Understanding the influence of surface chemical states on the dielectric tunability of sputtered Ba0.5Sr0.5TiO3 thin films

NASA Astrophysics Data System (ADS)

Venkata Saravanan, K.; Raju, K. C. James

2014-03-01

The surface chemical states of RF-magnetron sputtered Ba0.5Sr0.5TiO3 (BST5) thin films deposited at different oxygen mixing percentage (OMP) was examined by x-ray photoelectron spectroscopy. The O1s XPS spectra indicate the existence of three kinds of oxygen species (dissociated oxygen ion O2 -, adsorbed oxide ion O- and lattice oxide ion O2-) on the films’ surface, which strongly depends on OMP. The presence of oxygen species other than lattice oxygen ion makes the films’ surface highly reactivity to atmospheric gases, resulting in the formation of undesired surface layers. The XPS results confirm the formation of surface nitrates for the films deposited under oxygen deficient atmosphere (OMP ≦̸ 25%), whereas the films deposited in oxygen rich atmosphere (OMP ≧̸ 75%) show the presence of metal-hydroxide. The influence of a surface dead layer on the tunable dielectric properties of BST5 films have been studied in detail and are reported. Furthermore, our observations indicate that an optimum ratio of Ar:O2 is essential for achieving desired material and dielectric properties in BST5 thin films. The films deposited at 50% OMP have the highest dielectric tunability of ~65% (@280 kV cm-1), with good ɛ r-E curve symmetry of 98% and low tan δ of 0.018. The figure of merit for these films is about 35, which is promising for frequency agile device applications.

Tunable dielectric properties of Barium Magnesium Niobate (BMN) doped Barium Strontium Titanate (BST) thin films by magnetron sputtering

NASA Astrophysics Data System (ADS)

Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin

2013-03-01

We report on the tunable dielectric properties of Mg and Nb co-doped Ba0.45Sr0.55TiO3 (BST) thin film prepared by the magnetron sputtering using BST target (pure and doped with BaMg0.33Nb0.67O3 (BMN)) on Pt/TiO2/SiO2/Al2O3 4'' wafers at 700 °C under oxygen atmosphere. The electrical measurements are conducted on 2432 metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The crystalline structure, microstructure, and surface morphology of the films are analyzed and correlated to the films dielectric properties. The BMN doped and undoped BST films have shown tunabilities of 48% and 52%; and leakage current densities of 2.2x10-6 A/cm2 and 3.7x10-5 A/cm2, respectively at 0.5 MV/cm bias field. The results indicate that the BMN doped film exhibits a lower leakage current with no significant decrease in tunability. Due to similar electronegativity and ionic radii, it was suggested that both Mg2+ (accepter-type) and Nb5+ (donor-type) dopants substitutTi4+ ion in BST. The improvement in the film dielectric losses and leakage current with insignificant loss of tunability is attributed to the adversary effects of Mg2+ and Nb5+ in BST.

Strain engineered barium strontium titanate for tunable thin film resonators

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

Khassaf, H.; Khakpash, N.; Sun, F.

2014-05-19

Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

Tunable random lasing behavior in plasmonic nanostructures

NASA Astrophysics Data System (ADS)

Yadav, Ashish; Zhong, Liubiao; Sun, Jun; Jiang, Lin; Cheng, Gary J.; Chi, Lifeng

2017-01-01

Random lasing is desired in plasmonics nanostructures through surface plasmon amplification. In this study, tunable random lasing behavior was observed in dye molecules attached with Au nanorods (NRs), Au nanoparticles (NPs) and Au@Ag nanorods (NRs) respectively. Our experimental investigations showed that all nanostructures i.e., Au@AgNRs, AuNRs & AuNPs have intensive tunable spectral effects. The random lasing has been observed at excitation wavelength 532 nm and varying pump powers. The best random lasing properties were noticed in Au@AgNRs structure, which exhibits broad absorption spectrum, sufficiently overlapping with that of dye Rhodamine B (RhB). Au@AgNRs significantly enhance the tunable spectral behavior through localized electromagnetic field and scattering. The random lasing in Au@AgNRs provides an efficient coherent feedback for random lasers.

Study of Chemistry and Structure-Property Relationship on Tunable Plasmonic Nanostructures

NASA Astrophysics Data System (ADS)

Jing, Hao

In this dissertation, the rational design and controllable fabrication of an array of novel plasmonic nanostructures with geometrically tunable optical properties are demonstrated, including metal-semiconductor hybrid hetero-nanoparticles, bimetallic noble metal nanoparticles and hollow nanostructures (nanobox and nanocage). Firstly, I have developed a robust wet chemistry approach to the geometry control of Ag-Cu2O core-shell nanoparticles through epitaxial growth of Cu2O nanoshells on the surfaces of various Ag nanostructures, such as quasi-spherical nanoparticles, nanocubes, and nanocuboids. Precise control over the core and the shell geometries enables me to develop detailed, quantitative understanding of how the Cu2O nanoshells introduce interesting modifications to the resonance frequencies and the extinction spectral line shapes of multiple plasmon modes of the Ag cores. Secondly, I present a detailed and systematic study of the controlled overgrowth of Pd on Au nanorods. The overgrowth of Pd nanoshells with fine-controlled dimensions and architectures on single-crystalline Au nanorods through seed-mediated growth protocol in the presence of various surfactants is investigated. Thirdly, I have demonstrated that creation of high-index facets on subwavelength metallic nanoparticles provides a unique approach to the integration of desired plasmonic and catalytic properties on the same nanoparticle. Through site-selective surface etching of metallic nanocuboids whose surfaces are dominated by low-index facets, I have controllably fabricated nanorice and nanodumbbell particles, which exhibit drastically enhanced catalytic activities arising from the catalytically active high index facets abundant on the particle surfaces. And the nanorice and nanodumbbell particles also possess appealing tunable plasmonic properties that allow us to gain quantitative insights into nanoparticle-catalyzed reactions with unprecedented sensitivity and detail through time-resolved plasmon-enhanced spectroscopic measurements, such as surface-enhanced Raman scattering (SERS). Last but not least, I have demonstrated that the capability of geometry control over Ag-Pd bimetallic hollow nanostructures through nanoscale galvanic replacement can be greatly enhanced by the use of appropriate mild reducing agents, such as ascorbic acid and formaldehyde. With the aid of mild reducing agents, we have been able to fine-tailor the compositions, interior architectures, and surface morphologies of Ag-Pd bimetallic hollow nanoparticles with increased structural complexity through surface ligand-free galvanic replacement processes at room temperature. This reducing agent-mediated galvanic replacement provides a unique way of achieving both enhanced optical tunability and optimized catalytic activities through deliberate control over the geometries of complex Ag-Pd bimetallic nanoparticles.

Self-assembled tunable networks of sticky colloidal particles

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

Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim

Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

Tunable antireflection from conformal Al-doped ZnO films on nanofaceted Si templates

PubMed Central

2014-01-01

Photon harvesting by reducing reflection loss is the basis of photovoltaic devices. Here, we show the efficacy of Al-doped ZnO (AZO) overlayer on ion beam-synthesized nanofaceted silicon for suppressing reflection loss. In particular, we demonstrate thickness-dependent tunable antireflection (AR) from conformally grown AZO layer, showing a systematic shift in the reflection minima from ultraviolet to visible to near-infrared ranges with increasing thickness. Tunable AR property is understood in light of depth-dependent refractive index of nanofaceted silicon and AZO overlayer. This improved AR property significantly increases the fill factor of such textured heterostructures, which reaches its maximum for 60-nm AZO compared to the ones based on planar silicon. This thickness matches with the one that shows the maximum reduction in surface reflectance. PACS 81.07.-b; 42.79.Wc; 81.16.Rf; 81.15.Cd PMID:24808799

Simulation, fabrication, and characterization of a tunable electrowetting-based lens with a wedge-shaped PDMS dielectric layer.

PubMed

Moghaddam, Mohammadreza Salehi; Latifi, H; Shahraki, Hamidreza; Cheri, Mohammad Sadegh

2015-04-01

Microlenses with tunable focal length have wide applications in optofluidic devices. This work presents a numerical and experimental investigation on a tunable electrowetting-based concave lens. Optical properties such as focal length of the lens and visibility of images were investigated numerically and experimentally. A finite element analysis and a ZEMAX simulation were used for determination of surface profile and focal length of the lens. The results show that the theoretical surface profile and focal length of the lens are in good agreement with the experimental ones. The lens has a wide tuning focal length equal to 6.5 (cm). Because the polydimethylsiloxane (PDMS) layer is wedge shaped (as both the dielectric and hydrophobic layers), lower applied voltage is needed. A commercial program was used to find the focal length of the lens from maximum visibility value by tuning the applied voltage.

Experimental validation of tunable features in laser-induced plasma resonators

NASA Astrophysics Data System (ADS)

Colón Quiñones, Roberto A.; Cappelli, Mark A.

2017-08-01

Measurements are presented which examine the use of gaseous plasma elements as highly-tunable resonators. The resonator considered here is a laser-induced plasma kernel generated by focusing the fundamental output from a Q-switched Nd:YAG laser through a lens and into a gas at constant pressure. The near-ellipsoidal plasma element interacts with incoming microwave radiation through excitation of low-order, electric-dipole resonances similar to those seen in metallic spheres. The tunability of these elements stems from the dispersive nature of plasmas arising from their variable electron density, electron momentum transfer collision frequency, and the concomitant e↵ect of these properties on the excited surface plasmon resonance. Experiments were carried out in the Ku band of the microwave spectrum to characterize the scattering properties of these resonators for di↵erent values of electron density. The experimental results are compared with results from theoretical approximations and finite element method electromagnetic simulations. The described tunable resonators have the potential to be used as the building blocks in a new class of all-plasma metamaterials with fully three-dimensional structural flexibility.

Two-step fabrication of ZnO-PVP composites with tunable visible emissions

NASA Astrophysics Data System (ADS)

Agulto, Verdad C.; Empizo, Melvin John F.; Kawano, Keisuke; Minami, Yuki; Yamanoi, Kohei; Sarukura, Nobuhiko; Yago, Allan Christopher C.; Sarmago, Roland V.

2018-02-01

We report a two-step fabrication of zinc oxide-polyvinylpyrrolidone (ZnO-PVP) composites for potential phosphor-based applications. The composites are fabricated by initially preparing ZnO microrods using hydrothermal growth method and then dip-coating the microrods into aqueous PVP solutions with varying molar concentrations. The as-prepared ZnO microrods exhibit smooth surfaces and broad visible emissions, while the ZnO-PVP composites have pitted surfaces with shifted and reduced visible emissions. These changes in the structural and optical properties, which are found to depend on the PVP concentration, are attributed to the adsorption of PVP on the microrod surface. Although the surface morphology and visible emission are modified by PVP, the composites still maintain a hexagonal wurtzite crystal structure and near-band-edge ultraviolet (UV) emission similar with the as-prepared microrods. Our results therefore suggest that the ZnO-PVP composites can be used as phosphors that offer not only properties found in both ZnO and PVP but also tunable visible emissions which can be controlled during material fabrication.

Electrowetting Controlled Tunable Liquid Microlens

NASA Astrophysics Data System (ADS)

Krupenkin, Tom; Yang, Shu

2002-03-01

Electrowetting potentially provides a convenient way to control the shape and position of the liquid droplet on a rigid substrate. However, the effectiveness of this method relies strongly on the precise control of the surface properties of the substrate. Here we present a tunable liquid microlens capable of adjusting the position of its focal spot in all three dimensions. The microlens consists of a droplet of a transparent conductive liquid placed on a dielectric substrate with a hydrophobic coating. By varying the voltage applied to the structure, both the position and the curvature of the microlens can be changed. The influence of the bulk and surface properties of the materials on the microlens behavior is experimentally investigated and supported by theoretical calculations. Some of the potential problems associated with the stick-slip behavior and contact angle hysteresis are outlined and possible ways to prevent them are suggested.

Multifunctional mussel-inspired copolymerized epigallocatechin gallate (EGCG)/arginine coating: the potential as an ad-layer for vascular materials.

PubMed

Luo, Rifang; Tang, Linlin; Xie, Lingxia; Wang, Jin; Huang, Nan; Wang, Yunbing

2016-12-01

Surface properties are considered to be important factors in addressing proper functionalities. In this paper, a multifunctional mussel-inspired coating was prepared via the direct copolymerization of epigallocatechin gallate (EGCG) and arginine. The coating formation was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectra. The EGCG/arginine coating contained diverse functional groups like amines, phenols and carboxyls, whose densities were also tunable. Such mussel-inspired coating could also be applied as an ad-layer for its secondary reactivity, demonstrated by quartz crystal microbalance technique. Moreover, the tunable surface density of phenols showed potential ability in modulating endothelial cell and smooth muscle cell viability. The coatings rich in phenols presented excellent free radical scavenging property. Current results strongly indicated the potential of EGCG/arginine coatings to be applied as an ad-layer for vascular materials.

Gold Nanoparticles with Externally Controlled, Reversible Shifts of Local Surface Plasmon Resonance Bands

PubMed Central

Yavuz, Mustafa S.; Jensen, Gary C.; Penaloza, David P.; Seery, Thomas A. P.; Pendergraph, Samuel A.; Rusling, James F.; Sotzing, Gregory A.

2010-01-01

We have achieved reversible tunability of local surface plasmon resonance in conjugated polymer functionalized gold nanoparticles. This property was facilitated by the preparation of 3,4-ethylenedioxythiophene (EDOT) containing polynorbornene brushes on gold nanoparticles via surface-initiated ring-opening metathesis polymerization. Reversible tuning of the surface plasmon band was achieved by electrochemically switching the EDOT polymer between its reduced and oxidized states. PMID:19839619

Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator

DOE PAGES

Neupane, Madhab; Xu, Su-Yang; Sankar, R.; ...

2015-08-20

Here we report the evolution of the surface electronic structure and surface material properties of a topological crystalline insulator (TCI), Pb 1more » $${-}$$xSnxSe, as a function of various material parameters including composition x, temperature T , and crystal structure. Our spectroscopic data demonstrate the electronic ground-state condition for the saddle point singularity, the tunability of surface chemical potential, and the surface states’ response to circularly polarized light. Our results show that each material parameter can tune the system between the trivial and topological phase in a distinct way, unlike that seen in Bi 2Se 3 and related compounds, leading to a rich topological phase diagram. Our systematic studies of the TCI Pb 1$${-}$$xSnxSe are a valuable materials guide to realize new topological phenomena.« less

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors.

PubMed

Byun, Hye-Ran; You, Eun-Ah; Ha, Young-Geun

2017-03-01

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm 2 ), insulating property (leakage current densities <10 -7 A/cm 2 ), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Preface: special topic on supramolecular self-assembly at surfaces.

PubMed

Bartels, Ludwig; Ernst, Karl-Heinz; Gao, Hong-Jun; Thiel, Patricia A

2015-03-14

Supramolecular self-assembly at surfaces is one of the most exciting and active fields in Surface Science today. Applications can take advantage of two key properties: (i) versatile pattern formation over a broad length scale and (ii) tunability of electronic structure and transport properties, as well as frontier orbital alignment. It provides a new frontier for Chemical Physics as it uniquely combines the versatility of Organic Synthesis and the Physics of Interfaces. The Journal of Chemical Physics is pleased to publish this Special Topic Issue, showcasing recent advances and new directions.

Development of Polydimethylsiloxane Substrates with Tunable Elastic Modulus to Study Cell Mechanobiology in Muscle and Nerve

PubMed Central

Palchesko, Rachelle N.; Zhang, Ling; Sun, Yan; Feinberg, Adam W.

2012-01-01

Mechanics is an important component in the regulation of cell shape, proliferation, migration and differentiation during normal homeostasis and disease states. Biomaterials that match the elastic modulus of soft tissues have been effective for studying this cell mechanobiology, but improvements are needed in order to investigate a wider range of physicochemical properties in a controlled manner. We hypothesized that polydimethylsiloxane (PDMS) blends could be used as the basis of a tunable system where the elastic modulus could be adjusted to match most types of soft tissue. To test this we formulated blends of two commercially available PDMS types, Sylgard 527 and Sylgard 184, which enabled us to fabricate substrates with an elastic modulus anywhere from 5 kPa up to 1.72 MPa. This is a three order-of-magnitude range of tunability, exceeding what is possible with other hydrogel and PDMS systems. Uniquely, the elastic modulus can be controlled independently of other materials properties including surface roughness, surface energy and the ability to functionalize the surface by protein adsorption and microcontact printing. For biological validation, PC12 (neuronal inducible-pheochromocytoma cell line) and C2C12 (muscle cell line) were used to demonstrate that these PDMS formulations support cell attachment and growth and that these substrates can be used to probe the mechanosensitivity of various cellular processes including neurite extension and muscle differentiation. PMID:23240031

Tunable Luminescent Carbon Nanospheres with Well-Defined Nanoscale Chemistry for Synchronized Imaging and Therapy.

PubMed

Mukherjee, Prabuddha; Misra, Santosh K; Gryka, Mark C; Chang, Huei-Huei; Tiwari, Saumya; Wilson, William L; Scott, John W; Bhargava, Rohit; Pan, Dipanjan

2015-09-01

In this work, we demonstrate the significance of defined surface chemistry in synthesizing luminescent carbon nanomaterials (LCN) with the capability to perform dual functions (i.e., diagnostic imaging and therapy). The surface chemistry of LCN has been tailored to achieve two different varieties: one that has a thermoresponsive polymer and aids in the controlled delivery of drugs, and the other that has fluorescence emission both in the visible and near-infrared (NIR) region and can be explored for advanced diagnostic modes. Although these particles are synthesized using simple, yet scalable hydrothermal methods, they exhibit remarkable stability, photoluminescence and biocompatibility. The photoluminescence properties of these materials are tunable through careful choice of surface-passivating agents and can be exploited for both visible and NIR imaging. Here the synthetic strategy demonstrates the possibility to incorporate a potent antimetastatic agent for inhibiting melanomas in vitro. Since both particles are Raman active, their dispersion on skin surface is reported with Raman imaging and utilizing photoluminescence, their depth penetration is analysed using fluorescence 3D imaging. Our results indicate a new generation of tunable carbon-based probes for diagnosis, therapy or both. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Bartels, Ludwig; Ernst, Karl-Heinz; Gao, Hong-Jun

Supramolecular self-assembly at surfaces is one of the most exciting and active fields in Surface Science today. Applications can take advantage of two key properties: (i) versatile pattern formation over a broad length scale and (ii) tunability of electronic structure and transport properties, as well as frontier orbital alignment. It provides a new frontier for Chemical Physics as it uniquely combines the versatility of Organic Synthesis and the Physics of Interfaces. The Journal of Chemical Physics is pleased to publish this Special Topic Issue, showcasing recent advances and new directions.

Development of a portable petroleum by-products chemical sensor : phase III and IV.

DOT National Transportation Integrated Search

2009-08-21

Semiconductor quantum dots (QDs) are considered to have potential for chemical sensing application : because of their high surface to volume ratio and unique size tunable properties like : photoluminescence (PL). However, our study revealed for the f...

Multimodal transmission property in a liquid-filled photonic crystal fiber

NASA Astrophysics Data System (ADS)

Lin, Wei; Miao, Yinping; Song, Binbin; Zhang, Hao; Liu, Bo; Liu, Yange; Yan, Donglin

2015-02-01

The multimode interference (MMI) effect in a liquid-filled photonic crystal fiber (PCF) has been experimentally demonstrated by fully infiltrating the air-hole cladding of a solid-core PCF with the refractive index (RI) matching liquid whose RI is close to the silica background. Due to the weak mode confinement capability of the cladding region, several high-order modes are excited to establish the multimode interference effect. The multimode interferometer shows a good temperature tunability of 12.30 nm/K, which makes it a good candidate for a highly tunable optical filtering as well as temperature sensing applications. Furthermore, this MMI effect would have great promise in various applications such as highly sensitive multi-parameter sensing, tunable optically filtering, and surface-enhanced Raman scattering.

Reconfigurable all-dielectric metasurface based on tunable chemical systems in aqueous solution.

PubMed

Yang, Xiaoqing; Zhang, Di; Wu, Shiyue; Yin, Yang; Li, Lanshuo; Cao, Kaiyuan; Huang, Kama

2017-06-09

Dynamic control transmission and polarization properties of electromagnetic (EM) wave propagation is investigated using chemical reconfigurable all-dielectric metasurface. The metasurface is composed of cross-shaped periodical teflon tubes and inner filled chemical systems (i.e., mixtures and chemical reaction) in aqueous solution. By tuning the complex permittivity of chemical systems, the reconfigurable metasurface can be easily achieved. The transmission properties of different incident polarized waves (i.e., linear and circular polarization) were simulated and experimentally measured for static ethanol solution as volume ratio changed. Both results indicated this metasurface can serve as either tunable FSS (Frequency Selective Surface) or tunable linear-to-circular/cross Polarization Converter at required frequency range. Based on the reconfigurable laws obtained from static solutions, we developed a dynamic dielectric system and researched a typical chemical reaction with time-varying permittivity filled in the tubes experimentally. It provides new ways for realizing automatic reconfiguration of metasurface by chemical reaction system with given variation laws of permittivity.

Topologically-protected one-way leaky waves in nonreciprocal plasmonic structures

NASA Astrophysics Data System (ADS)

Hassani Gangaraj, S. Ali; Monticone, Francesco

2018-03-01

We investigate topologically-protected unidirectional leaky waves on magnetized plasmonic structures acting as homogeneous photonic topological insulators. Our theoretical analyses and numerical experiments aim at unveiling the general properties of these exotic surface waves, and their nonreciprocal and topological nature. In particular, we study the behavior of topological leaky modes in stratified structures composed of a magnetized plasma at the interface with isotropic conventional media, and we show how to engineer their propagation and radiation properties, leading to topologically-protected backscattering-immune wave propagation, and highly directive and tunable radiation. Taking advantage of the non-trivial topological properties of these leaky modes, we also theoretically demonstrate advanced functionalities, including arbitrary re-routing of leaky waves on the surface of bodies with complex shapes, as well as the realization of topological leaky-wave (nano)antennas with isolated channels of radiation that are completely independent and separately tunable. Our findings help shedding light on the behavior of topologically-protected modes in open wave-guiding structures, and may open intriguing directions for future antenna generations based on topological structures, at microwaves and optical frequencies.

Photocrosslinked Tyramine-Substituted Hyaluronate Hydrogels with Tunable Mechanical Properties Improve Immediate Tissue‐Hydrogel Interfacial Strength in Articular Cartilage

PubMed Central

Donnelly, Patrick E.; Chen, Tony; Finch, Anthony; Brial, Caroline; Maher, Suzanne A.; Torzilli, Peter A.

2017-01-01

Articular cartilage lacks the ability to self-repair and a permanent solution for cartilage repair remains elusive. Hydrogel implantation is a promising technique for cartilage repair; however for the technique to be successful hydrogels must interface with the surrounding tissue. The objective of this study was to investigate the tunability of mechanical properties in a hydrogel system using a phenol-substituted polymer, tyramine-substituted hyaluronate (TA-HA), and to determine if the hydrogels could form an interface with cartilage. We hypothesized that tyramine moieties on hyaluronate could crosslink to aromatic amino acids in the cartilage extracellular matrix. Ultraviolet (UV) light and a riboflavin photosensitizer were used to create a hydrogel by tyramine self‐crosslinking. The gel mechanical properties were tuned by varying riboflavin concentration, TA-HA concentration, and UV exposure time. Hydrogels formed with a minimum of 2.5 min of UV exposure. The compressive modulus varied from 5–16 kPa. Fluorescence spectroscopy analysis found differences in dityramine content. Cyanine-3 labelled tyramide reactivity at the surface of cartilage was dependent on the presence of riboflavin and UV exposure time. Hydrogels fabricated within articular cartilage defects had increasing peak interfacial shear stress at the cartilage-hydrogel interface with increasing UV exposure time, reaching a maximum shear stress 3.5× greater than a press‐fit control. Our results found that phenol-substituted polymer/riboflavin systems can be used to fabricate hydrogels with tunable mechanical properties and can interface with the surface tissue, such as articular cartilage. PMID:28134036

PEG-nanotube liquid crystals as templates for construction of surfactant-free gold nanorods.

PubMed

Kameta, Naohiro; Shiroishi, Hidenobu

2018-05-03

Lyotropic liquid crystals, in which nanotubes coated with polyethylene glycol were aligned side-by-side in aqueous dispersions, acted as templates for the construction of surfactant-free gold nanorods with controllable diameters, functionalizable surfaces, and tunable optical properties.

Tunable dichroic polarization beam splitter created by one-step holographic photoalignment using four-beam polarization interferometry

NASA Astrophysics Data System (ADS)

Kawai, Kotaro; Sakamoto, Moritsugu; Noda, Kohei; Sasaki, Tomoyuki; Kawatsuki, Nobuhiro; Ono, Hiroshi

2017-01-01

A tunable dichroic polarization beam splitter (tunable DPBS) simultaneously performs the follow functions: 1. Separation of a polarized incident beam into multiple pairs of orthogonally polarized beams; 2. Separation of the propagation direction of two wavelength incident beams after passing through the tunable DPBS; and 3. Control of both advanced polarization and wavelength separation capabilities by varying the temperature of the tunable DPBS. This novel complex optical property is realized by diffraction phenomena using a designed three-dimensional periodic structure of aligned liquid crystals in the tunable DPBS, which was fabricated quickly with precision in a one-step photoalignment using four-beam polarization interferometry. In experiments, we demonstrated that these diffraction properties are obtained by entering polarized beams of wavelengths 532 nm and 633 nm onto the tunable DPBS. These diffraction properties are described using the Jones calculus in a polarization propagation analysis. Of significance is that the aligned liquid crystal structure needed to obtain these diffraction properties was proposed based on a theoretical analysis, and these properties were then demonstrated experimentally. The tunable DPBS can perform several functions of a number of optical elements such as wave plates, polarization beam splitter, dichroic beam splitter, and tunable wavelength filter. Therefore, the tunable DPBS can contribute to greater miniaturization, sophistication, and cost reduction of optical systems used widely in applications, such as optical measurements, communications, and information processing.

Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding.

PubMed

Mi, Hao-Yang; Salick, Max R; Jing, Xin; Jacques, Brianna R; Crone, Wendy C; Peng, Xiang-Fang; Turng, Lih-Sheng

2013-12-01

Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold's microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications. © 2013.

Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding

PubMed Central

Mi, Hao-Yang; Salick, Max R.; Jing, Xin; Jacques, Brianna R.; Crone, Wendy C.; Peng, Xiang-Fang; Turng, Lih-Sheng

2015-01-01

Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold’s microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications. PMID:24094186

Biocompatible Surface Chemistry Manipulation of Gold Nanorods Preserves Optical Properties for Bio-Imaging Applications

DTIC Science & Technology

2015-12-18

3. DATES COVERED (From - To) March 2014 – Sept 2014 4. TITLE AND SUBTITLE Biocompatible surface chemistry manipulation of gold nanorods preserves...Due to their anisotropic shape, gold nanorods (GNRs) possess a number of advantages for biosystem use including, enhanced surface area and tunable...intracellular aggregation of MTAB-TA GNRs, and identify them as prime andidates for use in nanobased bio-imaging applications. 15. SUBJECT TERMS Gold

Tunable Band Alignment with Unperturbed Carrier Mobility of On-Surface Synthesized Organic Semiconducting Wires

PubMed Central

2016-01-01

The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursors, the product’s energy level alignment can be tuned without compromising the charge carrier’s mobility. PMID:26841052

Localized surface plasmon resonance properties of symmetry-broken Au-ITO-Ag multilayered nanoshells

NASA Astrophysics Data System (ADS)

Lv, Jingwei; Mu, Haiwei; Lu, Xili; Liu, Qiang; Liu, Chao; Sun, Tao; Chu, Paul K.

2018-06-01

The plasmonic properties of symmetry-broken Au-ITO-Ag multilayered nanoshells by shell cutting are studied by the finite element method. The influence of the polarization of incident light and geometrical parameters on the plasmon resonances of the multilayered nanoshells are investigated. The polarization-dependent multiple plasmon resonances appear from the multilayered nanoshells due to symmetry breaking. In nanostructures with a broken symmetry, the localized surface plasmon resonance modes are enhanced resulting in higher order resonances. According to the plasmon hybridization theory, these resonance modes and greater spectral tunability derive from the interactions of an admixture of both primitive and multipolar modes between the inner Au core and outer Ag shell. By changing the radius of the Au core, the extinction resonance modes of the multilayered nanoshells can be easily tuned to the near-infrared region. To elucidate the symmetry-broken effects of multilayered nanoshells, we link the geometrical asymmetry to the asymmetrical distributions of surface charges and demonstrate dipolar and higher order plasmon modes with large associated field enhancements at the edge of the Ag rim. The spectral tunability of the multiple resonance modes from visible to near-infrared is investigated and the unique properties are attractive to applications including angularly selective filtering to biosensing.

Controlling Properties and Cytotoxicity of Chitosan Nanocapsules by Chemical Grafting

PubMed Central

De Matteis, Laura; Alleva, Maria; Serrano-Sevilla, Inés; García-Embid, Sonia; Stepien, Grazyna; Moros, María; de la Fuente, Jesús M.

2016-01-01

The tunability of the properties of chitosan-based carriers opens new ways for the application of drugs with low water-stability or high adverse effects. In this work, the combination of a nanoemulsion with a chitosan hydrogel coating and the following poly (ethylene glycol) (PEG) grafting is proven to be a promising strategy to obtain a flexible and versatile nanocarrier with an improved stability. Thanks to chitosan amino groups, a new easy and reproducible method to obtain nanocapsule grafting with PEG has been developed in this work, allowing a very good control and tunability of the properties of nanocapsule surface. Two different PEG densities of coverage are studied and the nanocapsule systems obtained are characterized at all steps of the optimization in terms of diameter, Z potential and surface charge (amino group analysis). Results obtained are compatible with a conformation of PEG molecules laying adsorbed on nanoparticle surface after covalent linking through their amino terminal moiety. An improvement in nanocapsule stability in physiological medium is observed with the highest PEG coverage density obtained. Cytotoxicity tests also demonstrate that grafting with PEG is an effective strategy to modulate the cytotoxicity of developed nanocapsules. Such results indicate the suitability of chitosan as protective coating for future studies oriented toward drug delivery. PMID:27706041

Green synthesis of biocompatible gold nanocrystals with tunable surface plasmon resonance using garlic phytochemicals.

PubMed

Menon, Deepthy; Basanth, Amritha; Retnakumari, Archana; Manzoor, K; Nair, Shantikumar V

2012-12-01

Synthesis of biocompatible gold nanoparticles having tunable optical absorbance finds immense use in biomedical applications such as cancer diagnosis and photothermal therapy. Hence, it is imperative to develop environment and bio-friendly green chemical processes that aid in preparing gold nanoparticles with tunable optical properties. In the present work, phytochemicals present in the medicinal herb, viz., garlic, were used to provide the dual effects of reduction of gold salts to gold nanoparticles as well as stabilization, in a single step process. The optical tunability of nanogold with respect to concentration of precursor and volume of garlic extract, processing conditions of garlic, its differing molecular weight fractions, reaction time and temperature has been demonstrated. The presence of a range of anisotropic nanogold including nanotriangles, nanorods and nanospheres as evident from TEM endows the colloid with a tunable optical absorption, specifically into the near infrared region. In vitro stability studies of the colloidal suspension in various media including saline, BSA, histidine and PBS showed that gold nanoparticles did not aggregate with time or differing pH conditions. The role of the garlic phytochemicals in providing stability against agglomeration was also substantiated by FTIR studies. Cytotoxicity studies performed using spherical and anisotropic gold nanoparticles on MCF-7 and L929 cell lines proved the biocompatibility of the material up to high doses of 500 microg/ml. The present work highlights the role of garlic phytochemicals in preparing biocompatible metallic gold nanoparticles with tunable optical properties and good in vitro stability, suggesting its potential use for molecular imaging or therapeutic nanomedicines.

Controllable asymmetric transmission via gap-tunable acoustic metasurface

NASA Astrophysics Data System (ADS)

Liu, Bingyi; Jiang, Yongyuan

2018-04-01

In this work, we utilize the acoustic gradient metasurface (AGM) of a bilayer configuration to realize the controllable asymmetric transmission. Relying on the adjustable gap between the two composing layers, the metasurface could switch from symmetric transmission to asymmetric transmission at a certain gap value. The underlying mechanism is attributed to the interference between the forward diffracted waves scattered by the surface bound waves at two air-AGM interfaces, which is apparently influenced by the interlayer distance. We further utilize the hybrid acoustic elements to construct the desired gradient metasurface with a tunable gap and validate the controllable asymmetric transmission with full-wave simulations. Our work provides the solution for actively controlling the transmission property of an acoustic element, which shows potential application in acoustic communication as a dynamic tunable acoustic diode.

Tunable protease-activatable virus nanonodes.

PubMed

Judd, Justin; Ho, Michelle L; Tiwari, Abhinav; Gomez, Eric J; Dempsey, Christopher; Van Vliet, Kim; Igoshin, Oleg A; Silberg, Jonathan J; Agbandje-McKenna, Mavis; Suh, Junghae

2014-05-27

We explored the unique signal integration properties of the self-assembling 60-mer protein capsid of adeno-associated virus (AAV), a clinically proven human gene therapy vector, by engineering proteolytic regulation of virus-receptor interactions such that processing of the capsid by proteases is required for infection. We find the transfer function of our engineered protease-activatable viruses (PAVs), relating the degree of proteolysis (input) to PAV activity (output), is highly nonlinear, likely due to increased polyvalency. By exploiting this dynamic polyvalency, in combination with the self-assembly properties of the virus capsid, we show that mosaic PAVs can be constructed that operate under a digital AND gate regime, where two different protease inputs are required for virus activation. These results show viruses can be engineered as signal-integrating nanoscale nodes whose functional properties are regulated by multiple proteolytic signals with easily tunable and predictable response surfaces, a promising development toward advanced control of gene delivery.

Tunable Protease-Activatable Virus Nanonodes

PubMed Central

2015-01-01

We explored the unique signal integration properties of the self-assembling 60-mer protein capsid of adeno-associated virus (AAV), a clinically proven human gene therapy vector, by engineering proteolytic regulation of virus–receptor interactions such that processing of the capsid by proteases is required for infection. We find the transfer function of our engineered protease-activatable viruses (PAVs), relating the degree of proteolysis (input) to PAV activity (output), is highly nonlinear, likely due to increased polyvalency. By exploiting this dynamic polyvalency, in combination with the self-assembly properties of the virus capsid, we show that mosaic PAVs can be constructed that operate under a digital AND gate regime, where two different protease inputs are required for virus activation. These results show viruses can be engineered as signal-integrating nanoscale nodes whose functional properties are regulated by multiple proteolytic signals with easily tunable and predictable response surfaces, a promising development toward advanced control of gene delivery. PMID:24796495

Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

NASA Technical Reports Server (NTRS)

Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

2012-01-01

Thin Si films coated on porous 3D particles composed of curved 2D graphene sheets have been synthesized utilizing techniques that allow for tunable properties. Since graphene exhibits specific surface area up to 100 times higher than carbon black or graphite, the deposition of the same mass of Si on graphene is much faster in comparison -- a factor which is important for practical applications. In addition, the distance between graphene layers is tunable and variation in the thickness of the deposited Si film is feasible. Both of these characteristics allow for optimization of the energy and power characteristics. Thicker films will allow higher capacity, but slower rate capabilities. Thinner films will allow more rapid charging, or higher power performance. In this innovation, uniform deposition of Si and C layers on high-surface area graphene produced granules with specific surface area (SSA) of 5 sq. m/g.

Tunable antenna radome based on graphene frequency selective surface

NASA Astrophysics Data System (ADS)

Qu, Meijun; Rao, Menglou; Li, Shufang; Deng, Li

2017-09-01

In this paper, a graphene-based frequency selective surface (FSS) is proposed. The proposed FSS exhibits a tunable bandpass filtering characteristic due to the alterable conductivity of the graphene strips which is controlled by chemical potential. Based on the reconfigurable bandpass property of the proposed FSS, a cylindrical antenna radome is designed using the FSS unit cells. A conventional omnidirectional dipole can realize a two-beam directional pattern when it is placed into the proposed antenna radome. Forward and backward endfire radiations of the dipole loaded with the radome is realized by properly adjusting the chemical potential. The proposed antenna radome is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems when the gain of a conventional antenna needs to be enhanced.

Design of tunable ultraviolet (UV) absorbance by controlling the Agsbnd Al co-sputtering deposition

NASA Astrophysics Data System (ADS)

Zhang, Xin-Yuan; Chen, Lei; Wang, Yaxin; Zhang, Yongjun; Yang, Jinghai; Choi, Hyun Chul; Jung, Young Mee

2018-05-01

Changing the structure and composition of a material can alter its properties; hence, the controlled fabrication of metal nanostructures plays a key role in a wide range of applications. In this study, the structure of Agsbnd Al ordered arrays fabricated by co-sputtering deposition onto a monolayer colloidal crystal significantly increased its ultraviolet (UV) absorbance owing to a tunable localized surface plasmon resonance (LSPR) effect. By increasing the spacing between two nanospheres and the content of aluminum, absorbance in the UV region could be changed from UVA (320-400 nm) to UVC (200-275 nm), and the LSPR peak in the visible region gradually shifted to the UV region. This provides the potential for surface-enhanced Raman scattering (SERS) in both the UV and visible regions.

Nano-Sized Cyclodextrin-Based Molecularly Imprinted Polymer Adsorbents for Perfluorinated Compounds—A Mini-Review

PubMed Central

Karoyo, Abdalla H.; Wilson, Lee D.

2015-01-01

Recent efforts have been directed towards the design of efficient and contaminant selective remediation technology for the removal of perfluorinated compounds (PFCs) from soils, sediments, and aquatic environments. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal materials design of sorbents for selective uptake of PFCs. This article reviews the sorptive uptake of PFCs using cyclodextrin (CD)-based polymer adsorbents with nano- to micron-sized structural attributes. The relationship between synthesis of adsorbent materials and their structure relate to the overall sorption properties. Hence, the adsorptive uptake properties of CD-based molecularly imprinted polymers (CD-MIPs) are reviewed and compared with conventional MIPs. Further comparison is made with non-imprinted polymers (NIPs) that are based on cross-linking of pre-polymer units such as chitosan with epichlorohydrin in the absence of a molecular template. In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphology that may vary considerably. This mini-review provides a rationale for the design of unique polymer adsorbent materials that employ an intrinsic porogen via incorporation of a macrocyclic compound in the polymer framework to afford adsorbent materials with tunable physicochemical properties and unique nanostructure properties. PMID:28347047

Tunable particles alter macrophage uptake based on combinatorial effects of physical properties

PubMed Central

Garapaty, Anusha

2017-01-01

Abstract The ability to tune phagocytosis of particle‐based therapeutics by macrophages can enhance their delivery to macrophages or reduce their phagocytic susceptibility for delivery to non‐phagocytic cells. Since phagocytosis is affected by the physical and chemical properties of particles, it is crucial to identify any interplay between physical properties of particles in altering phagocytic interactions. The combinatorial effect of physical properties size, shape and stiffness was investigated on Fc receptor mediated macrophage interactions by fabrication of layer‐by‐layer tunable particles of constant surface chemistry. Our results highlight how changing particle stiffness affects phagocytic interaction intricately when combined with varying size or shape. Increase in size plays a dominant role over reduction in stiffness in reducing internalization by macrophages for spherical particles. Internalization of rod‐shaped, but not spherical particles, was highly dependent on stiffness. These particles demonstrate the interplay between size, shape and stiffness in interactions of Fc‐functionalized particles with macrophages during phagocytosis. PMID:29313025

A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner

NASA Astrophysics Data System (ADS)

Barsbay, Murat; Güven, Olgun

2009-12-01

Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly γ radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of γ radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of γ radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

Tunable optical response of bowtie nanoantenna arrays on thermoplastic substrates

NASA Astrophysics Data System (ADS)

Sharac, N.; Sharma, H.; Veysi, M.; Sanderson, R. N.; Khine, M.; Capolino, F.; Ragan, R.

2016-03-01

Thermally responsive polymers present an interesting avenue for tuning the optical properties of nanomaterials on their surfaces by varying their periodicity and shape using facile processing methods. Gold bowtie nanoantenna arrays are fabricated using nanosphere lithography on prestressed polyolefin (PO), a thermoplastic polymer, and optical properties are investigated via a combination of spectroscopy and electromagnetic simulations to correlate shape evolution with optical response. Geometric features of bowtie nanoantennas evolve by annealing at temperatures between 105 °C and 135 °C by releasing the degree of prestress in PO. Due to the higher modulus of Au versus PO, compressive stress occurs on Au bowtie regions on PO, which leads to surface buckling at the two highest annealing temperatures; regions with a 5 nm gap between bowtie nanoantennas are observed and the average reduction is 75%. Reflectance spectroscopy and full-wave electromagnetic simulations both demonstrate the ability to tune the plasmon resonance wavelength with a window of approximately 90 nm in the range of annealing temperatures investigated. Surface-enhanced Raman scattering measurements demonstrate that maximum enhancement is observed as the excitation wavelength approaches the plasmon resonance of Au bowtie nanoantennas. Both the size and morphology tunability offered by PO allows for customizing optical response.

Frequency-tunable terahertz absorber with wire-based metamaterial and graphene

NASA Astrophysics Data System (ADS)

Xiong, Han; Jiang, Yan-Nan; Yang, Cheng; Zeng, Xiao-Ping

2018-01-01

We present a dynamically tunable metamaterial graphene absorber (MGA) in the terahertz regime. The unit cell of the proposed MGA consists of metal wire and graphene sheet over the grounded dielectric absorber. The MGA achieves frequency tunable characteristics via changing the chemical potential. In order to understand the absorption mechanism of this absorber, a simple equivalent circuit method has been proposed. Because the coupling between wire-based metamaterial and graphene is complicated and cannot be neglected an equivalent surface impedance was introduced and extracted for simplification. In addition to the chemical potential of graphene, the constitutive parameters of metal wire are also discussed in detail to completely understand how these factors affect the absorption properties. It is believed that this study may be useful for providing valuable guidance in the development of more advanced MGAs.

Dynamic biophotonics: female squid exhibit sexually dimorphic tunable leucophores and iridocytes.

PubMed

DeMartini, Daniel G; Ghoshal, Amitabh; Pandolfi, Erica; Weaver, Aaron T; Baum, Mary; Morse, Daniel E

2013-10-01

Loliginid squid use tunable multilayer reflectors to modulate the optical properties of their skin for camouflage and communication. Contained inside specialized cells called iridocytes, these photonic structures have been a model for investigations into bio-inspired adaptive optics. Here, we describe two distinct sexually dimorphic tunable biophotonic features in the commercially important species Doryteuthis opalescens: bright stripes of rainbow iridescence on the mantle just beneath each fin attachment and a bright white stripe centered on the dorsal surface of the mantle between the fins. Both of these cellular features are unique to the female; positioned in the same location as the conspicuously bright white testis in the male, they are completely switchable, transitioning between transparency and high reflectivity. The sexual dimorphism, location and tunability of these features suggest that they may function in mating or reproduction. These features provide advantageous new models for investigation of adaptive biophotonics. The intensely reflective cells of the iridescent stripes provide a greater signal-to-noise ratio than the adaptive iridocytes studied thus far, while the cells constituting the white stripe are adaptive leucophores--unique biological tunable broadband scatterers containing Mie-scattering organelles activated by acetylcholine, and a unique complement of reflectin proteins.

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

DOE PAGES

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.; ...

2017-07-31

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

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

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

CH-π Interaction Driven Macroscopic Property Transition on Smart Polymer Surface

NASA Astrophysics Data System (ADS)

Li, Minmin; Qing, Guangyan; Xiong, Yuting; Lai, Yuekun; Sun, Taolei

2015-10-01

Life systems have evolved to utilize weak noncovalent interactions, particularly CH-π interaction, to achieve various biofunctions, for example cellular communication, immune response, and protein folding. However, for artificial materials, it remains a great challenge to recognize such weak interaction, further transform it into tunable macroscopic properties and realize special functions. Here we integrate monosaccharide-based CH-π receptor capable of recognizing aromatic peptides into a smart polymer with three-component “Recognition-Mediating-Function” design, and report the CH-π interaction driven surface property switching on smart polymer film, including wettability, adhesion, viscoelasticity and stiffness. Detailed studies indicate that, the CH-π interaction induces the complexation between saccharide unit and aromatic peptide, which breaks the initial amphiphilic balance of the polymer network, resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties. This work not only presents a new approach to control the surface property of materials, but also points to a broader research prospect on CH-π interaction at a macroscopic level.

CH-π Interaction Driven Macroscopic Property Transition on Smart Polymer Surface.

PubMed

Li, Minmin; Qing, Guangyan; Xiong, Yuting; Lai, Yuekun; Sun, Taolei

2015-10-29

Life systems have evolved to utilize weak noncovalent interactions, particularly CH-π interaction, to achieve various biofunctions, for example cellular communication, immune response, and protein folding. However, for artificial materials, it remains a great challenge to recognize such weak interaction, further transform it into tunable macroscopic properties and realize special functions. Here we integrate monosaccharide-based CH-π receptor capable of recognizing aromatic peptides into a smart polymer with three-component "Recognition-Mediating-Function" design, and report the CH-π interaction driven surface property switching on smart polymer film, including wettability, adhesion, viscoelasticity and stiffness. Detailed studies indicate that, the CH-π interaction induces the complexation between saccharide unit and aromatic peptide, which breaks the initial amphiphilic balance of the polymer network, resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties. This work not only presents a new approach to control the surface property of materials, but also points to a broader research prospect on CH-π interaction at a macroscopic level.

Photonic polymer-blend structures and method for making

DOEpatents

Barnes, Michael D.

2004-06-29

The present invention comprises the formation of photonic polymer-blend structures having tunable optical and mechanical properties. The photonic polymer-blend structures comprise monomer units of spherical microparticles of a polymer-blend material wherein the spherical microparticles have surfaces partially merged with one another in a robust inter-particle bond having a tunable inter-particle separation or bond length sequentially attached in a desired and programmable architecture. The photonic polymer-blend structures of the present invention can be linked by several hundred individual particles sequentially linked to form complex three-dimensional structures or highly ordered two-dimensional arrays of 3D columns with 2D spacing.

Non-Uniform Bias Enhancement of a Varactor-Tuned FSS used with a Low Profile 2.4 GHz Dipole Antenna

NASA Technical Reports Server (NTRS)

Cure, David; Weller, Thomas M.; Miranda, Felix A.

2012-01-01

In this paper a low profile antenna using a nonuniformly biased varactor-tuned frequency selective surface (FSS) is presented. The tunable FSS avoids the use of vias and has a simplified DC bias network. The voltages to the DC bias ports can be varied independently allowing adjustment in the frequency response and enhanced radiation properties. The measured data demonstrate tunability from 2.15 GHz to 2.63 GHz with peak efficiencies that range from 50% to 90% and instantaneous bandwidths of 50 MHz to 280 MHz within the tuning range. The total antenna thickness is approximately lambda/45.

Magnetically tunable unidirectional waveguide based on magnetic photonic crystals

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

Tong, Weiwei; Wang, Jiafu, E-mail: wangjiafu1981@126.com, E-mail: qushaobo@mail.xjtu.edu.cn; Wang, Jun

2016-08-01

In this letter, we presented a magnetically tunable ferrite-loaded unidirectional waveguide based on magnetic photonic crystals. Two rows of ferrite rods are symmetrically arranged near the two lateral sides of the rectangular waveguide, where they are biased with static magnetic fields with the same amplitude and opposite directions along the rod axis. Since the magnetic one-way transmission is induced by the magnetic surface plasmon resonance, the operating band of the unidirectional waveguide can be tuned by changing the biased magnetic field intensity. To validate the design, a prototype was fabricated and measured. Both the simulation and experiment results verify themore » unidirectional transmission property.« less

Interfacial engineering of microstructured materials

NASA Astrophysics Data System (ADS)

Poda, Aimee

The tribological behavior of octadecyltrichlorosilane self assembled monolayers (OTS-SAMs) has been successfully exploited to reduce energy losses and to produce adequate adhesion barrier properties on many MEMS surfaces. Unfortunately, performance discrepancies are reported in the literature between films produced on smooth surfaces as compared to typical MEMS surfaces maintaining topographical roughness. Rational explanations in terms of reproducibility issues, production considerations, and the scale of measurement technique have been introduced to account for some of the variation. The tribological phenomena at the micro-scale are complicated by the fact that rather than inertial effects, the forces associated with the surface become dominant factors influencing the mechanical behavior of contacting components. In MEMS, real mechanical contacts typically consist of a few nanometer scale asperities. Furthermore, various surface topographies exist for MEMS device fabrication and their corresponding asperity profiles can vary drastically based on the production process. This dissertation presents research focusing on the influence of topographical asperities on OTS film properties of relevance for efficient tribological improvement. A fundamental approach has been taken to carefully examine the factors that contribute to high quality film formation, specifically formation temperature and the role of interfacial water layer associated with the sample surface. As evidenced on smooth surfaces, the characteristics for successful tribological performance of OTS films are strongly dependent on the lateral packing density and molecular orientation of the monolayer. Limited information is available on how monolayers associate on topographical asperities and whether these topographical asperities influence the interfacial reactivity of MEMS surfaces. A silica film produced from a low temperature, vapor-phase hydrolysis of tetrachlorosilane with a tunable topography is introduced and leveraged as a novel investigative platform for advanced analytical investigations often restricted to use on smooth surfaces. This tunable surface allows intellectual insight into the nature of surface properties associated with silica surfaces, the uptake of interfacial water and the subsequent influence of surface morphology on OTS film formation. FTIR analysis was utilized for an examination of interfacial properties on both smooth Si(100) surfaces and on the tunable MVD topography in combination with an investigation of OTS film formation mechanism. A dilute etchant technique is developed to provide topographic contrast for AFM imaging to allow direct examination of film packing characteristics in relation to surface asperities. A relationship between monolayer adsorption characteristics and topographical asperities with observed variations in monolayer order resultant from surface roughness has been elucidated. Results show that the packing structure of OTS monolayers is dependent on the local asperity curvature which is qualitatively different from that observed on flat surfaces. In addition, a difference in surface reactivity is observed as a result of different surface topographies with thicker silica layers maintaining a thicker interfacial water layer resulting in a higher coverage of OTS monolayers at similar reaction times and conditions. This work shows changes in surface reactivity as a consequence of different morphological surface characteristics and preparation procedures. Additional research is presented on a new class of SAM, namely octadecylphoshonic acid and its monolayer formation mechanism and properties are compared to conventional OTS monolayers. This monolayer is translated to investigative probes based on Aluminum oxide specifically tailored for a tribological comparison across multi-scale friction regimes.

Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications.

PubMed

Smirnov, Serguei; Anoshkin, Ilya V; Demchenko, Petr; Gomon, Daniel; Lioubtchenko, Dmitri V; Khodzitsky, Mikhail; Oberhammer, Joachim

2018-06-21

Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.

Characterization of PDMS samples with variation of its synthesis parameters for tunable optics applications

NASA Astrophysics Data System (ADS)

Marquez-Garcia, Josimar; Cruz-Félix, Angel S.; Santiago-Alvarado, Agustin; González-García, Jorge

2017-09-01

Nowadays the elastomer known as polydimethylsiloxane (PDMS, Sylgard 184), due to its physical properties, low cost and easy handle, have become a frequently used material for the elaboration of optical components such as: variable focal length liquid lenses, optical waveguides, solid elastic lenses, etc. In recent years, we have been working in the characterization of this material for applications in visual sciences; in this work, we describe the elaboration of PDMSmade samples, also, we present physical and optical properties of the samples by varying its synthesis parameters such as base: curing agent ratio, and both, curing time and temperature. In the case of mechanical properties, tensile and compression tests were carried out through a universal testing machine to obtain the respective stress-strain curves, and to obtain information regarding its optical properties, UV-vis spectroscopy is applied to the samples to obtain transmittance and absorbance curves. Index of refraction variation was obtained through an Abbe refractometer. Results from the characterization will determine the proper synthesis parameters for the elaboration of tunable refractive surfaces for potential applications in robotics.

Orbital engineering of nickelates in three-component heterostructures

NASA Astrophysics Data System (ADS)

Disa, Ankit; Kumah, Divine; Malashevich, Andrei; Chen, Hanghui; Ismail-Beigi, Sohrab; Walker, Fred; Ahn, Charles; Specht, Eliot; Arena, Dario

2015-03-01

The orbital configuration of complex oxides dictates the emergence of a wide range of properties, including metal-insulator transitions, interfacial magnetism, and high-temperature superconductivity. In this work, we experimentally demonstrate a novel method for achieving large and tunable orbital polarizations in nickelates. The technique is based on leveraging three-component, atomically layered superlattices to yield a combination of inversion symmetry breaking, charge transfer, and polar distortions. In the system we studied, composed of LaTiO3/LaNiO3/LaAlO3, we use synchrotron x-ray diffraction and spectroscopy to characterize these properties and show that they lead to fully broken orbital degeneracy in the nickelate layer consistent with a single-band Fermi surface. Furthermore, we show that this system is widely tunable and enables quasi-continuous orbital control unachievable by conventional strain and confinement-based approaches. This technique provides an experimentally realizable route for accessing and studying novel orbitally dependent quantum phenomena.

Peptide-Decorated Tunable-Fluorescence Graphene Quantum Dots.

PubMed

Sapkota, Bedanga; Benabbas, Abdelkrim; Lin, Hao-Yu Greg; Liang, Wentao; Champion, Paul; Wanunu, Meni

2017-03-22

We report here the synthesis of graphene quantum dots with tunable size, surface chemistry, and fluorescence properties. In the size regime 15-35 nm, these quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon absorption (TPA) cross section (6500 Göppert-Mayer units). Furthermore, through noncovalent tailoring of the chemistry of these quantum dots, we obtain water-stable quantum dots. For example, quantum dots with lysine groups bind strongly to DNA in solution and inhibit polymerase-based DNA strand synthesis. Finally, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, but they do not enter the cell nucleus.

Dielectric properties of BaMg1/3Nb2/3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

NASA Astrophysics Data System (ADS)

Alema, Fikadu; Pokhodnya, Konstantin

2015-11-01

Ba(Mg1/3Nb2/3)O3 (BMN) doped and undoped Ba0.45Sr0.55TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss (˜38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg2+ whose detrimental effect on tunability is partially compensated by small Nb5+ as the two substitute Ti4+ in the BST. The coupling between MgTi″ and VO•• charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was investigated in the temperature range of 300-450K. A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from MgTi″, VO•• and NbTi• charged defects. The carrier transport properties of the films were analyzed in light of Schottky thermionic emission (SE) and Poole-Frenkel (PF) emission mechanisms. The result indicated that while the carrier transport mechanism in the undoped film is interface limited (SE), the conduction in the BMN doped film was dominated by bulk processes (PF). The change of the conduction mechanism from SE to PF as a result of BMN doping is attributed to the presence of uncoupled NbTi• sitting as a positive trap center at the shallow donor level of the BST.

Nearly-octave wavelength tuning of a continuous wave fiber laser

PubMed Central

Zhang, Lei; Jiang, Huawei; Yang, Xuezong; Pan, Weiwei; Cui, Shuzhen; Feng, Yan

2017-01-01

The wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 μm is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output. PMID:28198414

Tunable geometric Fano resonances in a metal/insulator stack

NASA Astrophysics Data System (ADS)

Grotewohl, Herbert

We present a theoretical analysis of surface-plasmon-mediated mode-coupling in a planar thin film metal/insulator stack. The spatial overlap of a surface plasmon polariton (SPP) and a waveguide mode results in a Fano interference analog. Tuning of the material parameters effects the modes and output fields of the system. Lastly, the intensity and phase sensitivity of the system are compared to a standard surface plasmon resonance (SPR). We begin with background information on Fano interference, an interference effect between two indistinguishable pathways. Originally described for autoionization, we discuss the analogs in other systems. We discuss the features of Fano interference in the mode diagrams, and the Fano resonance observed in the output field. The idea of a geometric Fano resonance (GFR) occurring in the angular domain is presented. Background information on surface plasmon polaritons is covered next. The dielectric properties of metals and how they relate to surface plasmons is first reviewed. The theoretical background of SPPs on an infinite planar surface is covered. The modes of a two planar interface metal/insulator stack are reviewed and the leaky properties of the waveguide are shown in the reflectance. We solve for modes of a three interface metal/insulator stack and shows an avoided crossing in the modes indicative of Fano interference. We observe the asymmetric Fano resonance in the angular domain in the reflectance. The tunability of the material parameters tunes the GFR of the system. The GFR tuning is explored and different Fano lineshapes are observed. We also observe a reversal of the asymmetry Fano lineshape, attributed to the relate phase interactions of the non-interacting modes. The phase of the GFR is calculated and discussed for the variations of the parameters. The reflected field is explored as the insulator permittivities are varied. As the waveguide permittivity is varied, we show there is little response from the system. As the exterior permittivity is varied, the reflectance exhibits the geometric Fano resonance and the tunability of the lineshape is explored. Finally, we calculate the sensitivities of our metal/insulator stack to changes in the permittivity and compare them to the sensitivities of SPRs.

Tailorable Surface Morphology of 3D Scaffolds by Combining Additive Manufacturing with Thermally Induced Phase Separation.

PubMed

Di Luca, Andrea; de Wijn, Joost R; van Blitterswijk, Clemens A; Camarero-Espinosa, Sandra; Moroni, Lorenzo

2017-08-01

The functionalization of biomaterials substrates used for cell culture is gearing towards an increasing control over cell activity. Although a number of biomaterials have been successfully modified by different strategies to display tailored physical and chemical surface properties, it is still challenging to step from 2D substrates to 3D scaffolds with instructive surface properties for cell culture and tissue regeneration. In this study, additive manufacturing and thermally induced phase separation are combined to create 3D scaffolds with tunable surface morphology from polymer gels. Surface features vary depending on the gel concentration, the exchanging temperature, and the nonsolvent used. When preosteoblasts (MC-3T3 cells) are cultured on these scaffolds, a significant increase in alkaline phosphatase activity is measured for submicron surface topography, suggesting a potential role on early cell differentiation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation of ultra-wideband achromatic Airy plasmons on a graphene surface.

PubMed

Guan, Chunying; Yuan, Tingting; Chu, Rang; Shen, Yize; Zhu, Zheng; Shi, Jinhui; Li, Ping; Yuan, Libo; Brambilla, Gilberto

2017-02-01

Tunable ultra-wideband achromatic plasmonic Airy beams are demonstrated on graphene surfaces. Surface plasmonic polaritons are excited using diffractive gratings. The phase and amplitude of plasmonic waves on the graphene surface are determined by the relative position between the grating arrays and the duty ratio of the grating unit cell, respectively. The transverse acceleration and nondiffraction properties of plasmonic waves are observed. The achromatic Airy plasmons with identical acceleration trajectory at different excited frequencies can be achieved by tuning dynamically the Fermi energy of graphene without reoptimizing the grating structures. The proposed devices may find applications in photonics integrations and surface optical manipulation.

Silicon-Based Anode and Method for Manufacturing the Same

NASA Technical Reports Server (NTRS)

Yushin, Gleb Nikolayevich (Inventor); Zdyrko, Bogdan (Inventor); Magasinski, Alexandre (Inventor); Luzinov, Igor (Inventor)

2017-01-01

A silicon-based anode comprising silicon, a carbon coating that coats the surface of the silicon, a polyvinyl acid that binds to at least a portion of the silicon, and vinylene carbonate that seals the interface between the silicon and the polyvinyl acid. Because of its properties, polyvinyl acid binders offer improved anode stability, tunable properties, and many other attractive attributes for silicon-based anodes, which enable the anode to withstand silicon cycles of expansion and contraction during charging and discharging.

Self-organizing layers from complex molecular anions

DOE PAGES

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.; ...

2018-05-14

The formation of traditional ionic materials occurs principally via joint accumulation of both anions and cations. Here in this paper, we describe a previously unreported phenomenon by which macroscopic liquid-like thin layers with tunable self-organization properties form through accumulation of stable complex ions of one polarity on surfaces. Using a series of highly stable molecular anions we demonstrate a strong influence of the internal charge distribution of the molecular ions, which is usually shielded by counterions, on the properties of the layers. Detailed characterization reveals that the intrinsically unstable layers of anions on surfaces are stabilized by simultaneous accumulation ofmore » neutral molecules from the background environment. Different phases, self-organization mechanisms and optical properties are observed depending on the molecular properties of the deposited anions, the underlying surface and the coadsorbed neutral molecules. This demonstrates rational control of the macroscopic properties (morphology and size of the formed structures) of the newly discovered anion-based layers.« less

Self-organizing layers from complex molecular anions

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

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.

The formation of traditional ionic materials occurs principally via joint accumulation of both anions and cations. Here in this paper, we describe a previously unreported phenomenon by which macroscopic liquid-like thin layers with tunable self-organization properties form through accumulation of stable complex ions of one polarity on surfaces. Using a series of highly stable molecular anions we demonstrate a strong influence of the internal charge distribution of the molecular ions, which is usually shielded by counterions, on the properties of the layers. Detailed characterization reveals that the intrinsically unstable layers of anions on surfaces are stabilized by simultaneous accumulation ofmore » neutral molecules from the background environment. Different phases, self-organization mechanisms and optical properties are observed depending on the molecular properties of the deposited anions, the underlying surface and the coadsorbed neutral molecules. This demonstrates rational control of the macroscopic properties (morphology and size of the formed structures) of the newly discovered anion-based layers.« less

A new series of two-dimensional silicon crystals with versatile electronic properties

NASA Astrophysics Data System (ADS)

Chae, Kisung; Kim, Duck Young; Son, Young-Woo

2018-04-01

Silicon (Si) is one of the most extensively studied materials owing to its significance to semiconductor science and technology. While efforts to find a new three-dimensional (3D) Si crystal with unusual properties have made some progress, its two-dimensional (2D) phases have not yet been explored as much. Here, based on a newly developed systematic ab initio materials searching strategy, we report a series of novel 2D Si crystals with unprecedented structural and electronic properties. The new structures exhibit perfectly planar outermost surface layers of a distorted hexagonal network with their thicknesses varying with the atomic arrangement inside. Dramatic changes in electronic properties ranging from semimetal to semiconducting with indirect energy gaps and even to one with direct energy gaps are realized by varying thickness as well as by surface oxidation. Our predicted 2D Si crystals with flat surfaces and tunable electronic properties will shed light on the development of silicon-based 2D electronics technology.

A Dual Role of Graphene Oxide Sheet Deposition on Titanate Nanowire Scaffolds for Osteo-implantation: Mechanical Hardener and Surface Activity Regulator

NASA Astrophysics Data System (ADS)

Dong, Wenjun; Hou, Lijuan; Li, Tingting; Gong, Ziqiang; Huang, Huandi; Wang, Ge; Chen, Xiaobo; Li, Xiaoyun

2015-12-01

Scaffold biomaterials with open pores and channels are favourable for cell growth and tissue regeneration, however the inherent poor mechanical strength and low surface activity limit their applications as load-bearing bone grafts with satisfactory osseointegration. In this study, macro-porous graphene oxide (GO) modified titanate nanowire scaffolds with desirable surface chemistry and tunable mechanical properties were prepared through a simple hydrothermal process followed by electrochemical deposition of GO nanosheets. The interconnected and porous structure of the GO/titanate nanowire scaffolds provides a large surface area for cellular attachment and migration and displays a high compressive strength of approximately 81.1 MPa and a tunable Young’s modulus over the range of 12.4-41.0 GPa, which satisfies site-specific requirements for implantation. Surface chemistry of the scaffolds was modulated by the introduction of GO, which endows the scaffolds flexibility in attaching and patterning bioactive groups (such as -OH, -COOH and -NH2). In vitro cell culture tests suggest that the GO/titanate nanowire scaffolds act as a promising biomaterial candidate, in particular the one terminated with -OH groups, which demonstrates improved cell viability, and proliferation, differentiation and osteogenic activities.

A Dual Role of Graphene Oxide Sheet Deposition on Titanate Nanowire Scaffolds for Osteo-implantation: Mechanical Hardener and Surface Activity Regulator.

PubMed

Dong, Wenjun; Hou, Lijuan; Li, Tingting; Gong, Ziqiang; Huang, Huandi; Wang, Ge; Chen, Xiaobo; Li, Xiaoyun

2015-12-21

Scaffold biomaterials with open pores and channels are favourable for cell growth and tissue regeneration, however the inherent poor mechanical strength and low surface activity limit their applications as load-bearing bone grafts with satisfactory osseointegration. In this study, macro-porous graphene oxide (GO) modified titanate nanowire scaffolds with desirable surface chemistry and tunable mechanical properties were prepared through a simple hydrothermal process followed by electrochemical deposition of GO nanosheets. The interconnected and porous structure of the GO/titanate nanowire scaffolds provides a large surface area for cellular attachment and migration and displays a high compressive strength of approximately 81.1 MPa and a tunable Young's modulus over the range of 12.4-41.0 GPa, which satisfies site-specific requirements for implantation. Surface chemistry of the scaffolds was modulated by the introduction of GO, which endows the scaffolds flexibility in attaching and patterning bioactive groups (such as -OH, -COOH and -NH2). In vitro cell culture tests suggest that the GO/titanate nanowire scaffolds act as a promising biomaterial candidate, in particular the one terminated with -OH groups, which demonstrates improved cell viability, and proliferation, differentiation and osteogenic activities.

Improvement in temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films using Ba(Mg1/3Ta2/3)O3 buffer layer

NASA Astrophysics Data System (ADS)

Wu, Zhi; Zhou, Jing; Chen, Wen; Shen, Jie; Yang, Huimin; Zhang, Shisai; Liu, Yueli

2016-12-01

In this paper, Pb(Zr0.52Ti0.48)O3 (PZT) thin films were prepared via sol-gel method. The effects of Ba(Mg1/3Ta2/3)O3 (BMT) buffer layer on the temperature dependence and dielectric tunability properties of PZT thin films were studied. As the thickness of BMT buffer layer increases, the tan δ and tunability of PZT thin films decrease while tunability still maintains above 10%. This result shows that BMT buffer layer can improve the dielectric tunability properties of PZT thin films. Furthermore, the temperature coefficient of the dielectric constant decreases from 2333.4 to 906.9 ppm/°C with the thickness of BMT buffer layer increasing in the range from 25 to 205 °C, indicating that BMT buffer layer can improve the temperature stability of PZT thin films. Therefore, BMT buffer layer plays a critical role in improving temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films.

Recent Progress on Stability and Passivation of Black Phosphorus.

PubMed

Abate, Yohannes; Akinwande, Deji; Gamage, Sampath; Wang, Han; Snure, Michael; Poudel, Nirakar; Cronin, Stephen B

2018-05-11

From a fundamental science perspective, black phosphorus (BP) is a canonical example of a material that possesses fascinating surface and electronic properties. It has extraordinary in-plane anisotropic electrical, optical, and vibrational states, as well as a tunable band gap. However, instability of the surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications. Early studies were limited by the degradation of black phosphorous surfaces in air. Recently, several robust strategies have been developed to mitigate these issues, and these novel developments can potentially allow researchers to exploit the extraordinary properties of this material and devices made out of it. Here, the fundamental chemistry of BP degradation and the tremendous progress made to address this issue are extensively reviewed. Device performances of encapsulated BP are also compared with nonencapsulated BP. In addition, BP possesses sensitive anisotropic photophysical surface properties such as excitons, surface plasmons/phonons, and topologically protected and Dirac semi-metallic surface states. Ambient degradation as well as any passivation method used to protect the surface could affect the intrinsic surface properties of BP. These properties and the extent of their modifications by both the degradation and passivation are reviewed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Yihuang; Wang, Zewei; He, Yanjie; Yoon, Young Jun; Jung, Jaehan; Zhang, Guangzhao; Lin, Zhiqun

2018-02-01

The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temperature, pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest molecule nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temperature- or pH-sensitive polymer-capped magnetic, ferroelectric, upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystallization kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnology, and biotechnology.

Tuning electronic and magnetic properties of GaN nanosheets by surface modifications and nanosheet thickness.

PubMed

Xiao, Meixia; Yao, Tingzhen; Ao, Zhimin; Wei, Peng; Wang, Danghui; Song, Haiyang

2015-04-14

Density-functional theory calculations are performed to investigate the effects of surface modifications and nanosheet thickness on the electronic and magnetic properties of gallium nitride (GaN) nanosheets (NSs). Unlike the bare GaN NSs terminating with polar surfaces, the systems with hydrogenated Ga (H-GaN), fluorinated Ga (F-GaN), and chlorinated Ga (Cl-GaN) preserve their initial wurtzite structures and exhibit ferromagnetic states. The abovementioned three different decorations on Ga atoms are energetically more favorable for thicker GaN NSs. Moreover, as the thickness increases, H-GaN and F-GaN NSs undergo semiconductor to metal and half-metal to metal transition, respectively, while Cl-GaN NSs remain completely metallic. The predicted diverse and tunable electronic and magnetic properties highlight the potential of GaN NSs for novel electronic and spintronic nanodevices.

Tunable Transmission-Line Metamaterials Mimicking Electromagnetically Induced Transparency

NASA Astrophysics Data System (ADS)

Feng, T. H.; Han, H. P.

2016-11-01

Tunable transmission-line (TL) metamaterials mimicking electromagnetically induced transparency (EIT) have been studied. Firstly, two types of tunable TL EIT-like metamaterial, based on the double split-ring resonator (DSRR) and single split-ring resonator (SSRR), were fabricated and their transmission properties carefully compared. The results showed that the transmittance maximum was almost invariable with shift of the transparency window for the tunable DSRR-based TL EIT-like metamaterial, but for the tunable SSRR-based TL EIT-like metamaterial, the transmittance maximum gradually diminished with shift of the transparency window toward the center of the absorption band. Moreover, the reason for these different transmission properties was explored, revealing that the reduction of the transmittance maximum of the transparency window for the tunable SSRR-based TL EIT-like metamaterial is mainly due to energy loss caused by the resistance of the loaded varactor diodes.

Tunable magnetic properties by interfacial manipulation of L1(0)-FePt perpendicular ultrathin film with island-like structures.

PubMed

Feng, C; Wang, S G; Yang, M Y; Zhang, E; Zhan, Q; Jiang, Y; Li, B H; Yu, G H

2012-02-01

Based on interfacial manipulation of the MgO single crystal substrate and non-magnetic AIN compound, a L1(0)-FePt perpendicular ultrathin film with the structure of MgO/FePt-AIN/Ta was designed, prepared, and investigated. The film is comprised of L1(0)-FePt "magnetic islands," which exhibits a perpendicular magnetic anisotropy (PMA), tunable coercivity (Hc), and interparticle exchange coupling (IEC). The MgO substrate promotes PMA of the film because of interfacial control of the FePt lattice orientation. The AIN compound is doped to increase the difference of surface energy between FePt layer and MgO substrate and to suppress the growth of FePt grains, which takes control of island growth mode of FePt atoms. The AIN compound also acts as isolator of L1(0)-FePt islands to pin the sites of FePt domains, resulting in the tunability of Hc and IEC of the films.

Putting gold nanocages to work for optical imaging, controlled release and cancer theranostics

PubMed Central

Pang, Bo; Yang, Xuan; Xia, Younan

2016-01-01

Gold nanocages are hollow nanostructures with ultrathin, porous walls. They are bio-inert and their surface can be readily modified with functional groups to specifically interact with the biological system of interest. They have remarkable optical properties, including localized surface plasmon resonance peaks tunable to the near-infrared region, strong absorption and scattering, as well as two- and three-photon luminescence. With the establishment of robust protocols for both synthesis and surface functionalization, Au nanocages have been extensively explored for various biomedical applications. In this review, we begin with a brief account of the synthesis and properties of Au nanocages, and then highlight some of the recent developments in applying them to an array of biomedical applications related to optical imaging, controlled release and cancer theranostics. PMID:27348546

An investigation on the physicochemical properties of the nanostructured [(4-X)PMAT][N(CN)2] ion pairs as energetic and tunable aryl alkyl amino tetrazolium based ionic liquids

NASA Astrophysics Data System (ADS)

Khalili, Behzad; Rimaz, Mehdi

2017-06-01

In this study the different class of tunable and high nitrogen content ionic liquids termed TAMATILs (Tunable Aryl Methyl Amino Tetrazolium based Ionic Liquids) were designed. The physicochemical properties of the nanostructured TAMATILs composed of para substituted phenyl methyl amino tetrazolium cations [(4-X)PMAT]+ (X = H, Me, OCH3, OH, NH2, NO2, F, CN, CHO, CF3, COMe and CO2Me) and dicyanimide anion [N(CN)2]- were fully investigated using M06-2X functional in conjunction with the 6-311++G(2d,2p) basis set. For all of the studied nanostructured ILs the structural parameters, interaction energy, cation's enthalpy of formation, natural charges, charge transfer values and topological properties were calculated and discussed. The substituent effect on the interaction energy and physicochemical properties also is taking into account. The results showed that the strength of interaction has a linear correlation with electron content of the phenyl ring in a way the substituents with electron withdrawing effects lead to make more stable ion pairs with higher interaction energies. Some of the main physical properties of ILs such as surface tension, melting point, critical-point temperature, electrochemical stability and conductivity are discussed and estimated for studying ion pairs using quantum chemical computationally obtained thermochemical data. Finally the enthalpy and Gibbs free energy of formation for twelve nanostructured individual cations with the general formula of [(4-X)PMAT]+ (X = 4-H, 4-Me, 4-OMe, 4-OH, 4-NH2, 4-NO2, 4-F, 4-CN, 4-CHO, 4-CF3, 4-COMe and 4-CO2Me) are calculated.

Modification of electronic properties of graphene by using low-energy K{sup +} ions

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

Kim, Jingul; Lee, Paengro; Ryu, Mintae

2016-05-02

Despite its superb electronic properties, the semi-metallic nature of graphene with no band gap (E{sub g}) at the Dirac point has been a stumbling block for its industrial application. We report an improved means of producing a tunable band gap over other schemes by doping low energy (10 eV) potassium ions (K{sup +}) on single layer graphene formed on 6H-SiC(0001) surface, where the noble Dirac nature of the π-band remains almost unaltered. The changes in the π-band induced by K{sup +} ions reveal that the band gap increases gradually with increasing dose (θ) of the ions up to E{sub g} = 0.65 eV atmore » θ = 1.10 monolayers, demonstrating the tunable character of the band gap. Our core level data for C 1s, Si 2p, and K 2p suggest that the K{sup +}-induced asymmetry in charge distribution among carbon atoms drives the opening of band gap, which is in sharp contrast with no band gap when neutral K atoms are adsorbed on graphene. This tunable K{sup +}-induced band gap in graphene illustrates its potential application in graphene-based nano-electronics.« less

Self-organizing layers from complex molecular anions

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

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.

Ions are promising building blocks for tunable self-organizing materials with advanced technological applications. However, because of strong Coulomb attraction with counterions, the intrinsic properties of ions are difficult to exploit for preparation of bulk materials. Here, we report the precisely-controlled preparation of macroscopic surface layers by soft landing of mass selected complex anions which determine the self organization of the layers with their molecular properties. The family of halogenated dodecaborates [B12X12]2- (X = F, Cl, Br, I), in which the internal charge distribution between core and shell regions of the molecular ions systematically vary, was deposited on different self assembledmore » monolayer surfaces (SAMs) on gold at high coverage. Layers of anions were found to be stabilized by accumulation of neutral molecules. Different phases, self-organization mechanisms and optical properties were observed to depend upon the internal charge distribution of the deposited anions, the underlying surface and the coadsorbed molecules. This demonstrates rational control of the properties of anion based layers.« less

Formation of Triboelectric Series via Atomic-Level Surface Functionalization for Triboelectric Energy Harvesting.

PubMed

Shin, Sung-Ho; Bae, Young Eun; Moon, Hyun Kyung; Kim, Jungkil; Choi, Suk-Ho; Kim, Yongho; Yoon, Hyo Jae; Lee, Min Hyung; Nah, Junghyo

2017-06-27

Triboelectric charging involves frictional contact of two different materials, and their contact electrification usually relies on polarity difference in the triboelectric series. This limits the choices of materials for triboelectric contact pairs, hindering research and development of energy harvest devices utilizing triboelectric effect. A progressive approach to resolve this issue involves modification of chemical structures of materials for effectively engineering their triboelectric properties. Here, we describe a facile method to change triboelectric property of a polymeric surface via atomic-level chemical functionalizations using a series of halogens and amines, which allows a wide spectrum of triboelectric series over single material. Using this method, tunable triboelectric output power density is demonstrated in triboelectric generators. Furthermore, molecular-scale calculation using density functional theory unveils that electrons transferred through electrification are occupying the PET group rather than the surface functional group. The work introduced here would open the ability to tune triboelectric property of materials by chemical modification of surface and facilitate the development of energy harvesting devices and sensors exploiting triboelectric effect.

Tunable Wetting Property in Growth Mode-Controlled WS2 Thin Films

NASA Astrophysics Data System (ADS)

Choi, Byoung Ki; Lee, In Hak; Kim, Jiho; Chang, Young Jun

2017-04-01

We report on a thickness-dependent wetting property of WS2/Al2O3 and WS2/SiO2/Si structures. We prepared WS2 films with gradient thickness by annealing thickness-controlled WO3 films at 800 °C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS2 over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS2 films can account for the contrasting wetting properties between WS2/Al2O3 and WS2/SiO2/Si. The thickness dependence of water contact angle persisted for longer than 2 weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles.

PubMed

Bucaro, Michael A; Kolodner, Paul R; Taylor, J Ashley; Sidorenko, Alex; Aizenberg, Joanna; Krupenkin, Tom N

2009-04-09

In this paper, we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality-for example, a dynamic 3D projector, i.e., a light source which can scan an image onto a moving, nonplanar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles

NASA Astrophysics Data System (ADS)

Krupenkin, Tom; Bucaro, Mike; Kolodner, Paul; Taylor, Ashley; Sidorenko, Alex; Aizenberg, Joanna

2009-03-01

In this work we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically-functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality - for example, a dynamic 3D projector; i.e., a light source which can scan an image onto a moving, non-planar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe 2

DOE PAGES

Wu, Yun; Mou, Daixiang; Jo, Na Hyun; ...

2016-09-14

We use ultrahigh resolution, tunable, vacuum ultraviolet laser angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of WTe 2, a material that was predicted to be a type-II Weyl semimetal. The Weyl fermion states in WTe 2 were proposed to emerge at the crossing points of electron and hole pockets, and Fermi arcs connecting electron and hole pockets would be visible in the spectral function on (001) surface. Here we report the observation of such Fermi arcs in WTe 2 confirming the theoretical predictions. This provides strong evidence for type-II Weyl semimetallic states in WTe 2. Here, we alsomore » find that trivial and topological domains coexist on the same surface of the sample due to the presence of inhomogeneous strain detected by scanning electron microscopy data. This is in agreement with the theoretical prediction that strain can drive this system from topological Weyl to trivial semimetal. WTe 2 therefore provides a tunable playground for studying exotic topological quantum effects.« less

Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe 2

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

Wu, Yun; Mou, Daixiang; Jo, Na Hyun

We use ultrahigh resolution, tunable, vacuum ultraviolet laser angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of WTe 2, a material that was predicted to be a type-II Weyl semimetal. The Weyl fermion states in WTe 2 were proposed to emerge at the crossing points of electron and hole pockets, and Fermi arcs connecting electron and hole pockets would be visible in the spectral function on (001) surface. Here we report the observation of such Fermi arcs in WTe 2 confirming the theoretical predictions. This provides strong evidence for type-II Weyl semimetallic states in WTe 2. Here, we alsomore » find that trivial and topological domains coexist on the same surface of the sample due to the presence of inhomogeneous strain detected by scanning electron microscopy data. This is in agreement with the theoretical prediction that strain can drive this system from topological Weyl to trivial semimetal. WTe 2 therefore provides a tunable playground for studying exotic topological quantum effects.« less

Color-Tunable ZnO/GaN Heterojunction LEDs Achieved by Coupling with Ag Nanowire Surface Plasmons.

PubMed

Yang, Liu; Wang, Yue; Xu, Haiyang; Liu, Weizhen; Zhang, Cen; Wang, Chunliang; Wang, Zhongqiang; Ma, Jiangang; Liu, Yichun

2018-05-09

Color-tunable light-emitting devices (LEDs) have a great impact on our daily life. Herein, LEDs with tunable electroluminescence (EL) color were achieved via introducing Ag nanowires surface plasmons into p-GaN/n-ZnO film heterostructures. By optimizing the surface coverage density of coated Ag nanowires, the EL color was changed continuously from yellow-green to blue-violet. Transient-state and temperature-variable fluorescence emission characterizations uncovered that the spontaneous emission rate and the internal quantum efficiency of the near-UV emission were increased as a consequence of the resonance coupling interaction between Ag nanowires surface plasmons and ZnO excitons. This effect induces the selective enhancement of the blue-violet EL component but suppresses the defect-related yellow-green emission, leading to the observed tunable EL color. The proposed strategy of introducing surface plasmons can be further applied to many other kinds of LEDs for their selective enhancement of EL intensity and effective adjustment of the emission color.

Towards an in vitro model mimicking the foreign body response: tailoring the surface properties of biomaterials to modulate extracellular matrix.

PubMed

Damanik, Febriyani F R; Rothuizen, Tonia C; van Blitterswijk, Clemens; Rotmans, Joris I; Moroni, Lorenzo

2014-09-19

Despite various studies to minimize host reaction following a biomaterial implantation, an appealing strategy in regenerative medicine is to actively use such an immune response to trigger and control tissue regeneration. We have developed an in vitro model to modulate the host response by tuning biomaterials' surface properties through surface modifications techniques as a new strategy for tissue regeneration applications. Results showed tunable surface topography, roughness, wettability, and chemistry by varying treatment type and exposure, allowing for the first time to correlate the effect of these surface properties on cell attachment, morphology, strength and proliferation, as well as proinflammatory (IL-1β, IL-6) and antiinflammatory cytokines (TGF-β1, IL-10) secreted in medium, and protein expression of collagen and elastin. Surface microstructuring, derived from chloroform partial etching, increased surface roughness and oxygen content. This resulted in enhanced cell adhesion, strength and proliferation as well as a balance of soluble factors for optimum collagen and elastin synthesis for tissue regeneration. By linking surface parameters to cell activity, we could determine the fate of the regenerated tissue to create successful soft tissue-engineered replacement.

Towards an in vitro model mimicking the foreign body response: tailoring the surface properties of biomaterials to modulate extracellular matrix

NASA Astrophysics Data System (ADS)

Damanik, Febriyani F. R.; Rothuizen, Tonia C.; van Blitterswijk, Clemens; Rotmans, Joris I.; Moroni, Lorenzo

2014-09-01

Despite various studies to minimize host reaction following a biomaterial implantation, an appealing strategy in regenerative medicine is to actively use such an immune response to trigger and control tissue regeneration. We have developed an in vitro model to modulate the host response by tuning biomaterials' surface properties through surface modifications techniques as a new strategy for tissue regeneration applications. Results showed tunable surface topography, roughness, wettability, and chemistry by varying treatment type and exposure, allowing for the first time to correlate the effect of these surface properties on cell attachment, morphology, strength and proliferation, as well as proinflammatory (IL-1β, IL-6) and antiflammatory cytokines (TGF-β1, IL-10) secreted in medium, and protein expression of collagen and elastin. Surface microstructuring, derived from chloroform partial etching, increased surface roughness and oxygen content. This resulted in enhanced cell adhesion, strength and proliferation as well as a balance of soluble factors for optimum collagen and elastin synthesis for tissue regeneration. By linking surface parameters to cell activity, we could determine the fate of the regenerated tissue to create successful soft tissue-engineered replacement.

Nanoscopy reveals surface-metallic black phosphorus

DOE PAGES

Abate, Yohannes; Gamage, Sampath; Li, Zhen; ...

2016-10-21

Black phosphorus (BP) is an emerging two-dimensional material with intriguing physical properties. It is highly anisotropic and highly tunable by means of both the number of monolayers and surface doping. Here, we experimentally investigate and theoretically interpret the near-field properties of a-few-atomic-monolayer nanoflakes of BP. We discover near-field patterns of bright outside fringes and a high surface polarizability of nanofilm BP consistent with its surface-metallic, plasmonic behavior at mid-infrared frequencies <1176 cm -1. We conclude that these fringes are caused by the formation of a highly polarizable layer at the BP surface. This layer has a thickness of ~1 nmmore » and exhibits plasmonic behavior. We estimate that it contains free carriers in a concentration of n≈1.1 × 10 20 cm -3. Surface plasmonic behavior is observed for 10–40 nm BP thicknesses but absent for a 4-nm BP thickness. This discovery opens up a new field of research and potential applications in nanoelectronics, plasmonics and optoelectronics.« less

Enhanced mechanical properties and increased corrosion resistance of a biodegradable magnesium alloy by plasma electrolytic oxidation (PEO).

PubMed

White, Leon; Koo, Youngmi; Neralla, Sudheer; Sankar, Jagannathan; Yun, Yeoheung

2016-06-01

We report the enhanced mechanical properties of AZ31 magnesium alloys by plasma electrolytic oxidation (PEO) coating in NaOH, Na 2 SiO 3 , KF and NaH 2 PO 4 ·2H 2 O containing electrolytes. Mechanical properties including wear resistance, surface hardness and elastic modulus were increased for PEO-coated AZ31 Mg alloys (PEO-AZ31). DC polarization in Hank's solution indicating that the corrosion resistance significantly increased for PEO-coating in KF-contained electrolyte. Based on these results, the PEO coating method shows promising potential for use in biodegradable implant applications where tunable corrosion and mechanical properties are needed.

Freestanding palladium nanosheets with plasmonic and catalytic properties

NASA Astrophysics Data System (ADS)

Huang, Xiaoqing; Tang, Shaoheng; Mu, Xiaoliang; Dai, Yan; Chen, Guangxu; Zhou, Zhiyou; Ruan, Fangxiong; Yang, Zhilin; Zheng, Nanfeng

2011-01-01

Ultrathin metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties. Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques, but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.

Elucidation of Peptide-Directed Palladium Surface Structure for Biologically Tunable Nanocatalysts

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

Bedford, Nicholas M.; Ramezani-Dakhel, Hadi; Slocik, Joseph M.

Peptide-enabled synthesis of inorganic nanostructures represents an avenue to access catalytic materials with tunable and optimized properties. This is achieved via peptide complexity and programmability that is missing in traditional ligands for catalytic nanomaterials. Unfortunately, there is limited information available to correlate peptide sequence to particle structure and catalytic activity to date. As such, the application of peptide-enabled nanocatalysts remains limited to trial and error approaches. In this paper, a hybrid experimental and computational approach is introduced to systematically elucidate biomolecule-dependent structure/function relationships for peptide-capped Pd nanocatalysts. Synchrotron X-ray techniques were used to uncover substantial particle surface structural disorder, whichmore » was dependent upon the amino acid sequence of the peptide capping ligand. Nanocatalyst configurations were then determined directly from experimental data using reverse Monte Carlo methods and further refined using molecular dynamics simulation, obtaining thermodynamically stable peptide-Pd nanoparticle configurations. Sequence-dependent catalytic property differences for C-C coupling and olefin hydrogenation were then eluddated by identification of the catalytic active sites at the atomic level and quantitative prediction of relative reaction rates. This hybrid methodology provides a clear route to determine peptide-dependent structure/function relationships, enabling the generation of guidelines for catalyst design through rational tailoring of peptide sequences« less

Combined Thermochromic And Plasmonic: Optical Responses In Novel Nanocomposite Au-VO2 Films Prepared By RF Inverted Cylindrical Magnetron Sputtering

NASA Astrophysics Data System (ADS)

Kana, J. B. Kana; Ndjaka, J. M.; Manyala, N.; Nemraoui, O.; Beye, A. C.; Maaza, M.

2008-09-01

We prepared gold/Vanadium dioxide nanocomposites thin films by the rf reactive inverted cylindrical magnetron sputtering (ICMS) for the first time and report their enhanced surface plasmon resonance (SPR) tunable shift reversibility. ICMS has been attracting much attention for its ability for uniform coating of three-dimensional objects and high-rate deposition of dielectric materials. To investigate the optical properties of gold nanoparticles embedded in an active matrix (VO2) composite film was synthesized on corning glass substrates for several substrate temperatures ranging from 400 °C to 600 °C. The X-ray diffraction results demonstrated that the Au and VO2 were well crystallized. The optical transmission properties were measured from 300nm to 1100nm and the absorption peak due to the surface plasmon resonance (SPR) of Au nanoparticles were observed. Under external temperature stimuli, the tunable reversibility of the SPR shift was observed when the nanocomposites temperature varies from 20 °C to 100 °C. The enhancement of this shift of SPR was observed as the substrate temperature increases and it was found that the shift of SPR increased rapidly with increasing substrate temperature but then remained constant at ˜57 nm for substrate temperature higher than 500 °C.

Elucidation of peptide-directed palladium surface structure for biologically tunable nanocatalysts.

PubMed

Bedford, Nicholas M; Ramezani-Dakhel, Hadi; Slocik, Joseph M; Briggs, Beverly D; Ren, Yang; Frenkel, Anatoly I; Petkov, Valeri; Heinz, Hendrik; Naik, Rajesh R; Knecht, Marc R

2015-05-26

Peptide-enabled synthesis of inorganic nanostructures represents an avenue to access catalytic materials with tunable and optimized properties. This is achieved via peptide complexity and programmability that is missing in traditional ligands for catalytic nanomaterials. Unfortunately, there is limited information available to correlate peptide sequence to particle structure and catalytic activity to date. As such, the application of peptide-enabled nanocatalysts remains limited to trial and error approaches. In this paper, a hybrid experimental and computational approach is introduced to systematically elucidate biomolecule-dependent structure/function relationships for peptide-capped Pd nanocatalysts. Synchrotron X-ray techniques were used to uncover substantial particle surface structural disorder, which was dependent upon the amino acid sequence of the peptide capping ligand. Nanocatalyst configurations were then determined directly from experimental data using reverse Monte Carlo methods and further refined using molecular dynamics simulation, obtaining thermodynamically stable peptide-Pd nanoparticle configurations. Sequence-dependent catalytic property differences for C-C coupling and olefin hydrogenation were then elucidated by identification of the catalytic active sites at the atomic level and quantitative prediction of relative reaction rates. This hybrid methodology provides a clear route to determine peptide-dependent structure/function relationships, enabling the generation of guidelines for catalyst design through rational tailoring of peptide sequences.

Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents.

PubMed

Štengl, Václav; Henych, Jiří; Janoš, Pavel; Skoumal, Miroslav

2016-01-01

Metal oxides have very important applications in many areas of chemistry, physics and materials science; their properties are dependent on the method of preparation, the morphology and texture. Nanostructured metal oxides can exhibit unique characteristics unlike those of the bulk form depending on their morphology, with a high density of edges, corners and defect surfaces. In recent years, methods have been developed for the preparation of metal oxide powders with tunable control of the primary particle size as well as of a secondary particle size: the size of agglomerates of crystallites. One of the many ways to take advantage of unique properties of nanostructured oxide materials is stoichiometric degradation of chemical warfare agents (CWAs) and volatile organic compounds (VOC) pollutants on their surfaces.

The excitonic photoluminescence mechanism and lasing action in band-gap-tunable CdS(1-x)Se(x) nanostructures.

PubMed

Dai, Jun; Zhou, Pengxia; Lu, Junfeng; Zheng, Hongge; Guo, Jiyuan; Wang, Fang; Gu, Ning; Xu, Chunxiang

2016-01-14

Bandgap tunable semiconductor materials have wide application in integrated-optoelectronic and communication devices. The CdS1-xSex ternary semiconductor materials covering green-red bands have been reported previously, but their basic band-gap and optical properties crucial to the performance of the CdS1-xSex-based optoelectronic devices have not been deeply understood. In this paper, we theoretically simulated and discussed the feasibility of bandgap-tunable CdS1-xSex nanomaterials for designing wavelength tunable microlasers. Then we fabricated the CdS1-xSex nanobelts with their band gap ranging from 2.4 to 1.74 eV by adjusting the composition ratio x in the vapor-phase-transport growth process. The temperature-dependent photoluminescence and exciton-related optical constants of the CdS1-xSex nanobelts were carefully demonstrated. Finally, the wavelength-tunable Fabry-Perot lasing in CdS1-xSex nanobelts was obtained, and the Fabry-Perot lasing mechanism was numerically simulated by the FDTD method. The systematic results on the mechanism of the tunable band gap, exciton properties and lasing of the CdS1-xSex nanostructure help us deeply understand the intrinsic optical properties of this material, and will build a strong foundation for future application of green-red wavelength-tunable CdS1-xSex microlasers.

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.

Metal-polymer nanocomposites for stretchable optics and plasmonics

NASA Astrophysics Data System (ADS)

Potenza, Marco A. C.; Minnai, Chloé; Milani, Paolo

2016-12-01

Stretchable and conformable optical devices open very exciting perspectives for the fabrication of systems incorporating diffracting and optical power in a single element and of tunable plasmonic filters and absorbers. The use of nanocomposites obtained by inserting metallic nanoparticles produced in the gas phase into polymeric matrices allows to effectively fabricate cheap and simple stretchable optical elements able to withstand thousands of deformations and stretching cycles without any degradation of their optical properties. The nanocomposite-based reflective optical devices show excellent performances and stability compared to similar devices fabricated with standard techniques. The nanocomposite-based devices can be therefore applied to arbitrary curved non-optical grade surfaces in order to achieve optical power and to minimize aberrations like astigmatism. Examples discussed here include stretchable reflecting gratings, plasmonic filters tunable by mechanical stretching and light absorbers.

Tunable Chiroptical Properties from the Plasmonic Band to Metal-Ligand Charge Transfer Band of the Cysteine Capped Molybdenum Oxide Nanoparticles.

PubMed

Li, Yiwen; Cheng, Jiaji; Li, Jiagen; Zhu, Xi; He, TingChao; Chen, Rui; Tang, Zikang

2018-06-25

Understanding the interactions between a semiconducting nanocrystal surface and chiral anchoring molecules could resolve the mechanism of chirality induction in nanoscale and facilitate the rational design of chiral semiconducting materials for chiroptics. Herein, we present chiral molybdenum oxide nanoparticles in which chirality is transferred via a bio-to-nano approach. With facile controlling on the amount of chiral cysteine molecules under redox treatment, circular dichroism (CD) signals are generated in plasmon region and metal-ligand charge transfer band. The obtained enhanced CD signals with tunable line-shapes illustrate the possibility of using chiral molybdenum oxide nanoparticles as potentials for chiral semiconductor nanosensors, optoelectronics and photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient and Tunable Three-Dimensional Functionalization of Fully Zwitterionic Antifouling Surface Coatings.

PubMed

Lange, Stefanie C; van Andel, Esther; Smulders, Maarten M J; Zuilhof, Han

2016-10-11

To enhance the sensitivity and selectivity of surface-based (bio)sensors, it is of crucial importance to diminish background signals that arise from the nonspecific binding of biomolecules, so-called biofouling. Zwitterionic polymer brushes have been shown to be excellent antifouling materials. However, for sensing purposes, antifouling does not suffice but needs to be combined with the possibility to efficiently modify the brush with recognition units. So far this has been achieved only at the expense of either antifouling properties or binding capacity. Herein we present a conceptually new approach by integrating both characteristics into a single tailor-made monomer: a novel sulfobetaine-based zwitterionic monomer equipped with a clickable azide moiety. Copolymerization of this monomer with a well-established standard sulfobetaine monomer results in highly antifouling surface coatings with a large yet tunable number of clickable groups present throughout the entire brush. Subsequent functionalization of the azido brushes via widely used strain-promoted alkyne azide click reactions yields fully zwitterionic 3D-functionalized coatings with a recognition unit of choice that can be tailored for any specific application. Here we show a proof of principle with biotin-functionalized brushes on Si 3 N 4 that combine excellent antifouling properties with specific avidin binding from a protein mixture. The signal-to-noise ratio is significantly improved over that of traditional chain-end modification of sulfobetaine polymer brushes, even if the azide content is lowered to 1%. This therefore offers a viable approach to the development of biosensors with greatly enhanced performance on any surface.

Size tunable gold nanorods evenly distributed in the channels of mesoporous silica.

PubMed

Li, Zhi; Kübel, Christian; Pârvulescu, Vasile I; Richards, Ryan

2008-06-01

Uniformly distributed gold nanorods in mesoporous silica were synthesized in situ by performing a seed-mediated growth process in the channels of SBA-15 which functions as a hard-template to confine the diameter of gold nanorods. By changing the amount of gold precursor, gold nanorods were prepared with a fixed diameter (6-7 nm) and tunable aspect ratios from 3 to 30. Transmission electron microscope and electron tomography were utilized to visualize the gold nanorods supported on one piece of SBA-15 segment and showed a fairly uniform 3-dimensional distribution of gold nanorods within the SBA-15 channels. The longitudinal plasmon resonances of the gold nanorods/SBA-15 composites analyzed by diffuse reflectance UV-vis spectra were found to be tunable depending on the length of gold nanorods. No significant decrease in surface area and/or pore size of the composite was found after growth, indicating the growth process did not disrupt the open mesoporous structure of SBA-15. The combination of the tunable size of the nanorods and their 3-dimensional distribution within the open supporting matrix makes the gold nanorods/SBA-15 composites interesting candidates to systematically study the influence of the aspect ratio of gold nanorods on their properties and potential applications, i.e., catalyst, optical polarizer, and ultrasensitive medical imaging technique.

Controllable Broadband Optical Transparency and Wettability Switching of Temperature-Activated Solid/Liquid-Infused Nanofibrous Membranes.

PubMed

Manabe, Kengo; Matsubayashi, Takeshi; Tenjimbayashi, Mizuki; Moriya, Takeo; Tsuge, Yosuke; Kyung, Kyu-Hong; Shiratori, Seimei

2016-09-29

Inspired by biointerfaces, such as the surfaces of lotus leaves and pitcher plants, researchers have developed innovative strategies for controlling surface wettability and transparency. In particular, great success has been achieved in obtaining low adhesion and high transmittance via the introduction of a liquid layer to form liquid-infused surfaces. Furthermore, smart surfaces that can change their surface properties according to external stimuli have recently attracted substantial interest. As some of the best-performing smart surface materials, slippery liquid-infused porous surfaces (SLIPSs), which are super-repellent, demonstrate the successful achievement of switchable adhesion and tunable transparency that can be controlled by a graded mechanical stimulus. However, despite considerable efforts, producing temperature-responsive, super-repellent surfaces at ambient temperature and pressure remains difficult because of the use of nonreactive lubricant oil as a building block in previously investigated repellent surfaces. Therefore, the present study focused on developing multifunctional materials that dynamically adapt to temperature changes. Here, we demonstrate temperature-activated solidifiable/liquid paraffin-infused porous surfaces (TA-SLIPSs) whose transparency and control of water droplet movement at room temperature can be simultaneously controlled. The solidification of the paraffin changes the surface morphology and the size of the light-transmission inhibitor in the lubricant layer; as a result, the control over the droplet movement and the light transmittance at different temperatures is dependent on the solidifiable/liquid paraffin mixing ratio. Further study of such temperature-responsive, multifunctional systems would be valuable for antifouling applications and the development of surfaces with tunable optical transparency for innovative medical applications, intelligent windows, and other devices.

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

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

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

DOE PAGES

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

2017-10-23

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes

PubMed Central

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-01-01

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices. PMID:27829663

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes

NASA Astrophysics Data System (ADS)

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-11-01

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices.

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes.

PubMed

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-11-10

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS 2 ) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS 2 and pentacene. The pentacene/MoS 2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices.

Phononic Crystal Tunable via Ferroelectric Phase Transition

NASA Astrophysics Data System (ADS)

Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

2015-09-01

Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

PubMed Central

Walters, Diane M.; Lyubimov, Ivan; de Pablo, Juan J.; Ediger, M. D.

2015-01-01

Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. We apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (Tsubstrate) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by Tsubstrate/Tg, where Tg is the glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form “stable glasses” with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. By showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics. PMID:25831545

Biaxially mechanical tuning of 2-D reversible and irreversible surface topologies through simultaneous and sequential wrinkling.

PubMed

Yin, Jie; Yagüe, Jose Luis; Boyce, Mary C; Gleason, Karen K

2014-02-26

Controlled buckling is a facile means of structuring surfaces. The resulting ordered wrinkling topologies provide surface properties and features desired for multifunctional applications. Here, we study the biaxially dynamic tuning of two-dimensional wrinkled micropatterns under cyclic mechanical stretching/releasing/restretching simultaneously or sequentially. A biaxially prestretched PDMS substrate is coated with a stiff polymer deposited by initiated chemical vapor deposition (iCVD). Applying a mechanical release/restretch cycle in two directions loaded simultaneously or sequentially to the wrinkled system results in a variety of dynamic and tunable wrinkled geometries, the evolution of which is investigated using in situ optical profilometry, numerical simulations, and theoretical modeling. Results show that restretching ordered herringbone micropatterns, created through sequential release of biaxial prestrain, leads to reversible and repeatable surface topography. The initial flat surface and the same wrinkled herringbone pattern are obtained alternatively after cyclic release/restretch processes, owing to the highly ordered structure leaving no avenue for trapping irregular topological regions during cycling as further evidenced by the uniformity of strains distributions and negligible residual strain. Conversely, restretching disordered labyrinth micropatterns created through simultaneous release shows an irreversible surface topology whether after sequential or simultaneous restretching due to creation of irregular surface topologies with regions of highly concentrated strain upon formation of the labyrinth which then lead to residual strains and trapped topologies upon cycling; furthermore, these trapped topologies depend upon the subsequent strain histories as well as the cycle. The disordered labyrinth pattern varies after each cyclic release/restretch process, presenting residual shallow patterns instead of achieving a flat state. The ability to dynamically tune the highly ordered herringbone patterning through mechanical stretching or other actuation makes these wrinkles excellent candidates for tunable multifunctional surfaces properties such as reflectivity, friction, anisotropic liquid flow or boundary layer control.

Directed assembly of colloidal particles for micro/nano photonics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zheng, Yuebing

2017-02-01

Bottom-up fabrication of complex structures with chemically synthesized colloidal particles as building blocks pave an efficient and cost-effective way towards micro/nano photonics with unprecedented functionality and tunability. Novel properties can arise from quantum effects of colloidal particles, as well as inter-particle interactions and spatial arrangement in particle assemblies. Herein, I discuss our recent developments and applications of three types of techniques for directed assembly of colloidal particles: moiré nanosphere lithography (MNSL), bubble-pen lithography (BPL), and optothermal tweezers (OTTs). Specifically, MNSL provides an efficient approach towards creating moiré metasurface with tunable and multiband optical responses from visible to mid-infrared regime. Au moiré metasurfaces have been applied for surface-enhanced infrared spectroscopy, optical capture and patterning of bacteria, and photothermal denaturation of proteins. BPL is developed to pattern a variety of colloidal particles on plasmonic substrates and two-dimensional atomic-layer materials in an arbitrary manner. The laser-directed microbubble captures and immobilizes nanoparticles through coordinated actions of Marangoni convection, surface tension, gas pressure, and substrate adhesion. OTTs are developed to create dynamic nanoparticle assemblies at low optical power. Such nanoparticle assemblies have been used for surface-enhanced Raman spectroscopy for molecular analysis in their native environments.

Tunable optofluidic microring laser based on a tapered hollow core microstructured optical fiber.

PubMed

Li, Zhi-Li; Zhou, Wen-Yuan; Luo, Ming-Ming; Liu, Yan-Ge; Tian, Jian-Guo

2015-04-20

A tunable optofluidic microring dye laser within a tapered hollow core microstructured optical fiber was demonstrated. The fiber core was filled with a microfluidic gain medium plug and axially pumped by a nanosecond pulse laser at 532 nm. Strong radial emission and low-threshold lasing (16 nJ/pulse) were achieved. Lasing was achieved around the surface of the microfluidic plug. Laser emission was tuned by changing the liquid surface location along the tapered fiber. The possibility of developing a tunable laser within the tapered simplified hollow core microstructured optical fiber presents opportunities for developing liquid surface position sensors and biomedical analysis.

Building 3D Layer-by-Layer Graphene-Gold Nanoparticle Hybrid Architecture with Tunable Interlayer Distance

DTIC Science & Technology

2014-06-26

supercapacitors .11 On the other hand, because of the anisotropic graphene structure, it exhibits strong direction- dependent properties, including...GNPs has the advantage of increased surface area for supercapacitor .11 2. EXPERIMENTAL SECTION 2.1. Materials and Instruments. All chemicals and...rectangular, which means that this material has good potential for applications such as supercapacitors .22 In an ideal situation, it can be envisioned that

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

NASA Astrophysics Data System (ADS)

Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

2018-03-01

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

Tunable vertical-cavity surface-emitting laser with feedback to implement a pulsed neural model. 2. High-frequency effects and optical coupling.

PubMed

Romariz, Alexandre R S; Wagner, Kelvin H

2007-07-20

The operation of an optoelectronic dynamic neural model implementation is extended to higher frequencies. A simplified model of thermal effects in vertical-cavity surface-emitting lasers correctly predicts the qualitative changes in the nonlinear mapping implementation with frequency. Experiments and simulations show the expected resonance properties of this model neuron, along with the possibility of other dynamic effects in addition to the ones observed in the original FitzHugh-Nagumo equations. Results of optical coupling between two similar pulsing artificial neurons are also presented.

Electrochemical and optical biosensors based on nanomaterials and nanostructures: a review.

PubMed

Li, Ming; Li, Rui; Li, Chang Ming; Wu, Nianqiang

2011-06-01

Nanomaterials and nanostructures exhibit unique size-tunable and shape-dependent physicochemical properties that are different from those of bulk materials. Advances of nanomaterials and nanostructures open a new door to develop various novel biosensors. The present work has reviewed the recent progress in electrochemical, surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS) and fluorescent biosensors based on nanomaterials and nanostructures. An emphasis is put on the research that demonstrates how the performance of biosensors such as the limit of detection, sensitivity and selectivity is improved by the use of nanomaterials and nanostructures.

Tunable plasmonic properties of Ag-Fe nanoparticles

NASA Astrophysics Data System (ADS)

Bhatia, Pradeep; Verma, S. S.; Sinha, M. M.

2018-05-01

Compatibility problems with electronic processes, limited availability and the high cost of noble metals motivate towards the search of alternative materials to enhance the suitability and efficiency of plasmonic based devices. Alloy or coated bimetallic material configuration is an attractive way to engineer a system possessing tuneable plasmonic properties. Magneto-plasmonic nanoparticles (MPNPs) present the possibility to exhibit their tuneable magnetic and optical properties with extensive applications. We studied the optical properties of Ag-Fe alloy for different compositions. The Localised Surface Plasmon Resonance (LSPR) tunability of Agx-Fe1-x (x = 0.25, 0.50 and 0.75) alloy for nanospheres has been calculated by using Discrete Dipole Approximation (DDA) simulation technique. It is found that absorption and scattering efficiencies of Ag-Fe alloy are found in near ultra violet and visible region of electromagnetic spectrum. Large LSPR shift has been observed in absorption and scattering efficiencies peak for 40 nm and 80 nm size of nanospheres alloys. It is concluded that the LSPR can be tuned by changing nanoparticle size and the alloy composition. Results of the plasmonics properties for Ag-Fe alloy at wavelength 330-545nm (absorption) and 331-507nm (scattering) will open the avenues for new applications in optical imaging, biomedical fields particularly in (calorimetric)-DNA, pentose's, proteins (absorption) and plasmonic-enhanced spectroscopies/spectrometer devices (scattering) for determination of optical densities of cell cultures.

Correlation between tunability and anisotropy in magnetoelectric voltage tunable inductor (VTI).

PubMed

Yan, Yongke; Geng, Liwei D; Zhang, Lujie; Gao, Xiangyu; Gollapudi, Sreenivasulu; Song, Hyun-Cheol; Dong, Shuxiang; Sanghadasa, Mohan; Ngo, Khai; Wang, Yu U; Priya, Shashank

2017-11-22

Electric field modulation of magnetic properties via magnetoelectric coupling in composite materials is of fundamental and technological importance for realizing tunable energy efficient electronics. Here we provide foundational analysis on magnetoelectric voltage tunable inductor (VTI) that exhibits extremely large inductance tunability of up to 1150% under moderate electric fields. This field dependence of inductance arises from the change of permeability, which correlates with the stress dependence of magnetic anisotropy. Through combination of analytical models that were validated by experimental results, comprehensive understanding of various anisotropies on the tunability of VTI is provided. Results indicate that inclusion of magnetic materials with low magnetocrystalline anisotropy is one of the most effective ways to achieve high VTI tunability. This study opens pathway towards design of tunable circuit components that exhibit field-dependent electronic behavior.

Water at surfaces with tunable surface chemistries

NASA Astrophysics Data System (ADS)

Sanders, Stephanie E.; Vanselous, Heather; Petersen, Poul B.

2018-03-01

Aqueous interfaces are ubiquitous in natural environments, spanning atmospheric, geological, oceanographic, and biological systems, as well as in technical applications, such as fuel cells and membrane filtration. Where liquid water terminates at a surface, an interfacial region is formed, which exhibits distinct properties from the bulk aqueous phase. The unique properties of water are governed by the hydrogen-bonded network. The chemical and physical properties of the surface dictate the boundary conditions of the bulk hydrogen-bonded network and thus the interfacial properties of the water and any molecules in that region. Understanding the properties of interfacial water requires systematically characterizing the structure and dynamics of interfacial water as a function of the surface chemistry. In this review, we focus on the use of experimental surface-specific spectroscopic methods to understand the properties of interfacial water as a function of surface chemistry. Investigations of the air-water interface, as well as efforts in tuning the properties of the air-water interface by adding solutes or surfactants, are briefly discussed. Buried aqueous interfaces can be accessed with careful selection of spectroscopic technique and sample configuration, further expanding the range of chemical environments that can be probed, including solid inorganic materials, polymers, and water immiscible liquids. Solid substrates can be finely tuned by functionalization with self-assembled monolayers, polymers, or biomolecules. These variables provide a platform for systematically tuning the chemical nature of the interface and examining the resulting water structure. Finally, time-resolved methods to probe the dynamics of interfacial water are briefly summarized before discussing the current status and future directions in studying the structure and dynamics of interfacial water.

Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces

PubMed Central

Franklin, Daniel; Chen, Yuan; Vazquez-Guardado, Abraham; Modak, Sushrut; Boroumand, Javaneh; Xu, Daming; Wu, Shin-Tson; Chanda, Debashis

2015-01-01

Structural colour arising from nanostructured metallic surfaces offers many benefits compared to conventional pigmentation based display technologies, such as increased resolution and scalability of their optical response with structure dimensions. However, once these structures are fabricated their optical characteristics remain static, limiting their potential application. Here, by using a specially designed nanostructured plasmonic surface in conjunction with high birefringence liquid crystals, we demonstrate a tunable polarization-independent reflective surface where the colour of the surface is changed as a function of applied voltage. A large range of colour tunability is achieved over previous reports by utilizing an engineered surface which allows full liquid crystal reorientation while maximizing the overlap between plasmonic fields and liquid crystal. In combination with imprinted structures of varying periods, a full range of colours spanning the entire visible spectrum is achieved, paving the way towards dynamic pixels for reflective displays. PMID:26066375

Novel Design of Tunable Microlens with Lowered Driving Voltage and Iris with Conformal Antireflective Surface

NASA Astrophysics Data System (ADS)

Almoallem, Yousuf Dawood

Miniaturizing camera systems as required in many new compact devices places a severe restriction on the device size and power consumption. In modern life nowadays, a daily used compact devices like mobile phones and tablets must have some essential components such as single or multiple tiny cameras, as a component of micro-optical systems. In fact, for most of the current miniaturized cameras, optical power is varied based on the traditional situation where the distances between the lenses are mechanically varied relying on old-fashioned voice coil motors or equivalent mechanical drivers. Spatial and power consumption could be scaled down drastically with much faster response time when the revolutionary alternative liquid tunable microlens is utilized after acquiring a good understanding of microfluidics. The influence of interfacial tension as a key metric in controlling microfluidics systems (e.g. liquid microlens) has drawn considerable attention in biomedical, industrial, military fields over the past decade. Tunable microlenses overcome aforementioned concerns of miniaturizing optical systems and present a viable solution by tuning the focal length of lenses via, for example, variation in the lens curvature. Here, a novel tunable dielectrophoretic (DEP)-based tunable lens is presented. Out of many other mechanisms of tuning the lenses, the dielectric mechanism is especially promising since having the capability to achieve a faster response and overcome the electrolysis issue. Nonetheless, DEP usually requires high driving voltage levels. The proposed design is operating with a lowered voltage level and is based on a tunable dielectric liquid lens with a double-sided electrode design, unlike in the conventional scheme with a single-sided electrode design. The design methodology, geometrical analysis, device fabrication, simulation, and testing are demonstrated. Furthermore, the design, simulation, fabrication and characterization of a black-silicon (BSi) based iris is discussed. Reducing undesirable light stray reflections from surfaces is desired in many 3D optical elements, such as supporting optomechanical mounts, irises, optical filters, solar cells, and photolithography underlying layers. BSi (as antireflective nanostructures) provides a potential economic solution which is highly absorptive across the visible spectrum to replace many currently used yet expensive coating materials. Si nanowires (SiNW) were formed using a metal-assisted chemical (MAC) etching process to get a conformal antireflective property on the iris 3D structure including sharp tips and sidewalls. A significant reduction in undesirable light stray reflections was achieved as a result of successful implementation of the conformal antireflective surface on all facets of fabricated irises to eliminate undesirable light stray reflections.

Directed aggregation of carbon nanotube on curved surfaces by polymer induced depletion attraction

NASA Astrophysics Data System (ADS)

Lee, Hsin-Chieh; Jiang, Hong-Ren

2017-12-01

In this study, we show that by chemically grafting macromolecule, polyethylene glycol (PEG), onto CNTs, PEG-CNTs become dispersible in an aqueous solution with tunable depletion interactions with each other. The aggregation of the PEG-CNTs can be controlled by adding PEG polymers into the solution. PEG-CNTs not only aggregate with each other but also tend to aggregate on curved surfaces. Due to this property, we show that PEG-CNTs can be directed to aggregate on particles and patterned surfaces. Depletion interaction induced aggregation of PEG-CNTs may provide a method to place PEG-CNTs on a specific position for different applications ranging from biomedical to industrial usages.

Broadly tunable thin-film intereference coatings: active thin films for telecom applications

NASA Astrophysics Data System (ADS)

Domash, Lawrence H.; Ma, Eugene Y.; Lourie, Mark T.; Sharfin, Wayne F.; Wagner, Matthias

2003-06-01

Thin film interference coatings (TFIC) are the most widely used optical technology for telecom filtering, but until recently no tunable versions have been known except for mechanically rotated filters. We describe a new approach to broadly tunable TFIC components based on the thermo-optic properties of semiconductor thin films with large thermo-optic coefficients 3.6X10[-4]/K. The technology is based on amorphous silicon thin films deposited by plasma-enhanced chemical vapor deposition (PECVD), a process adapted for telecom applications from its origins in the flat-panel display and solar cell industries. Unlike MEMS devices, tunable TFIC can be designed as sophisticated multi-cavity, multi-layer optical designs. Applications include flat-top passband filters for add-drop multiplexing, tunable dispersion compensators, tunable gain equalizers and variable optical attenuators. Extremely compact tunable devices may be integrated into modules such as optical channel monitors, tunable lasers, gain-equalized amplifiers, and tunable detectors.

Tunable electronic and magnetic properties of two-dimensional materials and their one-dimensional derivatives.

PubMed

Zhang, Zhuhua; Liu, Xiaofei; Yu, Jin; Hang, Yang; Li, Yao; Guo, Yufeng; Xu, Ying; Sun, Xu; Zhou, Jianxin; Guo, Wanlin

2016-01-01

Low-dimensional materials exhibit many exceptional properties and functionalities which can be efficiently tuned by externally applied force or fields. Here we review the current status of research on tuning the electronic and magnetic properties of low-dimensional carbon, boron nitride, metal-dichalcogenides, phosphorene nanomaterials by applied engineering strain, external electric field and interaction with substrates, etc, with particular focus on the progress of computational methods and studies. We highlight the similarities and differences of the property modulation among one- and two-dimensional nanomaterials. Recent breakthroughs in experimental demonstration of the tunable functionalities in typical nanostructures are also presented. Finally, prospective and challenges for applying the tunable properties into functional devices are discussed. WIREs Comput Mol Sci 2016, 6:324-350. doi: 10.1002/wcms.1251 For further resources related to this article, please visit the WIREs website. The authors have declared no conflicts of interest for this article.

Mechanically Robust, Ultraelastic Hierarchical Foam with Tunable Properties via 3D Printing

DOE PAGES

Chen, Qiyi; Cao, Peng-Fei; Advincula, Rigoberto C.

2018-04-11

We present a mechanically robust, ultraelastic foam with controlled multiscale architectures and tunable mechanical/conductive performance is fabricated via 3D printing. Hierarchical porosity, including both macro- and microscaled pores, are produced by the combination of direct ink writing (DIW), acid etching, and phase inversion. The thixotropic inks in DIW are formulated by a simple one-pot process to disperse duo nanoparticles (nanoclay and silica nanoparticles) in a polyurethane suspension. The resulting lightweight foam exhibits tailorable mechanical strength, unprecedented elasticity (standing over 1000 compression cycles), and remarkable robustness (rapidly and fully recover after a load more than 20 000 times of its ownmore » weight). Surface coating of carbon nanotubes yields a conductive elastic foam that can be used as piezoresistivity sensor with high sensitivity. For the first time, this strategy achieves 3D printing of elastic foam with controlled multilevel 3D structures and mechanical/conductive properties. In conclusion, the facile ink preparation method can be utilized to fabricate foams of various materials with desirable performance via 3D printing.« less

Mechanically Robust, Ultraelastic Hierarchical Foam with Tunable Properties via 3D Printing

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

Chen, Qiyi; Cao, Peng-Fei; Advincula, Rigoberto C.

We present a mechanically robust, ultraelastic foam with controlled multiscale architectures and tunable mechanical/conductive performance is fabricated via 3D printing. Hierarchical porosity, including both macro- and microscaled pores, are produced by the combination of direct ink writing (DIW), acid etching, and phase inversion. The thixotropic inks in DIW are formulated by a simple one-pot process to disperse duo nanoparticles (nanoclay and silica nanoparticles) in a polyurethane suspension. The resulting lightweight foam exhibits tailorable mechanical strength, unprecedented elasticity (standing over 1000 compression cycles), and remarkable robustness (rapidly and fully recover after a load more than 20 000 times of its ownmore » weight). Surface coating of carbon nanotubes yields a conductive elastic foam that can be used as piezoresistivity sensor with high sensitivity. For the first time, this strategy achieves 3D printing of elastic foam with controlled multilevel 3D structures and mechanical/conductive properties. In conclusion, the facile ink preparation method can be utilized to fabricate foams of various materials with desirable performance via 3D printing.« less

Combined effects of Ag nanoparticles and oxygen plasma treatment on PLGA morphological, chemical, and antibacterial properties.

PubMed

Fortunati, Elena; Mattioli, Samantha; Visai, Livia; Imbriani, Marcello; Fierro, Josè Luis G; Kenny, Josè Maria; Armentano, Ilaria

2013-03-11

The purpose of this study is to investigate the combined effects of oxygen plasma treatments and silver nanoparticles (Ag) on PLGA in order to modulate the surface antimicrobial properties through tunable bacteria adhesion mechanisms. PLGA nanocomposite films, produced by solvent casting with 1 wt % and 7 wt % of Ag nanoparticles were investigated. The PLGA and PLGA/Ag nanocomposite surfaces were treated with oxygen plasma. Surface properties of PLGA were investigated by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), static contact angle (CA), and high resolution X-ray photoelectron spectroscopy (XPS). Antibacterial tests were performed using an Escherichia coli RB (a Gram negative) and Staphylococcus aureus 8325-4 (a Gram positive). The PLGA surface becomes hydrophilic after the oxygen treatment and its roughness increases with the treatment time. The surface treatment and the Ag nanoparticle introduction have a dominant influence on the bacteria adhesion and growth. Oxygen-treated PLGA/Ag systems promote higher reduction of the bacteria viability in comparison to the untreated samples and neat PLGA. The combination of Ag nanoparticles with the oxygen plasma treatment opens new perspectives for the studied biodegradable systems in biomedical applications.

Tuning cell adhesive properties via layer-by-layer assembly of chitosan and alginate

PubMed Central

Silva, Joana M.; García, José R.; Reis, Rui L.; García, Andrés J.; Mano, João F.

2017-01-01

Understanding the mechanisms controlling cell-multilayer film interactions is crucial to the successful engineering of these coatings for biotechnological and biomedical applications. Herein, we present a strategy to tune the cell adhesive properties of multilayers based on marine polysaccharides with and without cross-linking and/or coating with extracellular matrix proteins. Chemical cross-linking of multilayers improved mechanical properties of the coatings but also elicited changes in surface chemistry that alter the adhesion of human umbilical vein endothelial cells. We evaluated a strategy to decouple the mechanical and chemical properties of these films, enabling the transition from cell-adhesive to cell-resistant multilayers. Addition of chitosan/alginate multilayers on top of cross-linked films decreased endothelial cell adhesion, spreading, and proliferation to similar levels as uncross-linked films. Our findings highlight the key role of surface chemistry in cell-multilayer film interactions, and these engineered nanocoatings represent a tunable model of cell adhesive and non-adhesive multilayered films. PMID:28126597

Out-of-Plane Designed Soft Metasurface for Tunable Surface Plasmon Polariton.

PubMed

Liu, Xin; Huang, Zhao; Zhu, Chengkai; Wang, Li; Zang, Jianfeng

2018-02-14

Reliable and repeatable tunability gives functional diversity for reconfigurable plasmonics devices, while reversible and large mechanical deformation enabled by soft materials provides a new way for the global or partial regulation of metadevices. Here, we demonstrate a soft metasurface with an out-of-plane design for tuning the energy of surface plasmon polaritons (SPPs) bloch wave using theory, simulation, and experiments. Our metasurface is composed of two-layered gold nanoribbon arrays (2GNRs) on a soft substrate. The out-of-plane coupling mechanism is systematically analyzed in terms of separation height effect. Moreover, by harnessing mechanical deformation, continuously tunable plasmonic resonance has been achieved in the visible and near-infrared ranges. We further studied the angle-dependent reflection spectra of our metastructure. Compared with its planar counterpart, our soft and two-layered metastructure exhibits diverse tunability and significant field enhancement by out-of-plane interactions. Our approach in designing soft metasurface with out-of-plane structures can be extended to more-complex photonic devices and finds prominent applications such as biosensing, high-density plasmonic circuits, surface-enhanced luminescence, and surface-enhanced Raman scattering.

Combined Thermochromic And Plasmonic: Optical Responses In Novel Nanocomposite Au-VO{sub 2} Films Prepared By RF Inverted Cylindrical Magnetron Sputtering

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

Kana, J. B. Kana; Department of physics, University of Yaounde I, P.O. Box 812 Yaounde; Ndjaka, J. M.

2008-09-23

We prepared gold/Vanadium dioxide nanocomposites thin films by the rf reactive inverted cylindrical magnetron sputtering (ICMS) for the first time and report their enhanced surface plasmon resonance (SPR) tunable shift reversibility. ICMS has been attracting much attention for its ability for uniform coating of three-dimensional objects and high-rate deposition of dielectric materials. To investigate the optical properties of gold nanoparticles embedded in an active matrix (VO{sub 2}) composite film was synthesized on corning glass substrates for several substrate temperatures ranging from 400 deg. C to 600 deg. C. The X-ray diffraction results demonstrated that the Au and VO{sub 2} weremore » well crystallized. The optical transmission properties were measured from 300nm to 1100nm and the absorption peak due to the surface plasmon resonance (SPR) of Au nanoparticles were observed. Under external temperature stimuli, the tunable reversibility of the SPR shift was observed when the nanocomposites temperature varies from 20 deg. C to 100 deg. C. The enhancement of this shift of SPR was observed as the substrate temperature increases and it was found that the shift of SPR increased rapidly with increasing substrate temperature but then remained constant at {approx}57 nm for substrate temperature higher than 500 deg. C.« less

Thermo-optically tunable thin film devices

NASA Astrophysics Data System (ADS)

Domash, Lawrence H.

2003-10-01

We report advances in tunable thin film technology and demonstration of multi-cavity tunable filters. Thin film interference coatings are the most widely used optical technology for telecom filtering, but until recently no tunable versions have been known except for mechanically rotated filters. We describe a new approach to broadly tunable components based on the properties of semiconductor thin films with large thermo-optic coefficients. The technology is based on amorphous silicon deposited by plasma-enhanced chemical vapor deposition (PECVD), a process adapted for telecom applications from its origins in the flat-panel display and solar cell industries. Unlike MEMS devices, tunable thin films can be constructed in sophisticated multi-cavity, multi-layer optical designs.

Tunable Bragg filters with a phase transition material defect layer

DOE PAGES

Wang, Xi; Gong, Zilun; Dong, Kaichen; ...

2016-01-01

We propose an all-solid-state tunable Bragg filter with a phase transition material as the defect layer. Bragg filters based on a vanadium dioxide defect layer sandwiched between silicon dioxide/titanium dioxide Bragg gratings are experimentally demonstrated. Temperature dependent reflection spectroscopy shows the dynamic tunability and hysteresis properties of the Bragg filter. Temperature dependent Raman spectroscopy reveals the connection between the tunability and the phase transition of the vanadium dioxide defect layer. This work paves a new avenue in tunable Bragg filter designs and promises more applications by combining phase transition materials and optical cavities.

Tunable Bragg filters with a phase transition material defect layer

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

Wang, Xi; Gong, Zilun; Dong, Kaichen

We propose an all-solid-state tunable Bragg filter with a phase transition material as the defect layer. Bragg filters based on a vanadium dioxide defect layer sandwiched between silicon dioxide/titanium dioxide Bragg gratings are experimentally demonstrated. Temperature dependent reflection spectroscopy shows the dynamic tunability and hysteresis properties of the Bragg filter. Temperature dependent Raman spectroscopy reveals the connection between the tunability and the phase transition of the vanadium dioxide defect layer. This work paves a new avenue in tunable Bragg filter designs and promises more applications by combining phase transition materials and optical cavities.

Tunable Nanowire Patterning Using Standing Surface Acoustic Waves

PubMed Central

Chen, Yuchao; Ding, Xiaoyun; Lin, Sz-Chin Steven; Yang, Shikuan; Huang, Po-Hsun; Nama, Nitesh; Zhao, Yanhui; Nawaz, Ahmad Ahsan; Guo, Feng; Wang, Wei; Gu, Yeyi; Mallouk, Thomas E.; Huang, Tony Jun

2014-01-01

Patterning of nanowires in a controllable, tunable manner is important for the fabrication of functional nanodevices. Here we present a simple approach for tunable nanowire patterning using standing surface acoustic waves (SSAW). This technique allows for the construction of large-scale nanowire arrays with well-controlled patterning geometry and spacing within 5 seconds. In this approach, SSAWs were generated by interdigital transducers (IDTs), which induced a periodic alternating current (AC) electric field on the piezoelectric substrate and consequently patterned metallic nanowires in suspension. The patterns could be deposited onto the substrate after the liquid evaporated. By controlling the distribution of the SSAW field, metallic nanowires were assembled into different patterns including parallel and perpendicular arrays. The spacing of the nanowire arrays could be tuned by controlling the frequency of the surface acoustic waves. Additionally, we observed 3D spark-shape nanowire patterns in the SSAW field. The SSAW-based nanowire-patterning technique presented here possesses several advantages over alternative patterning approaches, including high versatility, tunability, and efficiency, making it promising for device applications. PMID:23540330

Active Plasmonics: Principles, Structures, and Applications.

PubMed

Jiang, Nina; Zhuo, Xiaolu; Wang, Jianfang

2018-03-28

Active plasmonics is a burgeoning and challenging subfield of plasmonics. It exploits the active control of surface plasmon resonance. In this review, a first-ever in-depth description of the theoretical relationship between surface plasmon resonance and its affecting factors, which forms the basis for active plasmon control, will be presented. Three categories of active plasmonic structures, consisting of plasmonic structures in tunable dielectric surroundings, plasmonic structures with tunable gap distances, and self-tunable plasmonic structures, will be proposed in terms of the modulation mechanism. The recent advances and current challenges for these three categories of active plasmonic structures will be discussed in detail. The flourishing development of active plasmonic structures opens access to new application fields. A significant part of this review will be devoted to the applications of active plasmonic structures in plasmonic sensing, tunable surface-enhanced Raman scattering, active plasmonic components, and electrochromic smart windows. This review will be concluded with a section on the future challenges and prospects for active plasmonics.

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

PubMed

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

Microwave dielectric properties of BNT-BT0.08 thin films prepared by sol-gel technique

NASA Astrophysics Data System (ADS)

Huitema, L.; Cernea, M.; Crunteanu, A.; Trupina, L.; Nedelcu, L.; Banciu, M. G.; Ghalem, A.; Rammal, M.; Madrangeas, V.; Passerieux, D.; Dutheil, P.; Dumas-Bouchiat, F.; Marchet, P.; Champeaux, C.

2016-04-01

We report for the first time the microwave characterization of 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 (BNT-BT0.08) ferroelectric thin films fabricated by the sol-gel method and integrated in both planar and out-of-plane tunable capacitors for agile high-frequency applications and particularly on the WiFi frequency band from 2.4 GHz to 2.49 GHz. The permittivity and loss tangent of the realized BNT-BT0.08 layers have been first measured by a resonant cavity method working at 12.5 GHz. Then, we integrated the ferroelectric material in planar inter-digitated capacitors (IDC) and in out-of-plane metal-insulator-metal (MIM) devices and investigated their specific properties (dielectric tunability and losses) on the whole 100 MHz-15 GHz frequency domain. The 3D finite-elements electromagnetic simulations of the IDC capacitances are fitting very well with their measured responses and confirm the dielectric properties determined with the cavity method. While IDCs are not exhibiting an optimal tunability, the MIM capacitor devices with optimized Ir/MgO(100) bottom electrodes demonstrate a high dielectric tunability, of 30% at 2.45 GHz under applied voltages as low as 10 V, and it is reaching 50% under 20 V voltage bias at the same frequency. These high-frequency properties of the MIM devices integrating the BNT-BT0.08 films, combining a high tunability under low applied voltages indicate a wide integration potential for tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used industrial, scientific, and medical frequency band.

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

DOE PAGES

Dalal, Shakeel S.; Walters, Diane M.; Lyubimov, Ivan; ...

2015-03-23

Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. In this paper, we apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T substrate) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by T substrate/T g, where T g is themore » glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form “stable glasses” with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. Finally, by showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.« less

Melanin and Melanin-Related Polymers as Materials with Biomedical and Biotechnological Applications—Cuttlefish Ink and Mussel Foot Proteins as Inspired Biomolecules

PubMed Central

2017-01-01

The huge development of bioengineering during the last years has boosted the search for new bioinspired materials, with tunable chemical, mechanical, and optoelectronic properties for the design of semiconductors, batteries, biosensors, imaging and therapy probes, adhesive hydrogels, tissue restoration, photoprotectors, etc. These new materials should complement or replace metallic or organic polymers that cause cytotoxicity and some adverse health effects. One of the most interesting biomaterials is melanin and synthetic melanin-related molecules. Melanin has a controversial molecular structure, dependent on the conditions of polymerization, and therefore tunable. It is found in animal hair and skin, although one of the common sources is cuttlefish (Sepia officinalis) ink. On the other hand, mussels synthesize adhesive proteins to anchor these marine animals to wet surfaces. Both melanin and mussel foot proteins contain a high number of catecholic residues, and their properties are related to these groups. Dopamine (DA) can easily polymerize to get polydopamine melanin (PDAM), that somehow shares properties with melanin and mussel proteins. Furthermore, PDAM can easily be conjugated with other components. This review accounts for the main aspects of melanin, as well as DA-based melanin-like materials, related to their biomedical and biotechnological applications. PMID:28718807

Melanin and Melanin-Related Polymers as Materials with Biomedical and Biotechnological Applications-Cuttlefish Ink and Mussel Foot Proteins as Inspired Biomolecules.

PubMed

Solano, Francisco

2017-07-18

The huge development of bioengineering during the last years has boosted the search for new bioinspired materials, with tunable chemical, mechanical, and optoelectronic properties for the design of semiconductors, batteries, biosensors, imaging and therapy probes, adhesive hydrogels, tissue restoration, photoprotectors, etc. These new materials should complement or replace metallic or organic polymers that cause cytotoxicity and some adverse health effects. One of the most interesting biomaterials is melanin and synthetic melanin-related molecules. Melanin has a controversial molecular structure, dependent on the conditions of polymerization, and therefore tunable. It is found in animal hair and skin, although one of the common sources is cuttlefish (Sepia officinalis) ink. On the other hand, mussels synthesize adhesive proteins to anchor these marine animals to wet surfaces. Both melanin and mussel foot proteins contain a high number of catecholic residues, and their properties are related to these groups. Dopamine (DA) can easily polymerize to get polydopamine melanin (PDAM), that somehow shares properties with melanin and mussel proteins. Furthermore, PDAM can easily be conjugated with other components. This review accounts for the main aspects of melanin, as well as DA-based melanin-like materials, related to their biomedical and biotechnological applications.

Controlling Reaction Selectivity through the Surface Termination of Perovskite Catalysts

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

Polo-Garzon, Felipe; Yang, Shi-Ze; Fung, Victor

2017-07-19

Although perovskites have been widely used in catalysis, tuning their surface terminations to control reaction selectivities has not been well established. In this work, we employ multiple surface sensitive techniques to characterize the surface termination (one aspect of surface reconstruction) of SrTiO 3 (STO) after thermal pretreatment (Sr-enrichment) and chemical etching (Ti-enrichment). We show, using the conversion of 2-propanol as a probe reaction, that the surface termination of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivities in a wide range, which are inaccessible using single metal oxides, either SrO or TiO 2. Densitymore » functional theory (DFT) calculations well explain the selectivity tuning and reaction mechanism on different surface terminations of STO. Similar catalytic tunability is also observed on BaZrO 3, highlighting the generality of the finding from this work.« less

Tunable growth of TiO2 nanostructures on Ti substrates

NASA Astrophysics Data System (ADS)

Peng, Xinsheng; Wang, Jingpeng; Thomas, Dan F.; Chen, Aicheng

2005-10-01

A simple and facile method is described to directly synthesize TiO2 nanostructures on titanium substrates by oxidizing Ti foil using small organic molecules as the oxygen source. The effect of reaction temperature and oxygen source on the formation of the TiO2 nanostructures has been studied using scanning electron microscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy and water contact angle measurement. Polycrystalline grains are formed when pure oxygen and formic acid are used as the oxygen source; elongated micro-crystals are produced when water vapour is used as the oxygen source; oriented and aligned TiO2 nanorod arrays are synthesized when ethanol, acetaldehyde or acetone are used as the oxygen source. The growth mechanism of the TiO2 nanostructures is discussed. The diffusion of Ti atoms to the oxide/gas interface via the network of the grain boundaries of the thin oxide layer is the determining factor for the formation of well-aligned TiO2 nanorod arrays. The wetting properties of the TiO2 nanostructured surfaces formed are dictated by their structure, varying from a hydrophilic surface to a strongly hydrophobic surface as the surface structure changes from polycrystalline grains to well-aligned nanorod arrays. This tunable growth of TiO2 nanostructures is desirable for promising applications of TiO2 nanostructures in the development of optical devices, sensors, photo-catalysts and self-cleaning coatings.

Wrinkled silica/titania nanoparticles with tunable interwrinkle distances for efficient utilization of photons in dye-sensitized solar cells.

PubMed

Kang, Jin Soo; Lim, Joohyun; Rho, Won-Yeop; Kim, Jin; Moon, Doo-Sik; Jeong, Juwon; Jung, Dongwook; Choi, Jung-Woo; Lee, Jin-Kyu; Sung, Yung-Eun

2016-08-04

Efficient light harvesting is essential for the realization of high energy conversion efficiency in dye-sensitized solar cells (DSCs). State-of-the-art mesoporous TiO2 photoanodes fall short for collection of long-wavelength visible light photons, and thus there have been efforts on introduction of scattering nanoparticles. Herein, we report the synthesis of wrinkled silica/titania nanoparticles with tunable interwrinkle distances as scattering materials for enhanced light harvesting in DSCs. These particles with more than 20 times larger specific surface area (>400 m(2)/g) compared to the spherical scattering particles (<20 m(2)/g) of the similar sizes gave rise to the dye-loading amounts, causing significant improvements in photocurrent density and efficiency. Moreover, dependence of spectral scattering properties of wrinkled particles on interwrinkle distances, which was originated from difference in overall refractive indices, was observed.

Wavelength-tunable light shaping with cholesteric liquid crystal microlenses.

PubMed

Bayon, Chloé; Agez, Gonzague; Mitov, Michel

2014-06-21

The ability to guide light on the mesoscopic scale is important both scientifically and technologically. Especially relevant is the development of wavelength-tunable light-shaping microdevices. Here we demonstrate the use of cholesteric liquid crystal polygonal textures organized as an array of microlenses for this purpose. The beam shaping is controlled by tuning the wavelength of the incident light in the visible spectrum. By taking advantage of the self-organization property of liquid crystals, the structure of the lens and its optical response are tailored by changing the annealing time of the single layer material during a completely integrated one-step process. The intrinsic helical organization of the layer is the cause of the light shaping and not the shape of the surface as for conventional lenses. A new concept of light manipulation using the structure chirality of liquid crystals is demonstrated, which concerns soft matter photonic circuits to mould the light.

A small mode volume tunable microcavity: Development and characterization

NASA Astrophysics Data System (ADS)

Greuter, Lukas; Starosielec, Sebastian; Najer, Daniel; Ludwig, Arne; Duempelmann, Luc; Rohner, Dominik; Warburton, Richard J.

2014-09-01

We report the realization of a spatially and spectrally tunable air-gap Fabry-Pérot type microcavity of high finesse and cubic-wavelength-scale mode volume. These properties are attractive in the fields of opto-mechanics, quantum sensing, and foremost cavity quantum electrodynamics. The major design feature is a miniaturized concave mirror with atomically smooth surface and radius of curvature as low as 10 μm produced by CO2 laser ablation of fused silica. We demonstrate excellent mode-matching of a focussed laser beam to the microcavity mode and confirm from the frequencies of the resonator modes that the effective optical radius matches the physical radius. With these small radii, we demonstrate wavelength-size beam waists. We also show that the microcavity is sufficiently rigid for practical applications: in a cryostat at 4 K, the root-mean-square microcavity length fluctuations are below 5 pm.

Emergent thermodynamics in a system of macroscopic, chaotic surface waves

NASA Astrophysics Data System (ADS)

Welch, Kyle J.

The properties of conventional materials are inextricably linked with their molecular composition; to make water flow like wine would require changing its molecular identity. To circumvent this restriction, I have constructed and characterized a two-dimensional metafluid, so-called because its constitutive dynamics are derived not from atoms and molecules but from macroscopic, chaotic surface waves excited on a vertically agitated fluid. Unlike in conventional fluids, the viscosity and temperature of this metafluid are independently tunable. Despite this unconventional property, our system is surprisingly consistent with equilibrium thermodynamics, despite being constructed from macroscopic, non-equilibrium elements. As a programmable material, our metafluid represents a new platform on which to study complex phenomena such as self-assembly and pattern formation. We demonstrate one such application in our study of short-chain polymer analogs embedded in our system.

Gold nanoparticles enlighten the future of cancer theranostics

PubMed Central

Guo, Jianfeng; Rahme, Kamil; He, Yan; Li, Lin-Lin; Holmes, Justin D; O’Driscoll, Caitriona M

2017-01-01

Development of multifunctional nanomaterials, one of the most interesting and advanced research areas in the field of nanotechnology, is anticipated to revolutionize cancer diagnosis and treatment. Gold nanoparticles (AuNPs) are now being widely utilized in bio-imaging and phototherapy due to their tunable and highly sensitive optical and electronic properties (the surface plasmon resonance). As a new concept, termed “theranostics,” multifunctional AuNPs may contain diagnostic and therapeutic functions that can be integrated into one system, thereby simultaneously facilitating diagnosis and therapy and monitoring therapeutic responses. In this review, the important properties of AuNPs relevant to diagnostic and phototherapeutic applications such as structure, shape, optics, and surface chemistry are described. Barriers for translational development of theranostic AuNPs and recent advances in the application of AuNPs for cancer diagnosis, photothermal, and photodynamic therapy are discussed. PMID:28883725

Aptamer-functionalized nano-biosensors.

PubMed

Chiu, Tai-Chia; Huang, Chih-Ching

2009-01-01

Nanomaterials have become one of the most interesting sensing materials because of their unique size- and shape-dependent optical properties, high surface energy and surface-to-volume ratio, and tunable surface properties. Aptamers are oligonucleotides that can bind their target ligands with high affinity. The use of nanomaterials that are bioconjugated with aptamers for selective and sensitive detection of analytes such as small molecules, metal ions, proteins, and cells has been demonstrated. This review focuses on recent progress in the development of biosensors by integrating functional aptamers with different types of nanomaterials, including quantum dots, magnetic nanoparticles (NPs), metallic NPs, and carbon nanotubes. Colorimetry, fluorescence, electrochemistry, surface plasmon resonance, surface-enhanced Raman scattering, and magnetic resonance imaging are common detection modes for a broad range of analytes with high sensitivity and selectivity when using aptamer bioconjugated nanomaterials (Apt-NMs). We highlight the important roles that the size and concentration of nanomaterials, the secondary structure and density of aptamers, and the multivalent interactions play in determining the specificity and sensitivity of the nanosensors towards analytes. Advantages and disadvantages of the Apt-NMs for bioapplications are focused.

Single cigar-shaped nanopores functionalized with amphoteric amino acid chains: experimental and theoretical characterization.

PubMed

Ali, Mubarak; Ramirez, Patricio; Nguyen, Hung Quoc; Nasir, Saima; Cervera, Javier; Mafe, Salvador; Ensinger, Wolfgang

2012-04-24

We present an experimental and theoretical characterization of single cigar-shaped nanopores with pH-responsive carboxylic acid and lysine chains functionalized on the pore surface. The nanopore characterization includes (i) optical images of the nanostructure obtained by FESEM; (ii) different chemical procedures for the nanopore preparation (etching time and functionalizations; pH and electrolyte concentration of the external solution) allowing externally tunable nanopore responses monitored by the current-voltage (I-V) curves; and (iii) transport simulations obtained with a multilayer nanopore model. We show that a single, approximately symmetric nanopore can be operated as a reconfigurable diode showing different rectifying behaviors by applying chemical and electrical signals. The remarkable characteristics of the new nanopore are the sharp response observed in the I-V curves, the improved tunability (with respect to previous designs of symmetric nanopores) which is achieved because of the direct external access to the nanostructure mouths, and the broad range of rectifying properties. The results concern both fundamental concepts useful for the understanding of transport processes in biological systems (ion channels) and applications relevant for tunable nanopore technology (information processing and drug controlled release).

Electromagnetically Tunable Fields

DTIC Science & Technology

2008-07-01

constitutive material properties (electrical permittivity, magnetic permeability, and electrical conductivity) of electromagnetically tunable fluids ( ETFs ... trade -offs and operational perspectives of a dielectric coated spherical inverted-F antenna," accepted for IEEE/URSI Int. Symp. Antennas and Propag

One-dimensional carrier confinement in “Giant” CdS/CdSe excitonic nanoshells

DOE PAGES

Razgoniaeva, Natalia; Moroz, Pavel; Yang, Mingrui; ...

2017-05-23

Here, the emerging generation of quantum dot optoelectronic devices offers an appealing prospect of a size-tunable band gap. The confinement-enabled control over electronic properties, however, requires nanoparticles to be sufficiently small, which leads to a large area of interparticle boundaries in a film. Such interfaces lead to a high density of surface traps which ultimately increase the electrical resistance of a solid. To address this issue, we have developed an inverse energy-gradient core/shell architecture supporting the quantum confinement in nanoparticles larger than the exciton Bohr radius. The assembly of such nanostructures exhibits a relatively low surface-to-volume ratio, which was manifestedmore » in this work through the enhanced conductance of solution-processed films. The reported core/shell geometry was realized by growing a narrow gap semiconductor layer (CdSe) on the surface of a wide-gap core material (CdS) promoting the localization of excitons in the shell domain, as was confirmed by ultrafast transient absorption and emission lifetime measurements. The band gap emission of fabricated nanoshells, ranging from 15 to 30 nm in diameter, has revealed a characteristic size-dependent behavior tunable via the shell thickness with associated quantum yields in the 4.4–16.0% range.« less

Fabrication of bio-inspired nitinol alloy surface with tunable anisotropic wetting and high adhesive ability.

PubMed

Tian, Yan L; Zhao, Yue C; Yang, Cheng J; Wang, Fu J; Liu, Xian P; Jing, Xiu B

2018-10-01

In this paper, micro/nano-scale structures were fabricated on nitinol alloy (NiTi) to realize tunable anisotropic wetting and high adhesive capability. Laser texturing and silanization process are utilized to change the morphological and chemical properties of substrates. It is noted that these treated substrates exhibit the joint characteristics of anisotropic wetting and high adhesive capability. In order to investigate the influences of laser-texturing and silanization processes on NiTi, these surfaces were evaluated using scanning electron microscope (SEM), a white light confocal microscope, X-ray photoelectron spectroscopy (XPS) and goniometer. The relationship between water volume and anisotropic wetting was also established. From the experimental testing, we can obtain the following conclusions: (1) the anisotropic wetting characterized by the difference between the water contact angles (WCAs) in the vertical and parallel directions ranges from 0° to 20.3°, which is far more than the value of natural rice leaves. (2) the water sliding angles (WSAs) kept stable at 180°, successfully mimicking the adhesive ability of rose petals. (3) the silanization process could strengthen the hydrophobicity but weaken anisotropic wetting. These bio-inspired NiTi surfaces have a tremendous potential applications such as microfluidic devices, bio-mimetic materials fabrication and lab on chip. Copyright © 2018 Elsevier Inc. All rights reserved.

One-dimensional carrier confinement in “Giant” CdS/CdSe excitonic nanoshells

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

Razgoniaeva, Natalia; Moroz, Pavel; Yang, Mingrui

Here, the emerging generation of quantum dot optoelectronic devices offers an appealing prospect of a size-tunable band gap. The confinement-enabled control over electronic properties, however, requires nanoparticles to be sufficiently small, which leads to a large area of interparticle boundaries in a film. Such interfaces lead to a high density of surface traps which ultimately increase the electrical resistance of a solid. To address this issue, we have developed an inverse energy-gradient core/shell architecture supporting the quantum confinement in nanoparticles larger than the exciton Bohr radius. The assembly of such nanostructures exhibits a relatively low surface-to-volume ratio, which was manifestedmore » in this work through the enhanced conductance of solution-processed films. The reported core/shell geometry was realized by growing a narrow gap semiconductor layer (CdSe) on the surface of a wide-gap core material (CdS) promoting the localization of excitons in the shell domain, as was confirmed by ultrafast transient absorption and emission lifetime measurements. The band gap emission of fabricated nanoshells, ranging from 15 to 30 nm in diameter, has revealed a characteristic size-dependent behavior tunable via the shell thickness with associated quantum yields in the 4.4–16.0% range.« less

Engineering Silver Nanoparticles: Towards a Tunable Antimicrobial

NASA Astrophysics Data System (ADS)

Puppala, Hema Lakshmi

Overwhelming production of commercially available products containing silver nanoparticles (AgNPs) underscores the studies determining their fate in the environment. In order to regulate the use, assess the environmental impact and develop eco-responsible silver products, models that can predict AgNP toxicity based on physicochemical properties are vital. With that vision, this thesis developed well-characterized model libraries of uniform AgNPs stabilized with oleate in the range of 2-45 nm diameter with variable surface coating and investigated the dissolution properties that link AgNP structure to antimicrobial activity. High temperature organic synthesis allowed controlled growth of AgNPs (sigma<15%) by an Ostwald ripening mechanism in the first few hours, and followed by size dependent growth rates yielding uniform nanocrystals. Characterization of these materials revealed a crystalline nature, bidentate binding mode of oleate and non-oxidized pristine silver surface. Phase transfer of these AgNPs from organics to water was facilitated by encapsulation and ligand exchange methods using amphiphilic polymers and methoxy poly (ethylene glycol) (mPEGSH) respectively. Among these surface coatings, steric stabilization by mPEGSH not only helped retain their optical properties but also reduced the dissolution (<1(w/w)%) of AgNPs. This enhanced the stability in various environmentally relevant high ionic strength media (such as Hoaglands, EPA hard water and OECD medium), thereby increasing the shelf life. In addition, size, surface coating, pH of the medium and grafting density of the polymer mediated the dissolution of AgNPs. For instance, the rate of dissolution was decreased by 40% when the polymer coating possessed a mushroom conformation and increased with reducing core size. Analogous to dissolution, physicochemical properties also influenced the antimicrobial activity which were studied by minimum inhibitory concentration (MIC) and bactericidal efficacy assays. For example, surface passivation with mPEGSH prevented the oxidation of active silver atoms on the surface, and resulted in reduced toxicity against E. coli. Moreover citrate stabilized AgNPs when surface modified with mPEGSH had reduced toxicity, which was correlated with residual Ag+ in AgNP solution. Therefore this study demonstrates that processes in the environment that increase stability of AgNPs could make them more persistent due to low dissolution. Furthermore, the size and surface chemistry effects of AgNPs studied here make the intrinsic antimicrobial property of silver tunable and hence more versatile. This work also served as a material support for research on investigating toxicity of AgNPs to C. elegans, Daphnia Magna, Populus and Arabidopsis. In the future, this data will be used to develop nanomaterial bioavailability & environmental exposure (nanoBEE) models that predict the environmental impact of AgNPs.

Tunable electronic and magnetic properties of two‐dimensional materials and their one‐dimensional derivatives

PubMed Central

Zhang, Zhuhua; Liu, Xiaofei; Yu, Jin; Hang, Yang; Li, Yao; Guo, Yufeng; Xu, Ying; Sun, Xu; Zhou, Jianxin

2016-01-01

Low‐dimensional materials exhibit many exceptional properties and functionalities which can be efficiently tuned by externally applied force or fields. Here we review the current status of research on tuning the electronic and magnetic properties of low‐dimensional carbon, boron nitride, metal‐dichalcogenides, phosphorene nanomaterials by applied engineering strain, external electric field and interaction with substrates, etc, with particular focus on the progress of computational methods and studies. We highlight the similarities and differences of the property modulation among one‐ and two‐dimensional nanomaterials. Recent breakthroughs in experimental demonstration of the tunable functionalities in typical nanostructures are also presented. Finally, prospective and challenges for applying the tunable properties into functional devices are discussed. WIREs Comput Mol Sci 2016, 6:324–350. doi: 10.1002/wcms.1251 For further resources related to this article, please visit the WIREs website. Conflict of interest: The authors have declared no conflicts of interest for this article. PMID:27818710

Tuning the surface properties of novel ternary iron(III) fluoride-based catalysts using the template effect of the matrix.

PubMed

Guo, Ying; Lippitz, Andreas; Saftien, Paul; Unger, Wolfgang E S; Kemnitz, Erhard

2015-03-21

Sol-gel prepared ternary FeF3-MgF2 materials have become promising heterogeneous catalysts due to their porosity and surface Lewis/Brønsted acidity (bi-acidity). Despite the good catalytic performance, nanoscopic characterisations of this type of material are still missing and the key factors controlling the surface properties have not yet been identified, impeding both a better understanding and further development of ternary fluoride catalysts. In this study, we characterised the interaction between the bi-acidic component (FeF3) and the matrix (MgF2) on the nano-scale. For the first time, the formation pathway of FeF3-MgF2 was profiled and the template effect of MgF2 during the synthesis process was discovered. Based on these new insights two novel materials, FeF3-CaF2 and FeF3-SrF2, were established, revealing that with decreasing the atomic numbers (from Sr to Mg), the ternary fluorides exhibited increasing surface acidity and surface area but decreasing pore size. These systematic changes gave rise to a panel of catalysts with tuneable surface and bulk properties either by changing the matrix alkaline earth metal fluoride or by adjusting their ratios to Fe or both. The template effect of the alkaline earth metal fluoride matrix was identified as the most probable key factor determining the surface properties and further influencing the catalytic performance in ternary fluoride based catalysts, and paves the way to targeted design of next-generation catalysts with tunable properties.

Controlling Surface Chemistry of Gallium Liquid Metal Alloys to Enhance their Fluidic Properties

NASA Astrophysics Data System (ADS)

Ilyas, Nahid; Cumby, Brad; Cook, Alexander; Durstock, Michael; Tabor, Christopher; Materials; Manufacturing Directorate Team

Gallium liquid metal alloys (GaLMAs) are one of the key components of emerging technologies in reconfigurable electronics, such as tunable radio frequency antennas and electronic switches. Reversible flow of GaLMA in microchannels of these types of devices is hindered by the instantaneous formation of its oxide skin in ambient environment. The oxide film sticks to most surfaces leaving unwanted metallic residues that can cause undesired electronic properties. In this report, residue-free reversible flow of a binary alloy of gallium (eutectic gallium indium) is demonstrated via two types of surface modifications where the oxide film is either protected by an organic thin film or chemically removed. An interface modification layer (alkyl phosphonic acids) was introduced into the microfluidic system to modify the liquid metal surface and protect its oxide layer. Alternatively, an ion exchange membrane was utilized as a 'sponge-like' channel material to store and slowly release small amounts of HCl to react with the surface oxide of the liquid metal. Characterization of these interfaces at molecular level by surface spectroscopy and microscopy provided with mechanistic details for the interfacial interactions between the liquid metal surface and the channel materials.

Synthesis, fractionation, and thin film processing of nanoparticles using the tunable solvent properties of carbon dioxide gas expanded liquids

NASA Astrophysics Data System (ADS)

Anand, Madhu

Nanoparticles have received significant attention because of their unusual characteristics including high surface area to volume ratios. Materials built from nanoparticles possess unique chemical, physical, mechanical and optical properties. Due to these properties, they hold potential in application areas such as catalysts, sensors, semiconductors and optics. At the same time, CO 2 in the form of supercritical fluid or CO2 gas-expanded liquid mixtures has gained significant attention in the area of processing nanostructures. This dissertation focuses on the synthesis and processing of nanoparticles using CO2 tunable solvent systems. Nanoparticle properties depend heavily on their size and, as such, the ability to finely control the size and uniformity of nanoparticles is of utmost importance. Solution based nanoparticle formation techniques are attractive due to their simplicity, but they often result in the synthesis of particles with a wide size range. To address this limitation, a post-synthesis technique has been developed in this dissertation to fractionate polydisperse nanoparticles ( s . = 30%) into monodisperse fractions ( s . = 8%) using tunable physicochemical properties of CO 2 expanded liquids, where CO2 is employed as an antisolvent. This work demonstrates that by controlling the addition of CO2 (pressurization) to an organic dispersion of nanoparticles, the ligand stabilized nanoparticles can be size selectively precipitated within a novel high pressure apparatus that confines the particle precipitation to a specified location on a surface. Unlike current techniques, this CO2 expanded liquid approach provides faster and more efficient particle size separation, reduction in organic solvent usage, and pressure tunable size selection in a single process. To improve our fundamental understanding and to further refine the size separation process, a detailed study has been performed to identify the key parameters enabling size separation of various nanoparticle populations. This study details the influence of various factors on the size separation process, such as the types of nanoparticles, ligand type and solvent type as well as the use of recursive fractionation and the time allowed for settling during each fractionation step. This size selective precipitation technique was also applied to fractionate and separate polydisperse dispersions of CdSe/ZnS semiconductor nanocrystals into very distinct size and color fractions based solely on the pressure tunable solvent properties of CO2 expanded liquids. This size selective precipitation of nanoparticles is achieved by finely tuning the solvent strength of the CO2/organic solvent medium by simply adjusting the applied CO2 pressure. These subtle changes affect the balance between osmotic repulsive and van der Waals attractive forces thereby allowing fractionation of the nanocrystals into multiple narrow size populations. Thermodynamic analysis of nanoparticle size selective fractionation was performed to develop a theoretical model based on the thermodynamic properties of gas expanded liquids. We have used the general phenomenon of nanoparticle precipitation with CO2 expanded liquids to create dodecanethiol stabilized gold nanoparticle thin films. This method utilizes CO2 as an anti-solvent for low defect, wide area gold nanoparticle film formation employing monodisperse gold nanoparticles. Dodecanethiol stabilized gold particles are precipitated from hexane by controllably expanding the solution with carbon dioxide. Subsequent addition of carbon dioxide as a dense supercritical fluid then provides for removal of the organic solvent while avoiding the dewetting effects common to evaporating solvents. Unfortunately, the use of carbon dioxide as a neat solvent in nanoparticles synthesis and processing is limited by the very poor solvent strength of dense phase CO2. As a result, most current techniques employed to synthesize and disperse nanoparticles in neat carbon dioxide require the use of environmentally persistent fluorinated compounds as metal precursors and/or stabilizing ligands. This dissertation presents the first report of the simultaneous synthesis and stabilization of metallic nanoparticles in carbon dioxide solvent without the use of any fluorinated compounds thereby further enabling the use of CO 2 as a green solvent medium in nanomaterials synthesis and processing.

Development of thin-film tunable band-pass filters based hyper-spectral imaging system applied for both surface enhanced Raman scattering and plasmon resonance Rayleigh scattering

NASA Astrophysics Data System (ADS)

Iga, Mitsuhiro; Kakuryu, Nobuyuki; Tanaami, Takeo; Sajiki, Jiro; Isozaki, Katsumi; Itoh, Tamitake

2012-10-01

We describe the development of a hyper-spectral imaging (HSI) system composed of thin-film tunable band-pass filters (TF-TBPFs) and its application to inhomogeneous sample surfaces. Compared with existing HSI systems, the system has a simpler optical arrangement and has an optical transmittance of up to 80% owing to polarization independence. The HSI system exhibits a constant spectral resolution over a spectral window of 80 nm (530 to 610 nm) and tunable spectral resolution from 1.5 to 3.0 nm, and requires only 5.4 s per measurement. Plasmon resonance and surface enhanced Raman scattering (SERS) from inhomogeneous surfaces dispersed with Ag nanoparticles (NP) have been measured with the HSI system. The measurement of multiple Ag NPs is consistent with conventional isolated NP measurements as explained by the electromagnetic mechanism of SERS, demonstrating the validity of the HSI system.

Liquid-assisted tunable metasurface for simultaneous manipulation of surface elastic and acoustic waves

NASA Astrophysics Data System (ADS)

Yuan, Si-Min; Ma, Tian-Xue; Chen, A.-Li; Wang, Yue-Sheng

2018-03-01

A tunable and multi-functional one-dimensional metasurface, which is formed by engraving periodic semi-ellipse grooves on the surface of an aluminum half-space, is proposed in this paper. One characteristic of the metasurface is the manipulation of multi-physical fields, i.e. it could be utilized to manipulate surface elastic and acoustic waves simultaneously. The dispersion curves of the elastic and acoustic waves can be effectively tuned by adding liquids into the grooves. Based on the tunability different applications can be realized by adding different volumes of different liquids into the grooves. As an example, simultaneous rainbow trapping of the surface elastic and acoustic waves is demonstrated in the metasurface. Moreover, a resonant cavity where the elastic and acoustic waves are highly confined is reported. The proposed metasurface paves the way to the design of multi-functional devices for simultaneous control of elastic and acoustic waves.

Sialic acid-triggered macroscopic properties switching on a smart polymer surface

NASA Astrophysics Data System (ADS)

Xiong, Yuting; Li, Minmin; Wang, Hongxi; Qing, Guangyan; Sun, Taolei

2018-01-01

Constructing smart surfaces with responsive polymers capable of dynamically and reversibly changing their chemical and physical properties by responding to the recognition of biomolecules remains a challenging task. And, the key to achieving this purpose relies on the design of polymers to precisely interact with the target molecule and successfully transform the interaction signal into tunable macroscopic properties, further achieve special bio-functions. Herein, inspired by carbohydrate-carbohydrate interaction (CCI) in life system, we developed a three-component copolymer poly(NIPAAm-co-PT-co-Glc) bearing a binding unit glucose (Glc) capable of recognizing sialic acid, a type of important molecular targets for cancer diagnosis and therapy, and reported the sialic acid triggered macroscopic properties switching on this smart polymer surface. Detailed mechanism studies indicated that multiple hydrogen bonding interactions between Glc unit and Neu5Ac destroyed the initial hydrogen bond network of the copolymer, leading to a reversible "contraction-to-swelling" conformational transition of the copolymer chains, accompanied with distinct macroscopic property switching (i.e., surface wettability, morphology, stiffness) of the copolymer film. And these features enabled this copolymer to selectively capture sialic acid-containing glycopeptides from complex protein samples. This work provides an inspiration for the design of novel smart polymeric materials with sensitive responsiveness to sialic acid, which would promote the development of sialic acid-specific bio-devices and drug delivery systems.

Controlling Reaction Selectivity through the Surface Termination of Perovskite Catalysts

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

Polo-Garzon, Felipe; Yang, Shi-Ze; Fung, Victor

2017-07-19

Although well known in the material science field, surface reconstruction of perovskites has not been implemented in heterogeneous catalysis. In this work, we employ multiple surface sensitive techniques to characterize the surface reconstruction of SrTiO3 (STO) after thermal pretreatment (Sr-enrichment) and chemical etching (Ti-enrichment). We show, using the conversion of 2-propanol as a probe reaction, that the surface reconstruction of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivities in a wide range, which are inaccessible using single metal oxides, either SrO or TiO2. Density functional theory (DFT) calculations well explain the selectivity tuningmore » and reaction mechanism on differently reconstructed surfaces of STO. Similar catalytic tunability is also observed on BaZrO3, highlighting the generality of the finding from this work.« less

In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

NASA Astrophysics Data System (ADS)

Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

2017-04-01

Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ. In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage.

Plasmonic Metallurgy Enabled by DNA

DOE PAGES

Ross, Michael B.; Ku, Jessie C.; Lee, Byeongdu; ...

2016-02-05

In this study, mixed silver and gold plasmonic nanoparticle architectures are synthesized using DNA-programmable assembly, unveiling exquisitely tunable optical properties that are predicted and explained both by effective thin-film models and explicit electrodynamic simulations. These data demonstrate that the manner and ratio with which multiple metallic components are arranged can greatly alter optical properties, including tunable color and asymmetric reflectivity behavior of relevance for thin-film applications.

Tunable band gap in Bi(Fe1-xMnx)O3 films

NASA Astrophysics Data System (ADS)

Xu, X. S.; Ihlefeld, J. F.; Lee, J. H.; Ezekoye, O. K.; Vlahos, E.; Ramesh, R.; Gopalan, V.; Pan, X. Q.; Schlom, D. G.; Musfeldt, J. L.

2010-05-01

In order to investigate band gap tunability in polar oxides, we measured the optical properties of a series of Bi(Fe1-xMnx)O3 thin films. The absorption response of the mixed metal solid solutions is approximately a linear combination of the characteristics of the two end members, a result that demonstrates straightforward band gap tunability in this system.

Highly Tunable Hollow Gold Nanospheres: Gaining Size Control and Uniform Galvanic Exchange of Sacrificial Cobalt Boride Scaffolds.

PubMed

Lindley, Sarah A; Cooper, Jason K; Rojas-Andrade, Mauricio D; Fung, Victoria; Leahy, Conor J; Chen, Shaowei; Zhang, Jin Z

2018-04-18

In principle, the diameter and surface plasmon resonance (SPR) frequency of hollow metal nanostructures can be independently adjusted, allowing the formation of targeted photoactivated structures of specific size and optical functionality. Although tunable SPRs have been reported for various systems, the shift in SPR is usually concomitant with a change in particle size. As such, more advanced tunability, including constant diameter with varying SPR or constant SPR with varying diameter, has not been properly achieved experimentally. Herein, we demonstrate this advanced tunability with hollow gold nanospheres (HGNs). HGNs were synthesized through galvanic exchange using cobalt-based nanoparticles (NPs) as sacrificial scaffolds. Co 2 B NP scaffolds were prepared by sodium borohydride nucleation of aqueous cobalt chloride and characterized using UV-vis, dynamic light scattering, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Careful control over the size of the Co 2 B scaffold and its galvanic conversion is essential to realize fine control of the resultant HGN diameter and shell thickness. In pursuit of size control, we introduce B(OH) 4 - (the final product of NaBH 4 hydrolysis) as a growth agent to obtain hydrodynamic diameters ranging from ∼17-85 nm with relative standard deviation <3%. The highly monodisperse Co 2 B NPs were then used as scaffolds for the formation of HGNs. In controlling HGN shell thickness and uniformity, environmental oxygen was shown to affect both the structural and optical properties of the resultant gold shells. With careful control of these key factors, we demonstrate an HGN synthesis that enables independent variation of diameter and shell thickness, and thereby SPR, with unprecedented uniformity. The new synthesis method creates a truly tunable plasmonic nanostructure platform highly desirable for a wide range of applications, including sensing, catalysis, and photothermal therapy.

Phosphate uptake studies of cross-linked chitosan bead materials.

PubMed

Mahaninia, Mohammad H; Wilson, Lee D

2017-01-01

A systematic experimental study is reported that provides a molecular based understanding of cross-linked chitosan beads and their adsorption properties in aqueous solution containing phosphate dianion (HPO 4 2- ) species. Synthetically modified chitosan using epichlorohydrin and glutaraldehyde cross-linkers result in surface modified beads with variable hydrophile-lipophile character and tunable HPO 4 2- uptake properties. The kinetic and thermodynamic adsorption properties of cross-linked chitosan beads with HPO 4 2- species were studied in aqueous solution. Complementary structure and physicochemical characterization of chitosan beads via potentiometry, Raman spectroscopy, DSC, and dye adsorption measurements was carried out to establish structure-property relationships. The maximum uptake (Q m ) of bead systems with HPO 4 2- at equilibrium was 52.1mgg -1 ; whereas, kinetic uptake results for chitosan bead/phosphate systems are relatively rapid (0.111-0.113min -1 ) with an intraparticle diffusion rate-limiting step. The adsorption process follows a multi-step pathway involving inner- and outer-sphere complexes with significant changes in hydration. Phosphate uptake strongly depends on the composition and type of cross-linker used for preparation of chitosan beads. The adsorption isotherms and structural characterization of bead systems illustrate the role of surface charge, hydrophile-lipophile balance, adsorption site accessibility, and hydration properties of the chitosan bead surface. Copyright © 2016 Elsevier Inc. All rights reserved.

Structure and physico-mechanical properties of low temperature plasma treated electrospun nanofibrous scaffolds examined with atomic force microscopy.

PubMed

Chlanda, Adrian; Kijeńska, Ewa; Rinoldi, Chiara; Tarnowski, Michał; Wierzchoń, Tadeusz; Swieszkowski, Wojciech

2018-04-01

Electrospun nanofibrous scaffolds are willingly used in tissue engineering applications due to their tunable mechanical, chemical and physical properties. Additionally, their complex openworked architecture is similar to the native extracellular matrix of living tissue. After implantation such scaffolds should provide sufficient mechanical support for cells. Moreover, it is of crucial importance to ensure sterility and hydrophilicity of the scaffold. For this purpose, a low temperature surface plasma treatment can be applied. In this paper, we report physico-mechanical evaluation of stiffness and adhesive properties of electrospun mats after their exposition to low temperature plasma. Complex morphological and mechanical studies performed with an atomic force microscope were followed by scanning electron microscope imaging and a wettability assessment. The results suggest that plasma treatment can be a useful method for the modification of the surface of polymeric scaffolds in a desirable manner. Plasma treatment improves wettability of the polymeric mats without changing their morphology. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electrodeposition of ZnO nanorod arrays on ZnO substrate with tunable orientation and optical properties.

PubMed

Jehl, Z; Rousset, J; Donsanti, F; Renou, G; Naghavi, N; Lincot, D

2010-10-01

The electrodeposition of ZnO nanorods on ZnO:Al films with different orientations is reported. The influence of the total charge exchanged during electrodeposition on the nanorod's geometry (length, diameter, aspect ratio and surface density) and the optical transmission properties of the nanorod arrays is studied on a [0001]-oriented ZnO:Al substrate. The nanorods are highly vertically oriented along the c axis, following the lattice matching with the substrate. The growth on a [1010] and [1120] ZnO:Al-oriented substrate with c axis parallel to the substrate leads to a systematic deviation angle of 55 degrees from the perpendicular direction. This finding has been explained by the occurrence of a minority orientation with the [1011] planes parallel to the surface, with a preferential growth on corresponding [0001] termination. Substrate crystalline orientation is thereby found to be a major parameter in finely tuning the orientation of the nanorod array. This new approach allows us to optimize the light scattering properties of the films.

Atomic Mechanism of Hybridization-Dependent Surface Reconstruction with Tailored Functionality in Hexagonal Multiferroics.

PubMed

Deng, Shiqing; Cheng, Shaobo; Xu, Changsong; Ge, Binghui; Sun, Xuefeng; Yu, Rong; Duan, Wenhui; Zhu, Jing

2017-08-16

The broken symmetry along with anomalous defect structures and charging conditions at multiferroics surface can alter both crystal structures and electronic configurations, bringing in emergent physical properties. Extraordinary surface states are induced into original mutually coupled order parameters in such strongly correlated oxides, which flourish in diverse properties but remain less explored. Here, we report the peculiar surface ferroelectric states and reconfigurable functionalities driven by the relaxation of surface and consequent changes in O 2p and Y 4d orbital (p-d) hybridization within a representative hexagonal multiferroics, YMnO 3 . An unprecedented surface reconstruction is achieved by tailored p-d hybridization coupling with in-plane oxygen vacancies, which is atomically revealed on the basis of the advantages of state-of-the-art aberration-corrected (scanning) transmission electron microscopy. Further ab initio density functional theory calculations verify the key roles of in-plane oxygen vacancies in modulating polarization properties and electronic structure, which should be regarded as the atomic multiferroic element. This surface configuration is found to induce tunable functionalities, such as surface ferromagnetism and conductivity. Meanwhile, the controversial origin of improper ferroelectricity that is unexpectedly free from critical size has also been atomically unraveled. Our findings provide new insights into the design and implementation of surface chemistry devices by simply controlling the oxygen stoichiometry, greatly advance our understandings of surface science in strongly correlated oxides, and enable exciting innovations and new technological functionality paradigms.

Widely tunable telecom MEMS-VCSEL for terahertz photomixing.

PubMed

Haidar, Mohammad Tanvir; Preu, Sascha; Paul, Sujoy; Gierl, Christian; Cesar, Julijan; Emsia, Ali; Küppers, Franko

2015-10-01

We report frequency-tunable terahertz (THz) generation with a photomixer driven by an ultra-broadband tunable micro-electro-mechanical system vertical-cavity surface-emitting laser (MEMS-VCSEL) and a fixed-wavelength VCSEL, as well as a tunable MEMS-VCSEL mixed with a distributed feedback (DFB) diode. A total frequency span of 3.4 THz is covered in direct detection mode and 3.23 THz in the homodyne mode. The tuning range is solely limited by the dynamic range of the photomixers and the Schottky diode/photoconductor used in the experiment.

Electric-field and strain-tunable electronic properties of MoS2/h-BN/graphene vertical heterostructures.

PubMed

Zan, Wenyan; Geng, Wei; Liu, Huanxiang; Yao, Xiaojun

2016-01-28

Vertical heterostructures of MoS2/h-BN/graphene have been successfully fabricated in recent experiments. Using first-principles analysis, we show that the structural and electronic properties of such vertical heterostructures are sensitive to applied vertical electric fields and strain. The applied electric field not only enhances the interlayer coupling but also linearly controls the charge transfer between graphene and MoS2 layers, leading to a tunable doping in graphene and controllable Schottky barrier height. Applied biaxial strain could weaken the interlayer coupling and results in a slight shift of graphene's Dirac point with respect to the Fermi level. It is of practical importance that the tunable electronic properties by strain and electric fields are immune to the presence of sulfur vacancies, the most common defect in MoS2.

Fabrication and characterization of thermo-responsive gold nanorod assemblies

NASA Astrophysics Data System (ADS)

Bustamante, Gilbert; Carrizales, Katherine; DeLuna, Frank; Large, Nicolas; Ye, Jing Yong

2018-02-01

Advancements in nanotechnology sensors have aided in the detection of subtle, but significant cellular deviations that may mark certain stages of diseases. Gold nanorods (GNRs) are often studied for this purpose due to their tunable optical properties and ease in surface functionalization. The absorption properties of GNRs are governed by the localized surface plasmon resonance (LSPR), which strongly depends on the GNR's aspect ratio and on interparticle interactions. By controlling the coupling of nearby rods, a sensor can be created to respond to temperature fluctuations in the local environment. Here, we fabricated thermo-responsive gold nanorod assemblies by conjugating GNRs in end-to-end or side-by-side configurations using Poly(N-isopropyl acrylamide) (PNIPAM). End-to-end assemblies were fabricated through mixture of GNRs and PNIPAM in DI water. GNRs and PNIPAM were combined in DI water and dimethylformamide (DMF) under sonication to achieve side-by-side configuration. The optical absorption of the assemblies was measured by UV-Visible spectroscopy at different temperatures. As the temperature increased, the polymer contracted and initiated plasmon coupling between the GNRs. The optical spectrum experienced a blue- or red-shift for side-by-side or end-to-end configurations, respectively. Spectral tunability reversal was observed when cooled. Experimental results were verified by finite-difference time-domain (FDTD) calculations, which demonstrated spectral shifts under similar parameters. We present methods for fabrication of thermo-responsive gold nanorods for use as a local thermal nanosensor.

Dynamically tunable interface states in 1D graphene-embedded photonic crystal heterostructure

NASA Astrophysics Data System (ADS)

Huang, Zhao; Li, Shuaifeng; Liu, Xin; Zhao, Degang; Ye, Lei; Zhu, Xuefeng; Zang, Jianfeng

2018-03-01

Optical interface states exhibit promising applications in nonlinear photonics, low-threshold lasing, and surface-wave assisted sensing. However, the further application of interface states in configurable optics is hindered by their limited tunability. Here, we demonstrate a new approach to generate dynamically tunable and angle-resolved interface states using graphene-embedded photonic crystal (GPC) heterostructure device. By combining the GPC structure design with in situ electric doping of graphene, a continuously tunable interface state can be obtained and its tuning range is as wide as the full bandgap. Moreover, the exhibited tunable interface states offer a possibility to study the correspondence between space and time characteristics of light, which is beyond normal incident conditions. Our strategy provides a new way to design configurable devices with tunable optical states for various advanced optical applications such as beam splitter and dynamically tunable laser.

Flatland plasmonics and nanophotonics based on graphene and beyond

NASA Astrophysics Data System (ADS)

Chen, Pai-Yen; Argyropoulos, Christos; Farhat, Mohamed; Gomez-Diaz, J. Sebastian

2017-04-01

In this paper, we review and discuss how the recently discovered two-dimensional (2D) Dirac materials, particularly graphene, may be utilized as new efficient platforms for excitations of propagating and localized surface plasmon polaritons (SPPs) in the terahertz (THz) and mid-infrared (MIR) regions. The surface plasmon modes supported by the metallic 2D materials exhibit tunable plasmon resonances that are essential, yet missing, ingredients needed for THz and MIR photonic and optoelectronic devices. We describe how the atomically thin graphene monolayer and metamaterial structures based on it may tailor and control the spectral, spatial, and temporal properties of electromagnetic radiation. In the same frequency range, the newly unveiled nonlocal, nonlinear, and nonequilibrium electrodynamics in graphene show a variety of nonlinear and amplifying electromagnetic responses, whose potential applications are yet unexplored. With these 2D material platforms, virtually all plasmonic, optoelectronic, and nonlinear functions found in near-infrared (NIR) and visible devices can be analogously transferred to the long-wavelength regime, even with enhanced tunability and new functionalities. The spectral range from THz to MIR is particularly compelling because of the many spectral fingerprints of key chemical, gas, and biological agents, as well as a myriad of remote sensing, imaging, communication, and security applications.

High-speed wavelength switching of tunable MEMS vertical cavity surface emitting laser by ringing suppression

NASA Astrophysics Data System (ADS)

Inoue, Shunya; Nishimura, Shun; Nakahama, Masanori; Matsutani, Akihiro; Sakaguchi, Takahiro; Koyama, Fumio

2018-04-01

For use in wavelength division multiplexing (WDM) with high-speed wavelength routing functions, the fast wavelength switching of tunable lasers is a key function. A tunable MEMS vertical cavity surface emitting laser (VCSEL) is a good candidate as a light source for this purpose. The cantilever in MEMS VCSELs has a high mechanical resonance frequency thanks to its small size, but the switching time is limited by the ringing of the cantilever structure. In this paper, we analyzed the mechanical behavior of a cantilever MEMS mirror and demonstrated ringing-free operation with an engineered voltage signal. The applied voltage waveform was optimized in a two-step format and we experimentally obtained ringing free wavelength switching. We measured the transient response of the wavelength by inserting a tunable filter, exhibiting the settling time of less than 2.5 µs, which corresponds to a half period of the cantilever resonance frequency.

Empirical Evidence for Roughness-Dependent Limit in Observation of Odd-Even Effect in Wetting Properties of Polar Liquids on n-Alkanethiolate Self-Assembled Monolayers.

PubMed

Wang, Zhengjia; Chen, Jiahao; Oyola-Reynoso, Stephanie; Thuo, Martin

2016-08-16

Substrate roughness influences the wetting properties of self-assembled monolayers (SAMs), but details on this dependency at the sub-nanometer level are still lacking. This study investigates the effect of surface roughness on interfacial properties of n-alkanethiolate SAMs, specifically wetting, and confirms the predicted limit to the observation of the odd-even effect in hydrophobicity. This article studies static contact angles of polar and nonpolar probe liquids on a series of n-alkanethiolate SAMs on surfaces with tunable roughness. We prepared Ag surfaces with root-mean-square roughness (Rrms) of ∼0.6-2.2 nm and compared the wetting properties of n-alkanethiolate SAMs fabricated on these surfaces. We measured the static contact angles, θs, formed between SAM and probe liquids [water, glycerol, and hexadecane]. Hexadecane showed an odd-even effect on all surfaces irrespective of the degree of roughness. Polar liquids (water and glycerol), however, showed a dependency on the roughness of the substrate with an odd-even effect observable only on smooth, but not rougher (Rrms ≥ 1.15 nm), surfaces. These results confirm that the previously predicted limit to observation of the odd-even effect in hydrophobicity (here extended to polar liquids) is real. From the results with glycerol, we infer that this limit is not limited just to hydrophobicity but may extend to other polar liquids. Results from hexadecane, however, suggest that this limit may not be a universal property of the SAM.

Magnetically Responsive Superhydrophobic Surface: In Situ Reversible Switching of Water Droplet Wettability and Adhesion for Droplet Manipulation.

PubMed

Yang, Chao; Wu, Lei; Li, Gang

2018-06-13

A smart, magnetically responsive superhydrophobic surface was facilely prepared by combining spray coating and magnetic-field-directed self-assembly. The surface comprised a dense array of magnetorheological elastomer micropillars (MREMPs). Benefitting from the magnetic field-stiffening effect of the MREMPs, the surface exhibited reversible switching of the wettability and adhesion that was responsive to an on/off magnetic field. The wettability and adhesion properties of the surfaces with MREMPs were investigated under different magnetic fields. The results revealed that the adhesion force and sliding behaviors of these surfaces were strongly dependent on the intensity of the applied magnetic field and the mixing ratio of poly(dimethylsiloxane) (PDMS), iron particles, and solvent (in solution) used for preparation of the magnetically responsive superhydrophobic surfaces. The adhesion transition was attributed to the tunable mechanical properties of the MREMPs, which was easily controlled by an external magnetic field. It was also demonstrated that the magnetically responsive superhydrophobic surface can be used as a "mechanical hand" for no-loss liquid droplet transportation. This magnetically responsive superhydrophobic surface not only provides a novel interface for microfluidic control and droplet transportation, but also opens up new avenues for achieving smart liquid-repellent skin, programmable fluid collection and transport, and smart microfluidic devices.

Intermediate stages of surface state formation and collapse of topological protection to transport in Bi2Se3

NASA Astrophysics Data System (ADS)

Banerjee, Abhishek; Rai, Abhishek; Majhi, Kunjalata; Barman, Sudipta Roy; Ganesan, R.; Kumar, P. S. Anil

2017-05-01

Surface states consisting of helical Dirac fermions have been extensively studied in three-dimensional topological insulators. Yet, experiments to date have only investigated fully formed topological surface states (TSS) and it is not known whether preformed or partially formed surface states can exist or what properties they could potentially host. Here, by decorating thin films of Bi2Se3 with nanosized islands of the same material, we show for the first time that not only can surface states exist in various intermediate stages of formation but they exhibit unique properties not accessible in fully formed TSS. These include tunability of the Dirac cone mass, vertical migration of the surface state wave-function and the appearance of mid-gap Rashba-like states as exemplified by our theoretical model for decorated TIs. Our experiments show that an interplay of Rashba and Dirac fermions on the surface leads to an intriguing multi-channel weak anti-localization effect concomitant with an unprecedented tuning of the topological protection to transport. Our work offers a new route to engineer topological surface states involving Dirac-Rashba coupling by nano-scale decoration of TI thin films, at the same time shedding light on the real-space mechanism of surface state formation in general.

Strain-induced tunable negative differential resistance in triangle graphene spirals

NASA Astrophysics Data System (ADS)

Tan, Jie; Zhang, Xiaoming; Liu, Wenguan; He, Xiujie; Zhao, Mingwen

2018-05-01

Using non-equilibrium Green’s function formalism combined with density functional theory calculations, we investigate the significant changes in electronic and transport properties of triangle graphene spirals (TGSs) in response to external strain. Tunable negative differential resistance (NDR) behavior is predicted. The NDR bias region, NDR width, and peak-to-valley ratio can be well tuned by external strain. Further analysis shows that these peculiar properties can be attributed to the dispersion widths of the p z orbitals. Moreover, the conductance of TGSs is very sensitive to the applied stress, which is promising for applications in nanosensor devices. Our findings reveal a novel approach to produce tunable electronic devices based on graphene spirals.

Strain-induced tunable negative differential resistance in triangle graphene spirals.

PubMed

Tan, Jie; Zhang, Xiaoming; Liu, Wenguan; He, Xiujie; Zhao, Mingwen

2018-05-18

Using non-equilibrium Green's function formalism combined with density functional theory calculations, we investigate the significant changes in electronic and transport properties of triangle graphene spirals (TGSs) in response to external strain. Tunable negative differential resistance (NDR) behavior is predicted. The NDR bias region, NDR width, and peak-to-valley ratio can be well tuned by external strain. Further analysis shows that these peculiar properties can be attributed to the dispersion widths of the p z orbitals. Moreover, the conductance of TGSs is very sensitive to the applied stress, which is promising for applications in nanosensor devices. Our findings reveal a novel approach to produce tunable electronic devices based on graphene spirals.

Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

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

Chou Chau, Yuan-Fong, E-mail: chou.fong@ubd.edu.bn; Lim, Chee Ming; Kumara, N. T. R. N.

Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviorsmore » are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.« less

Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic In2S3 Nanocrystals.

PubMed

Berestok, Taisiia; Guardia, Pablo; Portals, Javier Blanco; Estradé, Sònia; Llorca, Jordi; Peiró, Francesca; Cabot, Andreu; Brock, Stephanie L

2018-06-05

Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering easier recyclability and a number of potentially advantageous functionalities, such as tunable band gaps, plasmonic properties, or a magnetic moment. Using high-throughput printing technologies, colloidal NCs can also be supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic, and sensing devices. For both catalytic and technological application, NC surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of In 2 S 3 , both as a colloid and as a supported layer. As a colloid, NCs stabilized by inorganic ligands show the highest photocatalytic activities, which we associate with their large and more accessible surfaces. On the other hand, when NCs are supported on a substrate, their organization becomes an essential parameter determining performance. For instance, NC-based films produced through a gelation process provided five-fold higher photocurrent densities than those obtained from dense films produced by the direct printing of NCs.

Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

NASA Astrophysics Data System (ADS)

Chou Chau, Yuan-Fong; Lim, Chee Ming; Lee, Chuanyo; Huang, Hung Ji; Lin, Chun-Ting; Kumara, N. T. R. N.; Yoong, Voo Nyuk; Chiang, Hai-Pang

2016-09-01

Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviors are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.

Tunable dielectric properties of mesoporous carbon hollow microspheres via textural properties.

PubMed

Xu, Hailong; Yin, Xiaowei; Li, Zhaochen; Liu, Chenglong; Wang, Zeyu; Li, Minghang; Zhang, Litong; Cheng, Laifei

2018-05-04

In this study, mesoporous carbon hollow microspheres (PCHMs) with tunable textural properties have been prepared through a facile hard template etching method. The PCHMs were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Raman spectra, and nitrogen adsorption and desorption systems. Uniform PCHMs with shell thickness ranging from 23 nm to 55 nm are realized. PCHMs with different textural properties can regulate dielectric and electromagnetic (EM) wave absorption effectively. The composite of paraffin wax mixed with 10 wt% PCHMs (the shell thickness of PCHMs is 35 nm) exhibits a minimum coefficient value of -53.8 dB at 8.8 GHz, with a thickness of 3.4 mm. Besides, it is remarkable that the effective absorption bandwidth covers all the X band with as low as a 10 wt% filler ratio, compared with other spherical EM wave absorbers. The excellent EM wave absorption capability of PCHMs can be ascribed to the better impendence matching and strong EM wave attenuation constant based on tunable textural properties. Our results provide a facile strategy to tune dielectric properties of spherical carbon absorbers based on textural properties, and can be extended to other spherical absorbers.

Tunable dielectric properties of mesoporous carbon hollow microspheres via textural properties

NASA Astrophysics Data System (ADS)

Xu, Hailong; Yin, Xiaowei; Li, Zhaochen; Liu, Chenglong; Wang, Zeyu; Li, Minghang; Zhang, Litong; Cheng, Laifei

2018-05-01

In this study, mesoporous carbon hollow microspheres (PCHMs) with tunable textural properties have been prepared through a facile hard template etching method. The PCHMs were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Raman spectra, and nitrogen adsorption and desorption systems. Uniform PCHMs with shell thickness ranging from 23 nm to 55 nm are realized. PCHMs with different textural properties can regulate dielectric and electromagnetic (EM) wave absorption effectively. The composite of paraffin wax mixed with 10 wt% PCHMs (the shell thickness of PCHMs is 35 nm) exhibits a minimum coefficient value of -53.8 dB at 8.8 GHz, with a thickness of 3.4 mm. Besides, it is remarkable that the effective absorption bandwidth covers all the X band with as low as a 10 wt% filler ratio, compared with other spherical EM wave absorbers. The excellent EM wave absorption capability of PCHMs can be ascribed to the better impendence matching and strong EM wave attenuation constant based on tunable textural properties. Our results provide a facile strategy to tune dielectric properties of spherical carbon absorbers based on textural properties, and can be extended to other spherical absorbers.

Nanomaterials modulate stem cell differentiation: biological interaction and underlying mechanisms.

PubMed

Wei, Min; Li, Song; Le, Weidong

2017-10-25

Stem cells are unspecialized cells that have the potential for self-renewal and differentiation into more specialized cell types. The chemical and physical properties of surrounding microenvironment contribute to the growth and differentiation of stem cells and consequently play crucial roles in the regulation of stem cells' fate. Nanomaterials hold great promise in biological and biomedical fields owing to their unique properties, such as controllable particle size, facile synthesis, large surface-to-volume ratio, tunable surface chemistry, and biocompatibility. Over the recent years, accumulating evidence has shown that nanomaterials can facilitate stem cell proliferation and differentiation, and great effort is undertaken to explore their possible modulating manners and mechanisms on stem cell differentiation. In present review, we summarize recent progress in the regulating potential of various nanomaterials on stem cell differentiation and discuss the possible cell uptake, biological interaction and underlying mechanisms.

Self-alignment of plasmonic gold nanorods in reconfigurable anisotropic fluids for tunable bulk metamaterial applications.

PubMed

Liu, Qingkun; Cui, Yanxia; Gardner, Dennis; Li, Xin; He, Sailing; Smalyukh, Ivan I

2010-04-14

We demonstrate the bulk self-alignment of dispersed gold nanorods imposed by the intrinsic cylindrical micelle self-assembly in nematic and hexagonal liquid crystalline phases of anisotropic fluids. External magnetic field and shearing allow for alignment and realignment of the liquid crystal matrix with the ensuing long-range orientational order of well-dispersed plasmonic nanorods. This results in a switchable polarization-sensitive plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The device-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of properties arising from combining the switchable nanoscale structure of anisotropic fluids with the surface plasmon resonance properties of the plasmonic nanorods.

Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties

NASA Astrophysics Data System (ADS)

Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

2015-03-01

Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.

Programming the Assembly of Unnatural Materials with Nucleic Acids

NASA Astrophysics Data System (ADS)

Mirkin, Chad

Nature directs the assembly of enormously complex and highly functional materials through an encoded class of biomolecules, nucleic acids. The establishment of a similarly programmable code for the construction of synthetic, unnatural materials would allow researchers to impart functionality by precisely positioning all material components. Although it is exceedingly difficult to control the complex interactions between atomic and molecular species in such a manner, interactions between nanoscale components can be directed through the ligands attached to their surface. Our group has shown that nucleic acids can be used as highly programmable surface ligands to control the spacing and symmetry of nanoparticle building blocks in structurally sophisticated and functional materials. These nucleic acids function as programmable ``bonds'' between nanoparticle ``atoms,'' analogous to a nanoscale genetic code for assembling materials. The sequence and length tunability of nucleic acid bonds has allowed us to define a powerful set of design rules for the construction of nanoparticle superlattices with more than 30 unique lattice symmetries, tunable defect structures and interparticle spacings, and several well-defined crystal habits. Further, the nature of the nucleic acid bond enables an additional level of structural control: temporal regulation of dynamic material response to external biomolecular and chemical stimuli. This control allows for the reversible transformation between thermodynamic states with different crystal symmetries, particle stoichiometries, thermal stabilities, and interparticle spacings on demand. Notably, our unique genetic approach affords functional nanoparticle architectures that, among many other applications, can be used to systematically explore and manipulate optoelectronic material properties, such as tunable interparticle plasmonic interactions, microstructure-directed energy emission, and coupled plasmonic and photonic modes.

Recent advances of mesoporous materials in sample preparation.

PubMed

Zhao, Liang; Qin, Hongqiang; Wu, Ren'an; Zou, Hanfa

2012-03-09

Sample preparation has been playing an important role in the analysis of complex samples. Mesoporous materials as the promising adsorbents have gained increasing research interest in sample preparation due to their desirable characteristics of high surface area, large pore volume, tunable mesoporous channels with well defined pore-size distribution, controllable wall composition, as well as modifiable surface properties. The aim of this paper is to review the recent advances of mesoporous materials in sample preparation with emphases on extraction of metal ions, adsorption of organic compounds, size selective enrichment of peptides/proteins, specific capture of post-translational peptides/proteins and enzymatic reactor for protein digestion. Copyright © 2011 Elsevier B.V. All rights reserved.

Injectable Biodegradable Polyurethane Scaffolds with Release of Platelet-derived Growth Factor for Tissue Repair and Regeneration

PubMed Central

Hafeman, Andrea E.; Li, Bing; Yoshii, Toshitaka; Zienkiewicz, Katarzyna; Davidson, Jeffrey M.; Guelcher, Scott A.

2013-01-01

Purpose The purpose of this work was to investigate the effects of triisocyanate composition on the biological and mechanical properties of biodegradable, injectable polyurethane scaffolds for bone and soft tissue engineering. Methods Scaffolds were synthesized using reactive liquid molding techniques, and were characterized in vivo in a rat subcutaneous model. Porosity, dynamic mechanical properties, degradation rate, and release of growth factors were also measured. Results Polyurethane scaffolds were elastomers with tunable damping properties and degradation rates, and they supported cellular infiltration and generation of new tissue. The scaffolds showed a two-stage release profile of platelet-derived growth factor, characterized by a 75% burst release within the first 24 h and slower release thereafter. Conclusions Biodegradable polyurethanes synthesized from triisocyanates exhibited tunable and superior mechanical properties compared to materials synthesized from lysine diisocyanates. Due to their injectability, biocompatibility, tunable degradation, and potential for release of growth factors, these materials are potentially promising therapies for tissue engineering. PMID:18516665

X-ray photoemission analysis of clean and carbon monoxide-chemisorbed platinum(111) stepped surfaces using a curved crystal

DOE PAGES

Walter, Andrew L.; Schiller, Frederik; Corso, Martina; ...

2015-11-12

Surface chemistry and catalysis studies could significantly gain from the systematic variation of surface active sites, tested under the very same conditions. Curved crystals are excellent platforms to perform such systematics, which may in turn allow to better resolve fundamental properties and reveal new phenomena. This is demonstrated here for the carbon monoxide/platinum system. We curve a platinum crystal around the high-symmetry (111) direction and carry out photoemission scans on top. This renders the spatial core-level imaging of carbon monoxide adsorbed on a 'tunable' vicinal surface, allowing a straightforward visualization of the rich chemisorption phenomenology at steps and terraces. Throughmore » such photoemission images we probe a characteristic elastic strain variation at stepped surfaces, and unveil subtle stress-release effects on clean and covered vicinal surfaces. Lastly, these results offer the prospect of applying the curved surface approach to rationally investigate the chemical activity of surfaces under real pressure conditions.« less

X-ray photoemission analysis of clean and carbon monoxide-chemisorbed platinum(111) stepped surfaces using a curved crystal

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

Walter, Andrew L.; Schiller, Frederik; Corso, Martina

Surface chemistry and catalysis studies could significantly gain from the systematic variation of surface active sites, tested under the very same conditions. Curved crystals are excellent platforms to perform such systematics, which may in turn allow to better resolve fundamental properties and reveal new phenomena. This is demonstrated here for the carbon monoxide/platinum system. We curve a platinum crystal around the high-symmetry (111) direction and carry out photoemission scans on top. This renders the spatial core-level imaging of carbon monoxide adsorbed on a 'tunable' vicinal surface, allowing a straightforward visualization of the rich chemisorption phenomenology at steps and terraces. Throughmore » such photoemission images we probe a characteristic elastic strain variation at stepped surfaces, and unveil subtle stress-release effects on clean and covered vicinal surfaces. Lastly, these results offer the prospect of applying the curved surface approach to rationally investigate the chemical activity of surfaces under real pressure conditions.« less

Tunable Nitride Josephson Junctions.

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

Missert, Nancy A.; Henry, Michael David; Lewis, Rupert M.

We have developed an ambient temperature, SiO 2/Si wafer - scale process for Josephson junctions based on Nb electrodes and Ta x N barriers with tunable electronic properties. The films are fabricated by magnetron sputtering. The electronic properties of the Ta xN barriers are controlled by adjusting the nitrogen flow during sputtering. This technology offers a scalable alternative to the more traditional junctions based on AlO x barriers for low - power, high - performance computing.

Chemical Routes to Ceramics with Tunable Properties and Structures: Chemical Routes to Nano and Micro-Structured Ceramics

DTIC Science & Technology

2009-12-20

condensations, ordered macroporous arrays of titania , zirconia, and alumina . Other work employing the silica templates has yielded macroporous carbons...Final 3. DATES COVERED (From - To) 05/01/05-09/30/09 4. TITLE AND SUBTITLE Chemical Routes to Ceramics with Tunable Properties and...ORGANIZATION REPORT NUMBER 9-2009 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) Air Force Office of Scientific Research Ceramic and

Plasmonic Metallurgy Enabled by DNA.

PubMed

Ross, Michael B; Ku, Jessie C; Lee, Byeongdu; Mirkin, Chad A; Schatz, George C

2016-04-13

Mixed silver and gold plasmonic nanoparticle architectures are synthesized using DNA-programmable assembly, unveiling exquisitely tunable optical properties that are predicted and explained both by effective thin-film models and explicit electrodynamic simulations. These data demonstrate that the manner and ratio with which multiple metallic components are arranged can greatly alter optical properties, including tunable color and asymmetric reflectivity behavior of relevance for thin-film applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A silk-based scaffold platform with tunable architecture for engineering critically-sized tissue constructs.

PubMed

Wray, Lindsay S; Rnjak-Kovacina, Jelena; Mandal, Biman B; Schmidt, Daniel F; Gil, Eun Seok; Kaplan, David L

2012-12-01

In the field of tissue engineering and regenerative medicine there is significant unmet need for critically-sized, fully degradable biomaterial scaffold systems with tunable properties for optimizing tissue formation in vitro and tissue regeneration in vivo. To address this need, we have developed a silk-based scaffold platform that has tunable material properties, including localized and bioactive functionalization, degradation rate, and mechanical properties and that provides arrays of linear hollow channels for delivery of oxygen and nutrients throughout the scaffold bulk. The scaffolds can be assembled with dimensions that range from millimeters to centimeters, addressing the need for a critically-sized platform for tissue formation. We demonstrate that the hollow channel arrays support localized and confluent endothelialization. This new platform offers a unique and versatile tool for engineering 'tailored' scaffolds for a range of tissue engineering and regenerative medicine needs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Magnetic-plasmonic multilayered nanorods

NASA Astrophysics Data System (ADS)

Thumthan, Orathai

Multilayered nanorods which consist of alternating magnetic layers separated by Au layers combine two distinctive properties, magnetic properties and surface plasmonic resonance (SPR) properties into one nano-entity. Their magnetic properties are tunable by changing the layer thickness, varying from single domain to superparamagnetic state. Superparamagnetic is a key requirement for magnetic nanoparticles for bioapplications. Superparamagnetic nanoparticles exhibit high magnetic moments at low applied magnetic field while retain no magnetic moments when magnetic field is removed preventing them from aggregation due to magnetic attraction. Au layers in the nanorods provide anchorage sites for functional group attachment. Also, Au nanodisks exhibit SPR properties. The SPR peak can be tuned from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. In this research, there are three types of multilayered nanorod have been fabricated: Au/NiFe nanorods, Au/Fe nanorods, and Au/Co nanorods. These magnetic nanorods were fabricated by templated electrodeposition into the channels in Anodic Aluminum Oxide (AAO) membrane. The setup for AAO fabrication was developed as a part of this research. Our fabricated AAO membrane has channels with a diameter ranging from 40nm to 80 nm and a thickness of 10um to 12um. Magnetic properties of nanorods such as saturation field, saturation moment, coercivity and remanence are able to manipulate through their shape anisotropy. The magnetization will be easier in long axis rather than short axis of particle. In addition, Au nanodisks in the nanorod structure are not only serving as anchorage sites for functional groups but also provide SPR properties. Under irradiation of light Au nanodisks strongly absorb light at SPR frequency which ranging from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. The SPR tunability of nanorods in near-infrared region can be used in in-vivo biomedical applications such as photo thermal therapy because tissue has an absorption maximum in the infrared range. The magnetic nanorods were explored for the following two applications: 1) as active component orientation-tunable ferrogel for cell culture matrix, 2) as MRI contrast agent. The results show that Au/NiFe magnetic nanorods can be aligned along applied magnetic field. Using MTT assay for 3T3 fibroblast cells, the biocompatibility of Au/Co nanorods was investigated. It shows that cell proliferation after 72 hours of incubation with nanorods decreases as the concentration of nanorods increases. However, cell viability quantified by counting dead cell/live cell reveals that only few cells died after three days of incubation. Au/Co multilayered nanorods were tested as T2 MRI-contrast agent, and a very large relaxivity was observed. In summary, we have successfully fabricated multilayered nanorods with tunability in both magnetic and SPR properties. These nanorods can potentially be used in biological and biomedical fields.

Mineral concentration dependent modulation of mechanical properties of bone-inspired bionanocomposite scaffold

NASA Astrophysics Data System (ADS)

Biswas, Abhijit; Ovaert, Timothy C.; Slaboch, Constance; Zhao, He; Bayer, Ilker S.; Biris, Alexandru S.; Wang, Tao

2011-07-01

We demonstrate tunable mechanical properties of bone-inspired bionanocomposite scaffolds while maintaining the required viscoelasticity. Mechanical properties such as hardness and elastic modulus of the bionanocomposite scaffolds were controlled by varying mineral concentrations of the bioscaffold. In particular, higher calcium and oxygen contents in the bioscaffold resulted in a significant enhancement in hardness and modulus of the bionanocomposite. Moreover, the phosphorous content appeared to be a determining factor in the hardness and mechanical properties of the bionanocomposites. These results open up the possibility of designing new engineered biocompatible nanoscaffolds with desired and tunable biomimetic functions and biomechanical properties with significant potential for advanced bone tissue engineering platforms and bone substitutes.

Majorana fermions from Landau quantization in a superconductor and topological-insulator hybrid structure.

PubMed

Tiwari, Rakesh P; Zülicke, U; Bruder, C

2013-05-03

We show that the interplay of cyclotron motion and Andreev reflection experienced by massless-Dirac-like charge carriers in topological-insulator surface states generates a Majorana-particle excitation. On the basis of an envelope-function description of the Dirac-Andreev edge states, we discuss the kinematic properties of the Majorana mode and find them to be tunable by changing the superconductor's chemical potential and/or the magnitude of the perpendicular magnetic field. Our proposal opens up new possibilities for studying Majorana fermions in a controllable setup.

Tunable Micro- and Nanomechanical Resonators

PubMed Central

Zhang, Wen-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

2015-01-01

Advances in micro- and nanofabrication technologies have enabled the development of novel micro- and nanomechanical resonators which have attracted significant attention due to their fascinating physical properties and growing potential applications. In this review, we have presented a brief overview of the resonance behavior and frequency tuning principles by varying either the mass or the stiffness of resonators. The progress in micro- and nanomechanical resonators using the tuning electrode, tuning fork, and suspended channel structures and made of graphene have been reviewed. We have also highlighted some major influencing factors such as large-amplitude effect, surface effect and fluid effect on the performances of resonators. More specifically, we have addressed the effects of axial stress/strain, residual surface stress and adsorption-induced surface stress on the sensing and detection applications and discussed the current challenges. We have significantly focused on the active and passive frequency tuning methods and techniques for micro- and nanomechanical resonator applications. On one hand, we have comprehensively evaluated the advantages and disadvantages of each strategy, including active methods such as electrothermal, electrostatic, piezoelectrical, dielectric, magnetomotive, photothermal, mode-coupling as well as tension-based tuning mechanisms, and passive techniques such as post-fabrication and post-packaging tuning processes. On the other hand, the tuning capability and challenges to integrate reliable and customizable frequency tuning methods have been addressed. We have additionally concluded with a discussion of important future directions for further tunable micro- and nanomechanical resonators. PMID:26501294

On a Road to "Soft" Optical MEMS

NASA Astrophysics Data System (ADS)

Yang, Shu; Mach, Peter; Krupenkin, Tom

2003-03-01

A phenomenon of electrowetting has been applied to the actuation of micro-optical devices. The devices use small droplets of transparent conductive liquids to manipulate light in a useful way. The form and position of these droplets is controlled by the applied voltage. Both fiber based and open space optical devices are demonstrated. As an example of an open space optical device, a tunable liquid microlens capable of adjusting its focal length and lateral position is discussed. The microlens consists of a droplet of a transparent conductive liquid placed on a dielectric substrate with underlying electrodes. By varying the voltage applied to the structure, both the position and curvature of microlens can be reversibly changed. Similarly, electrowetting actuation of fluids in micro channels is employed to provide dynamic and reversible tuning of the optical fiber structures. When combined with in-fiber gratings or etched fibers this approach yields tunable broadband and narrowband filters with a large dynamic range. Both the surface and bulk properties of the materials are found important to control the device performance. Fundamental problems, such as stick-slip behavior and contact angle hysteresis associated with the surface roughness and surface contamination, are studied to optimize the choice of dielectric materials and their coatings. Some of the possible ways to control these phenomena are outlined. Several potential applications of the proposed approach are also discussed.

Graphene-based porous materials with tunable surface area and CO2 adsorption properties synthesized by fluorine displacement reaction with various diamines.

PubMed

Li, Baoyin; Fan, Kun; Ma, Xin; Liu, Yang; Chen, Teng; Cheng, Zheng; Wang, Xu; Jiang, Jiaxing; Liu, Xiangyang

2016-09-15

A mild, operationally simple and controllable protocol for preparing graphene-based porous materials is essential to achieve a good pore-design development. In this paper, graphene-based porous materials with tunable surface area were constructed by the intercalation of fluorinated graphene (FG) based on the reaction of reactive CF bonds attached to graphene sheets with various amine-terminated molecules. In the porous materials, graphene sheets are like building blocks, and the diamines covalently grafted onto graphene framework act as pillars. Various diamines are successfully grafted onto graphene sheets, but the grafting ratio of diamines and reduction degree of FG differ greatly and depend on the chemical reactivity of diamines. Pillared diamine molecules chemically anchor at one end and are capable of undergoing a different reaction on the other end, resulting in three different conformations of graphene derivatives. Nitrogen sorption isotherms revealed that the surface area and pore distribution of the obtained porous materials depend heavily on the size and structure of diamine pillars. CO2 uptake capacity characterization showed that ethylenediamine intercalated FG achieved a high CO2 uptake density of 18.0 CO2 molecules per nm(2) at 0°C and 1.1bars, and high adsorption heat, up to 46.1kJmol(-1) at zero coverage. Copyright © 2016 Elsevier Inc. All rights reserved.

In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

PubMed

Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

2014-11-26

Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents.

Bioinspired fabrication of hierarchically structured, pH-tunable photonic crystals with unique transition.

PubMed

Yang, Qingqing; Zhu, Shenmin; Peng, Wenhong; Yin, Chao; Wang, Wanlin; Gu, Jiajun; Zhang, Wang; Ma, Jun; Deng, Tao; Feng, Chuanliang; Zhang, Di

2013-06-25

We herein report a new class of photonic crystals with hierarchical structures, which are of color tunability over pH. The materials were fabricated through the deposition of polymethylacrylic acid (PMAA) onto a Morpho butterfly wing template by using a surface bonding and polymerization route. The amine groups of chitosan in Morpho butterfly wings provide reaction sites for the MAA monomer, resulting in hydrogen bonding between the template and MAA. Subsequent polymerization results in PMAA layers coating homogenously on the hierarchical photonic structures of the biotemplate. The pH-induced color change was detected by reflectance spectra as well as optical observation. A distinct U transition with pH was observed, demonstrating PMAA content-dependent properties. The appearance of the unique U transition results from electrostatic interaction between the -NH3(+) of chitosan and the -COO(-) groups of PMAA formed, leading to a special blue-shifted point at the pH value of the U transition, and the ionization of the two functional groups in the alkali and acid environment separately, resulting in a red shift. This work sets up a strategy for the design and fabrication of tunable photonic crystals with hierarchical structures, which provides a route for combining functional polymers with biotemplates for wide potential use in many fields.

Tunable elastin-like polypeptide hollow sphere as a high payload and controlled delivery gene depot.

PubMed

Dash, Biraja C; Mahor, Sunil; Carroll, Oliver; Mathew, Asha; Wang, Wenxin; Woodhouse, Kimberly A; Pandit, Abhay

2011-06-30

Self-assembly driven processes can be utilized to produce a variety of nanostructures useful for various in vitro and in vivo applications. Characteristics such as size, stability, biocompatibility, high therapeutic loading and controlled delivery of these nanostructures are particularly crucial in relation to in vivo applications. In this study, we report the fabrication of tunable monodispersed elastin-like polypeptide (ELP) hollow spheres of 100, 300, 500 and 1000 nm by exploiting the self-assembly property and net positive charge of ELP. The microbial transglutaminase (mTGase) cross-linking provided robustness and stability to the hollow spheres while maintaining surface functional groups for further modifications. The resulting hollow spheres showed a higher loading efficiency of plasmid DNA (pDNA) by using polyplex (~70 μg pDNA/mg of hollow sphere) than that of self-assembled ELP particles and demonstrated controlled release triggered by protease and elastase. Moreover, polyplex-loaded hollow spheres showed better cell viability than polyplex alone and yielded higher luciferase expression by providing protection against endosomal degradation. Overall, the monodispersed, tunable hollow spheres with a capability of post-functionalization can provide an exciting new opportunity for use in a range of therapeutic and diagnostic applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Single crystalline thin films as a novel class of electrocatalysts

DOE PAGES

Snyder, Joshua; Markovic, Nenad; Stamenkovic, Vojislav

2013-01-01

The ubiquitous use of single crystal metal electrodes has garnered invaluable insight into the relationship between surface atomic structure and functional electrochemical properties. But, the sensitivity of their electrochemical response to surface orientation and the amount of precious metal required can limit their use. We present here a generally applicable procedure for producing thin metal films with a large proportion of atomically flat (111) terraces without the use of an epitaxial template. Thermal annealing in a controlled atmosphere induces long-range ordering of magnetron sputtered thin metal films deposited on an amorphous substrate. The ordering transition in these thin metal filmsmore » yields characteristic (111) electrochemical signatures with minimal amount of material and provides an adequate replacement for oriented bulk single crystals. Our procedure can be generalized towards a novel class of practical multimetallic thin film based electrocatalysts with tunable near-surface compositional profile and morphology. Annealing of atomically corrugated sputtered thin film Pt-alloy catalysts yields an atomically smooth structure with highly crystalline, (111)-like ordered and Pt segregated surface that displays superior functional properties, bridging the gap between extended/bulk surfaces and nanoscale systems.« less

Titanium oxide as substrate for neural cell growth.

PubMed

Carballo-Vila, Mónica; Moreno-Burriel, Berta; Chinarro, Eva; Jurado, José R; Casañ-Pastor, Nieves; Collazos-Castro, Jorge E

2009-07-01

Titanium oxide has antiinflammatory activity and tunable electrochemical behavior that make it an attractive material for the fabrication of implantable devices. The most stable composition is TiO2 and occurs mainly in three polymorphs, namely, anatase, rutile, and brookite, which differ in its crystallochemical properties. Here, we report the preparation of rutile surfaces that permit good adherence and axonal growth of cultured rat cerebral cortex neurons. Rutile disks were obtained by sinterization of TiO2 powders of commercial origin or precipitated from hydrolysis of Ti(IV)-isopropoxide. Commercial powders sintered at 1300-1600 degrees C produced rutile surfaces with abnormal grain growth, probably because of impurities of the powders. Neurons cultured on those surfaces survived in variable numbers and showed fewer neurites than on control materials. On the other hand, rutile sintered from precipitated powders had less contaminants and more homogenous grain growth. By adjusting the thermal treatment it was possible to obtain surfaces performing well as substrate for neuron survival for at least 10 days. Some surfaces permitted normal axonal elongation, whereas dendrite growth was generally impaired. These findings support the potential use of titanium oxide in neuroprostheses and other devices demanding materials with enhanced properties in terms of biocompatibility and axon growth promotion.

Nanocrystals in compression: unexpected structural phase transition and amorphization due to surface impurities.

PubMed

Liu, Gang; Kong, Lingping; Yan, Jinyuan; Liu, Zhenxian; Zhang, Hengzhong; Lei, Pei; Xu, Tao; Mao, Ho-Kwang; Chen, Bin

2016-06-09

We report an unprecedented surface doping-driven anomaly in the compression behaviors of nanocrystals demonstrating that the change of surface chemistry can lead to an interior bulk structure change in nanoparticles. In the synchrotron-based X-ray diffraction experiments, titania nanocrystals with low concentration yttrium dopants at the surface are found to be less compressible than undoped titania nanocrystals. More surprisingly, an unexpected TiO2(ii) phase (α-PbO2 type) is induced and obvious anisotropy is observed in the compression of yttrium-doped TiO2, in sharp contrast to the compression behavior of undoped TiO2. In addition, the undoped brookite nanocrystals remain with the same structure up to 30 GPa, whereas the yttrium-doped brookite amorphizes above 20 GPa. The abnormal structural evolution observed in yttrium-doped TiO2 does not agree with the reported phase stability of nano titania polymorphs, thus suggesting that the physical properties of the interior of nanocrystals can be controlled by the surface, providing an unconventional and new degree of freedom in search for nanocrystals with novel tunable properties that can trigger applications in multiple areas of industry and provoke more related basic science research.

Design & synthesis of silicone elastomer networks with tunable physico-chemical characteristics

NASA Astrophysics Data System (ADS)

Willoughby, Julie Ann-Crowe

2007-05-01

We have engineered functional surfaces via the manipulation of silicone elastomers (SEs). The most common silicone, poly(dimethylsiloxane) PDMS, can be both challenging and advantageous in the design of surfaces due to its inherent inertness and flexibility of the siloxane backbone. This unique polymer is approaching a $10 billion dollar market attributed to its formulation in a wide array of applications; from the personal care industry to the electronics industry. While it can be used for many applications, surface design with PDMS usually requires a chemical or physical modification of the polymeric network. In addition, surface characteristics are tailored for specific functions since there is not one surface that fits all end-uses. In studying the intrinsic behavior of engineered SEs, we asked questions regarding surface stability, environmental conformation and adaptability, and tuning physical features. We report on the formation of responsive surfaces with tailorable surface-reconstruction kinetics and switching hysteresis by thiol-ene radical addition of mercaptoalkanols with variable lengths to poly(vinylmethylsiloxane) networks. Exposing the modified surfaces to water led to a rearrangement of the hydrophilic alkanes at the surface. The rearrangement kinetics decreases with increasing number of the methylene spacers (n) in the mercaptoalkanol. The response kinetics is found to be very fast for n = 2 and 6. For instance, upon exposing to water, the water contact angle on 3-mercaptopropanol-based surfaces decreases by ≈35° at the rate of 2°/second. The high flexibility of the siloxane backbone endows these materials with switching longevity; the materials were able to switch their wettability over 10 cycles with minimum hysteresis. Increasing the number of methylene spacers to n = 11 decreases the surface reorganization dramatically. Formation of semi-crystalline regions in such materials (detected via IR) is responsible for initial "sluggish" kinetics and eventual surface "freezing". The effects of surface chemistry and topology on cellular adhesion and proliferation have been studied extensively in the past. However, little work exists that aims at probing the effects of surface morphology and elastic modulus on cell behavior. To achieve timely and comprehensive experimental design, there is need for the availability of novel substrata with tunable mechanical properties (or compliance) at the micro and meso-scale level ranging from individual cells to whole tissues. Despite expansive research that has targeted the understanding of cellular response to its host scaffold, the choice of material and extrapolation of findings from one cell/material system to another has proven difficult. Thus establishing general relationships between substrate compliance and cell behavior cannot be considered independent of the material and cell type. In our work, we have explored creating surfaces from SEs comprising gradients in stiffness (or elastic modulus), by controlling the degree of cross-linking. Network regions consisting of higher cross-linking demonstrate a greater elastic modulus. We present two methods to control the mechanical properties of silicone elastomers. The first technique utilizes interdiffusion of multiple SEs with varied molecular weights that are subsequently cross-linked into a network. The second method involves synthesizing a UV-curable SE. This method controls the degree of cross-linking by regulating the intensity of the UV light via a transparency with tunable transmittance placed on top of the SE film. Our results show that it is possible to generate compliance gradients through either route, enabling a large range of both gradient patterns and stiffness.

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

Shen, Yong; Desseaux, Solenne; Aden, Bethany

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

Highly coherent tunable mid-infrared frequency comb pumped by supercontinuum at 1 µm

NASA Astrophysics Data System (ADS)

Jin, Lei; Yamanaka, Masahito; Sonnenschein, Volker; Tomita, Hideki; Iguchi, Tetsuo; Sato, Atsushi; Oh-hara, Toshinari; Nishizawa, Norihiko

2017-01-01

We report a tunable mid-infrared frequency comb working at 184 MHz, which is based on difference frequency generation in a periodically poled Mg-doped stoichiometric lithium tantalate (PPMgSLT) crystal pumped by high-power supercontinuum pulses. Supercontinuum pulses from two fibers with different dispersion properties were examined. With a photonic crystal fiber (PCF) having normal dispersion properties, a tunable wavelength range of 2.9-4.7 µm was achieved. With another PCF having zero dispersion at 1040 nm, a maximum power of 1.34 mW was observed at 3.9 µm. The high coherence of the pulses generated with this scheme was verified experimentally, and a fringe visibility of 0.90 was observed.

Diffraction of digital micromirror device gratings and its effect on properties of tunable fiber lasers.

PubMed

Chen, Xiao; Yan, Bin-bin; Song, Fei-jun; Wang, Yi-quan; Xiao, Feng; Alameh, Kamal

2012-10-20

A digital micromirror device (DMD) is a kind of widely used spatial light modulator. We apply DMD as wavelength selector in tunable fiber lasers. Based on the two-dimensional diffraction theory, the diffraction of DMD and its effect on properties of fiber laser parameters are analyzed in detail. The theoretical results show that the diffraction efficiency is strongly dependent upon the angle of incident light and the pixel spacing of DMD. Compared with the other models of DMDs, the 0.55 in. DMD grating is an approximate blazed state in our configuration, which makes most of the diffracted radiation concentrated into one order. It is therefore a better choice to improve the stability and reliability of tunable fiber laser systems.

Sputtered (barium(x), strontium(1-x))titanate, BST, thin films on flexible copper foils for use as a non-linear dielectric

NASA Astrophysics Data System (ADS)

Laughlin, Brian James

Ferroelectric thin film dielectrics have a non-linear DC bias dependent permittivity and can be used as the dielectric between metal electrodes to make tunable Metal-Insulator-Metal (MIM) capacitors. Varactors can be used to change the resonance frequency of a circuit allowing high speed frequency switching intra- and inter-band. 2-D geometric arrays of circuitry, where resonant frequency is independently controlled by tunable elements in each section of the array, allow electromagnetic radiation to be focused and the wave front spatial trajectory controlled. BST thin films varactors allow large DC fields to be applied with modest voltages providing large tunabilities. If ferroelectric thin film based devices are to complement or supplant semiconductor varactors as tunable elements then devices must be synthesized using a low cost processing techniques. The Film on Foil process methodology for depositing BST thin films on copper foil substrates was used to create BST/Cu specimens. Sputtering conditions were determined via BST deposition on platinized silicon. Sputtered BST thin films were synthesized on Cu foil substrates and densified using high T, controlled pO2 anneals. XRD showed the absence of Cu2O in as-deposited, post crystallization annealed, and post "re-ox" annealed state. Data showed a polycrystalline BST microstructure with a 55--80 nm grain size and no copper oxidation. HRTEM imaging qualitatively showed evidence of an abrupt BST/Cu interface free from oxide formation. Dielectric properties of Cu/BST/Pt MIM devices were measured as a function of DC bias, frequency, and temperature. A permittivity of 725 was observed with tunability >3:1 while zero bias tan delta of 0.02 saturating to tan delta < 0.003 at high DC bias. No significant frequency dispersion was observed over five decades of frequency. Temperature dependent measurements revealed a broad ferroelectric transition with a maximum at -32°C which sustains a large tunability over -150°C to 150°C. Sputtered BST thin films on copper foils show comparable dielectric properties to CVD deposited films on platinized silicon substrates proving sputtered BST/Cu specimens can reproduce excellent properties using a more cost-effective processing approach. A concept for reducing the temperature dependence was explored. Stacks of multiple compositions of BST thin films were considered as an extension of core-shell structures to a thin film format. Temperature profiles of BST/Cu films were modeled and mathematically combined in simulations of multi-composition film stacks. Simulations showed singular composition BST thin films could meet X7R specifications if a film has a 292 K < TC < 330 K. Simulations of series connected film stacks show only modest temperature profile broadening. Parallel connected dual composition film stacks showed a 75°C temperature range with essentially flat capacitance by simulating compositions that create a DeltaTC = 283°C. Maximum permittivity and temperature profile shape independent of film thickness or composition were assumed for simulations. BST/Cu thickness and compositions series were fabricated and dielectric properties characterized. These studies showed films could be grown from 300 nm and approaching 1 mum without changing the dielectric temperature response. In studying BST composition, an increasing TC shift was observed when increasing Ba mole fraction in BST thin films while tunability >3:1 was maintained. These results provide a route for creating temperature stable capacitors using a BST/Cu embodiment. An effort to reduce surface roughness of copper foil substrates adversely impacted BST film integrity by impairing adhesion. XPS analysis of high surface roughness commercially obtained Cu foils revealed a surface treatment of Zn-Cu-O that was not present on smooth Cu, thus an investigation of surface chemistry was conducted. Sessile drop experiments were performed to characterize Cu-BST adhesion and the effects of metallic Zn and ZnO in this system. The study revealed the work of adhesion of Cu-BST, WCu-BSTa ≈ 0.60 J m-2, an intermediate value relative to noble metals commonly used as electrodes and substrates for electroceramics. Examination of metallic Zn-BST adhesion revealed a dramatic decrease of WZn-BSTa ≈ 0.13 J m-2, while increasing the content of Zn in metallic (Cux,Zn1-x) alloys monotonically reduced WCux,Zn1-x -BSTa . Conversely, a Cu-ZnO interface showed a large work of adhesion, WCu-ZnOa = 2.0 J m-2. These results indicate that a ZnO interlayer between the substrate Cu and the BST thin film provides adequate adhesion for robust films on flexible copper foil substrates. Additionally, this study provided characterization of adhesion for Zn-Al2O3 and Zn-BST; data that does not exist in the open literature. A process has been developed for preparing ultra-smooth copper foils by evaporation and subsequent peel-off of copper metal layers from glass slides. These 15 mum thick substrates exhibited roughness values between 1 and 2 nm RMS and 9 nm RMS over 25 mum2 and 100 mum2 analysis areas, respectively. The deposition and crystallization of BST layers on these ultra-smooth foils is demonstrated. The fully processed dielectric layers exhibited field tunability >5:1, and could withstand fields >750 kV cm-1. High field loss tangents below 0.007 were observed, making these materials excellent candidates for microwave devices. Finally, a process of lamination and contact lithography was used to demonstrate patterning of micron-scale features suitable for microwave circuit element designs.

High power tunable mid-infrared optical parametric oscillator enabled by random fiber laser.

PubMed

Wu, Hanshuo; Wang, Peng; Song, Jiaxin; Ye, Jun; Xu, Jiangming; Li, Xiao; Zhou, Pu

2018-03-05

Random fiber laser, as a kind of novel fiber laser that utilizes random distributed feedback as well as Raman gain, has become a research focus owing to its advantages of wavelength flexibility, modeless property and output stability. Herein, a tunable optical parametric oscillator (OPO) enabled by a random fiber laser is reported for the first time. By exploiting a tunable random fiber laser to pump the OPO, the central wavelength of idler light can be continuously tuned from 3977.34 to 4059.65 nm with stable temporal average output power. The maximal output power achieved is 2.07 W. So far as we know, this is the first demonstration of a continuous-wave tunable OPO pumped by a tunable random fiber laser, which could not only provide a new approach for achieving tunable mid-infrared (MIR) emission, but also extend the application scenarios of random fiber lasers.

Generation of tunable narrow-band surface-emitted terahertz radiation in periodically poled lithium niobate.

PubMed

Weiss, C; Torosyan, G; Avetisyan, Y; Beigang, R

2001-04-15

Generation of tunable narrow-band terahertz (THz) radiation perpendicular to the surface of periodically poled lithium niobate by optical rectification of femtosecond pulses is reported. The generated THz radiation can be tuned by use of different poling periods and different observation angles, limited only by the available bandwidth of the pump pulse. Typical bandwidths were 50-100 GHz, depending on the collection angle and the number of periods involved.

Liquid-crystal-based tunable plasmonic waveguide filters

NASA Astrophysics Data System (ADS)

Yin, Shengtao; Liu, Yan Jun; Xiao, Dong; He, Huilin; Luo, Dan; Jiang, Shouzhen; Dai, Haitao; Ji, Wei; Sun, Xiao Wei

2018-06-01

We propose a liquid-crystal-based tunable plasmonic waveguide filter and numerically investigate its filtering properties. The filter consists of a metal-insulator-metal waveguide with a nanocavity resonator. By filling the nanocavity with birefringent liquid crystals (LCs), we could then vary the effective refractive index of the nanocavity by controlling the alignment of the LC molecules, hence making the filter tunable. The tunable filtering properties are further analyzed in details via the temporal coupled mode theory (CMT) and the finite-difference time-domain (FDTD) method. The simulation results show that the resonant wavelengths have linear redshift as the refractive index of the nanocavity increases and the coupling efficiency is more than 65% without considering the internal loss in the nanocavity and waveguides. These achieved results by the FDTD simulations can be also accurately analyzed by CMT. The compact design of our proposed plasmonic filters is especially favorable for integration, and such filters could find many important potential applications in high-density plasmonic integration circuits.

Dual-enhanced photothermal conversion properties of reduced graphene oxide-coated gold superparticles for light-triggered acoustic and thermal theranostics

NASA Astrophysics Data System (ADS)

Lin, Li-Sen; Yang, Xiangyu; Niu, Gang; Song, Jibin; Yang, Huang-Hao; Chen, Xiaoyuan

2016-01-01

A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles-graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications.A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles-graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07552a

Toward tunable doping in graphene FETs by molecular self-assembled monolayers

NASA Astrophysics Data System (ADS)

Li, Bing; Klekachev, Alexander V.; Cantoro, Mirco; Huyghebaert, Cedric; Stesmans, André; Asselberghs, Inge; de Gendt, Stefan; de Feyter, Steven

2013-09-01

In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant.In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant. Electronic supplementary information (ESI) available: AFM images of self-assembled monolayers of OA on HOPG; AFM height image of the graphene surface on a SiC substrate; high resolution STM image of a self-assembled monolayer of OA on HOPG; transfer curves of a graphene FET with and without baking steps; transfer curves of a graphene FET under high vacuum conditions; transfer curves of a graphene FET and its Raman response before and after OA treatment; transfer curves of a graphene FET before and after rinsing with n-hexane. See DOI: 10.1039/c3nr01255g

A tunable single-polarization photonic crystal fiber filter based on surface plasmon resonance

NASA Astrophysics Data System (ADS)

Zhang, Shuhuan; Li, Jianshe; Li, Shuguang; Liu, Qiang; Liu, Yingchao; Zhang, Zhen; Wang, Yujun

2018-06-01

A tunable single polarizing filter is proposed by selectively coating gold film on the air holes of photonic crystal fiber (PCF). The polarization properties of the PCF filter are evaluated by the finite-element method. Simulation results show that the loss of y-polarized core mode at 1250 and 1550 nm is 136.23 and 839.73 dB/cm, respectively. Furthermore, we innovatively combine stable modulation with flexible modulation. To be specific, the resonance wavelengths are slowly controlled in a small wavelength range by altering the diameter of the air-hole-coated gold film, while the resonance wavelengths are flexibly controlled in a wide wavelength range by altering the thickness of the gold film or the diameter of the small air holes. When the length of the PCF is 500 µm, the bandwidth of extinction ratio greater than - 20 dB is only 60 nm at the communication window of 1550 nm. It is beneficial to fabricate a narrow-band polarization filter.

Seedless Synthesis of Monodispersed Gold Nanorods with Remarkably High Yield: Synergistic Effect of Template Modification and Growth Kinetics Regulation.

PubMed

Liu, Kang; Bu, Yanru; Zheng, Yuanhui; Jiang, Xuchuan; Yu, Aibing; Wang, Huanting

2017-03-08

Gold nanorods (AuNRs) are versatile materials due to their broadly tunable optical properties associated with their anisotropic feature. Conventional seed-mediated synthesis is, however, not only limited by the operational complexity and over-sensitivity towards subtle changes of experimental conditions but also suffers from low yield (≈15 %). A facile seedless method is reported to overcome these challenges. Monodispersed AuNRs with high yield (≈100 %) and highly adjustable longitudinal surface plasmon resonance (LSPR) are reproducibly synthesized. The parameters that influence the AuNRs growth were thoroughly investigated in terms of growth kinetics and soft-template regulation, offering a better understanding of the template-based mechanism. The facile synthesis, broad tunability of LSRP, high reproducibility, high yield, and ease of scale-up make this method promising for the future mass production of monodispersed AuNRs for applications in catalysis, sensing, and biomedicine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated MEMS-tunable VCSELs for reconfigurable optical interconnects

NASA Astrophysics Data System (ADS)

Kögel, Benjamin; Debernardi, Pierluigi; Westbergh, Petter; Gustavsson, Johan S.; Haglund, Åsa; Haglund, Erik; Bengtsson, Jörgen; Larsson, Anders

2012-03-01

A simple and low-cost technology for tunable vertical-cavity surface-emitting lasers (VCSELs) with curved movable micromirror is presented. The micro-electro-mechanical system (MEMS) is integrated with the active optical component (so-called half-VCSEL) by means of surface-micromachining using a reflown photoresist droplet as sacrificial layer. The technology is demonstrated for electrically pumped, short-wavelength (850 nm) tunable VCSELs. Fabricated devices with 10 μm oxide aperture are singlemode with sidemode suppression >35 dB, tunable over 24 nm with output power up to 0.5mW, and have a beam divergence angle <6 °. An improved high-speed design with reduced parasitic capacitance enables direct modulation with 3dB-bandwidths up to 6GHz and error-free data transmission at 5Gbit/s. The modulation response of the MEMS under electrothermal actuation has a bandwidth of 400 Hz corresponding to switching times of about 10ms. The thermal crosstalk between MEMS and half-VCSEL is negligible and not degrading the device performance. With these characteristics the integrated MEMS-tunable VCSELs are basically suitable for use in reconfigurable optical interconnects and ready for test in a prototype system. Schemes for improving output power, tuning speed, and modulation bandwidth are briefly discussed.

Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure.

PubMed

Chen, Nai-Chuan; Liao, Chung-Chi; Chen, Cheng-Chang; Fan, Wan-Ting; Wu, Jin-Han; Li, Jung-Yu; Chen, Shih-Pu; Huang, Bohr-Ran; Lee, Li-Ling

2014-01-01

This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d'Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm).

Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure

PubMed Central

2014-01-01

This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d’Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm). PMID:25328506

Tunable surface plasmon devices

DOEpatents

Shaner, Eric A [Rio Rancho, NM; Wasserman, Daniel [Lowell, MA

2011-08-30

A tunable extraordinary optical transmission (EOT) device wherein the tunability derives from controlled variation of the dielectric constant of a semiconducting material (semiconductor) in evanescent-field contact with a metallic array of sub-wavelength apertures. The surface plasmon resonance wavelength can be changed by changing the dielectric constant of the dielectric material. In embodiments of this invention, the dielectric material is a semiconducting material. The dielectric constant of the semiconducting material in the metal/semiconductor interfacial region is controllably adjusted by adjusting one or more of the semiconductor plasma frequency, the concentration and effective mass of free carriers, and the background high-frequency dielectric constant in the interfacial region. Thermal heating and/or voltage-gated carrier-concentration changes may be used to variably adjust the value of the semiconductor dielectric constant.

Electronic energy loss spectra from mono-layer to few layers of phosphorene

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

Mohan, Brij, E-mail: brijmohanhpu@yahoo.com; Thakur, Rajesh; Ahluwalia, P. K.

2016-05-23

Using first principles calculations, electronic and optical properties of few-layers phosphorene has been investigated. Electronic band structure show a moderate band gap of 0.9 eV in monolayer phosphorene which decreases with increasing number of layers. Optical properties of few-layers of phosphorene in infrared and visible region shows tunability with number of layers. Electron energy loss function has been plotted and huge red shift in plasmonic behaviours is found. These tunable electronic and optical properties of few-layers of phosphorene can be useful for the applications of optoelectronic devices.

2004 Army Research Office in Review

DTIC Science & Technology

2004-01-01

23 Uncool Tunable LWIR Microbolometer...but also for speech in multimedia applications. ELECTRONICS Uncooled Tunable LWIR Microbolometer – Multi- or hyper- spectral images contain...Analysis of NURBS Curves and Surfaces Jian-Ao Lian, Prairie View A&M University The multiresolution structure of NURBS ( nonuniform rational B

Spoof surface plasmons resonance effect and tunable electric response of improved metamaterial in the terahertz regime

NASA Astrophysics Data System (ADS)

Wang, Yue; Zhang, Li-Ying; Mei, Jin-Shuo; Zhang, Wen-Chao; Tong, Yi-Jing

2015-12-01

We propose an improved design and numerical study of an optimized tunable plasmonics artificial material resonator in the terahertz regime. We demonstrate that tunability can be realized with a transmission intensity as much as ˜61% in the lower frequency resonance, which is implemented through the effect of photoconductive switching under photoexcitation. In the higher frequency resonance, we show that spoof surface plasmons along the interface of metal/dielectric provide new types of electromagnetic resonances. Our approach opens up possibilities for the interface of metamaterial and plasmonics to be applied to optically tunable THz switching. Project supported by the National Natural Science Foundation of China (Grant No. 61201075), the Natural Science Foundation of Heilongjiang Province, China (Grant No. F2015039), the Young Scholar Project of Heilongjiang Provincial Education Bureau, China (Grant No. 1254G021), the China Postdoctoral Science Foundation (Grant No. 2012M511507), and the Science Funds for the Young Innovative Talents of Harbin University of Science and Technology, China (Grant No. 201302).

Dynamic Control of Radiative Heat Transfer with Tunable Materials for Thermal Management in Both Far and Near Fields

NASA Astrophysics Data System (ADS)

Yang, Yue

The proposed research mainly focuses on employing tunable materials to achieve dynamic control of radiative heat transfer in both far and near fields for thermal management. Vanadium dioxide (VO2), which undergoes a phase transition from insulator to metal at the temperature of 341 K, is one tunable material being applied. The other one is graphene, whose optical properties can be tuned by chemical potential through external bias or chemical doping. (Abstract shortened by ProQuest.).

Influence of the growth parameters on the electronic and magnetic properties of La0.67Sr0.33MnO3 epitaxial thin films

NASA Astrophysics Data System (ADS)

Annese, E.; Mori, T. J. A.; Schio, P.; Rache Salles, B.; Cezar, J. C.

2018-04-01

The implementation of La0.67Sr0.33MnO3 thin films in multilayered structures in organic and inorganic spintronics devices requires the optimization of their electronic and magnetic properties. In this work we report the structural, morphological, electronic and magnetic characterizations of La0.67Sr0.33MnO3 epitaxial thin films on SrTiO3 substrates, grown by pulsed laser deposition under different growing conditions. We show that the fluence of laser shots and in situ post-annealing conditions are important parameters to control the tetragonality (c/a) of the thin films. The distortion of the structure has a remarkable impact on both surface and bulk magnetism, allowing the tunability of the materials properties for use in different applications.

Tailoring plasmonic properties of nanobeam composites by the sliding disorder

NASA Astrophysics Data System (ADS)

Gric, Tatjana; Hess, Ortwin

2017-11-01

Nanobeam composites are important for designing sensing, nonlinear, and emission functionalities. Here, we describe a method for tuning the plasmonic properties of a silver nanobeam-based metamaterial. Such metamaterials open the wide avenues for a variety of applications in the fields of bio- and chemical sensing, nonlinearity enhancement, and fluorescence control. Specifically, we present the boundary between two nanobeam composites stacked together and exhibiting the sliding disorder. The modes are tunable. We simulated the solutions of surface plasmon polaritons (SPP) modes and their propagations. The configuration proposed here makes a breakthrough of the conventional configuration allowing for optimizations of SPP properties and making SPP application more flexible in practices. The wide plasmonic tuning range of nanobeam composites makes them promising in metamaterial-based optoelectronic devices. The plasma frequency is found to be tailored by the sliding disorder.

Versatile buffer layer architectures based on Ge1-xSnx alloys

NASA Astrophysics Data System (ADS)

Roucka, R.; Tolle, J.; Cook, C.; Chizmeshya, A. V. G.; Kouvetakis, J.; D'Costa, V.; Menendez, J.; Chen, Zhihao D.; Zollner, S.

2005-05-01

We describe methodologies for integration of compound semiconductors with Si via buffer layers and templates based on the GeSn system. These layers exhibit atomically flat surface morphologies, low defect densities, tunable thermal expansion coefficients, and unique ductile properties, which enable them to readily absorb differential stresses produced by mismatched overlayers. They also provide a continuous selection of lattice parameters higher than that of Ge, which allows lattice matching with technologically useful III-V compounds. Using this approach we have demonstrated growth of GaAs, GeSiSn, and pure Ge layers at low temperatures on Si(100). These materials display extremely high-quality structural, morphological, and optical properties opening the possibility of versatile integration schemes directly on silicon.

Normal incidence reflective-mode etalons with novel spectral properties

NASA Astrophysics Data System (ADS)

Te Kolste, Robert D.

2003-11-01

Etalons having one surface which is highly reflective have been used for a variety of applications. By varying the coating type and carefully controlling the thicknesses of the coatings on the lower reflectance side, one can obtain interesting and useful properties. One example is a low finesse but highly efficient element having a reflectance which is very sinusoidal with respect to wavelength. By adding additional layers, functions which are asymmetric about the reflectance peak with respect to wavelength can be obtained, including behavior which approximates a sawtooth reflectance as a function of wavelength. Such devices are easily fabricated at the wafer scale, and can be used in wavelength monitoring and control applications such as wavelength lockers for tunable lasers.

Activating the molecular spinterface

NASA Astrophysics Data System (ADS)

Cinchetti, Mirko; Dediu, V. Alek; Hueso, Luis E.

2017-05-01

The miniaturization trend in the semiconductor industry has led to the understanding that interfacial properties are crucial for device behaviour. Spintronics has not been alien to this trend, and phenomena such as preferential spin tunnelling, the spin-to-charge conversion due to the Rashba-Edelstein effect and the spin-momentum locking at the surface of topological insulators have arisen mainly from emergent interfacial properties, rather than the bulk of the constituent materials. In this Perspective we explore inorganic/molecular interfaces by looking closely at both sides of the interface. We describe recent developments and discuss the interface as an ideal platform for creating new spin effects. Finally, we outline possible technologies that can be generated thanks to the unique active tunability of molecular spinterfaces.

Stability enhancement and electronic tunability of two-dimensional SbIV compounds via surface functionalization

NASA Astrophysics Data System (ADS)

Zhou, Wenhan; Guo, Shiying; Liu, Xuhai; Cai, Bo; Song, Xiufeng; Zhu, Zhen; Zhang, Shengli

2018-01-01

We propose a family of hydrogenated- and halogenated-SbIV (SbIVX-2) materials that simultaneously have two-dimensional (2D) structures, high stability and appealing electronic properties. Based on first-principles total-energy and vibrational-spectra calculations, SbIVX-2 monolayers are found both thermally and dynamically stable. Varying IV and X elements can rationally tune the electronic properties of SbIVX-2 monolayers, effectively modulating the band gap from 0 to 3.42 eV. Regarding such superior stability and broad band-gap range, SbIVX-2 monolayers are expected to be synthesized in experiments and taken as promising candidates for low-dimensional electronic and optoelectronic devices, such as blue-to-ultraviolet light-emitting diodes (LED) and photodetectors.

Hard template synthesis of metal nanowires

PubMed Central

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-01-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance, and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed. PMID:25453031

Hard template synthesis of metal nanowires

NASA Astrophysics Data System (ADS)

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-11-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed.

Hard template synthesis of metal nanowires.

PubMed

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-01-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance, and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed.

Tunable surface configuration of skyrmion lattices in cubic helimagnets

NASA Astrophysics Data System (ADS)

Wan, Xuejin; Hu, Yangfan; Wang, Biao

2018-06-01

In bulk helimagnets, the presence of magnetic skyrmion lattices is always accompanied by a periodic stress field due to the intrinsic magnetoelastic coupling. The release of this nontrivial stress field at the surface causes a periodic displacement field, which characterizes a novel particle-like property of skyrmion: its surface configuration. Here, we derive the analytical solution of this displacement field for semi-infinite cubic helimagnet with the skyrmion magnetization approximated by the triple-Q representation. For MnSi, we show that the skyrmion lattices have a bumpy surface configuration characterized by periodically arranged peaks with a characteristic height of about 10‑13 m. The pattern of the peaks can be controlled by varying the strength of the applied magnetic field. Moreover, we prove that the surface configuration varies together with the motion and deformation of the skyrmion lattices. As a result, the surface configuration can be tuned by application of electric current, mechanical loads, as well as any other effective external fields for skyrmion lattices.

Size-tunable Lateral Confinement in Monolayer Semiconductors

DOE PAGES

Wei, Guohua; Czaplewski, David A.; Lenferink, Erik J.; ...

2017-06-12

Three-dimensional confinement allows semiconductor quantum dots to exhibit size-tunable electronic and optical properties that enable a wide range of opto-electronic applications from displays, solar cells and bio-medical imaging to single-electron devices. Additional modalities such as spin and valley properties in monolayer transition metal dichalcogenides provide further degrees of freedom requisite for information processing and spintronics. In nanostructures, however, spatial confinement can cause hybridization that inhibits the robustness of these emergent properties. Here in this paper, we show that laterally-confined excitons in monolayer MoS 2 nanodots can be created through top-down nanopatterning with controlled size tunability. Unlike chemically-exfoliated monolayer nanoparticles, themore » lithographically patterned monolayer semiconductor nanodots down to a radius of 15 nm exhibit the same valley polarization as in a continuous monolayer sheet. The inherited bulk spin and valley properties, the size dependence of excitonic energies, and the ability to fabricate MoS 2 nanostructures using semiconductor-compatible processing suggest that monolayer semiconductor nanodots have potential to be multimodal building blocks of integrated optoelectronics and spintronics systems« less

Complete photonic band gaps and tunable self-collimation in the two-dimensional plasma photonic crystals with a new structure

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

Zhang, Hai-Feng, E-mail: hanlor@163.com; Nanjing Artillery Academy, Nanjing 211132; Ding, Guo-Wen

2015-02-15

In this paper, the properties of complete photonic band gaps (CPBGs) and tunable self-collimation in two-dimensional plasma photonic crystals (2D PPCs) with a new structure in square lattices, whose dielectric fillers (GaAs) are inserted into homogeneous and nomagnetized plasma background are theoretically investigated by a modified plane wave expansion (PWE) method with a novel technique. The novel PWE method can be utilized to compute the dispersion curves of 2D PPCs with arbitrary-shaped cross section in any lattices. As a comparison, CPBGs of PPCs for four different configurations are numerically calculated. The computed results show that the proposed design has themore » advantages of achieving the larger CPBGs compared to the other three configurations. The influences of geometric parameters of filled unit cell and plasma frequency on the properties of CPBGs are studied in detail. The calculated results demonstrate that CPBGs of the proposed 2D PPCs can be easily engineered by changing those parameters, and the larger CPBGs also can be obtained by optimization. The self-collimation in such 2D PPCs also is discussed in theory under TM wave. The theoretical simulations reveal that the self-collimation phenomena can be found in the TM bands, and both the frequency range of self-collimation and the equifrequency surface contours can be tuned by the parameters as mentioned above. It means that the frequency range and direction of electromagnetic wave can be manipulated by designing, as it propagates in the proposed PPCs without diffraction. Those results can hold promise for designing the tunable applications based on the proposed PPCs.« less

Synthesis of Large-Size 1T' ReS2x Se2(1-x) Alloy Monolayer with Tunable Bandgap and Carrier Type.

PubMed

Cui, Fangfang; Feng, Qingliang; Hong, Jinhua; Wang, Renyan; Bai, Yu; Li, Xiaobo; Liu, Dongyan; Zhou, Yu; Liang, Xing; He, Xuexia; Zhang, Zhongyue; Liu, Shengzhong; Lei, Zhibin; Liu, Zonghuai; Zhai, Tianyou; Xu, Hua

2017-12-01

Chemical vapor deposition growth of 1T' ReS 2 x Se 2(1- x ) alloy monolayers is reported for the first time. The composition and the corresponding bandgap of the alloy can be continuously tuned from ReSe 2 (1.32 eV) to ReS 2 (1.62 eV) by precisely controlling the growth conditions. Atomic-resolution scanning transmission electron microscopy reveals an interesting local atomic distribution in ReS 2 x Se 2(1- x ) alloy, where S and Se atoms are selectively occupied at different X sites in each Re-X 6 octahedral unit cell with perfect matching between their atomic radius and space size of each X site. This structure is much attractive as it can induce the generation of highly desired localized electronic states in the 2D surface. The carrier type, threshold voltage, and carrier mobility of the alloy-based field effect transistors can be systematically modulated by tuning the alloy composition. Especially, for the first time the fully tunable conductivity of ReS 2 x Se 2(1- x ) alloys from n-type to bipolar and p-type is realized. Owing to the 1T' structure of ReS 2 x Se 2(1- x ) alloys, they exhibit strong anisotropic optical, electrical, and photoelectric properties. The controllable growth of monolayer ReS 2 x Se 2(1- x ) alloy with tunable bandgaps and electrical properties as well as superior anisotropic feature provides the feasibility for designing multifunctional 2D optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrophobic Coatings by Thiol-Ene Click Functionalization of Silsesquioxanes with Tunable Architecture.

PubMed

Dirè, Sandra; Bottone, Davide; Callone, Emanuela; Maniglio, Devid; Génois, Isabelle; Ribot, François

2017-08-08

The hydrolysis-condensation of trialkoxysilanes under strictly controlled conditions allows the production of silsesquioxanes (SSQs) with tunable size and architecture ranging from ladder to cage-like structures. These nano-objects can serve as building blocks for the preparation of hybrid organic/inorganic materials with selected properties. The SSQs growth can be tuned by simply controlling the reaction duration in the in situ water production route (ISWP), where the kinetics of the esterification reaction between carboxylic acids and alcohols rules out the extent of organosilane hydrolysis-condensation. Tunable SSQs with thiol functionalities (SH-NBBs) are suitable for further modification by exploiting the simple thiol-ene click reaction, thus allowing for modifying the wettability properties of derived coatings. In this paper, coatings were prepared from SH-NBBs with different architecture onto cotton fabrics and paper, and further functionalized with long alkyl chains by means of initiator-free UV-induced thiol-ene coupling with 1-decene (C10) and 1-tetradecene (C14). The coatings appeared to homogeneously cover the natural fibers and imparted a multi-scale roughness that was not affected by the click functionalization step. The two-step functionalization of cotton and paper warrants a stable highly hydrophobic character to the surface of natural materials that, in perspective, suggests a possible application in filtration devices for oil-water separation. Furthermore, the purification of SH-NBBs from ISWP by-products was possible during the coating process, and this step allowed for the fast, initiator-free, click-coupling of purified NBBs with C10 and C14 in solution with a nearly quantitative yield. Therefore, this approach is an alternative route to get sol-gel-derived, ladder-like, and cage-like SSQs functionalized with long alkyl chains.

Oxidation catalysis by polyoxometalates fundamental electron-transfer phenomena

Treesearch

Yurii V. Geletii; Rajai H. Atalla; Alan J. Bailey; Laurent Delannoy; Craig L. Hill; Ira A. Weinstock

2002-01-01

Early transition-metal oxygen-anion clusters (polyoxometalates, POMs) are a large and rapidly growing class of versatile and tunable oxidation catalysts. All key molecular properties of these clusters (composition, size, shape, charge density, reduction potential, solubility, etc.) can be systematically altered, and the clusters themselves can serve as tunable ligands...

Acousto-Optic Tunable Filter Hyperspectral Microscope Imaging Method for Characterizing Spectra from Foodborne Pathogens.

USDA-ARS?s Scientific Manuscript database

Hyperspectral microscope imaging (HMI) method, which provides both spatial and spectral characteristics of samples, can be effective for foodborne pathogen detection. The acousto-optic tunable filter (AOTF)-based HMI method can be used to characterize spectral properties of biofilms formed by Salmon...

The tunable wettability in multistimuli-responsive smart graphene surfaces

NASA Astrophysics Data System (ADS)

Wan, Shanhong; Pu, Jibin; Zhang, Xiaoqian; Wang, Liping; Xue, Qunji

2013-01-01

The tunable wettability of smart graphene films onto stainless steel substrates with a multi-response to different environmental stimuli has been investigated including light irradiation, pH, electric field, and annealing temperature. Conductive graphene film exhibited the controllable transition from water-repellent to water-loving characteristic in response to different environment fields, which primarily resulted from the morpho-chemically synergistic effect as well as the restoration of electronic stucture. Based on the fundamental theories of wettability, mechanisms in switching from hydrophobicity to hydrophilicity for smart graphene surface including thermal chemistry, electrostatic, photo-induced surface chemistry, solvent, and pH methods were presented.

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

NASA Astrophysics Data System (ADS)

Katoch, Jyoti; Ulstrup, Søren; Koch, Roland J.; Moser, Simon; McCreary, Kathleen M.; Singh, Simranjeet; Xu, Jinsong; Jonker, Berend T.; Kawakami, Roland K.; Bostwick, Aaron; Rotenberg, Eli; Jozwiak, Chris

2018-04-01

In two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), new electronic phenomena such as tunable bandgaps1-3 and strongly bound excitons and trions emerge from strong many-body effects4-6, beyond the spin and valley degrees of freedom induced by spin-orbit coupling and by lattice symmetry7. Combining single-layer TMDs with other 2D materials in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these many-body effects, by means of engineered interlayer interactions8-10. Here, we use micro-focused angle-resolved photoemission spectroscopy (microARPES) and in situ surface doping to manipulate the electronic structure of single-layer WS2 on hexagonal boron nitride (WS2/h-BN). Upon electron doping, we observe an unexpected giant renormalization of the spin-orbit splitting of the single-layer WS2 valence band, from 430 meV to 660 meV, together with a bandgap reduction of at least 325 meV, attributed to the formation of trionic quasiparticles. These findings suggest that the electronic, spintronic and excitonic properties are widely tunable in 2D TMD/h-BN heterostructures, as these are intimately linked to the quasiparticle dynamics of the materials11-13.

Cell surface engineering with polyelectrolyte multilayer thin films.

PubMed

Wilson, John T; Cui, Wanxing; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Pan, Di; Qu, Zheng; Krishnamurthy, Venkata R; Mets, Joseph; Kumar, Vivek; Wen, Jing; Song, Yuhua; Tsukruk, Vladimir V; Chaikof, Elliot L

2011-05-11

Layer-by-layer assembly of polyelectrolyte multilayer (PEM) films represents a bottom-up approach for re-engineering the molecular landscape of cell surfaces with spatially continuous and molecularly uniform ultrathin films. However, fabricating PEMs on viable cells has proven challenging owing to the high cytotoxicity of polycations. Here, we report the rational engineering of a new class of PEMs with modular biological functionality and tunable physicochemical properties which have been engineered to abrogate cytotoxicity. Specifically, we have discovered a subset of cationic copolymers that undergoes a conformational change, which mitigates membrane disruption and facilitates the deposition of PEMs on cell surfaces that are tailorable in composition, reactivity, thickness, and mechanical properties. Furthermore, we demonstrate the first successful in vivo application of PEM-engineered cells, which maintained viability and function upon transplantation and were used as carriers for in vivo delivery of PEMs containing biomolecular payloads. This new class of polymeric film and the design strategies developed herein establish an enabling technology for cell transplantation and other therapies based on engineered cells. © 2011 American Chemical Society

On Applicability of Tunable Filter Bank Based Feature for Ear Biometrics: A Study from Constrained to Unconstrained.

PubMed

Chowdhury, Debbrota Paul; Bakshi, Sambit; Guo, Guodong; Sa, Pankaj Kumar

2017-11-27

In this paper, an overall framework has been presented for person verification using ear biometric which uses tunable filter bank as local feature extractor. The tunable filter bank, based on a half-band polynomial of 14th order, extracts distinct features from ear images maintaining its frequency selectivity property. To advocate the applicability of tunable filter bank on ear biometrics, recognition test has been performed on available constrained databases like AMI, WPUT, IITD and unconstrained database like UERC. Experiments have been conducted applying tunable filter based feature extractor on subparts of the ear. Empirical experiments have been conducted with four and six subdivisions of the ear image. Analyzing the experimental results, it has been found that tunable filter moderately succeeds to distinguish ear features at par with the state-of-the-art features used for ear recognition. Accuracies of 70.58%, 67.01%, 81.98%, and 57.75% have been achieved on AMI, WPUT, IITD, and UERC databases through considering Canberra Distance as underlying measure of separation. The performances indicate that tunable filter is a candidate for recognizing human from ear images.

Sialic Acid-Responsive Polymeric Interface Material: From Molecular Recognition to Macroscopic Property Switching

NASA Astrophysics Data System (ADS)

Xiong, Yuting; Jiang, Ge; Li, Minmin; Qing, Guangyan; Li, Xiuling; Liang, Xinmiao; Sun, Taolei

2017-01-01

Biological systems that utilize multiple weak non-covalent interactions and hierarchical assemblies to achieve various bio-functions bring much inspiration for the design of artificial biomaterials. However, it remains a big challenge to correlate underlying biomolecule interactions with macroscopic level of materials, for example, recognizing such weak interaction, further transforming it into regulating material’s macroscopic property and contributing to some new bio-applications. Here we designed a novel smart polymer based on polyacrylamide (PAM) grafted with lactose units (PAM-g-lactose0.11), and reported carbohydrate-carbohydrate interaction (CCI)-promoted macroscopic properties switching on this smart polymer surface. Detailed investigations indicated that the binding of sialic acid molecules with the grafted lactose units via the CCIs induced conformational transformation of the polymer chains, further resulted in remarkable and reversible switching in surface topography, wettability and stiffness. With these excellent recognition and response capacities towards sialic acid, the PAM-g-lactose0.11 further facilitated good selectivity, strong anti-interference and high adsorption capacity in the capture of sialylated glycopeptides (important biomarkers for cancers). This work provides some enlightenment for the development of biointerface materials with tunable property, as well as high-performance glycopeptide enrichment materials.

Morphology, stoichiometry, and crystal structure control via post-annealing for Pt-ZnO nanograin Schottky barrier interfaces

NASA Astrophysics Data System (ADS)

Chan, Yuet Ching; Yu, Jerry; Ho, Derek

2018-06-01

Nanointerfaces have attracted intensive research effort for advanced electronics due to their unique and tunable semiconducting properties made possible by metal-contacted oxide structures at the nanoscale. Although much work has been on the adjustment of fabrication parameters to achieve high-quality interfaces, little work has experimentally obtained the various correlations between material parameters and Schottky barrier electronic properties to accurately probe the underlying phenomenon. In this work, we investigate the control of Pt-ZnO nanograin interfaces properties by thermal annealing. Specifically, we quantitatively analyze the correlation between material parameters (such as surface morphology, crystallographic structure, and stoichiometry) and Schottky diode parameters (Schottky barrier height, ideality factor, and contact resistance). Results revealed strong dependencies of Schottky barrier characteristics on oxygen vacancies, surface roughness, grain density, d-spacing, and crystallite size. I-V-T data shows that annealing at 600 °C produces a nanograin based interface with the most rectifying diode characteristics. These dependencies, which have not been previously reported holistically, highlight the close relationship between material properties and Schottky barrier characteristics, and are instrumental for the performance optimization of nanostructured metal-semiconductor interfaces in advanced electronic devices.

Tissue-engineered cartilage with inducible and tunable immunomodulatory properties

PubMed Central

Glass, Katherine A.; Link, Jarrett M.; Brunger, Jonathan M.; Moutos, Franklin T.; Gersbach, Charles A.; Guilak, Farshid

2014-01-01

The pathogenesis of osteoarthritis is mediated in part by inflammatory cytokines including interleukin-1 (IL-1), which promote degradation of articular cartilage and prevent human mesenchymal stem cell (MSC) chondrogenesis. In this study, we combined gene therapy and functional tissue engineering to develop engineered cartilage with immunomodulatory properties that allow chondrogenesis in the presence of pathologic levels of IL-1 by inducing overexpression of IL-1 receptor antagonist (IL-1Ra) in MSCs via scaffold-mediated lentiviral gene delivery. A doxycycline-inducible vector was used to transduce MSCs in monolayer or within 3D woven PCL scaffolds to enable tunable IL-1Ra production. In the presence of IL-1, IL-1Ra-expressing engineered cartilage produced cartilage-specific extracellular matrix, while resisting IL-1-induced upregulation of matrix metalloproteinases and maintaining mechanical properties similar to native articular cartilage. The ability of functional engineered cartilage to deliver tunable anti-inflammatory cytokines to the joint may enhance the long-term success of therapies for cartilage injuries or osteoarthritis. PMID:24767790

Engineered liquid crystal anchoring energies with nanopatterned surfaces.

PubMed

Gear, Christopher; Diest, Kenneth; Liberman, Vladimir; Rothschild, Mordechai

2015-01-26

The anchoring energy of liquid crystals was shown to be tunable by surface nanopatterning of periodic lines and spaces. Both the pitch and height were varied using hydrogen silsesquioxane negative tone electron beam resist, providing for flexibility in magnitude and spatial distribution of the anchoring energy. Using twisted nematic liquid crystal cells, it was shown that this energy is tunable over an order of magnitude. These results agree with a literature model which predicts the anchoring energy of sinusoidal grooves.

Finite-difference time-domain simulation of electromagnetic bandgap and bi-anisotropic metamaterials

NASA Astrophysics Data System (ADS)

Bray, Matthew G.

The term "Metamaterial" has been introduced into the electromagnetic lexicon in recent years to describe new artificial materials with electromagnetic properties that are not found in naturally occurring materials. Metamaterials exhibit electromagnetic properties that are not observed in its constituent materials, and/or not observed in nature. This thesis will analyze two different classes of metamaterials through the use of the finite-difference time-domain (FDTD) technique. The first class of metamaterials are artificial magnetic conductors (AMC) which approximate the behavior of a perfect magnetic conductor (PMC) over a finite frequency range. The AMC metamaterials are created through the use of an electromagnetic bandgap (EBG) structure. A periodic FDTD code is used to simulate a full-wave model of the metallodielectric EBG structures. The AMCs developed with the aid of the FDTD tool are then used to create low-profile antenna systems consisting of a dipole antenna in close proximity to an AMC surface. Through the use of this FDTD tool, several original contributions were made to the electromagnetic community. These include the first dual-band independently tunable EBG AMC ground plane and the first linearly polarized single-band and dual-band tunable antenna/EBG systems. The second class of materials analyzed are bi-anisotropic metamaterials. Bi-anisotropic media are the largest class of linear media which is able to describe the macroscopic material properties of artificial dielectrics, artificial magnetics, artificial chiral materials, left-handed materials, and other composite materials. The dispersive properties of these materials can be approximated by the oscillator model. This model assumes a Lorentzian frequency profile for the permittivity and permeability and a Condon model for chirality. A new FDTD formulation is introduced which can simulate this type of bi-anisotropic media. This FDTD method incorporates the dispersive material properties through a Z-transform technique derived from the constitutive relations for bi-anisotropic media. This is the first FDTD formulation to be able to simulate dispersive chiral media on a single FDTD grid. This tool was also used to perform the first simulations of dispersive chiral frequency selective surfaces.

Tunable properties of light propagation in photonic liquid crystal fibers

NASA Astrophysics Data System (ADS)

Szaniawska, K.; Nasilowski, T.; Woliński, T. R.; Thienpont, H.

2006-12-01

Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].

Precise Control Over Morphology and Density of Metal and Transition Metal Nanostructures for Sensing and Energy Related Applications

NASA Astrophysics Data System (ADS)

Tran, Minh

Metallic nanostructures are of great interest due to their applicability in various modern technologies, such as catalysis, sensing, and optoelectronics. In this work, we employed three solution-based methods, including colloidal suspension synthesis, modified galvanic displacement, and electrodeposition, to synthesize nanostructured metals and transition metals, including gold (Au), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), and cobalt (Co). Our focus was to establish process-structure-property relationship and explore their applicability in the field of sensing and clean energy generation. More precisely we established relationships between experimental parameters, such as temperature, applied potential, electrolyte pH, reactant concentration, additive, and the number of deposition cycles, and the characteristics of the nanostructures, such as morphology, density, size, and size distribution. Our results indicated that the nanostructures were tunable by adjusting the process parameters. This provided insight into the growth mechanisms of the metallic nanostructures. Since properties of the nanostructures are tunable by controlling the structure, our results provided researchers with additional tools to obtain nanomaterials with desired properties for specific applications. The materials synthesized by our methods were utilized to as substrates for surface enhanced Raman spectroscopy (SERS) and as photocathodes for photoelectrochemical production of hydrogen. The results showed that the performances of our materials were either promising or compatible with those reported in the literature, thus bringing new opportunities to the development of low-cost, high-performance, and flexible nanomaterials for the current and future technologies.

MEMS for Tunable Photonic Metamaterial Applications

NASA Astrophysics Data System (ADS)

Stark, Thomas

Photonic metamaterials are materials whose optical properties are derived from artificially-structured sub-wavelength unit cells, rather than from the bulk properties of the constituent materials. Examples of metamaterials include plasmonic materials, negative index materials, and electromagnetic cloaks. While advances in simulation tools and nanofabrication methods have allowed this field to grow over the past several decades, many challenges still exist. This thesis addresses two of these challenges: fabrication of photonic metamaterials with tunable responses and high-throughput nanofabrication methods for these materials. The design, fabrication, and optical characterization of a microelectromechanical systems (MEMS) tunable plasmonic spectrometer are presented. An array of holes in a gold film, with plasmon resonance in the mid-infrared, is suspended above a gold reflector, forming a Fabry-Perot interferometer of tunable length. The spectra exhibit the convolution of extraordinary optical transmission through the holes and Fabry-Perot resonances. Using MEMS, the interferometer length is modulated from 1.7 mum to 21.67 mum , thereby tuning the free spectral range from about 2900 wavenumbers to 230.7 wavenumbers and shifting the reflection minima and maxima across the infrared. Due to its broad spectral tunability in the fingerprint region of the mid-infrared, this device shows promise as a tunable biological sensing device. To address the issue of high-throughput, high-resolution fabrication of optical metamaterials, atomic calligraphy, a MEMS-based dynamic stencil lithography technique for resist-free fabrication of photonic metamaterials on unconventional substrates, has been developed. The MEMS consists of a moveable stencil, which can be actuated with nanometer precision using electrostatic comb drive actuators. A fabrication method and flip chip method have been developed, enabling evaporation of metals through the device handle for fabrication on an external substrate. While the MEMS can be used to fabricate over areas of approximately 100 square mum2, a piezoelectric step-and repeat system enables fabrication over cm length scales. Thus, this technique leverages the precision inherent to MEMS actuation, while enhancing nanofabrication thoughput. Fabricating metamaterials on new substrates will enable novel and tunable metamaterials. For example, by fabricating unit cells on a periodic auxetic mechanical scaffold, the optical properties can be tuned by straining the mechanical scaffold.

A Biphasic Ligand Exchange Reaction on Cdse Nanoparticles: Introducing Undergraduates to Functionalizing Nanoparticles for Solar Cells

ERIC Educational Resources Information Center

Zemke, Jennifer M.; Franz, Justin

2016-01-01

Semiconductor nanoparticles, including cadmium selenide (CdSe) particles, are attractive as light harvesting materials for solar cells. In the undergraduate laboratory, the size-tunable optical and electronic properties can be easily investigated; however, these nanoparticles (NPs) offer another platform for application-based tunability--the NP…

Electrical and Optical Tunability in All-Inorganic Halide Perovskite Alloy Nanowires.

PubMed

Lei, Teng; Lai, Minliang; Kong, Qiao; Lu, Dylan; Lee, Woochul; Dou, Letian; Wu, Vincent; Yu, Yi; Yang, Peidong

2018-06-13

Alloying different semiconductors is a powerful approach to tuning the optical and electronic properties of semiconductor materials. In halide perovskites (ABX 3 ), alloys with different anions have been widely studied, and great band gap tunability in the visible range has been achieved. However, perovskite alloys with different cations at the "B" site are less understood due to the synthetic challenges. Herein, we first have developed the synthesis of single-crystalline CsPb x Sn 1- x I 3 nanowires (NWs). The electronic band gaps of CsPb x Sn 1- x I 3 NWs can be tuned from 1.3 to 1.78 eV by varying the Pb/Sn ratio, which leads to the tunable photoluminescence (PL) in the near-infrared range. More importantly, we found that the electrical conductivity increases as more Sn 2+ is alloyed with Pb 2+ , possibly due to the increase of charge carrier concentration when more Sn 2+ is introduced. The wide tunability of the optical and electronic properties makes CsPb x Sn 1- x I 3 alloy NWs promising candidates for future optoelectronic device applications.

Broadband dielectric characterization of sapphire/TiOx/Ba₀.₃Sr₀.₇TiO₃ (111)-oriented thin films for the realization of a tunable interdigitated capacitor.

PubMed

Ghalem, Areski; Ponchel, Freddy; Remiens, Denis; Legier, Jean-Francois; Lasri, Tuami

2013-05-01

A complete microwave characterization up to 67 GHz using specific coplanar waveguides was performed to determine the dielectric properties (permittivity, losses, and tunability) of sapphire/TiOx/Ba0.3Sr0.7TiO3 (BST) (111)-oriented thin films. To that end, BaxSr1-xTiO3 thin films were deposited by RF magnetron sputtering on sapphire (0001) substrate. To control the preferred (111) orientation, a TiOx buffer layer was deposited on sapphire. According to the detailed knowledge of the material properties, it has been possible to conceive, fabricate, and test interdigitated capacitors, the basic element for future microwave tunable applications. Retention of capacitive behavior up to 67 GHz and a tunability of 32% at 67 GHz at an applied voltage of 30 V (150 kV/cm) were observed. The Q-factor remains greater than 30 over the entire frequency band. The possibility of a complete characterization of the material for the realization of high-performance interdigitated capacitors opens the door to microwave device fabrication.

Periodic nanostructural materials for nanoplasmonics

NASA Astrophysics Data System (ADS)

Choi, Dukhyun

2017-02-01

Nanoscale periodic material design and fabrication are essentially fundamental requirement for basic scientific researches and industrial applications of nanoscience and engineering. Innovative, effective, reproducible, large-area uniform, tunable and robust nanostructure/material syntheses are still challenging. Here, I would like to introduce the novel periodic nanostructural materials particularly with uniformly ordered nanoporous or nanoflower structures, which are fabricated by simple, cost-effective, and high-throughput wet chemical methods. I also report large-area periodic plasmonic nanostructures based on template-based nanolithography. The surface morphology and optical properties are characterized by SEM and UV-vis. spectroscopy. Furthermore, their enhancement factor is evaluated by using SERS signals.

Experimental verification of the rainbow trapping effect in adiabatic plasmonic gratings

PubMed Central

Gan, Qiaoqiang; Gao, Yongkang; Wagner, Kyle; Vezenov, Dmitri; Ding, Yujie J.; Bartoli, Filbert J.

2011-01-01

We report the experimental observation of a trapped rainbow in adiabatically graded metallic gratings, designed to validate theoretical predictions for this unique plasmonic structure. One-dimensional graded nanogratings were fabricated and their surface dispersion properties tailored by varying the grating groove depth, whose dimensions were confirmed by atomic force microscopy. Tunable plasmonic bandgaps were observed experimentally, and direct optical measurements on graded grating structures show that light of different wavelengths in the 500–700-nm region is “trapped” at different positions along the grating, consistent with computer simulations, thus verifying the “rainbow” trapping effect. PMID:21402936

Tunable dual-band nearly perfect absorption based on a compound metallic grating

NASA Astrophysics Data System (ADS)

Gao, Hua; Zheng, Zhi-Yuan; Feng, Juan

2017-02-01

Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure.

From Flexible and Stretchable Meta-Atom to Metamaterial: A Wearable Microwave Meta-Skin with Tunable Frequency Selective and Cloaking Effects

PubMed Central

Yang, Siming; Liu, Peng; Yang, Mingda; Wang, Qiugu; Song, Jiming; Dong, Liang

2016-01-01

This paper reports a flexible and stretchable metamaterial-based “skin” or meta-skin with tunable frequency selective and cloaking effects in microwave frequency regime. The meta-skin is composed of an array of liquid metallic split ring resonators (SRRs) embedded in a stretchable elastomer. When stretched, the meta-skin performs as a tunable frequency selective surface with a wide resonance frequency tuning range. When wrapped around a curved dielectric material, the meta-skin functions as a flexible “cloaking” surface to significantly suppress scattering from the surface of the dielectric material along different directions. We studied frequency responses of multilayer meta-skins to stretching in a planar direction and to changing the spacing between neighboring layers in vertical direction. We also investigated scattering suppression effect of the meta-skin coated on a finite-length dielectric rod in free space. This meta-skin technology will benefit many electromagnetic applications, such as frequency tuning, shielding, and scattering suppression. PMID:26902969

Far-field emission characteristics and linewidth measurements of surface micro-machined MEMS tunable VCSELs

NASA Astrophysics Data System (ADS)

Paul, Sujoy; Gierl, Christian; Gründl, Tobias; Zogal, Karolina; Meissner, Peter; Amann, Markus-Christian; Küppers, Franko

2013-03-01

In this paper, we demonstrate for the first time the far-field experimental results and the linewidth characteris- tics for widely tunable surface-micromachined micro-electro-mechanical system (MEMS) vertical-cavity surface- emitting lasers (VCSELs) operating at 1550 nm. The fundamental Gaussian mode emission is confirmed by optimizing the radius of curvature of top distributed Bragg reflector (DBR) membrane and by choosing an ap- propriate diameter of circular buried tunnel junctions (BTJs) so that only the fundamental Gaussian mode can sustain. For these VCSELs, a mode-hop free continuous tuning over 100 nm has already been demonstrated, which is achieved by electro-thermal tuning of the MEMS mirror. The fiber-coupled optical power of 2mW over the entire tuning range has been reported. The singlemode laser emission has more than 40 dB of side-mode suppression ratio (SMSR). The smallest linewidth achieved with these of MEMS tunable VCSELs is 98MHz which is one order of magnitude higher than that of fixed-wavelength VCSELs.

Development of solid tunable optics for ultra-miniature imaging systems

NASA Astrophysics Data System (ADS)

Yongchao, Zou

This thesis focuses on the optimal design, fabrication and testing of solid tunable optics and exploring their applications in miniature imaging systems. It starts with the numerical modelling of such lenses, followed by the optimum design method and alignment tolerance analysis. A miniature solid tunable lens driven by a piezo actuator is then developed. To solve the problem of limited maximum optical power and tuning range in conventional lens designs, a novel multi-element solid tunable lens is proposed and developed. Inspired by the Alvarez principle, a novel miniature solid tunable dual-focus lens, which is designed using freeform surfaces and driven by one micro-electro-mechanical-systems (MEMS) rotary actuator, is demonstrated. To explore the applications of these miniature solid tunable lenses, a miniature adjustable-focus endoscope and one compact adjustable-focus camera module are developed. The adjustable-focus capability of these two miniature imaging systems is fully proved by electrically focusing targets placed at different positions.

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

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

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

DOE PAGES

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei; ...

2018-05-12

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Devetter, Brent M.; Mukherjee, Prabuddha; Murphy, Catherine J.; Bhargava, Rohit

2015-05-01

Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min-1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes.Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min-1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01006c

Superhydrophobic Surface With Shape Memory Micro/Nanostructure and Its Application in Rewritable Chip for Droplet Storage.

PubMed

Lv, Tong; Cheng, Zhongjun; Zhang, Dongjie; Zhang, Enshuang; Zhao, Qianlong; Liu, Yuyan; Jiang, Lei

2016-09-21

Recently, superhydrophobic surfaces with tunable wettability have aroused much attention. Noticeably, almost all present smart performances rely on the variation of surface chemistry on static micro/nanostructure, to obtain a surface with dynamically tunable micro/nanostructure, especially that can memorize and keep different micro/nanostructures and related wettabilities, is still a challenge. Herein, by creating micro/nanostructured arrays on shape memory polymer, a superhydrophobic surface that has shape memory ability in changing and recovering its hierarchical structures and related wettabilities was reported. Meanwhile, the surface was successfully used in the rewritable functional chip for droplet storage by designing microstructure-dependent patterns, which breaks through current research that structure patterns cannot be reprogrammed. This article advances a superhydrophobic surface with shape memory hierarchical structure and the application in rewritable functional chip, which could start some fresh ideas for the development of smart superhydrophobic surface.

Composition-Tunable Optical Properties of Zn x Cd(1 - x)S Quantum Dot-Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

NASA Astrophysics Data System (ADS)

Mansur, Alexandra A. P.; Mansur, Herman S.; Caires, Anderson J.; Mansur, Rafael L.; Oliveira, Luiz C.

2017-07-01

Quantum dots (QDs) are colloidal semiconductor nanocrystals with unique properties that can be engineered by controlling the nanoparticle size and chemical composition by doping and alloying strategies. However, due to their potential toxicity, augmenting their biocompatibility is yet a challenge for expanding to several biomedical and environmentally friendly applications. Thus, the main goal of this study was to develop composition-tunable and biocompatible Zn x Cd1 - x S QDs using carboxymethylcellulose polysaccharide as direct capping ligand via green colloidal aqueous route at neutral pH and at room temperature for potential biomedical and environmental applications. The ternary alloyed QDs were extensively characterized using UV-vis spectroscopy, photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), and X-ray photoelectrons spectroscopy (XPS). The results indicated that Zn x Cd(1 - x)S QDs were surface stabilized by carboxymethylcellulose biopolymer with spherical morphology for all composition of alloys and narrow sizes distributions ranging from 4 to 5 nm. The XRD results indicated that monophasic ternary alloyed Zn x Cd1 - x S nanocrystals were produced with homogenous composition of the core as evidenced by EELS and XPS analyses. In addition, the absorption and emission optical properties of Zn x Cd1 - x S QDs were red shifted with increasing the amount of Cd2+ in the alloyed nanocrystals, which have also increased the quantum yield compared to pure CdS and ZnS nanoparticles. These properties of alloyed nanomaterials were interpreted based on empirical model of Vegard's law and chemical bond model (CBM). As a proof of concept, these alloyed-QD conjugates were tested for biomedical and environmental applications. The results demonstrated that they were non-toxic and effective fluorophores for bioimaging live HEK293T cells (human embryonic kidney cells) using confocal laser scanning fluorescence microscopy. Moreover, these conjugates presented photocatalytic activity for photodegradation of methylene blue used as model organic industrial pollutant in water. Hence, composition-tunable optical properties of ternary Zn x Cd1 - x S ( x = 0-1) fluorescent alloyed QDs was achieved using a facile eco-friendly aqueous processing route, which can offer promising alternatives for developing innovative nanomaterials for applications in nanomedicine and environmental science and technology.

Persistently Auxetic Materials: Engineering the Poisson Ratio of 2D Self-Avoiding Membranes under Conditions of Non-Zero Anisotropic Strain.

PubMed

Ulissi, Zachary W; Govind Rajan, Ananth; Strano, Michael S

2016-08-23

Entropic surfaces represented by fluctuating two-dimensional (2D) membranes are predicted to have desirable mechanical properties when unstressed, including a negative Poisson's ratio ("auxetic" behavior). Herein, we present calculations of the strain-dependent Poisson ratio of self-avoiding 2D membranes demonstrating desirable auxetic properties over a range of mechanical strain. Finite-size membranes with unclamped boundary conditions have positive Poisson's ratio due to spontaneous non-zero mean curvature, which can be suppressed with an explicit bending rigidity in agreement with prior findings. Applying longitudinal strain along a singular axis to this system suppresses this mean curvature and the entropic out-of-plane fluctuations, resulting in a molecular-scale mechanism for realizing a negative Poisson's ratio above a critical strain, with values significantly more negative than the previously observed zero-strain limit for infinite sheets. We find that auxetic behavior persists over surprisingly high strains of more than 20% for the smallest surfaces, with desirable finite-size scaling producing surfaces with negative Poisson's ratio over a wide range of strains. These results promise the design of surfaces and composite materials with tunable Poisson's ratio by prestressing platelet inclusions or controlling the surface rigidity of a matrix of 2D materials.

Annealing temperature dependent reversible wettability switching of micro/nano structured ZnO superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Velayi, Elmira; Norouzbeigi, Reza

2018-05-01

Superhydrophobic ZnO surfaces with reversibly tunable wettability were fabricated on stainless steel meshes via a facile chemical bath deposition method just by regulating the micro/nano structured ZnO needles without using chemical post modifications. The obtained surfaces can be easily and reversibly switched between superhydrophobic and superhydrophilic/underwater superoleophobic characteristics by altering the annealing temperatures. As-prepared sample exhibited long-term superhydrophobic properties with a water contact angle (WCA) of 163.8° ± 1.8° and contact angle hysteresis (CAH) of 1.1° ± 0.8°. The SEM, XRD, XPS and Raman analyses were employed to characterize the morphological features and surface chemistry of the prepared samples. SEM images showed the formation of ZnO micro/nanoneedles with a diameter of ∼90 nm on the substrate. The superhydrophobic ZnO surface was switched to highly hydrophilic and underwater superoleophobic properties with an oil contact angle (OCA) of about 172.5° after being annealed at 400 °C in air for 30 min and restored to superhydrophobic state again by altering the annealing temperature to 150 °C. Mechanical durability of the ZnO superhydrophobic surface was tested by an abrasion test. Results confirmed that the prepared surface exhibited an excellent robustness after 20 abrasion cycles under the pressure of 4.7 kPa.

Switchable molecular magnets

PubMed Central

SATO, Osamu

2012-01-01

Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes. PMID:22728438

Controllable reflection properties of nanocomposite photonic crystals constructed by semiconductor nanocrystallites and natural periodic bio-matrices.

PubMed

Han, Jie; Su, Huilan; Song, Fang; Zhang, Di; Chen, Zhixin

2010-10-01

In this contribution, the subtle periodic nanostructures in butterfly wings and peacock feathers are applied as natural PhC matrices to in situ embed CdS nanocrystallites (nano-CdS) on the structure surface via a convenient solution process. The resulting nano-CdS/natural PhCs nanocomposites show typical 1D, quasi 1D and 2D PhC structures at the nanoscale, which is inherited from the corresponding natural periodic bio-matrices. Moreover, their reflection properties are investigated and show dependence on PhC type, structure parameter, loading amount, as well as collecting angle. This work suggests that natural periodic bio-structures could be perfect matrices to construct novel nanocomposite PhCs, whose photonic band structures are tunable and thus achieve controllable optical properties. Related ideas could inspire the design and synthesis of future nanocomposite PhCs.

New insights on laser-induced graphene electrodes for flexible supercapacitors: tunable morphology and physical properties.

PubMed

Lamberti, Andrea; Perrucci, Francesco; Caprioli, Matteo; Serrapede, Mara; Fontana, Marco; Bianco, Stefano; Ferrero, Sergio; Tresso, Elena

2017-04-28

In certain polymers the graphenization of carbon atoms can be obtained by laser writing owing to the easy absorption of long-wavelength radiation, which generates photo-thermal effects. On a polyimide surface this process allows the formation of a nanostructured and porous carbon network known as laser-induced graphene (LIG). Herein we report on the effect of the process parameters on the morphology and physical properties of LIG nanostructures. We show that the scan speed and the frequency of the incident radiation affect the gas evolution, inducing different structure rearrangements, an interesting nitrogen self-doping phenomenon and consequently different conduction properties. The materials were characterized by infrared and Raman spectroscopy, XPS elemental analysis, electron microscopy and electrical/electrochemical measurements. In particular the samples were tested as interdigitated electrodes into electrochemical supercapacitors and the optimized LIG arrangement was tested in parallel and series supercapacitor configurations to allow power exploitation.

Graphene: from synthesis to engineering to biosensor applications

NASA Astrophysics Data System (ADS)

Singh, Jagpreet; Rathi, Aditi; Rawat, Mohit; Gupta, Manoj

2018-03-01

Graphene is a fascinating material of recent origin whose first isolation was being made possible through micromechanical cleavage of a graphite crystal. Owing to its fascinating properties, graphene has garnered significant attention in the research community for multiple applications. A number of methods have been employed for the synthesis of single-layer and multi-layer graphene. The extraordinary properties of graphene such as its Hall effect at room temperature, high surface area, tunable bandgap, high charge mobility and excellent electrical, conducting and thermal properties allow for the development of sensors of various types and also opened the doors for its use in nanoelectronics, supercapacitors and batteries. Biological aspects of graphene have also been investigated with particular emphasis on its toxicity and drug delivery. In this review, many of the salient aspects of graphene, such as from synthesis to its applications, primarily focusing on sensor applications which are of current interest, are covered.

Film-Evaporation MEMS Tunable Array for Picosat Propulsion and Thermal Control

NASA Technical Reports Server (NTRS)

Alexeenko, Alina; Cardiff, Eric; Martinez, Andres; Petro, Andrew

2015-01-01

The Film-Evaporation MEMS Tunable Array (FEMTA) concept for propulsion and thermal control of picosats exploits microscale surface tension effect in conjunction with temperature- dependent vapor pressure to realize compact, tunable and low-power thermal valving system. The FEMTA is intended to be a self-contained propulsion unit requiring only a low-voltage DC power source to operate. The microfabricated thermal valving and very-high-integration level enables fast high-capacity cooling and high-resolution, low-power micropropulsion for picosats that is superior to existing smallsat micropropulsion and thermal management alternatives.

Single helically folded aromatic oligoamides that mimic the charge surface of double-stranded B-DNA

NASA Astrophysics Data System (ADS)

Ziach, Krzysztof; Chollet, Céline; Parissi, Vincent; Prabhakaran, Panchami; Marchivie, Mathieu; Corvaglia, Valentina; Bose, Partha Pratim; Laxmi-Reddy, Katta; Godde, Frédéric; Schmitter, Jean-Marie; Chaignepain, Stéphane; Pourquier, Philippe; Huc, Ivan

2018-05-01

Numerous essential biomolecular processes require the recognition of DNA surface features by proteins. Molecules mimicking these features could potentially act as decoys and interfere with pharmacologically or therapeutically relevant protein-DNA interactions. Although naturally occurring DNA-mimicking proteins have been described, synthetic tunable molecules that mimic the charge surface of double-stranded DNA are not known. Here, we report the design, synthesis and structural characterization of aromatic oligoamides that fold into single helical conformations and display a double helical array of negatively charged residues in positions that match the phosphate moieties in B-DNA. These molecules were able to inhibit several enzymes possessing non-sequence-selective DNA-binding properties, including topoisomerase 1 and HIV-1 integrase, presumably through specific foldamer-protein interactions, whereas sequence-selective enzymes were not inhibited. Such modular and synthetically accessible DNA mimics provide a versatile platform to design novel inhibitors of protein-DNA interactions.

Tunable Droplet Breakup Dynamics on Micropillared Superhydrophobic Surfaces.

PubMed

Zhang, Rui; Hao, Pengfei; Zhang, Xiwen; Niu, Fenglei; He, Feng

2018-06-22

Functional materials with controllable droplet breakup properties have extensive application prospects in aircraft anti-icing, spraying cooling, surface coating, and so on. Here we show that introducing micropillar arrays with various morphologies to fabricate superhydrophobic surfaces could either facilitate or suppress droplet splitting. The spacing and height of micropillars play an essential role in tuning the splitting patterns. Delayed splashing occurs on dense pillars which support the liquid lamella and provide channels for air to escape. A novel droplet breakup mechanism is found on sparse tall pillars, which rises from the instability of lateral liquid jets and significantly reduces the droplet breakup threshold. The critical Weber number of the rupture of low-viscous liquid is solely determined by the geometric parameters of micropillars and droplets. This work unveils the impact of ordered microstructures on the droplet breakup dynamics and provides a quantitative analysis of the geometric parameters in revising the breakup criteria.

Superstretchable, Self-Healing Polymeric Elastomers with Tunable Properties

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

Cao, Peng-Fei; Li, Bingrui; Hong, Tao

Utilization of self-healing chemistry to develop synthetic polymer materials that can heal themselves with restored mechanical performance and functionality is of great interest. Self-healable polymer elastomers with tunable mechanical properties are especially attractive for a variety of applications. In this paper, a series of urea functionalized poly(dimethyl siloxane)-based elastomers (U-PDMS-Es) are reported with extremely high stretchability, self-healing mechanical properties, and recoverable gas-separation performance. Tailoring the molecular weights of poly(dimethyl siloxane) or weight ratio of elastic cross-linker offers tunable mechanical properties of the obtained U-PDMS-Es, such as ultimate elongation (from 984% to 5600%), Young's modulus, ultimate tensile strength, toughness, and elasticmore » recovery. The U-PDMS-Es can serve as excellent acoustic and vibration damping materials over a broad range of temperature (over 100 °C). The strain-dependent elastic recovery behavior of U-PDMS-Es is also studied. After mechanical damage, the U-PDMS-Es can be healed in 120 min at ambient temperature or in 20 min at 40 °C with completely restored mechanical performance. Lastly, the U-PDMS-Es are also demonstrated to exhibit recoverable gas-separation functionality with retained permeability/selectivity after being damaged.« less

Superstretchable, Self-Healing Polymeric Elastomers with Tunable Properties

DOE PAGES

Cao, Peng-Fei; Li, Bingrui; Hong, Tao; ...

2018-04-16

Utilization of self-healing chemistry to develop synthetic polymer materials that can heal themselves with restored mechanical performance and functionality is of great interest. Self-healable polymer elastomers with tunable mechanical properties are especially attractive for a variety of applications. In this paper, a series of urea functionalized poly(dimethyl siloxane)-based elastomers (U-PDMS-Es) are reported with extremely high stretchability, self-healing mechanical properties, and recoverable gas-separation performance. Tailoring the molecular weights of poly(dimethyl siloxane) or weight ratio of elastic cross-linker offers tunable mechanical properties of the obtained U-PDMS-Es, such as ultimate elongation (from 984% to 5600%), Young's modulus, ultimate tensile strength, toughness, and elasticmore » recovery. The U-PDMS-Es can serve as excellent acoustic and vibration damping materials over a broad range of temperature (over 100 °C). The strain-dependent elastic recovery behavior of U-PDMS-Es is also studied. After mechanical damage, the U-PDMS-Es can be healed in 120 min at ambient temperature or in 20 min at 40 °C with completely restored mechanical performance. Lastly, the U-PDMS-Es are also demonstrated to exhibit recoverable gas-separation functionality with retained permeability/selectivity after being damaged.« less

Shape-Persistent, Thermoresponsive Polypeptide Brushes Prepared by Vapor Deposition Surface-Initiated Ring-Opening Polymerization of α-Amino Acid N -Carboxyanhydrides

DOE PAGES

Shen, Yong; Desseaux, Solenne; Aden, Bethany; ...

2015-04-20

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

Quantum strain sensor with a topological insulator HgTe quantum dot

PubMed Central

Korkusinski, Marek; Hawrylak, Pawel

2014-01-01

We present a theory of electronic properties of HgTe quantum dot and propose a strain sensor based on a strain-driven transition from a HgTe quantum dot with inverted bandstructure and robust topologically protected quantum edge states to a normal state without edge states in the energy gap. The presence or absence of edge states leads to large on/off ratio of conductivity across the quantum dot, tunable by adjusting the number of conduction channels in the source-drain voltage window. The electronic properties of a HgTe quantum dot as a function of size and applied strain are described using eight-band Luttinger and Bir-Pikus Hamiltonians, with surface states identified with chirality of Luttinger spinors and obtained through extensive numerical diagonalization of the Hamiltonian. PMID:24811674

Enhanced selectivity for the hydrolysis of block copoly(2-oxazoline)s in ethanol-water resulting in linear poly(ethylene imine) copolymers.

PubMed

van Kuringen, Huub P C; de la Rosa, Victor R; Fijten, Martin W M; Heuts, Johan P A; Hoogenboom, Richard

2012-05-14

The ability of merging the properties of poly(2-oxazoline)s and poly(ethylene imine) is of high interest for various biomedical applications, including gene delivery, biosensors, and switchable surfaces and nanoparticles. In the present research, a methodology for the controlled and selective hydrolysis of (co)poly(2-oxazoline)s is developed in an ethanol-water solvent mixture, opening the path toward a wide range of block poly(2-oxazoline-co-ethylene imine) (POx-PEI) copolymers with tunable properties. The unexpected influence of the selected ethanol-water binary solvent mixture on the hydrolysis kinetics and selectivity is highlighted in the pursue of well-defined POx-PEI block copolymers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solvent-induced synthesis of nitrogen-doped hollow carbon spheres with tunable surface morphology for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Feng; Yuan, Ren-Lu; Zhang, Ning; Ke, Chang-Ce; Ma, Shao-Xia; Zhang, Ru-Liang; Liu, Lei

2018-04-01

Nitrogen doped hollow carbon spheres (NHCSs) with tunable surface morphology have been prepared through one-pot carbonization method by using melamine-formaldehyde spheres as template and resorcinol-based resin as carbon precursor in ethanol-water solution. Well-dispersed NHCSs with particle size of 800 nm were obtained and the surface of NHCSs turn from smooth to tough, wrinkled, and finally concave by increasing the ethanol concentration. The fabricated NHCSs possessed high nitrogen content (3.99-4.83%) and hierarchical micro-dual mesoporous structure with surface area range of 265-405 m2 g-1 and total pore volume of 0.18-0.29 cm3 g-1, which contributed to high specific capacitance, excellent rate capability and long cycle life.

Multilayer thin films with compositional PbZr0.52Ti0.48O3/Bi1.5Zn1.0Nb1.5O7 layers for tunable applications

PubMed Central

Yu, Shihui; Li, Lingxia; Zhang, Weifeng; Sun, Zheng; Dong, Helei

2015-01-01

The dielectric properties and tunability of multilayer thin films with compositional PbZr0.52Ti0.48O3/Bi1.5Zn1.0Nb1.5O7 (PZT/BZN) layers (PPBLs) fabricated by pulsed laser deposition on Pt/TiO2/SiO2/Si substrate have been investigated. Dielectric measurements indicate that the PZT/BZN bilayer thin films exhibit medium dielectric constant of about 490, low loss tangent of 0.017, and superior tunable dielectric properties (tunability = 49.7% at 500 kV/cm) at a PZT/BZN thickness ratio of 3, while the largest figure of merit is obtained as 51.8. The thickness effect is discussed with a series connection model of bilayer capacitors, and the calculated dielectric constant and loss tangent are obtained. Furthermore, five kinds of thin–film samples comprising single bilayers, two, three, four and five PPBLs were also elaborated with the final same thickness. The four PPBLs show the largest dielectric constant of ~538 and tunability of 53.3% at a maximum applied bias field of 500 kV/cm and the lowest loss tangent of ~0.015, while the largest figure of merit is 65.6. The results indicate that four PPBLs are excellent candidates for applications of tunable devices. PMID:25960043

Multichannel tunable omnidirectional photonic band gaps of 1D ternary photonic crystal containing magnetized cold plasma

NASA Astrophysics Data System (ADS)

Awasthi, Suneet Kumar; Panda, Ranjita; Chauhan, Prashant Kumar; Shiveshwari, Laxmi

2018-05-01

By using the transfer matrix method, theoretical investigations have been carried out in the microwave region to study the reflection properties of multichannel tunable omnidirectional photonic bandgaps (OPBGs) based on the magneto-optic Faraday effect. The proposed one dimensional ternary plasma photonic crystal consists of alternate layers of quartz, magnetized cold plasma (MCP), and air. In the absence of an external magnetic field, the proposed structure possesses two OPBGs induced by Bragg scattering and is strongly dependent on the incident angle, the polarization of the incident light, and the lattice constant unlike to the single-negative gap and zero- n ¯ gap. Next, the reflection properties of OPBGs have been made tunable by the application of external magnetic field under right hand and left hand polarization configurations. The results of this manuscript may be utilized for the development of a new kind of tunable omnidirectional band stop filter with ability to completely stop single to multiple bands (called channels) of microwave frequencies in the presence of external static magnetic field under left-hand polarization and right-hand polarization configurations, respectively. Moreover, outcomes of this study open a promising way to design tunable magneto-optical devices, omnidirectional total reflectors, and planar waveguides of high Q microcavities as a result of evanescent fields in the MCP layer to allow propagation of light.

Rational Design of Hyperbranched Nanowire Systems for Tunable Superomniphobic Surfaces Enabled by Atomic Layer Deposition

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

Bielinski, Ashley R.; Boban, Mathew; He, Yang

2017-01-24

A method for tunable control of geometry in hyperbranched ZnO nanowire (NW) systems is reported, which enables the rational design and fabrication of superomniphobic surfaces. Branched NWs with tunable density and orientation were grown via a sequential hydrothermal process, in which atomic layer deposition (ALD) was used for NW seeding, disruption of epitaxy, and selective blocking of NW nucleation. This approach allows for the rational design and optimization of three-level hierarchical structures, in which the geometric parameters of each level of hierarchy can be individually controlled. We demonstrate the coupled relationships between geometry and contact angle for a variety ofmore » liquids, which is supported by mathematical models of structural superomniphobicity. The highest performing superomniphobic surface was designed with three levels of hierarchy and achieved the following advancing/receding contact angles, water: 172°/170°, hexadecane: 166°/156°, octane: 162°/145°, and heptane: 160°/130°. Low surface tension liquids were shown to bounce off the surface from a height of 7 cm without breaking through and wetting. This approach demonstrates the power of ALD as an enabling technique for hierarchical materials by design, spanning the macro, micro, and nano length scales.« less

Electrotunable nanoplasmonic liquid mirror

NASA Astrophysics Data System (ADS)

Montelongo, Yunuen; Sikdar, Debabrata; Ma, Ye; McIntosh, Alastair J. S.; Velleman, Leonora; Kucernak, Anthony R.; Edel, Joshua B.; Kornyshev, Alexei A.

2017-11-01

Recently, there has been a drive to design and develop fully tunable metamaterials for applications ranging from new classes of sensors to superlenses among others. Although advances have been made, tuning and modulating the optical properties in real time remains a challenge. We report on the first realization of a reversible electrotunable liquid mirror based on voltage-controlled self-assembly/disassembly of 16 nm plasmonic nanoparticles at the interface between two immiscible electrolyte solutions. We show that optical properties such as reflectivity and spectral position of the absorption band can be varied in situ within +/-0.5 V. This observed effect is in excellent agreement with theoretical calculations corresponding to the change in average interparticle spacing. This electrochemical fully tunable nanoplasmonic platform can be switched from a highly reflective `mirror' to a transmissive `window' and back again. This study opens a route towards realization of such platforms in future micro/nanoscale electrochemical cells, enabling the creation of tunable plasmonic metamaterials.

GATG dendrimers and PEGylated block copolymers: from synthesis to bioapplications.

PubMed

Sousa-Herves, Ana; Novoa-Carballal, Ramon; Riguera, Ricardo; Fernandez-Megia, Eduardo

2014-09-01

Dendrimers are synthetic macromolecules composed of repetitive layers of branching units that emerge from a central core. They are characterized by a tunable size and precise number of peripheral groups which determine their physicochemical properties and function. Their high multivalency, functional surface, and globular architecture with diameters in the nanometer scale makes them ideal candidates for a wide range of applications. Gallic acid-triethylene glycol (GATG) dendrimers have attracted our attention as a promising platform in the biomedical field because of their high tunability and versatility. The presence of terminal azides in GATG dendrimers and poly(ethylene glycol) (PEG)-dendritic block copolymers allows their efficient functionalization with a variety of ligands of biomedical relevance including anionic and cationic groups, carbohydrates, peptides, or imaging agents. The resulting functionalized dendrimers have found application in drug and gene delivery, as antiviral agents and for the treatment of neurodegenerative diseases, in diagnosis and as tools to study multivalent carbohydrate recognition and dendrimer dynamics. Herein, we present an account on the preparation and recent applications of GATG dendrimers in these fields.

Electric-field control of magnetic moment in Pd

PubMed Central

Obinata, Aya; Hibino, Yuki; Hayakawa, Daichi; Koyama, Tomohiro; Miwa, Kazumoto; Ono, Shimpei; Chiba, Daichi

2015-01-01

Several magnetic properties have recently become tunable with an applied electric field. Particularly, electrically controlled magnetic phase transitions and/or magnetic moments have attracted attention because they are the most fundamental parameters in ferromagnetic materials. In this study, we showed that an electric field can be used to control the magnetic moment in films made of Pd, usually a non-magnetic element. Pd ultra-thin films were deposited on ferromagnetic Pt/Co layers. In the Pd layer, a ferromagnetically ordered magnetic moment was induced by the ferromagnetic proximity effect. By applying an electric field to the ferromagnetic surface of this Pd layer, a clear change was observed in the magnetic moment, which was measured directly using a superconducting quantum interference device magnetometer. The results indicate that magnetic moments extrinsically induced in non-magnetic elements by the proximity effect, as well as an intrinsically induced magnetic moments in ferromagnetic elements, as reported previously, are electrically tunable. The results of this study suggest a new avenue for answering the fundamental question of “can an electric field make naturally non-magnetic materials ferromagnetic?” PMID:26391306

Tissue-engineered cartilage with inducible and tunable immunomodulatory properties.

PubMed

Glass, Katherine A; Link, Jarrett M; Brunger, Jonathan M; Moutos, Franklin T; Gersbach, Charles A; Guilak, Farshid

2014-07-01

The pathogenesis of osteoarthritis is mediated in part by inflammatory cytokines including interleukin-1 (IL-1), which promote degradation of articular cartilage and prevent human mesenchymal stem cell (MSC) chondrogenesis. In this study, we combined gene therapy and functional tissue engineering to develop engineered cartilage with immunomodulatory properties that allow chondrogenesis in the presence of pathologic levels of IL-1 by inducing overexpression of IL-1 receptor antagonist (IL-1Ra) in MSCs via scaffold-mediated lentiviral gene delivery. A doxycycline-inducible vector was used to transduce MSCs in monolayer or within 3D woven PCL scaffolds to enable tunable IL-1Ra production. In the presence of IL-1, IL-1Ra-expressing engineered cartilage produced cartilage-specific extracellular matrix, while resisting IL-1-induced upregulation of matrix metalloproteinases and maintaining mechanical properties similar to native articular cartilage. The ability of functional engineered cartilage to deliver tunable anti-inflammatory cytokines to the joint may enhance the long-term success of therapies for cartilage injuries or osteoarthritis. Copyright © 2014 Elsevier Ltd. All rights reserved.

A facile strategy to design zeolite L crystals with tunable morphology and surface architecture.

PubMed

Lupulescu, Alexandra I; Kumar, Manjesh; Rimer, Jeffrey D

2013-05-01

Tailoring the anisotropic growth rates of materials to achieve desired structural outcomes is a pervasive challenge in synthetic crystallization. Here we discuss a method to selectively control the growth of zeolite crystals, which are used extensively in a wide range of industrial applications. This facile method cooperatively tunes crystal properties, such as morphology and surface architecture, through the use of inexpensive, commercially available chemicals with specificity for binding to crystallographic surfaces and mediating anisotropic growth. We examined over 30 molecules as potential zeolite growth modifiers (ZGMs) of zeolite L (LTL type) crystallization. ZGM efficacy was quantified through a combination of macroscopic (bulk) and microscopic (surface) investigations that identified modifiers capable of dramatically altering the cylindrical morphology of LTL crystals. We demonstrate an ability to tailor properties critical to zeolite performance, such as external porous surface area, crystal shape, and pore length, which can enhance sorbate accessibility to LTL pores, tune the supramolecular organization of guest-host composites, and minimize the diffusion path length, respectively. We report that a synergistic combination of ZGMs and the judicious adjustment of synthesis parameters produce LTL crystals with unique surface features, and a range of length-to-diameter aspect ratios spanning 3 orders of magnitude. A systematic examination of different ZGM structures and molecular compositions (i.e., hydrophobicity and binding moieties) reveal interesting physicochemical properties governing their efficacy and specificity. Results of this study suggest this versatile strategy may prove applicable for a host of framework types to produce unrivaled materials that have eluded more conventional techniques.

Transparent nanocellulosic multilayer thin films on polylactic acid with tunable gas barrier properties.

PubMed

Aulin, Christian; Karabulut, Erdem; Tran, Amy; Wågberg, Lars; Lindström, Tom

2013-08-14

The layer-by-layer (LbL) deposition method was used for the build-up of alternating layers of nanofibrillated cellulose (NFC) or carboxymethyl cellulose (CMC) with a branched, cationic polyelectrolyte, polyethyleneimine (PEI) on flexible poly (lactic acid) (PLA) substrates. With this procedure, optically transparent nanocellulosic films with tunable gas barrier properties were formed. 50 layer pairs of PEI/NFC and PEI/CMC deposited on PLA have oxygen permeabilities of 0.34 and 0.71 cm(3)·μm/m(2)·day·kPa at 23 °C and 50% relative humidity, respectively, which is in the same range as polyvinyl alcohol and ethylene vinyl alcohol. The oxygen permeability of these multilayer nanocomposites outperforms those of pure NFC films prepared by solvent-casting. The nanocellulosic LbL assemblies on PLA substrates was in detailed characterized using a quartz crystal microbalance with dissipation (QCM-D). Atomic force microscopy (AFM) reveals large structural differences between the PEI/NFC and the PEI/CMC assemblies, with the PEI/NFC assembly showing a highly entangled network of nanofibrils, whereas the PEI/CMC surfaces lacked structural features. Scanning electron microscopy images showed a nearly perfect uniformity of the nanocellulosic coatings on PLA, and light transmittance results revealed remarkable transparency of the LbL-coated PLA films. The present work demonstrates the first ever LbL films based on high aspect ratio, water-dispersible nanofibrillated cellulose, and water-soluble carboxymethyl cellulose polymers that can be used as multifunctional films and coatings with tailorable properties, such as gas barriers and transparency. Owing to its flexibility, transparency and high-performance gas barrier properties, these thin film assemblies are promising candidates for several large-scale applications, including flexible electronics and renewable packaging.

Fabrication of a nano-cone array on a p-GaN surface for enhanced light extraction efficiency from GaN-based tunable wavelength LEDs.

PubMed

Soh, C B; Wang, B; Chua, S J; Lin, Vivian K X; Tan, Rayson J N; Tripathy, S

2008-10-08

We report on the fabrication of a nano-cone structured p-GaN surface for enhanced light extraction from tunable wavelength light emitting diodes (LEDs). Prior to p-contact metallization, self-assembled colloidal particles are deposited and used as a mask for plasma etching to create nano-cone structures on the p-GaN layer of LEDs. A well-defined periodic nano-cone array, with an average cone diameter of 300 nm and height of 150 nm, is generated on the p-GaN surface. The photoluminescence emission intensity recorded from the regions with the nano-cone array is increased by two times as compared to LEDs without surface patterning. The light output power from the LEDs with surface nano-cones shows significantly higher electroluminescence intensity at an injection current of 70 mA. This is due to the internal multiple scattering of light from the nano-cone sidewalls. Furthermore, we have shown that with an incorporation of InGaN nanostructures in the quantum well, the wavelength of these surface-patterned LEDs can be tuned from 517 to 488 nm with an increase in the injection current. This methodology may serve as a practical approach to increase the light extraction efficiency from wavelength tunable LEDs.

Surface plasmon resonance enhanced light absorption and wavelength tuneable in gold-coated iron oxide spherical nanoparticle

NASA Astrophysics Data System (ADS)

Dasri, Thananchai; Chingsungnoen, Artit

2018-06-01

Surface plasmon in nano-sized particles, such as gold, silver, copper and their composites, has recently attracted a great deal of attention due to its possible uses in many applications, especially in life sciences. It is desirable for application devices with a tenability of surface plasmon wavelength and optical properties enhancement. This article presents enhanced optical light absorption and tunable wavelength in gold-coated magnetite (Fe3O4@Au core-shell) nanoparticles embedded in water using the theoretical method of discrete dipole approximation (DDA). The absorption spectra in the wavelengths from 350 to 900 nm were found to be the spectra obtained from Fe3O4@Au core-shell nanoparticles, and when compared with pure Fe3O4 nanoparticles, the surface plasmon resonance can be enhanced and tuned over the entire visible spectrum (viz. 350-800 nm) of the electromagnetic spectrum by varying the Au shell thickness (2-5 nm). Similarly, the Faraday rotation spectra can also be obtained.

Ultrafast Imaging of Chiral Surface Plasmon by Photoemission Electron Microscopy

NASA Astrophysics Data System (ADS)

Dai, Yanan; Dabrowski, Maciej; Petek, Hrvoje

We employ Time-Resolved Photoemission Electron Microscopy (TR-PEEM) to study surface plasmon polariton (SPP) wave packet dynamics launched by tunable (VIS-UV) femtosecond pulses of various linear and circular polarizations. The plasmonic structures are micron size single-crystalline Ag islands grown in situ on Si surfaces and characterized by Low Energy Electron Microscopy (LEEM). The local fields of plasmonic modes enhance two and three photon photoemission (2PP and 3PP) at the regions of strong field enhancement. Imaging of the photoemission signal with PEEM electron optics thus images the plasmonic fields excited in the samples. The observed PEEM images with left and right circularly polarized light show chiral images, which is a consequence of the transverse spin momentum of surface plasmon. By changing incident light polarization, the plasmon interference pattern shifts with light ellipticity indicating a polarization dependent excitation phase of SPP. In addition, interferometric-time resolved measurements record the asymmetric SPP wave packet motion in order to characterize the dynamical properties of chiral SPP wave packets.

Biomimetic honeycomb-patterned surface as the tunable cell adhesion scaffold.

PubMed

Chen, Shuangshuang; Lu, Xuemin; Hu, Ying; Lu, Qinghua

2015-01-01

Inspired by the typically adhesive behaviors of fish skin and Parthenocissus tricuspidata, two different decorations of polystyrene honeycomb membrane (PSHCM) prepared by the breath figure approach were carried out with poly(N-(3-Sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine)(polySBMA) to explore controllable bioadhesive surfaces. Casting and dip-coating were employed to graft polySBMA onto the plasma treated PSHCM. The polySBMA casted PSHCM showed a uniform covering layer on the PSHCM similar to the mucus layer of fish skin, presenting excellent antifouling properties. On the contrary, a dip-coated one showed the polySBMA aggregating on the honeycomb pore walls forming a large number of sucking disks such as the adhesive disks of the tendrils of P. tricuspidata, which remarkably boosts cell adhesion on substrates. Thus, bioadhesion could be regulated as desired by tuning the distribution of zwitterionic polymer on the honeycomb surface. The results may provide a new approach for the design of biomaterial surfaces.

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

Zhuang, Jinda; Ju, Y. Sungtaek, E-mail: just@seas.ucla.edu

One major challenge in incorporating flexible electronics or optoelectronics on curved surfaces is the requirement of significant stretchability. We report a tunable platform for incorporating flexible and yet non-stretching device layers on a hemisphere. In this configuration, an array of planar petals contractively maps onto the surface of an inflatable hemisphere through elastocapillary interactions mediated by an interface liquid. A mechanical model is developed to elucidate the dependence of the conformality of the petal structures on their elastic modulus and thickness and the liquid surface tension. The modeling results are validated against experimental results obtained using petal structures of differentmore » thicknesses, restoring elastic spring elements of different spring constants, and liquids with different surface tension coefficients. Our platform will enable facile integration of non-stretching electronic and optoelectronic components prepared using established planar fabrication techniques on tunable hemispherical surfaces.« less

Interfacial synthesis of polyethyleneimine-protected copper nanoclusters: Size-dependent tunable photoluminescence, pH sensor and bioimaging.

PubMed

Wang, Chan; Yao, Yagang; Song, Qijun

2016-04-01

The copper nanoclusters (CuNCs) offer excellent potential as functional biological probes due to their unique photoluminescence (PL) properties. Herein, CuNCs capped with hyperbranched polyethylenimine (PEI) were prepared by the interfacial etching approach. The resultant PEI-CuNCs exhibited good dispersion and strong fluorescence with high quantum yields (QYs, up to 7.5%), which would be endowed for bioimaging system. By changing the reaction temperatures from 25 to 150 °C, the size of PEI-CuNCs changed from 1.8 to 3.5 nm, and thus tunable PL were achieved, which was confirmed by transmission electron microscopy (TEM) imagings and PL spectra. Besides, PEI-CuNCs had smart absorption characteristics that the color changes from colorless to blue with changing the pH value from 2.0 to 13.2, and thus they could be used as color indicator for pH detection. In addition, the PEI-CuNCs exhibited good biocompatibility and low cytotoxicity to 293T cells through MTT assay. Owing to the positively charged of PEI-CuNCs surface, they had the ability to capture DNA, and the PEI-CuNCs/DNA complexes could get access to cells for efficient gene expression. Armed with these attractive properties, the synthesized PEI-CuNCs are quite promising in biological applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Polysaccharide-based hydrogels with tunable composition as 3D cell culture systems.

PubMed

Gentilini, Roberta; Munarin, Fabiola; Bloise, Nora; Secchi, Eleonora; Visai, Livia; Tanzi, Maria Cristina; Petrini, Paola

2018-04-01

To date, cell cultures have been created either on 2-dimensional (2D) polystyrene surfaces or in 3-dimensional (3D) systems, which do not offer a controlled chemical composition, and which lack the soft environment encountered in vivo and the chemical stimuli that promote cell proliferation and allow complex cellular behavior. In this study, pectin-based hydrogels were developed and are proposed as versatile cell culture systems. Pectin-based hydrogels were produced by internally crosslinking pectin with calcium carbonate at different initial pH, aiming to control crosslinking kinetics and degree. Additionally, glucose and glutamine were added as additives, and their effects on the viscoelastic properties of the hydrogels and on cell viability were investigated. Pectin hydrogels showed in high cell viability and shear-thinning behavior. Independently of hydrogel composition, an initial swelling was observed, followed by a low percentage of weight variation and a steady-state stage. The addition of glucose and glutamine to pectin-based hydrogels rendered higher cell viability up to 90%-98% after 1 hour of incubation, and these hydrogels were maintained for up to 7 days of culture, yet no effect on viscoelastic properties was detected. Pectin-based hydrogels that offer tunable composition were developed successfully. They are envisioned as synthetic extracellular matrix (ECM) either to study complex cellular behaviors or to be applied as tissue engineering substitutes.

Electrically tunable polarizer based on graphene-loaded plasmonic cross antenna

NASA Astrophysics Data System (ADS)

Qin, Yuwei; Xiong, Xiaoyan Y. Z.; Sha, Wei E. I.; Jiang, Li Jun

2018-04-01

The unique gate-voltage dependent optical properties of graphene make it a promising electrically-tunable plasmonic material. In this work, we proposed in situ control of the polarization of nanoantennas by combining plasmonic structures with an electrostatically tunable graphene monolayer. The tunable polarizer is designed based on an asymmetric cross nanoantenna comprising two orthogonal metallic dipoles sharing the same feed gap. Graphene monolayer is deposited on a Si/SiO2 substrate, and inserted beneath the nanoantenna. Our modelling demonstrates that as the chemical potential is incremented up to 1 eV by electrostatic doping, resonant wavelength for the longer graphene-loaded dipole is blue shifted for 500 nm (~10% of the resonance) in the mid-infrared range, whereas the shorter dipole experiences much smaller influences due to the unique wavelength-dependent optical properties of graphene. In this way, the relative field amplitude and phase between the two dipole nanoantennas are electrically adjusted, and the polarization state of the reflected wave can be electrically tuned from the circular into near-linear states with the axial ratio changing over 8 dB. Our study thus confirms the strong light-graphene interaction with metallic nanostructures, and illuminates promises for high-speed electrically controllable optoelectronic devices.

Highly efficient synthesis of ordered nitrogen-doped mesoporous carbons with tunable properties and its application in high performance supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Dan; Zeng, Chao; Qu, Deyu; Tang, Haolin; Li, Yu; Su, Bao-Lian; Qu, Deyang

2016-07-01

Nitrogen-doped ordered mesoporous carbons (OMCs) have been synthesized via aqueous cooperative assembly route in the presence of basic amino acids as either polymerization catalysts or nitrogen dopants. This method allows the large-scale production of nitrogen-doped OMCs with tunable composition, structure and morphology while maintaining highly ordered mesostructures. For instances, the nitrogen content can be varied from ∼1 wt% to ∼6.3 wt% and the mesophase can be either 3-D body-centered cubic or 2-D hexagonal. The specific surface area for typical OMCs is around 600 m2 g-1, and further KOH activation can significantly enhance the surface area to 1866 m2 g-1 without destroying the ordered mesostructures. Benefiting from hierarchically ordered porous structure, nitrogen-doping effect and large-scale production availability, the synthesized OMCs show a great potential towards supercapacitor application. When measured in a symmetrical two-electrode configuration with an areal mass loading of ∼3 mg cm-2, the activated OMC exhibits high capacitance (186 F g-1 at 0.25 A g-1) and good rate capability (75% capacity retention at 20 A g-1) in ionic liquid electrolyte. Even as the mass loading is up to ∼12 mg cm-2, the OMC electrode still yields a specific capacitance of 126 F g-1 at 20 A g-1.

Pt/glassy carbon model catalysts prepared from PS-b-P2VP micellar templates.

PubMed

Gu, Yunlong; St-Pierre, Jean; Ploehn, Harry J

2008-11-04

Poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer was used as a micellar template to fabricate arrays of Pt nanoparticles on mica and glassy carbon (GC) supports. Polymer micellar deposition yields Pt nanoparticles with tunable particle size and surface number density on both mica and GC. After deposition of precursor-loaded micelles onto GC, oxygen plasma etching removes the polymer shell, followed by thermal treatment with H2 gas to reduce the Pt. Etching conditions were optimized to maximize removal of the polymer while minimizing damage to the GC. Arrays of Pt nanoparticles with controlled size and surface number density can be prepared on mica (for particle size characterization) and GC to make Pt/GC model catalysts. These model catalysts were characterized by tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry to measure activity for oxidation of carbon monoxide or methanol. Cyclic voltammetry results demonstrate the existence of a correlation between Pt particle size and electrocatalytic properties including onset potential, tolerance of carbonaceous adsorbates, and intrinsic activity (based on active Pt area from CO stripping voltammetry). Results obtained with Pt/GC model catalysts duplicate prior results obtained with Pt/porous carbon catalysts therefore validating the synthesis approach and offering a new, tunable platform to study catalyst structure and other effects such as aging on proton exchange membrane fuel cell (PEMFC) reactions.

Self-Supporting Nanodiamond Gels: Elucidating Colloidal Interactions Through Rheology_

NASA Astrophysics Data System (ADS)

Adhikari, Prajesh; Tripathi, Anurodh; Vogel, Nancy A.; Rojas, Orlando J.; Raghavan, Sriunivasa R.; Khan, Saad A.

This work investigates the colloidal interactions and rheological behavior of nanodiamond (ND) dispersions. While ND represents a promising class of nanofiller due to its high surface area, superior mechanical strength, tailorable surface functionality and biocompatibility, much remains unknown about the behavior of ND dispersions. We hypothesize that controlling interactions in ND dispersions will lead to highly functional systems with tunable modulus and shear response. Steady and dynamic rheology techniques are thus employed to systematically investigate nanodiamonds dispersed in model polar and non-polar media. We find that low concentrations of ND form gels almost instantaneously in a non-polar media. In contrast, ND's in polar media show a time-dependent behavior with the modulus increasing with time. We attribute the difference in behavior to variations in inter-particle interactions as well as the interaction of the ND with the media. Large steady and oscillatory strains are applied to ND colloidal gels to investigate the role of shear in gel microstructure breakdown and recovery. For colloidal gels in non-polar medium, the incomplete recovery of elastic modulus at high strain amplitudes indicates dominance of particle-particle interactions; however, in polar media the complete recovery of elastic modulus even at high strain amplitudes indicates dominance of particle-solvent interactions. These results taken together provide a platform to develop self-supporting gels with tunable properties in terms of ND concentration, and solvent type.

Unique dielectric tunability of Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 antiferroelectric ceramics

NASA Astrophysics Data System (ADS)

Li, Lei; Spreitzer, Matjaž; Suvorov, Danilo; Chen, Xiang Ming

2016-08-01

The tunable dielectric properties of Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 antiferroelectric ceramics were investigated, and high relative tunability of 49% was obtained at 25 °C under a low bias electric field of 50 kV/cm. Abrupt changes and a significant hysteresis in dielectric constant and dielectric loss against bias electric field were observed, which are very different from the previously reported antiferroelectric materials. The unique dielectric tunability is attributed to the square-shaped double hysteresis loop and indicates the possible applications in some special tunable devices, such as an electrically-controlled switch. Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 ceramics also exhibit unique dielectric tunability at -5 °C. Abrupt changes in dielectric constant and dielectric loss were observed when the bias electric field increased to 31 kV/cm for the fresh sample, which is similar to the antiferroelectric-like dielectric tunability at 25 °C. However, the dielectric tunability was ferroelectric-like in the following measurement. This response is consistent with the hysteresis loop and can be explained by the electric field-assisted irreversible antiferroelectric-ferroelectric phase transition.

Properties of Self-Assembled Monolayers Revealed via Inverse Tensiometry.

PubMed

Chen, Jiahao; Wang, Zhengjia; Oyola-Reynoso, Stephanie; Thuo, Martin M

2017-11-28

Self-assembled monolayers (SAMs) have emerged as a simple platform technology and hence have been broadly studied. With advances in state-of-the-art fabrication and characterization methods, new insights into SAM structure and related properties have been delineated, albeit with some discrepancies and/or incoherencies. Some discrepancies, especially between experimental and theoretical work, are in part due to the misunderstanding of subtle structural features such as phase evolution and SAM quality. Recent work has, however, shown that simple techniques, such as the measurement of static contact angles, can be used to delineate otherwise complex properties of the SAM, especially when complemented by other more advanced techniques. In this article, we highlight the effect of nanoscale substrate asperities and molecular chain length on the SAM structure and associated properties. First, surfaces with tunable roughness are prepared on both Au and Ag, and their corresponding n-alkanethiolate SAMs are characterized through wetting and spectroscopy. From these data, chain-length- and substrate-morphology-dependent limits to the odd-even effect (structure and properties vary with the number of carbons in the molecules and the nature of the substrate), parametrization of gauche defect densities, and structural phase evolution (liquidlike, waxy, crystalline interfaces) are deduced. An evaluation of the correlation between the effect of roughness and the components of surface tension (polar-γ p and dispersive-γ d ) reveals that wetting, at nanoscale rough surfaces, evolves proportionally with the ratio of the two components of surface tension. The evolution of conformational order is captured over a range of molecular lengths and parametrized through a dimensionless number, χ c . By deploying a well-known tensiometry technique (herein the liquid is used to characterize the solid, hence the term inverse tensiometry) to characterize SAMs, we demonstrate that complex molecular-level phenomena in SAMs can be understood through simplicity.

Fabrication of nanoscale to macroscale nickel-multiwall carbon nanotube hybrid materials with tunable material properties

NASA Astrophysics Data System (ADS)

Abdalla, Ahmed M.; Majdi, Tahereh; Ghosh, Suvojit; Puri, Ishwar K.

2016-12-01

To utilize their superior properties, multiwall carbon nanotubes (MWNTs) must be manipulated and aligned end-to-end. We describe a nondestructive method to magnetize MWNTs and provide a means to remotely manipulate them through the electroless deposition of magnetic nickel nanoparticles on their surfaces. The noncovalent bonds between Ni nanoparticles and MWNTs produce a Ni-MWNT hybrid material (NiCH) that is electrically conductive and has an enhanced magnetic susceptibility and elastic modulus. Our experiments show that MWNTs can be plated with Ni for Ni:MWNT weight ratios of γ = 1, 7, 14 and 30, to control the material properties. The phase, atom-level, and morphological information from x-ray diffraction, energy dispersive x-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, dark field STEM, and atomic force microscopy clarify the plating process and reveal the mechanical properties of the synthesized material. Ni metalizes at the surface of the Pd catalyst, forming a continuous wavy layer that encapsulates the MWNT surfaces. Subsequently, Ni acts as an autocatalyst, allowing the plating to continue even after the original Pd catalyst has been completely covered. Raising γ increases the coating layer thickness from 10 to 150 nm, which influences the NiCH magnetic properties and tunes its elastic modulus from 12.5 to 58.7 GPa. The NiCH was used to fabricate Ni-MWNT macrostructures and tune their morphologies by changing the direction of an applied magnetic field. Leveraging the hydrophilic Ni-MWNT outer surface, a water-based conductive ink was created and used to print a conductive path that had an electrical resistivity of 5.9 Ω m, illustrating the potential of this material for printing electronic circuits.

Optical properties of metal nanoparticles embedded in amorphous silicon analysed using discrete dipole approximation

NASA Astrophysics Data System (ADS)

Fantoni, Alessandro; Fernandes, Miguel; Vygranenko, Yuri; Vieira, Manuela; Oliveira-Silva, Rui P.; Prazeres, D. M. F.; Ribeiro, Ana P. C.; Alegria, Elisabete C. B. A.

2018-02-01

Localized surface plasmons (LSP) can be excited in metal nanoparticles (NP) by UV, visible or NIR light and are described as coherent oscillation of conduction electrons. Taking advantage of the tunable optical properties of NPs, we propose the realization of a plasmonic structure, based on the LSP interaction of NP with an embedding matrix of amorphous silicon. This study is directed to define the characteristics of NP and substrate necessary to the development of a LSP proteomics sensor that, once provided immobilized antibodies on its surface, will screen the concentration of selected antigens through the determination of LSPR spectra and peaks of light absorption. Metals of interest for NP composition are: Aluminium and Gold. Recent advances in nanoparticle production techniques allow almost full control over shapes and size, permitting full control over their optical and plasmonic properties and, above all, over their responsive spectra. Analytical solution is only possible for simple NP geometries, therefore our analysis, is realized recurring to computer simulation using the Discrete Dipole Approximation method (DDA). In this work we use the free software DDSCAT to study the optical properties of metal nanoparticles embedded in an amorphous silicon matrix, as a function of size, shape, aspect-ratio and metal type. Experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.

Porous Carriers for Controlled/Modulated Drug Delivery

PubMed Central

Ahuja, G.; Pathak, K.

2009-01-01

Considerable research efforts have been directed in recent years towards the development of porous carriers as controlled drug delivery matrices because of possessing several features such as stable uniform porous structure, high surface area, tunable pore size and well-defined surface properties. Owing to wide range of useful properties porous carriers have been used in pharmaceuticals for many purposes including development of floating drug delivery systems, sustained drug delivery systems. Various types of pores like open, closed, transport and blind pores in the porous solid allow them to adsorb drugs and release them in a more reproducible and predictable manner. Pharmaceutically exploited porous adsorbents includes, silica (mesoporous), ethylene vinyl acetate (macroporous), polypropylene foam powder (microporous), titanium dioxide (nanoporous). When porous polymeric drug delivery system is placed in contact with appropriate dissolution medium, release of drug to medium must be preceded by the drug dissolution in the water filled pores or from surface and by diffusion through the water filled channels. The porous carriers are used to improve the oral bioavailability of poorly water soluble drugs, to increase the dissolution of relatively insoluble powders and conversion of crystalline state to amorphous state. PMID:20376211

Nanoparticles for Biomedical Imaging

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

Nune, Satish K.; Gunda, Padmaja; Thallapally, Praveen K.

2009-11-01

Background: Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 to 100 nm in diameter possess dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has further expanded the potential of nanoparticles as probes for molecular imaging. Objective: To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced non-specific uptake with increasedmore » spatial resolution containing stabilizers conjugated with targeting ligands. Methods: This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their applications in biomedical imaging. Conclusion: Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed. Keywords: nanoparticle synthesis, surface modification, targeting, molecular imaging, and biomedical imaging.« less

Universal Coatings Based on Zwitterionic-Dopamine Copolymer Microgels.

PubMed

Vatankhah-Varnosfaderani, Mohammad; Hu, Xiaobo; Li, Qiaoxi; Adelnia, Hossein; Ina, Maria; Sheiko, Sergei S

2018-06-05

Multifunctional coatings that adhere to chemically distinct substrates are vital in many industries, including automotive, aerospace, shipbuilding, construction, petrochemical, biomedical, and pharmaceutical. We design well-defined, nearly monodisperse microgels that integrate hydrophobic dopamine methacrylamide monomers and hydrophilic zwitterionic monomers. The dopamine functionalities operate as both intraparticle cross-linkers and interfacial binders, respectively providing mechanical strength of the coatings and their strong adhesion to different substrates. In tandem, the zwitterionic moieties enable surface hydration to empower antifouling and antifogging properties. Drop-casting of microgel suspensions in ambient as well as humid environments facilitates rapid film formation and tunable roughness through regulation of cross-linking density and deposition conditions.

Fluorescent nanoparticles based on AIE fluorogens for bioimaging.

PubMed

Yan, Lulin; Zhang, Yan; Xu, Bin; Tian, Wenjing

2016-02-07

Fluorescent nanoparticles (FNPs) have recently attracted increasing attention in the biomedical field because of their unique optical properties, easy fabrication and outstanding performance in imaging. Compared with conventional molecular probes including small organic dyes and fluorescent proteins, FNPs based on aggregation-induced emission (AIE) fluorogens have shown significant advantages in tunable emission and brightness, good biocompatibility, superb photo- and physical stability, potential biodegradability and facile surface functionalization. In this review, we summarize the latest advances in the development of fluorescent nanoparticles based on AIE fluorogens including polymer nanoparticles and silica nanoparticles over the past few years, and the various biomedical applications based on these fluorescent nanoparticles are also elaborated.

Metasurface external cavity laser

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

Xu, Luyao, E-mail: luyaoxu.ee@ucla.edu; Curwen, Christopher A.; Williams, Benjamin S.

2015-11-30

A vertical-external-cavity surface-emitting-laser is demonstrated in the terahertz range, which is based upon an amplifying metasurface reflector composed of a sub-wavelength array of antenna-coupled quantum-cascade sub-cavities. Lasing is possible when the metasurface reflector is placed into a low-loss external cavity such that the external cavity—not the sub-cavities—determines the beam properties. A near-Gaussian beam of 4.3° × 5.1° divergence is observed and an output power level >5 mW is achieved. The polarized response of the metasurface allows the use of a wire-grid polarizer as an output coupler that is continuously tunable.

Gate-tunable diode-like current rectification and ambipolar transport in multilayer van der Waals ReSe2/WS2 p-n heterojunctions.

PubMed

Wang, Cong; Yang, Shengxue; Xiong, Wenqi; Xia, Congxin; Cai, Hui; Chen, Bin; Wang, Xiaoting; Zhang, Xinzheng; Wei, Zhongming; Tongay, Sefaattin; Li, Jingbo; Liu, Qian

2016-10-12

Vertically stacked van der Waals (vdW) heterojunctions of two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted a great deal of attention due to their fascinating properties. In this work, we report two important gate-tunable phenomena in new artificial vdW p-n heterojunctions created by vertically stacking p-type multilayer ReSe 2 and n-type multilayer WS 2 : (1) well-defined strong gate-tunable diode-like current rectification across the p-n interface is observed, and the tunability of the electronic processes is attributed to the tunneling-assisted interlayer recombination induced by majority carriers across the vdW interface; (2) the distinct ambipolar behavior under gate voltage modulation both at forward and reverse bias voltages is found in the vdW ReSe 2 /WS 2 heterojunction transistors and a corresponding transport model is proposed for the tunable polarity behaviors. The findings may provide some new opportunities for building nanoscale electronic and optoelectronic devices.

μ-Rainbow: CdSe Nanocrystal Photoluminescence Gradients via Laser Spike Annealing for Kinetic Investigations and Tunable Device Design.

PubMed

Treml, Benjamin E; Jacobs, Alan G; Bell, Robert T; Thompson, Michael O; Hanrath, Tobias

2016-02-10

Much of the promise of nanomaterials derives from their size-dependent, and hence tunable, properties. Impressive advances have been made in the synthesis of nanoscale building blocks with precisely tailored size, shape and composition. Significant attention is now turning toward creating thin film structures in which size-dependent properties can be spatially programmed with high fidelity. Nonequilibrium processing techniques present exciting opportunities to create nanostructured thin films with unprecedented spatial control over their optical and electronic properties. Here, we demonstrate single scan laser spike annealing (ssLSA) on CdSe nanocrystal (NC) thin films as an experimental test bed to illustrate how the size-dependent photoluminescence (PL) emission can be tuned throughout the visible range and in spatially defined profiles during a single annealing step. Through control of the annealing temperature and time, we discovered that NC fusion is a kinetically limited process with a constant activation energy in over 2 orders of magnitude of NC growth rate. To underscore the broader technological implications of this work, we demonstrate the scalability of LSA to process large area NC films with periodically modulated PL emission, resulting in tunable emission properties of a large area film. New insights into the processing-structure-property relationships presented here offer significant advances in our fundamental understanding of kinetics of nanomaterials as well as technological implications for the production of nanomaterial films.

The second evolution of ionic liquids: from solvents and separations to advanced materials--energetic examples from the ionic liquid cookbook.

PubMed

Smiglak, Marcin; Metlen, Andreas; Rogers, Robin D

2007-11-01

In this Account of the small portion of the recent research in ionic liquids (ILs) by the Rogers Group, we fast forward through the first evolution of IL research, where ILs were studied for their unique set of physical properties and the resulting potential for tunable "green solvents", to the second evolution of ILs, where the tunability of the cation and anion independently offers almost unlimited access to targeted combinations of physical and chemical properties. This approach is demonstrated here with the field of energetic ionic liquids (EILs), which utilizes this design flexibility to find safe synthetic routes to ILs with high energy content and targeted physical properties.

Supramolecular biomaterials

NASA Astrophysics Data System (ADS)

Webber, Matthew J.; Appel, Eric A.; Meijer, E. W.; Langer, Robert

2016-01-01

Polymers, ceramics and metals have historically dominated the application of materials in medicine. Yet rationally designed materials that exploit specific, directional, tunable and reversible non-covalent interactions offer unprecedented advantages: they enable modular and generalizable platforms with tunable mechanical, chemical and biological properties. Indeed, the reversible nature of supramolecular interactions gives rise to biomaterials that can sense and respond to physiological cues, or that mimic the structural and functional aspects of biological signalling. In this Review, we discuss the properties of several supramolecular biomaterials, as well as their applications in drug delivery, tissue engineering, regenerative medicine and immunology. We envision that supramolecular biomaterials will contribute to the development of new therapies that combine highly functional materials with unmatched patient- and application-specific tailoring of both material and biological properties.

Electrodeposition on nanofibrous polymer scaffolds: Rapid mineralization, tunable calcium phosphate composition and topography

PubMed Central

He, Chuanglong; Xiao, Guiyong; Jin, Xiaobing; Sun, Chenghui; Ma, Peter X.

2011-01-01

We developed a straightforward, fast, and versatile technique to fabricate mineralized nanofibrous polymer scaffolds for bone regeneration in this work. Nanofibrous poly(l-lactic acid) scaffolds were fabricated using both electrospinning and phase separation techniques. An electrodeposition process was designed to deposit calcium phosphate on the nanofibrous scaffolds. Such scaffolds contain a high quality mineral coating on the fiber surface with tunable surface topography and chemical composition by varying the processing parameters, which can mimic the composition and structure of natural bone extracellular matrix and provide a more biocompatible interface for bone regeneration. PMID:21673827

Electronically controlled spoof localized surface plasmons on the corrugated ring with a shorting pin

NASA Astrophysics Data System (ADS)

Zhang, Chao; Zhou, Yong Jin

2018-07-01

We have demonstrated that spoof localized surface plasmons (LSPs) can be controlled by loading a shorting pin into the corrugated ring resonator in the microwave and terahertz (THz) frequencies. Electronical switchability and tunability of spoof LSPs have been achieved by mounting Schottky barrier diodes and varactor diodes across the slit around the shorting pin in the ground plane. An electronically tunable band-pass filter has been demostrated in the microwave frequencies. Such electronically controlled spoof LSPs devices can find more applications for highly integrated plasmonic circuits in microwave and THz frequencies.

Tunable, superconducting, surface-emitting teraherz source

DOEpatents

Welp, Ulrich [Lisle, IL; Koshelev, Alexei E [Bolingbrook, IL; Gray, Kenneth E [Evanston, IL; Kwok, Wai-Kwong [Evanston, IL; Vlasko-Vlasov, Vitalii [Downers Grove, IL

2009-10-27

A compact, solid-state THz source based on the driven Josephson vortex lattice in a highly anisotropic superconductor such as Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 that allows cw emission at tunable frequency. A second order metallic Bragg grating is used to achieve impedance matching and to induce surface emission of THz-radiation from a Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 sample. Steering of the emitted THz beam is accomplished by tuning the Josephson vortex spacing around the grating period using a superimposed magnetic control field.

Tunable, superconducting, surface-emitting teraherz source

DOEpatents

Welp, Ulrich; Koshelev, Alexei E.; Gray, Kenneth E.; Kwok, Wai-Kwong; Vlasko-Vlasov, Vitalii

2010-05-11

A compact, solid-state THz source based on the driven Josephson vortex lattice in a highly anisotropic superconductor such as Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 that allows cw emission at tunable frequency. A second order metallic Bragg grating is used to achieve impedance matching and to induce surface emission of THz-radiation from a Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 sample. Steering of the emitted THz beam is accomplished by tuning the Josephson vortex spacing around the grating period using a superimposed magnetic control field.

Meta-structure and tunable optical device including the same

DOEpatents

Han, Seunghoon; Papadakis, Georgia Theano; Atwater, Harry

2017-12-26

A meta-structure and a tunable optical device including the same are provided. The meta-structure includes a plurality of metal layers spaced apart from one another, an active layer spaced apart from the plurality of metal layers and having a carrier concentration that is tuned according to an electric signal applied to the active layer and the plurality of metal layers, and a plurality of dielectric layers spaced apart from one another and each having one surface contacting a metal layer among the plurality of metal layers and another surface contacting the active layer.

Robust and Elastic Polymer Membranes with Tunable Properties for Gas Separation

DOE PAGES

Cao, Peng -Fei; Li, Bingrui; Hong, Tao; ...

2017-07-17

Here, polymer membranes with the capability to process a massive volume of gas are especially attractive for practical applications of gas separation. Although much effort has been devoted to develop novel polymer membranes with increased selectivity, the overall gas-separation performance and lifetime of membrane are still negatively affected by the weak mechanical performance, low plasticization resistance and poor physical aging tolerance. Recently, elastic polymer membranes with tunable mechanical properties have been attracting significant attentions due to their tremendous potential applications. Herein, we report a series of urethanerich PDMS-based polymer networks (U-PDMS-NW) with improved mechanical performance for gas separation. The cross-linkmore » density of U-PDMS-NWs is tailored by varying the molecular weight ( M n) of PDMS. The U-PDMS-NWs show up to 400% elongation and tunable Young’s modulus (1.3–122.2 MPa), ultimate tensile strength (1.1–14.3 MPa), and toughness (0.7–24.9 MJ/m 3). All of the U-PDMS-NWs exhibit salient gas-separation performance with excellent thermal resistance and aging tolerance, high gas permeability (>100 Barrer), and tunable gas selectivity (up to α[ P CO2/ P N2] ≈ 41 and α[ P CO2/ P CH4] ≈ 16). With well-controlled mechanical properties and gas-separation performance, these U-PDMS-NW can be used as a polymermembrane platform not only for gas separation but also for other applications such as microfluidic channels and stretchable electronic devices.« less

Dielectric properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) ceramics.

PubMed

Xu, Yebin; Liu, Ting; He, Yanyan; Yuan, Xiao

2009-11-01

Ba(0.6)Sr(0.4)TiO(3)-La(B(0.5)Ti(0.5))O(3) (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg(0.5)Ti(0.5))O(3) and 10 to 50 mol% La(Zn(0.5)Ti(0.5))O(3). With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba(0.6)Sr(0.4)TiO(3)-La(Mg(0.5)Ti(0.5))O(3) has better dielectric properties than Ba(0.6)Sr(0.4)TiO(3)-La(Zn(0.5)Ti(0.5))O(3). 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1La(Mg(0.5)Ti(0.5))O(3) has a dielectric constant epsilon = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba(0.6)Sr(0.4)TiO(3)- 0.5La(Mg(0.5)Ti(0.5))O(3) reached 9367 GHz, but the tunable properties were lost.

Tunable conductivity in mesoporous germanium

NASA Astrophysics Data System (ADS)

Beattie, Meghan N.; Bioud, Youcef A.; Hobson, David G.; Boucherif, Abderraouf; Valdivia, Christopher E.; Drouin, Dominique; Arès, Richard; Hinzer, Karin

2018-05-01

Germanium-based nanostructures have attracted increasing attention due to favourable electrical and optical properties, which are tunable on the nanoscale. High densities of germanium nanocrystals are synthesized via electrochemical etching, making porous germanium an appealing nanostructured material for a variety of applications. In this work, we have demonstrated highly tunable electrical conductivity in mesoporous germanium layers by conducting a systematic study varying crystallite size using thermal annealing, with experimental conductivities ranging from 0.6 to 33 (×10‑3) Ω‑1 cm‑1. The conductivity of as-prepared mesoporous germanium with 70% porosity and crystallite size between 4 and 10 nm is shown to be ∼0.9 × 10‑3 Ω‑1 cm‑1, 5 orders of magnitude smaller than that of bulk p-type germanium. Thermal annealing for 10 min at 400 °C further reduced the conductivity; however, annealing at 450 °C caused a morphological transformation from columnar crystallites to interconnecting granular crystallites and an increase in conductivity by two orders of magnitude relative to as-prepared mesoporous germanium caused by reduced influence of surface states. We developed an electrostatic model relating the carrier concentration and mobility of p-type mesoporous germanium to the nanoscale morphology. Correlation within an order of magnitude was found between modelled and experimental conductivities, limited by variation in sample uniformity and uncertainty in void size and fraction after annealing. Furthermore, theoretical results suggest that mesoporous germanium conductivity could be tuned over four orders of magnitude, leading to optimized hybrid devices.

A liquid thermal gradient refractive index lens and using it to trap single living cell in flowing environments.

PubMed

Liu, H L; Shi, Y; Liang, L; Li, L; Guo, S S; Yin, L; Yang, Y

2017-03-29

A gradient refractive index (GRIN) lens has a great potential for on-chip imaging and detection systems because of its flat surface with reduced defects. This paper reports a liquid thermal GRIN lens prepared using heat conduction between only one liquid, and uses it as a tunable optical tweezer for single living cell trapping in a flowing environment. This liquid GRIN lens consists of a trapezoidal region in the upper layer which is used to establish a GRIN profile by the heat conduction between three streams of benzyl alcohol with different temperatures, and subsequently a rhombus region in the lower layer with compensation liquids to form a steady square-law parabolic refractive index profile only in transverse direction. Simulations and experiments successfully show the real-time tunability of the focusing properties. The focal length can be modulated in the range of 500 μm with the minimum focal length of 430 μm. A considerable high enhancement factor achieves 5.4 whereas the full width at half maximum is 4 μm. The response time of the GRIN lens is about 20 ms. Based on this enhancement, tunable optical trapping for single human embryonic kidney 293 cell in the range of 280 μm is demonstrated by varying the focal length and working distance which is difficult for solid optical tweezers. The considerable quality of this liquid GRIN lens indicates on-chip applications especially in high quality optical imaging, detection and cells' handling.

Interlayer Coupling and Gate-Tunable Excitons in Transition Metal Dichalcogenide Heterostructures

DOE PAGES

Gao, Shiyuan; Yang, Li; Spataru, Catalin Dan

2017-11-22

Bilayer van der Waals (vdW) heterostructures such as MoS 2/WS 2 and MoSe 2/WSe 2 have attracted much attention recently, particularly because of their type II band alignments and the formation of interlayer exciton as the lowest-energy excitonic state. In this work, we calculate the electronic and optical properties of such heterostructures with the first-principles GW+Bethe–Salpeter Equation (BSE) method and reveal the important role of interlayer coupling in deciding the excited-state properties, including the band alignment and excitonic properties. Our calculation shows that due to the interlayer coupling, the low energy excitons can be widely tuned by a vertical gatemore » field. In particular, the dipole oscillator strength and radiative lifetime of the lowest energy exciton in these bilayer heterostructures is varied by over an order of magnitude within a practical external gate field. We also build a simple model that captures the essential physics behind this tunability and allows the extension of the ab initio results to a large range of electric fields. In conclusion, our work clarifies the physical picture of interlayer excitons in bilayer vdW heterostructures and predicts a wide range of gate-tunable excited-state properties of 2D optoelectronic devices.« less

Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry.

PubMed

Ryder, Christopher R; Wood, Joshua D; Wells, Spencer A; Yang, Yang; Jariwala, Deep; Marks, Tobin J; Schatz, George C; Hersam, Mark C

2016-06-01

Functionalization of atomically thin nanomaterials enables the tailoring of their chemical, optical and electronic properties. Exfoliated black phosphorus (BP)-a layered two-dimensional semiconductor-exhibits favourable charge-carrier mobility, tunable bandgap and highly anisotropic properties, but it is chemically reactive and degrades rapidly in ambient conditions. Here we show that covalent aryl diazonium functionalization suppresses the chemical degradation of exfoliated BP even after three weeks of ambient exposure. This chemical modification scheme spontaneously forms phosphorus-carbon bonds, has a reaction rate sensitive to the aryl diazonium substituent and alters the electronic properties of exfoliated BP, ultimately yielding a strong, tunable p-type doping that simultaneously improves the field-effect transistor mobility and on/off current ratio. This chemical functionalization pathway controllably modifies the properties of exfoliated BP, and thus improves its prospects for nanoelectronic applications.

Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry

NASA Astrophysics Data System (ADS)

Ryder, Christopher R.; Wood, Joshua D.; Wells, Spencer A.; Yang, Yang; Jariwala, Deep; Marks, Tobin J.; Schatz, George C.; Hersam, Mark C.

2016-06-01

Functionalization of atomically thin nanomaterials enables the tailoring of their chemical, optical and electronic properties. Exfoliated black phosphorus (BP)—a layered two-dimensional semiconductor—exhibits favourable charge-carrier mobility, tunable bandgap and highly anisotropic properties, but it is chemically reactive and degrades rapidly in ambient conditions. Here we show that covalent aryl diazonium functionalization suppresses the chemical degradation of exfoliated BP even after three weeks of ambient exposure. This chemical modification scheme spontaneously forms phosphorus-carbon bonds, has a reaction rate sensitive to the aryl diazonium substituent and alters the electronic properties of exfoliated BP, ultimately yielding a strong, tunable p-type doping that simultaneously improves the field-effect transistor mobility and on/off current ratio. This chemical functionalization pathway controllably modifies the properties of exfoliated BP, and thus improves its prospects for nanoelectronic applications.

The Role of Water in Mediating Interfacial Adhesion and Shear Strength in Graphene Oxide.

PubMed

Soler-Crespo, Rafael A; Gao, Wei; Mao, Lily; Nguyen, Hoang T; Roenbeck, Michael R; Paci, Jeffrey T; Huang, Jiaxing; Nguyen, SonBinh T; Espinosa, Horacio D

2018-06-12

Graphene oxide (GO), whose highly tunable surface chemistry enables the formation of strong interfacial hydrogen-bond networks, has garnered increasing interest in the design of devices that operate in the presence of water. For instance, previous studies have suggested that controlling GO's surface chemistry leads to enhancements in interfacial shear strength, allowing engineers to manage deformation pathways and control failure mechanisms. However, these previous reports have not explored the role of ambient humidity and only offer extensive chemical modifications to GO's surface as the main pathway to control GO's interfacial properties. Herein, through atomic force microscopy experiments on GO-GO interfaces, the adhesion energy and interfacial shear strength of GO were measured as a function of ambient humidity. Experimental evidence shows that adhesion energy and interfacial shear strength can be improved by a factor of 2-3 when GO is exposed to moderate (∼30% water weight) water content. Furthermore, complementary molecular dynamics simulations uncovered the mechanisms by which these nanomaterial interfaces achieve their properties. They reveal that the strengthening mechanism arises from the formation of strongly interacting hydrogen-bond networks, driven by the chemistry of the GO basal plane and intercalated water molecules between two GO surfaces. In summary, the methodology and findings here reported provide pathways to simultaneously optimize GO's interfacial and in-plane mechanical properties, by tailoring the chemistry of GO and accounting for water content, in engineering applications such as sensors, filtration membranes, wearable electronics, and structural materials.

Amine-Modulated/Engineered Interfaces of NiMo Electrocatalysts for Improved Hydrogen Evolution Reaction in Alkaline Solutions.

PubMed

Gao, Wei; Gou, Wangyan; Zhou, Xuemei; Ho, Johnny C; Ma, Yuanyuan; Qu, Yongquan

2018-01-17

The interface between electrolytes and electrocatalysts would largely determine their corresponding activity and stability. Herein, modulating the surface characteristics of NiMo nanoparticles by various adsorbed amines gives the tunability on their interfacial properties and subsequently improves their catalytic performance for hydrogen evolution reaction (HER) in alkaline solutions. Diamines can significantly improve their HER activity by decreasing the charge-transfer resistance and modulating the electronic structures of interfacial active sites. Importantly, among various amines, ethylenediamine facilitates the HER activity of NiMo with a remarkable decrease of 268 mV in the overpotential to reach 10 mA cm -2 as compared with that of the unmodified NiMo in 1.0 M KOH. This method provides a novel strategy of regulating the interfacial properties to strengthen the catalytic performance of electrocatalysts.

Plasmonic Nanobubbles as Transient Vapor Nanobubbles Generated Around Plasmonic Nanoparticles

PubMed Central

Lukianova-Hleb, Ekaterina; Hu, Ying; Latterini, Loredana; Tarpani, Luigi; Lee, Seunghyun; Drezek, Rebekah A.; Hafner, Jason H.; Lapotko, Dmitri O.

2010-01-01

We have used short laser pulses to generate transient vapor nanobubbles around plasmonic nanoparticles. The photothermal, mechanical and optical properties of such bubbles were found to be different from those of plasmonic nanoparticle and vapor bubbles as well. This phenomena was considered as a new complex nanosystem – plasmonic nanobubble (PNB). Mechanical and optical scattering properties of PNB depended upon the nanoparticle surface and heat capacity, clusterization state, and the optical pulse length. The generation of the PNB required much higher laser pulse fluence thresholds than the explosive boiling level, and was characterized by the relatively high lower threshold of the minimal size (lifetime) of PNB. Optical scattering by PNB and its diameter (measured as the lifetime) has been varied with the fluence of laser pulse and this has demonstrated the tunable nature of PNB. PMID:20307085

Advances in tunable diode laser technology

NASA Technical Reports Server (NTRS)

Lo, W.

1980-01-01

The improvement of long-term reliability, the purification of mode properties, and the achievement of higher-temperature operation were examined. In reliability studies a slow increase in contact resistance during room temperature storage for lasers fabricated with In-Au or In-Pt contacts was observed. This increase is actually caused by the diffusion of In into the surface layer of laser crystals. By using a three layered structure of In-Au-Pt or In-Pt-Au, this mode of degradation was reduced. In characterizing the mode properties, it was found that the lasers emit in a highly localized, filamentary manner. For widestripe lasers the emission occurs near the corners of the junction. In order to achieve single-mode operation, stripe widths on the order of 8-10 micrometers are needed. Also, it was found that room temperature electroluminescence is possible near 4.6 micrometers.

Noble metal nanostructures for double plasmon resonance with tunable properties

NASA Astrophysics Data System (ADS)

Petr, M.; Kylián, O.; Kuzminova, A.; Kratochvíl, J.; Khalakhan, I.; Hanuš, J.; Biederman, H.

2017-02-01

We report and compare two vacuum-based strategies to produce Ag/Au materials characterized by double plasmon resonance peaks: magnetron sputtering and method based on the use of gas aggregation sources (GAS) of nanoparticles. It was observed that the double plasmon resonance peaks may be achieved by both of these methods and that the intensities of individual localized surface plasmon resonance peaks may be tuned by deposition conditions. However, in the case of sputter deposition it was necessary to introduce a separation dielectric interlayer in between individual Ag and Au nanoparticle films which was not the case of films prepared by GAS systems. The differences in the optical properties of sputter deposited bimetallic Ag/Au films and coatings consisted of individual Ag and Au nanoparticles produced by GAS is ascribed to the divers mechanisms of nanoparticles formation.

Tunable natural nano-arrays: controlling surface properties and light reflectance

NASA Astrophysics Data System (ADS)

Watson, Jolanta A.; Myhra, Sverre; Watson, Gregory S.

2006-01-01

The general principles of optical design based on the theories of reflection, refraction and diffraction have been rigorously developed and optimized over the last three centuries. Of increasing importance has been the ability to predict and devise new optical technologies designed for specific functions. A key design feature of many of today's optical materials is the control of reflection and light transmittance through the medium. A sudden transition or impedance mismatch from one optical medium to another can result in unwanted reflections from the surface plane. Modification of a surface by creation of a gradual change in refractive index over a significant portion of a wavelength range will result in a reduction in reflection. An alternative surface modification to the multi layered stack coating (gradient index coating) is to produce a surface with structures having a period and height shorter than the light wavelength. These structures act like a pseudo-gradient index coating and can be described by the effective medium theory. Bernhard and Miller some forty years ago were the first to observe such structures found on the surface of insects. These were found in the form of hexagonally close packed nanometre sized protrusions on the corneal surface of certain moths. In this study we report on similar structures which we have found on certain species of cicada wings demonstrating that the reflective/transmission properties of these natural nano-structures can be tuned by controlled removal of the structure height using Atomic Force Microscopy (AFM).

Facile synthesis of biphasic calcium phosphate microspheres with engineered surface topography for controlled delivery of drugs and proteins.

PubMed

Zarkesh, Ibrahim; Ghanian, Mohammad Hossein; Azami, Mahmoud; Bagheri, Fatemeh; Baharvand, Hossein; Mohammadi, Javad; Eslaminejad, Mohamadreza Baghaban

2017-09-01

Biphasic calcium phosphate (BCP) microspheres are of great interest due to their high stability and osteoinductive properties at specific compositions. However, the need for optimal performance at a unique composition limits their flexibility for tuning drug release by modulation of bulk properties and presents the question of engineering surface topography as an alternative. It is necessary to have a facile method to control surface topography at a defined bulk composition. Here, we have produced BCP microspheres with different surface topographies that have the capability to be used as tunable drug release systems. We synthesized calcium deficient hydroxyapatite (CDHA) microparticles by precipitating calcium and phosphate ions onto ethylenediaminetetraacetic acid (EDTA) templates. The morphology and surface topography of CDHA microparticles were controlled using process parameters, which governed nucleation and growth. These parameters included template concentration, heat rate, and stirring speed. Under low heat rate and static conditions, we could obtain spherical microparticles with long and short nanosheets on their surfaces at low and high EDTA concentrations, respectively. These nanostructured microspheres were subsequently crystallized by thermal treatment to produce EDTA-free BCP microspheres with intact morphology. These biocompatible BCP microspheres were highly effective in loading and prolonged release of both small molecule [dexamethasone (Dex)] and protein [bovine serum albumin (BSA)] models. This strategy has enabled us to control the surface topography of BCP microspheres at defined compositions and holds tremendous promise for drug delivery and tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultralight anisotropic foams from layered aligned carbon nanotube sheets

NASA Astrophysics Data System (ADS)

Faraji, Shaghayegh; L. Stano, Kelly; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D.

2015-10-01

In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03899e

High on/off ratios in bilayer graphene field effect transistors realized by surface dopants.

PubMed

Szafranek, B N; Schall, D; Otto, M; Neumaier, D; Kurz, H

2011-07-13

The unique property of bilayer graphene to show a band gap tunable by external electrical fields enables a variety of different device concepts with novel functionalities for electronic, optoelectronic, and sensor applications. So far the operation of bilayer graphene-based field effect transistors requires two individual gates to vary the channel's conductance and to create a band gap. In this paper, we report on a method to increase the on/off ratio in single gated bilayer graphene field effect transistors by adsorbate doping. The adsorbate dopants on the upper side of the graphene establish a displacement field perpendicular to the graphene surface breaking the inversion symmetry of the two graphene layers. Low-temperature measurements indicate that the increased on/off ratio is caused by the opening of a mobility gap.

Computationally Probing the Performance of Hybrid, Heterogeneous, and Homogeneous Iridium-Based Catalysts for Water Oxidation

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

García-Melchor, Max; Vilella, Laia; López, Núria

2016-04-29

An attractive strategy to improve the performance of water oxidation catalysts would be to anchor a homogeneous molecular catalyst on a heterogeneous solid surface to create a hybrid catalyst. The idea of this combined system is to take advantage of the individual properties of each of the two catalyst components. We use Density Functional Theory to determine the stability and activity of a model hybrid water oxidation catalyst consisting of a dimeric Ir complex attached on the IrO 2(110) surface through two oxygen atoms. We find that homogeneous catalysts can be bound to its matrix oxide without losing significant activity.more » Hence, designing hybrid systems that benefit from both the high tunability of activity of homogeneous catalysts and the stability of heterogeneous systems seems feasible.« less

The influence of size and charge of chitosan/polyglutamic acid hollow spheres on cellular internalization, viability and blood compatibility.

PubMed

Dash, Biraja C; Réthoré, Gildas; Monaghan, Michael; Fitzgerald, Kathleen; Gallagher, William; Pandit, Abhay

2010-11-01

Polymeric hollow spheres can be tailored as efficient carriers of various therapeutic molecules due to their tunable properties. However, the entry of these synthetic vehicles into cells, their cell viability and blood compatibility depend on their physical and chemical properties e.g. size, surface charge. Herein, we report the effect of size and surface charge on cell viability and cellular internalization behaviour and their effect on various blood components using chitosan/polyglutamic acid hollow spheres as a model system. Negatively charged chitosan/polyglutamic acid hollow spheres of various sizes 100, 300, 500 and 1000 nm were fabricated using a template based method and covalently surface modified using linear polyethylene glycol and methoxyethanol amine to create a gradient of surface charge from negative to neutrally charged spheres respectively. The results here suggest that both size and surface charge have a significant influence on the sphere's behaviour, most prominently on haemolysis, platelet activation, plasma recalcification time, cell viability and internalization over time. Additionally, cellular internalization behaviour and viability was found to vary with different cell types. These results are in agreement with those of inorganic spheres and liposomes, and can serve as guidelines for tailoring polymeric solid spheres for specific desired applications in biological and pharmaceutical fields, including the design of nanometer to submicron-sized delivery vehicles. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Thermally-induced softening of PNIPAm-based nanopillar arrays.

PubMed

Sanz, Belén; von Bilderling, Catalina; Tuninetti, Jimena S; Pietrasanta, Lía; Mijangos, Carmen; Longo, Gabriel S; Azzaroni, Omar; Giussi, Juan M

2017-03-29

The surface properties of soft nanostructured hydrogels are crucial in the design of responsive materials that can be used as platforms to create adaptive devices. The lower critical solution temperature (LCST) of thermo-responsive hydrogels such as poly(N-isopropylacrylamide) (PNIPAm) can be modified by introducing a hydrophilic monomer to create a wide range of thermo-responsive micro-/nano-structures in a large temperature range. Using surface initiation atom-transfer radical polymerization in synthesized anodized aluminum oxide templates, we designed, fabricated, and characterized thermo-responsive nanopillars based on PNIPAm hydrogels with tunable mechanical properties by incorporating acrylamide monomers (AAm). In addition to their LCST, the incorporation of a hydrophilic entity in the nanopillars based on PNIPAm has abruptly changed the topological and mechanical properties of our system. To gain an insight into the mechanical properties of the nanostructure, its hydrophilic/hydrophobic behavior and topological characteristics, atomic force microscopy, molecular dynamics simulations and water contact angle studies were combined. When changing the nanopillar composition, a significant and opposite variation was observed in their mechanical properties. As temperature increased above the LCST, the stiffness of PNIPAm nanopillars, as expected, did so too, in contrast to the stiffness of PNIPAm-AAm nanopillars that decreased significantly. The molecular dynamics simulations proposed a local molecular rearrangement in our nanosystems at the LCST. The local aggregation of NIPAm segments near the center of the nanopillars displaced the hydrophilic AAm units towards the surface of the structure leading to contact with the aqueous environment. This behavior was confirmed via contact angle measurements below and above the LCST.

Effects of applied electric field during postannealing on the tunable properties of (Ba,Sr)TiO3 thin films

NASA Astrophysics Data System (ADS)

Xia, Yidong; Cheng, Jinbo; Pan, Bai; Wu, Di; Meng, Xiangkang; Liu, Zhiguo

2005-08-01

The impact of postannealing in electric field on the structure, tunability, and dielectric behavior of rf magnetron sputtering derived (Ba,Sr)TiO3 films has been studied. It has been demonstrated that postannealing in the proper electric field can increase the dielectric constant and the tunability remarkably and destroy the symmetry of capacitance-voltage characteristics of the films. The increased out-of-plane lattice constant and the appearance of the hysteresis loops in the electric-annealed films indicated the formation of small polar regions with tetragonal structure, which are responsible for the increased dielectric constant and tunability. It was proposed that the segregation of Ti3+ ions caused by electric annealing could induce the formation of BaTiO3-like regions, which are ferroelectric at room temperature.

Graphene transport mediated by micropatterned substrates

NASA Astrophysics Data System (ADS)

Hinnefeld, J. Henry; Gill, Stephen T.; Mason, Nadya

2018-04-01

Engineered substrates offer a promising avenue towards graphene devices having tunable properties. In particular, topographically patterned substrates can expose unique behavior due to their ability to induce local variations in strain and electrostatic doping. However, to explore the range of possible science and applications, it is important to create topographic substrates that both have tunable features and are suitable for transport measurements. In this letter, we describe the fabrication of tunable, topographically patterned substrates suitable for transport measurements. We report both optical and transport measurements of graphene devices fabricated on these substrates and demonstrate the characteristic strain and local doping behavior induced by the topographic features.

Graphene based terahertz phase modulators

NASA Astrophysics Data System (ADS)

Kakenov, N.; Ergoktas, M. S.; Balci, O.; Kocabas, C.

2018-07-01

Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of π and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.

Shape-Controllable Gold Nanoparticle-MoS2 Hybrids Prepared by Tuning Edge-Active Sites and Surface Structures of MoS2 via Temporally Shaped Femtosecond Pulses.

PubMed

Zuo, Pei; Jiang, Lan; Li, Xin; Li, Bo; Xu, Yongda; Shi, Xuesong; Ran, Peng; Ma, Tianbao; Li, Dawei; Qu, Liangti; Lu, Yongfeng; Grigoropoulos, Costas P

2017-03-01

Edge-active site control of MoS 2 is crucial for applications such as chemical catalysis, synthesis of functional composites, and biochemical sensing. This work presents a novel nonthermal method to simultaneously tune surface chemical (edge-active sites) and physical (surface periodic micro/nano structures) properties of MoS 2 using temporally shaped femtosecond pulses, through which shape-controlled gold nanoparticles are in situ and self-assembly grown on MoS 2 surfaces to form Au-MoS 2 hybrids. The edge-active sites with unbound sulfurs of laser-treated MoS 2 drive the reduction of gold nanoparticles, while the surface periodic structures of laser-treated MoS 2 assist the shape-controllable growth of gold nanoparticles. The proposed novel method highlights the broad application potential of MoS 2 ; for example, these Au-MoS 2 hybrids exhibit tunable and highly sensitive SERS activity with an enhancement factor up to 1.2 × 10 7 , indicating the marked potential of MoS 2 in future chemical and biological sensing applications.

Tunable optical properties of plasmonic Au/Al2O3 nanocomposite thin films analyzed by spectroscopic ellipsometry accounting surface characteristics.

PubMed

Jaiswal, Jyoti; Mourya, Satyendra; Malik, Gaurav; Chandra, Ramesh

2018-05-01

In the present work, we have fabricated plasmonic gold/alumina nanocomposite (Au/Al 2 O 3 NC) thin films on a glass substrate at room temperature by RF magnetron co-sputtering. The influence of the film thickness (∼10-40  nm) on the optical and other physical properties of the samples was investigated and correlated with the structural and compositional properties. The X-ray diffractometer measurement revealed the formation of Au nanoparticles with average crystallite size (5-9.2 nm) embedded in an amorphous Al 2 O 3 matrix. The energy-dispersive X ray and X-ray photoelectron spectroscopy results confirmed the formation of Au/Al 2 O 3 NC quantitatively and qualitatively and it was observed that atomic% of Au increased by increasing thickness. The optical constants of the plasmonic Au/Al 2 O 3 NC thin films were examined by variable angle spectroscopic ellipsometry in the wide spectral range of 246-1688 nm, accounting the surface characteristics in the optical stack model, and the obtained results are expected to be unique. Additionally, a thickness-dependent blueshift (631-590 nm) of surface plasmon resonance peak was observed in the absorption spectra. These findings of the plasmonic Au/Al 2 O 3 NC films may allow the design and fabrication of small, compact, and efficient devices for optoelectronic and photonic applications.

Bio-inspired metal-coordinate hydrogels with programmable viscoelastic material functions controlled by longwave UV light.

PubMed

Grindy, Scott C; Holten-Andersen, Niels

2017-06-07

Control over the viscoelastic mechanical properties of hydrogels intended for use as biomedical materials has long been a goal of soft matter scientists. Recent research has shown that materials made from polymers with reversibly associating transient crosslinks are a promising strategy for controlling viscoelasticity in hydrogels, for example leading to systems with precisely tunable mechanical energy-dissipation. We and others have shown that bio-inspired histidine:transition metal ion complexes allow highly precise and tunable control over the viscoelastic properties of transient network hydrogels. In this paper, we extend the design of these hydrogels such that their viscoelastic properties respond to longwave UV radiation. We show that careful selection of the histidine:transition metal ion crosslink mixtures allows unique control over pre- and post-UV viscoelastic properties. We anticipate that our strategy for controlling stimuli-responsive viscoelastic properties will aid biomedical materials scientists in the development of soft materials with specific stress-relaxing or energy-dissipating properties.

Designer biomaterials for mechanobiology

NASA Astrophysics Data System (ADS)

Li, Linqing; Eyckmans, Jeroen; Chen, Christopher S.

2017-12-01

Biomaterials engineered with specific bioactive ligands, tunable mechanical properties and complex architecture have emerged as powerful tools to probe cell sensing and response to physical properties of their material surroundings, and ultimately provide designer approaches to control cell function.

Multishell Au/Ag/SiO 2 nanorods with tunable optical properties as single particle orientation and rotational tracking probes

DOE PAGES

Chen, Kuangcai; Lin, Chia -Cheng; Vela, Javier; ...

2015-04-07

In this study, three-layer core–shell plasmonic nanorods (Au/Ag/SiO 2–NRs), consisting of a gold nanorod core, a thin silver shell, and a thin silica layer, were synthesized and used as optical imaging probes under a differential interference contrast microscope for single particle orientation and rotational tracking. The localized surface plasmon resonance modes were enhanced upon the addition of the silver shell, and the anisotropic optical properties of gold nanorods were maintained. The silica coating enables surface functionalization with silane coupling agents and provides enhanced stability and biocompatibility. Taking advantage of the longitudinal LSPR enhancement, the orientation and rotational information of themore » hybrid nanorods on synthetic lipid bilayers and on live cell membranes were obtained with millisecond temporal resolution using a scientific complementary metal-oxide-semiconductor camera. The results demonstrate that the as-synthesized hybrid nanorods are promising imaging probes with improved sensitivity and good biocompatibility for single plasmonic particle tracking experiments in biological systems.« less

Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid

NASA Astrophysics Data System (ADS)

Wang, Z.; McKeown Walker, S.; Tamai, A.; Wang, Y.; Ristic, Z.; Bruno, F. Y.; de la Torre, A.; Riccò, S.; Plumb, N. C.; Shi, M.; Hlawenka, P.; Sánchez-Barriga, J.; Varykhalov, A.; Kim, T. K.; Hoesch, M.; King, P. D. C.; Meevasana, W.; Diebold, U.; Mesot, J.; Moritz, B.; Devereaux, T. P.; Radovic, M.; Baumberger, F.

2016-08-01

Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.

X-ray Spectroscopy Uncovering the Effects of Cu Based Nanoparticle Concentration and Structure on Phaseolus vulgaris Germination and Seedling Development.

PubMed

Duran, Nádia M; Savassa, Susilaine M; Lima, Rafael Giovanini de; de Almeida, Eduardo; Linhares, Francisco S; van Gestel, Cornelis A M; Pereira de Carvalho, Hudson W

2017-09-13

Nanoparticles properties such as solubility, tunable surface charges, and singular reactivity might be explored to improve the performance of fertilizers. Nevertheless, these unique properties may also bring risks to the environment since the fate of nanoparticles is poorly understood. This study investigated the impact of a range of CuO nanoparticles sizes and concentrations on the germination and seedling development of Phaseolus vulgaris L. Nanoparticles did not affect seed germination, but seedling weight gain was promoted by 100 mg Cu L -1 and inhibited by 1 000 mg Cu L -1 of 25 nm CuO and CuSO 4 . Most of the Cu taken up remained in the seed coat with Cu hotspots in the hilum. X-ray absorption spectroscopy unraveled that most of the Cu remained in its pristine form. The higher surface reactivity of the 25 nm CuO nanoparticles might be responsible for its deleterious effects. The present study therefore highlights the importance of the nanoparticle structure for its physiological impacts.

Influence of hydrothermal synthesis parameters on the properties of hydroxyapatite nanoparticles.

PubMed

Kuśnieruk, Sylwia; Wojnarowicz, Jacek; Chodara, Agnieszka; Chudoba, Tadeusz; Gierlotka, Stanislaw; Lojkowski, Witold

2016-01-01

Hydroxyapatite (HAp) nanoparticles of tunable diameter were obtained by the precipitation method at room temperature and by microwave hydrothermal synthesis (MHS). The following parameters of the obtained nanostructured HAp were determined: pycnometric density, specific surface area, phase purity, lattice parameters, particle size, particle size distribution, water content, and structure. HAp nanoparticle morphology and structure were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction measurements confirmed crystalline HAp was synthesized, which was pure in terms of phase. It was shown that by changing the synthesis parameters, the diameter of HAp nanoparticles could be controlled. The average diameter of the HAp nanoparticles was determined by Scherrer's equation via the Nanopowder XRD Processor Demo web application, which interprets the results of specific surface area and TEM measurements using the dark-field technique. The obtained nanoparticles with average particle diameter ranging from 8-39 nm were characterized by having homogeneous morphology with a needle shape and a narrow particle size distribution. Strong similarities were found when comparing the properties of some types of nanostructured hydroxyapatite with natural occurring apatite found in animal bones and teeth.

Wetting properties of phospholipid dispersion on tunable hydrophobic SiO2-glass plates.

PubMed

Alexandrova, Lidia; Karakashev, Stoyan I; Grigorov, L; Phan, Chi M; Smoukov, Stoyan K

2015-06-01

We study the wetting properties of very small droplets of salty aqueous suspensions of unilamellar liposomes of DMPC (dimyristoylphosphatidylcholine), situated on SiO2-glass surfaces with different levels of hydrophobicity. We evaluated two different measures of hydrophobicity of solid surfaces - receding contact angles and the thickness of wetting films trapped between an air bubble and the solid surface at different levels of hydrophobicity. We established a good correlation between methods which differ significantly in measurement difficulty and experimental setup. We also reveal details of the mechanism of wetting of different surfaces by the DMPC liposome suspension. Hydrophilic surfaces with water contact angles in the range of 0° to 35° are readily hydrophobized by the liposomes and only showed corresponding contact angles in the range 27°-43°. For same range of surface hydrophobicities, there was a clear reduction of the thickness of the wetting films between the surface and a bubble, reaching a minimum in the 35°-40° range. At higher levels of hydrophobicity both pure water and the liposome suspension show similar contact angles, and the thickness of wetting films between a bubble and those surfaces increases in parallel. Our analysis showed that the only force able to stabilize the film under these experimental conditions is steric repulsion. The latter suggests that nanobubbles adsorbed on hydrophobic parts of the surface, and coated with a DMPC layer, may be the cause of the 40-70 nm thickness of wetting films we observe. Copyright © 2014 Elsevier B.V. All rights reserved.

Atomic layer deposition of Al-incorporated Zn(O,S) thin films with tunable electrical properties

NASA Astrophysics Data System (ADS)

Park, Helen Hejin; Jayaraman, Ashwin; Heasley, Rachel; Yang, Chuanxi; Hartle, Lauren; Mankad, Ravin; Haight, Richard; Mitzi, David B.; Gunawan, Oki; Gordon, Roy G.

2014-11-01

Zinc oxysulfide, Zn(O,S), films grown by atomic layer deposition were incorporated with aluminum to adjust the carrier concentration. The electron carrier concentration increased up to one order of magnitude from 1019 to 1020 cm-3 with aluminum incorporation and sulfur content in the range of 0 ≤ S/(Zn+Al) ≤ 0.16. However, the carrier concentration decreased by five orders of magnitude from 1019 to 1014 cm-3 for S/(Zn+Al) = 0.34 and decreased even further when S/(Zn+Al) > 0.34. Such tunable electrical properties are potentially useful for graded buffer layers in thin-film photovoltaic applications.

Design and synthesis of nonionic copolypeptide hydrogels with reversible thermoresponsive and tunable physical properties.

PubMed

Zhang, Shanshan; Alvarez, Daniel J; Sofroniew, Michael V; Deming, Timothy J

2015-04-13

Polypeptide-based formulations that undergo liquid to hydrogel transitions upon change in temperature have become desirable targets since they can be mixed with cells or injected into tissues as liquids, and subsequently transform into rigid scaffolds or depots. Such materials have been challenging to prepare using synthetic polypeptides, especially when reversible gelation and tunable physical properties are desired. Here, we designed and prepared new nonionic diblock copolypeptide hydrogels (DCH) containing hydrophilic poly(γ-[2-(2-methoxyethoxy)ethyl]-rac-glutamate) and hydrophobic poly(l-leucine) segments, named DCHEO, and also further incorporated copolypeptide domains into DCHEO to yield unprecedented thermoresponsive DCH, named DCHT. Although previous attempts to prepare nonionic hydrogels composed solely of synthetic polypeptides have been unsuccessful, our designs yielded materials with highly reversible thermal transitions and tunable properties. Nonionic, thermoresponsive DCHT were found to support the viability of suspended mesenchymal stem cells in vitro and were able to dissolve and provide prolonged release of both hydrophilic and hydrophobic molecules. The versatility of these materials was further demonstrated by the independent molecular tuning of DCHT liquid viscosity at room temperature and DCHT hydrogel stiffness at elevated temperature, as well as the DCHT liquid to hydrogel transition temperature itself.

Tunable photoluminescence and magnetic properties of Dy(3+) and Eu(3+) doped GdVO4 multifunctional phosphors.

PubMed

Liu, Yanxia; Liu, Guixia; Dong, Xiangting; Wang, Jinxian; Yu, Wensheng

2015-10-28

A series of Dy(3+) or/and Eu(3+) doped GdVO4 phosphors were successfully prepared by a simple hydrothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometry (EDS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The results indicate that the as-prepared samples are pure tetragonal phase GdVO4, taking on nanoparticles with an average size of 45 nm. Under ultraviolet (UV) light excitation, the individual Dy(3+) or Eu(3+) ion activated GdVO4 phosphors exhibit excellent emission properties in their respective regions. The mechanism of energy transfer from the VO4(3-) group and the charge transfer band (CTB) to Dy(3+) and Eu(3+) ions is proposed. Color-tunable emissions in GdVO4:Dy(3+),Eu(3+) phosphors are realized through adopting different excitation wavelengths or adjusting the appropriate concentration of Dy(3+) and Eu(3+) when excited by a single excitation wavelength. In addition, the as-prepared samples show paramagnetic properties at room temperature. This kind of multifunctional color-tunable phosphor has great potential applications in the fields of photoelectronic devices and biomedical sciences.

Multichannel tunable filter properties of 1D magnetized ternary plasma photonic crystal in the presence of evanescent wave

NASA Astrophysics Data System (ADS)

Awasthi, Suneet Kumar; Panda, Ranjita; Shiveshwari, Laxmi

2017-07-01

The multichannel tunable filter properties of one-dimensional ternary plasma photonic crystal composed of magnetized plasma and lossless dielectric have been theoretically investigated using transfer matrix method in the microwave region. The proposed filters possess 2N - 2 comb-like sharp resonant peaks also called transmission channels for N > 1 in transmission spectra in the absence and presence of an external magnetic field. Due to the coupling between evanescent waves and propagating modes in plasma and dielectric layers, respectively, 2N - 2 transmission channels are found without the addition of any defect, enabling the structure to work as a multichannel filter. Next, the filter properties can be made tunable by the application of an external magnetic field, i.e., channel frequency can either be red or blue shifted depending upon the orientation of an external magnetic field. The number of channels and their positions can also be modulated by changing the number of periods (N) and the incident angle (θo), respectively, for both transverse electric (TE) and transverse magnetic (TM) modes besides other parameters such as plasma collision frequency, thickness of the plasma layer, plasma frequency, etc.

Parallel microfluidic synthesis of size-tunable polymeric nanoparticles using 3D flow focusing towards in vivo study

PubMed Central

Lim, Jong-Min; Bertrand, Nicolas; Valencia, Pedro M.; Rhee, Minsoung; Langer, Robert; Jon, Sangyong; Farokhzad, Omid C.; Karnik, Rohit

2014-01-01

Microfluidic synthesis of nanoparticles (NPs) can enhance the controllability and reproducibility in physicochemical properties of NPs compared to bulk synthesis methods. However, applications of microfluidic synthesis are typically limited to in vitro studies due to low production rates. Herein, we report the parallelization of NP synthesis by 3D hydrodynamic flow focusing (HFF) using a multilayer microfluidic system to enhance the production rate without losing the advantages of reproducibility, controllability, and robustness. Using parallel 3D HFF, polymeric poly(lactide-co-glycolide)-b-polyethyleneglycol (PLGA-PEG) NPs with sizes tunable in the range of 13–150 nm could be synthesized reproducibly with high production rate. As a proof of concept, we used this system to perform in vivo pharmacokinetic and biodistribution study of small (20 nm diameter) PLGA-PEG NPs that are otherwise difficult to synthesize. Microfluidic parallelization thus enables synthesis of NPs with tunable properties with production rates suitable for both in vitro and in vivo studies. PMID:23969105

Topologically nontrivial electronic bands and tunable Dirac cones in graphynes with spin-orbit coupling

NASA Astrophysics Data System (ADS)

Juricic, Vladimir; van Miert, Guido; Morais Smith, Cristiane

2015-03-01

Graphynes represent an emerging family of carbon allotropes that differ from graphene by the presence of the triple bonds (-C ≡C-) in their band structure. They have recently attracted much interest due to the tunability of the Dirac cones in the band structure. I will show that the spin-orbit coupling in β-graphyne could produce various effects related to the topological properties of its electronic bands. Intrinsic spin-orbit coupling yields high- and tunable Chern-number bands, which may host both topological and Chern insulators, in the presence and absence of time-reversal symmetry, respectively. Furthermore, Rashba spin-orbit coupling can be used to control the position and the number of Dirac cones in the Brillouin zone. Finally, I will also discuss the electronic properties of α - and γ - graphyne in the presence of the spin-orbit coupling within recently developed general theory of spin-orbit couplings in graphynes. Work supported by the Netherlands Organization for Scientific Research (NWO).

An organic dye-polymer (phenol red-poly (vinyl alcohol)) composite architecture towards tunable -optical and -saturable absorption characteristics

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

Sreedhar, Sreeja, E-mail: sreejasreedhar83@gmail.com; Muneera, C. I., E-mail: drcimuneera@hotmail.com; Illyaskutty, Navas

2016-05-21

Herein, we demonstrate that blending an organic dye (guest/filler), with a vinyl polymer (host template), is an inexpensive and simple approach for the fabrication of multifunctional photonic materials which could display an enhancement in the desirable properties of the constituent materials and, at the same time provide novel synergistic properties for the guest-host system. A new guest-host nanocomposite system comprising Phenol Red dye and poly (vinyl alcohol) as guest and host template, respectively, which exhibits tunable optical characteristics and saturable absorption behavior, is introduced. The dependence of local electronic environment provided by the polymer template and the interactions of themore » polymer molecules with the encapsulated guest molecules on the observed optical/nonlinear absorption behavior is discussed. An understanding of the tunability of the optical/ photophysical processes, with respect to the filler content, as discussed herein could help in the design of improved optical materials for several photonic device applications like organic light emitting diodes and saturable absorbers.« less

Fluorescence-tunable Ag-DNA biosensor with tailored cytotoxicity for live-cell applications

NASA Astrophysics Data System (ADS)

Bossert, Nelli; de Bruin, Donny; Götz, Maria; Bouwmeester, Dirk; Heinrich, Doris

2016-11-01

DNA-stabilized silver clusters (Ag-DNA) show excellent promise as a multi-functional nanoagent for molecular investigations in living cells. The unique properties of these fluorescent nanomaterials allow for intracellular optical sensors with tunable cytotoxicity based on simple modifications of the DNA sequences. Three Ag-DNA nanoagent designs are investigated, exhibiting optical responses to the intracellular environments and sensing-capability of ions, functional inside living cells. Their sequence-dependent fluorescence responses inside living cells include (1) a strong splitting of the fluorescence peak for a DNA hairpin construct, (2) an excitation and emission shift of up to 120 nm for a single-stranded DNA construct, and (3) a sequence robust in fluorescence properties. Additionally, the cytotoxicity of these Ag-DNA constructs is tunable, ranging from highly cytotoxic to biocompatible Ag-DNA, independent of their optical sensing capability. Thus, Ag-DNA represents a versatile live-cell nanoagent addressable towards anti-cancer, patient-specific and anti-bacterial applications.

Liquid crystal photonic bandgap fiber components

NASA Astrophysics Data System (ADS)

Scolari, L.; Alkeskjold, T. T.; Noordegraaf, D.; Tartarini, G.; Bassi, P.; Bjarklev, A.

2007-11-01

Liquid crystal photonic bandgap fibers represent a promising platform for the design of all-in-fiber optical devices, which show a high degree of tunability and exhibit novel optical properties for the manipulation of guided light. In this review paper we present tunable fiber devices for spectral filtering, such as Gaussian filters and notch filters, and devices for polarization control and analysis, such as birefringence control devices and switchable and rotatable polarizers.

Photo-crosslinked PDMSstar-PEG Hydrogels: Synthesis, Characterization, and Potential Application for Tissue Engineering Scaffolds

PubMed Central

Hou, Yaping; Schoener, Cody A.; Regan, Katherine R.; Munoz-Pinto, Dany; Hahn, Mariah S.; Grunlan, Melissa A.

2010-01-01

Inorganic-organic hydrogels with tunable chemical and physical properties were prepared from methacrylated star polydimethylsiloxane (PDMSstar-MA) and diacrylated poly(ethylene glycol) (PEG-DA) for use as tissue engineering scaffolds. Eighteen compositionally unique hydrogels were prepared by photo-crosslinking varying weight ratios of PEG-DA and PDMSstar-MA of different molecular weights (Mn): PEG-DA (Mn = 3.4k and 6k g/mol) and PDMSstar-MA (Mn = 1.8k, 5k and 7k g/mol). Introduction of PDMSstar-MA caused formation of discrete PDMS-enriched microparticles dispersed within the PEG matrix. The swelling ratio, mechanical properties in tension and compression, non-specific protein adhesion, controlled introduction of bioactivity and cytotoxicity of hydrogels were studied. This library of inorganic-organic hydrogels with tunable properties provides a useful platform to study the effect of scaffold properties on cell behavior. PMID:20146518

Stretchable nanocomposite electrodes with tunable mechanical properties by supersonic cluster beam implantation in elastomers

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

Borghi, F.; Podestà, A.; Milani, P., E-mail: pmilani@mi.infn.it

We demonstrate the fabrication of gold-polydimethylsiloxane nanocomposite electrodes, by supersonic cluster beam implantation, with tunable Young's modulus depending solely on the amount of metal clusters implanted in the elastomeric matrix. We show both experimentally and by atomistic simulations that the mechanical properties of the nanocomposite can be maintained close to that of the bare elastomer for significant metal volume concentrations. Moreover, the elastic properties of the nanocomposite, as experimentally characterized by nanoindentation and modeled with molecular dynamics simulations, are also well described by the Guth-Gold classical model for nanoparticle-filled rubbers, which depends on the presence, concentration, and aspect ratio ofmore » metal nanoparticles, and not on the physical and chemical modification of the polymeric matrix due to the embedding process. The elastic properties of the nanocomposite can therefore be determined and engineered a priori, by controlling only the nanoparticle concentration.« less

A facile method to prepare "green" nano-phosphors with a large Stokes-shift and solid-state enhanced photophysical properties based on surface-modified gold nanoclusters.

PubMed

Cheng, C H; Huang, H Y; Talite, M J; Chou, W C; Yeh, J M; Yuan, C T

2017-12-15

Colloidal nano-materials, such as quantum dots (QDs) have been applied to light-conversion nano-phosphors due to their unique tunable emission. However, most of the QDs involve toxic elements and are synthesized in a hazardous solvent. In addition, conventional QD nano-phosphors with a small Stokes shift suffered from reabsorption losses and aggregation-induced quenching in the solid state. Here, we demonstrate a facile, matrix-free method to prepare eco-friendly nano-phosphors with a large Stokes shift based on aqueous thiolate-stabilized gold nanoclusters (GSH-AuNCs) with simple surface modifications. Our method is just to drop GSH-AuNCs solution on the aluminum foil and then surface-modified AuNCs (Al-GSH-AuNCs) can be spontaneously precipitated out of the aqueous solution. Compared with pristine GSH-AuNCs in solution, the Al-GSH-AuNCs exhibit enhanced solid-state PL quantum yields, lengthened PL lifetime, and spectral blue shift, which can be attributed to the aggregation-induced emission enhancement facilitated by surface modifications. Such surface-treatment induced aggregation of AuNCs can restrict the surface-ligand motion, leading to the enhancement of PL properties in the solid state. In addition, the Al-GSH-AuNCs nano-phosphors with a large Stokes shift can mitigate the aggregation-induced PL quenching and reabsorption losses, which would be potential candidates for "green" nano-phosphors. Copyright © 2017 Elsevier Inc. All rights reserved.

Controlling the Photophysical Properties of Semiconductor Quantum Dot Arrays by Strategically Altering Their Surface Chemistry

NASA Astrophysics Data System (ADS)

Marshall, Ashley R.

Semiconductor quantum dots (QDs) are interesting materials that, after less than 40 years of research, are used in commercial products. QDs are now found in displays, such as Samsung televisions and the Kindle Fire, and have applications in lighting, bio-imaging, quantum computing, and photovoltaics. They offer a large range of desirable properties: a controllable band gap, solution processability, controlled energy levels, and are currently the best materials for multiple exciton generation. The tunable optoelectronic properties of QDs can be controlled using size, shape, composition, and surface treatments--as shown here. Due to the quasi-spherical shape of QDs the surface to volume ratio is high, i.e. many of the constituent atoms are found on the QD surface. This makes QDs highly sensitive to surface chemistry modifications. This thesis encompasses the effects of surface treatments for QDs of two semiconducting materials: lead chalcogenides and CsPbI3. Our group developed a new synthetic technique for lead chalcogenide QDs via the cation exchange of cadmium chalcogenides. An in-depth chemical analysis is paired with optical and electrical studies and we find that metal halide residue contributes to the oxidative stability and decreased trap state density in cation-exchanged PbS QDs. We exploit these properties to make air-stable QD photovoltaic devices from both PbS and PbSe QD materials. Beyond the effects of residual atoms left from the synthetic technique, I investigated how to controllably add atoms onto the surface of QDs. I found that by introducing metal halides as a post-treatment in an electronically coupled array I am able to control the performance parameters in QD photovoltaic devices. These treatments fully infiltrate the assembled film, even under short exposure times and allow me to add controlled quantities of surface atoms to study their effects on film properties and photovoltaic device performance. Finally, I sought to apply the knowledge of the lead chalcogenide QD surfaces to produce QD photovoltaics from a new material: CsPbI3. I fabricated the first perovskite QD photovoltaic devices and using similar treatment methods as the lead chalcogenide QD arrays, I am able to influence the photophysical properties of CsPbI3 QD arrays.

Deposition of Nanostructured Thin Film from Size-Classified Nanoparticles

NASA Technical Reports Server (NTRS)

Camata, Renato P.; Cunningham, Nicholas C.; Seol, Kwang Soo; Okada, Yoshiki; Takeuchi, Kazuo

2003-01-01

Materials comprising nanometer-sized grains (approximately 1_50 nm) exhibit properties dramatically different from those of their homogeneous and uniform counterparts. These properties vary with size, shape, and composition of nanoscale grains. Thus, nanoparticles may be used as building blocks to engineer tailor-made artificial materials with desired properties, such as non-linear optical absorption, tunable light emission, charge-storage behavior, selective catalytic activity, and countless other characteristics. This bottom-up engineering approach requires exquisite control over nanoparticle size, shape, and composition. We describe the design and characterization of an aerosol system conceived for the deposition of size classified nanoparticles whose performance is consistent with these strict demands. A nanoparticle aerosol is generated by laser ablation and sorted according to size using a differential mobility analyzer. Nanoparticles within a chosen window of sizes (e.g., (8.0 plus or minus 0.6) nm) are deposited electrostatically on a surface forming a film of the desired material. The system allows the assembly and engineering of thin films using size-classified nanoparticles as building blocks.

Structural Properties of Silk Electro-Gels

NASA Astrophysics Data System (ADS)

Tabatabai, A. P.; Urbach, J. S.; Blair, D. L.; Kaplan, D. L.

2013-03-01

The interest in Bombyx Mori silk emerges from its biocompatibility and its structural superiority to synthetic polymers. Our particular interest lies in understanding the capabilities of silk electro-gels because of their reversibility and tunable adhesion. We create an electro-gel by applying a DC electric potential across a reconstituted silk fibroin solution derived directly from Bombyx Mori cocoons. This process leads to the intermolecular self-assembly of fibroin proteins into a weak gel. In this talk we will present our results on the effects of applied shear on electro-gels. We quantify the structural properties while dynamically imaging shear induced fiber formation; known as fibrillogenesis. It is observed that the mechanical properties and microstructure of these materials are highly dependent on shear history. We will also discuss the role of surface modification, through micro-patterning, on the observed gel structure. Our results provide an understanding of both the viscoelastiticity and microstucture of reconstituted silks that are being utilized as tissue scaffolds. This work is supported by a grant from the AFOSR FA9550-07-1-0130.

Combined laser heating and tandem acousto-optical filter for two-dimensional temperature distribution on the surface of the heated microobject

NASA Astrophysics Data System (ADS)

Bykov, A. A.; Kutuza, I. B.; Zinin, P. V.; Machikhin, A. S.; Troyan, I. A.; Bulatov, K. M.; Batshev, V. I.; Mantrova, Y. V.; Gaponov, M. I.; Prakapenka, V. B.; Sharma, S. K.

2018-01-01

Recently it has been shown that it is possible to measure the two-dimensional distribution of the surface temperature of microscopic specimens. The main component of the system is a tandem imaging acousto-optical tunable filter synchronized with a video camera. In this report, we demonstrate that combining the laser heating system with a tandem imaging acousto-optical tunable filter allows measurement of the temperature distribution under laser heating of the platinum plates as well as a visualization of the infrared laser beam, that is widely used for laser heating in diamond anvil cells.

Flexible and tunable terahertz all-dielectric metasurface composed of ceramic spheres embedded in ferroelectric/ elastomer composite.

PubMed

Lan, Chuwen; Zhu, Di; Gao, Jiannan; Li, Bo; Gao, Zehua

2018-04-30

Terahertz (THz) all-dielectric metasurfaces made of high-index and low-loss resonators have attracted more and more attention due to their versatile properties. However, the all-dielectric metasurfaces in THz suffer from limited bandwidth and low tunability. Meanwhile, they are usually fabricated on flat and rigid substrates, and consequently their applications are restricted. Here, a simple approach is proposed and experimentally demonstrated to obtain a flexible and tunable THz all-dielectric metasurface. In this metasurface, micro ceramic spheres (ZrO 2 ) are embedded in a ferroelectric (strontium titanate) / elastomer (polydimethylsiloxane) composite. It is shown that the Mie resonances in micro ceramic spheres can be thermally and reversibly tuned resulting from the temperature dependent permittivity of the ferroelectric / PDMS composite. This metasurface characterized by flexibility and tunability is expected to have a more extensive application in active THz devices.

Tunable Microfluidic Devices for Hydrodynamic Fractionation of Cells and Beads: A Review

PubMed Central

Alvankarian, Jafar; Majlis, Burhanuddin Yeop

2015-01-01

The adjustable microfluidic devices that have been developed for hydrodynamic-based fractionation of beads and cells are important for fast performance tunability through interaction of mechanical properties of particles in fluid flow and mechanically flexible microstructures. In this review, the research works reported on fabrication and testing of the tunable elastomeric microfluidic devices for applications such as separation, filtration, isolation, and trapping of single or bulk of microbeads or cells are discussed. Such microfluidic systems for rapid performance alteration are classified in two groups of bulk deformation of microdevices using external mechanical forces, and local deformation of microstructures using flexible membrane by pneumatic pressure. The main advantage of membrane-based tunable systems has been addressed to be the high capability of integration with other microdevice components. The stretchable devices based on bulk deformation of microstructures have in common advantage of simplicity in design and fabrication process. PMID:26610519

Progress in Cherenkov femtosecond fiber lasers

PubMed Central

Liu, Xiaomin; Svane, Ask S.; Lægsgaard, Jesper; Tu, Haohua; Boppart, Stephen A.; Turchinovich, Dmitry

2016-01-01

We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems – broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted - dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40 % conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100–200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed. PMID:27110037

Design of multi-wavelength tunable filter based on Lithium Niobate

NASA Astrophysics Data System (ADS)

Zhang, Ailing; Yao, Yuan; Zhang, Yue; Song, Hongyun

2018-05-01

A multi-wavelength tunable filter is designed. It consists of multiple waveguides among multiple waveguide gratings. A pair of electrodes were placed on both sides of each waveguide. The tunable filter uses the electro-optic effect of Lithium Niobate to tune the phase caused by each waveguide. Consequently, the wavelength and wavelength spacing of the filter are tuned by changing external voltages added on the electrode pairs. The tunable property of the filter is analyzed by phase matching condition and transfer-matrix method. Numerical results show that not only multiple wavelengths with narrow bandwidth are tuned with nearly equal spacing by synchronously changing the voltages added on all electrode pairs, but also the number of wavelengths is determined by the number of phase shifts caused by electrode pairs. Furthermore, due to the electro-optic effect of Lithium Niobate, the tuning speed of the filter can reach the order of ns.

A spectrally tunable all-graphene-based flexible field-effect light-emitting device

NASA Astrophysics Data System (ADS)

Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

2015-07-01

The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (~450 nm) to red (~750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays.

Progress in Cherenkov femtosecond fiber lasers.

PubMed

Liu, Xiaomin; Svane, Ask S; Lægsgaard, Jesper; Tu, Haohua; Boppart, Stephen A; Turchinovich, Dmitry

2016-01-20

We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems - broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted - dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40 % conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100-200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed.

Tunable terahertz wave-plate based on dual-frequency liquid crystal controlled by alternating electric field.

PubMed

Yu, Jian-Ping; Chen, Sai; Fan, Fei; Cheng, Jie-Rong; Xu, Shi-Tong; Wang, Xiang-Hui; Chang, Sheng-Jiang

2018-01-22

In this work, the optically anisotropic property of dual-frequency liquid crystals (DFLC) in terahertz (THz) regime has been experimentally investigated, which indicates that the refractive index and birefringence of DFLC can be continuously modulated by both the alternating frequency and intensity of the alternating electric field. This tunability originates from the rotation of DFLC molecules induced by alternating electric fields. The results show that by modulating the alternating frequency from 1 kHz to 100 kHz under 30 kV/m electric field, the 600 μm thickness DFLC cell can play as a tunable quarter-wave plate above 0.68 THz, or a half-wave plate above 1.33 THz. Besides, it can be viewed as a tunable THz phase shifter from 0 to π. Therefore, due to its novel tuning mechanism, DFLC will be of great significance in dynamic manipulating on THz phase and polarization.

Tunable Absorption System based on magnetorheological elastomers and Halbach array: design and testing

NASA Astrophysics Data System (ADS)

Bocian, Mirosław; Kaleta, Jerzy; Lewandowski, Daniel; Przybylski, Michał

2017-08-01

In this paper, the systematic design, construction and testing of a Tunable Absorption System (TAS) incorporating magnetorheological elastomer (MRE) has been investigated. The TAS has been designed for energy absorption and mitigation of vibratory motions from an impact excitation. The main advantage of the designed TAS is that it has the ability to change and adapt to working conditions. Tunability can be realised through a change in the magnetic field caused by the change of an internal arrangement of permanent magnets within a double dipolar circular Halbach array. To show the capabilities of the tested system, experiments based on an impulse excitation have been performed. Significant changes of the TASs natural frequency and damping characteristics have been obtained. By incorporating magnetic tunability within the TAS a significant qualitative and quantitative change in the devices mechanical properties and performance were obtained.

Nano-optomechanical characterization of surface-plasmon-based tunable filter integrated with comb-drive actuator

NASA Astrophysics Data System (ADS)

Honma, H.; Mitsudome, M.; Ishida, M.; Sawada, K.; Takahashi, K.

2017-03-01

We report a tunable plasmonic color filter consisting of a metamaterial periodic grating and microelectromechanical systems (MEMS) actuator. An aluminum subwavelength grating is integrated with electrostatic comb-drive actuators to expand the metal subwavelength period, which allows continuous control of the excitation wavelength of surface plasmons (SPs). We develop a batch fabrication process by employing a liftoff technique using an electron beam resist altered by the electron dose depending on different aspect ratios (length/width) for various components such as the subwavelength grating, nanohinge flexural suspensions, and comb fingers. We successfully demonstrate a continuous shift in the excitation wavelength over the 514-635 nm range by nanopitch expansion. The design margin of the grating period for SP excitation is evaluated by comparing the experimental pitch variation and theoretically calculated values. The resonance frequency of the tunable filter is optically measured to be approximately 10 kHz. The optically and mechanically obtained values agree well with the theory of electrostatic actuation and finite-difference time-domain simulation.

Hierarchically Porous Graphitic Carbon with Simultaneously High Surface Area and Colossal Pore Volume Engineered via Ice Templating

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

Estevez, Luis; Prabhakaran, Venkateshkumar; Garcia, Adam L.

Developing hierarchical porous carbon (HPC) materials with competing textural characteristics such as surface area and pore volume in one material is difficult to accomplish—particulalry for an atomically ordered (graphitic) carbon. Herein we describe a synthesis strategy to engineer tunable hierarchically porous carbon (HPC) materials across micro- meso- and macroporous length scales, allowing the fabrication of a graphitic HPC with both very high surface area (> 2500 m2/g) and pore volume (>10 cm3/g), the combination of which has not been seen previously. The mesopore volume alone for these materials is up to 7.91 cm3/g, the highest ever reported. The unique materialmore » was explored for use as a supercapaictor electrode and for oil adsorption; two applications that require textural properties that are typicaly exclusive to one another. This design scheme for HPCs can be utilized in broad applications, including electrochemical systems such as batteries and supercapacitors, sorbents, and catalyst supports.« less

Anomalous Z2 antiferromagnetic topological phase in pressurized SmB6

NASA Astrophysics Data System (ADS)

Chang, Kai-Wei; Chen, Peng-Jen

2018-05-01

Antiferromagnetic materials, whose time-reversal symmetry is broken, can be classified into the Z2 topology if they respect some specific symmetry. Since the theoretical proposal, however, no materials have been found to host such Z2 antiferromagnetic topological (Z2-AFT ) phase to date. Here we demonstrate that the topological Kondo insulator SmB6 can be a Z2-AFT system when pressurized to undergo an antiferromagnetic phase transition. In addition to proposing the possible candidate for a Z2-AFT material, in this work we also illustrate the anomalous topological surface states of the Z2-AFT phase which have not been discussed before. Originating from the interplay between the topological properties and the antiferromagnetic surface magnetization, the topological surface states of the Z2-AFT phase behave differently as compared with those of a topological insulator. Besides, the Z2-AFT insulators are also found promising in the generation of tunable spin currents, which is an important application in spintronics.

Optical properties of single infrared resonant circular microcavities for surface phonon polaritons.

PubMed

Wang, Tao; Li, Peining; Hauer, Benedikt; Chigrin, Dmitry N; Taubner, Thomas

2013-11-13

Plasmonic antennas are crucial components for nano-optics and have been extensively used to enhance sensing, spectroscopy, light emission, photodetection, and others. Recently, there is a trend to search for new plasmonic materials with low intrinsic loss at new plasmon frequencies. As an alternative to metals, polar crystals have a negative real part of permittivity in the Reststrahlen band and support surface phonon polaritons (SPhPs) with weak damping. Here, we experimentally demonstrate the resonance of single circular microcavities in a thin gold film deposited on a silicon carbide (SiC) substrate in the mid-infrared range. Specifically, the negative permittivity of SiC leads to a well-defined, size-tunable SPhP resonance with a Q factor of around 60 which is much higher than those in surface plasmon polariton (SPP) resonators with similar structures. These infrared resonant microcavities provide new possibilities for widespread applications such as enhanced spectroscopy, sensing, coherent thermal emission, and infrared photodetectors among others throughout the infrared frequency range.

Reversed oxygen sensing using colloidal quantum wells towards highly emissive photoresponsive varnishes

PubMed Central

Lorenzon, Monica; Christodoulou, Sotirios; Vaccaro, Gianfranco; Pedrini, Jacopo; Meinardi, Francesco; Moreels, Iwan; Brovelli, Sergio

2015-01-01

Colloidal quantum wells combine the advantages of size-tunable electronic properties with vast reactive surfaces that could allow one to realize highly emissive luminescent-sensing varnishes capable of detecting chemical agents through their reversible emission response, with great potential impact on life sciences, environmental monitoring, defence and aerospace engineering. Here we combine spectroelectrochemical measurements and spectroscopic studies in a controlled atmosphere to demonstrate the ‘reversed oxygen-sensing’ capability of CdSe colloidal quantum wells, that is, the exposure to oxygen reversibly increases their luminescence efficiency. Spectroelectrochemical experiments allow us to directly relate the sensing response to the occupancy of surface states. Magneto-optical measurements demonstrate that, under vacuum, heterostructured CdSe/CdS colloidal quantum wells stabilize in their negative trion state. The high starting emission efficiency provides a possible means to enhance the oxygen sensitivity by partially de-passivating the particle surfaces, thereby enhancing the density of unsaturated sites with a minimal cost in term of luminescence losses. PMID:25910499

Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

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

Liu, Shenggang, E-mail: liusg@uestc.edu.cn; Hu, Min; Chen, Xiaoxing

2014-05-19

Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The radiation intensity generated with this method is 400 times stronger than that from SPPs at a conventional dielectric or semiconducting surface and is comparable to that from the most advanced photonics source such as a quantum cascade laser. The physical mechanism for this strongmore » radiation is presented. The phase diagrams defining the parameters range for the occurrence of radiation is also shown.« less

Room-temperature processing of CdSe quantum dots with tunable sizes

NASA Astrophysics Data System (ADS)

Joo, So-Yeong; Jeong, Da-Woon; Lee, Chan-Gi; Kim, Bum-Sung; Park, Hyun-Su; Kim, Woo-Byoung

2017-06-01

In this work, CdSe quantum dots (QDs) with tunable sizes have been fabricated via photo-induced chemical etching at room temperature, and the related reaction mechanism was investigated. The surface of QDs was oxidized by the holes generated through photon irradiation of oxygen species, and the obtained oxide layer was dissolved in an aqueous solution of 3-amino-1-propanol (APOL) with an APOL:H2O volume ratio of 5:1. The generated electrons promoted QD surface interactions with amino groups, which ultimately passivated surface defects. The absorption and photoluminescence emission peaks of the produced QDs were clearly blue-shifted about 26 nm with increasing time, and the resulting quantum yield for an 8 h etched sample was increased from 20% to 26%, as compared to the initial sample.

Tunable bi-functional photonic device based on one-dimensional photonic crystal infiltrated with a bistable liquid-crystal layer.

PubMed

Wu, Chong-Yin; Zou, Yi-Hong; Timofeev, Ivan; Lin, Yu-Ting; Zyryanov, Victor Ya; Hsu, Jy-Shan; Lee, Wei

2011-04-11

We investigated the optical properties of a one-dimensional photonic crystal infiltrated with a bistable chiral tilted homeotropic nematic liquid crystal as the central defect layer. By modulating the nematic director orientation with applied voltage, the electrical tunability of the defect modes was observed in the transmission spectrum. The composite not only is a general tunable device but also involves the green concept in that it can operate in two stable states at 0 V. Under the parallel-polarizer scheme, the spectral characteristics suggest a potential application for this device as an energy-efficient multichannel optical switch. © 2011 Optical Society of America

Electronic and thermally tunable infrared metamaterial absorbers

NASA Astrophysics Data System (ADS)

Shrekenhamer, David; Miragliotta, Joseph A.; Brinkley, Matthew; Fan, Kebin; Peng, Fenglin; Montoya, John A.; Gauza, Sebastian; Wu, Shin-Tson; Padilla, Willie J.

2016-09-01

In this paper, we report a computational and experimental study using tunable infrared (IR) metamaterial absorbers (MMAs) to demonstrate frequency tunable (7%) and amplitude modulation (61%) designs. The dynamic tuning of each structure was achieved through the addition of an active material—liquid crystals (LC) or vanadium dioxide (VO2)-within the unit cell of the MMA architecture. In both systems, an applied stimulus (electric field or temperature) induced a dielectric change in the active material and subsequent variation in the absorption and reflection properties of the MMA in the mid- to long-wavelength region of the IR (MWIR and LWIR, respectively). These changes were observed to be reversible for both systems and dynamic in the LC-based structure.

Silk-elastin-like protein biomaterials for the controlled delivery of therapeutics.

PubMed

Huang, Wenwen; Rollett, Alexandra; Kaplan, David L

2015-05-01

Genetically engineered biomaterials are useful for controlled delivery owing to their rational design, tunable structure-function, biocompatibility, degradability and target specificity. Silk-elastin-like proteins (SELPs), a family of genetically engineered recombinant protein polymers, possess these properties. Additionally, given the benefits of combining semi-crystalline silk-blocks and elastomeric elastin-blocks, SELPs possess multi-stimuli-responsive properties and tunability, thereby becoming promising candidates for targeted cancer therapeutics delivery and controlled gene release. An overview of SELP biomaterials for drug delivery and gene release is provided. Biosynthetic strategies used for SELP production, fundamental physicochemical properties and self-assembly mechanisms are discussed. The review focuses on sequence-structure-function relationships, stimuli-responsive features and current and potential drug delivery applications. The tunable material properties allow SELPs to be pursued as promising biomaterials for nanocarriers and injectable drug release systems. Current applications of SELPs have focused on thermally-triggered biomaterial formats for the delivery of therapeutics, based on local hyperthermia in tumors or infections. Other prominent controlled release applications of SELPs as injectable hydrogels for gene release have also been pursued. Further biomedical applications that utilize other stimuli to trigger the reversible material responses of SELPs for targeted delivery, including pH, ionic strength, redox, enzymatic stimuli and electric field, are in progress. Exploiting these additional stimuli-responsive features will provide a broader range of functional biomaterials for controlled therapeutics release and tissue regeneration.

Electrically tunable metasurface based on Mie-type dielectric resonators.

PubMed

Su, Zhaoxian; Zhao, Qian; Song, Kun; Zhao, Xiaopeng; Yin, Jianbo

2017-02-21

In this paper, we have designed a metasurface based on electrically tunable Mie-type resonators and theoretically demonstrated its tunable response to electromagnetic waves with varying frequency. The metasurface consists of disk-like ferroelectric resonators arrayed on a metal film and the upper surface of resonators is covered by ion gel film which is transparent for incident electromagnetic wave. Using the metal film and ion gel film as electrodes, the permittivity of the resonators can be adjusted by an external electric field and, as a result, the reflection phase of the resonators can be dynamically adjusted in a relatively wide range. By programmable controlling the electric field strength applied on resonators of metasurface, a 2π phase ramp can be realized and, thereby, the arbitrary reflection behavior of incident waves with varied frequency is obtained. Because of the tunability, this metasurface can also be used to design adaptive metasurface lens and carpet cloak.

Micro-optofluidic Lenses: A review

PubMed Central

Nguyen, Nam-Trung

2010-01-01

This review presents a systematic perspective on the development of micro-optofluidic lenses. The progress on the development of micro-optofluidic lenses are illustrated by example from recent literature. The advantage of micro-optofluidic lenses over solid lens systems is their tunability without the use of large actuators such as servo motors. Depending on the relative orientation of light path and the substrate surface, micro-optofluidic lenses can be categorized as in-plane or out-of-plane lenses. However, this review will focus on the tunability of the lenses and categorizes them according to the concept of tunability. Micro-optofluidic lenses can be either tuned by the liquid in use or by the shape of the lens. Micro-optofluidic lenses with tunable shape are categorized according to the actuation schemes. Typical parameters of micro-optofluidic lenses reported recently are compared and discussed. Finally, perspectives are given for future works in this field. PMID:20714369

Electrically tunable metasurface based on Mie-type dielectric resonators

PubMed Central

Su, Zhaoxian; Zhao, Qian; Song, Kun; Zhao, Xiaopeng; Yin, Jianbo

2017-01-01

In this paper, we have designed a metasurface based on electrically tunable Mie-type resonators and theoretically demonstrated its tunable response to electromagnetic waves with varying frequency. The metasurface consists of disk-like ferroelectric resonators arrayed on a metal film and the upper surface of resonators is covered by ion gel film which is transparent for incident electromagnetic wave. Using the metal film and ion gel film as electrodes, the permittivity of the resonators can be adjusted by an external electric field and, as a result, the reflection phase of the resonators can be dynamically adjusted in a relatively wide range. By programmable controlling the electric field strength applied on resonators of metasurface, a 2π phase ramp can be realized and, thereby, the arbitrary reflection behavior of incident waves with varied frequency is obtained. Because of the tunability, this metasurface can also be used to design adaptive metasurface lens and carpet cloak. PMID:28220861

Electrically tunable metasurface based on Mie-type dielectric resonators

NASA Astrophysics Data System (ADS)

Su, Zhaoxian; Zhao, Qian; Song, Kun; Zhao, Xiaopeng; Yin, Jianbo

2017-02-01

In this paper, we have designed a metasurface based on electrically tunable Mie-type resonators and theoretically demonstrated its tunable response to electromagnetic waves with varying frequency. The metasurface consists of disk-like ferroelectric resonators arrayed on a metal film and the upper surface of resonators is covered by ion gel film which is transparent for incident electromagnetic wave. Using the metal film and ion gel film as electrodes, the permittivity of the resonators can be adjusted by an external electric field and, as a result, the reflection phase of the resonators can be dynamically adjusted in a relatively wide range. By programmable controlling the electric field strength applied on resonators of metasurface, a 2π phase ramp can be realized and, thereby, the arbitrary reflection behavior of incident waves with varied frequency is obtained. Because of the tunability, this metasurface can also be used to design adaptive metasurface lens and carpet cloak.

Prominent blue emission through Tb3+ doped La2O3 nano-phosphors for white LEDs

NASA Astrophysics Data System (ADS)

Jain, Neha; Singh, Rajan Kr; Srivastava, Amit; Mishra, S. K.; Singh, Jai

2018-06-01

In this article, we report the tunable luminescence emission of Tb3+ doped La2O3 nanophosphors synthesized by a facile and effective Polyol method. The structural and surface morphological studies have been carried out by employing X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD studies elucidate the proper phase formation and the results emanate from Raman spectroscopy of the as synthesized nanophosphor affirms it. The optical properties of the as fabricated nanoparticles have been investigated by Raman and photoluminescence (PL) spectroscopy. The PL spectroscopy shows the occurrence of excitation peaks at 305, 350 and 375 nm for 543 nm emissions, correspond to transition 5D4 →7F5. Emission spectra with 305 nm excitation exhibits characteristic emission peaks of Tb3+ion at 472, 487, 543 and 580 nm. The intensity of emission increases with Tb3+ concentration and is most prominent for 7 at% Tb3+ ion. The characteristic emissions of Tb3+ ion owes to the transition in which intensities of blue and green emission are prominent. The dominant intensity has been found for 472 nm (for blue emission). Commission international d 'Eclairage (CIE) co-ordinates have found in the light blue to green region. The research work provides a new interesting insight dealing with tunable properties with Tb3+ doping in La2O3 nanophosphors, to be useful for display devices, solar cells, LEDs and optoelectronic devices.

Moth eye-inspired anti-reflective surfaces for improved IR optical systems & visible LEDs fabricated with colloidal lithography and etching.

PubMed

Chan, Lesley W; Morse, Daniel E; Gordon, Michael J

2018-05-08

Near- and sub-wavelength photonic structures are used by numerous organisms (e.g. insects, cephalopods, fish, birds) to create vivid and often dynamically-tunable colors, as well as create, manipulate, or capture light for vision, communication, crypsis, photosynthesis, and defense. This review introduces the physics of moth eye (ME)-like, biomimetic nanostructures and discusses their application to reduce optical losses and improve efficiency of various optoelectronic devices, including photodetectors, photovoltaics, imagers, and light emitting diodes. Light-matter interactions at structured and heterogeneous surfaces over different length scales are discussed, as are the various methods used to create ME-inspired surfaces. Special interest is placed on a simple, scalable, and tunable method, namely colloidal lithography with plasma dry etching, to fabricate ME-inspired nanostructures in a vast suite of materials. Anti-reflective surfaces and coatings for IR devices and enhancing light extraction from visible light emitting diodes are highlighted.

Effect of CaRuO3 interlayer on the dielectric properties of Ba(Zr ,Ti)O3 thin films prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Tang, X. G.; Tian, H. Y.; Wang, J.; Wong, K. H.; Chan, H. L. W.

2006-10-01

Ba(Zr0.2Ti0.8)O3 (BZT) thin films on Pt(111)/Ti /SiO2/Si(100) substrates without and with CaRuO3 (CRO) buffer layer were fabricated at 650°C in situ by pulsed laser deposition. The BZT thin films showed a dense morphology, many clusters are found on the surface images of BZT/Pt films, which are composed by nanosized grains of 25-35nm; the average grain size of BZT/CRO films is about 80nm, which lager than that of BZT/Pt thin film. The dielectric constants and dissipation factors of BZT/Pt and BZT/CRO thin films were 392 and 0.019 and 479 and 0.021 at 1MHz, respectively. The dielectric constant of BZT/Pt and BZT/CRO thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of ˜70% and 37 and 75% and 36, respectively, under an applied field of 400kV /cm. The possible microstructural background responsible for the high dielectric constant and tunability was discussed.

Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

PubMed Central

Jung, Han Sae; Tsai, Hsin-Zon; Wong, Dillon; Germany, Chad; Kahn, Salman; Kim, Youngkyou; Aikawa, Andrew S.; Desai, Dhruv K.; Rodgers, Griffin F.; Bradley, Aaron J.; Velasco, Jairo; Watanabe, Kenji; Taniguchi, Takashi; Wang, Feng; Zettl, Alex; Crommie, Michael F.

2015-01-01

Owing to its relativistic low-energy charge carriers, the interaction between graphene and various impurities leads to a wealth of new physics and degrees of freedom to control electronic devices. In particular, the behavior of graphene’s charge carriers in response to potentials from charged Coulomb impurities is predicted to differ significantly from that of most materials. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) can provide detailed information on both the spatial and energy dependence of graphene's electronic structure in the presence of a charged impurity. The design of a hybrid impurity-graphene device, fabricated using controlled deposition of impurities onto a back-gated graphene surface, has enabled several novel methods for controllably tuning graphene’s electronic properties.1-8 Electrostatic gating enables control of the charge carrier density in graphene and the ability to reversibly tune the charge2 and/or molecular5 states of an impurity. This paper outlines the process of fabricating a gate-tunable graphene device decorated with individual Coulomb impurities for combined STM/STS studies.2-5 These studies provide valuable insights into the underlying physics, as well as signposts for designing hybrid graphene devices. PMID:26273961

Color-tunable up-conversion emission in Y2O3:Yb3+, Er3+ nanoparticles prepared by polymer complex solution method

PubMed Central

2013-01-01

Abstract Powders of Y2O3 co-doped with Yb3+ and Er3+ composed of well-crystallized nanoparticles (30 to 50 nm in diameter) with no adsorbed ligand species on their surface are prepared by polymer complex solution method. These powders exhibit up-conversion emission upon 978-nm excitation with a color that can be tuned from green to red by changing the Yb3+/Er3+ concentration ratio. The mechanism underlying up-conversion color changes is presented along with material structural and optical properties. PACS 42.70.-a, 78.55.Hx, 78.60.-b PMID:23522083

Molecular Assembly of Polysaccharide-Based Microcapsules and Their Biomedical Applications.

PubMed

Feng, Xiyun; Du, Cuiling; Li, Junbai

2016-08-01

Advanced multifunctional microcapsules have revealed great potential in biomedical applications owing to their tunable size, shape, surface properties, and stimuli responsiveness. Polysaccharides are one of the most acceptable biomaterials for biomedical applications because of their outstanding virtues such as biocompatibility, biodegradability, and low toxicity. Many efforts have been devoted to investigating novel molecular design and efficient building blocks for polysaccharide-based microcapsules. In this Personal Account, we first summarize the common features of polysaccharides and the main principles of the design and fabrication of polysaccharide-based microcapsules, and further discuss their applications in biomedical areas and perspectives for future research. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of mesoscale, crumpled, reduced graphene oxide roses by water-in-oil emulsion approach

NASA Astrophysics Data System (ADS)

Sharma, Shruti; Pham, Viet H.; Boscoboinik, Jorge A.; Camino, Fernando; Dickerson, James H.; Tannenbaum, Rina

2018-05-01

Mesoscale crumpled graphene oxide roses (GO roses) were synthesized by using colloidal graphene oxide (GO) variants as precursors for a hybrid emulsification-rapid evaporation approach. This process produced rose-like, spherical, reduced mesostructures of colloidal GO sheets, with corrugated surfaces and particle sizes tunable in the range of ∼800 nm to 15 μm. Excellent reproducibility for particle size distribution is shown for each selected speed of homogenizer rotor among different sample batches. The morphology and chemical structure of these produced GO roses was investigated using electron microscopy and spectroscopy techniques. The proposed synthesis route provides control over particle size, morphology and chemical properties of the synthesized GO roses.

Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics.

PubMed

Ryabchun, Alexander; Kollosche, Matthias; Wegener, Michael; Sakhno, Oksana

2016-12-01

Volume diffraction gratings (VDGs) are inscribed selectively by diffusive introduction of benzophenone and subsequent UV-holographic structuring into an electroactive dielectric elastomer actuator (DEA), to afford a continuous voltage-controlled grating shift of 17%. The internal stress coupling of DEA and optical domain allows for a new generation of true monolithic tunable elastomer optics with voltage controlled properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature.

PubMed

Kim, Myeong-Ho; Lee, Young-Ahn; Kim, Jinseo; Park, Jucheol; Ahn, Seungbae; Jeon, Ki-Joon; Kim, Jeong Won; Choi, Duck-Kyun; Seo, Hyungtak

2015-10-27

The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal-OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm(2) V(-1) sec(-1), the carrier concentration at ∼10(20) cm(-3) without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.

Polysaccharide based nanogels in the drug delivery system: Application as the carrier of pharmaceutical agents.

PubMed

Debele, Tilahun Ayane; Mekuria, Shewaye Lakew; Tsai, Hsieh-Chih

2016-11-01

Polysaccharide-based nanoparticles have fascinated attention as a vesicle of different pharmaceutical agents due to their unique multi-functional groups in addition to their physicochemical properties, including biocompatibility and biodegradability. The existence of multi-functional groups on the polysaccharide backbone permits facile chemical or biochemical modification to synthesize polysaccharide based nanoparticles with miscellaneous structures. Polysaccharide-based nanogels have high water content, large surface area for multivalent bioconjugation, tunable size, and interior network for the incorporation of different pharmaceutical agents. These unique properties offer great potential for the utilization of polysaccharide-based nanogels in the drug delivery systems. Hence, this review describes chemistry of certain common polysaccharides, several methodologies used to synthesize polysaccharide nanoparticles and primarily focused on the polysaccharide (or polysaccharide derivative) based nanogels as the carrier of pharmaceutical agents. Copyright © 2016 Elsevier B.V. All rights reserved.

Theory of high-resolution tunneling spin transport on a magnetic skyrmion

NASA Astrophysics Data System (ADS)

Palotás, Krisztián; Rózsa, Levente; Szunyogh, László

2018-05-01

Tunneling spin transport characteristics of a magnetic skyrmion are described theoretically in magnetic scanning tunneling microscopy (STM). The spin-polarized charge current in STM (SP-STM) and tunneling spin transport vector quantities, the longitudinal spin current and the spin transfer torque, are calculated in high spatial resolution within the same theoretical framework. A connection between the conventional charge current SP-STM image contrasts and the magnitudes of the spin transport vectors is demonstrated that enables the estimation of tunneling spin transport properties based on experimentally measured SP-STM images. A considerable tunability of the spin transport vectors by the involved spin polarizations is also highlighted. These possibilities and the combined theory of tunneling charge and vector spin transport pave the way for gaining deep insight into electric-current-induced tunneling spin transport properties in SP-STM and to the related dynamics of complex magnetic textures at surfaces.

Tunable properties of spin waves in magnetoelastic {NiFe}/{{Gd}}_{2}{({{MoO}}_{4})}_{3} heterostructure

NASA Astrophysics Data System (ADS)

Graczyk, Piotr; Trzaskowska, Aleksandra; Załȩski, Karol; Mróz, Bogusław

2016-07-01

Full ferroelastic and simultaneously ferroelectric materials are interesting candidates for applications in devices based on multiferroic heterostructures. They should allow for non-volatile and low-power writing of data bits in magnetoelectric random access memories. Moreover, ferroelasticity, in contrast to piezoelectric material, make magnetic information in ferromagnetic film resistant to external fields. As an example for such a system, we have studied the magnetoelastic interaction between a thin ferromagnetic layer of {{Ni}}85{{Fe}}15 with a full ferroelastic-ferroelectric gadolinium molybdate {{Gd}}2{({{MoO}}4)}3 crystal. We have investigated the influence of {{Gd}}2{({{MoO}}4)}3 spontaneous strain onto magnetic properties of thin ferromagnetic film. Particularly, we have shown by Brillouin spectroscopy, that it is possible to modulate surface spin wave frequency of {{Ni}}85{{Fe}}15 by spontaneous strain of gadolinium molybdate substrate.

Enhanced cytocompatibility and reduced genotoxicity of polydimethylsiloxane modified by plasma immersion ion implantation.

PubMed

Tong, Liping; Zhou, Wenhua; Zhao, Yuetao; Yu, Xuefeng; Wang, Huaiyu; Chu, Paul K

2016-12-01

Polydimethylsiloxane(PDMS) is a common industrial polymer with advantages such as ease of fabrication, tunable hardness, and other desirable properties, but the basic (-OSi(CH 3 ) 2 -) n structure in PDMS is inherently hydrophobic thereby hampering application to biomedical engineering. In this study, plasma immersion ion implantation (PIII) is conducted on PDMS to improve the biological properties. PIII forms wrinkled "herringbone" patterns and abundant O-containing functional groups on PDMS to alter the surface hydrophilicity. The biocompatibility of the modified PDMS is assessed with Chinese hamster ovarian cells and compared to that of the untreated PDMS. Our results reveal that the PDMS samples after undergoing PIII have better cytocompatibility and lower genotoxicity. PIII which is a non-line-of-sight technique extends the application of PDMS to the biomedical field. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of humidity and solution viscosity on electrospun fiber morphology.

PubMed

Nezarati, Roya M; Eifert, Michelle B; Cosgriff-Hernandez, Elizabeth

2013-10-01

Electrospinning is a popular technique to fabricate tissue engineering scaffolds due to the exceptional tunability of fiber morphology that can be used to control scaffold mechanical properties, degradation rate, and cell behavior. Although the effects of modulating processing or solution parameters on fiber morphology have been extensively studied, there remains limited understanding of the impact of environmental parameters such as humidity. To address this gap, three polymers (poly(ethylene glycol) [PEG], polycaprolactone [PCL], and poly(carbonate urethane) [PCU]) were electrospun at a range of relative humidities (RH = 5%-75%) and the resulting fiber architecture characterized with scanning electron microscopy. Low relative humidity (< 50%) resulted in fiber breakage for all three polymers due to decreased electrostatic discharge from the jet. At high relative humidity (> 50%), three distinct effects were observed based on individual polymer properties. An increase in fiber breakage and loss of fiber morphology occurred in the PEG system as a result of increased water absorption at high relative humidity. In contrast, surface pores on PCL fibers were observed and hypothesized to have formed via vapor-induced phase separation. Finally, decreased PCU fiber collection occurred at high humidity likely due to increased electrostatic discharge. These findings highlight that the effects of relative humidity on electrospun fiber morphology are dependent on polymer hydrophobicity, solvent miscibility with water, and solvent volatility. An additional study was conducted to highlight that small changes in molecular weight can strongly influence solution viscosity and resulting fiber morphology. We propose that solution viscosity rather than concentration is a more useful parameter to report in electrospinning methodology to enable reproduction of findings. In summary, this study further elucidates key mechanisms in electrospun fiber formation that can be utilized to fabricate tissue engineering scaffolds with tunable and reproducible properties.

Effects of Humidity and Solution Viscosity on Electrospun Fiber Morphology

PubMed Central

Nezarati, Roya M.; Eifert, Michelle B.

2013-01-01

Electrospinning is a popular technique to fabricate tissue engineering scaffolds due to the exceptional tunability of fiber morphology that can be used to control scaffold mechanical properties, degradation rate, and cell behavior. Although the effects of modulating processing or solution parameters on fiber morphology have been extensively studied, there remains limited understanding of the impact of environmental parameters such as humidity. To address this gap, three polymers (poly(ethylene glycol) [PEG], polycaprolactone [PCL], and poly(carbonate urethane) [PCU]) were electrospun at a range of relative humidities (RH=5%–75%) and the resulting fiber architecture characterized with scanning electron microscopy. Low relative humidity (<50%) resulted in fiber breakage for all three polymers due to decreased electrostatic discharge from the jet. At high relative humidity (>50%), three distinct effects were observed based on individual polymer properties. An increase in fiber breakage and loss of fiber morphology occurred in the PEG system as a result of increased water absorption at high relative humidity. In contrast, surface pores on PCL fibers were observed and hypothesized to have formed via vapor-induced phase separation. Finally, decreased PCU fiber collection occurred at high humidity likely due to increased electrostatic discharge. These findings highlight that the effects of relative humidity on electrospun fiber morphology are dependent on polymer hydrophobicity, solvent miscibility with water, and solvent volatility. An additional study was conducted to highlight that small changes in molecular weight can strongly influence solution viscosity and resulting fiber morphology. We propose that solution viscosity rather than concentration is a more useful parameter to report in electrospinning methodology to enable reproduction of findings. In summary, this study further elucidates key mechanisms in electrospun fiber formation that can be utilized to fabricate tissue engineering scaffolds with tunable and reproducible properties. PMID:23469941

Bioresorbable polypeptide-based comb-polymers efficiently improves the stability and pharmacokinetics of proteins in vivo.

PubMed

Turabee, Md Hasan; Thambi, Thavasyappan; Lym, Jae Seung; Lee, Doo Sung

2017-03-28

Stimuli-responsive polypeptides are a promising class of biomaterials due to their tunable physicochemical and biological properties. Herein, a series of novel pH- and thermo-responsive block copolymers based on polypeptides were synthesized by ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride in the presence of poly(ethylene glycol)-diamine macroinitiator followed by aminolysis. The resulting polypeptide-based triblock copolymer, poly[(2-(dibutylamino)ethyl-l-glutamate)-co-(γ-benzyl-l-glutamate)]-poly(ethylene glycol)-b-poly[(2-(dibutylamino)ethyl-l-glutamate)-co-(γ-benzyl-l-glutamate)] (PNLG-co-PBLG-b-PEG-b-PBLG-co-PNLG), exists as a low viscous sol at low pH and temperature (≤pH 6.4, 25 °C) but it transforms to a soft gel under physiological conditions (pH 7.4 and 37 °C). The physical properties of the polypeptide gel can be tuned by controlling the ratio between hydrophobic PBLG and pH-sensitive PNLG blocks. The polypeptide-based copolymer did not show any noticeable cytotoxicity to fibroblast cells in vitro. It was found that subcutaneous injection of the polypeptide copolymer solution into the dorsal region of Sprague-Dawley (SD) rats formed a gel instantly without major inflammation. The gels were completely biodegraded in six weeks and found to be bioresorbable. Human growth hormone (hGH)-loaded polypeptide-based biodegradable copolymer sols readily formed a viscoelastic gel that inhibited an initial burst and prolonged the hGH release for one week. Overall, due to their bioresorbable and sustained release protein characteristics, polypeptide hydrogels may serve as viable platforms for therapeutic protein delivery and the surface tunable properties of polypeptide hydrogels can be exploited for other potential therapeutic proteins.

Synthesis of layer-tunable graphene: A combined kinetic implantation and thermal ejection approach

DOE PAGES

Wang, Gang; Zhang, Miao; Liu, Su; ...

2015-05-04

Layer-tunable graphene has attracted broad interest for its potentials in nanoelectronics applications. However, synthesis of layer-tunable graphene by using traditional chemical vapor deposition (CVD) method still remains a great challenge due to the complex experimental parameters and the carbon precipitation process. Herein, by performing ion implantation into a Ni/Cu bilayer substrate, the number of graphene layers, especially single or double layer, can be controlled precisely by adjusting the carbon ion implant fluence. The growth mechanism of the layer-tunable graphene is revealed by monitoring the growth process is observed that the entire implanted carbon atoms can be expelled towards the substratemore » surface and thus graphene with designed layer number can be obtained. Such a growth mechanism is further confirmed by theoretical calculations. The proposed approach for the synthesis of layer-tunable graphene offers more flexibility in the experimental conditions. Being a core technology in microelectronics processing, ion implantation can be readily implemented in production lines and is expected to expedite the application of graphene to nanoelectronics.« less

One-step, simple, and green synthesis of tin dioxide/graphene nanocomposites and their application to lithium-ion battery anodes

NASA Astrophysics Data System (ADS)

Jiang, Zaixing; Zhang, Dongjie; Li, Yue; Cheng, Hao; Wang, Mingqiang; Wang, Xueqin; Bai, Yongping; Lv, Haibao; Yao, Yongtao; Shao, Lu; Huang, Yudong

2014-10-01

Graphene with extraordinary thermal, mechanical and electrical properties offers possibilities in a variety of applications. Recent advances in the synthesis of graphene composites using supercritical fluids are highlighted. Supercritical fluids exhibit unique features for the synthesis of composites due to its low viscosity, high diffusivity, near-zero surface tension, and tunability. Here, we report the preparation of tin dioxide (SnO2)/graphene nanocomposite through supercritical CO2 method. It demonstrates that the SnO2 nanoparticles are homogeneously dispersed on the surface of graphene sheets with a particle size of 2.3-2.6 nm. The SnO2/graphene nanocomposites exhibit higher lithium storage capacity and better cycling performance compared to that of the similar CNT nanocomposites. The reported synthetic procedure is straightforward, green and inexpensive. And it may be readily adopted to produce large quantities of graphene based nanocomposites.

Sub-50-nm self-assembled nanotextures for enhanced broadband antireflection in silicon solar cells.

PubMed

Rahman, Atikur; Ashraf, Ahsan; Xin, Huolin; Tong, Xiao; Sutter, Peter; Eisaman, Matthew D; Black, Charles T

2015-01-21

Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light-emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nm enhance the broadband antireflection compared with that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well-modelled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self-assembly for precise and tunable nanotexture design in the range of ~10-70 nm across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significantly betters the performance gain compared with an optimized, planar antireflection coating.

Electrophoretic co-deposition of cellulose nanocrystals-45S5 bioactive glass nanocomposite coatings on stainless steel

NASA Astrophysics Data System (ADS)

Chen, Qiang; Yang, Yuyun; Pérez de Larraya, Uxua; Garmendia, Nere; Virtanen, Sannakaisa; Boccaccini, Aldo R.

2016-01-01

An organic-inorganic nanocomposite coating consisting of fibrous cellulose nanocrystals and 45S5 bioactive glass, intended as a bioactive surface for bone implants, was developed by a one-step electrophoretic deposition. The composition, surface roughness and wettability of the deposited coatings, influenced by the concentration of each component in the suspension, were controllable as a result of the simplicity of the coating technique. Bioactive glass particles were individually wrapped with porous cellulose layers, forming a porous coating with uniform thickness. Bioactivity test in simulated body fluid revealed a rapid hydroxyapatite formation on the deposited nanocomposite coating. Furthermore, electrochemical test was carried out to understand the corrosion behavior of the deposited coatings during incubation in simulated body fluid. According to the results of this study, the obtained cellulose-bioactive glass coatings with tunable properties represent a promising approach for biofunctionalization of metallic orthopedic implants.

Asymmetric mass acquisition in LaBi. Topological semimetal candidate

DOE PAGES

Wu, Yun; Kong, Tai; Wang, Lin-Lin; ...

2016-08-18

We use our high resolution He-lamp-based, tunable laser-based angle-resolved photoemission spectroscopy measurements and density functional theory calculations to study the electronic properties of LaBi, a binary system that was proposed to be a member of a new family of topological semimetals. Both bulk and surface bands are present in the spectra. Furthermore, the dispersion of the surface state is highly unusual. It resembles a Dirac cone, but upon closer inspection we can clearly detect an energy gap. The bottom band follows roughly a parabolic dispersion. The dispersion of the top band remains very linear, “V” -shape like, with the tipmore » approaching very closely to the extrapolated location of Dirac point. Finally, such asymmetric mass acquisition is highly unusual and opens a possibility of a new topological phenomenon that has yet to be understood.« less

Bio-inspired reversible underwater adhesive.

PubMed

Zhao, Yanhua; Wu, Yang; Wang, Liang; Zhang, Manman; Chen, Xuan; Liu, Minjie; Fan, Jun; Liu, Junqiu; Zhou, Feng; Wang, Zuankai

2017-12-20

The design of smart surfaces with switchable adhesive properties in a wet environment has remained a challenge in adhesion science and materials engineering. Despite intense demands in various industrial applications and exciting progress in mimicking the remarkable wet adhesion through the delicate control of catechol chemistry, polyelectrolyte complex, and supramolecular architectures, the full recapitulation of nature's dynamic function is limited. Here, we show a facile approach to synthesize bioinspired adhesive, which entails the reversible, tunable, and fast regulation of the wet adhesion on diverse surfaces. The smart wet adhesive takes advantage of the host-guest molecular interaction and the adhesive nature of catechol chemistry, as well as the responsive polymer, allowing for screening and activation of the interfacial interaction simply by a local temperature trigger in an on-demand manner. Our work opens up an avenue for the rational design of bioinspired adhesives with performances even beyond nature.

Targeted Drug Delivery Based on Gold Nanoparticle Derivatives.

PubMed

Gholipourmalekabadi, Mazaher; Mobaraki, Mohammadmahdi; Ghaffari, Maryam; Zarebkohan, Amir; Omrani, Vahid Fallah; Urbanska, Aleksandra M; Seifalian, Alexander

2017-01-01

Drug delivery systems are effective and attractive methods which allow therapeutic substances to be introduced into the body more effectively and safe by having tunable delivery rate and release target site. Gold nanoparticles (AuNPs) have a myriad of favorable physical, chemical, optical, thermal and biological properties that make them highly suitable candidates as non-toxic carriers for drug and gene delivery. The surface modifications of AuNPs profoundly improve their circulation, minimize aggregation rates, enhance attachment to therapeutic molecules and target agents due to their nano range size which further increases their ability to cross cell membranes and reduce overall cytotoxicity. This comprehensive article reviews the applications of the AuNPs in drug delivery systems along with their corresponding surface modifications. The highlighting results obtained from the preclinical trial are promising and next five years have huge possibility move to the clinical setting. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Dry Sintering Meets Wet Silver-Ion "Soldering": Charge-Transfer Plasmon Engineering of Solution-Assembled Gold Nanodimers From Visible to Near-Infrared I and II Regions.

PubMed

Fang, Lingling; Wang, Yueliang; Liu, Miao; Gong, Ming; Xu, An; Deng, Zhaoxiang

2016-11-07

Achieving highly tunable and localized surface plasmon resonance up to near infrared (NIR) regions is a key target in nanoplasmonics. In particular, a self-assembly process capable of producing highly uniform and solution-processable nanomaterials with tailor-made plasmonic properties is lacking. We herein address this problem through a conjunctive use of wet Ag + soldering and dry thermal sintering to produce nanodimer-derived structures with precisely engineered charge-transfer plasmon (CTP). The sintered dimers are water soluble, featuring gradually shifted CTP spanning an 800 nm wavelength range (up to NIR II). Upon silica removal, the products are grafted by DNA to offer surface functionality. This process is also adaptable to DNA-linked AuNP dimers toward plasmonic meta-materials via DNA-guided soldering and sintering. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural Color Model Based on Surface Morphology of MORPHO Butterfly Wing Scale

NASA Astrophysics Data System (ADS)

Huang, Zhongjia; Cai, Congcong; Wang, Gang; Zhang, Hui; Huttula, Marko; Cao, Wei

2016-05-01

Color production through structural coloration is created by micrometer and sub-micrometer surface textures which interfere with visible light. The shiny blue of morpho menelaus is a typical example of structural coloring. Modified from morphology of the morpho scale, a structure of regular windows with two side offsets was constructed on glass substrates. Optical properties of the bioinspired structure were studied through numerical simulations of light scattering. Results show that the structure can generate monochromatic light scattering. Wavelength of scattered light is tunable via changing the spacing between window shelves. Compared to original butterfly model, the modified one possesses larger illumination scopes in azimuthal distributions despite being less in polar directions. Present bionic structure is periodically repeated and is easy to fabricate. It is hoped that the computational materials design work can inspire future experimental realizations of such a structure in photonics applications.

Thermal tuning On narrow linewidth fiber laser

NASA Astrophysics Data System (ADS)

Han, Peiqi; Liu, Tianshan; Gao, Xincun; Ren, Shiwei

2010-10-01

At present, people have been dedicated to high-speed and large-capacity optical fiber communication system. Studies have been shown that optical wavelength division multiplexing (WDM) technology is an effective means of communication to increase the channel capacity. Tunable lasers have very important applications in high-speed, largecapacity optical communications, and distributed sensing, it can provide narrow linewidth and tunable laser for highspeed optical communication. As the erbium-doped fiber amplifier has a large gain bandwidth, the erbium-doped fiber laser can be achieved lasing wavelength tunable by adding a tunable filter components, so tunable filter device is the key components in tunable fiber laser.At present, fiber laser wavelength is tuned by PZT, if thermal wavelength tuning is combined with PZT, a broader range of wavelength tuning is appearance . Erbium-doped fiber laser is used in the experiments,the main research is the physical characteristics of fiber grating temperature-dependent relationship and the fiber grating laser wavelength effects. It is found that the fiber laser wavelength changes continuously with temperature, tracking several temperature points observed the self-heterodyne spectrum and found that the changes in spectra of the 3dB bandwidth of less than 1kHz, and therefore the fiber laser with election-mode fiber Bragg grating shows excellent spectral properties and wavelength stability.

Semiconductor detector with smoothly tunable effective thickness for the study of ionization loss by moderately relativistic electrons

NASA Astrophysics Data System (ADS)

Shchagin, A. V.; Shul'ga, N. F.; Trofymenko, S. V.; Nazhmudinov, R. M.; Kubankin, A. S.

2016-11-01

The possibility of measurement of electrons ionization loss in Si layer of smoothly tunable thickness is shown in the proof-of-principle experiment. The Si surface-barrier detector with the depleted layer thickness controlled by the value of high voltage power supply has been used. Ionization loss spectra for electrons emitted by radioactive source 207Bi are presented and discussed. Experimental results for the most probable ionization loss in the Landau spectral peak are compared with theoretical calculations. The possibility of research of evolution of electromagnetic field of ultra-relativistic particles traversing media interface with the use of detectors with smoothly tunable thickness is proposed.

Low Profile Tunable Dipole Antennas Using BST Varactors for Biomedical Applications

NASA Technical Reports Server (NTRS)

Cure, David; Weller, Thomas; Price, Tony; Miranda, Felix A.

2013-01-01

In this presentation a 2.4 GHz low profile (lambda45) tunable dipole antenna is evaluated in the presence of a human core model (HCM) body phantom. The antenna uses a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells and its performance is compared to a similar low profile antenna that uses an FSS with semiconductor varactor diodes. The measured data of the antenna demonstrate tunability from 2.2 GHz to 2.55 GHz in free space and impedance match improvement in the presence of a HCM at different distances. This antenna has smaller size, lower cost and less weight compared to the semiconductor varactor diode counterpart.

Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode.

PubMed

Klinkhammer, Sönke; Liu, Xin; Huska, Klaus; Shen, Yuxin; Vanderheiden, Sylvia; Valouch, Sebastian; Vannahme, Christoph; Bräse, Stefan; Mappes, Timo; Lemmer, Uli

2012-03-12

The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured thickness profile. The laser threshold is low enough that inexpensive laser diodes can be used as pump sources.

Low Profile Tunable Dipole Antenna Using BST Varactors for Biomedical Applications

NASA Technical Reports Server (NTRS)

Cure, David; Weller, Thomas M.; Miranda, Felix A.; Price, Tony

2013-01-01

In this paper a 2.4 GHz low profile (lambda/47) tunable dipole antenna is evaluated in the presence of a human core model (HCM) body phantom. The antenna uses a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells and its performance is compared to a similar low profile antenna that uses an FSS with semiconductor varactor diodes. The measured data of the antenna demonstrate tunability from 2.2 GHz to 2.55 GHz in free space and impedance match improvement in the presence of a HCM at different distances. This antenna has smaller size, lower cost and less weight compared to the semiconductor varactor diode counterpart.

Approach to Rapid Synthesis and Functionalization of Iron Oxide Nanoparticles for High Gene Transfection.

PubMed

Stephen, Zachary R; Dayringer, Christopher J; Lim, Josh J; Revia, Richard A; Halbert, Mackenzie V; Jeon, Mike; Bakthavatsalam, Arvind; Ellenbogen, Richard G; Zhang, Miqin

2016-03-01

Surface functionalization of theranostic nanoparticles (NPs) typically relies on lengthy, aqueous postsynthesis labeling chemistries that have limited ability to fine-tune surface properties and can lead to NP heterogeneity. The need for a rapid, simple synthesis approach that can provide great control over the display of functional moieties on NP surfaces has led to increased use of highly selective bioorthoganol chemistries including metal-affinity coordination. Here we report a simple approach for rapid production of a superparamagnetic iron oxide NPs (SPIONs) with tunable functionality and high reproducibility under aqueous conditions. We utilize the high affinity complex formed between catechol and Fe((III)) as a means to dock well-defined catechol modified polymer modules on the surface of SPIONs during sonochemical coprecipitation synthesis. Polymer modules consisted of chitosan and poly(ethylene glycol) (PEG) copolymer (CP) modified with catechol (CCP), and CCP functionalized with cationic polyethylenimine (CCP-PEI) to facilitate binding and delivery of DNA for gene therapy. This rapid synthesis/functionalization approach provided excellent control over the extent of PEI labeling, improved SPION magnetic resonance imaging (MRI) contrast enhancement and produced an efficient transfection agent.

Surface-Cross-Linked Micelles as Multifunctionalized Organic Nanoparticles for Controlled Release, Light Harvesting, and Catalysis

PubMed Central

2016-01-01

Surfactant micelles are dynamic entities with a rapid exchange of monomers. By “clicking” tripropargylammonium-containing surfactants with diazide cross-linkers, we obtained surface-cross-linked micelles (SCMs) that could be multifunctionalized for different applications. They triggered membrane fusion through tunable electrostatic interactions with lipid bilayers. Antenna chromophores could be installed on them to create artificial light-harvesting complexes with efficient energy migration among tens to hundreds of chromophores. When cleavable cross-linkers were used, the SCMs could break apart in response to redox or pH signals, ejecting entrapped contents quickly as a result of built-in electrostatic stress. They served as caged surfactants whose surface activity was turned on by environmental stimuli. They crossed cell membranes readily. Encapsulated fluorophores showed enhanced photophysical properties including improved quantum yields and greatly expanded Stokes shifts. Catalytic groups could be installed on the surface or in the interior, covalently attached or physically entrapped. As enzyme mimics, the SCMs enabled rational engineering of the microenvironment around the catalysts to afford activity and selectivity not possible with conventional catalysts. PMID:27181610

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-01

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 107 and the detection limit can reach 10-10M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy.

PubMed

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-21

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 10(7) and the detection limit can reach 10(-10)M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

Optical properties of plasmonic nanostructures: Theory & experiments

NASA Astrophysics Data System (ADS)

Bala Krishna, Juluri

Metal nanoparticles and thin films enable localization of electromagnetic energy in the form of localized surface plasmon resonances (LSPR) and propagating surface plasmons respectively. This research field, also known as plasmonics, involves understanding and fabricating innovative nanostructures designed to manage and utilize localized light in the nanoscale. Advances in plasmonics will facilitate innovation in sensing, biomedical engineering, energy harvesting and nanophotonic devices. In this thesis, three aspects of plasmonics are studied: 1) active plasmonic systems using charge-induced plasmon shifts (CIPS) and plasmon-molecule resonant coupling; 2) scalable solutions to fabricate large electric field plasmonic nanostructures; and 3) controlling the propagation of designer surface plasmons (DSPs) using parabolic graded media. The full potential of plasmonics can be realized with active plasmonic devices which provide tunable plasmon resonances. The work reported here develops both an understanding for and realization of various mechanisms to achieve tunable plasmonic systems. First, we show that certain nanoparticle geometries and material compositions enable large CIPS. Second, we propose and investigate systems which exhibit coupling between molecular and plasmonic resonances where energy splitting is observed due to interactions between plasmons and molecules. Large electric field nanostructures have many promising applications in the areas of surface enhanced Raman spectroscopy, higher harmonic light generation, and enhanced uorescence. High throughput techniques that utilize simple nanofabrication are essential their advancement. We contribute to this effort by using a salting-out quenching technique and colloidal lithography to fabricate nanodisc dimers and cusp nanostructures that allow localization of large electric fields, and are comparable to structures fabricated by conventional lithography/milling techniques. Designer surface plasmons (DSPs) are surface waves that are localized to the interface between a structured perfect electric conductor (PEC) surface and dielectric medium. Terahertz (THz) DSPs excited on microscale structured PEC are localized in the out-of-plane direction, with negligible in-plane localization. We addressed this problem by subjecting DSPs to a parabolic graded-index structure. Lateral confinement such as focusing, collimation, and waveguiding of DSPs is demonstrated. Such control will pave the way towards THz energy concentration, diffusion, guiding, and beam aperture modifcation.

Tuning Wettability and Adhesion of Structured Surfaces

NASA Astrophysics Data System (ADS)

Badge, Ila

Structured surfaces with feature size ranging from a few micrometers down to nanometers are of great interest in the applications such as design of anti-wetting surfaces, tissue engineering, microfluidics, filtration, microelectronic devices, anti-reflective coatings and reversible adhesives. A specific surface property demands particular roughness geometry along with suitable surface chemistry. Plasma Enhanced Chemical Vapor Deposition (PECVD) is a technique that offers control over surface chemistry without significantly affecting the roughness and thus, provides a flexibility to alter surface chemistry selectively for a given structured surface. In this study, we have used PECVD to fine tune wetting and adhesion properties. The research presented focuses on material design aspects as well as the fundamental understanding of wetting and adhesion phenomena of structured surfaces. In order to study the effect of surface roughness and surface chemistry on the surface wettability independently, we developed a model surface by combination of colloidal lithography and PECVD. A systematically controlled hierarchical roughness using spherical colloidal particles and surface chemistry allowed for quantitative prediction of contact angles corresponding to metastable and stable wetting states. A well-defined roughness and chemical composition of the surface enabled establishing a correlation between theory predictions and experimental measurements. We developed an extremely robust superhydrophobic surface based on Carbon-Nanotubes (CNT) mats. The surface of CNTs forming a nano-porous mesh was modified using PECVD to deposit a layer of hydrophobic coating (PCNT). The PCNT surface thus formed is superhydrophobic with almost zero contact angle hysteresis. We demonstrated that the PCNT surface is not wetted under steam condensation even after prolonged exposure and also continues to retain its superhydrophobicity after multiple frosting-defrosting cycles. The anti-wetting behavior of PCNT surface is consistent with our model predictions, derived based on thermodynamic theory of wetting. The surface of gecko feet is a very unique natural structured surface. The hierarchical surface structure of a Gecko toe pad is responsible for its reversible adhesive properties and superhydrophobicity. van der Waals interactions is known to be the key mechanism behind Gecko adhesion. However, we found that the wettability, thus the surface chemistry plays a significant role in Gecko adhesion mechanism, especially in the case of underwater adhesion. We used PECVD process to deposit a layer of coating with known chemistry on the surface of sheds of gecko toes to study the effect that wettability of the toe surface has on its adhesion. In summary, we demonstrated that PECVD can be effectively used as means of surface chemistry control for tunable structure-property relationship of three types of structured surfaces; each having unique surface features.

Beam-splitter switches based on zenithal bistable liquid-crystal gratings.

PubMed

Zografopoulos, Dimitrios C; Beccherelli, Romeo; Kriezis, Emmanouil E

2014-10-01

The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.

Tunable wideband bandstop acoustic filter based on two-dimensional multiphysical phenomena periodic systems

NASA Astrophysics Data System (ADS)

Romero-García, V.; Sánchez-Pérez, J. V.; Garcia-Raffi, L. M.

2011-07-01

The physical properties of a periodic distribution of absorbent resonators is used in this work to design a tunable wideband bandstop acoustic filter. Analytical and numerical simulations as well as experimental validations show that the control of the resonances and the absorption of the scatterers along with their periodic arrangement in air introduce high technological possibilities to control noise. Sound manipulation is perhaps the most obvious application of the structures presented in this work. We apply this methodology to develop a device as an alternative to the conventional acoustic barriers with several properties from the acoustical point of view but also with additional esthetic and constructive characteristics.

Negative stiffness honeycombs as tunable elastic metamaterials

NASA Astrophysics Data System (ADS)

Goldsberry, Benjamin M.; Haberman, Michael R.

2018-03-01

Acoustic and elastic metamaterials are media with a subwavelength structure that behave as effective materials displaying atypical effective dynamic properties. These material systems are of interest because the design of their sub-wavelength structure allows for direct control of macroscopic wave dispersion. One major design limitation of most metamaterial structures is that the dynamic response cannot be altered once the microstructure is manufactured. However, the ability to modify wave propagation in the metamaterial with an external stimulus is highly desirable for numerous applications and therefore remains a significant challenge in elastic metamaterials research. In this work, a honeycomb structure composed of a doubly periodic array of curved beams, known as a negative stiffness honeycomb (NSH), is analyzed as a tunable elastic metamaterial. The nonlinear static elastic response that results from large deformations of the NSH unit cell leads to a large variation in linear elastic wave dispersion associated with infinitesimal motion superposed on the externally imposed pre-strain. A finite element model is utilized to model the static deformation and subsequent linear wave motion at the pre-strained state. Analysis of the slowness surface and group velocity demonstrates that the NSH exhibits significant tunability and a high degree of anisotropy which can be used to guide wave energy depending on static pre-strain levels. In addition, it is shown that partial band gaps exist where only longitudinal waves propagate. The NSH therefore behaves as a meta-fluid, or pentamode metamaterial, which may be of use for applications of transformation elastodynamics such as cloaking and gradient index lens devices.

Synthesis and sensing properties of D5h pentagonal silver star nanoparticles.

PubMed

Cathcart, Nicole; Coombs, Neil; Gourevich, Ilya; Kitaev, Vladimir

2016-11-03

In this work, we use silver decahedral nanoparticle (AgDeNP) seeds to synthesize pentagonal silver stars (AgStDeNPs) and study the sensing properties of these nanoparticles. The regrowth process of AgStDeNPs is kinetically-controlled, so the purity of the seed NPs is critical to avoid secondary deposition in the highly non-equilibrium reduction. To control the regrowth process, surface blocking with sodium polyacrylate (PANa) was implemented. PANa moderates rough silver nanostructures typically obtained by reduction with ascorbic acid. To modulate polymer binding to the surface and thus to tune surface blocking, pH served as a key synthetic parameter. Under optimal regrowth conditions, new sliver was deposited on the highest energy sites of the decahedra - the vertices of the rims - to yield pentagonal stars. The universality of this regrowth process was established with several different seed particles. The sharpness and size of the stellated tips are tunable by the amount of added silver. Gold deposition onto AgStDeNPs enables the preparation of diverse structures with enhanced stability. Ease of transformation, e.g. rounding, of star branches opens a promising venue for enhanced SPR sensing. Also, AgStDeNPs enable femtomolar detection of 5,5-dithiobis(2-nitrobenzoic acid) in SERS.

Structural and mechanical properties of glassy water in nanoscale confinement.

PubMed

Lombardo, Thomas G; Giovambattista, Nicolás; Debenedetti, Pablo G

2009-01-01

We investigate the structure and mechanical properties of glassy water confined between silica-based surfaces with continuously tunable hydrophobicity and hydrophilicity by computing and analyzing minimum energy, mechanically stable configurations (inherent structures). The structured silica substrate imposes long-range order on the first layer of water molecules under hydrophobic confinement at high density (p > or = 1.0 g cm(-3)). This proximal layer is also structured in hydrophilic confinement at very low density (p approximately 0.4 g cm(-3)). The ordering of water next to the hydrophobic surface greatly enhances the mechanical strength of thin films (0.8 nm). This leads to a substantial stress anisotropy; the transverse strength of the film exceeds the normal strength by 500 MPa. The large transverse strength results in a minimum in the equation of state of the energy landscape that does not correspond to a mechanical instability, but represents disruption of the ordered layer of water next to the wall. In addition, we find that the mode of mechanical failure is dependent on the type of confinement. Under large lateral strain, water confined by hydrophilic surfaces preferentially forms voids in the middle of the film and fails cohesively. In contrast, water under hydrophobic confinement tends to form voids near the walls and fails by loss of adhesion.

Multilength Scale Patterning of Functional Layers by Roll-to-Roll Ultraviolet-Light-Assisted Nanoimprint Lithography.

PubMed

Leitgeb, Markus; Nees, Dieter; Ruttloff, Stephan; Palfinger, Ursula; Götz, Johannes; Liska, Robert; Belegratis, Maria R; Stadlober, Barbara

2016-05-24

Top-down fabrication of nanostructures with high throughput is still a challenge. We demonstrate the fast (>10 m/min) and continuous fabrication of multilength scale structures by roll-to-roll UV-nanoimprint lithography on a 250 mm wide web. The large-area nanopatterning is enabled by a multicomponent UV-curable resist system (JRcure) with viscous, mechanical, and surface properties that are tunable over a wide range to either allow for usage as polymer stamp material or as imprint resist. The adjustable elasticity and surface chemistry of the resist system enable multistep self-replication of structured resist layers. Decisive for defect-free UV-nanoimprinting in roll-to-roll is the minimization of the surface energies of stamp and resist, and the stepwise reduction of the stiffness from one layer to the next is essential for optimizing the reproduction fidelity especially for nanoscale features. Accordingly, we demonstrate the continuous replication of 3D nanostructures and the high-throughput fabrication of multilength scale resist structures resulting in flexible polyethylenetherephtalate film rolls with superhydrophobic properties. Moreover, a water-soluble UV-imprint resist (JRlift) is introduced that enables residue-free nanoimprinting in roll-to-roll. Thereby we could demonstrate high-throughput fabrication of metallic patterns with only 200 nm line width.

Chemically Tunable Full Spectrum Optical Properties of 2D Silicon Telluride Nanoplates.

PubMed

Wang, Mengjing; Lahti, Gabriella; Williams, David; Koski, Kristie J

2018-06-07

Silicon telluride (Si 2 Te 3 ) is a two-dimensional, layered, p-type semiconductor that shows broad near-infrared photoluminescence. We show how, through various means of chemical modification, Si 2 Te 3 can have its optoelectronic properties modified in several independent ways without fundamentally altering the host crystalline lattice. Substitutional doping with Ge strongly redshifts the photoluminescence while substantially lowering the direct and indirect band gaps and altering the optical phonon modes. Intercalation with Ge introduces a sharp 4.3 eV ultraviolet resonance and shifts the bulk plasmon even while leaving the infrared response and band gaps virtually unchanged. Intercalation with copper strengthens the photoluminescence without altering its spectral shape. Thus silicon telluride is shown to be a chemically tunable platform of full spectrum optical properties promising for opto-electronic applications.

Ferroelectric and paraelectric Ba0.5Sr0.5TiO3 film structure distortions at room temperature and their effects on tunable microwave properties

NASA Astrophysics Data System (ADS)

Alldredge, L. M. B.; Chang, Wontae; Qadri, Syed B.; Kirchoefer, Steven W.; Pond, Jeffrey M.

2007-05-01

Sputter-deposited Ba0.5Sr0.5TiO3 films on (001) MgO were characterized for their dielectric properties with different lattice structures. With varying Ar :O2 ratios during deposition, the films showed either in-plane (ca) tetragonal distortions, significantly affecting the dielectric constant and tunability. The dielectric constant exhibited clear hysteresis with dc bias at room temperature, indicating that the films were ferroelectric. The relationship between the dielectric properties and the distortions was the reverse of that observed in films deposited by pulsed laser deposition. The anisotropic in-plane dielectric behavior can be understood by relating polarization to film distortions and to the presence of permanent dipoles.

Unique Zigzag-Shaped Buckling Zn2C Monolayer with Strain-Tunable Band Gap and Negative Poisson Ratio.

PubMed

Meng, Lingbiao; Zhang, Yingjuan; Zhou, Minjie; Zhang, Jicheng; Zhou, Xiuwen; Ni, Shuang; Wu, Weidong

2018-02-19

Designing new materials with reduced dimensionality and distinguished properties has continuously attracted intense interest for materials innovation. Here we report a novel two-dimensional (2D) Zn 2 C monolayer nanomaterial with exceptional structure and properties by means of first-principles calculations. This new Zn 2 C monolayer is composed of quasi-tetrahedral tetracoordinate carbon and quasi-linear bicoordinate zinc, featuring a peculiar zigzag-shaped buckling configuration. The unique coordinate topology endows this natural 2D semiconducting monolayer with strongly strain tunable band gap and unusual negative Poisson ratios. The monolayer has good dynamic and thermal stabilities and is also the lowest-energy structure of 2D space indicated by the particle-swarm optimization (PSO) method, implying its synthetic feasibility. With these intriguing properties the material may find applications in nanoelectronics and micromechanics.

Electronic properties and mechanical strength of β-phosphorene nano-ribbons

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

Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok, E-mail: ashok@cup.ac.in

We have performed first principles calculations to find out the effect of mechanical strain on the electronic properties of zig-zag edged nano ribbons of β-phosphorene. It is found that electronic band-gap get opened-up to 2.61 eV by passivation of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75 GPa to 2.65 GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The band-gap value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable properties ofmore » β-phospherene with passivation with H-atom and applying mechanical strain offer its use in tunable nano electronics.« less

Switchable and Tunable Bulk Acoustic Wave Devices Based on Ferroelectric Material

NASA Astrophysics Data System (ADS)

Mansour, Almonir

The explosive development of personal communications systems, navigation, satellite communications as well as personal computer and data processing systems together with the constant demand for higher speeds and larger bandwidths has driven fabrication technology to its limits. This, in turn, necessitates the development of novel functional materials for the fabrication of devices with superior performance and higher capacity at reduced manufacturing costs. Ferroelectric materials such as barium strontium titanate (BST) and strontium titanium oxide (STO) have received more attention by researchers and industry because of their field-induced piezoelectric property. This property gives these types of ferroelectric materials the ability to be switchable and tunable in the presence of an electric field. These features have allowed the ferroelectric materials to be used in many applications such as non-volatile memory and DRAMs, sensors, pyroelectric detectors, and tunable microwave devices. Therefore, with the ever increasing complexity in RF front-end receivers, and the demand for services (which in turn requires more functionalities), ferroelectric bulk acoustic wave (BAW) resonators and filters that are intrinsically switchable and tunable promise to reduce the size and complexity of component parts. In this work, we present the design, fabrication and experimental evaluation of switchable and tunable thin film bulk acoustic wave (BAW) resonators, filters and duplexers for radio frequency (RF) applications. The switchability and tunability of these devices come from utilizing the electrostrictive effect of ferroelectric materials such as barium strontium titanate (BST) with the application of an external DC-bias voltage. The BAW resonators, filters and duplexers in this work were fabricated on different substrates as solidly mounted resonator (SMR) structure with number of periodic layers of silicon dioxide and tantalum oxide as a Bragg reflector in order to acoustically isolate the resonator from the damping effect of the substrate, enhancing the quality factor and temperature compensation.

Flatland Photonics: Circumventing Diffraction with Planar Plasmonic Architectures

NASA Astrophysics Data System (ADS)

Dionne, Jennifer Anne

On subwavelength scales, photon-matter interactions are limited by diffraction. The diffraction limit restricts the size of optical devices and the resolution of conventional microscopes to wavelength-scale dimensions, severely hampering our ability to control and probe subwavelength-scale optical phenomena. Circumventing diffraction is now a principle focus of integrated nanophotonics. Surface plasmons provide a particularly promising approach to sub-diffraction-limited photonics. Surface plasmons are hybrid electron-photon modes confined to the interface between conductors and transparent materials. Combining the high localization of electronic waves with the propagation properties of optical waves, plasmons can achieve extremely small mode wavelengths and large local electromagnetic field intensities. Through their unique dispersion, surface plasmons provide access to an enormous phase space of refractive indices and propagation constants that can be readily tuned with material or geometry. In this thesis, we explore both the theory and applications of dispersion in planar plasmonic architectures. Particular attention is given to the modes of metallic core and plasmon slot waveguides, which can span positive, near-zero, and even negative indices. We demonstrate how such basic plasmonic geometries can be used to develop a suite of passive and active plasmonic components, including subwavelength waveguides, color filters, negative index metamaterials, and optical MOS field effect modulators. Positive index modes are probed by near- and far-field techniques, revealing plasmon wavelengths as small as one-tenth of the excitation wavelength. Negative index modes are characterized through direct visualization of negative refraction. By fabricating prisms comprised of gold, silicon nitride, and silver multilayers, we achieve the first experimental demonstration of a negative index material at visible frequencies, with potential applications for sub-diffraction-limited microscopy and electromagnetic cloaking. We exploit this tunability of complex plasmon mode indices to create a compact metal-oxide-Si (MOS) field effect plasmonic modulator (or plasMOStor). By transforming the MOS gate oxide into an optical channel, amplitude modulation depths of 11.2 dB are achieved in device volumes as small as one one-fifth of a cubic wavelength. Our results indicate the accessibility of tunable refractive indices over a wide frequency band, facilitating design of a new materials class with extraordinary optical properties and applications.

Biomimetic oral mucin from polymer micelle networks

NASA Astrophysics Data System (ADS)

Authimoolam, Sundar Prasanth

Mucin networks are formed by the complexation of bottlebrush-like mucin glycoprotein with other small molecule glycoproteins. These glycoproteins create nanoscale strands that then arrange into a nanoporous mesh. These networks play an important role in ensuring surface hydration, lubricity and barrier protection. In order to understand the functional behavior in mucin networks, it is important to decouple their chemical and physical effects responsible for generating the fundamental property-function relationship. To achieve this goal, we propose to develop a synthetic biomimetic mucin using a layer-by-layer (LBL) deposition approach. In this work, a hierarchical 3-dimensional structures resembling natural mucin networks was generated using affinity-based interactions on synthetic and biological surfaces. Unlike conventional polyelectrolyte-based LBL methods, pre-assembled biotin-functionalized filamentous (worm-like) micelles was utilized as the network building block, which from complementary additions of streptavidin generated synthetic networks of desired thickness. The biomimetic nature in those synthetic networks are studied by evaluating its structural and bio-functional properties. Structurally, synthetic networks formed a nanoporous mesh. The networks demonstrated excellent surface hydration property and were able capable of microbial capture. Those functional properties are akin to that of natural mucin networks. Further, the role of synthetic mucin as a drug delivery vehicle, capable of providing localized and tunable release was demonstrated. By incorporating antibacterial curcumin drug loading within synthetic networks, bacterial growth inhibition was also demonstrated. Thus, such bioactive interfaces can serve as a model for independently characterizing mucin network properties and through its role as a drug carrier vehicle it presents exciting future opportunities for localized drug delivery, in regenerative applications and as bio-functional implant coats. KEYWORDS: Biomimic, Bioapplication, Drug delivery, Filomicelle, Mucin, Polymer networks.

Optical performance of a PDMS tunable lens with automatically controlled applied stress

NASA Astrophysics Data System (ADS)

Cruz-Felix, Angel S.; Santiago-Alvarado, Agustín.; Hernández-Méndez, Arturo; Reyes-Pérez, Emilio R.; Tepichín-Rodriguez, Eduardo

2016-09-01

The advances in the field of adaptive optics and in the fabrication of tunable optical components capable to automatically modify their physical features are of great interest in areas like machine vision, imaging systems, ophthalmology, etc. Such components like tunable lenses are used to reduce the overall size of optical setups like in small camera systems and even to imitate some biological functions made by the human eye. In this direction, in the last years we have been working in the development and fabrication of PDMS-made tunable lenses and in the design of special mechanical mounting systems to manipulate them. A PDMS-made tunable lens was previously designed by us, following the scheme reported by Navarro et al. in 1985, in order to mimic the accommodation process made by the crystalline lens of the human eye. The design included a simulation of the application of radial stress onto the lens and it was shown that the effective focal length was indeed changed. In this work we show the fabrication process of this particular tunable lens and an optimized mechanism that is able to automatically change the curvature of both surfaces of the lens by the application of controlled stress. We also show results of a study and analysis of aberrations performed to the Solid Elastic Lens (SEL).

Nanosecond laser ablated copper superhydrophobic surface with tunable ultrahigh adhesion and its renewability with low temperature annealing

NASA Astrophysics Data System (ADS)

He, An; Liu, Wenwen; Xue, Wei; Yang, Huan; Cao, Yu

2018-03-01

Recently, metallic superhydrophobic surfaces with ultrahigh adhesion have got plentiful attention on account of their significance in scientific researches and industrial applications like droplet transport, drug delivery and novel microfluidic devices. However, the long lead time and transience hindered its in-depth development and industrial application. In this work, nanosecond laser ablation was carried out to construct grid of micro-grooves on copper surface, whereafter, by applying fast ethanol assisted low-temperature annealing, we obtained surface with superhydrophobicity and ultrahigh adhesion within hours. And the ultrahigh adhesion force was found tunable by varying the groove spacing. Using ultrasonic cleaning as the simulation of natural wear and tear in service, the renewability of superhydrophobicity was also investigated, and the result shows that the contact angle can rehabilitate promptly by the processing of ethanol assisted low-temperature annealing, which gives a promising fast and cheap circuitous strategy to realize the long wish durable metallic superhydrophobic surfaces in practical applications.

Reversible structural modulation of Fe-Pt bimetallic surfaces and its effect on reactivity.

PubMed

Ma, Teng; Fu, Qiang; Su, Hai-Yan; Liu, Hong-Yang; Cui, Yi; Wang, Zhen; Mu, Ren-Tao; Li, Wei-Xue; Bao, Xin-He

2009-05-11

Tunable surface: The surface structure of the Fe-Pt bimetallic catalyst can be reversibly modulated between the iron-oxide-rich Pt surface and the Pt-skin structure with subsurface Fe via alternating reduction and oxidation treatments (see figure). The regenerated active Pt-skin structure is active in reactions involving CO and/or O.

Low temperature perovskite crystallization of highly tunable dielectric Ba0.7Sr0.3TiO3 thick films deposited by ion beam sputtering on platinized silicon substrates

NASA Astrophysics Data System (ADS)

Zhu, X. H.; Guigues, B.; Defaÿ, E.; Dubarry, C.; Aïd, M.

2009-02-01

Ba0.7Sr0.3TiO3 (BST) thick films with thickness up to 1 μm were deposited on Pt-coated silicon substrates by ion beam sputtering, followed by an annealing treatment. It is demonstrated that pure well-crystallized perovskite phase could be obtained in thick BST films by a low temperature process (535 °C). The BST thick films show highly tunable dielectric properties with tunability (at 800 kV/cm) up to 51.0% and 66.2%, respectively, for the 0.5 and 1 μm thick films. The relationship between strains and dielectric properties was systematically investigated in the thick films. The results suggest that a comparatively larger tensile thermal in-plane strain (0.15%) leads to the degradation in dielectric properties of the 0.5 μm thick film; besides, strong defect-related inhomogeneous strains (˜0.3%) make the dielectric peaks smearing and broadening in the thick films, which, however, preferably results in high figure-of-merit factors over a wide operating temperature range. Moreover, the leakage current behavior in the BST thick films was found to be dominated by the space-charge-limited-current mechanism, irrespective of the film thickness.

Sub–100-nm metafluorophores with digitally tunable optical properties self-assembled from DNA

PubMed Central

Woehrstein, Johannes B.; Strauss, Maximilian T.; Ong, Luvena L.; Wei, Bryan; Zhang, David Y.; Jungmann, Ralf; Yin, Peng

2017-01-01

Fluorescence microscopy allows specific target detection down to the level of single molecules and has become an enabling tool in biological research. To transduce the biological information to an imageable signal, we have developed a variety of fluorescent probes, such as organic dyes or fluorescent proteins with different colors. Despite their success, a limitation on constructing small fluorescent probes is the lack of a general framework to achieve precise and programmable control of critical optical properties, such as color and brightness. To address this challenge, we introduce metafluorophores, which are constructed as DNA nanostructure–based fluorescent probes with digitally tunable optical properties. Each metafluorophore is composed of multiple organic fluorophores, organized in a spatially controlled fashion in a compact sub–100-nm architecture using a DNA nanostructure scaffold. Using DNA origami with a size of 90 × 60 nm2, substantially smaller than the optical diffraction limit, we constructed small fluorescent probes with digitally tunable brightness, color, and photostability and demonstrated a palette of 124 virtual colors. Using these probes as fluorescent barcodes, we implemented an assay for multiplexed quantification of nucleic acids. Additionally, we demonstrated the triggered in situ self-assembly of fluorescent DNA nanostructures with prescribed brightness upon initial hybridization to a nucleic acid target. PMID:28691083

Tunable resistance coatings

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

Elam, Jeffrey W.; Mane, Anil U.

2015-08-11

A method and article of manufacture of intermixed tunable resistance composite materials containing at least one of W:Al.sub.2O.sub.3, Mo:Al.sub.2O.sub.3 or M:Al.sub.2O.sub.3 where M is a conducting compound containing either W or Mo. A conducting material and an insulating material are deposited by such methods as ALD or CVD to construct composites with intermixed materials which do not have structure or properties like their bulk counterparts.

Tunable Polymer Lens

DTIC Science & Technology

2008-08-04

can also be initiated mechanically to produce variable lenses [9-11]. Recent work shows lens properties of a controlled liquid drop shape, with no... liquid crystal spherical lens ," Appl. Phys. Lett. 84, 4789-4791 (2004). 3. H. W. Ren, D. W. Fox, B. Wu, and S. T. Wu, " Liquid crystal lens with large...and S. S. Lee, "Focal tunable liquid lens integrated with an electromagnetic actuator," Appl. Phys. Lett. 90, 121129 (2007). 10. H. W. Ren, D. Fox

Control of Wannier orbitals for generating tunable Ising interactions of ultracold atoms in an optical lattice

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

Inaba, Kensuke; Tamaki, Kiyoshi; Igeta, Kazuhiro

2014-12-04

In this study, we propose a method for generating cluster states of atoms in an optical lattice. By utilizing the quantum properties of Wannier orbitals, we create an tunable Ising interaction between atoms without inducing the spin-exchange interactions. We investigate the cause of errors that occur during entanglement generations, and then we propose an error-management scheme, which allows us to create high-fidelity cluster states in a short time.

Nanorice Particles: Hybrid Plasmonic Nanostructures

NASA Technical Reports Server (NTRS)

Le, Fei (Inventor); Halas, Nancy J. (Inventor); Nordlander, Peter (Inventor); Brandl, Daniel (Inventor); Wang, Hui (Inventor)

2010-01-01

A new hybrid nanoparticle, i.e., a nanorice particle, which combines the intense local fields of nanorods with the highly tunable plasmon resonances of nanoshells, is described herein. This geometry possesses far greater structural tunability than previous nanoparticle geometries, along with much larger local field enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than presently known dielectric-conductive material nanostructures. In an embodiment, a nanoparticle comprises a prolate spheroid-shaped core having a first aspect ratio. The nanoparticle also comprises at least one conductive shell surrounding said prolate spheroid-shaped core. The nanoparticle has a surface plasmon resonance sensitivity of at least 600 nm RIU(sup.-1). Methods of making the disclosed nanorice particles are also described herein.

Enhanced and tunable electric dipole-dipole interactions near a planar metal film

NASA Astrophysics Data System (ADS)

Zhou, Lei-Ming; Yao, Pei-Jun; Zhao, Nan; Sun, Fang-Wen

2017-08-01

We investigate the enhanced electric dipole-dipole interaction of surface plasmon polaritons (SPPs) supported by a planar metal film waveguide. By taking two nitrogen-vacancy (NV) center electric dipoles in diamond as an example, both the coupling strength and collective relaxation of two dipoles are studied with the numerical Green Function method. Compared to two-dipole coupling on a planar surface, metal film provides stronger and tunable coupling coefficients. Enhancement of the interaction between coupled NV center dipoles could have applications in both quantum information and energy transfer investigation. Our investigation provides systematic results for experimental applications based on a dipole-dipole interaction mediated with SPPs on a planar metal film.

Experimental demonstration of tunable directional excitation of surface plasmon polaritons with a subwavelength metallic double slit

NASA Astrophysics Data System (ADS)

Li, Xiaowei; Tan, Qiaofeng; Bai, Benfeng; Jin, Guofan

2011-06-01

We demonstrate experimentally the directional excitation of surface plasmon polaritons (SPPs) on a metal film by a subwavelength double slit under backside illumination, based on the interference of SPPs generated by the two slits. By varying the incident angle, the SPPs can be tunably directed into two opposite propagating directions with a predetermined splitting ratio. Under certain incident angle, unidirectional SPP excitation can be achieved. This compact directional SPP coupler is potentially useful for many on-chip applications. As an example, we show the integration of the double-slit couplers with SPP Bragg mirrors, which can effectively realize selective coupling of SPPs into different ports in an integrated plasmonic chip.

Tunable and highly reproducible surface-enhanced Raman scattering substrates made from large-scale nanoparticle arrays based on periodically poled LiNbO3 templates

NASA Astrophysics Data System (ADS)

Liu, Xiaoyan; Kitamura, Kenji; Yu, Qiuming; Xu, Jiajie; Osada, Minoru; Takahiro, Nagata; Li, Jiangyu; Cao, Guozhong

2013-10-01

This work describes novel surface-enhanced Raman scattering (SERS) substrates based on ferroelectric periodically poled LiNbO3 templates. The templates comprise silver nanoparticles (AgNPs), the size and position of which are tailored by ferroelectric lithography. The substrate has uniform and large sampling areas that show SERS effective with excellent signal reproducibility, for which the fabrication protocol is advantageous in its simplicity. We demonstrate ferroelectric-based SERS substrates with particle sizes ranging from 30 to 70 nm and present tunable SERS effect from Raman active 4-mercaptopyridine molecules attached to AgNPs when excited by a laser source at 514 nm.

Electrically Tunable Nd:YAG waveguide laser based on Graphene

PubMed Central

Ma, Linan; Tan, Yang; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

2016-01-01

We demonstrate a tunable hybrid Graphene-Nd:YAG cladding waveguide laser exploiting the electro-optic and the Joule heating effects of Graphene. A cladding Nd:YAG waveguide was fabricated by the ion irradiation. The multi-layer graphene were transferred onto the waveguide surface as the saturable absorber to get the Q-switched pulsed laser oscillation in the waveguide. Composing with appropriate electrodes, graphene based capacitance and heater were formed on the surface of the Nd:YAG waveguide. Through electrical control of graphene, the state of the hybrid waveguide laser was turned on or off. And the laser operation of the hybrid waveguide was electrically tuned between the continuous wave laser and the nanosecond pulsed laser. PMID:27833114

Self-Assembled N-Heterocyclic Carbene-Based Carboxymethylated Dextran Monolayers on Gold as a Tunable Platform for Designing Affinity-Capture Biosensor Surfaces.

PubMed

Li, Zhijun; Munro, Kim; Narouz, Mina R; Lau, Andrew; Hao, Hongxia; Crudden, Cathleen M; Horton, J Hugh

2018-05-30

Sensor surfaces play a predominant role in the development of optical biosensor technologies for the analysis of biomolecular interactions. Thiol-based self-assembled monolayers (SAMs) on gold have been widely used as linker layers for sensor surfaces. However, the degradation of the thiol-gold bond can limit the performance and durability of such surfaces, directly impacting their performance and cost-effectiveness. To this end, a new family of materials based on N-heterocyclic carbenes (NHCs) has emerged as an alternative for surface modification, capable of self-assembling onto a gold surface with higher affinity and superior stability as compared to the thiol-based systems. Here we demonstrate three applications of NHC SAMs supporting a dextran layer as a tunable platform for developing various affinity-capture biosensor surfaces. We describe the development and testing of NHC-based dextran biosensor surfaces modified with each of streptavidin, nitrilotriacetic acid, and recombinant Protein A. These affinity-capture sensor surfaces enable oriented binding of ligands for optimal performance in biomolecular assays. Together, the intrinsic high stability and flexible design of the NHC biosensing platforms show great promise and open up exciting possibilities for future biosensing applications.

Thermomechanical and chemical properties of porous W/liquid Li hybrid systems as plasma-facing self-healing surfaces

NASA Astrophysics Data System (ADS)

Kapat, Aveek; Lang, Eric; Neff, Anton; Allain, Jean Paul

2017-10-01

The environmental conditions at the plasma-material interface of a future nuclear fusion reactor interacting will be extreme. The incident plasma will carry heat fluxes of the order of 100's of MWm-2 and particle fluxes that can average 1024 m-2s-1. The fusion reactor wall would need to operate at high temperatures near 800 C and the incident energy of particles will vary from a few eV ions to MeV neutrons. A hybrid system, inspired by self-healing solid-state concepts, combines the ductile phase of liquid Li within a solid phase porous W. The liquid Li serves to control hydrogen retention and provide vapor shielding, within the framework of a tunable porosity to optimize edge plasma conditions [2]. Additionally, the porous interface can also provide for effective defect sinks for high duty cycle neutron damage. The surface chemistry of liquid Li on a porous surface varied with D irradiation is studied and its effect on retention. Prior results with refractory alloys have demonstrated effective wetting properties [3]. These hybrid systems, as well as traditional W samples, are bombarded with 500eV D2+and Ar+ at 230oC and 300oC. The Li, O, and C XPS peaks were examined and compared to controls. Additionally, the porous W is characterized for thermo-mechanical properties. Work supported by USDOE Contract DE- DE-SC0014267.

Supramolecular assembly of borate with quaternary ammonium: Crystal structure and tunable luminescent properties

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

Liang, Jie; Wang, Yong-gang; Wang, Ying-xia, E-mail: wangyx@pku.edu.cn

2013-04-15

A new borate [C{sub 6}H{sub 16}N][B{sub 5}O{sub 6}(OH){sub 4}] (1) is synthesized hydrothermally by the reaction of isopropyltrimethylammonium hydroxide with boric acid. It crystallizes in the triclinic space group P-1 with the parameters a=9.1578(10) Å, b=9.372(9) Å, c=9.9812(10) Å, α=66.508(2)°, β=74.751(2)°, γ=81.893(2)°. The [B{sub 5}O{sub 6}(OH){sub 4}]{sup −} anions are interlinked via hydrogen bonding forming a 3D supramolecular network containing large cavities, where reside the (CH{sub 3}){sub 3}(i-C{sub 3}H{sub 7}) N{sup +} cations. This borate shows tunable luminescent properties with temperature, heating-treatment, exciting-light, and solvents. The fluorescent intensity of 1 enhances 6-fold with decreasing the temperature from 25 K tomore » 78 K. By treatment under different temperatures, the luminescence of 1 shifted from blue to white and the sample treated at 230 °C emits bright white light to naked eyes. The hybrid borate can disperse in different solvents, and shows a red-shifted and intense emission in polar solvents. - Graphical abstract: The new quaternary ammonium borate [C{sub 6}H{sub 17}N][B{sub 5}O{sub 6}(OH){sub 4}] contains a 3D supramolecular network formed by hydrogen bond linked [B{sub 5}O{sub 6}(OH){sub 4}]{sup −} anions and shows tunable luminescent properties with temperature, excitation light, and solvents. Highlights: ► A novel quaternary ammonium borate was synthesized. ► It possesses a supramolecular network fomed by H-bonded [B{sub 5}O{sub 6}(OH){sub 4}]{sup −} anions. ► This borate shows tunable luminescent properties with temperature, heating treatment, excitation light, and solvents.« less

Transition Metal Nanomaterials by Bacterial Precipitation: Synthesis and Characterization of Cadmium Sulfide Quantum Dots

NASA Astrophysics Data System (ADS)

Marusak, Katherine Elizabeth

We present a new method to fabricate semiconducting, transition metal nanoparticles (NPs) with tunable bandgap energies using engineered Escherichia coli. These bacteria overexpress the Treponema denticola cysteine desulfhydrase gene to facilitate precipitation of cadmium sulfide (CdS) NPs. Multiple characterization techniques reveal that the bacterially precipitated NPs are agglomerates of mostly quantum dots, with diameters that can range from 3 to 15 nm, embedded in a carbon-rich matrix. Notably, the measured photoelectrochemical current generated by these NPs is comparable to values reported in the literature and higher than that of synthesized chemical bath deposited CdS NPs. We showed that we can manipulate the bandgap energy of the NPs by controlling their size through varying the precursor concentrations. Our calculated bandgap energies ranged between 2.67 eV (i.e., quantum confined CdS) to 2.36 eV ( i.e., bulk CdS). By adding the CdCl2 precursor at a specific stage of the bacterial growth cycle, we were able to induce extracellular CdS NP precipitation. Additionally, we adapted extracellular precipitation strategies to form CdS NPs on surfaces as bacterial/PC membrane composites and characterized them by spectroscopic and imaging methods, including energy dispersive spectroscopy, and scanning and transmission electron microscopy. This method allowed us to control the localization of NP precipitation throughout the layered bacterial/membrane composite, by varying the timing of the cadmium precursor addition. Additionally, we demonstrated the photodegradation of methyl orange using the CdS functionalized porous membranes, thus confirming the photocatalytic properties of our composites for eventual translation to device development. We finally also explored the precipitation of other metallic NPs using our bacterial system, using enzyme extracted from our bacterial system, and using commercially available, his-tagged enzyme. We hope to extend this research to tethering enzymes on surfaces to direct NP precipitation. Taken all together, our results show the great promise bacteria have for the fabrication of tunable, transition metal NPs with useful electronic properties.

Flexible Teflon nanocone array surfaces with tunable superhydrophobicity for self-cleaning and aqueous droplet patterning.

PubMed

Toma, Mana; Loget, Gabriel; Corn, Robert M

2014-07-23

Tunable hydrophobic/hydrophilic flexible Teflon nanocone array surfaces were fabricated over large areas (cm(2)) by a simple two-step method involving the oxygen plasma etching of a colloidal monolayer of polystyrene beads on a Teflon film. The wettability of the nanocone array surfaces was controlled by the nanocone array dimensions and various additional surface modifications. The resultant Teflon nanocone array surfaces were hydrophobic and adhesive (a "gecko" type of surface on which a water droplet has a high contact angle but stays in place) with a contact angle that correlated with the aspect ratio/sharpness of the nanocones. The surfaces switched to a superhydrophobic or "lotus" type of surface when hierarchical nanostructures were created on Teflon nanocones by modifying them with a gold nanoparticle (AuNPs) film. The nanocone array surfaces could be made superhydrophobic with a maximum contact angle of 160° by the further modification of the AuNPs with an octadecanethiol (C18SH) monolayer. Additionally, these nanocone array surfaces became hydrophilic when the nanocone surfaces were sequentially modified with AuNPs and hydrophilic polydopamine (PDA) layers. The nanocone array surfaces were tested for two potential applications: self-cleaning superhydrophobic surfaces and for the passive dispensing of aqueous droplets onto hybrid superhydrophobic/hydrophilic microarrays.

Dual-enhanced photothermal conversion properties of reduced graphene oxide-coated gold superparticles for light-triggered acoustic and thermal theranostics†

PubMed Central

Lin, Li-Sen; Yang, Xiangyu; Niu, Gang

2017-01-01

A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles–graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications. PMID:26726809

Electric field-tunable Ba{sub x}Sr{sub 1-x}TiO{sub 3} films with high figures of merit grown by molecular beam epitaxy

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

Mikheev, Evgeny; Kajdos, Adam P.; Hauser, Adam J.

2012-12-17

We report on the dielectric properties of Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BST) films grown by molecular beam epitaxy on epitaxial Pt bottom electrodes. Paraelectric films (x Less-Than-Or-Equivalent-To 0.5) exhibit dielectric losses that are similar to those of BST single crystals and ceramics. Films with device quality factors greater than 1000 and electric field tunabilities exceeding 1:5 are demonstrated. The results provide evidence for the importance of stoichiometry control and the use of a non-energetic deposition technique for achieving high figures of merit of tunable devices with BST thin films.

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

DOE PAGES

Dorrer, C.; Consentino, A.; Cuffney, R.; ...

2017-10-18

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

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

Dorrer, C.; Consentino, A.; Cuffney, R.

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Substituent-Modulated Assembly Formation: An Approach to Enhancing the Photostability of Photoelectric-Sensitive Chalcogenide-Based Ion-Pair Hybrids.

PubMed

Lin, Jian; Fu, Zhixing; Zhang, Jiaxu; Zhu, Yujia; Hu, Dandan; Li, Dongsheng; Wu, Tao

2017-03-20

A series of electronically active viologen dications (RV) with tunable substituent groups were utilized to hybridize with [Ge 4 S 10 ] 4- (T2 cluster) to form the hybrids of T2@RV. These hybrids exhibited variable supermolecular assembly formation, tunable optical absorption properties, and different photoelectric response under the influence of different RV dications. Raman testing and time-dependent photocurrent response indicated that the photosensitivity and photostability of T2@RV could be integrated while choosing suitable RV dications. Current research provides a general method to build a tunable hybrid system based on crystalline metal chalcogenide compounds through the replacement of photoinactive cationic organic templates with photoactive ones with different substituent groups.

Pathway towards Programmable Wave Anisotropy in Cellular Metamaterials

NASA Astrophysics Data System (ADS)

Celli, Paolo; Zhang, Weiting; Gonella, Stefano

2018-01-01

In this work, we provide a proof-of-concept experimental demonstration of the wave-control capabilities of cellular metamaterials endowed with populations of tunable electromechanical resonators. Each independently tunable resonator comprises a piezoelectric patch and a resistor-inductor shunt, and its resonant frequency can be seamlessly reprogrammed without interfering with the cellular structure's default properties. We show that, by strategically placing the resonators in the lattice domain and by deliberately activating only selected subsets of them, chosen to conform to the directional features of the beamed wave response, it is possible to override the inherent wave anisotropy of the cellular medium. The outcome is the establishment of tunable spatial patterns of energy distillation resulting in a nonsymmetric correction of the wave fields.

Toward individually tunable compound eyes with transparent graphene electrode.

PubMed

Shahini, Ali; Jin, Hai; Zhou, Zhixian; Zhao, Yang; Chen, Pai-Yen; Hua, Jing; Cheng, Mark Ming-Cheng

2017-06-08

We present tunable compound eyes made of ionic liquid lenses, of which both curvatures (R 1 and R 2 in the lensmaker's equation) can be individually changed using electrowetting on dielectric (EWOD) and applied pressure. Flexible graphene is used as a transparent electrode and is integrated on a flexible polydimethylsiloxane (PDMS)/parylene hybrid substrate. Graphene electrodes allow a large lens aperture diameter of between 2.4 mm and 2.74 mm. Spherical aberration analysis is performed using COMSOL to investigate the optical property of the lens under applied voltage and pressure. The final lens system shows a resolution of 645.1 line pair per millimeter. A prototype of a tunable lens array is proposed for the application of a compound eye.

Broadband tunable electromagnetically induced transparency analogue metamaterials based on graphene in terahertz band

NASA Astrophysics Data System (ADS)

Wang, Yue; Leng, Yanbing; Wang, Li; Dong, Lianhe; Liu, Shunrui; Wang, Jun; Sun, Yanjun

2018-06-01

Most of the actively controlled electromagnetically induced transparency analogue (EIT-like) metamaterials were implemented with narrowband modulations. In this paper, a broadband tunable EIT-like metamaterial based on graphene in the terahertz band is presented. It consists of a cut wire as the bright resonator and two couples of H-shaped resonators in mirror symmetry as the dark resonators. A broadband tunable property of transmission amplitude is realized by changing the Fermi level of graphene. Furthermore, the geometries of the metamaterial structure are optimized to achieve the ideal curve through the simulation. Such EIT-like metamaterials proposed here are promising candidates for designing active wide-band slow-light devices, wide-band terahertz active filters, and wide-band terahertz modulators.

Tunable Microstrip Filters Using Selectively Etched Ferroelectric Thin-Film Varactors for Coupling

NASA Technical Reports Server (NTRS)

Mueller, Carl H.; VanKeuls, Frederick W.; Romanofsky, Robert R.; Subramanyam, Guru; Miranda, Felix A.

2006-01-01

We report on the use of patterned ferroelectric films to fabricate proof of concept tunable one-pole microstrip filters with excellent transmission and mismatch/reflection properties at frequencies up to 24 GHz. By controlling the electric field distribution within the coupling region between the resonator and input/output lines, sufficiently high loaded and unloaded Q values are maintained so as to be useful for microstrip filter design, with low mismatch loss. In the 23 - 24 GHz region, the filter was tunable over a 100 MHz range, the loaded and unloaded Q values were 29 and 68, respectively, and the reflection losses were below -16 dB, which demonstrates the suitability of these films for practical microwave applications.

Tunable plasmon-induced transparency with graphene-based T-shaped array metasurfaces

NASA Astrophysics Data System (ADS)

Niu, Yuying; Wang, Jicheng; Hu, Zhengda; Zhang, Feng

2018-06-01

The frequency tunable Plasmonic induced transparency (PIT) effect is researched with a periodically patterned T-shaped graphene array in mid-infrared region. We adjust the geometrical parameters to obtain the optimized combination for the realization of the PIT response and use the coupled Lorentz oscillator model to analysis the physical mechanism. Due to the properties of graphene, the PIT effect can be easily and markedly enhanced with the increase of chemical potential and carrier mobility. The frequency of PIT effect is also insensitive with the angle of incident light. In addition, we also propose the π shaped structure to realizing the double-peak PIT effect. The results offer a flexible approach for the development of tunable graphene-based photonic devices.

Quasi-Airy beams along tunable propagation trajectories and directions.

PubMed

Qian, Yixian; Zhang, Site

2016-05-02

We present a theoretical and experimental exhibit that accelerates quasi-Airy beams propagating along arbitrarily appointed parabolic trajectories and directions in free space. We also demonstrate that such quasi-Airy beams can be generated by a tunable phase pattern, where two disturbance factors are introduced. The topological structures of quasi-Airy beams are readily manipulated with tunable phase patterns. Quasi-Airy beams still possess the characteristics of non-diffraction, self-healing to some extent, although they are not the solutions for paraxial wave equation. The experiments show the results are consistent with theoretical predictions. It is believed that the property of propagation along arbitrarily desired parabolic trajectories will provide a broad application in trapping atom and living cell manipulation.

Optically Tunable Chiral Plasmonic Guest-Host Cellulose Films Weaved with Long-range Ordered Silver Nanowires.

PubMed

Chu, Guang; Wang, Xuesi; Chen, Tianrui; Gao, Jianxiong; Gai, Fangyuan; Wang, Yu; Xu, Yan

2015-06-10

Plasmonic materials with large chiroptical activity at visible wavelength have attracted considerable attention due to their potential applications in metamaterials. Here we demonstrate a novel guest-host chiral nematic liquid crystal film composed of bulk self-co-assembly of the dispersed plasmonic silver nanowires (AgNWs) and cellulose nanocrystals (CNCs). The AgNWs-CNCs composite films show strong plasmonic optical activities, that are dependent on the chiral photonic properties of the CNCs host medium and orientation of the guest AgNWs. Tunable chiral distribution of the aligned anisotropic AgNWs with long-range order is obtained through the CNCs liquid crystal mediated realignment. The chiral plasmonic optical activity of the AgNWs-CNCs composite films can be tuned by changing the interparticle electrostatic repulsion between the CNCs nanorods and AgNWs. We also observe an electromagnetic energy transfer phenomena among the plasmonic bands of AgNWs, due to the modulation of the photonic band gap of the CNCs host matrix. This facile approach for fabricating chiral macrostructured plasmonic materials with optically tunable property is of interest for a variety of advanced optics applications.

Highly tunable magnetism in silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain

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

Zheng, Rui; Ni, Jun, E-mail: junni@mail.tsinghua.edu.cn; Collaborative Innovative Center of Quantum Matter, Beijing 100084

2015-12-28

We have investigated the magnetic properties of silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain by the first-principles calculations. We find that Cr and Fe doped silicenes show strain-tunable magnetism. (1) The magnetism of Cr and Fe doped silicenes exhibits sharp transitions from low spin states to high spin states by a small isotropic tensile strain. Specially for Fe doped silicene, a nearly nonmagnetic state changes to a high magnetic state by a small isotropic tensile strain. (2) The magnetic moments of Fe doped silicene also show a sharp jump to ∼2 μ{sub B} at amore » small threshold of the uniaxial strain, and the magnetic moments of Cr doped silicene increase gradually to ∼4 μ{sub B} with the increase of uniaxial strain. (3) The electronic and magnetic properties of Cr and Fe doped silicenes are sensitive to the magnitude and direction of the external strain. The highly tunable magnetism may be applied in the spintronic devices.« less

Tunable two-dimensional interfacial coupling in molecular heterostructures

DOE PAGES

Xu, Beibei; Chakraborty, Himanshu; Yadav, Vivek K.; ...

2017-08-22

Two-dimensional van der Waals heterostructures are of considerable interest for the next generation nanoelectronics because of their unique interlayer coupling and optoelectronic properties. Here, we report a modified Langmuir–Blodgett method to organize twodimensional molecular charge transfer crystals into arbitrarily and vertically stacked heterostructures, consisting of bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF)/C 60 and poly (3-dodecylthiophene-2,5-diyl) (P3DDT)/C 60 nanosheets. A strong and anisotropic interfacial coupling between the charge transfer pairs is demonstrated. The van der Waals heterostructures exhibit pressure dependent sensitivity with a high piezoresistance coefficient of -4.4 × 10 -6 Pa -1, and conductance and capacitance tunable by external stimuli (ferroelectric field and magneticmore » field). Density functional theory calculations confirm charge transfer between the n-orbitals of the S atoms in BEDT–TTF of the BEDT–TTF/C 60 layer and the π* orbitals of C atoms in C 60 of the P3DDT/C 60 layer contribute to the inter-complex CT. Thus, the two-dimensional molecular van der Waals heterostructures with tunable optical–electronic–magnetic coupling properties are promising for flexible electronic applications.« less

Electrodeposited silk coatings for functionalized implant applications

NASA Astrophysics Data System (ADS)

Elia, Roberto

The mechanical and morphological properties of titanium as well as its biocompatibility and osteoinductive characteristics have made it the material of choice for dental implant systems. Although the success rate of titanium implants exceeds 90% in healthy individuals, a large subset of the population has one or more risk factors that inhibit implant integration. Treatments and coatings have been developed to improve clinical outcomes via introduction of appropriate surface topography, texture and roughness or incorporation of bioactive molecules. It is essential that the coatings and associated deposition techniques are controllable and reproducible. Currently, methods of depositing functional coatings are dictated by numerous parameters (temperature, particle size distribution, pH and voltage), which result in variable coating thickness, strength, porosity and weight, and hinder or preclude biomolecule incorporation. Silk is a highly versatile protein with a unique combination of mechanical and physical properties, including tunable degradation, biocompatibility, drug stabilizing capabilities and mechanical properties. Most recently an electrogelation technique was developed which allows for the deposition of gels which dry seamlessly over the contoured topography of the conductive substrate. In this work we examine the potential use of silk electrogels as mechanically robust implant coatings capable of sequestering and releasing therapeutic agents. Electrodeposition of silk electrogels formed in uniform electric fields was characterized with respect to field intensity and deposition time. Gel formation kinetics were used to derive functions which allowed for the prediction of coating deposition over a range of process and solution parameters. Silk electrogel growth orientation was shown to be influenced by the applied electric field. Coatings were reproducible and tunable via intrinsic silk solution properties and extrinsic process parameters. Adhesion was modulated over a 10-fold range and implant insertion into bone mimics demonstrated that the coatings were able to withstand delamination forces experienced during these mock implantations. Antibiotic release from coated implant studs inhibited bacterial growth and dexamethasone release was shown to stimulate calcium deposition in mesenchymal stem cells.

Optical and Acoustic Device Applications of Ferroelastic Crystals

NASA Astrophysics Data System (ADS)

Meeks, Steven Wayne

This dissertation presents the discovery of a means of creating uniformly periodic domain gratings in a ferroelastic crystal of neodymium pentaphosphate (NPP). The uniform and non-uniform domain structures which can be created in NPP have the potential applications as tunable active gratings for lasers, tunable diffraction gratings, tunable Bragg reflection gratings, tunable acoustic filters, optical modulators, and optical domain wall memories. The interaction of optical and acoustic waves with ferroelastic domain walls in NPP is presented in detail. Acoustic amplitude reflection coefficients from a single domain wall in NPP are much larger than other ferroelastic-ferroelectrics such as gadolinium molybdate (GMO). Domain walls of NPP are used to make two demonstration acoustic devices: a tunable comb filter and a tunable delay line. The tuning process is accomplished by moving the position of the reflecting surface (the domain wall). A theory of the reflection of optical waves from NPP domain walls is discussed. The optical reflection is due to a change in the polarization of the wave, and not a change in the index, as the wave crosses the domain wall. Theoretical optical power reflection coefficients show good agreement with the experimentally measured values. The largest optical reflection coefficient of a single domain wall is at a critical angle and is 2.2% per domain wall. Techniques of injecting periodic and aperiodic domain walls into NPP are presented. The nucleation process of the uniformly periodic domain gratings in NPP is described in terms of a newly-discovered domain structure, namely the ferroelastic bubble. A ferroelastic bubble is the elastic analogue to the well-known magnetic bubble. The period of the uniformly periodic domain grating is tunable from 100 to 0.5 microns and the grating period may be tuned relatively rapidly. The Bragg efficiency of these tunable gratings is 77% for an uncoated crystal. Several demonstration devices which use these periodic structures are discussed. These devices are a tunable active grating laser (TAG laser), a tunable active grating (TAG), and a tunable acoustic bulk wave filter.

Tunable coating of gold nanostars: tailoring robust SERS labels for cell imaging

NASA Astrophysics Data System (ADS)

Bassi, B.; Taglietti, A.; Galinetto, P.; Marchesi, N.; Pascale, A.; Cabrini, E.; Pallavicini, P.; Dacarro, G.

2016-07-01

Surface modification of noble metal nanoparticles with mixed molecular monolayers is one of the most powerful tools in nanotechnology, and is used to impart and tune new complex surface properties. In imaging techniques based on surface enhanced Raman spectroscopy (SERS), precise and controllable surface modifications are needed to carefully design reproducible, robust and adjustable SERS nanoprobes. We report here the attainment of SERS labels based on gold nanostars (GNSs) coated with a mixed monolayer composed of a poly ethylene glycol (PEG) thiol (neutral or negatively charged) that ensure stability in biological environments, and of a signalling unit 7-Mercapto-4-methylcoumarin as a Raman reporter molecule. The composition of the coating mixture is precisely controlled using an original method, allowing the modulation of the SERS intensity and ensuring overall nanoprobe stability. The further addition of a positively charged layer of poly (allylamine hydrocloride) on the surface of negatively charged SERS labels does not change the SERS response, but it promotes the penetration of GNSs in SH-SY5Y neuroblastoma cells. As an example of an application of such an approach, we demonstrate here the internalization of these new labels by means of visualization of cell morphology obtained with SERS mapping.

Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors

PubMed Central

Khosroabadi, Akram A.; Gangopadhyay, Palash; Hernandez, Steven; Kim, Kyungjo; Peyghambarian, Nasser; Norwood, Robert A.

2015-01-01

We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material. PMID:28793489

Identification of the optimal spectral region for plasmonic and nanoplasmonic sensing.

PubMed

Otte, Marinus A; Sepúlveda, Borja; Ni, Weihai; Juste, Jorge Pérez; Liz-Marzán, Luis M; Lechuga, Laura M

2010-01-26

We present a theoretical and experimental study involving the sensing characteristics of wavelength-interrogated plasmonic sensors based on surface plasmon polaritons (SPP) in planar gold films and on localized surface plasmon resonances (LSPR) of single gold nanorods. The tunability of both sensing platforms allowed us to analyze their bulk and surface sensing characteristics as a function of the plasmon resonance position. We demonstrate that a general figure of merit (FOM), which is equivalent in wavelength and energy scales, can be employed to mutually compare both sensing schemes. Most interestingly, this FOM has revealed a spectral region for which the surface sensitivity performance of both sensor types is optimized, which we attribute to the intrinsic dielectric properties of plasmonic materials. Additionally, in good agreement with theoretical predictions, we experimentally demonstrate that, although the SPP sensor offers a much better bulk sensitivity, the LSPR sensor shows an approximately 15% better performance for surface sensitivity measurements when its FOM is optimized. However, optimization of the substrate refractive index and the accessibility of the relevant molecules to the nanoparticles can lead to a total 3-fold improvement of the FOM in LSPR sensors.

Wrinkled, wavelength-tunable graphene-based surface topographies for directing cell alignment and morphology

PubMed Central

Wang, Zhongying; Tonderys, Daniel; Leggett, Susan E.; Williams, Evelyn Kendall; Kiani, Mehrdad T.; Steinberg, Ruben Spitz; Qiu, Yang; Wong, Ian Y.; Hurt, Robert H.

2015-01-01

Textured surfaces with periodic topographical features and long-range order are highly attractive for directing cell-material interactions. They mimic physiological environments more accurately than planar surfaces and can fundamentally alter cell alignment, shape, gene expression, and cellular assembly into superstructures or microtissues. Here we demonstrate for the first time that wrinkled graphene-based surfaces are suitable as textured cell attachment substrates, and that engineered wrinkling can dramatically alter cell alignment and morphology. The wrinkled surfaces are fabricated by graphene oxide wet deposition onto pre-stretched elastomers followed by relaxation and mild thermal treatment to stabilize the films in cell culture medium. Multilayer graphene oxide films form periodic, delaminated buckle textures whose wavelengths and amplitudes can be systematically tuned by variation in the wet deposition process. Human and murine fibroblasts attach to these textured films and remain viable, while developing pronounced alignment and elongation relative to those on planar graphene controls. Compared to lithographic patterning of nanogratings, this method has advantages in the simplicity and scalability of fabrication, as well as the opportunity to couple the use of topographic cues with the unique conductive, adsorptive, or barrier properties of graphene materials for functional biomedical devices. PMID:25848137