite GNPs), arrangement, and periodicity, the nanocrown array shows multiple optical resonance frequencies at visible wavelengths as well as angle-dependent optical properties.

  7. BRDF-dependent accuracy of array-projection-based 3D sensors.

    PubMed

    Heist, Stefan; Kühmstedt, Peter; Tünnermann, Andreas; Notni, Gunther

    2017-03-10

    In order to perform high-speed three-dimensional (3D) shape measurements with structured light systems, high-speed projectors are required. One possibility is an array projector, which allows pattern projection at several tens of kilohertz by switching on and off the LEDs of various slide projectors. The different projection centers require a separate analysis, as the intensity received by the cameras depends on the projection direction and the object's bidirectional reflectance distribution function (BRDF). In this contribution, we investigate the BRDF-dependent errors of array-projection-based 3D sensors and propose an error compensation process.

  8. Equivalent-circuit model for stacked slot-based 2D periodic arrays of arbitrary geometry for broadband analysis

    NASA Astrophysics Data System (ADS)

    Astorino, Maria Denise; Frezza, Fabrizio; Tedeschi, Nicola

    2018-03-01

    The analysis of the transmission and reflection spectra of stacked slot-based 2D periodic structures of arbitrary geometry and the ability to devise and control their electromagnetic responses have been a matter of extensive research for many decades. The purpose of this paper is to develop an equivalent Π circuit model based on the transmission-line theory and Floquet harmonic interactions, for broadband and short longitudinal period analysis. The proposed circuit model overcomes the limits of identical and symmetrical configurations imposed by the even/odd excitation approach, exploiting both the circuit topology of a single 2D periodic array of apertures and the ABCD matrix formalism. The transmission spectra obtained through the equivalent-circuit model have been validated by comparison with full-wave simulations carried out with a finite-element commercial electromagnetic solver. This allowed for a physical insight into the spectral and angular responses of multilayer devices with arbitrary aperture shapes, guaranteeing a noticeable saving of computational resources.

  9. Ag-nanoparticles-decorated NiO-nanoflakes grafted Ni-nanorod arrays stuck out of porous AAO as effective SERS substrates.

    PubMed

    Zhou, Qitao; Meng, Guowen; Huang, Qing; Zhu, Chuhong; Tang, Haibin; Qian, Yiwu; Chen, Bin; Chen, Bensong

    2014-02-28

    NiO-nanoflakes (NiO-NFs) grafted Ni-nanorod (Ni-NR) arrays stuck out of the porous anodic aluminum oxide (AAO) template are achieved by a combinatorial process of AAO-confined electrodeposition of Ni-NRs, selectively etching part of the AAO template to expose the Ni-NRs, wet-etching the exposed Ni-NRs in ammonia to obtain Ni(OH)2-NFs grafted onto the cone-shaped Ni-NRs, and annealing to transform Ni(OH)2-NFs in situ into NiO-NFs. By top-view sputtering, Ag-nanoparticles (Ag-NPs) are decorated on each NiO-NFs grafted Ni-NR (denoted as NiO-NFs@Ni-NR). The resultant Ag-NPs-decorated NiO-NFs@Ni-NR (denoted as Ag-NPs@NiO-NFs@Ni-NR) arrays exhibit not only strong surface-enhanced Raman scattering (SERS) activity but also reproducible SERS-signals over the whole array. It is demonstrated that the strong SERS-activity is mainly ascribed to the high density of sub-10 nm gaps (hot spots) between the neighboring Ag-NPs, the semiconducting NiO-NFs induced chemical enhancement effect, and the lightning rod effect of the cone-shaped Ni-NRs. The three-level hierarchical nanostructure arrays stuck out of the AAO template can be utilized to probe polychlorinated biphenyls (PCBs, a kind of global environmental hazard) with a concentration as low as 5 × 10(-6) M, showing promising potential in SERS-based rapid detection of organic environmental pollutants.

  10. The potential of TiO2 nanoparticles as carriers for cadmium uptake in Lumbriculus variegatus and Daphnia magna.

    PubMed

    Hartmann, Nanna B; Legros, Samuel; Von der Kammer, Frank; Hofmann, Thilo; Baun, Anders

    2012-08-15

    The use of engineered nanoparticles (e.g. in industrial applications and consumer products) is increasing. Consequently, these particles will be released into the aquatic environment. Through aggregation/agglomeration and sedimentation, sediments are expected ultimately to be sinks for nanoparticles. Both in the water phase and in the sediments engineered nanoparticles will mix and interact with other environmental pollutants, including metals. In this study the toxicity of cadmium to two freshwater organisms, water column crustacean Daphnia magna and sediment oligochaete Lumbriculus variegatus, was investigated both in the absence and presence of titanium dioxide (TiO(2)) nanoparticles (P25 Evonic Degussa, d: 30 nm). The uptake of cadmium in sub-lethal concentrations was also studied in the absence and presence of 2 mg/L TiO(2) nanoparticles. Formation of larger nanoparticles aggregates/agglomerates was observed and sizes varied depending on media composition (358±13 nm in US EPA moderately hard synthetic freshwater and 1218±7 nm in Elendt M7). TiO(2) nanoparticles are potential carriers for cadmium and it was found that 25% and 6% of the total cadmium mass in the test system for L. variegatus and D. magna tests were associated to suspended TiO(2) particles, respectively. μXRF (micro X-ray fluorescence) analysis confirmed the uptake of TiO(2) in the gut of D. magna. For L. variegatus μXRF analysis indicated attachment of TiO(2) nanoparticles to the organism surface as well as a discrete distribution within the organisms. Though exact localisation in this organism was more difficult to assess, the uptake seems to be within the coelomic cavity. Results show that the overall body burden and toxicity of cadmium to L. variegatus was unchanged by addition of TiO(2) nanoparticles, showing that cadmium adsorption to TiO(2) nanoparticles did not affect overall bioavailability. Despite facilitated uptake of cadmium by TiO(2) nanoparticles in D. magna, resulting in

  11. A Direction Finding Method with A 3-D Array Based on Aperture Synthesis

    NASA Astrophysics Data System (ADS)

    Li, Shiwen; Chen, Liangbing; Gao, Zhaozhao; Ma, Wenfeng

    2018-01-01

    Direction finding for electronic warfare application should provide a wider field of view as possible. But the maximum unambiguous field of view for conventional direction finding methods is a hemisphere. It cannot distinguish the direction of arrival of the signals from the back lobe of the array. In this paper, a full 3-D direction finding method based on aperture synthesis radiometry is proposed. The model of the direction finding system is illustrated, and the fundamentals are presented. The relationship between the outputs of the measurements of a 3-D array and the 3-D power distribution of the point sources can be represented by a 3-D Fourier transform, and then the 3-D power distribution of the point sources can be reconstructed by an inverse 3-D Fourier transform. And in order to display the 3-D power distribution of the point sources conveniently, the whole spherical distribution is represented by two 2-D circular distribution images, one of which is for the upper hemisphere, and the other is for the lower hemisphere. Then a numeric simulation is designed and conducted to demonstrate the feasibility of the method. The results show that the method can estimate the arbitrary direction of arrival of the signals in the 3-D space correctly.

  12. Three-dimensional electrodes for dye-sensitized solar cells: synthesis of indium-tin-oxide nanowire arrays and ITO/TiO2 core-shell nanowire arrays by electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Wen; Ting, Chi-Feng; Hung, Miao-Ken; Chiou, Chwei-Huann; Liu, Ying-Ling; Liu, Zongwen; Ratinac, Kyle R.; Ringer, Simon P.

    2009-02-01

    Dye-sensitized solar cells (DSSCs) show promise as a cheaper alternative to silicon-based photovoltaics for specialized applications, provided conversion efficiency can be maximized and production costs minimized. This study demonstrates that arrays of nanowires can be formed by wet-chemical methods for use as three-dimensional (3D) electrodes in DSSCs, thereby improving photoelectric conversion efficiency. Two approaches were employed to create the arrays of ITO (indium-tin-oxide) nanowires or arrays of ITO/TiO2 core-shell nanowires; both methods were based on electrophoretic deposition (EPD) within a polycarbonate template. The 3D electrodes for solar cells were constructed by using a doctor-blade for coating TiO2 layers onto the ITO or ITO/TiO2 nanowire arrays. A photoelectric conversion efficiency as high as 4.3% was achieved in the DSSCs made from ITO nanowires; this performance was better than that of ITO/TiO2 core-shell nanowires or pristine TiO2 films. Cyclic voltammetry confirmed that the reaction current was significantly enhanced when a 3D ITO-nanowire electrode was used. Better separation of charge carriers and improved charge transport, due to the enlarged interfacial area, are thought to be the major advantages of using 3D nanowire electrodes for the optimization of DSSCs.

  13. Directed assembly of nanoparticles to isolated diatom valves using the non-wetting characteristics after pyrolysis

    NASA Astrophysics Data System (ADS)

    Jantschke, A.; Fischer, C.; Hensel, R.; Braun, H.-G.; Brunner, E.

    2014-09-01

    A novel strategy for a directed nanoparticle coupling to isolated Stephanopyxis turris valves is presented. After pyrolysis, the valves exhibit incomplete wetting due to their characteristic T-shaped profiles as a prerequisite for a regioselective coupling reaction. A micromanipulation system allows for precise handling and their immobilization onto an adhesive substrate and manipulation into arrays.A novel strategy for a directed nanoparticle coupling to isolated Stephanopyxis turris valves is presented. After pyrolysis, the valves exhibit incomplete wetting due to their characteristic T-shaped profiles as a prerequisite for a regioselective coupling reaction. A micromanipulation system allows for precise handling and their immobilization onto an adhesive substrate and manipulation into arrays. Electronic supplementary information (ESI) available: BET surface area, TG/DTA measurements, HIM images and a video of an array of six valves of S. turris in a wetting experiment as well as a 3D animation based on CLSM measurements. See DOI: 10.1039/c4nr02662d

  14. Investigation of the optical and sensing characteristics of nanoparticle arrays for high temperature applications

    NASA Astrophysics Data System (ADS)

    Dharmalingam, Gnanaprakash; Carpenter, Michael A.

    2015-05-01

    Monitoring polluting gases such as CO and NOx emitted from gas turbines in power plants and aircraft is important, in order to both reduce the effects of such gases on the environment as well as to optimize the performance of the respective power system. Fuel cost savings as well as a reduced environmental impact can be realized if air traffic utilized next generation jet turbines with an emission/performance control sensing system. These monitoring systems must be sensitive and selective to gases as well as be reliable and stable under harsh environmental conditions where the operation temperatures are in excess of 500 °C within a highly reactive environment. In this work, plasmonics based chemical sensors with nanocomposites of a combination of gold nano particles and Yttria Stabilized Zirconia (YSZ) has enabled the sensitive (PPM) and stable detection (100s of hrs.) of H2, NO2 and CO at temperatures of 500 °C. Selectivity remains a challenging parameter to optimize and a layer by layer sputter deposition approach has been recently demonstrated to modify the resulting sensing properties through a change in the morphology of the deposited films. It is expected that further enhancements would be realized through control of the shape and geometry of the catalytically active Au nanoparticles. This level of control has been realized through the use of electron beam lithography to fabricate nanocomposite arrays. Sensing results towards the detection of H2 will be highlighted with specific concerns related to optimization of these nanorod arrays detailed.

  15. Integrated circuits for volumetric ultrasound imaging with 2-D CMUT arrays.

    PubMed

    Bhuyan, Anshuman; Choe, Jung Woo; Lee, Byung Chul; Wygant, Ira O; Nikoozadeh, Amin; Oralkan, Ömer; Khuri-Yakub, Butrus T

    2013-12-01

    Real-time volumetric ultrasound imaging systems require transmit and receive circuitry to generate ultrasound beams and process received echo signals. The complexity of building such a system is high due to requirement of the front-end electronics needing to be very close to the transducer. A large number of elements also need to be interfaced to the back-end system and image processing of a large dataset could affect the imaging volume rate. In this work, we present a 3-D imaging system using capacitive micromachined ultrasonic transducer (CMUT) technology that addresses many of the challenges in building such a system. We demonstrate two approaches in integrating the transducer and the front-end electronics. The transducer is a 5-MHz CMUT array with an 8 mm × 8 mm aperture size. The aperture consists of 1024 elements (32 × 32) with an element pitch of 250 μm. An integrated circuit (IC) consists of a transmit beamformer and receive circuitry to improve the noise performance of the overall system. The assembly was interfaced with an FPGA and a back-end system (comprising of a data acquisition system and PC). The FPGA provided the digital I/O signals for the IC and the back-end system was used to process the received RF echo data (from the IC) and reconstruct the volume image using a phased array imaging approach. Imaging experiments were performed using wire and spring targets, a ventricle model and a human prostrate. Real-time volumetric images were captured at 5 volumes per second and are presented in this paper.

  16. A beamforming study for implementation of vibro-acoustography with a 1.75-D array transducer.

    PubMed

    Urban, Matthew W; Chalek, Carl; Haider, Bruno; Thomenius, Kai E; Fatemi, Mostafa; Alizad, Azra

    2013-03-01

    Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using 1-D linear-array transducers. In this article, we discuss VA beamforming and image formation using a 1.75-D array transducer. A 1.75-D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75-D array over a 1-D linear-array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75-D array transducer offers several advantages over scanning with a linear-array transducer, including improved image resolution and contrast resulting from better elevation focusing of the imaging point-spread function.

  17. A Beamforming Study for Implementation of Vibro-acoustography with a 1.75D Array Transducer

    PubMed Central

    Urban, Matthew W.; Chalek, Carl; Haider, Bruno; Thomenius, Kai E.; Fatemi, Mostafa; Alizad, Azra

    2013-01-01

    Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using one-dimensional (1D) linear array transducers. In this article, we discuss VA beamforming and image formation using a 1.75D array transducer. A 1.75D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75D array over a 1D linear array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75D array transducer offers several advantages over scanning with a linear array transducer including improved image resolution and contrast due to better elevation focusing of the imaging point-spread function. PMID:23475919

  18. Immobilization of Ag nanoparticles/FGF-2 on a modified titanium implant surface and improved human gingival fibroblasts behavior.

    PubMed

    Ma, Qianli; Mei, Shenglin; Ji, Kun; Zhang, Yumei; Chu, Paul K

    2011-08-01

    The objective of this study was to form a rapid and firm soft tissue sealing around dental implants that resists bacterial invasion. We present a novel approach to modify Ti surface by immobilizing Ag nanoparticles/FGF-2 compound bioactive factors onto a titania nanotubular surface. The titanium samples were anodized to form vertically organized TiO(2) nanotube arrays and Ag nanoparticles were electrodeposited onto the nanotubular surface, on which FGF-2 was immobilized with repeated lyophilization. A uniform distribution of Ag nanoparticles/FGF-2 was observed on the TiO(2) nanotubular surface. The L929 cell line was used for cytotoxicity assessment. Human gingival fibroblasts (HGFs) were cultured on the modified surface for cytocompatibility determination. The Ag/FGF-2 immobilized samples displayed excellent cytocompatibility, negligible cytotoxicity, and enhanced HGF functions such as cell attachment, proliferation, and ECM-related gene expression. The Ag nanoparticles also exhibit some bioactivity. In conclusion, this modified TiO(2) nanotubular surface has a large potential for use in dental implant abutment. Copyright © 2011 Wiley Periodicals, Inc.

  19. The influence of molecular mobility on the properties of networks of gold nanoparticles and organic ligands

    PubMed Central

    Kamalakar, M Venkata; Prendergast, Úna; Kübel, Christian; Lemma, Tibebe; Dayen, Jean-François

    2014-01-01

    Summary We prepare and investigate two-dimensional (2D) single-layer arrays and multilayered networks of gold nanoparticles derivatized with conjugated hetero-aromatic molecules, i.e., S-(4-{[2,6-bipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)thiolate (herein S-BPP), as capping ligands. These structures are fabricated by a combination of self-assembly and microcontact printing techniques, and are characterized by electron microscopy, UV–visible spectroscopy and Raman spectroscopy. Selective binding of the S-BPP molecules to the gold nanoparticles through Au–S bonds is found, with no evidence for the formation of N–Au bonds between the pyridine or pyrazole groups of BPP and the gold surface. Subtle, but significant shifts with temperature of specific Raman S-BPP modes are also observed. We attribute these to dynamic changes in the orientation and/or increased mobility of the molecules on the gold nanoparticle facets. As for their conductance, the temperature-dependence for S-BPP networks differs significantly from standard alkanethiol-capped networks, especially above 220 K. Relating the latter two observations, we propose that dynamic changes in the molecular layers effectively lower the molecular tunnel barrier for BPP-based arrays at higher temperatures. PMID:25383278

  20. The influence of molecular mobility on the properties of networks of gold nanoparticles and organic ligands.

    PubMed

    Devid, Edwin J; Martinho, Paulo N; Kamalakar, M Venkata; Prendergast, Úna; Kübel, Christian; Lemma, Tibebe; Dayen, Jean-François; Keyes, Tia E; Doudin, Bernard; Ruben, Mario; van der Molen, Sense Jan

    2014-01-01

    We prepare and investigate two-dimensional (2D) single-layer arrays and multilayered networks of gold nanoparticles derivatized with conjugated hetero-aromatic molecules, i.e., S-(4-{[2,6-bipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)thiolate (herein S-BPP), as capping ligands. These structures are fabricated by a combination of self-assembly and microcontact printing techniques, and are characterized by electron microscopy, UV-visible spectroscopy and Raman spectroscopy. Selective binding of the S-BPP molecules to the gold nanoparticles through Au-S bonds is found, with no evidence for the formation of N-Au bonds between the pyridine or pyrazole groups of BPP and the gold surface. Subtle, but significant shifts with temperature of specific Raman S-BPP modes are also observed. We attribute these to dynamic changes in the orientation and/or increased mobility of the molecules on the gold nanoparticle facets. As for their conductance, the temperature-dependence for S-BPP networks differs significantly from standard alkanethiol-capped networks, especially above 220 K. Relating the latter two observations, we propose that dynamic changes in the molecular layers effectively lower the molecular tunnel barrier for BPP-based arrays at higher temperatures.

  1. Fabrication of flexible MoS2 thin-film transistor arrays for practical gas-sensing applications.

    PubMed

    He, Qiyuan; Zeng, Zhiyuan; Yin, Zongyou; Li, Hai; Wu, Shixin; Huang, Xiao; Zhang, Hua

    2012-10-08

    By combining two kinds of solution-processable two-dimensional materials, a flexible transistor array is fabricated in which MoS(2) thin film is used as the active channel and reduced graphene oxide (rGO) film is used as the drain and source electrodes. The simple device configuration and the 1.5 mm-long MoS(2) channel ensure highly reproducible device fabrication and operation. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS(2) thin film with Pt nanoparticles further increases the sensitivity by up to ∼3 times. The successful incorporation of a MoS(2) thin-film into the electronic sensor promises its potential application in various electronic devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Uniform and nonuniform V-shaped planar arrays for 2-D direction-of-arrival estimation

    NASA Astrophysics Data System (ADS)

    Filik, T.; Tuncer, T. E.

    2009-10-01

    In this paper, isotropic and directional uniform and nonuniform V-shaped arrays are considered for azimuth and elevation direction-of-arrival (DOA) angle estimation simultaneously. It is shown that the uniform isotropic V-shaped arrays (UI V arrays) have no angle coupling between the azimuth and elevation DOA. The design of the UI V arrays is investigated, and closed form expressions are presented for the parameters of the UI V arrays and nonuniform V arrays. These expressions allow one to find the isotropic V angle for different array types. The DOA performance of the UI V array is compared with the uniform circular array (UCA) for correlated signals and in case of mutual coupling between array elements. The modeling error for the sensor positions is also investigated. It is shown that V array and circular array have similar robustness for the position errors while the performance of UI V array is better than the UCA for correlated source signals and when there is mutual coupling. Nonuniform V-shaped isotropic arrays are investigated which allow good DOA performance with limited number of sensors. Furthermore, a new design method for the directional V-shaped arrays is proposed. This method is based on the Cramer-Rao Bound for joint estimation where the angle coupling effect between the azimuth and elevation DOA angles is taken into account. The design method finds an optimum angle between the linear subarrays of the V array. The proposed method can be used to obtain directional arrays with significantly better DOA performance.

  3. Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

    2015-10-01

    Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10-7 M and 10-5 M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform

  4. A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom.

    PubMed

    Lye, Jessica; Kenny, John; Lehmann, Joerg; Dunn, Leon; Kron, Tomas; Alves, Andrew; Cole, Andrew; Williams, Ivan

    2014-10-01

    The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%-8%. The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to facilities modifying clinical practice and

  5. A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lye, Jessica; Dunn, Leon, E-mail: leon.dunn@arpansa.gov.au; Alves, Andrew

    Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantomsmore » are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have

  6. Fabrication of self-assembled (-)-epigallocatechin gallate (EGCG) ovalbumin-dextran conjugate nanoparticles and their transport across monolayers of human intestinal epithelial Caco-2 cells.

    PubMed

    Li, Zheng; Gu, Liwei

    2014-02-12

    Nanoparticles have the potential to increase bioavailability of nutraceutical compounds such as (-)-epigallocatechin gallate (EGCG). Ovalbumin was conjugated with dextran using the Maillard reaction. The resultant ovalbumin-dextran (O-D) conjugates were self-assembled with EGCG to form EGCG O-D conjugate nanoparticles at pH 5.2 after heating at 80 °C for 60 min. Ovalbumin in EGCG O-D conjugate nanoparticles was further cross-linked by glutaraldehyde for 24 h at room temperature. EGCG O-D conjugate nanoparticles and cross-linked EGCG O-D conjugate nanoparticles in aqueous suspension had particle sizes of 285 and 339 nm, respectively, and showed a spherical morphology. The loading efficiencies of EGCG in these two nanoparticles were 23.4 and 30.0%, whereas the loading capacities were 19.6 and 20.9%, respectively. These nanoparticles showed positive zeta-potentials in a pH range from 2.5 to 4.0 but had negative charges at pH ≥5.0. EGCG O-D conjugate nanoparticles maintained a particle size of 183-349 nm in simulated gastric fluid (SGF) and 188-291 nm in simulated intestinal fluid (SIF) at 37 °C for 2 h, whereas cross-linked nanoparticles had particle sizes of 294-527 nm in SGF and 206-300 nm in SIF. Limited release of EGCG was observed in both nanoparticle systems in simulated gastric and intestinal fluids without and with digestive enzymes. EGCG O-D conjugate nanoparticles significantly enhanced the apparent permeability coefficient (Papp) of EGCG on Caco-2 monolayers compared with EGCG solution, suggesting that these nanoparticles may improve the absorption of EGCG.

  7. Zinc cobalt sulfide nanosheets array derived from 2D bimetallic metal-organic frameworks for high-performance supercapacitor.

    PubMed

    Tao, Kai; Han, Xue; Cheng, Qiuhui; Yang, Yujing; Yang, Zheng; Ma, Qingxiang; Han, Lei

    2018-04-19

    Porous ternary metal sulfide integrated electrode materials with abundant electroactive sites and redox reactions are very promising for supercapacitors. Here, porous zinc cobalt sulfide nanosheets array on Ni foam (Zn-Co-S/NF) has been successfully constructed by a facile growth of 2D bimetallic zinc/cobalt-based metal-organic frameworks (Zn/Co-MOF) nanosheets with leaf-like morphology on Ni foam, followed by additional sulfurization. The Zn-Co-S/NF nanosheets array is directly acted as an electrode for supercapacitor, showing much better electrochemical performance (2354.3 F g-1 and 88.6% retention over 1000 cycles) when compared with zinc cobalt sulfide powder (355.3 F g-1 and 75.8% retention over 1000 cycles), which is originated from good electric conductivity and mechanical stability, abundant electroactive sites, and facilitated transportation of electron and electrolyte ion endowed by the unique nanosheets array structure. The asymmetric supercapacitor (ASC) device assembled from Zn-Co-S/NF and activated carbon electrodes can deliver the highest energy density of 31.9 Wh kg-1 and the maximum power density of 8.5 kW kg-1. Most importantly, this ASC also presents good cycling stability (97% retention over 1000 cycles). Furthermore, a red light-emitting diode (LED) can be illuminated by two connected ASCs, indicating that as-synthesized Zn-Co-S/NF hold great potential for practical applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Fabrication of 3D Reconstituted Organoid Arrays by DNA-programmed Assembly of Cells (DPAC)

    PubMed Central

    Todhunter, Michael E; Weber, Robert J; Farlow, Justin; Jee, Noel Y; Cerchiari, Alec E; Gartner, Zev J

    2016-01-01

    Tissues are the organizational units of function in metazoan organisms. Tissues comprise an assortment of cellular building blocks, soluble factors, and extracellular matrix (ECM) that are composed into specific three dimensional (3D) structures. The capacity to reconstitute tissues in vitro with the structural complexity observed in vivo is key to understanding processes such as morphogenesis, homeostasis, and disease. In this unit, we describe DNA-programmed Assembly of Cells (DPAC), a method to fabricate viable, functional arrays of organoid-like tissues within 3D ECM gels. In DPAC, dissociated cells are chemically functionalized with degradable oligonucleotide “velcro,” allowing rapid, specific, and reversible cell adhesion to a two-dimensional (2D) template patterned with complementary DNA. An iterative assembly process builds up organoids, layer-by-layer, from this initial 2D template and into the third dimension. Cleavage of the DNA releases the completed array of tissues that are captured and fully embedded in ECM gels for culture and observation. DPAC controls the size, shape, composition, and spatial heterogeneity of organoids, and permits positioning constituent cells with single-cell resolution even within cultures several centimeters long. PMID:27622567

  9. Toward more efficient fabrication of high-density 2-D VCSEL arrays for spatial redundancy and/or multi-level signal communication

    NASA Astrophysics Data System (ADS)

    Roscher, Hendrik; Gerlach, Philipp; Khan, Faisal Nadeem; Kroner, Andrea; Stach, Martin; Weigl, Alexander; Michalzik, Rainer

    2006-04-01

    We present flip-chip attached high-speed VCSELs in 2-D arrays with record-high intra-cell packing densities. The advances of VCSEL array technology toward improved thermal performance and more efficient fabrication are reviewed, and the introduction of self-aligned features to these devices is pointed out. The structure of close-spaced wedge-shaped VCSELs is discussed and their static and dynamic characteristics are presented including an examination of the modal structure by near-field measurements. The lasers flip-chip bonded to a silicon-based test platform exhibit 3-dB and 10-dB bandwidths of 7.7 GHz and 9.8 GHz, respectively. Open 12.5 Gbit/s two-level eye patterns are demonstrated. We discuss the uses of high packing densities for the increase of the total amount of data throughput an array can deliver in the course of its life. One such approach is to provide up to two backup VCSELs per fiber channel that can extend the lifetimes of parallel transmitters through redundancy of light sources. Another is to increase the information density by using multiple VCSELs per 50 μm core diameter multimode fiber to generate more complex signals. A novel scheme using three butt-coupled VCSELs per fiber for the generation of four-level signals in the optical domain is proposed. First experiments are demonstrated using two VCSELs butt-coupled to the same standard glass fiber, each modulated with two-level signals to produce four-level signals at the photoreceiver. A four-level direct modulation of one VCSEL within a triple of devices produced first 20.6 Gbit/s (10.3 Gsymbols/s) four-level eyes, leaving two VCSELs as backup sources.

  10. Dynamics of magnetic particles in cylindrical Halbach array: implications for magnetic cell separation and drug targeting.

    PubMed

    Babinec, Peter; Krafcík, Andrej; Babincová, Melánia; Rosenecker, Joseph

    2010-08-01

    Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology. In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets. Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations--Newton law. Computations were done for nanoparticles Nanomag-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 1.4 microm, which can be used for magnetic separation. Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications.

  11. 2D stepping drive for hyperspectral systems

    NASA Astrophysics Data System (ADS)

    Endrödy, Csaba; Mehner, Hannes; Grewe, Adrian; Sinzinger, Stefan; Hoffmann, Martin

    2015-07-01

    We present the design, fabrication and characterization of a compact 2D stepping microdrive for pinhole array positioning. The miniaturized solution enables a highly integrated compact hyperspectral imaging system. Based on the geometry of the pinhole array, an inch-worm drive with electrostatic actuators was designed resulting in a compact (1 cm2) positioning system featuring a step size of about 15 µm in a 170 µm displacement range. The high payload (20 mg) as required for the pinhole array and the compact system design exceed the known electrostatic inch-worm-based microdrives.

  12. Dragon Ears airborne acoustic array: CSP analysis applied to cross array to compute real-time 2D acoustic sound field

    NASA Astrophysics Data System (ADS)

    Cerwin, Steve; Barnes, Julie; Kell, Scott; Walters, Mark

    2003-09-01

    This paper describes development and application of a novel method to accomplish real-time solid angle acoustic direction finding using two 8-element orthogonal microphone arrays. The developed prototype system was intended for localization and signature recognition of ground-based sounds from a small UAV. Recent advances in computer speeds have enabled the implementation of microphone arrays in many audio applications. Still, the real-time presentation of a two-dimensional sound field for the purpose of audio target localization is computationally challenging. In order to overcome this challenge, a crosspower spectrum phase1 (CSP) technique was applied to each 8-element arm of a 16-element cross array to provide audio target localization. In this paper, we describe the technique and compare it with two other commonly used techniques; Cross-Spectral Matrix2 and MUSIC3. The results show that the CSP technique applied to two 8-element orthogonal arrays provides a computationally efficient solution with reasonable accuracy and tolerable artifacts, sufficient for real-time applications. Additional topics include development of a synchronized 16-channel transmitter and receiver to relay the airborne data to the ground-based processor and presentation of test data demonstrating both ground-mounted operation and airborne localization of ground-based gunshots and loud engine sounds.

  13. Superparamagnetic iron oxide nanoparticles alter expression of obesity and T2D-associated risk genes in human adipocytes

    NASA Astrophysics Data System (ADS)

    Sharifi, S.; Daghighi, S.; Motazacker, M. M.; Badlou, B.; Sanjabi, B.; Akbarkhanzadeh, A.; Rowshani, A. T.; Laurent, S.; Peppelenbosch, M. P.; Rezaee, F.

    2013-07-01

    Adipocytes hypertrophy is the main cause of obesity and its affliction such as type 2 diabetes (T2D). Since superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical/medical applications, we aimed to study the effect of SPIONs on 22 and 29 risk genes (Based on gene wide association studies) for obesity and T2D in human adipocytes. The mRNA expression of lipid and glucose metabolism genes was changed upon the treatment of human primary adipocytes with SPIONs. mRNA of GULP1, SLC30A8, NEGR1, SEC16B, MTCH2, MAF, MC4R, and TMEM195 were severely induced, whereas INSIG2, NAMPT, MTMR9, PFKP, KCTD15, LPL and GNPDA2 were down-regulated upon SPIONs stimulation. Since SEC16B gene assist the phagocytosis of apoptotic cells and this gene were highly expressed upon SPIONs treatment in adipocytes, it is logic to assume that SPIONs may play a crucial role in this direction, which requires more consideration in the future.

  14. Hybrid chalcogenide nanoparticles: 2D-WS2 nanocrystals inside nested WS2 fullerenes.

    PubMed

    Hoshyargar, Faegheh; Corrales, Tomas P; Branscheid, Robert; Kolb, Ute; Kappl, Michael; Panthöfer, Martin; Tremel, Wolfgang

    2013-10-28

    The MOCVD assisted formation of nested WS2 inorganic fullerenes (IF-WS2) was performed by enhancing surface diffusion with iodine, and fullerene growth was monitored by taking TEM snapshots of intermediate products. The internal structure of the core-shell nanoparticles was studied using scanning electron microscopy (SEM) after cross-cutting with a focused ion beam (FIB). Lamellar reaction intermediates were found occluded in the fullerene particles. In contrast to carbon fullerenes, layered metal chalcogenides prefer the formation of planar, plate-like structures where the dangling bonds at the edges are stabilized by excess S atoms. The effects of the reaction and annealing temperatures on the composition and morphology of the final product were investigated, and the strength of the WS2 shell was measured by intermittent contact-mode AFM. The encapsulated lamellar structures inside the hollow spheres may lead to enhanced tribological activities.

  15. SU-E-T-163: Characterization of a Novel High Resolution 1D Silicon Monolithic Array for Small Field Commissioning and Quality Assurance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bisello, F; IBA Dosimetry, Schwarzenbruck, DE; McGlade, J

    2015-06-15

    Purpose: To study the suitability of a novel 1D silicon monolithic array for dosimetry of small radiation fields and for QA of high dose gradient treatment modalities (IMRT and SBRT). Methods: A 1D array composed of 4 monolithic silicon modules of 64 mm length and 1 mm pixel pitch was developed by IBA Dosimetry. Measurements were carried out for 6MV and 15MV photons on two commercial different linacs (TrueBeam and Clinac iX, Varian Medical Systems, Palo Alto, CA) and for a CyberKnife G4 (Accuray Inc., Sunnyvale, CA). The 1D array was used to measure output factors (OF), profiles and offmore » axis correction factors (OACF) for the Iris CyberKnife variable collimator (5–60 mm). In addition, dose profiles (at the isocenter plane) were measured for multiple IMRT and SBRT treatment plans and compared with those obtained using EDR2radiographic film (Carestream Health, Rochester NY), a commercial 2D diode array and with the dose distribution calculated using a commercial TPS (Eclipse, Varian Medical Systems, Palo Alto, CA). Results: Due to the small pixel pitch of the detector, IMRT and SBRT plan profiles deviate from film measurements by less than 2%. Similarly, the 1D array exhibits better performance than the 2D diode array due to the larger (7 mm) pitch of that device. Iris collimator OFs measured using the 1D silicon array are in good agreement with the commissioning values obtained using a commercial stereotactic diode as well as with published data. Maximum deviations are < 3% for the smallest field (5 and 7.5mm) and below 1% for all other dimensions. Conclusion: We have demonstrated good performances of the array for commissioning of small photon fields and in patient QA, compared with diodes and film typically used in these clinical applications. The technology compares favorably with existing commercial solutions The presenting author is founded by a Marie Curie Early Initial Training Network Fellowship of the European Communitys Seventh Framework Programme

  16. Development of New Lipid-Based Paclitaxel Nanoparticles Using Sequential Simplex Optimization

    PubMed Central

    Dong, Xiaowei; Mattingly, Cynthia A.; Tseng, Michael; Cho, Moo; Adams, Val R.; Mumper, Russell J.

    2008-01-01

    The objective of these studies was to develop Cremophor-free lipid-based paclitaxel (PX) nanoparticle formulations prepared from warm microemulsion precursors. To identify and optimize new nanoparticles, experimental design was performed combining Taguchi array and sequential simplex optimization. The combination of Taguchi array and sequential simplex optimization efficiently directed the design of paclitaxel nanoparticles. Two optimized paclitaxel nanoparticles (NPs) were obtained: G78 NPs composed of glyceryl tridodecanoate (GT) and polyoxyethylene 20-stearyl ether (Brij 78), and BTM NPs composed of Miglyol 812, Brij 78 and D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS). Both nanoparticles successfully entrapped paclitaxel at a final concentration of 150 μg/ml (over 6% drug loading) with particle sizes less than 200 nm and over 85% of entrapment efficiency. These novel paclitaxel nanoparticles were stable at 4°C over three months and in PBS at 37°C over 102 hours as measured by physical stability. Release of paclitaxel was slow and sustained without initial burst release. Cytotoxicity studies in MDA-MB-231 cancer cells showed that both nanoparticles have similar anticancer activities compared to Taxol®. Interestingly, PX BTM nanocapsules could be lyophilized without cryoprotectants. The lyophilized powder comprised only of PX BTM NPs in water could be rapidly rehydrated with complete retention of original physicochemical properties, in-vitro release properties, and cytotoxicity profile. Sequential Simplex Optimization has been utilized to identify promising new lipid-based paclitaxel nanoparticles having useful attributes. PMID:19111929

  17. Ultraviolet and Visible Photochemistry of Methanol at 3D Mesoporous Networks: TiO2 and Au-TiO2

    DTIC Science & Technology

    2013-05-23

    methanol photochemistry at three-dimensionally (3D) networked aerogels of TiO2 or Au–TiO2 reveals that incorporated Au nanoparticles strongly sensitize...the oxide nanoarchitecture to visible light. Methanol dissociatively adsorbs at the surfaces of TiO2 and Au–TiO2 aerogels under dark, high-vacuum...photochemistry at three-dimensionally (3D) networked aerogels of TiO2 or Au–TiO2 reveals that incorporated Au nanoparticles strongly sensitize the oxide

  18. Effect of Size-Dependent Thermal Instability on Synthesis of Zn2 SiO4-SiOx Core–Shell Nanotube Arrays and Their Cathodoluminescence Properties

    PubMed Central

    2010-01-01

    Vertically aligned Zn2SiO4-SiOx(x < 2) core–shell nanotube arrays consisting of Zn2SiO4-nanoparticle chains encapsulated into SiOx nanotubes and SiOx-coated Zn2SiO4 coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW) arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of “etching” to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn2SiO4-SiOx coaxial nanotubes, single-crystalline Zn2SiO4-nanoparticle-chain-embedded SiOx nanotubes, and single-crystalline Zn2SiO4-SiOx coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL) spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn2SiO4 phase. PMID:20672064

  19. Innovative Techniques for the Production of Low Cost 2D Laser Diode Arrays

    DTIC Science & Technology

    1991-11-26

    electrically isolated and liquid cooled. (Deliverables: 5 5-bar arrays.) The following global issues not mentioned above will be investigated...house facet coating station. All global issues mentioned in Section 2.0 will be addressed and continuously investigated during this program. Very

  20. Simulation and characterization of silicon nanopillar-based nanoparticle sensors

    NASA Astrophysics Data System (ADS)

    Wasisto, Hutomo Suryo; Merzsch, Stephan; Huang, Kai; Stranz, Andrej; Waag, Andreas; Peiner, Erwin

    2013-05-01

    Nanopillar-based structures hold promise as highly sensitive resonant mass sensors for a new generation of aerosol nanoparticle (NP) detecting devices because of their very small masses. In this work, the possible use of a silicon nanopillar (SiNPL) array as a nanoparticle sensor is investigated. The sensor structures are created and simulated using a finite element modeling (FEM) tool of COMSOL Multiphysics 4.3 to study the resonant characteristics and the sensitivity of the SiNPL for femtogram NP mass detection. Instead of using 2D plate models or simple single 3D cylindrical pillar models, FEM is performed with SiNPLs in 3D structures based on the real geometry of experimental SiNPL arrays employing a piezoelectric stack for resonant excitation. In order to achieve an optimal structure and investigate the etching effect on the fabricated resonators, SiNPLs with different designs of meshes, sidewall profiles, lengths, and diameters are simulated and analyzed. To validate the FEM results, fabricated SiNPLs with a high aspect ratio of ~60 are employed and characterized in resonant frequency measurements. SiNPLs are mounted onto a piezoactuator inside a scanning electron microscope (SEM) chamber which can excite SiNPLs into lateral vibration. The measured resonant frequencies of the SiNPLs with diameters about 650 nm and heights about 40 μm range from 434.63 kHz to 458.21 kHz, which agree well with those simulated by FEM. Furthermore, the deflection of a SiNPL can be enhanced by increasing the applied piezoactuator voltage. By depositing different NPs (i.e., carbon, TiO2, SiO2, Ag, and Au NPs) on the SiNPLs, the decrease of the resonant frequency is clearly shown confirming their potential to be used as airborne NP mass sensor with femtogram resolution level.

  1. Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles

    PubMed Central

    Han, Luyang; Biskupek, Johannes; Kaiser, Ute; Ziemann, Paul

    2010-01-01

    Summary Monatomic (Fe, Co) and bimetallic (FePt and CoPt) nanoparticles were prepared by exploiting the self-organization of precursor loaded reverse micelles. Achievements and limitations of the preparation approach are critically discussed. We show that self-assembled metallic nanoparticles can be prepared with diameters d = 2–12 nm and interparticle distances D = 20–140 nm on various substrates. Structural, electronic and magnetic properties of the particle arrays were characterized by several techniques to give a comprehensive view of the high quality of the method. For Co nanoparticles, it is demonstrated that magnetostatic interactions can be neglected for distances which are at least 6 times larger than the particle diameter. Focus is placed on FePt alloy nanoparticles which show a huge magnetic anisotropy in the L10 phase, however, this is still less by a factor of 3–4 when compared to the anisotropy of the bulk counterpart. A similar observation was also found for CoPt nanoparticles (NPs). These results are related to imperfect crystal structures as revealed by HRTEM as well as to compositional distributions of the prepared particles. Interestingly, the results demonstrate that the averaged effective magnetic anisotropy of FePt nanoparticles does not strongly depend on size. Consequently, magnetization stability should scale linearly with the volume of the NPs and give rise to a critical value for stability at ambient temperature. Indeed, for diameters above 6 nm such stability is observed for the current FePt and CoPt NPs. Finally, the long-term conservation of nanoparticles by Au photoseeding is presented. PMID:21977392

  2. One-dimensional array of gold nanoparticles fabricated using biotemplate and its application to fine FET

    NASA Astrophysics Data System (ADS)

    Ban, Takahiko; Uenuma, Mutsunori; Migita, Shinji; Okamoto, Naofumi; Ishikawa, Yasuaki; Uraoka, Yukiharu; Yamashita, Ichiro; Yamamoto, Shin-ichi

    2018-06-01

    By synthesizing AuS nanoparticles (NPs) with spherical shell protein (ferritin) and using a V-groove, a one-dimensional array of NPs was formed at the bottom of the V-groove. It has been reported that AuS NPs are converted to Au NPs by UV/ozone treatment. Floating gate memory (FGM) was fabricated by applying this one-dimensional array to V-grooved junctionless (JL) FETs, V-grooved nin-like-type FETs, and pip-like-type FETs, which are fine FETs. In JL-FETs, it is considered that conversion occurred because of good charge storage efficiency, and operation in the opposite direction to normal FGM operation was seen. In the nin-like and pip-like types devices, the same operation as in conventional FGM was shown, and the width of the memory window was about the same size as when one electron entered one NP. The one-dimensional arrangement of the metal NPs used in this study is considered to be applicable to various fields of nanotechnology.

  3. Combinatorial fabrication and screening of organic light-emitting device arrays

    NASA Astrophysics Data System (ADS)

    Shinar, Joseph; Shinar, Ruth; Zhou, Zhaoqun

    2007-11-01

    The combinatorial fabrication and screening of 2-dimensional (2-d) small molecular UV-violet organic light-emitting device (OLED) arrays, 1-d blue-to-red arrays, 1-d intense white OLED libraries, 1-d arrays to study Förster energy transfer in guest-host OLEDs, and 2-d arrays to study exciplex emission from OLEDs is described. The results demonstrate the power of combinatorial approaches for screening OLED materials and configurations, and for studying their basic properties.

  4. SU-E-T-83: A Study On Evaluating the Directional Dependency of 2D Seven 29 Ion Chamber Array Clinically with Different IMRT Plans

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Syam; Aswathi, C.P.

    Purpose: To evaluate the directional dependency of 2D seven 29 ion chamber array clinically with different IMRT plans. Methods: 25 patients already treated with IMRT plans were selected for the study. Verification plans were created for each treatment plan in eclipse 10 treatment planning system using the AAA algorithm with the 2D array and the Octavius CT phantom. Verification plans were done 2 times for a single patient. First plan with real IMRT (plan-related approach) and second plan with zero degree gantry angle (field-related approach). Measurements were performed on a Varian Clinac-iX, linear accelerator equipped with a millennium 120 multileafmore » collimator. Fluence was measured for all the delivered plans and analyzed using the verisoft software. Comparison was done by selecting the fluence delivered in static gantry (zero degree gantry) versus IMRT with real gantry angles. Results: The gamma pass percentage is greater than 97 % for all IMRT delivered with zero gantry angle and between 95%–98% for real gantry angles. Dose difference between the TPS calculated and measured for IMRT delivered with zero gantry angle was found to be between (0.03 to 0.06Gy) and with real gantry angles between (0.02 to 0.05Gy). There is a significant difference between the gamma analysis between the zero degree and true angle with a significance of 0.002. Standard deviation of gamma pass percentage between the IMRT plans with zero gantry angle was 0.68 and for IMRT with true gantry angle was found to be 0.74. Conclusion: The gamma analysis for IMRT with zero degree gantry angles shows higher pass percentage than IMRT delivered with true gantry angles. Verification plans delivered with true gantry angles lower the verification accuracy when 2D array is used for measurement.« less

  5. Super non-linear RRAM with ultra-low power for 3D vertical nano-crossbar arrays.

    PubMed

    Luo, Qing; Xu, Xiaoxin; Liu, Hongtao; Lv, Hangbing; Gong, Tiancheng; Long, Shibing; Liu, Qi; Sun, Haitao; Banerjee, Writam; Li, Ling; Gao, Jianfeng; Lu, Nianduan; Liu, Ming

    2016-08-25

    Vertical crossbar arrays provide a cost-effective approach for high density three-dimensional (3D) integration of resistive random access memory. However, an individual selector device is not allowed to be integrated with the memory cell separately. The development of V-RRAM has impeded the lack of satisfactory self-selective cells. In this study, we have developed a high performance bilayer self-selective device using HfO2 as the memory switching layer and a mixed ionic and electron conductor as the selective layer. The device exhibits high non-linearity (>10(3)) and ultra-low half-select leakage (<0.1 pA). A four layer vertical crossbar array was successfully demonstrated based on the developed self-selective device. High uniformity, ultra-low leakage, sub-nA operation, self-compliance, and excellent read/write disturbance immunity were achieved. The robust array level performance shows attractive potential for low power and high density 3D data storage applications.

  6. Chitosan nanoparticle-based delivery of fused NKG2D–IL-21 gene suppresses colon cancer growth in mice

    PubMed Central

    Tan, Lunmei; Han, Sen; Ding, Shizhen; Xiao, Weiming; Ding, Yanbing; Qian, Li; Wang, Chenming; Gong, Weijuan

    2017-01-01

    Nanoparticles can be loaded with exogenous DNA for the potential expression of cytokines with immune-stimulatory function. NKG2D identifies major histocompatibility complex class I chain-related protein in human and retinoic acid early induced transcript-1 in mouse, which acts as tumor-associated antigens. Biologic agents based on interleukin 21 (IL-21) have displayed antitumor activities through lymphocyte activation. The NKG2D–IL-21 fusion protein theoretically identifies tumor cells through NKG2D moiety and activates T cells through IL-21 moiety. In this study, double-gene fragments that encode the extracellular domains of NKG2D and IL-21 genes were connected and then inserted into the pcDNA3.1(−) plasmid. PcDNA3.1–dsNKG2D–IL-21 plasmid nanoparticles based on chitosan were generated. Tumor cells pretransfected with dsNKG2D–IL-21 gene nanoparticles can activate natural killer (NK) and CD8+ T cells in vitro. Serum IL-21 levels were enhanced in mice intramuscularly injected with the gene nanoparticles. DsNKG2D–IL-21 gene nanoparticles accumulated in tumor tissues after being intravenously injected for ~4–24 h. Treatment of dsNKG2D–IL-21 gene nanoparticles also retarded tumor growth and elongated the life span of tumor-bearing mice by activating NK and T cells in vivo. Thus, the dsNKG2D–IL-21 gene nanoparticles exerted efficient antitumor activities and would be potentially used for tumor therapy. PMID:28450784

  7. Theoretical and experimental study of DOA estimation using AML algorithm for an isotropic and non-isotropic 3D array

    NASA Astrophysics Data System (ADS)

    Asgari, Shadnaz; Ali, Andreas M.; Collier, Travis C.; Yao, Yuan; Hudson, Ralph E.; Yao, Kung; Taylor, Charles E.

    2007-09-01

    The focus of most direction-of-arrival (DOA) estimation problems has been based mainly on a two-dimensional (2D) scenario where we only need to estimate the azimuth angle. But in various practical situations we have to deal with a three-dimensional scenario. The importance of being able to estimate both azimuth and elevation angles with high accuracy and low complexity is of interest. We present the theoretical and the practical issues of DOA estimation using the Approximate-Maximum-Likelihood (AML) algorithm in a 3D scenario. We show that the performance of the proposed 3D AML algorithm converges to the Cramer-Rao Bound. We use the concept of an isotropic array to reduce the complexity of the proposed algorithm by advocating a decoupled 3D version. We also explore a modified version of the decoupled 3D AML algorithm which can be used for DOA estimation with non-isotropic arrays. Various numerical results are presented. We use two acoustic arrays each consisting of 8 microphones to do some field measurements. The processing of the measured data from the acoustic arrays for different azimuth and elevation angles confirms the effectiveness of the proposed methods.

  8. A 5 MHz Cylindrical Dual-Layer Transducer Array for 3-D Transrectal Ultrasound Imaging

    PubMed Central

    Chen, Yuling; Nguyen, Man; Yen, Jesse T.

    2012-01-01

    2-D transrectal ultrasound (TRUS) is being used in guiding prostate biopsies and treatments. In many cases, the TRUS probes are moved manually or mechanically to acquire volumetric information, making the imaging slow, user-dependent and unreliable. A real-time 3-D TRUS system could improve reliability and volume rates of imaging during these procedures. In this paper, we present a 5 MHz cylindrical dual-layer transducer array capable of real-time 3-D transrectal ultrasound without any mechanically moving parts. Compared to fully-sampled 2-D arrays, this design substantially reduces the channel count and fabrication complexity. This dual-layer transducer uses PZT elements for transmit and P[VDF-TrFE] copolymer elements for receive, respectively. The mechanical flexibility of both diced PZT and copolymer makes it practical for transrectal applications. Full synthetic aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics Data Acquisition System (VDAS). Offline 3-D beamforming was then performed to obtain volumes of two wire phantoms and a cyst phantom. Generalized coherence factor (GCF) was applied to improve the contrast of images. The measured −6 dB fractional bandwidth of the transducer was 62% with a center frequency of 5.66 MHz. The measured lateral beamwidths were 1.28 mm and 0.91 mm in transverse and longitudinal directions respectively, compared with a simulated beamwidth of 0.92 mm and 0.74 mm. PMID:22972914

  9. Compression of self-assembled nano-objects: 2D/3D transitions in films of (perfluoroalkyl)alkanes--persistence of an organized array of surface micelles.

    PubMed

    de Gracia Lux, Caroline; Gallani, Jean-Louis; Waton, Gilles; Krafft, Marie Pierre

    2010-06-25

    Understanding and controlling the molecular organization of amphiphilic molecules at interfaces is essential for materials and biological sciences. When spread on water, the model amphiphiles constituted by C(n)F(2n+1)C(m)H(2m+1) (FnHm) diblocks spontaneously self-assemble into surface hemimicelles. Therefore, compression of monolayers of FnHm diblocks is actually a compression of nanometric objects. Langmuir films of F8H16, F8H18, F8H20, and F10H16 can actually be compressed far beyond the "collapse" of their monolayers at approximately 30 A(2). For molecular areas A between 30 and 10 A(2), a partially reversible, 2D/3D transition occurs between a monolayer of surface micelles and a multilayer that coexist on a large plateau. For A<10 A(2), surface pressure increases again, reaching up to approximately 48 mN m(-1) before the film eventually collapses. Brewster angle microscopy and AFM indicate a several-fold increase in film thickness when scanning through the 2D/3D coexistence plateau. Compression beyond the plateau leads to a further increase in film thickness and, eventually, to film disruption. Reversibility was assessed by using compression-expansion cycles. AFM of F8H20 films shows that the initial monolayer of micelles is progressively covered by one (and eventually two) bilayers, which leads to a hitherto unknown organized composite arrangement. Compression of films of the more rigid F10H16 results in crystalline-like inflorescences. For both diblocks, a hexagonal array of surface micelles is consistently seen, even when the 3D structures eventually disrupt, which means that this monolayer persists throughout the compression experiments. Two examples of pressure-driven transformations of films of self-assembled objects are thus provided. These observations further illustrate the powerful self-assembling capacity of perfluoroalkyl chains.

  10. Design of crossed-mirror array to form floating 3D LED signs

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hirotsugu; Bando, Hiroki; Kujime, Ryousuke; Suyama, Shiro

    2012-03-01

    3D representation of digital signage improves its significance and rapid notification of important points. Our goal is to realize floating 3D LED signs. The problem is there is no sufficient device to form floating 3D images from LEDs. LED lamp size is around 1 cm including wiring and substrates. Such large pitch increases display size and sometimes spoils image quality. The purpose of this paper is to develop optical device to meet the three requirements and to demonstrate floating 3D arrays of LEDs. We analytically investigate image formation by a crossed mirror structure with aerial aperture, called CMA (crossed-mirror array). CMA contains dihedral corner reflectors at each aperture. After double reflection, light rays emitted from an LED will converge into the corresponding image point. We have fabricated CMA for 3D array of LEDs. One CMA unit contains 20 x 20 apertures that are located diagonally. Floating image of LEDs was formed in wide range of incident angle. The image size of focused beam agreed to the apparent aperture size. When LEDs were located three-dimensionally (LEDs in three depths), the focused distances were the same as the distance between the real LED and the CMA.

  11. Periodic arrays of M2-branes

    NASA Astrophysics Data System (ADS)

    Jeon, Imtak; Lambert, Neil; Richmond, Paul

    2012-11-01

    We consider periodic arrays of M2-branes in the ABJM model in the spirit of a circle compactification to D2-branes in type IIA string theory. The result is a curious formulation of three-dimensional maximally supersymmetric Yang-Mills theory in terms of fermions, seven transverse scalars, a non-dynamical gauge field and an additional scalar `dual gluon'. Upon further T-duality on a transverse torus we obtain a non-manifest- Lorentz-invariant description of five-dimensional maximally supersymmetric Yang-Mills. Here the additional scalar field can be thought of as the components of a two-form along the torus. This action can be viewed as an M-theory description of M5-branes on {{{T}}^3}.

  12. Ag colloids and arrays for plasmonic non-radiative energy transfer from quantum dots to a quantum well

    NASA Astrophysics Data System (ADS)

    Murphy, Graham P.; Gough, John J.; Higgins, Luke J.; Karanikolas, Vasilios D.; Wilson, Keith M.; Garcia Coindreau, Jorge A.; Zubialevich, Vitaly Z.; Parbrook, Peter J.; Bradley, A. Louise

    2017-03-01

    Non-radiative energy transfer (NRET) can be an efficient process of benefit to many applications including photovoltaics, sensors, light emitting diodes and photodetectors. Combining the remarkable optical properties of quantum dots (QDs) with the electrical properties of quantum wells (QWs) allows for the formation of hybrid devices which can utilize NRET as a means of transferring absorbed optical energy from the QDs to the QW. Here we report on plasmon-enhanced NRET from semiconductor nanocrystal QDs to a QW. Ag nanoparticles in the form of colloids and ordered arrays are used to demonstrate plasmon-mediated NRET from QDs to QWs with varying top barrier thicknesses. Plasmon-mediated energy transfer (ET) efficiencies of up to ˜25% are observed with the Ag colloids. The distance dependence of the plasmon-mediated ET is found to follow the same d -4 dependence as the direct QD to QW ET. There is also evidence for an increase in the characteristic distance of the interaction, thus indicating that it follows a Förster-like model with the Ag nanoparticle-QD acting as an enhanced donor dipole. Ordered Ag nanoparticle arrays display plasmon-mediated ET efficiencies up to ˜21%. To explore the tunability of the array system, two arrays with different geometries are presented. It is demonstrated that changing the geometry of the array allows a transition from overall quenching of the acceptor QW emission to enhancement, as well as control of the competition between the QD donor quenching and ET rates.

  13. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Students' Spatial Structuring of 2D Arrays of Squares.

    ERIC Educational Resources Information Center

    Battista, Michael T.; Clements, Douglas H.; Arnoff, Judy; Battista, Kathryn; Van Auken Borrow, Caroline

    1998-01-01

    Defines spatial structuring as the mental operation of constructing an organization or form for an object/set of objects. Examines in detail students' structuring and enumeration of two-dimensional rectangular arrays of squares. Concludes that many students do not see row-by-column structure. Describes various levels of sophistication in students'…

  15. Thermodynamic Properties of α-Fe 2O 3 and Fe 3O 4 Nanoparticles

    DOE PAGES

    Spencer, Elinor C.; Ross, Nancy L.; Olsen, Rebecca E.; ...

    2015-04-21

    Here we comprehansively assessed the thermodynamic properties of hydrated α-Fe 2O 3 (hematite) and Fe 3O 4 (magnetite) nanoparticles. In addition to 9 nm Fe 3O 4, three α-e 2O 3nanoparticles samples of different sizes (11, 14, and 25 nm) and bulk α-e 2O 3 have been evaluated by inelastic neutron scattering methods. The contribution of the two-level magnetic spin flip transition to the heat capacity of the α-e 2O 3 particles has been determined. The isochoric heat capacity of the water confined on the surface of these two types of iron oxide particles have been calculated from their INSmore » spectra, and is affected by the chemical composition of the underlying particle. Furthermore, the heat capacity and dynamics of the particle hydration layers appear to be influenced by a complex array of factors including particle size, water coverage, and possibly the magnetic state of the particle itself.« less

  16. Aberration improvement of the floating 3D display system based on Tessar array and directional diffuser screen

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Sang, Xinzhu; Yu, Xunbo; Zhang, Wanlu; Yan, Binbin; Yu, Chongxiu

    2018-06-01

    The floating 3D display system based on Tessar array and directional diffuser screen is proposed. The directional diffuser screen can smoothen the gap of lens array and make the 3D image's brightness continuous. The optical structure and aberration characteristics of the floating three-dimensional (3D) display system are analyzed. The simulation and experiment are carried out, which show that the 3D image quality becomes more and more deteriorative with the further distance of the image plane and the increasing viewing angle. To suppress the aberrations, the Tessar array is proposed according to the aberration characteristics of the floating 3D display system. A 3840 × 2160 liquid crystal display panel (LCD) with the size of 23.6 inches, a directional diffuser screen and a Tessar array are used to display the final 3D images. The aberrations are reduced and the definition is improved compared with that of the display with a single-lens array. The display depth of more than 20 cm and the viewing angle of more than 45° can be achieved.

  17. Shape matters: Cr(VI) removal using iron nanoparticle impregnated 1-D vs 2-D carbon nanohybrids prepared by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Masud, Arvid; Cui, Yanbin; Atkinson, John D.; Aich, Nirupam

    2018-03-01

    Iron nanoparticles (Fe NPs) are used for treating water contaminated with metals or organic compounds. One-dimensional (1-D) carbon nanotubes (CNTs) and two-dimensional (2-D) graphenes act as useful nanocarbon (NC) supports for Fe NPs by resisting aggregation and enhancing adsorption and redox activity. However, no study showed how shape difference between tubular CNT and planar graphene structures dictates the physicochemical properties and pollutant removal potential of their iron-based nanohybrids. In this work, ultrasonic spray pyrolysis was used to continuously prepare Fe-CNT and Fe-rGO nanohybrids. Both NC shape and Fe/NC ratio influenced Fe NP size, loading, and oxidation states. High Fe content (precursor Fe/NC mass ratio = 2) resulted Fe NPs with diameters of 30.97 ± 7.00 and 24.11 ± 4.42 nm for Fe-CNT and Fe-rGO, respectively; however, low Fe content (Fe/NC = 0.2) provided more uniformly dispersed Fe NPs of 15.65 ± 3.06 and 9.67 ± 1.49 nm, respectively, while unsupported Fe NPs were 285.71 ± 132.42 nm. The USP-derived nanohybrids, for the first time, were used for removal of pollutant, i.e., chromium (Cr(VI)) from aqueous media. Both CNT and rGO provided synergistic effects to significantly enhance Fe NPs' ability to remove Cr(VI); the effect was more pronounced in Fe-rGO than Fe-CNT and also for low Fe content in both cases. Fe-rGO with low Fe/NC ratio and smallest Fe NPs provided the highest Cr(VI) removal capacity (25 mg/g), which was a multifold improvement over bare Fe NPs and other synthesized nanohybrids (range 7-14 mg/g). Overall, 2-D rGO improved contaminant removal capacity of the nanohybrids more than 1-D CNT indicating towards shape effect of NC supports. [Figure not available: see fulltext.

  18. Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles.

    PubMed

    Baniasad, Arezou; Ghorbani, Mohsen

    2016-05-01

    In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35Å. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring

    NASA Astrophysics Data System (ADS)

    Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Leandro, Luana Di; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

    2016-03-01

    Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and ``green'' routes to 3D reduced GO-metal composite materials.Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its

  20. In Situ Gold Nanoparticle Gradient Formation in a 3D Meso- and Macroporous Polymer Matrix.

    PubMed

    Penders, Jelle; Rajasekharan, Anand K; Hulander, Mats; Andersson, Martin

    2017-08-01

    Herein, the development and characterization of a 3D gradient structure of gold nanoparticles is described. The gradient of gold nanoparticles is made in situ in a macroporous nonionic block copolymer hydrogel matrix, through gold ion diffusion control. The polymer provides a matrix for diffusion of gold ions, acts as a template for controlling nanoparticle growth, and facilitates the in situ reduction of gold ions to gold nanoparticles. A clear gradient in gold nanoparticles is observed across the 3D space of the polymer matrix using scanning electron microscopy, fluorescence microscopy, atomic force microscopy, and thermogravimetric analysis. The particle gradient is further functionalized with both hydrophobic and hydrophilic groups via thiol-gold linkage to demonstrate the ability to form gradients with different chemical functionalities. Using additive manufacturing, the polymer can also be printed as a porous network with possible applications for 3D cell culturing in, e.g., biomaterials research. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Controllable 3D architectures of aligned carbon nanotube arrays by multi-step processes

    NASA Astrophysics Data System (ADS)

    Huang, Shaoming

    2003-06-01

    An effective way to fabricate large area three-dimensional (3D) aligned CNTs pattern based on pyrolysis of iron(II) phthalocyanine (FePc) by two-step processes is reported. The controllable generation of different lengths and selective growth of the aligned CNT arrays on metal-patterned (e.g., Ag and Au) substrate are the bases for generating such 3D aligned CNTs architectures. By controlling experimental conditions 3D aligned CNT arrays with different lengths/densities and morphologies/structures as well as multi-layered architectures can be fabricated in large scale by multi-step pyrolysis of FePc. These 3D architectures could have interesting properties and be applied for developing novel nanotube-based devices.

  2. SU-F-T-571: Objective Assessment of 3D Dosimetry for Flattened and Flattened Filter Free Stereotactic Rotational Delivery Using 729-Array Detector with Octavius 4D Phantom

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vikraman, S; Arun, C; Jain, K Sandeep

    2016-06-15

    Purpose: The purpose of this study was to assess the potential of 3D dosimetry for flattened and flattened filter free stereotactic rotational delivery in high definition MLC using 729-detector array with Octavius 4D phantom Methods: Twenty rapid arc plans were assessed for this study. For each patient two plans for 6X and 6FFF photon beams were generated with same prescription and critical organ constraints in Eclipse TPS version 13.0 using high definition MLC. Verification plans were generated in scanned Octavius 4D phantom in TPS. 3D dose measurements were collected from 729-ion chamber detector array in Octavius 4D phantom using verisoftmore » software v 6.0. TPS calculated dose was compared with measured 3D dose in verisoft using the following gamma analysis parameters such as 3D volumetric, 3D planar and 2D global gamma in transverse, sagittal and coronal planes for 3mm/3% and 2mm/2% distance to agreement criteria.Passing rate and arithmetic mean of global gamma were analysed for 2D and 3D global gamma in all planes. Results: The average number of dose points passing rate for 2D global gamma with 3mm/3% criteria in transverse, sagittal and coronal planes was 99.06%±2.89%, 98.8%±0.88% and 99.06%±91%, respectively. For 2mm/2% criteria 97.86%±2.26%, 94.49± 2.64% and 94.34%±2.9% was observed. In 3D planar global gamma with 3mm/3% was 99.53%±0.49%, 98.93%±1.03% and 99.29%±1.29%, for 2mm 2% criteria was 97.50%±2.24%, 94.5%±2.5% and 95.38%±4.5%. The maximum arithmetic mean gamma deviation of 0.505%±0.13% was observed in coronal plane for 2D global gamma with 2mm/2% criteria. The 3D volumetric gamma passing rate was observed as 99.61%±0.433% for 3mm /3% and 95.91%±2.51% for 2mm/2%. Conclusion: The objective assessment of 3D dosimetry have demonstrated that the rotational delivery accuracy for flattened and flattened filter free stereotactic plans can be verified by using Octavius system comprising with 729 ion chamber array and Octavius 4D phantom.« less

  3. Two-dimensional photonic crystal arrays for polymer:fullerene solar cells.

    PubMed

    Nam, Sungho; Han, Jiyoung; Do, Young Rag; Kim, Hwajeong; Yim, Sanggyu; Kim, Youngkyoo

    2011-11-18

    We report the application of two-dimensional (2D) photonic crystal (PC) array substrates for polymer:fullerene solar cells of which the active layer is made with blended films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The 2D PC array substrates were fabricated by employing a nanosphere lithography technique. Two different hole depths (200 and 300 nm) were introduced for the 2D PC arrays to examine the hole depth effect on the light harvesting (trapping). The optical effect by the 2D PC arrays was investigated by the measurement of optical transmittance either in the direction normal to the substrate (direct transmittance) or in all directions (integrated transmittance). The results showed that the integrated transmittance was higher for the 2D PC array substrates than the conventional planar substrate at the wavelengths of ca. 400 nm, even though the direct transmittance of 2D PC array substrates was much lower over the entire visible light range. The short circuit current density (J(SC)) was higher for the device with the 2D PC array (200 nm hole depth) than the reference device. However, the device with the 2D PC array (300 nm hole depth) showed a slightly lower J(SC) value at a high light intensity in spite of its light harvesting effect proven at a lower light intensity.

  4. Organic vapor discrimination with chemiresistor arrays of temperature modulated tin-oxide nanowires and thiolate-monolayer-protected gold nanoparticles.

    PubMed

    Scholten, K; Bohrer, F I; Dattoli, E; Lu, W; Zellers, E T

    2011-03-25

    This paper explores the discrimination of organic vapors with arrays of chemiresistors (CRs) employing interface layers of tin-oxide nanowires (NWs) and thiolate-monolayer-protected gold nanoparticles (MPNs). The former devices use contact-printed mats of NWs on micro-hotplate membranes to bridge a pair of metal electrodes. Oxidation at the NW surface causes changes in charge transport, the temperature dependence of which differs among different vapors, permitting vapor discrimination. The latter devices use solvent cast films of MPNs on interdigital electrodes operated at room temperature. Sorption into the organic monolayers causes changes in film tunneling resistance that differ among different vapors and MPN structures, permitting vapor discrimination. Here, we compare the performance and assess the 'complementarity' of these two types of sensors. Calibrated responses from an NW CR operated at two different temperatures and from a set of four different MPN CRs were generated for three test vapors: n-hexane, toluene, and nitromethane. This pooled data set was then analyzed using principal components regression classification models with varying degrees of random error superimposed on the responses via Monte Carlo simulation in order to estimate the rates of recognition/discrimination for arrays comprising different combinations of sensors. Results indicate that the diversity of most of the dual MPN-CR arrays exceeds that of the dual NW-CR array. Additionally, in assessing all possible arrays of 4-6 CR sensors, the recognition rates of the hybrid arrays (i.e. MPN + NW) were no better than that of the 4-sensor array containing only MPN CRs.

  5. Toward Eco-Friendly and Highly Efficient Solar Water Splitting Using In2S3/Anatase/Rutile TiO2 Dual-Staggered-Heterojunction Nanodendrite Array Photoanode.

    PubMed

    Yang, Jih-Sheng; Wu, Jih-Jen

    2018-01-31

    The TiO 2 -based heterojunction nanodendrite (ND) array composed of anatase nanoparticles (ANPs) on the surface of the rutile ND (RND) array is selected as the model photoanode to demonstrate the strategies toward eco-friendly and efficient solar water splitting using neutral electrolyte and seawater. Compared with the performances in alkaline electrolyte, a non-negligible potential drop across the electrolyte as well as impeded charge injection and charge separation is monitored in the ANP/RND array photoanode with neutral electrolyte, which are, respectively, ascribed to the series resistance of neutral electrolyte, the fundamentally pH-dependent water oxidation mechanism on TiO 2 surface, as well as the less band bending at the interface of TiO 2 and neutral electrolyte. Accordingly, a TiO 2 -based dual-staggered heterojunction ND array photoanode is further designed in this work to overcome the issue of less band bending with the neutral electrolyte. The improvement of charge separation efficiency is realized by the deposition of a transparent In 2 S 3 layer on the ANP/RND array photoanode for constructing additional staggered heterojunction. Under illumination of AM 1.5G (100 mW cm -2 ), the improved photocurrent densities acquired both in neutral electrolyte and seawater at 1.23 V vs reversible hydrogen electrode (RHE), which approach the theoretical value for rutile TiO 2 , are demonstrated in the dual-staggered-heterojunction ND array photoanode. Faradaic efficiencies of ∼95 and ∼32% for solar water oxidation in neutral electrolyte and solar seawater oxidation for 2 h are acquired at 1.23 V vs RHE, respectively.

  6. Study on antibacterial alginate-stabilized copper nanoparticles by FT-IR and 2D-IR correlation spectroscopy

    PubMed Central

    Díaz-Visurraga, Judith; Daza, Carla; Pozo, Claudio; Becerra, Abraham; von Plessing, Carlos; García, Apolinaria

    2012-01-01

    Background The objective of this study was to clarify the intermolecular interaction between antibacterial copper nanoparticles (Cu NPs) and sodium alginate (NaAlg) by Fourier transform infrared spectroscopy (FT-IR) and to process the spectra applying two-dimensional infrared (2D-IR) correlation analysis. To our knowledge, the addition of NaAlg as a stabilizer of copper nanoparticles has not been previously reported. It is expected that the obtained results will provide valuable additional information on: (1) the influence of reducing agent ratio on the formation of copper nanoparticles in order to design functional nanomaterials with increased antibacterial activity, and (2) structural changes related to the incorporation of Cu NPs into the polymer matrix. Methods Cu NPs were prepared by microwave heating using ascorbic acid as reducing agent and NaAlg as stabilizing agent. The characterization of synthesized Cu NPs by ultraviolet visible spectroscopy, transmission electron microscopy (TEM), electron diffraction analysis, X-ray diffraction (XRD), and semiquantitative analysis of the weight percentage composition indicated that the average particle sizes of Cu NPs are about 3–10 nm, they are spherical in shape, and consist of zerovalent Cu and Cu2O. Also, crystallite size and relative particle size of stabilized Cu NPs were calculated by XRD using Scherrer’s formula and FT from the X-ray diffraction data. Thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry (DSC), FT-IR, second-derivative spectra, and 2D-IR correlation analysis were applied to studying the stabilization mechanism of Cu NPs by NaAlg molecules. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of stabilized Cu NPs against five bacterial strains (Staphylococccus aureus ATCC 6538P, Escherichia coli ATCC 25922 and O157: H7, and Salmonella enterica serovar Typhimurium ATCC 13311 and 14028) were evaluated with macrodilution

  7. Multifunctional hydroxyapatite and poly(D,L-lactide-co-glycolide) nanoparticles for the local delivery of cholecalciferol.

    PubMed

    Ignjatović, Nenad; Uskoković, Vuk; Ajduković, Zorica; Uskoković, Dragan

    2013-03-01

    Cholecalciferol, vitamin D3, plays an important role in bonemetabolism by regulating extracellular levels of calcium. Presented here is a study on the effects of the local delivery of cholecalciferol (D3) using nanoparticulate carriers composed of hydroxyapatite (HAp) and poly(D,L-lactide-co-glycolide) (PLGA). Multifunctional nanoparticulate HAp-based powders were prepared for the purpose of: (a) either fast or sustained, local delivery of cholecalciferol, and (b) the secondary, osteoconductive and defect-filling effect of the carrier itself. Two types of HAp-based powders with particles of narrowly dispersed sizes in the nano range were prepared and tested in this study: HAp nanoparticles as direct cholecalciferol delivery agents and HAp nanoparticles coated with cholecalciferol-loaded poly(D,L)-lactide-co-glycolide (HAp/D3/PLGA). Satisfying biocompatibility of particulate systems, when incubated in contact with MC3T3-E1 osteoblastic cells in vitro, was observed for HAp/D3/PLGA and pure HAp. In contrast, an extensively fast release of cholecalciferol from the system comprising HAp nanoparticles coated with cholecalciferol (HAp/D3) triggered necrosis of the osteoblastic cells in vitro. Artificial defects induced in the osteoporotic bone of the rat mandible were successfully reconstructed following implantation of cholecalciferol-coated HAp nanoparticles as well as those comprising HAp nanoparticles coated with cholecalciferol-loaded PLGA (HAp/D3/PLGA). The greatest levels of enhanced angiogenesis, vascularization, osteogenesis and bone structure differentiation were achieved upon the implementation of HAp/D3/PLGA systems.

  8. Dye-sensitized solar cells employing doubly or singly open-ended TiO2 nanotube arrays: structural geometry and charge transport.

    PubMed

    Choi, Jongmin; Song, Seulki; Kang, Gyeongho; Park, Taiho

    2014-09-10

    We systematically investigated the charge transport properties of doubly or singly open-ended TiO2 nanotube arrays (DNT and SNT, respectively) for their utility as electrodes in dye-sensitized solar cells (DSCs). The SNT or DNT arrays were transferred in a bottom-up (B-up) or top-up (T-up) configuration onto a fluorine-doped tin oxide (FTO) substrate onto which had been deposited a 2 μm thick TiO2 nanoparticle (NP) interlayer. This process yielded four types of DSCs prepared with SNTs (B-up or T-up) or DNT (B-up or T-up). The photovoltaic performances of these DSCs were analyzed by measuring the dependence of the charge transport on the DSC geometry. High resolution scanning electron microscopy techniques were used to characterize the electrode cross sections, and electrochemical impedance spectroscopy was used to characterize the electrical connection at the interface between the NT array and the TiO2 NP interlayer. We examined the effects of decorating the DNT or SNT arrays with small NPs (sNP@DNT and sNP@SNT, respectively) in an effort to increase the extent of dye loading. The DNT arrays decorated with small NPs performed better than the decorated SNT arrays, most likely because the Ti(OH)4 precursor solution flowed freely into the array through the open ends of the NTs in the DNT case but not in the SNT case. The sNP@DNT-based DSC exhibited a better PCE (10%) compared to the sNP@SNT-based DSCs (6.8%) because the electrolyte solution flow was not restricted, direct electron transport though the NT arrays was possible, the electrical connection at the interface between the NT array and the TiO2 NP interlayer was good, and the array provided efficient light harvesting.

  9. Localization and separation of acoustic sources by using a 2.5-dimensional circular microphone array.

    PubMed

    Bai, Mingsian R; Lai, Chang-Sheng; Wu, Po-Chen

    2017-07-01

    Circular microphone arrays (CMAs) are sufficient in many immersive audio applications because azimuthal angles of sources are considered more important than the elevation angles in those occasions. However, the fact that CMAs do not resolve the elevation angle well can be a limitation for some applications which involves three-dimensional sound images. This paper proposes a 2.5-dimensional (2.5-D) CMA comprised of a CMA and a vertical logarithmic-spacing linear array (LLA) on the top. In the localization stage, two delay-and-sum beamformers are applied to the CMA and the LLA, respectively. The direction of arrival (DOA) is estimated from the product of two array output signals. In the separation stage, Tikhonov regularization and convex optimization are employed to extract the source amplitudes on the basis of the estimated DOA. The extracted signals from two arrays are further processed by the normalized least-mean-square algorithm with the internal iteration to yield the source signal with improved quality. To validate the 2.5-D CMA experimentally, a three-dimensionally printed circular array comprised of a 24-element CMA and an eight-element LLA is constructed. Objective perceptual evaluation of speech quality test and a subjective listening test are also undertaken.

  10. Synthesis of three-dimensional AgI@TiO2 nanoparticles with improved photocatalytic performance.

    PubMed

    An, Changhua; Jiang, Wen; Wang, Jizhuang; Wang, Shutao; Ma, Zhanhua; Li, Yanpeng

    2013-06-28

    Three-dimensional (3D) TiO2 with an acanthosphere-like morphology composed of nanothorns has been used as a suitable support to fabricate a visible-light-induced 3D AgI@TiO2 nanophotocatalyst. The structural characterization revealed that the size of the obtained AgI@TiO2 nanocomposite was close to that of pristine TiO2 particles, where AgI nanoparticles were evenly dispersed on the surfaces of "thorns" of TiO2. The as-achieved 3D AgI@TiO2 nanophotocatalyst exhibited enhanced photocatalytic performance towards photodegradation of organic pollutants, e.g., rhodamine B (RhB), in comparison with TiO2, P25, AgI and AgI@P25 with the same quantity. The enhanced photocatalytic performance is attributed to the strong visible light absorption and the defined interfaces between AgI nanoparticles and TiO2 nanothorns with efficient separation of photogenerated carriers. The excellent performance of the 3D AgI@TiO2 nanophotocatalyst suggests its promising applications in water treatment and environmental remediation.

  11. SERS detection of R6G based on a novel graphene oxide/silver nanoparticles/silicon pyramid arrays structure.

    PubMed

    Zhang, C; Jiang, S Z; Huo, Y Y; Liu, A H; Xu, S C; Liu, X Y; Sun, Z C; Xu, Y Y; Li, Z; Man, B Y

    2015-09-21

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/silicon pyramid arrays structure (GO/Ag/PSi). The SERS behaviors are discussed and compared by the detection of R6G. Based on the contrast experiments with PSi, GO/PSi, Ag/PSi and GO/AgA/PSi as SERS substrate, the perfect bio-compatibility, good homogeneity and chemical stability were confirmed. We also calculated the electric field distributions using Finite-difference time-domain (FDTD) analysis to further understand the GO/Ag/PSi structure as a perfect SERS platform. These experimental and theoretical results imply that the GO/Ag/PSi with regular pyramids array is expected to be an effective substrate for label-free sensitive SERS detections in areas of medicine, food safety and biotechnology.

  12. 1D-TlInSe2: Band Structure, Dielectric Function and Nanorods

    NASA Astrophysics Data System (ADS)

    Mamedov, Nazim; Wakita, Kazuki; Akita, Seiji; Nakayama, Yoshikazu

    2005-01-01

    Linear combination of atomic orbitals (LCAO) analysis of the electronic band states has been completed for one-dimensional (1D) TlInSe2 having rod-like ground state shape of bulky crystal. The total scenario of the occurrence of the band states from the atomic states has been established. According to this scenario, in dipole approximation the optical transitions at band gap (point T of Brillouin zone) are either entirely forbidden or allowed for T2-T10 transitions in e\\perpc configuration provided that either initial or terminate state has T2 symmetry and both are Se-like. As a whole, the obtained results on the electronic spectrum, including dielectric function, are applicable to all obtained 1D-TlInSe2 nanorods which were as thin as 30--50 nm in cross-section, and apparently preserved tetragonal crystal structure of bulky material. The thermal instabilities developing already in bulky samples of 1D-TlInSe2 are considered to be an ultimate source of the nanoparticles emerging in plenty during nanorods preparation. The nanoplates of a chemically similar but 2D material, TlInS2, are demonstrated for comparison to show the absence of nanoparticles in that case. A possibility of nanoparticle preparation using laser excited coherent phonon trains in the nanorods of 1D-TlInSe2 is figured out.

  13. Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

    PubMed Central

    2013-01-01

    Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed. PMID:24004518

  14. Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles.

    PubMed

    Labunov, Vladimir; Prudnikava, Alena; Bushuk, Serguei; Filatov, Serguei; Shulitski, Boris; Tay, Beng Kang; Shaman, Yury; Basaev, Alexander

    2013-09-03

    Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.

  15. Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa2Cu3O7-d Containing Zn0.95Mn0.05O or Al2O3 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Al-Mohsin, R. A.; Al-Otaibi, A. L.; Almessiere, M. A.; Al-badairy, H.; Slimani, Y.; Ben Azzouz, F.

    2018-07-01

    Here we compare the microstructure and flux pinning properties of polycrystalline YBa2Cu3O7-d (Y-123 or YBCO) containing either Al2O3 or Zn0.95Mn0.05O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn0.95Mn0.05O resulted in a high density of fine twins and a variety of interacting microstructures, while Al2O3 addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

  16. Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa2Cu3O7-d Containing Zn0.95Mn0.05O or Al2O3 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Al-Mohsin, R. A.; Al-Otaibi, A. L.; Almessiere, M. A.; Al-badairy, H.; Slimani, Y.; Ben Azzouz, F.

    2018-03-01

    Here we compare the microstructure and flux pinning properties of polycrystalline YBa2Cu3O7-d (Y-123 or YBCO) containing either Al2O3 or Zn0.95Mn0.05O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn0.95Mn0.05O resulted in a high density of fine twins and a variety of interacting microstructures, while Al2O3 addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

  17. ActiveSeismoPick3D - automatic first arrival determination for large active seismic arrays

    NASA Astrophysics Data System (ADS)

    Paffrath, Marcel; Küperkoch, Ludger; Wehling-Benatelli, Sebastian; Friederich, Wolfgang

    2016-04-01

    We developed a tool for automatic determination of first arrivals in active seismic data based on an approach, that utilises higher order statistics (HOS) and the Akaike information criterion (AIC), commonly used in seismology, but not in active seismics. Automatic picking is highly desirable in active seismics as the number of data provided by large seismic arrays rapidly exceeds of what an analyst can evaluate in a reasonable amount of time. To bring the functionality of automatic phase picking into the context of active data, the software package ActiveSeismoPick3D was developed in Python. It uses a modified algorithm for the determination of first arrivals which searches for the HOS maximum in unfiltered data. Additionally, it offers tools for manual quality control and postprocessing, e.g. various visualisation and repicking functionalities. For flexibility, the tool also includes methods for the preparation of geometry information of large seismic arrays and improved interfaces to the Fast Marching Tomography Package (FMTOMO), which can be used for the prediction of travel times and inversion for subsurface properties. Output files are generated in the VTK format, allowing the 3D visualization of e.g. the inversion results. As a test case, a data set consisting of 9216 traces from 64 shots was gathered, recorded at 144 receivers deployed in a regular 2D array of a size of 100 x 100 m. ActiveSeismoPick3D automatically checks the determined first arrivals by a dynamic signal to noise ratio threshold. From the data a 3D model of the subsurface was generated using the export functionality of the package and FMTOMO.

  18. Buried Man-made Structure Imaging using 2-D Resistivity Inversion

    NASA Astrophysics Data System (ADS)

    Anderson Bery, Andy; Nordiana, M. M.; El Hidayah Ismail, Noer; Jinmin, M.; Nur Amalina, M. K. A.

    2018-04-01

    This study is carried out with the objective to determine the suitable resistivity inversion method for buried man-made structure (bunker). This study was carried out with two stages. The first stage is suitable array determination using 2-D computerized modeling method. One suitable array is used for the infield resistivity survey to determine the dimension and location of the target. The 2-D resistivity inversion results showed that robust inversion method is suitable to resolve the top and bottom part of the buried bunker as target. In addition, the dimension of the buried bunker is successfully determined with height of 7 m and length of 20 m. The location of this target is located at -10 m until 10 m of the infield resistivity survey line. The 2-D resistivity inversion results obtained in this study showed that the parameters selection is important in order to give the optimum results. These parameters are array type, survey geometry and inversion method used in data processing.

  19. Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mehrmohammadi, Mohammad; Kinnick, Randall R.; Fatemi, Mostafa, E-mail: fatemi.mostafa@mayo.edu

    2014-09-15

    Purpose: Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens. Methods: Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped withmore » a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection. Results: The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%–92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment. Conclusions: Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that

  20. Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

    PubMed Central

    Mehrmohammadi, Mohammad; Alizad, Azra; Kinnick, Randall R.; Davis, Brian J.; Fatemi, Mostafa

    2014-01-01

    Purpose: Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens. Methods: Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped with a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection. Results: The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%–92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment. Conclusions: Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that

  1. Electrochemistry of Canis familiaris cytochrome P450 2D15 with gold nanoparticles: An alternative to animal testing in drug discovery.

    PubMed

    Rua, Francesco; Sadeghi, Sheila J; Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco

    2015-10-01

    This work reports for the first time the direct electron transfer of the Canis familiaris cytochrome P450 2D15 on glassy carbon electrodes to provide an analytical tool as an alternative to P450 animal testing in the drug discovery process. Cytochrome P450 2D15, that corresponds to the human homologue P450 2D6, was recombinantly expressed in Escherichia coli and entrapped on glassy carbon electrodes (GC) either with the cationic polymer polydiallyldimethylammonium chloride (PDDA) or in the presence of gold nanoparticles (AuNPs). Reversible electrochemical signals of P450 2D15 were observed with calculated midpoint potentials (E1/2) of −191 ± 5 and −233 ± 4 mV vs. Ag/AgCl for GC/PDDA/2D15 and GC/AuNPs/2D15, respectively. These experiments were then followed by the electro-catalytic activity of the immobilized enzyme in the presence of metoprolol. The latter drug is a beta-blocker used for the treatment of hypertension and is a specific marker of the human P450 2D6 activity. Electrocatalysis data showed that only in the presence of AuNps the expected α-hydroxy-metoprolol product was present as shown by HPLC. The successful immobilization of the electroactive C. familiaris cytochrome P450 2D15 on electrode surfaces addresses the ever increasing demand of developing alternative in vitromethods for amore detailed study of animal P450 enzymes' metabolism, reducing the number of animals sacrificed in preclinical tests.

  2. Monitoring adsorption of gold nanoparticles on gold nanodisk array using dark-field hyperspectral microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zhao, Fusheng; Zenasni, Oussama; Li, Jingting; Shih, Wei-Chuan

    2017-02-01

    Localized surface plasmon resonance (LSPR) arises from the interaction of light with noble metal nanoparticles, which induces a collective oscillation in the free electrons. The size and shape of the metallic nanostructure significantly impact LSPR frequency and strength. Nanoplasmonic sensor has become a recent research focus due to its significant signal enhancement and robust signal transduction measured by extinction spectroscopy, fluorescence, Raman scattering, and absorption spectroscopy. Dark-field microscopy, in contrast, reports the scattered photons after light-matter interactions. In this case, the nanoparticles can be understood as dipole radiators whose free electrons oscillate in concert. Coupled with spectroscopy, this platform allows the collection of plasmonically scattered spectra from gold nanoparticles. Plasmonic coupling between electron-beam lithography patterned gold nanodisks (AuND) and colloidal gold nanoparticles (AuNP) can change the plasmonic resonance of the original entities, and can be effectively studied by dark-field hyperspectral microscopy. Typically, a pronounced redshift can be observed when plasmonic coupling occurs. When these nano-entities are functionalized with interactive surface moieties, biochemistry and molecular processes can be studied. In this paper, we will present the capability of assessing the process of immobilizing streptavidin-functionalized AuNPs on an array of biotin-terminated AuNDs. By monitoring changes in the LSPR band of AuNDs, we are able to evaluate similar processes in other molecular systems. In addition, plasmon coupling induced scattering intensity variations can be measured by an electron-multiplied charge-coupled device camera for rapid in situ monitoring. This method can potentially be useful in studying dynamic biophysical and biochemical processes in situ.

  3. Micromachining Techniques in Developing High-Frequency Piezoelectric Composite Ultrasonic Array Transducers

    PubMed Central

    Liu, Changgeng; Djuth, Frank T.; Zhou, Qifa; Shung, K. Kirk

    2014-01-01

    Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 μm in size with 5-μm kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm2 with a 16-μm kerf between elements. The active piezoelectric material is (1 − x) Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN-PT)/epoxy 1–3 composite with a PMN-PT pillar lateral dimension of 8 μm and an average gap width of ~4 μm, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse–echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the −6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about −33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

  4. Synthesis, Characterization and Comparative Luminescence Studies of Rare-Earth-Doped Gd2O3 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Pyngrope, D.; Singh, L. R.; Prasad, A. I.; Bora, A.

    2018-04-01

    A facile direct precipitation method was used for the synthesis of luminescence nanomaterial. Gd2O3 doped with rare earth element Eu3+ is synthesized by polyol route. The synthesized nanoparticles show their characteristic red emission. The nanoparticles are characterized by x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) study. The synthesized nanoparticles are spherical particles with 30 nm size. The photoluminescence studies show the characteristic Eu3+ red emission. The PL study shows the intensity of the magnetic dipole transition ( 5 D0 \\to 7 F1 ) at 592 nm compared to that of the electronic dipole transition ( 5 D0 \\to 7 F2 ) at 615 nm. The nanomaterials can show significant application in various display devices and biomedical applications for tracking.

  5. Efficient photocatalytic degradation of gaseous N,N-dimethylformamide in tannery waste gas using doubly open-ended Ag/TiO2 nanotube array membranes

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Ma, Lin; Chang, Wenkai; Huang, Zhiding; Feng, Xugen; Qi, Xiaoxia; Li, Zenghe

    2018-06-01

    Gaseous N,N-dimethylformamide (DMF), typical volatile organic compound exhausted from manufacturing factories, may damage the health of workers under long-term exposure even at low levels. The defined geometry, porous surface and highly ordered channels make the free-standing anodic TiO2 nanotube (TiNT) arrays particularly suitable for applications of practical air purification by flow-through photocatalysis. In the present work, crystallized doubly open-ended Ag/TiNT array membranes were designed and prepared by employing a lift-off process based on an anodization-annealing-anodization-etching sequence, followed by uniform Ag nanoparticles decoration. For the photocatalytic degradation of gaseous DMF at low concentration levels close to that found in realistic pollutant air, an analytical methodology for the monitoring and determination of degradation process was developed based on the coupling of headspace sampling with gas chromatography mass spectrometry (HS-GC-MS). The doubly open-ended Ag/TiNT arrays exhibited higher removal efficiency of gaseous DMF from air compared with conventional bottom-closed Ag/TiNT arrays and pure bottomless TiNT arrays. These results indicated that the photocatalytic properties of TiNT arrays were improved with the open-bottom morphology and the Ag nanoparticles decoration. Based on the analysis with GC-MS and high performance ion chromatography (HPIC), it was found that demethylation is the main pathway of DMF degradation in photocatalytic reactions. Furthermore, decontamination of actual polluted tannery waste gas collected in leather factory proved that the photocatalysis on doubly open-ended Ag/TiNT array membrane is an efficient way and a promising application to treat air contaminated by DMF despite the complexity of various volatile organic compounds.

  6. A dual-mode hemispherical sparse array for 3D passive acoustic mapping and skull localization within a clinical MRI guided focused ultrasound device

    NASA Astrophysics Data System (ADS)

    Crake, Calum; Brinker, Spencer T.; Coviello, Christian M.; Livingstone, Margaret S.; McDannold, Nathan J.

    2018-03-01

    Previous work has demonstrated that passive acoustic imaging may be used alongside MRI for monitoring of focused ultrasound therapy. However, past implementations have generally made use of either linear arrays originally designed for diagnostic imaging or custom narrowband arrays specific to in-house therapeutic transducer designs, neither of which is fully compatible with clinical MR-guided focused ultrasound (MRgFUS) devices. Here we have designed an array which is suitable for use within an FDA-approved MR-guided transcranial focused ultrasound device, within the bore of a 3 Tesla clinical MRI scanner. The array is constructed from 5  ×  0.4 mm piezoceramic disc elements arranged in pseudorandom fashion on a low-profile laser-cut acrylic frame designed to fit between the therapeutic elements of a 230 kHz InSightec ExAblate 4000 transducer. By exploiting thickness and radial resonance modes of the piezo discs the array is capable of both B-mode imaging at 5 MHz for skull localization, as well as passive reception at the second harmonic of the therapy array for detection of cavitation and 3D passive acoustic imaging. In active mode, the array was able to perform B-mode imaging of a human skull, showing the outer skull surface with good qualitative agreement with MR imaging. Extension to 3D showed the array was able to locate the skull within  ±2 mm/2° of reference points derived from MRI, which could potentially allow registration of a patient to the therapy system without the expense of real-time MRI. In passive mode, the array was able to resolve a point source in 3D within a  ±10 mm region about each axis from the focus, detect cavitation (SNR ~ 12 dB) at burst lengths from 10 cycles to continuous wave, and produce 3D acoustic maps in a flow phantom. Finally, the array was used to detect and map cavitation associated with microbubble activity in the brain in nonhuman primates.

  7. Printing 1D Assembly Array of Single Particle Resolution for Magnetosensing.

    PubMed

    Gao, Meng; Kuang, Minxuan; Li, Lihong; Liu, Meijin; Wang, Libin; Song, Yanlin

    2018-05-01

    Magnetosensing is a ubiquitous ability for many organism species in nature. 1D assembly, especially that arranged in single-particle-resolution regulation, is able to sense the direction of magnetic field depending on the enhanced dipolar interaction in the linear orientation. Inspired by the magnetosome structure in magnetotactic bacteria, a 1D assembly array of single particle resolution with controlled length and well-behaved configuration is prepared via inkjet printing method assisted with magnetic guiding. In the fabrication process, chains in a "tip-to-tip" regulation with the desired number of particles are prepared in a confined tiny inkjet-printed droplet. By adjusting the receding angle of the substrate, the assembled 1D morphology is kept/deteriorated depending on the pinning/depinning behavior during ink evaporation, which leads to the formation of well-behaved 1D assembly/aggregated dot assembly. Owing to the high-aspect-ratio characteristic of the assembled structure, the as-prepared 1D arrays can be used for magnetic field sensing with anisotropic magnetization M // /M ⊥ up to 6.03. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. High photocatalytic activity of mixed anatase-rutile phases on commercial TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ruu Siah, Wai; Lintang, Hendrik O.; Shamsuddin, Mustaffa; Yuliati, Leny

    2016-02-01

    Titanium dioxide (TiO2) is well-known as an active photocatalyst for degradation of various organic pollutants. Over the years, a wide range of TiO2 nanoparticles with different phase compositions, crystallinities, and surface areas have been developed. Due to the different methods and conditions used to synthesize these commercial TiO2 nanoparticles, the properties and photocatalytic performance would also be different from each other. In this study, the photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) was investigated on commercial Evonik P25, Evonik P90, Hombikat UV100 and Hombikat N100 TiO2 nanoparticles. Upon photocatalytic tests, it was found that overall, the photocatalytic activities of the P25 and the P90 were higher than the N100 and the UV100 for the removal of both 2,4-D and 2,4,5-T. The high activities of the P25 and the P90 could be attributed to their phase compositions, which are made up of a mixture of anatase and rutile phases of TiO2. Whereas, the UV100 and the N100 are made up of 100% anatase phase of TiO2. The synergistic effect of the anatase/rutile mixture was reported to slow down the recombination rate of photogenerated electron-hole pairs. Consequently, the photocatalytic activity was increased on these TiO2 nanoparticles.

  9. UV-enhanced CO sensing using Ga 2O 3-based nanorod arrays at elevated temperature

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

    Monitoring and control of gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such application due to the inherent high temperature of combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °Cmore » by an order of magnitude. Under the 254 nm UV illumination, CO gas-sensing performance of Ga 2O 3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125 %, and the response time reduced by 30 % for La 0.8Sr 0.2FeO 3(LSFO)-decorated sample. The UV-enhanced detecting of CO might be due to the increased population of photo-induced electron-hole pairs. While for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of sensitizing effect and photocurrent effect.« less

  10. UV-enhanced CO sensing using Ga 2O 3-based nanorod arrays at elevated temperature

    DOE PAGES

    Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

    2017-01-23

    Monitoring and control of gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such application due to the inherent high temperature of combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °Cmore » by an order of magnitude. Under the 254 nm UV illumination, CO gas-sensing performance of Ga 2O 3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125 %, and the response time reduced by 30 % for La 0.8Sr 0.2FeO 3(LSFO)-decorated sample. The UV-enhanced detecting of CO might be due to the increased population of photo-induced electron-hole pairs. While for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of sensitizing effect and photocurrent effect.« less

  11. UV-enhanced CO sensing using Ga2O3-based nanorod arrays at elevated temperature

    NASA Astrophysics Data System (ADS)

    Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

    2017-01-01

    Monitoring and control of the gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such applications due to the inherent high temperature of the combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found that surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °C by an order of magnitude. Under the 254 nm UV illumination, the CO gas-sensing performance of Ga2O3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125% and the response time reduced by 30% for the La0.8Sr0.2FeO3(LSFO)-decorated sample. The UV-enhanced detection of CO might be due to the increased population of photo-induced electron-hole pairs, whereas for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of the sensitizing effect and photocurrent effect.

  12. Regular Arrays of Germanium Nanoparticles Assisted by Thermoset Polymer Composites for High Capacity Lithium Ion Battery

    NASA Astrophysics Data System (ADS)

    Jo, Gyuha; Park, Moon Jeong

    2012-02-01

    In recent years Li-batteries have attracted significant interests for a variety of applications such as portable electronics and electric vehicle (EV) batteries due to their high energy densities. Key challenges in advancing the technology lie in specific energy density, the long term cycle properties, and durability at elevated temperature. In present study, we were motivated to prepare high capacity Li-battery by creating regular arrays of germanium nanoparticles (GeNPs, 1600 mAh/g) to replace commercial graphite anode (370 mAh/g). Thermoset polymers were employed to prepare GeNPs/polymer composites with tunable NP loadings and spacings, followed by carbonization process to prepare GeNPs/carbon composite anode material. Due to the large volume change of GeNPs with charge/discharge cycles, the regular arrays of GeNPs are turned out to be a crucial parameter in obtaining enhanced cyclability. The GeNPs/carbon anode materials were cycle tested in a half cell configuration using Lithium foil as a counter electrode and lithium salt doped PS-PEO block copolymers as electrolytes. High capacity and rate capability were achieved, which demonstrate the role of nano-sized and regularly-arrayed anode active materials in obtaining the improved battery performance.

  13. Multifunctional hydroxyapatite and poly(D,L-lactide-co-glycolide) nanoparticles for the local delivery of cholecalciferol

    PubMed Central

    Ignjatović, Nenad; Uskoković, Vuk; Ajduković, Zorica; Uskoković, Dragan

    2013-01-01

    Cholecalciferol, vitamin D3, plays an important role in bone metabolism by regulating extracellular levels of calcium. Presented here is a study on the effects of the local delivery of cholecalciferol (D3) using nanoparticulate carriers composed of hydroxyapatite (HAp) and poly(D,L-lactide-co-glycolide) (PLGA). Multifunctional nanoparticulate HAp-based powders were prepared for the purpose of: (a) either fast or sustained, local delivery of cholecalciferol, and (b) the secondary, osteoconductive and defect-filling effect of the carrier itself. Two types of HAp-based powders with particles of narrowly dispersed sizes in the nano range were prepared and tested in this study: HAp nanoparticles as direct cholecalciferol delivery agents and HAp nanoparticles coated with cholecalciferol-loaded poly(D,L)-lactide-co-glycolide (HAp/D3/PLGA). Satisfying biocompatibility of particulate systems, when incubated in contact with MC3T3-E1 osteoblastic cells in vitro, was observed for HAp/D3/PLGA and pure HAp. In contrast, an extensively fast release of cholecalciferol from the system comprising HAp nanoparticles coated with cholecalciferol (HAp/D3) triggered necrosis of the osteoblastic cells in vitro. Artificial defects induced in the osteoporotic bone of the rat mandible were successfully reconstructed following implantation of cholecalciferol-coated HAp nanoparticles as well as those comprising HAp nanoparticles coated with cholecalciferol-loaded PLGA (HAp/D3/PLGA). The greatest levels of enhanced angiogenesis, vascularization, osteogenesis and bone structure differentiation were achieved upon the implementation of HAp/D3/PLGA systems. PMID:25382938

  14. Topically Applied Curcumin-Loaded Nanoparticles Treat Erectile Dysfunction in a Rat Model of Type-2 Diabetes.

    PubMed

    Draganski, Andrew; Tar, Moses T; Villegas, Guillermo; Friedman, Joel M; Davies, Kelvin P

    2018-05-01

    Curcumin, a naturally occurring anti-inflammatory compound, has shown promise in pre-clinical studies to treat erectile dysfunction (ED) associated with type-1 diabetes. However, poor bioavailability following oral administration limits its efficacy. The present study evaluated the potential of topical application of curcumin-loaded nanoparticles (curc-np) to treat ED in a rat model of type-2 diabetes (T2D). Determine if topical application of curc-np treats ED in a T2D rat model and modulates expression of inflammatory markers. Curc-np (4 mg curcumin) or blank nanoparticles were applied every 2 days for 2 weeks to the shaved abdomen of 20-week-old Zucker diabetic fatty male rats (N = 5 per group). Lean Zucker diabetic fatty male rat controls were treated with blank nanoparticles (N = 5). Penetration of nanoparticles and curcumin release were confirmed by 2-photon fluorescence microscopy and histology. Erectile function was determined by measuring intracorporal pressure (ICP) normalized to systemic blood pressure (ICP/BP) following cavernous nerve stimulation. Corporal tissue was excised and reverse transcription and quantitative polymerase chain reaction used to determine expression of the following markers: nuclear factor (NF)-κβ, NF-κβ-activating protein (Nkap), NF erythroid 2-related factor-2, Kelch-like enoyl-CoA hydratase-associated protein-1, heme oxygenase-1 (HO-1), variable coding sequence-A1, phosphodiesterase-5, endothelial and neuronal nitric oxide synthase, Ras homolog gene family member A, and Rho-associated coiled-coil containing protein kinases-1 and -2. Erectile function by determination of ICP/BP and expression of molecular markers in corporal tissue by RT-qPCR. Nanoparticles penetrated the abdominal epidermis and persisted in hair follicles for 24 hours. Curc-np-treated animals exhibited higher average ICP/BP than animals treated with blank nanoparticles at all levels of stimulation and this was statistically significant (P < .05) at 0.75 m

  15. Improved Spatial Differencing Scheme for 2-D DOA Estimation of Coherent Signals with Uniform Rectangular Arrays.

    PubMed

    Shi, Junpeng; Hu, Guoping; Sun, Fenggang; Zong, Binfeng; Wang, Xin

    2017-08-24

    This paper proposes an improved spatial differencing (ISD) scheme for two-dimensional direction of arrival (2-D DOA) estimation of coherent signals with uniform rectangular arrays (URAs). We first divide the URA into a number of row rectangular subarrays. Then, by extracting all the data information of each subarray, we only perform difference-operation on the auto-correlations, while the cross-correlations are kept unchanged. Using the reconstructed submatrices, both the forward only ISD (FO-ISD) and forward backward ISD (FB-ISD) methods are developed under the proposed scheme. Compared with the existing spatial smoothing techniques, the proposed scheme can use more data information of the sample covariance matrix and also suppress the effect of additive noise more effectively. Simulation results show that both FO-ISD and FB-ISD can improve the estimation performance largely as compared to the others, in white or colored noise conditions.

  16. Improved Spatial Differencing Scheme for 2-D DOA Estimation of Coherent Signals with Uniform Rectangular Arrays

    PubMed Central

    Hu, Guoping; Zong, Binfeng; Wang, Xin

    2017-01-01

    This paper proposes an improved spatial differencing (ISD) scheme for two-dimensional direction of arrival (2-D DOA) estimation of coherent signals with uniform rectangular arrays (URAs). We first divide the URA into a number of row rectangular subarrays. Then, by extracting all the data information of each subarray, we only perform difference-operation on the auto-correlations, while the cross-correlations are kept unchanged. Using the reconstructed submatrices, both the forward only ISD (FO-ISD) and forward backward ISD (FB-ISD) methods are developed under the proposed scheme. Compared with the existing spatial smoothing techniques, the proposed scheme can use more data information of the sample covariance matrix and also suppress the effect of additive noise more effectively. Simulation results show that both FO-ISD and FB-ISD can improve the estimation performance largely as compared to the others, in white or colored noise conditions. PMID:28837115

  17. Synthesis and optical properties modulation of ZnO/Eu2O3 nanocable arrays

    NASA Astrophysics Data System (ADS)

    Yang, Lei; She, Yajuan; Zhao, Shihua; Yue, Shihai; Wang, Qian; Hu, Aiping; Zhang, Wei

    2010-11-01

    White-light-emitting materials have attracted considerable attention because of their applications, such as large-surface emitting devices and displays. However, simply mixing nanoparticles would result in uneven color. Nanocables are expected to improve the chemical stability and color uniformity. Herein we demonstrate the synthesis of Eu2O3/ZnO nanocable arrays embedded in anodic alumina template via a versatile, simple, and cheap method. In order to control the composition of the cable with low cost, a two-step synthesis including an electric field deposition and a sol-gel template approach is used to fabricate the nanocable. The product is investigated by x-ray powder diffraction, transmission electron microscopy, selected area electron diffraction, and photoluminescence (PL) spectrum. The results show that ordered Eu2O3/ZnO nanocable arrays with an average inside diameter of 20-40 nm and wall thickness of 20-40 nm were prepared. By adjusting the excitation wavelength, change of the emitting color of the cables from blue to white could be obtained. Energy and charge transfer were found by investigating the electronic transition and recombination in the PL process. These arrays are promising for applications in display, white phosphors, and ultraviolet detectors owing to the special optical properties. And this method may be of much significance in the synthesis of nanocables with the controllable composition.

  18. D, L-Sulforaphane Loaded Fe3O4@ Gold Core Shell Nanoparticles: A Potential Sulforaphane Delivery System.

    PubMed

    Kheiri Manjili, Hamidreza; Ma'mani, Leila; Tavaddod, Sharareh; Mashhadikhan, Maedeh; Shafiee, Abbas; Naderi-Manesh, Hossein

    2016-01-01

    A novel design of gold-coated iron oxide nanoparticles was fabricated as a potential delivery system to improve the efficiency and stability of d, l-sulforaphane as an anticancer drug. To this purpose, the surface of gold-coated iron oxide nanoparticles was modified for sulforaphane delivery via furnishing its surface with thiolated polyethylene glycol-folic acid and thiolated polyethylene glycol-FITC. The synthesized nanoparticles were characterized by different techniques such as FTIR, energy dispersive X-ray spectroscopy, UV-visible spectroscopy, scanning and transmission electron microscopy. The average diameters of the synthesized nanoparticles before and after sulforaphane loading were obtained ∼ 33 nm and ∼ 38 nm, respectively, when ∼ 2.8 mmol/g of sulforaphane was loaded. The result of cell viability assay which was confirmed by apoptosis assay on the human breast cancer cells (MCF-7 line) as a model of in vitro-cancerous cells, proved that the bare nanoparticles showed little inherent cytotoxicity, whereas the sulforaphane-loaded nanoparticles were cytotoxic. The expression rate of the anti-apoptotic genes (bcl-2 and bcl-xL), and the pro-apoptotic genes (bax and bak) were quantified, and it was found that the expression rate of bcl-2 and bcl-xL genes significantly were decreased when MCF-7 cells were incubated by sulforaphane-loaded nanoparticles. The sulforaphane-loaded into the designed gold-coated iron oxide nanoparticles, acceptably induced apoptosis in MCF-7 cells.

  19. Plasmonic gold nanoparticles modified titania nanotubes for antibacterial application

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Jinhua; Zhou, Huaijuan; Qian, Shi

    Close-packed TiO{sub 2} nanotube arrays are prepared on metallic Ti surface by electrochemical anodization. Subsequently, by magnetron sputtering, Au nanoparticles are coated onto the top sidewall and tube inwall. The Au@TiO{sub 2} systems can effectively kill Staphylococcus aureus and Escherichia coli in darkness due to the existence of Au nanoparticles. On the basis of classical optical theories, the antibacterial mechanism is proposed from the perspective of localized surface plasmon resonance. Respiratory electrons of bacterial membrane transfer to Au nanoparticles and then to TiO{sub 2}, which makes bacteria steadily lose electrons until death. This work provides insights for the better understandingmore » and designing of noble metal nanoparticles-based plasmonic heterostructures for antibacterial application.« less

  20. Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.

    PubMed

    Leung, Yu Hang; Yung, Mana M N; Ng, Alan M C; Ma, Angel P Y; Wong, Stella W Y; Chan, Charis M N; Ng, Yip Hang; Djurišić, Aleksandra B; Guo, Muyao; Wong, Mabel Ting; Leung, Frederick C C; Chan, Wai Kin; Leung, Kenneth M Y; Lee, Hung Kay

    2015-04-01

    Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Well-defined magnetic surface imprinted nanoparticles for selective enrichment of 2,4-dichlorophenoxyacetic acid in real samples.

    PubMed

    Sheng, Le; Jin, Yulong; He, Yonghuan; Huang, Yanyan; Yan, Liushui; Zhao, Rui

    2017-11-01

    Superparamagnetic core-shell molecularly imprinted polymer nanoparticles (MIPs) were prepared via surface initiated reversible-addition fragmentation chain transfer (si-RAFT) polymerization for the selective recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) in real samples. The construction of uniform core-shell structure with a 50nm MIP layer was successfully accomplished, which favored mass transfer and resulted in fast recognition kinetics. The static equilibrium experiments revealed the satisfied adsorption capacity and imprinting efficiency of Fe 3 O 4 @MIP. Moreover, the Fe 3 O 4 @MIP exhibited high selectivity and affinity towards 2,4-D over structural analogues. The prepared Fe 3 O 4 @MIP nanoparticles were used for the selective enrichment of 2,4-D in tap water and Chinese cabbage samples. Combined with RP-HPLC, the recoveries of 2,4-D were calculated from 93.1% to 103.3% with RSD of 1.7-5.4% (n = 3) in Chinese cabbage samples. This work provides a versatile approach for fabricating well-constructed core-shell MIP nanoparticles for rapid enrichment and highly selective separation of target molecules in real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Clinical introduction of a linac head-mounted 2D detector array based quality assurance system in head and neck IMRT.

    PubMed

    Korevaar, Erik W; Wauben, David J L; van der Hulst, Peter C; Langendijk, Johannes A; Van't Veld, Aart A

    2011-09-01

    IMRT QA is commonly performed in a phantom geometry but the clinical interpretation of the results in a 2D phantom plane is difficult. The main objective of our work is to move from film measurement based QA to 3D dose reconstruction in a patient CT scan. In principle, this could be achieved using a dose reconstruction method from 2D detector array measurements as available in the COMPASS system (IBA Dosimetry). The first step in the clinical introduction of this system instead of the currently used film QA procedures is to test the reliability of the dose reconstruction. In this paper we investigated the validation of the method in a homogeneous phantom with the film QA procedure as a reference. We tested whether COMPASS QA results correctly identified treatment plans that did or did not fulfil QA requirements in head and neck (H&N) IMRT. A total number of 24 treatments were selected from an existing database with more than 100 film based H&N IMRT QA results. The QA results were classified as either good, just acceptable or clinically rejected (mean gamma index <0.4, 0.4-0.5 or >0.5, respectively with 3%/3mm criteria). Film QA was repeated and compared to COMPASS QA with a MatriXX detector measurement performed on the same day. Good agreement was found between COMPASS reconstructed dose and film measured dose in a phantom (mean gamma 0.83±0.09, 1SD with 1%/1mm criteria, 0.33±0.04 with 3%/3mm criteria). COMPASS QA results correlated well with film QA, identifying the same patients with less good QA results. Repeated measurements with film and COMPASS showed changes in delivery after a modified MLC calibration, also visible in a standard MLC check in COMPASS. The time required for QA reduced by half by using COMPASS instead of film. Agreement of COMPASS QA results with film based QA supports its clinical introduction for a phantom geometry. A standard MLC calibration check is sensitive to <1mm changes that could be significant in H&N IMRT. These findings offer

  3. 3D Graphene Oxide-encapsulated Gold Nanoparticles to Detect Neural Stem Cell Differentiation

    PubMed Central

    Kim, Tae-Hyung; Lee, Ki-Bum; Choi, Jeong-Woo

    2013-01-01

    Monitoring of stem cell differentiation and pluripotency is an important step for the practical use of stem cells in the field of regenerative medicine. Hence, a new non-destructive detection tool capable of in situ monitoring of stem cell differentiation is highly needed. In this study, we report a 3D graphene oxide-encapsulated gold nanoparticle that is very effective for the detection of the differentiation potential of neural stem cells (NSCs) based on surface-enhanced Raman spectroscopy (SERS). A new material, 3D GO-encapsulated gold nanoparticle, is developed to induce the double enhancement effect of graphene oxide and gold nanoparticle on SERS signals which is only effective for undifferentiated NSCs. The Raman peaks achieved from undifferentiated NSCs on the graphene oxide (GO)-encapsulated gold nanoparticles were 3.5 times higher than peaks obtained from normal metal structures and were clearly distinguishable from those of differentiated cells. The number of C=C bonds and the raman instensity at 1656cm−1 was found to show a positive correlation, which matches the differentiation state of the NSCs. Moreover, the substrate composed of 3D GO-encapsulated gold nanoparticles was also effective at distinguishing the differentiation state of single NSC by using electrochemical and electrical techniques. Hence, the proposed technique can be used as a powerful non-destructive in situ monitoring tool for the identification of the differentiation potential of various kinds of stem cells (mesenchymal, hematopoietic, and neural stem cells). PMID:23937915

  4. Extraction of 3D Information from Circular Array Measurements for Auralization with Wave Field Synthesis

    NASA Astrophysics Data System (ADS)

    de Vries, Diemer; Hörchens, Lars; Grond, Peter

    2007-12-01

    The state of the art of wave field synthesis (WFS) systems is that they can reproduce sound sources and secondary (mirror image) sources with natural spaciousness in a horizontal plane, and thus perform satisfactory 2D auralization of an enclosed space, based on multitrace impulse response data measured or simulated along a 2D microphone array. However, waves propagating with a nonzero elevation angle are also reproduced in the horizontal plane, which is neither physically nor perceptually correct. In most listening environments to be auralized, the floor is highly absorptive since it is covered with upholstered seats, occupied during performances by a well-dressed audience. A first-order ceiling reflection, reaching the floor directly or via a wall, will be severely damped and will not play a significant role in the room response anymore. This means that a spatially correct WFS reproduction of first-order ceiling reflections, by means of a loudspeaker array at the ceiling of the auralization reproduction room, is necessary and probably sufficient to create the desired 3D spatial perception. To determine the driving signals for the loudspeakers in the ceiling array, it is necessary to identify the relevant ceiling reflection(s) in the multichannel impulse response data and separate those events from the data set. Two methods are examined to identify, separate, and reproduce the relevant reflections: application of the Radon transform, and decomposition of the data into cylindrical harmonics. Application to synthesized and measured data shows that both methods in principle are able to identify, separate, and reproduce the relevant events.

  5. ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells

    PubMed Central

    2014-01-01

    Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells. PMID:24618047

  6. Correlating hydrodynamic radii with that of two-dimensional nanoparticles

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yue, Yuan; Kan, Yuwei; Clearfield, Abraham

    2015-12-21

    Dynamic light scattering (DLS) is one of the most adapted methods to measure the size of nanoparticles, as referred to the hydrodynamic radii (R{sub h}). However, the R{sub h} represents only that of three-dimensional spherical nanoparticles. In the present research, the size of two-dimensional (2D) nanoparticles of yttrium oxide (Y{sub 2}O{sub 3}) and zirconium phosphate (ZrP) was evaluated through comparing their hydrodynamic diameters via DLS with lateral sizes obtained using scanning and transmission electron microscopy. We demonstrate that the hydrodynamic radii are correlated with the lateral sizes of both square and circle shaped 2D nanoparticles. Two proportional coefficients, i.e., correctingmore » factors, are proposed for the Brownian motion status of 2D nanoparticles. The correction is possible by simplifying the calculation of integrals in the case of small thickness approximation. The correcting factor has great significance for investigating the translational diffusion behavior of 2D nanoparticles in a liquid and in effective and low-cost measurement in terms of size and morphology of shape-specific nanoparticles.« less

  7. Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates.

    PubMed

    Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

    2015-11-21

    Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) "hot spots" created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10(-7) M and 10(-5) M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.

  8. Use of Fe3O4 Nanoparticles for Enhancement of Biosensor Response to the Herbicide 2,4-Dichlorophenoxyacetic Acid

    PubMed Central

    Loh, Kee-Shyuan; Lee, Yook Heng; Musa, Ahmad; Salmah, Abdul Aziz; Zamri, Ishak

    2008-01-01

    Magnetic nanoparticles of Fe3O4 were synthesized and characterized using transmission electron microscopy and X-ray diffraction. The Fe3O4 nanoparticles were found to have an average diameter of 5.48 ±1.37 nm. An electrochemical biosensor based on immobilized alkaline phosphatase (ALP) and Fe3O4 nanoparticles was studied. The amperometric biosensor was based on the reaction of ALP with the substrate ascorbic acid 2-phosphate (AA2P). The incorporation of the Fe3O4 nanoparticles together with ALP into a sol gel/chitosan biosensor membrane has led to the enhancement of the biosensor response, with an improved linear response range to the substrate AA2P (5-120 μM) and increased sensitivity. Using the inhibition property of the ALP, the biosensor was applied to the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The use of Fe3O4 nanoparticles gives a two-fold improvement in the sensitivity towards 2,4-D, with a linear response range of 0.5-30 μgL-1. Exposure of the biosensor to other toxicants such as heavy metals demonstrated only slight interference from metals such as Hg2+, Cu2+, Ag2+ and Pb2+. The biosensor was shown to be useful for the determination of the herbicide 2, 4-D because good recovery of 95-100 percent was obtained, even though the analysis was performed in water samples with a complex matrix. Furthermore, the results from the analysis of 2,4-D in water samples using the biosensor correlated well with a HPLC method. PMID:27873839

  9. 3D CNT macrostructure synthesis catalyzed by MgFe2O4 nanoparticles-A study of surface area and spinel inversion influence

    NASA Astrophysics Data System (ADS)

    Zampiva, Rúbia Young Sun; Kaufmann Junior, Claudir Gabriel; Pinto, Juliano Schorne; Panta, Priscila Chaves; Alves, Annelise Kopp; Bergmann, Carlos Pérez

    2017-11-01

    The MgFe2O4 spinel exhibits remarkable magnetic properties that open up numerous applications in biomedicine, the environment and catalysis. MgFe2O4 nanoparticles are excellent catalyst for carbon nanotube (CNT) production. In this work, we proposed to use MgFe2O4 nanopowder as a catalyst in the production of 3D macroscopic structures based on CNTs. The creation of these nanoengineered 3D architectures remains one of the most important challenges in nanotechnology. These systems have high potential as supercapacitors, catalytic electrodes, artificial muscles and in environmental applications. 3D macrostructures are formed due to an elevated density of CNTs. The quantity and quality of the CNTs are directly related to the catalyst properties. A heat treatment study was performed to produce the most effective catalyst. Factors such as superficial area, spinel inversion, crystallite size, degree of agglomeration and its correlation with van der Waals forces were examined. As result, the ideal catalyst properties for CNT production were determined and high-density 3D CNT macrostructures were produced successfully.

  10. Nano-array integrated monolithic devices: toward rational materials design and multi-functional performance by scalable nanostructures assembly

    DOE PAGES

    Wang, Sibo; Ren, Zheng; Guo, Yanbing; ...

    2016-03-21

    We report the scalable three-dimensional (3-D) integration of functional nanostructures into applicable platforms represents a promising technology to meet the ever-increasing demands of fabricating high performance devices featuring cost-effectiveness, structural sophistication and multi-functional enabling. Such an integration process generally involves a diverse array of nanostructural entities (nano-entities) consisting of dissimilar nanoscale building blocks such as nanoparticles, nanowires, and nanofilms made of metals, ceramics, or polymers. Various synthetic strategies and integration methods have enabled the successful assembly of both structurally and functionally tailored nano-arrays into a unique class of monolithic devices. The performance of nano-array based monolithic devices is dictated bymore » a few important factors such as materials substrate selection, nanostructure composition and nano-architecture geometry. Therefore, the rational material selection and nano-entity manipulation during the nano-array integration process, aiming to exploit the advantageous characteristics of nanostructures and their ensembles, are critical steps towards bridging the design of nanostructure integrated monolithic devices with various practical applications. In this article, we highlight the latest research progress of the two-dimensional (2-D) and 3-D metal and metal oxide based nanostructural integrations into prototype devices applicable with ultrahigh efficiency, good robustness and improved functionality. Lastly, selective examples of nano-array integration, scalable nanomanufacturing and representative monolithic devices such as catalytic converters, sensors and batteries will be utilized as the connecting dots to display a roadmap from hierarchical nanostructural assembly to practical nanotechnology implications ranging from energy, environmental, to chemical and biotechnology areas.« less

  11. Nano-array integrated monolithic devices: toward rational materials design and multi-functional performance by scalable nanostructures assembly

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Sibo; Ren, Zheng; Guo, Yanbing

    We report the scalable three-dimensional (3-D) integration of functional nanostructures into applicable platforms represents a promising technology to meet the ever-increasing demands of fabricating high performance devices featuring cost-effectiveness, structural sophistication and multi-functional enabling. Such an integration process generally involves a diverse array of nanostructural entities (nano-entities) consisting of dissimilar nanoscale building blocks such as nanoparticles, nanowires, and nanofilms made of metals, ceramics, or polymers. Various synthetic strategies and integration methods have enabled the successful assembly of both structurally and functionally tailored nano-arrays into a unique class of monolithic devices. The performance of nano-array based monolithic devices is dictated bymore » a few important factors such as materials substrate selection, nanostructure composition and nano-architecture geometry. Therefore, the rational material selection and nano-entity manipulation during the nano-array integration process, aiming to exploit the advantageous characteristics of nanostructures and their ensembles, are critical steps towards bridging the design of nanostructure integrated monolithic devices with various practical applications. In this article, we highlight the latest research progress of the two-dimensional (2-D) and 3-D metal and metal oxide based nanostructural integrations into prototype devices applicable with ultrahigh efficiency, good robustness and improved functionality. Lastly, selective examples of nano-array integration, scalable nanomanufacturing and representative monolithic devices such as catalytic converters, sensors and batteries will be utilized as the connecting dots to display a roadmap from hierarchical nanostructural assembly to practical nanotechnology implications ranging from energy, environmental, to chemical and biotechnology areas.« less

  12. Comparing highly ordered monolayers of nanoparticles fabricated using electrophoretic deposition: Cobalt ferrite nanoparticles versus iron oxide nanoparticles

    DOE PAGES

    Dickerson, James H.; Krejci, Alex J.; Garcia, Adriana -Mendoza; ...

    2015-08-01

    Ordered assemblies of nanoparticles remain challenging to fabricate, yet could open the door to many potential applications of nanomaterials. Here, we demonstrate that locally ordered arrays of nanoparticles, using electrophoretic deposition, can be extended to produce long-range order among the constituents. Voronoi tessellations along with multiple statistical analyses show dramatic increases in order compared with previously reported assemblies formed through electric field-assisted assembly. As a result, based on subsequent physical measurements of the nanoparticles and the deposition system, the underlying mechanisms that generate increased order are inferred.

  13. Increase in the energy density of the pinch plasma in 3D implosion of quasi-spherical wire arrays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aleksandrov, V. V., E-mail: alexvv@triniti.ru; Gasilov, V. A.; Grabovski, E. V.

    Results are presented from experimental studies of the characteristics of the soft X-ray (SXR) source formed in the implosion of quasi-spherical arrays made of tungsten wires and metalized kapron fibers. The experiments were carried out at the Angara-5-1 facility at currents of up to 3 MA. Analysis of the spatial distribution of hard X-ray emission with photon energies above 20 keV in the pinch images taken during the implosion of quasi-spherical tungsten wire arrays (QTWAs) showed that a compact quasi-spherical plasma object symmetric with respect to the array axis formed in the central region of the array. Using a diffractionmore » grazing incidence spectrograph, spectra of SXR emission with wavelengths of 20–400 Å from the central, axial, and peripheral regions of the emission source were measured with spatial resolutions along the array radius and height in the implosion of QTWAs. It is shown that the emission spectra of the SXR sources formed under the implosion of quasi-spherical and cylindrical tungsten wire arrays at currents of up to 3 MA have a maximum in the wavelength range of 50–150 Å. It is found that, during the implosion of a QTWA with a profiled linear mass, a redistribution of energy in the emission spectrum takes place, which indicates that, during 3D implosion, the energy of longitudinal motion of the array material additionally contributes to the radiation energy. It is also found that, at close masses of the arrays and close values of the current in the range of 2.4{sup −3} MA, the average energy density in the emission source formed during the implosion of a quasi-spherical wire array is larger by a factor of 7 than in the source formed during the implosion of a cylindrical wire array. The experimental data were compared with results of 3D simulations of plasma dynamics and radiation generation during the implosion of quasi-spherical wire arrays with a profiled mass by using the MARPLE-3D radiative magnetohydrodynamic code

  14. TiO2 nanoparticles alleviate toxicity by reducing free Zn2+ ion in human primary epidermal keratinocytes exposed to ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Kathawala, Mustafa Hussain; Ng, Kee Woei; Loo, Say Chye Joachim

    2015-06-01

    Nanoparticles have been a subject of intense safety screenings due to their influx in various applications. Although recent studies have reported on the plausible cytotoxicity of nanoparticles, many of these focused only on single-material nanoparticles, while the cytotoxicity of dual-nanoparticle systems (e.g., ZnO with TiO2) has remained unexplored. For example, commercial products like sunscreens and cosmetics contain both nano-sized ZnO and TiO2, but cytotoxicity studies of such systems are meager. In this paper, the cytotoxicity of this dual-nanoparticle system comprising both ZnO and TiO2 was evaluated in vitro on skin-mimicking human primary epidermal keratinocytes (HPEKs). Inductively coupled plasma mass spectrometry, flow cytometry, and confocal microscopy were used to investigate the uptake of nanoparticles and free ions. Results revealed that ZnO nanoparticles were partially soluble (up to 20 μg ml-1 after 1 day) and could induce strong cytotoxicity as compared to the insoluble TiO2 nanoparticles which remained non-toxic until very high concentrations. It was found that TiO2 nanoparticles could play "vigilante" by protecting keratinocytes from acute toxicity of ZnO nanoparticles. This is in agreement with the observation that TiO2 nanoparticles caused an attenuation of free intracellular Zn2+ ions concentration, by adsorbing and immobilizing free Zn2+ ions. This study reveals a unique dual-nanoparticle observation in vitro on HPEKs, and highlights the importance of dual-nanoparticulate toxicity studies, especially in applications where more than one nanoparticle material-type is present.

  15. Effect of particle size on phase transition among metastable alumina nanoparticles: A view from high resolution 2D solid-state 27Al NMR study

    NASA Astrophysics Data System (ADS)

    Kim, H.; Lee, S.

    2012-12-01

    The detailed knowledge of atomic structures of diverse metastable/stable polymorphs in alumina nanoparticles is essential to understand their macroscopic properties. Alumina undergoes successive phase transitions from metastable γ-, δ-, and θ-alumina to stable α-alumina depending on types of precursors, annealing duration, and temperature. As large surface area of nanoparticles plays an important role in controlling their phase transitions, it is also necessary to explore the effect of particle size on nature of phase transition. Solid-state ^{27}Al NMR allows us to determine the atomic structure of Al sites in diverse amorphous/disordered silicates including alumina. However, generally, the crystallographically distinct Al sites among alumina polymorphs were not fully resolved in ^{27}Al magic angle spinning (MAS) NMR spectrum without performing a simulation of overlapped peaks for Al sites of metastable alumina in the spectra. Unfortunately, the simulation of 27Al MAS NMR spectra for alumina nanoparticles cannot be achieved well due to unconfirmed NMR parameters for Al sites of γ- and δ-alumina. The recent progress in triple-quantum (3Q) MAS can provide the much higher resolution for crystallographically distinct Al sites in amorphous alumina (Lee et al., 2009, Phys. Rev. Lett., 103, 095501; Lee et al., 2010, J. Phys. Chem. C, 114, 13890-13894) and aluminosilicate glasses (Lee, 2011, Proc. Natl. Acad. Sci., 108, 6847-6852) as well as crystalline layer silicates (Lee and Weiss, 2008, Am. Mineral. 93, 1066-1071). In this study, we report the ^{27}Al 2D 3QMAS and 1D MAS NMR spectra for alumina nanoparticles with varying particle size (e.g., 15, 19, and 27 nm) and temperature with an aim to explore the atomic structure of alumina polymorphs and nature of their phase transition sequence. The ^{27}Al 2D 3QMAS spectra show the resolved crystallographically distinct ^{[6]}Al and ^{[4]}Al sites in (γ, δ)-, θ-, and α-alumina in nanoparticles consisting of random

  16. Planar waveguide integrated spatial filter array

    NASA Astrophysics Data System (ADS)

    Ai, Jun; Dimov, Fedor; Lyon, Richard; Rakuljic, Neven; Griffo, Chris; Xia, Xiaowei; Arik, Engin

    2013-09-01

    An innovative integrated spatial filter array (iSFA) was developed for the nulling interferometer for the detection of earth-like planets and life beyond our solar system. The coherent iSFA comprised a 2D planar lightwave circuit (PLC) array coupled with a pair of 2D lenslet arrays in a hexagonal grid to achieve the optimum fill factor and throughput. The silica-on-silicon waveguide mode field diameter and numerical aperture (NA) were designed to match with the Airy disc and NA of the microlens for optimum coupling. The lenslet array was coated with a chromium pinhole array at the focal plane to pass the single-mode waveguide but attenuate the higher modes. We assembled a 32 by 30 array by stacking 32 chips that were produced by photolithography from a 6-in. silicon wafer. Each chip has 30 planar waveguides. The PLC array is inherently polarization-maintaining (PM) and requires much less alignment in contrast to a fiber array, where each PM fiber must be placed individually and oriented correctly. The PLC array offers better scalability than the fiber bundle array for large arrays of over 1,000 waveguides.

  17. Ferromagnetic resonance response of electron-beam patterned arrays of ferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Jung, Sukkoo; Watkins, Byron; Feller, Jeffrey; Ketterson, John; Chandrasekhar, Venkat

    2001-03-01

    We report on the fabrication and the dynamic magnetic properties of periodic permalloy dot arrays. Electron-beam lithography and e-gun evaporation have been used to make the arrays with the aspect ratio of 2 (dot diameter : 40 nm, height : 80 nm) and periods of 100 - 200 nm. The magnetic properties of the arrays and their interactions have been investigated by ferromagnetic resonance (FMR), magnetic force microscopy (MFM), and SQUID magnetometry. The measured FMR data show that the position and magnitude of resonant absorption peaks strongly depend on the angle between magnetic field and the lattice structure. The results of dot arrays with various kinds of structural parameters will be presented. Supported by Army Research Office, DAAD19-99-1-0334/P001

  18. Hollow V(2)O(5) nanoparticles (fullerene-like analogues) prepared by laser ablation.

    PubMed

    Levi, Roi; Bar-Sadan, Maya; Albu-Yaron, Ana; Popovitz-Biro, Ronit; Houben, Lothar; Shahar, Chen; Enyashin, Andrey; Seifert, Gotthard; Prior, Yehiam; Tenne, Reshef

    2010-08-18

    Nanoparticles of materials with layered structure are able to spontaneously form closed-cage nanostructures such as nested fullerene-like nanoparticles and nanotubes. This propensity has been demonstrated in a large number of compounds such as WS(2), NiCl(2), and others. Layered metal oxides possess a higher ionic character and consequently are stiffer and cannot be evenly folded. Vanadium pentoxide (V(2)O(5)), a layered metal oxide, has received much attention due to its attractive qualities in numerous applications such as catalysis and electronic and optical devices and as an electrode material for lithium rechargeable batteries. The synthesis by pulsed laser ablation (PLA) of V(2)O(5) hollow nanoparticles, which are closely (nearly) associated with inorganic "fullerene-like" (NIF-V(2)O(5)) nanoparticles, but not quite as perfect, is reported in the present work. The relation between the PLA conditions and the NIF-V(2)O(5) morphology is elucidated. A new mechanism leading to hollow nanostructure via crystallization of lower density amorphous nanoparticles is proposed. Transmission electron microscopy (TEM) is used extensively in conjunction with structural modeling of the NIF-V(2)O(5) in order to study the complex 3-D structure of the NIF-V(2)O(5) nanoparticles. This structure was shown to be composed of facets with their low-energy surfaces pointing outward and seamed by defective domains. These understandings are used to formulate a formation mechanism and may improve the function of V(2)O(5) in its many uses through additional morphological control. Furthermore, this study outlines which properties are required from layered compounds to fold into perfectly closed-cage IF nanoparticles.

  19. High-performance linear arrays of YBa2Cu3O7 superconducting infrared microbolometers on silicon

    NASA Astrophysics Data System (ADS)

    Johnson, Burgess R.; Foote, Marc C.; Marsh, Holly A.

    1995-06-01

    Single detectors and linear arrays of microbolometers utilizing the superconducting transition edge of YBa(subscript 2)Cu(subscript 3)O(subscript 7) have been fabricated by micromachining on silicon wafers. A D* of 8 +/- 2 X 10(superscript 9) cm Hz(superscript 1/2)/watt has been measured on a single detector. This is the highest D* reported on any superconducting microbolometer operating at temperatures higher than about 70 K. The NEP of this device was 1.5 X 10(superscript -12) watts/Hz(superscript HLF) at 2 Hz, at a temperature of 80.7 K. The thermal time constant was 105 msec, and the detector area was 140 micrometers X 105 micrometers . The use of batch silicon processing makes fabrication of linear arrays of these detectors relatively straightforward. The measured responsivity of detectors in one such array varied by less than 20% over the 6 mm length of the 64-element linear array. This measurement shows that good uniformity can be achieved at a single operating temperature in a superconductor microbolometer array, even when the superconducting resistive transition is a sharp function of temperature. The thermal detection mechanism of these devices gives them broadband response. This makes them especially useful at long wavelengths (e.g. (lambda) > 20 micrometers ), where they provide very high sensitivity at relatively high operating temperatures.

  20. High-resolution 3D laser imaging based on tunable fiber array link

    NASA Astrophysics Data System (ADS)

    Zhao, Sisi; Ruan, Ningjuan; Yang, Song

    2017-10-01

    Airborne photoelectric reconnaissance system with the bore sight down to the ground is an important battlefield situational awareness system, which can be used for reconnaissance and surveillance of complex ground scene. Airborne 3D imaging Lidar system is recognized as the most potential candidates for target detection under the complex background, and is progressing in the directions of high resolution, long distance detection, high sensitivity, low power consumption, high reliability, eye safe and multi-functional. However, the traditional 3D laser imaging system has the disadvantages of lower imaging resolutions because of the small size of the existing detector, and large volume. This paper proposes a high resolution laser 3D imaging technology based on the tunable optical fiber array link. The echo signal is modulated by a tunable optical fiber array link and then transmitted to the focal plane detector. The detector converts the optical signal into electrical signals which is given to the computer. Then, the computer accomplishes the signal calculation and image restoration based on modulation information, and then reconstructs the target image. This paper establishes the mathematical model of tunable optical fiber array signal receiving link, and proposes the simulation and analysis of the affect factors on high density multidimensional point cloud reconstruction.

  1. Formation of 2D nanoparticles with block structure in simultaneous electric explosion of conductors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kryzhevich, Dmitrij S., E-mail: kryzhev@ispms.ru, E-mail: kost@ispms.ru; Zolnikov, Konstantin P., E-mail: kryzhev@ispms.ru, E-mail: kost@ispms.ru; Abdrashitov, Andrei V.

    2014-11-14

    A molecular dynamics simulation of nanoparticle formation in simultaneous electric explosion of conductors is performed. Interatomic interaction is described using potentials calculated in the framework of the embedded atom method. High-rate heating results in failure of the conductors with the formation of nanoparticles. The influence of the heating rate, temperature distribution over the specimen cross-section and the distance between simultaneously exploded conductors on the structure of formed nanoparticles is studied. The calculation results show that the electric explosion of conductors allows the formation of nanoparticles with block structure.

  2. Copper-encapsulated vertically aligned carbon nanotube arrays.

    PubMed

    Stano, Kelly L; Chapla, Rachel; Carroll, Murphy; Nowak, Joshua; McCord, Marian; Bradford, Philip D

    2013-11-13

    A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites.

  3. Heat-resistant DNA tile arrays constructed by template-directed photoligation through 5-carboxyvinyl-2′-deoxyuridine

    PubMed Central

    Tagawa, Miho; Shohda, Koh-ichiroh; Fujimoto, Kenzo; Sugawara, Tadashi; Suyama, Akira

    2007-01-01

    Template-directed DNA photoligation has been applied to a method to construct heat-resistant two-dimensional (2D) DNA arrays that can work as scaffolds in bottom-up assembly of functional biomolecules and nano-electronic components. DNA double-crossover AB-staggered (DXAB) tiles were covalently connected by enzyme-free template-directed photoligation, which enables a specific ligation reaction in an extremely tight space and under buffer conditions where no enzymes work efficiently. DNA nanostructures created by self-assembly of the DXAB tiles before and after photoligation have been visualized by high-resolution, tapping mode atomic force microscopy in buffer. The improvement of the heat tolerance of 2D DNA arrays was confirmed by heating and visualizing the DNA nanostructures. The heat-resistant DNA arrays may expand the potential of DNA as functional materials in biotechnology and nanotechnology. PMID:17982178

  4. Nanopillar arrays of amorphous carbon nitride

    NASA Astrophysics Data System (ADS)

    Sai Krishna, Katla; Pavan Kumar, B. V. V. S.; Eswaramoorthy, Muthusamy

    2011-07-01

    Nanopillar arrays of amorphous carbon nitride have been prepared using anodic aluminum oxide (AAO) membrane as a template. The amine groups present on the surface of these nanopillars were exploited for functionalization with oleic acid in order to stabilize the nanostructure at the aqueous-organic interface and also for the immobilization of metal nanoparticles and protein. These immobilised nanoparticles were found to have good catalytic activity.

  5. Hierarchical nanoparticle assemblies formed by decorating breath figures.

    PubMed

    Böker, Alexander; Lin, Yao; Chiapperini, Kristen; Horowitz, Reina; Thompson, Mike; Carreon, Vincent; Xu, Ting; Abetz, Clarissa; Skaff, Habib; Dinsmore, A D; Emrick, Todd; Russell, Thomas P

    2004-05-01

    The combination of two self-assembly processes on different length scales leads to the formation of hierarchically structured nanoparticle arrays. Here, the formation of spherical cavities, or 'breath figures'-made by the condensation of micrometre-sized water droplets on the surface of a polymer solution-that self-assemble into a well-ordered hexagonal array, is combined with the self-assembly of CdSe nanoparticles at the polymer solution-water droplet interface. Complete evaporation of the solvent and water confines the particle assembly to an array of spherical cavities and allows for ex situ investigation. Fluorescence confocal, transmission electron and scanning electron microscope images show the preferential segregation of the CdSe nanoparticles to the polymer solution-water interface where they form a 5-7-nm-thick layer, thus functionalizing the walls of the holes. This process opens a new route to fabricating highly functionalized ordered microarrays of nanoparticles, potentially useful in sensory, separation membrane or catalytic applications.

  6. Syntheses of Eu-Activated Alkaline Earth Fluoride MF2 (M=Ca, Sr) Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hong, Byung-Chul; Kawano, Katsuyasu

    2007-09-01

    The Eu2+ ion-activated CaF2 and SrF2 nanoparticles were prepared by the sol-gel technique assisted with the trifluoro-acetic acid (TFA), and were evaluated by X-ray diffraction (XRD), photoluminescence (PL), photoluminescence excitation (PLE) measurements and atomic force microscopy (AFM) observation. A modified reducing method based on the thermal-carbon reducing atmosphere (TCRA) treatment using activated carbon was proposed to realize the effective reduction from Eu3+ to Eu2+ ions, in which the nanoparticles showed a strong and broad luminescence due to the parity allowed 4f7-4f65d1 transition. From the XRD results, it was found that the average particle size proportionally increased in the range of 15 to 120 nm and 10 to 100 nm for CaF2 and SrF2, respectively, with increasing sintering temperatures 300-700 °C. The surface images of nanoparticles obtained by the AFM revealed that the grains with high uniformity grew with increasing TCRA temperatures. It was confirmed that the reduced Eu2+ ions were homogeneously dispersed with the critical distance 16-17 Å in the fluoride nanoparticles from the concentration quenching results.

  7. Polymer (PDMS-Fe3O4) magneto-dielectric substrate for a MIMO antenna array

    NASA Astrophysics Data System (ADS)

    Alqadami, Abdulrahman Shueai Mohsen; Jamlos, Mohd Faizal; Soh, Ping Jack; Kamarudin, Muhammad Ramlee

    2016-01-01

    This paper presents the design of a 2 × 4 multiple-input multiple-output (MIMO) antenna array fabricated on a nanocomposite magneto-dielectric polymer substrate. The 10-nm iron oxide (Fe3O4) nanoparticles and polydimethylsiloxane (PDMS) composite is used as substrate to enhance the performance of a MIMO antenna array. The measured results showed up to 40.8 % enhancement in terms of bandwidth, 9.95 dB gain, and 57 % of radiation efficiency. Furthermore, it is found that the proposed magneto-dielectric (PDMS-Fe3O4) composite substrate provides excellent MIMO parameters such as correlation coefficient, diversity gain, and mutual coupling. The prototype of the proposed antenna is transparent, flexible, lightweight, and resistant against dust and corrosion. Measured results indicate that the proposed antenna is suitable for WLAN and ultra-wideband biomedical applications within frequency range of 5.33-7.70 GHz.

  8. Efficient PbS/CdS co-sensitized solar cells based on TiO2 nanorod arrays

    PubMed Central

    2013-01-01

    Narrow bandgap PbS nanoparticles, which may expand the light absorption range to the near-infrared region, were deposited on TiO2 nanorod arrays by successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The thicknesses of PbS nanoparticles were optimized to enhance the photovoltaic performance of PbS QDSCs. A uniform CdS layer was directly coated on previously grown PbS-TiO2 photoanode to protect the PbS from the chemical attack of polysulfide electrolytes. A remarkable short-circuit photocurrent density (approximately 10.4 mA/cm2) for PbS/CdS co-sensitized solar cell was recorded while the photocurrent density of only PbS-sensitized solar cells was lower than 3 mA/cm2. The power conversion efficiency of the PbS/CdS co-sensitized solar cell reached 1.3%, which was beyond the arithmetic addition of the efficiencies of single constituents (PbS and CdS). These results indicate that the synergistic combination of PbS with CdS may provide a stable and effective sensitizer for practical solar cell applications. PMID:23394609

  9. A 5-MHz cylindrical dual-layer transducer array for 3-D transrectal ultrasound imaging.

    PubMed

    Chen, Yuling; Nguyen, Man; Yen, Jesse T

    2012-07-01

    Two-dimensional transrectal ultrasound (TRUS) is being used in guiding prostate biopsies and treatments. In many cases, the TRUS probes are moved manually or mechanically to acquire volumetric information, making the imaging slow, user dependent, and unreliable. A real-time three-dimensional (3-D) TRUS system could improve reliability and volume rates of imaging during these procedures. In this article, the authors present a 5-MHz cylindrical dual-layer transducer array capable of real-time 3-D transrectal ultrasound without any mechanically moving parts. Compared with fully sampled 2-D arrays, this design substantially reduces the channel count and fabrication complexity. This dual-layer transducer uses PZT elements for transmit and P[VDF-TrFE] copolymer elements for receive, respectively. The mechanical flexibility of both diced PZT and copolymer makes it practical for transrectal applications. Full synthetic aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics Data Acquisition System. Offline 3-D beamforming was then performed to obtain volumes of two wire phantoms and a cyst phantom. Generalized coherence factor was applied to improve the contrast of images. The measured -6-dB fractional bandwidth of the transducer was 62% with a center frequency of 5.66 MHz. The measured lateral beamwidths were 1.28 mm and 0.91 mm in transverse and longitudinal directions, respectively, compared with a simulated beamwidth of 0.92 mm and 0.74 mm.

  10. Effect of nanoparticle encapsulation on the photostability of the sunscreen agent, 2-ethylhexyl-p-methoxycinnamate.

    PubMed

    Perugini, P; Simeoni, S; Scalia, S; Genta, I; Modena, T; Conti, B; Pavanetto, F

    2002-10-10

    The aim of this study was to investigate the influence of nanoparticle-based systems on the light-induced decomposition of the sunscreen agent, trans-2-ethylhexyl-p-methoxycinnamate (trans-EHMC). Ethylcellulose (EC) and poly-D,L-lactide-co-glycolide (PLGA) were used as biocompatible polymers for the preparation of the particulate systems. The "salting out" method was used for nanoparticle preparation and several variables were evaluated in order to optimize product characteristics. The photodegradation of the sunscreen agent in emulsion vehicles was reduced by encapsulation into the PLGA nanoparticles (the extent of degradation was 35.3% for the sunscreen-loaded nanoparticles compared to 52.3% for free trans-EHMC) whereas the EC nanoparticle system had no significant effect. Therefore, PLGA nanoparticles loaded with trans-EHMC improve the photostability of the sunscreen agent.

  11. Experimental study on the coalescence process of SiO2 supported colloidal Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Ruffino, F.; Torrisi, V.; Grimaldi, M. G.

    2015-11-01

    We report on an experimental study of the coalescence-driven grow process of colloidal Au nanoparticles on SiO2 surface. Nanoparticles with 30, 50, 80, 100 nm nominal diameters on a SiO2 substrate were deposited, from solutions, by the drop-casting method. Then, annealing processes, in the 573-1173 K temperature range and 900-3600 s time range, were performed. Using scanning electron microscopy analyses, the temporal evolution of the nanoparticles sizes has been studied. In particular, for all classes of nanoparticles, the experimental-obtained diameters distributions evidenced double-peak shapes (i. e. bimodal distributions): a first peak centered (and unchanged changing the annealing temperature and/or time) at the nominal diameter of the as-deposited nanoparticles, <D0>, and a second peak shifting at higher mean diameters, , increasing the annealing temperature and/or time. This observation suggested us a coalescence-driven growth process of a nanoparticles sub-population. As a consequence, the temporal evolution of (for each class of nanoparticles and each annealing temperature), within the well-established particles coalescence theoretical framework, has been analyzed. In particular, by the analyses of the experimental data using relations as prescribed by the theoretical model, a characteristic size-dependent activation energy for the Au nanoparticles coalescence process has been evaluated.

  12. Flexible nanohybrid microelectrode based on carbon fiber wrapped by gold nanoparticles decorated nitrogen doped carbon nanotube arrays: In situ electrochemical detection in live cancer cells.

    PubMed

    Zhang, Yan; Xiao, Jian; Sun, Yimin; Wang, Lu; Dong, Xulin; Ren, Jinghua; He, Wenshan; Xiao, Fei

    2018-02-15

    The rapidly growing demand for in situ real-time monitoring of chemical information in vitro and in vivo has attracted tremendous research efforts into the design and construction of high-performance biosensor devices. Herein, we develop a new type of flexible nanohybrid microelectrode based on carbon fiber wrapped by gold nanoparticles decorated nitrogen-doped carbon nanotube arrays, and explore its practical application in in situ electrochemical detection of cancer biomarker H 2 O 2 secreted from live cancer cells. Our results demonstrate that carbon fiber material with microscale size and fascinating mechanical properties can be used as a robust and flexible microelectrode substrate in the electrochemical biosensor system. And the highly ordered nitrogen-doped carbon nanotube arrays that grown on carbon fiber possess high surface area-to-volume ratio and abundant active sites, which facilitate the loading of high-density and uniformly dispersed gold nanoparticles on it. Benefited from the unique microstructure and excellent electrocatalytic properties of different components in the nanohybrid fiber microelectrode, an effective electrochemical sensing platform based on it has been built up for the sensitive and selective detection of H 2 O 2 , the detection limit is calculated to be 50nM when the signal-to-noise ratio is 3:1, and the linear dynamic range is up to 4.3mM, with a high sensitivity of 142µAcm -2 mM -1 . These good sensing performances, coupled with its intrinsic mechanical flexibility and biocompatibility, allow for its use in in situ real-time tracking H 2 O 2 secreted from breast cancer cell lines MCF-7 and MBA-MD-231, and evaluating the sensitivity of different cancer cells to chemotherapy or radiotherapy treatments, which hold great promise for clinic application in cancer diagnose and management. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Self-organization in complex oxide thin films: from 2D to 0D nanostructures of SrRuO3 and CoCr2O4

    NASA Astrophysics Data System (ADS)

    Sánchez, F.; Lüders, U.; Herranz, G.; Infante, I. C.; Fontcuberta, J.; García-Cuenca, M. V.; Ferrater, C.; Varela, M.

    2005-05-01

    We report here on the controlled fabrication of nanostructures of varied dimensionality by self-organization processes in the heteroepitaxial growth of SrRuO3 (SRO) and CoCr2O4 (CCO) films. The surface of SRO films on SrTiO3(001) substrates can show extremely smooth terraces (2D objects) separated by atomic steps, a structure of faceted islands (0D objects), a cross-hatch morphology (1D objects), an array of finger-like units (1D objects), or an array of giant bunched steps (1D objects). The surface can be tailored to a particular structure by controlling the vicinality of the substrate and the growth rate and nominal thickness of the film. In the case of CCO films, grown on (001)-oriented MgAl2O4 or MgO substrates, high aspect ratio {111}-faceted pyramids and hut clusters (0D objects), highly oriented and having a similar size, appear above a critical thickness. The size and spatial density can be tuned by varying deposition temperature, nominal thickness, and substrate. This dependence allows the fabrication of surfaces being fully faceted (2D objects), or having arrays of dislocated pyramids of up to micrometric size, or small coherently lattice strained pyramids having a nanometric size. We discuss the driving forces that originate the peculiar SRO and CCO nanostructures. The findings illustrate that the growth of complex oxides can promote a variety of novel self-organized morphologies, and suggest original strategies to fabricate templates or hybrid structures of oxides combining varied functionalities.

  14. Lithography-free fabrication of silicon nanowire and nanohole arrays by metal-assisted chemical etching

    PubMed Central

    2013-01-01

    We demonstrated a novel, simple, and low-cost method to fabricate silicon nanowire (SiNW) arrays and silicon nanohole (SiNH) arrays based on thin silver (Ag) film dewetting process combined with metal-assisted chemical etching. Ag mesh with holes and semispherical Ag nanoparticles can be prepared by simple thermal annealing of Ag thin film on a silicon substrate. Both the diameter and the distribution of mesh holes as well as the nanoparticles can be manipulated by the film thickness and the annealing temperature. The silicon underneath Ag coverage was etched off with the catalysis of metal in an aqueous solution containing HF and an oxidant, which form silicon nanostructures (either SiNW or SiNH arrays). The morphologies of the corresponding etched SiNW and SiNH arrays matched well with that of Ag holes and nanoparticles. This novel method allows lithography-free fabrication of the SiNW and SiNH arrays with control of the size and distribution. PMID:23557325

  15. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  16. Aptamer-based microfluidic beads array sensor for simultaneous detection of multiple analytes employing multienzyme-linked nanoparticle amplification and quantum dots labels.

    PubMed

    Zhang, He; Hu, Xinjiang; Fu, Xin

    2014-07-15

    This study reports the development of an aptamer-mediated microfluidic beads-based sensor for multiple analytes detection and quantification using multienzyme-linked nanoparticle amplification and quantum dots labels. Adenosine and cocaine were selected as the model analytes to validate the assay design based on strand displacement induced by target-aptamer complex. Microbeads functionalized with the aptamers and modified electron rich proteins were arrayed within a microfluidic channel and were connected with the horseradish peroxidases (HRP) and capture DNA probe derivative gold nanoparticles (AuNPs) via hybridization. The conformational transition of aptamer induced by target-aptamer complex contributes to the displacement of functionalized AuNPs and decreases the fluorescence signal of microbeads. In this approach, increased binding events of HRP on each nanosphere and enhanced mass transport capability inherent from microfluidics are integrated for enhancing the detection sensitivity of analytes. Based on the dual signal amplification strategy, the developed aptamer-based microfluidic bead array sensor could discriminate as low as 0.1 pM of adenosine and 0.5 pM cocaine, and showed a 500-fold increase in detection limit of adenosine compared to the off-chip test. The results proved the microfluidic-based method was a rapid and efficient system for aptamer-based targets assays (adenosine (0.1 pM) and cocaine (0.5 pM)), requiring only minimal (microliter) reagent use. This work demonstrated the successful application of aptamer-based microfluidic beads array sensor for detection of important molecules in biomedical fields. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Sensor Arrays from Multicomponent Micropatterned Nanoparticles and Graphene

    DTIC Science & Technology

    2013-10-10

    UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Case Western Reserve University,Case School of Engineering,Cleveland, OH ,44106 8...treatment, followed by region-selective substrate-enhanced electroless deposition of Au nanoparticles and solution alkalization of ferrous chloride...tetrahydrate in the presence of ammonia into Fe3O4 nanoparticles. The resultant Fe3O4/ Au multicomponent micropatterned-graphene films were found to be highly

  18. Aging of TiO2 Nanoparticles Transiently Increases Their Toxicity to the Pelagic Microcrustacean Daphnia magna

    PubMed Central

    Seitz, Frank; Lüderwald, Simon; Rosenfeldt, Ricki R.; Schulz, Ralf; Bundschuh, Mirco

    2015-01-01

    During their aquatic life cycle, nanoparticles are subject to environmentally driven surface modifications (e.g. agglomeration or coating) associated with aging. Although the ecotoxicological potential of nanoparticles might be affected by these processes, only limited information about the potential impact of aging is available. In this context, the present study investigated acute (96 h) and chronic (21 d) implications of systematically aged titanium dioxide nanoparticles (nTiO2; ~90 nm) on the standard test species Daphnia magna by following the respective test guidelines. The nTiO2 were aged for 0, 1, 3 and 6 d in media with varying ionic strengths (Milli-Q water: approx. 0.00 mmol/L and ASTM: 9.25 mmol/L) in the presence or absence of natural organic matter (NOM). Irrespective of the other parameters, aging in Milli-Q did not change the acute toxicity relative to an unaged control. In contrast, 6 d aged nTiO2 in ASTM without NOM caused a fourfold decreased acute toxicity. Relative to the 0 d aged particles, nTiO2 aged for 1 and 3 d in ASTM with NOM, which is the most environmentally-relevant setup used here, significantly increased acute toxicity (by approximately 30%), while a toxicity reduction (60%) was observed for 6 d aged nTiO2. Comparable patterns were observed during the chronic experiments. A likely explanation for this phenomenon is that the aging of nTiO2 increases the particle size at the start of the experiment or the time of the water exchange from <100 nm to approximately 500 nm, which is the optimal size range to be taken up by filter feeding D. magna. If subjected to further agglomeration, larger nTiO2 particles, however, cannot be retained by the daphnids’ filter apparatus ultimately reducing their ecotoxicological potential. This non-linear pattern of increasing and decreasing nTiO2 related toxicity over the aging duration, highlights the knowledge gap regarding the underlying mechanisms and processes. This understanding seems, however

  19. Investigation of the Optical and Sensing Characteristics of Nanoparticle Arrays for High Temperature Applications

    NASA Astrophysics Data System (ADS)

    Dharmalingam, Gnanaprakash

    realized through control of the shape and geometry of the catalytically active Au nanoparticles. While this is not possible through the layer by layer sputter deposition approach, this level of control has been realized through the use of electron beam lithography to fabricate nanocomposite arrays. Sensing results towards the detection of H2 will be highlighted with specific concerns related to optimization of these nanorod arrays detailed. The proposed work will discuss the various parameters for optimization of these arrays, which would enable them to be used as reliable, sensitive and selective harsh environmental sensors.

  20. Optical properties and band alignments in ZnTe nanoparticles/MoS2 layer hetero-interface using SE and KPFM studies

    NASA Astrophysics Data System (ADS)

    Sharma, Intu; Mehta, B. R.

    2017-11-01

    Integration of a layered two-dimensional (2D) material with a non-2D material provides a platform where one can modulate and achieve the properties desired for various next-generation electronic and opto-electronic applications. Here, we investigated ZnTe nanoparticles/MoS2 hetero-interfaces with the thickness of the MoS2 varying from few to multilayer. High-resolution transmission electron microscopy was used to observe the crystalline behaviour of the ZnTe nanoparticles, while the number of MoS2 layers was investigated using Raman measurements. Spectroscopic ellipsometry (SE) analysis based on the five-layer fitting model was used to analyse the optical behaviour of the heterojunction, where the excitonic features corresponding to the MoS2 layers and absorption features due to the ZnTe nanoparticles are observed. From the Kelvin probe force microscopy (KPFM) measurements, the surface potential (SP) of the ZnTe nanoparticles/MoS2 is found to be different in comparison with the SP of the ZnTe nanoparticles and MoS2, which is indicative of the charge transfer at the ZnTe nanoparticles/MoS2 hetero-interface. Various parameters obtained using SE and KPFM measurements were used to propose energy band alignments at the ZnTe nanoparticles/MoS2 hetero-interface. In addition, an interface photovoltage of 193 mV was obtained by carrying out KPFM measurements under illuminating condition.

  1. TiO2 Nanoparticle Uptake by the Water Flea Daphnia magna via Different Routes is Calcium-Dependent.

    PubMed

    Tan, Ling-Yan; Huang, Bin; Xu, Shen; Wei, Zhong-Bo; Yang, Liu-Yan; Miao, Ai-Jun

    2016-07-19

    Calcium plays versatile roles in aquatic ecosystems. In this study, we investigated its effects on the uptake of polyacrylate-coated TiO2 nanoparticles (PAA-TiO2-NPs) by the water flea (cladoceran) Daphnia magna. Particle distribution in these daphnids was also visualized using synchrotron radiation-based micro X-ray fluorescence spectroscopy, transmission electron microscopy, and scanning electron microscopy. At low ambient Ca concentrations in the experimental medium ([Ca]dis), PAA-TiO2-NPs were well dispersed and distributed throughout the daphnid; the particle concentration was highest in the abdominal zone and the gut, as a result of endocytosis and passive drinking of the nanoparticles, respectively. Further, Ca induced PAA-TiO2-NP uptake as a result of the increased Ca influx. At a high [Ca]dis, the PAA-TiO2-NPs formed micrometer-sized aggregates that were ingested by D. magna and concentrated only in its gut, independent of the Ca influx. Our results demonstrated the multiple effects of Ca on nanoparticle bioaccumulation. Specifically, well-dispersed nanoparticles were taken up by D. magna through endocytosis and passive drinking whereas the uptake of micrometer-sized aggregates relied on active ingestion.

  2. Size dependent magnetic and magneto-optical properties of Ni0.2Zn0.8Fe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Oksana A.; Lin, Chun-Rong; Chen, Hung-Yi; Hsu, Hua-Shu; Shih, Kun-Yauh; Edelman, Irina S.; Wu, Kai-Wun; Tseng, Yaw-Teng; Ovchinnikov, Sergey G.; Lee, Jiann-Shing

    2016-06-01

    Ni0.2Zn0.8Fe2O4 spinel nanoparticles have been synthesized by combustion method. Average particles size varies from 15.5 to 50.0 nm depending on annealing temperature. Correlations between particles size and magnetic and magneto-optical properties are investigated. Magnetization dependences on temperature and external magnetic field correspond to the sum of paramagnetic and superparamagnetic response. Critical size of single-domain transition is found to be 15.9 nm. Magnetic circular dichroism (MCD) studies of nickel zinc spinel are presented here for the first time. The features in magnetic circular dichroism spectrum are assigned to the one-ion d-d transitions in Fe3+ and Ni2+ ions, as well to the intersublattice and intervalence charge transfer transitions. The MCD spectrum rearrangement was revealed with the change of the nanoparticles size.

  3. Hybrid nanostructures of well-organized arrays of colloidal quantum dots and a self-assembled monolayer of gold nanoparticles for enhanced fluorescence

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoying; McBride, Sean P.; Jaeger, Heinrich M.; Nealey, Paul F.

    2016-07-01

    Hybrid nanomaterials comprised of well-organized arrays of colloidal semiconductor quantum dots (QDs) in close proximity to metal nanoparticles (NPs) represent an appealing system for high-performance, spectrum-tunable photon sources with controlled photoluminescence. Experimental realization of such materials requires well-defined QD arrays and precisely controlled QD-metal interspacing. This long-standing challenge is tackled through a strategy that synergistically combines lateral confinement and vertical stacking. Lithographically generated nanoscale patterns with tailored surface chemistry confine the QDs into well-organized arrays with high selectivity through chemical pattern directed assembly, while subsequent coating with a monolayer of close-packed Au NPs introduces the plasmonic component for fluorescence enhancement. The results show uniform fluorescence emission in large-area ordered arrays for the fabricated QD structures and demonstrate five-fold fluorescence amplification for red, yellow, and green QDs in the presence of the Au NP monolayer. Encapsulation of QDs with a silica shell is shown to extend the design space for reliable QD/metal coupling with stronger enhancement of 11 times through the tuning of QD-metal spatial separation. This approach provides new opportunities for designing hybrid nanomaterials with tailored array structures and multiple functionalities for applications such as multiplexed optical coding, color display, and quantum transduction.

  4. Biomimicry 3D gastrointestinal spheroid platform for the assessment of toxicity and inflammatory effects of zinc oxide nanoparticles.

    PubMed

    Chia, Sing Ling; Tay, Chor Yong; Setyawati, Magdiel I; Leong, David T

    2015-02-11

    Our current mechanistic understanding on the effects of engineered nanoparticles (NPs) on cellular physiology is derived mainly from 2D cell culture studies. However, conventional monolayer cell culture may not accurately model the mass transfer gradient that is expected in 3D tissue physiology and thus may lead to artifactual experimental conclusions. Herein, using a micropatterned agarose hydrogel platform, the effects of ZnO NPs (25 nm) on 3D colon cell spheroids of well-defined sizes are examined. The findings show that cell dimensionality plays a critical role in governing the spatiotemporal cellular outcomes like inflammatory response and cytotoxicity in response to ZnO NPs treatment. More importantly, ZnO NPs can induce different modes of cell death in 2D and 3D cell culture systems. Interestingly, the outer few layers of cells in 3D model could only protect the inner core of cells for a limited time and periodically slough off from the spheroids surface. These findings suggest that toxicological conclusions made from 2D cell models might overestimate the toxicity of ZnO NPs. This 3D cell spheroid model can serve as a reproducible platform to better reflect the actual cell response to NPs and to study a more realistic mechanism of nanoparticle-induced toxicity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Optical analysis of nanoparticles via enhanced backscattering facilitated by 3-D photonic nanojets

    NASA Astrophysics Data System (ADS)

    Li, Xu; Chen, Zhigang; Taflove, Allen; Backman, Vadim

    2005-01-01

    We report the phenomenon of ultra-enhanced backscattering of visible light by nanoparticles facilitated by the 3-D photonic nanojet a sub-diffraction light beam appearing at the shadow side of a plane-waveilluminated dielectric microsphere. Our rigorous numerical simulations show that backscattering intensity of nanoparticles can be enhanced up to eight orders of magnitude when locating in the nanojet. As a result, the enhanced backscattering from a nanoparticle with diameter on the order of 10 nm is well above the background signal generated by the dielectric microsphere itself. We also report that nanojet-enhanced backscattering is extremely sensitive to the size of the nanoparticle, permitting in principle resolving sub-nanometer size differences using visible light. Finally, we show how the position of a nanoparticle could be determined with subdiffractional accuracy by recording the angular distribution of the backscattered light. These properties of photonic nanojets promise to make this phenomenon a useful tool for optically detecting, differentiating, and sorting nanoparticles.

  6. SU-F-T-458: Tracking Trends of TG-142 Parameters Via Analysis of Data Recorded by 2D Chamber Array

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alexandrian, A; Kabat, C; Defoor, D

    Purpose: With increasing QA demands of medical physicists in clinical radiation oncology, the need for an effective method of tracking clinical data has become paramount. A tool was produced which scans through data automatically recorded by a 2D chamber array and extracts relevant information recommended by TG-142. Using this extracted information a timely and comprehensive analysis of QA parameters can be easily performed enabling efficient monthly checks on multiple linear accelerators simultaneously. Methods: A PTW STARCHECK chamber array was used to record several months of beam outputs from two Varian 2100 series linear accelerators and a Varian NovalisTx−. In conjunctionmore » with the chamber array, a beam quality phantom was used to simultaneously to determine beam quality. A minimalist GUI was created in MatLab that allows a user to set the file path of the data for each modality to be analyzed. These file paths are recorded to a MatLab structure and then subsequently accessed by a script written in Python (version 3.5.1) which then extracts values required to perform monthly checks as outlined by recommendations from TG-142. The script incorporates calculations to determine if the values recorded by the chamber array fall within an acceptable threshold. Results: Values obtained by the script are written to a spreadsheet where results can be easily viewed and annotated with a “pass” or “fail” and saved for further analysis. In addition to creating a new scheme for reviewing monthly checks, this application allows for able to succinctly store data for follow up analysis. Conclusion: By utilizing this tool, parameters recommended by TG-142 for multiple linear accelerators can be rapidly obtained and analyzed which can be used for evaluation of monthly checks.« less

  7. Closed-Form 3-D Localization for Single Source in Uniform Circular Array with a Center Sensor

    NASA Astrophysics Data System (ADS)

    Bae, Eun-Hyon; Lee, Kyun-Kyung

    A novel closed-form algorithm is presented for estimating the 3-D location (azimuth angle, elevation angle, and range) of a single source in a uniform circular array (UCA) with a center sensor. Based on the centrosymmetry of the UCA and noncircularity of the source, the proposed algorithm decouples and estimates the 2-D direction of arrival (DOA), i.e. azimuth and elevation angles, and then estimates the range of the source. Notwithstanding a low computational complexity, the proposed algorithm provides an estimation performance close to that of the benchmark estimator 3-D MUSIC.

  8. Comparison of Fe2O3 and Fe2CoO4 core-shell plasmonic nanoparticles for aptamer mediated SERS assays

    NASA Astrophysics Data System (ADS)

    Marks, Haley; Mabbott, Samuel; Huang, Po-Jung; Jackson, George W.; Kameoka, Jun; Graham, Duncan; Coté, Gerard L.

    2016-03-01

    Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a `target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.

  9. Direct observation of two-step crystallization in nanoparticle superlattice formation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Park, Jungwon; Zheng, Haimei; Lee, Won Chul

    2011-10-06

    Direct imaging of nanoparticle solutions by liquid phase transmission electron microscopy has enabled unique in-situ studies of nanoparticle motion and growth. In the present work, we report on real-time formation of two-dimensional nanoparticle arrays in the very low diffusive limit, where nanoparticles are mainly driven by capillary forces and solvent fluctuations. We find that superlattice formation appears to be segregated into multiple regimes. Initially, the solvent front drags the nanoparticles, condensing them into an amorphous agglomerate. Subsequently, the nanoparticle crystallization into an array is driven by local fluctuations. Following the crystallization event, superlattice growth can also occur via the additionmore » of individual nanoparticles drawn from outlying regions by different solvent fronts. The dragging mechanism is consistent with simulations based on a coarse-grained lattice gas model at the same limit.« less

  10. International Space Station 2A Array Modal Analysis

    NASA Technical Reports Server (NTRS)

    Laible, Michael; Fitzpatrick, Kristin; Grygier, Michael

    2012-01-01

    On December 9th 2009, the International Space Station (ISS) 2A solar array mast experienced prolonged longeron shadowing during a Soyuz undocking. Analytical reconstruction of induced thermal and dynamic structural loads showed an exceedance of the mast buckling limit. Possible structural damage to the solar array mast could have occurred during this event. A Low fidelity video survey of the 2A mast showed no obvious damage of the mast longerons or battens. The decision was made to conduct an on-orbit dynamic test of the 2A array on December 18th, 2009. The test included thruster pluming on the array while photogrammetry data was recorded. The test was similar to other Dedicated Thruster Firings (DTFs) that were performed to measure structural frequency and damping of a solar array. Results of the DTF indicated lower frequency mast modes than model predictions, thus leading to speculation of mast damage. A detailed nonlinear analysis was performed on the 2A array model to assess possible solutions to modal differences. The setup of the parametric nonlinear trade study included the use of a detailed array model and the reduced mass and stiffness matrices of the entire ISS being applied to the array interface. The study revealed that the array attachment structure is nonlinear and thus was the source of error in the model prediction of mast modes. In addition, a detailed study was performed to determine mast mode sensitivity to mast longeron damage. This sensitivity study was performed to assess if the ISS program has sufficient instrumentation for mast damage detection.

  11. Laser tailored nanoparticle arrays to detect molecules at dilute concentration

    NASA Astrophysics Data System (ADS)

    Zanchi, Chiara; Lucotti, Andrea; Tommasini, Matteo; Trusso, Sebastiano; de Grazia, Ugo; Ciusani, Emilio; Ossi, Paolo M.

    2017-02-01

    By nanosecond pulsed laser ablation in an ambient gas gold nanoparticles (NPs) were produced that self-assemble on a substrate resulting in increasingly elaborated architectures of growing thickness, from isolated NP arrays up to percolated films. NPs nucleate and grow in the plasma plume propagating through the gas. Process parameters including laser wavelength, laser energy density, target to substrate distance, nature and pressure of the gas affect plasma expansion, thus asymptotic NP size and kinetic energy. NP size, energy and mobility at landing determine film growth and morphology that affect the physico-chemical properties of the film. Keeping fixed the other process parameters, we discuss the sensitive dependence of film surface nanostructure on Ar pressure and on laser pulse number. The initial plume velocity and average ablated mass per pulse allow predicting the asymptotic NP size. The control of growth parameters favors fine-tuning of NP aggregation, relevant to plasmonics to get optimized substrates for surface enhanced Raman spectroscopy (SERS). Their behavior is discussed for testing conditions of interest for clinical application. Both in aqueous and in biological solutions we obtained good sensitivity and reproducibility of the SERS signals for the anti-Parkinson drug apomorphine, and for the anti-epilepsy drug carbamazepine.

  12. Preparation, characterization, and application of titanium nano-tube array in dye-sensitized solar cells

    PubMed Central

    2012-01-01

    The vertically orientated TiO2 nanotube array (TNA) decorated with TiO2 nano-particles was successfully fabricated by electrochemically anodizing titanium (Ti) foils followed by Ti-precursor post-treatment and annealing process. The TNA morphology characterized by SEM and TEM was found to be filled with TiO2 nano-particles interior and exterior of the TiO2 nano-tubes after titanium (IV) n-butoxide (TnB) treatment, whereas TiO2 nano-particles were only found inside of TiO2 nano-tubes upon titanium tetrachloride (TiCl4) treatment. The efficiency in TNA-based DSSCs was improved by both TnB and TiCl4 treatment presumably due to the increase of dye adsorption. PMID:22353282

  13. Disposition of lypophilized (methylmethacrylate-14C, 2-hydroxyethylmethacrylate, butylacrylate) nanoparticles in rats and their effect on zoxazolamine paralysis time.

    PubMed

    Kukan, M; Koprda, V; Bezek, S; Kálal, J; Labský, J; Trnovec, T

    1991-01-01

    The fate of lyophilized (methylmethacrylate-14C, 2-hydroxyethylmethacrylate, butylacrylate) nanoparticles was studied in male Wistar rats after p.o. administration. It was found that at least 4% of the dose of 14C was absorbed from the gastrointestinal tract after a single dose with these nanoparticles. Some radioactivity (less than 0.15% of dose) was found 7 d after administration in lung, spleen and liver. As expected excretion of the label was predominated via the feces. Ten d of p.o. treatment of rats with lyophilized nanoparticles (1 g/kg of body weight) was shown to prolong significantly zoxazolamine paralysis time. This result suggests that lyophilized nanoparticles decreased elimination of zoxazolamine.

  14. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    PubMed Central

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

  15. Chronic impacts of TiO2 nanoparticles on Populus nigra L. leaf decomposition in freshwater ecosystem.

    PubMed

    Du, Jingjing; Zhang, Yuyan; Guo, Wei; Li, Ningyun; Gao, Chaoshuai; Cui, Minghui; Lin, Zhongdian; Wei, Mingbao; Zhang, Hongzhong

    2018-05-15

    Titanium dioxide (TiO 2 ) nanoparticles have been applied in diverse commercial products, which could lead to toxic effects on aquatic microbes and would inhibit some important ecosystem processes. The study aimed to investigate the chronic impacts of TiO 2 nanoparticles with different concentrations (5, 50, and 500 mg L -1 ) on Populus nigra L. leaf decomposition in the freshwater ecosystem. After 50 d of decomposing, a significant decrease in decomposition rates was observed with higher concentrations of TiO 2 nanoparticles. During the period of litter decomposition, exposure of TiO 2 nanoparticles led to decreases in extracellular enzyme activities, which was caused by the reduction of microbial especially fungal biomass. In addition, the diversity and composition of the fungal community associated with litter decomposition were strongly affected by the concentrations of TiO 2 nanoparticles. The diversity and composition of the fungal community associated with litter decomposition was strongly affected. The abundance of Tricladium chaetocladium decreased with the increasing concentrations of TiO 2 nanoparticles, indicating the little contribution of the species to the litter decomposition. In conclusion, this study provided the evidence for the chronic exposure effects of TiO 2 nanoparticles on the litter decomposition and further the functions of freshwater ecosystems. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Anchorage of γ-Al 2O 3 nanoparticles on nitrogen-doped multiwalled carbon nanotubes

    DOE PAGES

    Rodríguez-Pulido, A.; Martínez-Gutiérrez, H.; Calderon-Polania, G. A.; ...

    2016-06-07

    Nitrogen-doped multiwalled carbon nanotubes (CNx-MWNTs) have been decorated with γ-Al 2O 3 nanoparticles by a novel method. This process involved a wet chemical approach in conjunction with thermal treatment. During the particle anchoring process, individual CNx-MWNT nanotubes agglomerated into bundles, resulting in arrays of aligned CNx-MWNT coated with γ-Al 2O 3. Extensive characterization of the resulting γ-Al 2O 3/CNx-MWNT bundles was performed using a range of electron microscopy imaging and microanalytical techniques. In conclusion, a possible mechanism explaining the nanobundle alignment is described, and possible applications of these materials for the fabrication of ceramic composites using CNx-MWNTs are briefly discussed.

  17. Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

    PubMed

    Liu, Chengbin; Cao, Chenghao; Luo, Xubiao; Luo, Shenglian

    2015-03-21

    A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. A low power, area efficient fpga based beamforming technique for 1-D CMUT arrays.

    PubMed

    Joseph, Bastin; Joseph, Jose; Vanjari, Siva Rama Krishna

    2015-08-01

    A low power area efficient digital beamformer targeting low frequency (2MHz) 1-D linear Capacitive Micromachined Ultrasonic Transducer (CMUT) array is developed. While designing the beamforming logic, the symmetry of the CMUT array is well exploited to reduce the area and power consumption. The proposed method is verified in Matlab by clocking an Arbitrary Waveform Generator(AWG). The architecture is successfully implemented in Xilinx Spartan 3E FPGA kit to check its functionality. The beamforming logic is implemented for 8, 16, 32, and 64 element CMUTs targeting Application Specific Integrated Circuit (ASIC) platform at Vdd 1.62V for UMC 90nm technology. It is observed that the proposed architecture consumes significantly lesser power and area (1.2895 mW power and 47134.4 μm(2) area for a 64 element digital beamforming circuit) compared to the conventional square root based algorithm.

  19. Hierarchically self-assembled hexagonal honeycomb and kagome superlattices of binary 1D colloids.

    PubMed

    Lim, Sung-Hwan; Lee, Taehoon; Oh, Younghoon; Narayanan, Theyencheri; Sung, Bong June; Choi, Sung-Min

    2017-08-25

    Synthesis of binary nanoparticle superlattices has attracted attention for a broad spectrum of potential applications. However, this has remained challenging for one-dimensional nanoparticle systems. In this study, we investigate the packing behavior of one-dimensional nanoparticles of different diameters into a hexagonally packed cylindrical micellar system and demonstrate that binary one-dimensional nanoparticle superlattices of two different symmetries can be obtained by tuning particle diameter and mixing ratios. The hexagonal arrays of one-dimensional nanoparticles are embedded in the honeycomb lattices (for AB 2 type) or kagome lattices (for AB 3 type) of micellar cylinders. The maximization of free volume entropy is considered as the main driving force for the formation of superlattices, which is well supported by our theoretical free energy calculations. Our approach provides a route for fabricating binary one-dimensional nanoparticle superlattices and may be applicable for inorganic one-dimensional nanoparticle systems.Binary mixtures of 1D particles are rarely observed to cooperatively self-assemble into binary superlattices, as the particle types separate into phases. Here, the authors design a system that avoids phase separation, obtaining binary superlattices with different symmetries by simply tuning the particle diameter and mixture composition.

  20. [Size dependent SERS activity of gold nanoparticles studied by 3D-FDTD simulation].

    PubMed

    Li, Li-mei; Fang, Ping-ping; Yang, Zhi-lin; Huang, Wen-da; Wu, De-yin; Ren, Bin; Tian, Zhong-qun

    2009-05-01

    By synthesizing Au nanoparticles with the controllable size from about 16 to 160 nm and measuring their SERS activity, the authors found that Au nanoparticles film with a size in the range of 120-135 nm showed the highest SERS activity with the 632.8 nm excitation, which is different from previous experimental results and theoretical predictions. The three dimensional finite difference time domain (3D-FDTD)method was employed to simulate the size dependent SERS activity. At the 632.8 nm excitation, the particles with a size of 110 nm shows the highest enhancement under coupling condition and presents an enhancement as high as 10(9) at the hot site. If the enhancement is averaged over the whole surface, the enhancement can still be as high as 10(7), in good agreement with our experimental data. For Au nanoparticles with a larger size such as 220 nm, the multipolar effect leads to the appearance of the second maximum enhancement with the increase in particles size. The averaged enhancement for the excitation line of 325 nm is only 10(2).

  1. bicep2/KECK ARRAY. IV. OPTICAL CHARACTERIZATION AND PERFORMANCE OF THE bicep2 AND KECK ARRAY EXPERIMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ade, P. A. R.; Aikin, R. W.; Bock, J. J.

    2015-06-20

    bicep2 and the Keck Array are polarization-sensitive microwave telescopes that observe the cosmic microwave background (CMB) from the South Pole at degree angular scales in search of a signature of inflation imprinted as B-mode polarization in the CMB. bicep2 was deployed in late 2009, observed for three years until the end of 2012 at 150 GHz with 512 antenna-coupled transition edge sensor bolometers, and has reported a detection of B-mode polarization on degree angular scales. The Keck Array was first deployed in late 2010 and will observe through 2016 with five receivers at several frequencies (95, 150, and 220 GHz). bicep2 and the Keck Array sharemore » a common optical design and employ the field-proven bicep1 strategy of using small-aperture, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. Here we describe the optical design of both instruments and report a full characterization of the optical performance and beams of bicep2 and the Keck Array at 150 GHz.« less

  2. Wire Array Photovoltaics

    NASA Astrophysics Data System (ADS)

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction

  3. Promotion of osteoblast differentiation in 3D biomaterial micro-chip arrays comprising fibronectin-coated poly(methyl methacrylate) polycarbonate.

    PubMed

    Altmann, Brigitte; Steinberg, Thorsten; Giselbrecht, Stefan; Gottwald, Eric; Tomakidi, Pascal; Bächle-Haas, Maria; Kohal, Ralf-Joachim

    2011-12-01

    Due to the architecture of solid body tissues including bone, three-dimensional (3D) in vitro microenvironments appear favorable, since herein cell growth proceeds under more physiological conditions compared to conventional 2D systems. In the present study we show that a 3D microenvironment comprising a fibronectin-coated PMMA/PC-based micro-chip promotes differentiation of primary human osteoblasts as reflected by the densely-packed 3D bone cell aggregates and expression of biomarkers indicating osteoblast differentiation. Morphogenesis and fluorescence dye-based live/dead staining revealed homogenous cell coverage of the microcavities of the chip array, whereat cells showed high viability up to 14 days. Moreover, Azur II staining proved formation of uniform sized multilayered aggregates, exhibiting progressive intracellular deposition of extracellular bone matrix constituents comprising fibronectin, osteocalcin and osteonectin from day 7 on. Compared to 2D monolayers, osteoblasts grown in the 3D chip environment displayed differential mostly higher gene expression for osteocalcin, osteonectin, and alkaline phosphatase, while collagen type I remained fairly constant in both culture environments. Our results indicate that the 3D microenvironment, based on the PMMA biomaterial chip array promotes osteoblast differentiation, and hereby renders a promising tool for tissue-specific in vitro preconditioning of osteoblasts designated for clinically-oriented bone augmentation or regeneration. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. ISS Solar Array Management

    NASA Technical Reports Server (NTRS)

    Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

    2010-01-01

    The International Space Station (ISS) Solar Array Management (SAM) software toolset provides the capabilities necessary to operate a spacecraft with complex solar array constraints. It monitors spacecraft telemetry and provides interpretations of solar array constraint data in an intuitive manner. The toolset provides extensive situational awareness to ensure mission success by analyzing power generation needs, array motion constraints, and structural loading situations. The software suite consists of several components including samCS (constraint set selector), samShadyTimers (array shadowing timers), samWin (visualization GUI), samLock (array motion constraint computation), and samJet (attitude control system configuration selector). It provides high availability and uptime for extended and continuous mission support. It is able to support two-degrees-of-freedom (DOF) array positioning and supports up to ten simultaneous constraints with intuitive 1D and 2D decision support visualizations of constraint data. Display synchronization is enabled across a networked control center and multiple methods for constraint data interpolation are supported. Use of this software toolset increases flight safety, reduces mission support effort, optimizes solar array operation for achieving mission goals, and has run for weeks at a time without issues. The SAM toolset is currently used in ISS real-time mission operations.

  5. Analog 65/130 nm CMOS 5 GHz Sub-Arrays with ROACH-2 FPGA Beamformers for Hybrid Aperture-Array Receivers

    DTIC Science & Technology

    2017-03-20

    sub-array, which is based on all-pass filters (APFs) is realized using 130 nm CMOS technology. Approximate- discrete Fourier transform (a-DFT...fixed beams are directed at known directions [9]. The proposed approximate- discrete Fourier transform (a-DFT) based multi-beamformer [9] yields L...to digital conversion daughter board. occurs in the discrete time domain (in ROACH-2 FPGA platform) following signal digitization (see Figs. 1(d) and

  6. A Robust and Engineerable Self-Assembling Protein Template for the Synthesis and Patterning of Ordered Nanoparticle Arrays

    NASA Technical Reports Server (NTRS)

    McMillan, R. Andrew; Howard, Jeanie; Zaluzec, Nestor J.; Kagawa, Hiromi K.; Li, Yi-Fen; Paavola, Chad D.; Trent, Jonathan D.

    2004-01-01

    Self-assembling biomolecules that form highly ordered structures have attracted interest as potential alternatives to conventional lithographic processes for patterning materials. Here we introduce a general technique for patterning materials on the nanoscale using genetically modified protein cage structures called chaperonins that self-assemble into crystalline templates. Constrained chemical synthesis of transition metal nanoparticles is specific to templates genetically functionalized with poly-Histidine sequences. These arrays of materials are ordered by the nanoscale structure of the crystallized protein. This system may be easily adapted to pattern a variety of materials given the rapidly growing list of peptide sequences selected by screening for specificity for inorganic materials.

  7. Large-area, near-infrared (IR) photonic crystals with colloidal gold nanoparticles embedding.

    PubMed

    Shukla, Shobha; Baev, Alexander; Jee, Hongsub; Hu, Rui; Burzynski, Ryszard; Yoon, Yong-Kyu; Prasad, Paras N

    2010-04-01

    A polymeric composite material composed of colloidal gold nanoparticles (<10 nm) and SU8 has been utilized for the fabrication of large-area, high-definition photonic crystal. We have successfully fabricated near-infrared photonic crystal slabs from composite materials using a combination of multiple beam interference lithography and reactive ion etching processes. Doping of colloidal gold nanoparticles into the SU8 photopolymer results in a better definition of structural features and hence in the enhancement of the optical properties of the fabricated photonic crystals. A 2D air hole array of triangular symmetry with a hole-to-hole pitch of approximately 500 nm has been successfully fabricated in a large circular area of 1 cm diameter. Resonant features observed in reflectance spectra of our slabs are found to depend on the exposure time, and can be tuned over a range of near-infrared frequencies.

  8. Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring.

    PubMed

    Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Di Leandro, Luana; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

    2016-03-28

    Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the "double-faced" Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml(-1). Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and "green" routes to 3D reduced GO-metal composite materials.

  9. Cryo-electron microscopy and cryo-electron tomography of nanoparticles.

    PubMed

    Stewart, Phoebe L

    2017-03-01

    Cryo-transmission electron microscopy (cryo-TEM or cryo-EM) and cryo-electron tomography (cryo-ET) offer robust and powerful ways to visualize nanoparticles. These techniques involve imaging of the sample in a frozen-hydrated state, allowing visualization of nanoparticles essentially as they exist in solution. Cryo-TEM grid preparation can be performed with the sample in aqueous solvents or in various organic and ionic solvents. Two-dimensional (2D) cryo-TEM provides a direct way to visualize the polydispersity within a nanoparticle preparation. Fourier transforms of cryo-TEM images can confirm the structural periodicity within a sample. While measurement of specimen parameters can be performed with 2D TEM images, determination of a three-dimensional (3D) structure often facilitates more spatially accurate quantization. 3D structures can be determined in one of two ways. If the nanoparticle has a homogeneous structure, then 2D projection images of different particles can be averaged using a computational process referred to as single particle reconstruction. Alternatively, if the nanoparticle has a heterogeneous structure, then a structure can be generated by cryo-ET. This involves collecting a tilt-series of 2D projection images for a defined region of the grid, which can be used to generate a 3D tomogram. Occasionally it is advantageous to calculate both a single particle reconstruction, to reveal the regular portions of a nanoparticle structure, and a cryo-electron tomogram, to reveal the irregular features. A sampling of 2D cryo-TEM images and 3D structures are presented for protein based, DNA based, lipid based, and polymer based nanoparticles. WIREs Nanomed Nanobiotechnol 2017, 9:e1417. doi: 10.1002/wnan.1417 For further resources related to this article, please visit the WIREs website. © 2016 Wiley Periodicals, Inc.

  10. Induction of protective anti-CTL epitope responses against HER-2-positive breast cancer based on multivalent T7 phage nanoparticles.

    PubMed

    Pouyanfard, Somayeh; Bamdad, Taravat; Hashemi, Hamidreza; Bandehpour, Mojgan; Kazemi, Bahram

    2012-01-01

    We report here the development of multivalent T7 bacteriophage nanoparticles displaying an immunodominant H-2k(d)-restricted CTL epitope derived from the rat HER2/neu oncoprotein. The immunotherapeutic potential of the chimeric T7 nanoparticles as anti-cancer vaccine was investigated in BALB/c mice in an implantable breast tumor model. The results showed that T7 phage nanoparticles confer a high immunogenicity to the HER-2-derived minimal CTL epitope, as shown by inducing robust CTL responses. Furthermore, the chimeric nanoparticles protected mice against HER-2-positive tumor challenge in both prophylactic and therapeutic setting. In conclusion, these results suggest that CTL epitope-carrying T7 phage nanoparticles might be a promising approach for development of T cell epitope-based cancer vaccines.

  11. High-power, ultralow-mass solar arrays: FY-77 solar arrays technology readiness assessment report, volume 2

    NASA Technical Reports Server (NTRS)

    Costogue, E. N.; Young, L. E.; Brandhorst, H. W., Jr.

    1978-01-01

    Development efforts are reported in detail for: (1) a lightweight solar array system for solar electric propulsion; (2) a high efficiency thin silicon solar cell; (3) conceptual design of 200 W/kg solar arrays; (4) fluorocarbon encapsulation for silicon solar cell array; and (5) technology assessment of concentrator solar arrays.

  12. Photo-reduced Cu/CuO nanoclusters on TiO2 nanotube arrays as highly efficient and reusable catalyst

    NASA Astrophysics Data System (ADS)

    Jin, Zhao; Liu, Chang; Qi, Kun; Cui, Xiaoqiang

    2017-01-01

    Non-noble metal nanoparticles are becoming more and more important in catalysis recently. Cu/CuO nanoclusters on highly ordered TiO2 nanotube arrays are successfully developed by a surfactant-free photoreduction method. This non-noble metal Cu/CuO-TiO2 catalyst exhibits excellent catalytic activity and stability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with the presence of sodium borohydride (NaBH4). The rate constant of this low-cost Cu/CuO based catalyst is even higher than that of the noble metal nanoparticles decorated on the same TiO2 substrate. The conversion efficiency remains almost unchanged after 7 cycles of recycling. The recycle process of this Cu/CuO-TiO2 catalyst supported by Ti foil is very simple and convenient compared with that of the common powder catalysts. This catalyst also exhibited great catalytic activity to other organic dyes, such as methylene blue (MB), rhodamine B (RhB) and methyl orange (MO). This highly efficient, low-cost and easily reusable Cu/CuO-TiO2 catalyst is expected to be of great potential in catalysis in the future.

  13. Fiber temperature sensor with nanostructured cladding by TiO2 nanoparticles self-assembled onto a side polished optical fiber

    NASA Astrophysics Data System (ADS)

    Yang, Bing; Chen, Zhe; Wang, Yiting; Zhang, Jun; Liao, Guozhen; Tian, Zhengwen; Yu, Jianhui; Tang, Jieyuan; Luo, Yunhan; Lu, Huihui

    2015-07-01

    A temperature fiber sensor with nanostructured cladding composed ted by titanium dioxide (TiO2) nanoparticles was demonstrated. The nanoparticles self-assembled onto a side polished optical fiber (SPF). The enhancement of interaction between the propagating light and the TiO2 nanoparticles (TN) can be obtained via strong evanescent field of the SPF. The strong light-TN interaction gives rise to temperature sensing with a optical power variation of ~4dB in SPF experimentally for an environment temperature ranging from -7.8°C to 77.6°C. The novel temperature sensor shows a sensitivity of ~0.044 dB/°C. The TN-based fiber-optic temperature sensor is facile to manufactured, compatible with fiber-optic interconnections and high potential in photonics applications.

  14. Simulated and Real Sheet-of-Light 3D Object Scanning Using a-Si:H Thin Film PSD Arrays.

    PubMed

    Contreras, Javier; Tornero, Josep; Ferreira, Isabel; Martins, Rodrigo; Gomes, Luis; Fortunato, Elvira

    2015-11-30

    A MATLAB/SIMULINK software simulation model (structure and component blocks) has been constructed in order to view and analyze the potential of the PSD (Position Sensitive Detector) array concept technology before it is further expanded or developed. This simulation allows changing most of its parameters, such as the number of elements in the PSD array, the direction of vision, the viewing/scanning angle, the object rotation, translation, sample/scan/simulation time, etc. In addition, results show for the first time the possibility of scanning an object in 3D when using an a-Si:H thin film 128 PSD array sensor and hardware/software system. Moreover, this sensor technology is able to perform these scans and render 3D objects at high speeds and high resolutions when using a sheet-of-light laser within a triangulation platform. As shown by the simulation, a substantial enhancement in 3D object profile image quality and realism can be achieved by increasing the number of elements of the PSD array sensor as well as by achieving an optimal position response from the sensor since clearly the definition of the 3D object profile depends on the correct and accurate position response of each detector as well as on the size of the PSD array.

  15. Nanoparticles with tunable shape and composition fabricated by nanoimprint lithography.

    PubMed

    Alayo, Nerea; Conde-Rubio, Ana; Bausells, Joan; Borrisé, Xavier; Labarta, Amilcar; Batlle, Xavier; Pérez-Murano, Francesc

    2015-11-06

    Cone-like and empty cup-shaped nanoparticles of noble metals have been demonstrated to provide extraordinary optical properties for use as optical nanoanntenas or nanoresonators. However, their large-scale production is difficult via standard nanofabrication methods. We present a fabrication approach to achieve arrays of nanoparticles with tunable shape and composition by a combination of nanoimprint lithography, hard-mask definition and various forms of metal deposition. In particular, we have obtained arrays of empty cup-shaped Au nanoparticles showing an optical response with distinguishable features associated with the excitations of localized surface plasmons. Finally, this route avoids the most common drawbacks found in the fabrication of nanoparticles by conventional top-down methods, such as aspect ratio limitation, blurring, and low throughput, and it can be used to fabricate nanoparticles with heterogeneous composition.

  16. Designing artificial 2D crystals with site and size controlled quantum dots.

    PubMed

    Xie, Xuejun; Kang, Jiahao; Cao, Wei; Chu, Jae Hwan; Gong, Yongji; Ajayan, Pulickel M; Banerjee, Kaustav

    2017-08-30

    Ordered arrays of quantum dots in two-dimensional (2D) materials would make promising optical materials, but their assembly could prove challenging. Here we demonstrate a scalable, site and size controlled fabrication of quantum dots in monolayer molybdenum disulfide (MoS 2 ), and quantum dot arrays with nanometer-scale spatial density by focused electron beam irradiation induced local 2H to 1T phase change in MoS 2 . By designing the quantum dots in a 2D superlattice, we show that new energy bands form where the new band gap can be controlled by the size and pitch of the quantum dots in the superlattice. The band gap can be tuned from 1.81 eV to 1.42 eV without loss of its photoluminescence performance, which provides new directions for fabricating lasers with designed wavelengths. Our work constitutes a photoresist-free, top-down method to create large-area quantum dot arrays with nanometer-scale spatial density that allow the quantum dots to interfere with each other and create artificial crystals. This technique opens up new pathways for fabricating light emitting devices with 2D materials at desired wavelengths. This demonstration can also enable the assembly of large scale quantum information systems and open up new avenues for the design of artificial 2D materials.

  17. Nanoparticles of Poly(Lactide-Co-Glycolide)-d-a-Tocopheryl Polyethylene Glycol 1000 Succinate Random Copolymer for Cancer Treatment

    NASA Astrophysics Data System (ADS)

    Ma, Yuandong; Zheng, Yi; Liu, Kexin; Tian, Ge; Tian, Yan; Xu, Lei; Yan, Fei; Huang, Laiqiang; Mei, Lin

    2010-07-01

    Cancer is the leading cause of death worldwide. Nanomaterials and nanotechnologies could provide potential solutions. In this research, a novel biodegradable poly(lactide-co-glycolide)-d-a-tocopheryl polyethylene glycol 1000 succinate (PLGA-TPGS) random copolymer was synthesized from lactide, glycolide and d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) by ring-opening polymerization using stannous octoate as catalyst. The obtained random copolymers were characterized by 1H NMR, FTIR, GPC and TGA. The docetaxel-loaded nanoparticles made of PLGA-TPGS copolymer were prepared by a modified solvent extraction/evaporation method. The nanoparticles were then characterized by various state-of-the-art techniques. The results revealed that the size of PLGA-TPGS nanoparticles was around 250 nm. The docetaxel-loaded PLGA-TPGS nanoparticles could achieve much faster drug release in comparison with PLGA nanoparticles. In vitro cellular uptakes of such nanoparticles were investigated by CLSM, demonstrating the fluorescence PLGA-TPGS nanoparticles could be internalized by human cervix carcinoma cells (HeLa). The results also indicated that PLGA-TPGS-based nanoparticles were biocompatible, and the docetaxel-loaded PLGA-TPGS nanoparticles had significant cytotoxicity against Hela cells. The cytotoxicity against HeLa cells for PLGA-TPGS nanoparticles was in time- and concentration-dependent manner. In conclusion, PLGA-TPGS random copolymer could be acted as a novel and promising biocompatible polymeric matrix material applicable to nanoparticle-based drug delivery system for cancer chemotherapy.

  18. Plasmonic Resonances for Spectroscopy Applications using 3D Finite-Difference Time-Domain Models

    NASA Astrophysics Data System (ADS)

    Ravi, Aruna

    Tuning plasmonic extinction resonances of sub-wavelength scale structures is essential to achieve maximum sensitivity and accuracy. These resonances can be controlled with careful design of nanoparticle geometries and incident wave attributes. In the first part of this dissertation, plasmonically enhanced effects on hexagonal-arrays of metal nanoparticles, metal-hole arrays (micro-mesh), and linear-arrays of metal nanorings are analyzed using three-dimensional Finite-Difference Time-Domain (3D-FDTD) simulations. The effect of particle size, lattice spacing, and lack of monodispersity of a self-assembled, hexagonal array layer of silver (Ag) nanoparticles on the extinction resonance is investigated to help determine optimal design specifications for efficient organic solar power harvesting. The enhancement of transmission resonances using plasmonic thin metal films with arrays of holes which enable recording of scatter-free infrared (IR) transmission spectra of individual particles is also explored. This method is quantitative, non-destructive and helps in better understanding the interaction of light with sub-wavelength particles. Next, plasmonically enhanced effects on linear arrays of gold (Au) rings are studied. Simulations employing 3D-FDTD can be used to determine the set of geometrical parameters to attain localized surface plasmon resonance (LSPR). The shifts in resonances due to changes in the effective dielectric of the structure are investigated, which is useful in sensing applications. Computational models enrich experimental studies. In the second part of this dissertation, the effect of particle size, shape and orientation on the IR spectra is investigated using 3D-FDTD and Mie-Bruggeman models. This computational analysis is extended to include clusters of particles of mixed composition. The prediction of extinction and absorption spectra of single particles of mixed composition helps in interpreting their physical properties and predict chemical

  19. 3D Dewetting for Crystal Patterning: Toward Regular Single-Crystalline Belt Arrays and Their Functionality.

    PubMed

    Wu, Yuchen; Feng, Jiangang; Su, Bin; Jiang, Lei

    2016-03-16

    Arrays of unidirectional dewetting behaviors can be generated by using 3D-wettability-difference micropillars, yielding highly ordered organic single-crystalline belt arrays. These patterned organic belts show an improved mobility record and can be used as flexible pressure sensors with high sensitivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Magnetic field directed assembly of superstructures of ferrite-ferroelectric core-shell nanoparticles and studies on magneto-electric interactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Srinivasan, G., E-mail: srinivas@oakland.edu; Sreenivasulu, G.; Benoit, Crystal

    2015-05-07

    Composites of ferromagnetic and ferroelectric are of interest for studies on mechanical strain mediated magneto-electric (ME) interactions and for useful technologies. Here, we report on magnetic-field-assisted-assembly of barium titanate (BTO)-nickel ferrite (NFO) core-shell particles into linear chains and 2D/3D arrays and measurements of ME effects in such assemblies. First, we synthesized the core-shell nano-particles with 50–600 nm BTO and 10–200 nm NFO by chemical self-assembly by coating the ferroic particles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst via the “click” reaction. The core-shell structure was confirmed with electron microscopy and scanning probe microscopy. Wemore » obtained superstructure of the core-shell particles by subjecting them to a magnetic field gradient that exerts an attractive force on the particles and align them toward the regions of high field strengths. At low particle concentration, linear chains were formed and they evolved into 2D and 3D arrays at high particle concentrations. Magnetoelectric characterization on unassembled films and assembled arrays has been performed through measurements of low-frequency ME voltage coefficient (MEVC) by subjecting the sample to a bias magnetic field and an ac magnetic field. The MEVC is higher for field-assembled samples than for unassembled films and is found to be sensitive to field orientation with a higher MEVC for magnetic fields parallel to the array direction than for magnetic fields perpendicular to the array. A maximum MEVC of 20 mV/cm Oe, one of the highest reported for any bulk nanocomposite, is measured across the array thickness. A model is provided for ME coupling in the superstructures of BTO-NFO particulate composites. First, we estimated the MEVC for a free-standing BTO-NFO core-shell particle and then extended the model to include an array of linear chains of the particles. The theoretical estimates