Electrochemical sensing of sulphur dioxide: a comparison using dodecanethiol and citrate capped gold nanoclusters.

PubMed

Sathe, Bhaskar R; Risbud, Mandar S; Mulla, Imtiaz S; Pillai, Vijayamohanan K

2008-06-01

A comparison of cyclic voltammograms of dodecanethiol (DDT) capped Au nanoclusters (5.0 0.5 nm) and trisodium citrate (Cit) capped Au nanoclusters (approximately 10-15 nm) modified glassy carbon electrode shows a dramatic variation in the current when exposed to a small amount of sulphur dioxide. This is explained using the electrocatalytic properties of Au nanoclusters towards the oxidation of SO2, thus facilitating the fabrication of electrochemical sensors for the detection of SO2. The intrinsic redox changes observed for gold nanocluster-modified glassy carbon electrodes disappear on passing SO2, despite a dramatic current increase, which indeed scales up with the amount of dissolved SO2. Interestingly, a complete rejuvenation of the redox behavior of gold is also observed on subsequent removal of SO2 from the solution by passing pure nitrogen for 15 minutes. Further, these nanoclusters when characterized with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) after SO2 passage reveal a variety of SO2 adsorption modes on gold surface. XP spectra also show a shift of 1.03 eV towards higher binding energy indicating a strong adsorption of SO2 gas, while FTIR gives conclusive evidence for the interaction of SO2 with gold nanoparticles.

Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

DOE PAGES

Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; ...

2016-03-08

The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities comparedmore » to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.« less

Method for making thin carbon foam electrodes

DOEpatents

Pekala, Richard W.; Mayer, Steven T.; Kaschmitter, James L.; Morrison, Robert L.

1999-01-01

A method for fabricating thin, flat carbon electrodes by infiltrating highly porous carbon papers, membranes, felts, metal fibers/powders, or fabrics with an appropriate carbon foam precursor material. The infiltrated carbon paper, for example, is then cured to form a gel-saturated carbon paper, which is subsequently dried and pyrolyzed to form a thin sheet of porous carbon. The material readily stays flat and flexible during curing and pyrolyzing to form thin sheets. Precursor materials include polyacrylonitrile (PAN), polymethylacrylonitrile (PMAN), resorcinol/formaldehyde, catechol/formaldehyde, phenol/formaldehyde, etc., or mixtures thereof. These thin films are ideal for use as high power and energy electrodes in batteries, capacitors, and fuel cells, and are potentially useful for capacitive deionization, filtration and catalysis.

Biomimetic Mineralization of Gold Nanoclusters as Multifunctional Thin Films for Glass Nanopore Modification, Characterization, and Sensing.

PubMed

Cao, Sumei; Ding, Shushu; Liu, Yingzi; Zhu, Anwei; Shi, Guoyue

2017-08-01

Hurdles of nanopore modification and characterization restrain the development of glass capillary-based nanopore sensing platforms. In this article, a simple but effective biomimetic mineralization method was developed to decorate glass nanopore with a thin film of bovine serum albumin-protected Au nanocluster (BSA-Au NC). The BSA-Au NC film emitted a strong red fluorescence whereby nondestructive characterization of Au film decorated at the inner surface of glass nanopore can be facilely achieved by a fluorescence microscopy. Besides, the BSA molecules played dual roles in the fabrication of functionalized Au thin film in glass nanopore: they not only directed the synthesis of fluorescent Au thin film but also provided binding sites for recognition, thus achieving synthesis-modification integration. This occurred due to the ionized carboxyl groups (-COO - ) of a BSA coating layer on Au NCs which can interacted with arginine (Arg) via guanidinium groups. The added Arg selectively led to the change in the charge and ionic current of BSA-Au NC film-decorated glass nanopore. Such ionic current responses can be used for quantifying Arg with a detection limit down to 1 fM, which was more sensitive than that of previous sensing systems. Together, the designed method exhibited great promise in providing a facile and controllable solution for glass nanopore modification, characterization, and sensing.

Method for making thin carbon foam electrodes

DOEpatents

Pekala, R.W.; Mayer, S.T.; Kaschmitter, J.L.; Morrison, R.L.

1999-08-03

A method for fabricating thin, flat carbon electrodes by infiltrating highly porous carbon papers, membranes, felts, metal fibers/powders, or fabrics with an appropriate carbon foam precursor material is disclosed. The infiltrated carbon paper, for example, is then cured to form a gel-saturated carbon paper, which is subsequently dried and pyrolyzed to form a thin sheet of porous carbon. The material readily stays flat and flexible during curing and pyrolyzing to form thin sheets. Precursor materials include polyacrylonitrile (PAN), polymethylacrylonitrile (PMAN), resorcinol/formaldehyde, catechol/formaldehyde, phenol/formaldehyde, etc., or mixtures thereof. These thin films are ideal for use as high power and energy electrodes in batteries, capacitors, and fuel cells, and are potentially useful for capacitive deionization, filtration and catalysis.

Tailoring magnetic properties of Co nanocluster assembled films using hydrogen

NASA Astrophysics Data System (ADS)

Romero, C. P.; Volodin, A.; Paddubrouskaya, H.; Van Bael, M. J.; Van Haesendonck, C.; Lievens, P.

2018-07-01

Tailoring magnetic properties in nanocluster assembled cobalt (Co) thin films was achieved by admitting a small percentage of H2 gas (∼2%) into the Co gas phase cluster formation chamber prior to deposition. The oxygen content in the films is considerably reduced by the presence of hydrogen during the cluster formation, leading to enhanced magnetic interactions between clusters. Two sets of Co samples were fabricated, one without hydrogen gas and one with hydrogen gas. Magnetic properties of the non-hydrogenated and the hydrogen-treated Co nanocluster assembled films are comparatively studied using magnetic force microscopy and vibrating sample magnetometry. When comparing the two sets of samples the considerably larger coercive field of the H2-treated Co nanocluster film and the extended micrometer-sized magnetic domain structure confirm the enhancement of magnetic interactions between clusters. The thickness of the antiferromagnetic CoO layer is controlled with this procedure and modifies the exchange bias effect in these films. The exchange bias shift is lower for the H2-treated Co nanocluster film, which indicates that a thinner antiferromagnetic CoO reduces the coupling with the ferromagnetic Co. The hydrogen-treatment method can be used to tailor the oxidation levels thus controlling the magnetic properties of ferromagnetic cluster-assembled films.

High-rate synthesis of phosphine-stabilized undecagold nanoclusters using a multilayered micromixer.

PubMed

Jin, Hyung Dae; Garrison, Anna; Tseng, T; Paul, Brian K; Chang, Chih-Hung

2010-11-05

Growth in the potential applications of nanomaterials has led to a focus on the development of new manufacturing approaches for these materials. In particular, an increased demand due to the unique properties of nanomaterials requires a substantial yield of high-performance materials and a simultaneous reduction in the environmental impact of these processes. In this paper, a high-rate production of phosphine-stabilized undecagold nanoclusters was achieved using a layer-up strategy which involves the use of microlamination architectures; the patterning and bonding of thin layers of material (laminae) to create a multilayered micromixer in the range of 25-250 µm thick was used to step up the production of phosphine-stabilized undecagold nanoclusters. The continuous production of highly monodispersed phosphine-stabilized undecagold nanoclusters at a rate of about 11.8 (mg s(-1)) was achieved using a microreactor with a size of 1.687 cm(3). This result is about 500 times over conventional batch syntheses based on the production rate per reactor volume.

High-rate synthesis of phosphine-stabilized undecagold nanoclusters using a multilayered micromixer

NASA Astrophysics Data System (ADS)

Jin, Hyung Dae; Garrison, Anna; Tseng, T.; Paul, Brian K.; Chang, Chih-Hung

2010-11-01

Growth in the potential applications of nanomaterials has led to a focus on the development of new manufacturing approaches for these materials. In particular, an increased demand due to the unique properties of nanomaterials requires a substantial yield of high-performance materials and a simultaneous reduction in the environmental impact of these processes. In this paper, a high-rate production of phosphine-stabilized undecagold nanoclusters was achieved using a layer-up strategy which involves the use of microlamination architectures; the patterning and bonding of thin layers of material (laminae) to create a multilayered micromixer in the range of 25-250 µm thick was used to step up the production of phosphine-stabilized undecagold nanoclusters. The continuous production of highly monodispersed phosphine-stabilized undecagold nanoclusters at a rate of about 11.8 (mg s - 1) was achieved using a microreactor with a size of 1.687 cm3. This result is about 500 times over conventional batch syntheses based on the production rate per reactor volume.

Theoretical Studies of Nanocluster Formation

DTIC Science & Technology

2016-05-26

background, technical approach 2. Core-shell nanoclusters (Mg/Cu, Si/Al, etc.) - energetic additives for propellants , explosives - gas generators...shell nanocluster synthesis Core-shell nanoclusters such as SiAln, NinAlm, Aln(CuO)m, etc. may be useful ingredients in propellants and explosives

Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

PubMed

Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

2017-02-10

In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

PubMed Central

Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

2017-01-01

In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)-capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters. PMID:28208642

Non-covalent attachment of silver nanoclusters onto single-walled carbon nanotubes with human serum albumin as linking molecule

NASA Astrophysics Data System (ADS)

Rodríguez-Galván, Andrés; Heredia, Alejandro; Amelines-Sarria, Oscar; Rivera, Margarita; Medina, Luis A.; Basiuk, Vladimir A.

2015-03-01

The attachment of silver nanoclusters (AgNCs) onto single-walled carbon nanotubes (SWNTs) for the formation of integrated fluorescence sites has attracted much attention due their potential applications as biological probes and nanovectors in theragnosis. Here, we report the preparation through assembly of fluorescent quasi 1-D nanomaterial based on SWNTs and silver nanoclusters (AgNCs) non-covalently attached to human serum albumin as biological linker. The fluorescent SWNT-AgNCs-HSA conjugates were characterized by atomic force microscopy, high-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning TEM (HAADF-STEM), fluorescent and UV-vis spectroscopy. The above techniques confirmed that AgNCs were non-covalently attached onto the external surface of SWNTs. In addition, it was observed that the modification did not affect the optical properties of the synthesized AgNCs since the absorption spectra and fluorescence under UV irradiation (λ = 365 nm) remain the same. The effect of the functionalized systems was tested on mammal red blood cells (RBCs) and it was found that their structural integrity was compromised by the conjugates, limiting their biological and medical applications.

Cadmium sulfide nanocluster-based electrochemical stripping detection of DNA hybridization.

PubMed

Zhu, Ningning; Zhang, Aiping; He, Pingang; Fang, Yuzhi

2003-03-01

A novel, sensitive electrochemical DNA hybridization detection assay, using cadmium sulfide (CdS) nanoclusters as the oligonucleotide labeling tag, is described. The assay relies on the hybridization of the target DNA with the CdS nanocluster oligonucleotide DNA probe, followed by the dissolution of the CdS nanoclusters anchored on the hybrids and the indirect determination of the dissolved cadmium ions by sensitive anodic stripping voltammetry (ASV) at a mercury-coated glassy carbon electrode (GCE). The results showed that only a complementary sequence could form a double-stranded dsDNA-CdS with the DNA probe and give an obvious electrochemical response. A three-base mismatch sequence and non-complementary sequence had negligible response. The combination of the large number of cadmium ions released from each dsDNA hybrid with the remarkable sensitivity of the electrochemical stripping analysis for cadmium at mercury-film GCE allows detection at levels as low as 0.2 pmol L(-1) of the complementary sequence of DNA.

Silver and copper nanoclusters in the lustre decoration of Italian Renaissance pottery: an EXAFS study

NASA Astrophysics Data System (ADS)

Padovani, S.; Borgia, I.; Brunetti, B.; Sgamellotti, A.; Giulivi, A.; D'Acapito, F.; Mazzoldi, P.; Sada, C.; Battaglin, G.

Lustre is one of the most important decorative techniques of the Medieval and Renaissance pottery of the Mediterranean basin, capable of producing brilliant metallic reflections and iridescence. Following the recent finding that the colour of lustre decorations is mainly determined by copper and silver nanoclusters dispersed in the glaze layer, the local environment of copper and silver atoms has been studied by extended X-ray absorption fine structure (EXAFS) spectroscopy on original samples of gold and red lustre. It has been found that, in gold lustre, whose colour is attributed mainly to the silver nanocluster dispersion, silver is only partially present in the metallic form and copper is almost completely oxidised. In the red lustre, whose colour is attributed mainly to the copper nanocluster dispersion, only a fraction of copper is present in the metallic form. EXAFS measurements on red lustre, carried out in the total electron yield mode to probe only the first 150 nm of the glaze layer, indicated that in some cases lustre nanoclusters may be confined in a very thin layer close to the surface.

Mesoporous Li4Ti5O12 nanoclusters anchored on super-aligned carbon nanotubes as high performance electrodes for lithium ion batteries.

PubMed

Sun, Li; Kong, Weibang; Wu, Hengcai; Wu, Yang; Wang, Datao; Zhao, Fei; Jiang, Kaili; Li, Qunqing; Wang, Jiaping; Fan, Shoushan

2016-01-07

Mesoporous lithium titanate (LTO) nanoclusters are in situ synthesized in a network of super aligned carbon nanotubes (SACNTs) via a solution-based method followed by heat treatment in air. In the LTO-CNT composite, SACNTs not only serve as the skeleton to support a binder-free electrode, but also render the composite with high conductivity, flexibility, and mechanical strength. The homogeneously dispersed LTO nanoclusters among the SACNTs allow each LTO grain to effectively access the electrolyte and the conductive network, benefiting both ion and electron transport. By the incorporation of LTO into the CNT network, mechanical reinforcement is also achieved. When serving as a negative electrode for lithium ion batteries, such a robust composite-network architecture provides the electrodes with effective charge transport and structural integrity, leading to high-performance flexible electrodes with high capacity, high rate capability, and excellent cycling stability.

Carbon Nanotube Thin-Film Antennas.

PubMed

Puchades, Ivan; Rossi, Jamie E; Cress, Cory D; Naglich, Eric; Landi, Brian J

2016-08-17

Multiwalled carbon nanotube (MWCNT) and single-walled carbon nanotube (SWCNT) dipole antennas have been successfully designed, fabricated, and tested. Antennas of varying lengths were fabricated using flexible bulk MWCNT sheet material and evaluated to confirm the validity of a full-wave antenna design equation. The ∼20× improvement in electrical conductivity provided by chemically doped SWCNT thin films over MWCNT sheets presents an opportunity for the fabrication of thin-film antennas, leading to potentially simplified system integration and optical transparency. The resonance characteristics of a fabricated chlorosulfonic acid-doped SWCNT thin-film antenna demonstrate the feasibility of the technology and indicate that when the sheet resistance of the thin film is >40 ohm/sq no power is absorbed by the antenna and that a sheet resistance of <10 ohm/sq is needed to achieve a 10 dB return loss in the unbalanced antenna. The dependence of the return loss performance on the SWCNT sheet resistance is consistent with unbalanced metal, metal oxide, and other CNT-based thin-film antennas, and it provides a framework for which other thin-film antennas can be designed.

Electron Damage Effects on Carbon Nanotube Thin Films

DTIC Science & Technology

2013-03-01

ELECTRON DAMAGE EFFECTS ON CARBON NANOTUBE THIN FILMS THESIS Jeremy S. Best, Captain, USMC AFIT-ENP-13-M-37 DEPARTMENT OF THE AIR FORCE AIR...Government and is not subject to copyright protection in the United States. AFIT-ENP-13-M-37 ELECTRON DAMAGE EFFECTS ON CARBON NANOTUBE THIN FILMS...M-37 ELECTRON DAMAGE EFFECTS ON CARBON NANOTUBE THIN FILMS Jeremy S. Best, BS Aerospace Engineering Captain, USMC Approved: Dr. John McClory

Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins.

PubMed

Rodríguez, Henry A; Giraldo, Luis F; Casanova, Herley

2015-07-01

The aim of this work was to study the effect of silica nanoclusters (SiNC), obtained by a solvent evaporation method and functionalized by 3-methacryloxypropyltrimethoxysilane (MPS) and MPS+octyltrimethoxysilane (OTMS) (50/50wt/wt), on the rheological, mechanical and sorption properties of urethane dimethylacrylate (UDMA)/triethylenglycol dimethacrylate (TEGDMA) (80/20wt/wt) resins blend. Silica nanoparticles (SiNP) were silanized with MPS or MPS+OTMS (50/50wt/wt) and incorporated in an UDMA-isopropanol mix to produce functionalized silica nanoclusters after evaporating the isopropanol. The effect of functionalized SiNC on resins rheological properties was determined by large and small deformation tests. Mechanical, thermal, sorption and solubility properties were evaluated for composite materials. The UDMA/TEGDMA (80/20wt/wt) resins blend with added SiNC (ca. 350nm) and functionalized with MPS showed a Newtonian flow behavior associated to their spheroidal shape, whereas the resins blend with nanoclusters silanized with MPS+OTMS (50/50wt/wt) (ca. 400nm) showed a shear-thinning behavior due to nanoclusters irregular shape. Composite materials prepared with bare silica nanoclusters showed lower compressive strength than functionalized silica nanoclusters. MPS functionalized nanoclusters showed better mechanical properties but higher water sorption than functionalized nanoclusters with both silane coupling agents, MPS and OTMS. The solvent evaporation method applied to functionalized nanoparticles showed to be an alternative way to the sinterization method for producing nanoclusters, which improved some dental composite mechanical properties and reduced water sorption. The shape of functionalized silica nanoclusters showed to have influence on the rheological properties of SiNC resin suspensions and the mechanical and sorption properties of light cured composites. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Synthesis and characterization of colloidal fluorescent silver nanoclusters.

PubMed

Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

2012-06-19

Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

Tandem Nitrogen Functionalization of Porous Carbon: Toward Immobilizing Highly Active Palladium Nanoclusters for Dehydrogenation of Formic Acid

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

Li, Zhangpeng; Yang, Xinchun; Tsumori, Nobuko

2017-03-10

Highly dispersed palladium nanoclusters (Pd NCs) immobilized by a nitrogen (N)-functionalized porous carbon support (N-MSC-30) are synthesized by a wet chemical reduction method, wherein the N-MSC-30 prepared by a tandem low temperature heat-treatment approach proved to be a distinct support for stabilizing the Pd NCs. The prepared Pd/N-MSC-30 shows extremely high catalytic activity and recyclability for the dehydrogenation of formic acid (FA), affording the highest turnover frequency (TOF = 8414 h -1) at 333 K, which is much higher than that of the Pd catalyst supported on the N-MSC-30 prepared via a one-step process. This tandem heat treatment strategy providesmore » a facile and effective synthetic methodology to immobilize ultrafine metal NPs on N-functionalized carbon materials, which have tremendous application prospects in various catalytic fields.« less

Surface mediated assembly of small, metastable gold nanoclusters

NASA Astrophysics Data System (ADS)

Pettibone, John M.; Osborn, William A.; Rykaczewski, Konrad; Talin, A. Alec; Bonevich, John E.; Hudgens, Jeffrey W.; Allendorf, Mark D.

2013-06-01

The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The

Chiral Gold Nanoclusters: Atomic Level Origins of Chirality.

PubMed

Zeng, Chenjie; Jin, Rongchao

2017-08-04

Chiral nanomaterials have received wide interest in many areas, but the exact origin of chirality at the atomic level remains elusive in many cases. With recent significant progress in atomically precise gold nanoclusters (e.g., thiolate-protected Au n (SR) m ), several origins of chirality have been unveiled based upon atomic structures determined by using single-crystal X-ray crystallography. The reported chiral Au n (SR) m structures explicitly reveal a predominant origin of chirality that arises from the Au-S chiral patterns at the metal-ligand interface, as opposed to the chiral arrangement of metal atoms in the inner core (i.e. kernel). In addition, chirality can also be introduced by a chiral ligand, manifested in the circular dichroism response from metal-based electronic transitions other than the ligand's own transition(s). Lastly, the chiral arrangement of carbon tails of the ligands has also been discovered in a very recent work on chiral Au 133 (SR) 52 and Au 246 (SR) 80 nanoclusters. Overall, the origins of chirality discovered in Au n (SR) m nanoclusters may provide models for the understanding of chirality origins in other types of nanomaterials and also constitute the basis for the development of various applications of chiral nanoparticles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface mediated assembly of small, metastable gold nanoclusters.

PubMed

Pettibone, John M; Osborn, William A; Rykaczewski, Konrad; Talin, A Alec; Bonevich, John E; Hudgens, Jeffrey W; Allendorf, Mark D

2013-07-21

The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.

Plasmon transmutation: inducing new modes in nanoclusters by adding dielectric nanoparticles.

PubMed

Wen, Fangfang; Ye, Jian; Liu, Na; Van Dorpe, Pol; Nordlander, Peter; Halas, Naomi J

2012-09-12

Planar clusters of coupled plasmonic nanoparticles support nanoscale electromagnetic "hot spots" and coherent effects, such as Fano resonances, with unique near and far field signatures, currently of prime interest for sensing applications. Here we show that plasmonic cluster properties can be substantially modified by the addition of individual, discrete dielectric nanoparticles at specific locations on the cluster, introducing new plasmon modes, or transmuting existing plasmon modes to new ones, in the resulting metallodielectric nanocomplex. Depositing a single carbon nanoparticle in the junction between a pair of adjacent nanodisks induces a metal-dielectric-metal quadrupolar plasmon mode. In a ten-membered cluster, placement of several carbon nanoparticles in junctions between multiple adjacent nanoparticles introduces a collective magnetic plasmon mode into the Fano dip, giving rise to an additional subradiant mode in the metallodielectric nanocluster response. These examples illustrate that adding dielectric nanoparticles to metallic nanoclusters expands the number and types of plasmon modes supported by these new mixed-media nanoscale assemblies.

Quantum sized gold nanoclusters with atomic precision.

PubMed

Qian, Huifeng; Zhu, Manzhou; Wu, Zhikun; Jin, Rongchao

2012-09-18

Gold nanoparticles typically have a metallic core, and the electronic conduction band consists of quasicontinuous energy levels (i.e. spacing δ ≪ k(B)T, where k(B)T is the thermal energy at temperature T (typically room temperature) and k(B) is the Boltzmann constant). Electrons in the conduction band roam throughout the metal core, and light can collectively excite these electrons to give rise to plasmonic responses. This plasmon resonance accounts for the beautiful ruby-red color of colloidal gold first observed by Faraday back in 1857. On the other hand, when gold nanoparticles become extremely small (<2 nm in diameter), significant quantization occurs to the conduction band. These quantum-sized nanoparticles constitute a new class of nanomaterial and have received much attention in recent years. To differentiate quantum-sized nanoparticles from conventional plasmonic gold nanoparticles, researchers often refer to the ultrasmall nanoparticles as nanoclusters. In this Account, we chose several typical sizes of gold nanoclusters, including Au(25)(SR)(18), Au(38)(SR)(24), Au(102)(SR)(44), and Au(144)(SR)(60), to illustrate the novel properties of metal nanoclusters imparted by quantum size effects. In the nanocluster size regime, many of the physical and chemical properties of gold nanoparticles are fundamentally altered. Gold nanoclusters have discrete electronic energy levels as opposed to the continuous band in plasmonic nanoparticles. Quantum-sized nanoparticles also show multiple optical absorption peaks in the optical spectrum versus a single surface plasmon resonance (SPR) peak at 520 nm for spherical gold nanocrystals. Although larger nanocrystals show an fcc structure, nanoclusters often have non-fcc atomic packing structures. Nanoclusters also have unique fluorescent, chiral, and magnetic properties. Due to the strong quantum confinement effect, adding or removing one gold atom significantly changes the structure and the electronic and optical

The construction of glucose biosensor based on platinum nanoclusters-multiwalled carbon nanotubes nanocomposites.

PubMed

Wang, Cheng Yan; Tan, Xing Rong; Chen, Shi Hong; Hu, Fang Xin; Zhong, Hua An; Zhang, Yu

2012-02-01

One-step synthesis method was proposed to obtain the nanocomposites of platinum nanoclusters and multiwalled carbon nanotubes (PtNCs-MWNTs), which were used as a novel immobilization matrix for the enzyme to fabricate glucose biosensor. The fabrication process of the biosensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and scanning electron microscope. Due to the favorable characteristic of PtNCs-MWNTs nanocomposites, the biosensor exhibited good characteristics, such as wide linear range (3.0 μM-12.1 mM), low detection limit (1.0 μM), high sensitivity (12.8 μA mM⁻¹), rapid response time (within 6 s). The apparent Michaelis-Menten constant (K(app)(m)) is 2.1 mM. The performance of the resulting biosensor is more prominent than that of most of the reported glucose biosensors. Furthermore, it was demonstrated that this biosensor can be used for the assay of glucose in human serum samples.

A highly efficient nano-cluster artificial peroxidase and its direct electrochemistry on a nano complex modified glassy carbon electrode.

PubMed

Hong, Jun; Wang, Wei; Huang, Kun; Yang, Wei-Yun; Zhao, Ying-Xue; Xiao, Bao-Lin; Gao, Yun-Fei; Moosavi-Movahedi, Zainab; Ghourchian, Hedayatollah; Moosavi-Movahedi, Ali Akbar

2012-01-01

A nano-cluster with highly efficient peroxide activity was constructed based on nafion (NF) and cytochrome c (Cyt c). UV-Vis spectrometry and transmission electron microscopy (TEM) methods were utilized for characterization of the nano-structured enzyme or artificial peroxidase (AP). The nano-cluster was composed of a Chain-Ball structure, with an average ball size of about 40 nm. The Michaelis-Menten (K(m)) and catalytic rate (k(cat)) constants of the AP were determined to be 2.5 ± 0.4 µM and 0.069 ± 0.001 s(-1), respectively, in 50 mM PBS at pH 7.0. The catalytic efficiency of the AP was evaluated to be 0.028 ± 0.005 µM(-1) s(-1), which was 39 ± 5% as efficient as the native horseradish peroxidase (HRP). The AP was also immobilized on a functional multi-wall carbon nanotube (MWNCTs)-gold colloid nanoparticles (AuNPs) nano-complex modified glassy carbon (GC) electrode. The cyclic voltammetry of AP on the nano complex modified GC electrode showed a pair of well-defined redox peaks with a formal potential (E°') of -45 ± 2 mV (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer rate constant (k(s)) was evaluated to be 0.65 s(-1). The surface concentration of electroactive AP on GC electrode (Γ) was 7 × 10(-10) mol cm(-2). The apparent Michaelis-Menten constant (K(m)(app)) was 0.23 nM.

Positron confinement in embedded lithium nanoclusters

NASA Astrophysics Data System (ADS)

van Huis, M. A.; van Veen, A.; Schut, H.; Falub, C. V.; Eijt, S. W.; Mijnarends, P. E.; Kuriplach, J.

2002-02-01

Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgO||Li interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

Atomically Precise Metal Nanoclusters for Catalytic Application

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

Jin, Rongchao

2016-11-18

The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily highmore » selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au 25(SR) 18, Au 28(SR) 20, Au 38(SR) 24, Au 99(SR) 42, Au 144(SR) 60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our works include: i) Effects of ligand, cluster charge state, and size on the catalytic

Matrix Sputtering Method: A Novel Physical Approach for Photoluminescent Noble Metal Nanoclusters.

PubMed

Ishida, Yohei; Corpuz, Ryan D; Yonezawa, Tetsu

2017-12-19

Noble metal nanoclusters are believed to be the transition between single metal atoms, which show distinct optical properties, and metal nanoparticles, which show characteristic plasmon absorbance. The interesting properties of these materials emerge when the particle size is well below 2 nm, such as photoluminescence, which has potential application particularly in biomedical fields. These photoluminescent ultrasmall nanoclusters are typically produced by chemical reduction, which limits their practical application because of the inherent toxicity of the reagents used in this method. Thus, alternative strategies are sought, particularly in terms of physical approaches, which are known as "greener alternatives," to produce high-purity materials at high yields. Thus, a new approach using the sputtering technique was developed. This method was initially used to produce thin films using solid substrates; now it can be applied even with liquid substrates such as ionic liquids or polyethylene glycol as long as these liquids have a low vapor pressure. This revolutionary development has opened up new areas of research, particularly for the synthesis of colloidal nanoparticles with dimensions below 10 nm. We are among the first to apply the sputtering technique to the physical synthesis of photoluminescent noble metal nanoclusters. Although typical sputtering systems have relied on the effect of surface composition and viscosity of the liquid matrix on controlling particle diameters, which only resulted in diameters ca. 3-10 nm, that were all plasmonic, our new approach introduced thiol molecules as stabilizers inspired from chemical methods. In the chemical syntheses of metal nanoparticles, controlling the concentration ratio between metal ions and stabilizing reagents is a possible means of systematic size control. However, it was not clear whether this would be applicable in a sputtering system. Our latest results showed that we were able to generically produce a

Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

PubMed Central

Zhang, Z. W.; Yao, L.; Wang, X.-L.; Miller, M. K.

2015-01-01

A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters. PMID:26023747

Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

DOE PAGES

Zhang, Z. W.; Yao, L.; Wang, X. -L.; ...

2015-05-29

A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using amore » combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.« less

Ultra-thin carbon-fiber paper fabrication and carbon-fiber distribution homogeneity evaluation method

NASA Astrophysics Data System (ADS)

Zhang, L. F.; Chen, D. Y.; Wang, Q.; Li, H.; Zhao, Z. G.

2018-01-01

A preparation technology of ultra-thin Carbon-fiber paper is reported. Carbon fiber distribution homogeneity has a great influence on the properties of ultra-thin Carbon-fiber paper. In this paper, a self-developed homogeneity analysis system is introduced to assist users to evaluate the distribution homogeneity of Carbon fiber among two or more two-value images of carbon-fiber paper. A relative-uniformity factor W/H is introduced. The experimental results show that the smaller the W/H factor, the higher uniformity of the distribution of Carbon fiber is. The new uniformity-evaluation method provides a practical and reliable tool for analyzing homogeneity of materials.

Unusual Structure and Magnetism in MnO Nanoclusters

NASA Astrophysics Data System (ADS)

Ganguly, Shreemoyee; Kabir, Mukul; Sanyal, Biplab; Mookerjee, Abhijit

2011-03-01

We report an unusual structural and magnetic evolution in stoichiometric MnO nanoclusters by an extensive and unbiased search through the potential energy surface within density functional theory. The (MnO)n nanoclusters adopt two-dimensional structures in size ranges in which Mnn nanoclusters are three-dimensional and regardless of the size of the nanocluster, the magnetic coupling is found to be antiferromagnetic, and is strikingly different from Mn-based molecular magnets. Both of these features are explained through the inherent electronic structures of the nanoclusters. We gratefully acknowledge financial support from Swedish Research Links program funded by VR/SIDA and Carl Tryggers Foundation, Sweden.

Fluorescent DNA-templated silver nanoclusters

NASA Astrophysics Data System (ADS)

Lin, Ruoqian

Because of the ultra-small size and biocompatibility of silver nanoclusters, they have attracted much research interest for their applications in biolabeling. Among the many ways of synthesizing silver nanoclusters, DNA templated method is particularly attractive---the high tunability of DNA sequences provides another degree of freedom for controlling the chemical and photophysical properties. However, systematic studies about how DNA sequences and concentrations are controlling the photophysical properties are still lacking. The aim of this thesis is to investigate the binding mechanisms of silver clusters binding and single stranded DNAs. Here in this thesis, we report synthesis and characterization of DNA-templated silver nanoclusters and provide a systematic interrogation of the effects of DNA concentrations and sequences, including lengths and secondary structures. We performed a series of syntheses utilizing five different sequences to explore the optimal synthesis condition. By characterizing samples with UV-vis and fluorescence spectroscopy, we achieved the most proper reactants ratio and synthesis conditions. Two of them were chosen for further concentration dependence studies and sequence dependence studies. We found that cytosine-rich sequences are more likely to produce silver nanoclusters with stronger fluorescence signals; however, sequences with hairpin secondary structures are more capable in stabilizing silver nanoclusters. In addition, the fluorescence peak emission intensities and wavelengths of the DNA templated silver clusters have sequence dependent fingerprints. This potentially can be applied to sequence sensing in the future. However all the current conclusions are not warranted; there is still difficulty in formulating general rules in DNA strand design and silver nanocluster production. Further investigation of more sequences could solve these questions in the future.

Development of High Resistive and High Magnetization Soft Thin Film and Fabrication of Thin Film Inductors

DTIC Science & Technology

2004-11-01

properties of Co- doped ZnO nanocluster films", .J. of Appl. Phys. in press, 2005 2. Presentations (contributed): Conference Contributions: 1) Y. Qiang...gigahertz band applications. The effects of substrates bias, sputter parameters, and seed-layer have thoroughly been investigated. The magnetic...Adequate properties of soft magnetic thin film were evaluated by an analytical calculation [1] to meet the requirement for gigahertz band thin-film

Experimental measurements of U60 nanocluster stability in aqueous solution

NASA Astrophysics Data System (ADS)

Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

2015-05-01

In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the

Electrostatic Interactions Positively Regulate K-Ras Nanocluster Formation and Function▿

PubMed Central

Plowman, Sarah J.; Ariotti, Nicholas; Goodall, Andrew; Parton, Robert G.; Hancock, John F.

2008-01-01

The organization of Ras proteins into plasma membrane nanoclusters is essential for high-fidelity signal transmission, but whether the nanoscale enviroments of different Ras nanoclusters regulate effector interactions is unknown. We show using high-resolution spatial mapping that Raf-1 is recruited to and retained in K-Ras-GTP nanoclusters. In contrast, Raf-1 recruited to the plasma membrane by H-Ras is not retained in H-Ras-GTP nanoclusters. Similarly, upon epidermal growth factor receptor activation, Raf-1 is preferentially recruited to K-Ras-GTP and not H-Ras-GTP nanoclusters. The formation of K-Ras-GTP nanoclusters is inhibited by phosphorylation of S181 in the C-terminal polybasic domain or enhanced by blocking S181 phosphorylation, with a concomitant reduction or increase in Raf-1 plasma membrane recruitment, respectively. Phosphorylation of S181 does not, however, regulate in vivo interactions with the nanocluster scaffold galectin-3 (Gal3), indicating separate roles for the polybasic domain and Gal3 in driving K-Ras nanocluster formation. Together, these data illustrate that Ras nanocluster composition regulates effector recruitment and highlight the importance of lipid/protein nanoscale environments to the activation of signaling cascades. PMID:18458061

Programmable Assembly of Hybrid Nanoclusters.

PubMed

Ni, Songbo; Wolf, Heiko; Isa, Lucio

2018-02-20

Hybrid nanoparticle clusters (often metallic) are interesting plasmonic materials with tunable resonances and a near-field electromagnetic enhancement at interparticle junctions. Therefore, in recent years, we have witnessed a surge in both the interest in these materials and the efforts to obtain them. However, a versatile fabrication of hybrid nanoclusters, that is, combining more than one material, still remains an open challenge. Current lithographical or self-assembly methods are limited to the preparation of hybrid clusters with up to two different materials and typically to the fabrication of hybrid dimers. Here, we provide a novel strategy to deposit and align not only hybrid dimers but also hybrid nanoclusters possessing more complex shapes and compositions. Our strategy is based on the downscaling of sequential capillarity-assisted particle assembly over topographical templates. As a proof of concept, we demonstrate dimers, linear trimers, and 2D nanoclusters with programmable compositions from a range of metallic nanoparticles. Our process does not rely on any specific chemistry and can be extended to a large variety of particles and shapes. The template also simultaneously aligns the hybrid (often anisotropic) nanoclusters, which could facilitate device integration, for example, for optical readout after transfer to other substrates by a printing step. We envisage that this new fabrication route will enable the assembly and positioning of complex hybrid nanoclusters of different functional nanoparticles to study coupling effects not only locally but also at larger scales for new nanoscale optical devices.

Nanoclustering as a dominant feature of plasma membrane organization.

PubMed

Garcia-Parajo, Maria F; Cambi, Alessandra; Torreno-Pina, Juan A; Thompson, Nancy; Jacobson, Ken

2014-12-01

Early studies have revealed that some mammalian plasma membrane proteins exist in small nanoclusters. The advent of super-resolution microscopy has corroborated and extended this picture, and led to the suggestion that many, if not most, membrane proteins are clustered at the plasma membrane at nanoscale lengths. In this Commentary, we present selected examples of glycosylphosphatidyl-anchored proteins, Ras family members and several immune receptors that provide evidence for nanoclustering. We advocate the view that nanoclustering is an important part of the hierarchical organization of proteins in the plasma membrane. According to this emerging picture, nanoclusters can be organized on the mesoscale to form microdomains that are capable of supporting cell adhesion, pathogen binding and immune cell-cell recognition amongst other functions. Yet, a number of outstanding issues concerning nanoclusters remain open, including the details of their molecular composition, biogenesis, size, stability, function and regulation. Notions about these details are put forth and suggestions are made about nanocluster function and why this general feature of protein nanoclustering appears to be so prevalent. © 2014. Published by The Company of Biologists Ltd.

Thin Coatings of Polymeric Carbon and Carbon Nanotubes for Corrosion Protection

DTIC Science & Technology

2009-02-01

Thin Coatings of Polymeric Carbon and Carbon Nanotubes for Corrosion Protection Zafar Iqbal Department of Chemistry and Environmental Science New...Department of Chemistry and Environmental Science ,Newark,NJ,07102 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND

Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

NASA Astrophysics Data System (ADS)

Ribis, J.; Bordas, E.; Trocellier, P.; Serruys, Y.; de Carlan, Y.; Legris, A.

2015-12-01

ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe-Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

Equilibrium Gold Nanoclusters Quenched with Biodegradable Polymers

PubMed Central

Murthy, Avinash K.; Stover, Robert J.; Borwankar, Ameya U.; Nie, Golay D.; Gourisankar, Sai; Truskett, Thomas M.; Sokolov, Konstantin V.; Johnston, Keith P.

2013-01-01

Although sub-100 nm nanoclusters of metal nanoparticles are of interest in many fields including biomedical imaging, sensors and catalysis, it has been challenging to control their morphologies and chemical properties. Herein, a new concept is presented to assemble equilibrium Au nanoclusters of controlled size by tuning the colloidal interactions with a polymeric stabilizer, PLA(1k)-b-PEG(10k)-b-PLA(1k). The nanoclusters form upon mixing a dispersion of ~5 nm Au nanospheres with a polymer solution followed by partial solvent evaporation. A weakly adsorbed polymer quenches the equilibrium nanocluster size and provides steric stabilization. Nanocluster size is tuned from ~20 nm to ~40 nm by experimentally varying the final Au nanoparticle concentration and the polymer/Au ratio, along with the charge on the initial Au nanoparticle surface. Upon biodegradation of the quencher, the nanoclusters reversibly and fully dissociate to individual ~5 nm primary particles. Equilibrium cluster size is predicted semi-quantitatively with a free energy model that balances short-ranged depletion and van der Waals attractions with longer-ranged electrostatic repulsion, as a function of the Au and polymer concentrations. The close spacings of the Au nanoparticles in the clusters produce strong NIR extinction over a broad range of wavelengths from 650 to 900 nm, which is of practical interest in biomedical imaging. PMID:23230905

Structural, electronic and vibrational properties of GexCy (x+y=2-5) nanoclusters: A B3LYP-DFT study

NASA Astrophysics Data System (ADS)

Goswami, Sohini; Saha, Sushmita; Yadav, R. K.

2015-11-01

An ab-initio study of the stability, structural and electronic properties has been made for 84 germanium carbide nanoclusters, GexCy (x+y=2-5). The configuration possessing the maximum value of final binding energy (FBE), among the various configurations corresponding to a fixed x+y=n value, is named as the most stable structure. The vibrational and optical properties have been investigated only for the most stable structures. A B3LYP-DFT/6-311G(3df) method has been employed to optimize fully the geometries of the nanoclusters. The binding energies (BE), highest-occupied and lowest-unoccupied molecular orbital (HOMO-LUMO) gaps have been obtained for all the clusters and the bond lengths have been reported for the most stable clusters. We have considered the zero point energy (ZPE) corrections. The adiabatic and vertical ionization potentials (IPs) and electron affinities (EAs), charge on atoms, dipole moments, vibrational frequencies, infrared intensities (IR Int.), relative infrared intensities (Rel. IR Int.) and Raman scattering activities have also been investigated for the most stable structures. The configurations containing the carbon atoms in majority are seen to be the most stable structures. The strong C-C bond has important role in stabilizing the clusters. For the clusters containing one germanium atom and all the other as carbon atoms, the BE increases monotonically with the number of the carbon atoms. The HOMO-LUMO gap, IPs and EAs fluctuates with increase in the number of atoms. The nanoclusters containing even number of carbon atoms have large HOMO-LUMO gaps and IPs, whereas the nanoclusters containing even number of carbon atoms have small EAs. In general, the adiabatic IP (EA) is smaller (greater) than the vertical IP (EA). The optical absorption spectrum or electron energy loss spectrum (EELS) is unique for every cluster, and may be used to characterize a specific cluster. All the predicted physical quantities are in good agreement with the

Formation of solid Kr nanoclusters in MgO

NASA Astrophysics Data System (ADS)

van Huis, M. A.; van Veen, A.; Schut, H.; Kooi, B. J.; de Hosson, J. Th.

2003-06-01

The phenomenon of positron confinement enables us to investigate the electronic structure of nanoclusters embedded in host matrices. Solid Kr nanoclusters are a very interesting subject of investigation because of the very low predicted value of the positron affinity of bulk Kr. In this work, positron trapping in solid Kr nanoclusters embedded in MgO is investigated. The Kr nanoclusters were created by means of 280 keV Kr ion implantation in single crystals of MgO(100) and subsequent thermal annealing at a temperature of 1100 K. The nanoclusters were observed by cross-sectional transmission electron microscopy in high-resolution mode. The fcc Kr nanoclusters are rectangularly shaped with sizes of 2 to 5 nm and are in a cube-on-cube orientation relationship with the MgO host matrix. From the Moiré fringes in high-resolution recordings, the lattice parameter of the solid Kr was deduced and found to vary from 5.3 to 5.8 Å. The corresponding pressures are 0.6 2.5 GPa as found using the Ronchi equation of state. The relationship between lattice parameter and cluster size was investigated and it was found that the lattice parameter increases linearly with increasing nanocluster size. The defect evolution during annealing was monitored by means optical absorption spectroscopy and positron beam analysis. No evidence of positron trapping was found despite the very low positron affinity of solid Kr. Alternative definitions of the positron affinity are proposed for application to insulator materials.

Carbon and water fluxes from ponderosa pine forests disturbed by wildfire and thinning.

PubMed

Dore, S; Kolb, T E; Montes-Helu, M; Eckert, S E; Sullivan, B W; Hungate, B A; Kaye, J P; Hart, S C; Koch, G W; Finkral, A

2010-04-01

Disturbances alter ecosystem carbon dynamics, often by reducing carbon uptake and stocks. We compared the impact of two types of disturbances that represent the most likely future conditions of currently dense ponderosa pine forests of the southwestern United States: (1) high-intensity fire and (2) thinning, designed to reduce fire intensity. High-severity fire had a larger impact on ecosystem carbon uptake and storage than thinning. Total ecosystem carbon was 42% lower at the intensely burned site, 10 years after burning, than at the undisturbed site. Eddy covariance measurements over two years showed that the burned site was a net annual source of carbon to the atmosphere whereas the undisturbed site was a sink. Net primary production (NPP), evapotranspiration (ET), and water use efficiency were lower at the burned site than at the undisturbed site. In contrast, thinning decreased total ecosystem carbon by 18%, and changed the site from a carbon sink to a source in the first posttreatment year. Thinning also decreased ET, reduced the limitation of drought on carbon uptake during summer, and did not change water use efficiency. Both disturbances reduced ecosystem carbon uptake by decreasing gross primary production (55% by burning, 30% by thinning) more than total ecosystem respiration (TER; 33-47% by burning, 18% by thinning), and increased the contribution of soil carbon dioxide efflux to TER. The relationship between TER and temperature was not affected by either disturbance. Efforts to accurately estimate regional carbon budgets should consider impacts on carbon dynamics of both large disturbances, such as high-intensity fire, and the partial disturbance of thinning that is often used to prevent intense burning. Our results show that thinned forests of ponderosa pine in the southwestern United States are a desirable alternative to intensively burned forests to maintain carbon stocks and primary production.

Influence of oxygen on growth of carbon thin films

NASA Astrophysics Data System (ADS)

Kumar, Prabhat; Gupta, Mukul; Phase, D. M.; Stahn, Jochen

2018-04-01

In this work we studied the influence of oxygen gas on growth of carbon thin films in a magnetron sputtering process. X-ray absorption spectroscopy (XAS), x-ray and neutron reflectivity techniques were used to probe carbon thin films deposited with and without oxygen at room temperature. XAS in particularly x-ray absorption near edge spectroscopy (XANES) is powerful technique to identify the nature of hybridization of carbon atoms with other elements. In a XANES pattern, presence of C=O and C-O bonds is generally observed in spite of the fact that oxygen has not been deliberately included in the growth process. In order to confirm the presence of such features, we introduced a small amount of oxygen at 1% during the growth of carbon thin films. Though such additions do not affect the number density as observed by x-ray and neutron reflectivity, they severally affect the C K-edge spectra as evidenced by an enhancement in carbon-oxygen hybridization. Observed results are helpful in analyzing the C K-edge spectra more confidently.

Angular distribution of hybridization in sputtered carbon thin film

NASA Astrophysics Data System (ADS)

Liu, Y.; Wang, H.; Wei, Z. C.

2017-08-01

The sp3/sp2 ratio of sputtered carbon thin film depends on the ion bombardment process and tailors the physical properties of carbon thin film. In present work, we report the angular distribution of hybridization in magnetron sputtered carbon thin film for the first time. By x-ray photoelectron spectra analyses, it is found that the sp3/sp2 ratio increases linearly with increasing the deposition angle from 0 to 90 degree, which could be attributed to the enhancement of direct knocking-out of near-surface target atoms. In addition, we also derive the sp3/sp2 ratio by simulation on complex permittivity in terahertz frequency using a modified percolation approximation tunneling model. Those derived data consist with the results from x-ray photoelectron spectroscopy.

Carbon-based nanocomposites with aptamer-templated silver nanoclusters for the highly sensitive and selective detection of platelet-derived growth factor.

PubMed

Zhang, Zhihong; Guo, Chuanpan; Zhang, Shuai; He, Linghao; Wang, Minghua; Peng, Donglai; Tian, Junfeng; Fang, Shaoming

2017-03-15

We synthesized two kinds of carbon-based nanocomposites of silver nanoclusters (AgNCs). An aptamer for targeted platelet-derived growth factor-BB (PDGF-BB) detection was used as the organic phase to produce AgNCs@Apt, three dimensional reduced graphene oxide@AgNCs@Aptamer (3D-rGO@AgNCs@Apt), and graphene quantum dots@AgNCs@Aptamer (GQD@AgNCs@Apt) nanocomposites. The formation mechanism of the developed nanocomposites was described by detailed characterizations of their chemical and crystal structures. Subsequently, the as-synthesized nanoclusters containing aptamer strands were applied as the sensitive layers to fabricate a novel electrochemical aptasensor for the detection of PDGF-BB, which may be directly used to determine the target protein. Electrochemical impedance spectra showed that the developed 3D-rGO@AgNCs@Apt-based biosensor exhibited the highest sensitivity for PDGF-BB detection among three kinds of fabricated aptasensors, with an extremely low detection limit of 0.82pgmL -1 . In addition, the 3D-rGO@AgNCs@Apt-based biosensor showed high selectivity, stability, and applicability for the detection of PDGF-BB. This finding indicated that the AgNC-based nanocomposites prepared by a one-step method could be used as an electrochemical biosensor for various detection procedures in the biomedical field. Copyright © 2016 Elsevier B.V. All rights reserved.

Uranyl peroxide nanoclusters at high-pressure

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

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

Uranyl peroxide nanoclusters at high-pressure

DOE PAGES

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang; ...

2017-08-14

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

NanoClusters Enhance Drug Delivery in Mechanical Ventilation

NASA Astrophysics Data System (ADS)

Pornputtapitak, Warangkana

The overall goal of this thesis was to develop a dry powder delivery system for patients on mechanical ventilation. The studies were divided into two parts: the formulation development and the device design. The pulmonary system is an attractive route for drug delivery since the lungs have a large accessible surface area for treatment or drug absorption. For ventilated patients, inhaled drugs have to successfully navigate ventilator tubing and an endotracheal tube. Agglomerates of drug nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. This Thesis systematically investigated formulations of NanoClusters and their aerosol performance in a conventional inhaler and a device designed for use during mechanical ventilation. These engineered powders of budesonide (NC-Bud) were delivered via a MonodoseRTM inhaler or a novel device through commercial endotracheal tubes, and analyzed by cascade impaction. NC-Bud had a higher efficiency of aerosol delivery compared to micronized stock budesonide. The delivery efficiency was independent of ventilator parameters such as inspiration patterns, inspiration volumes, and inspiration flow rates. A novel device designed to fit directly to the ventilator and endotracheal tubing connections and the MonodoseRTM inhaler showed the same efficiency of drug delivery. The new device combined with NanoCluster formulation technology, therefore, allowed convenient and efficient drug delivery through endotracheal tubes. Furthermore, itraconazole (ITZ), a triazole antifungal agent, was formulated as a NanoCluster powder via milling (top-down process) or precipitation (bottom-up process) without using any excipients. ITZ NanoClusters prepared by wet milling showed better aerosol performance compared to micronized stock ITZ and ITZ NanoClusters prepared by precipitation. ITZ NanoClusters prepared by precipitation methods also showed an amorphous state

A comparative theoretical study on the structural, electronic and nonlinear optical features of B12N12 and Al12N12 nanoclusters with the groups III, IV and V dopants

NASA Astrophysics Data System (ADS)

Shakerzadeh, Ehsan; Barazesh, Neda; Talebi, Sima Zargar

2014-12-01

The structural, electronic and nonlinear optical properties of the two important fullerene-like cages of B12N12 and Al12N12 nanostructures with the groups III, IV and V dopants are investigated through density functional theory (DFT) calculations. It has been found that doping process induces local deformation at bond lengths near the doping site. Natural bond orbital (NBO) analyses are also performed for scrutinizing the structural properties of the considered nanoclusters. The results indicate that the groups III, IV and V dopants remarkably narrow the energy gap of the B12N12 nanocluster. On the other hand, although the energy gap of Al12N12 nanocluster is insensitive to groups III and V dopants; the carbon, silicon and germanium dopants extremely reduce the energy gap of this cluster. It seems that the electronic character of the B12N12 and Al12N12 nanocluster is sensitive to the dopants and it could be adjusted by particular impurity. Moreover the considered dopants induce hyperpolarizability in both of the considered nanoclusters. Interestingly, the replacing aluminum atom by carbon one in Al12N12 nanocluster (CAl11N12) leads to an extremely large hyperpolarizability value of 4358.77 a.u., which is the largest one among the considered doped clusters. It shows that the doping process plays an important role in enhancing the first hyperpolarizability of the B12N12 and Al12N12 nanoclusters.

Ultrafast, 2 min synthesis of monolayer-protected gold nanoclusters (d < 2 nm)

NASA Astrophysics Data System (ADS)

Martin, Matthew N.; Li, Dawei; Dass, Amala; Eah, Sang-Kee

2012-06-01

An ultrafast synthesis method is presented for hexanethiolate-coated gold nanoclusters (d < 2 nm, <250 atoms per nanocluster), which takes only 2 min and can be easily reproduced. With two immiscible solvents, gold nanoclusters are separated from the reaction byproducts fast and easily without any need for post-synthesis cleaning.An ultrafast synthesis method is presented for hexanethiolate-coated gold nanoclusters (d < 2 nm, <250 atoms per nanocluster), which takes only 2 min and can be easily reproduced. With two immiscible solvents, gold nanoclusters are separated from the reaction byproducts fast and easily without any need for post-synthesis cleaning. Electronic supplementary information (ESI) available: Experimental details of gold nanocluster synthesis and mass-spectrometry. See DOI: 10.1039/c2nr30890h

Advances in fractal germanium micro/nanoclusters induced by gold: microstructures and properties.

PubMed

Chen, Zhiwen; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

2014-02-01

Germanium materials are a class of unique semiconductor materials with widespread technological applications because of their valuable semiconducting, electrical, optical, and thermoelectric power properties in the fields of macro/mesoscopic materials and micro/nanodevices. In this review, we describe the efforts toward understanding the microstructures and various properties of the fractal germanium micro/nanoclusters induced by gold prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the integer and non-integer dimensional germanium micro/nanoclusters such as nanoparticles, nanorings, and nanofractals induced by gold and annealing. In particular, the nonlinear electrical behavior of a gold/germanium bilayer film with the interesting nanofractal is discussed in detail. In addition, the third-order optical nonlinearities of the fractal germanium nanocrystals embedded in gold matrix will be summarized by using the sensitive and reliable Z-scan techniques aimed to determine the nonlinear absorption coefficient and nonlinear refractive index. Finally, we emphasize the thermoelectric power properties of the gold/germanium bilayer films. The thermoelectric power measurement is considered to be a more effective method than the conductivity for investigating superlocalization in a percolating system. This research may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices. Once mastered, germanium thin films with a variety of fascinating micro/nanoclusters will offer vast and unforeseen opportunities in the semiconductor industry as well as in other fields of science and technology.

Silver nanocluster catalytic microreactors for water purification

NASA Astrophysics Data System (ADS)

Da Silva, B.; Habibi, M.; Ognier, S.; Schelcher, G.; Mostafavi-Amjad, J.; Khalesifard, H. R. M.; Tatoulian, M.; Bonn, D.

2016-07-01

A new method for the elaboration of a novel type of catalytic microsystem with a high specific area catalyst is developed. A silver nanocluster catalytic microreactor was elaborated by doping a soda-lime glass with a silver salt. By applying a high power laser beam to the glass, silver nanoclusters are obtained at one of the surfaces which were characterized by BET measurements and AFM. A microfluidic chip was obtained by sealing the silver coated glass with a NOA 81 microchannel. The catalytic activity of the silver nanoclusters was then tested for the efficiency of water purification by using catalytic ozonation to oxidize an organic pollutant. The silver nanoclusters were found to be very stable in the microreactor and efficiently oxidized the pollutant, in spite of the very short residence times in the microchannel. This opens the way to study catalytic reactions in microchannels without the need of introducing the catalyst as a powder or manufacturing complex packed bed microreactors.

A Comparative XAFS Study of Gold-thiolate Nanoparticles and Nanoclusters

NASA Astrophysics Data System (ADS)

Chevrier, D. M.; Chatt, A.; Sham, T. K.; Zhang, P.

2013-04-01

Tiopronin-capped gold nanoparticles and gold nanoclusters of sizes 3.0 and 1.5 nm, respectively, were investigated with XAFS at the gold L3-edge. The specific EXAFS fitting procedure is discussed for obtaining reliable fit parameters for each system. The difficulties and challenges faced when analysing EXAFS data for gold nanoparticles and nanoclusters are also mentioned. Fitting results for gold nanoparticles reveal a small amount of surface Au-thiolate interactions with a large Au-Au metal core. For gold nanoclusters, only a one-shell fit was obtainable. Instead of Au-Au metal core, long-range interactions are expected for gold nanoclusters. Tiopronin-capped gold nanoclusters are proposed to be polymeric in nature, which helps explain the observed red luminescence.

Synthesis, Characterization and Application of Water-soluble Gold and Silver Nanoclusters

NASA Astrophysics Data System (ADS)

Kumar, Santosh

The term `nanotechnology' has emerged as a buzzword since the last few decades. It has found widespread applications across disciplines, from medicine to energy. The synthesis of gold and silver nanoclusters has found much excitement, due to their novel material properties. Seminal work by various groups, including ours, has shown that the size of these clusters can be controlled with atomic precision. This control gives access to tuning the optical and electronic properties. The majority of nanoclusters reported thus far are not water soluble, which limit their applications in biology that requires water-solubility. Going from organic to aqueous phase is by no means a simple task, as it is associated with many challenges. Their stability in the presence of oxygen, difficulty in characterization, and separation of pure nanoclusters are some of the major bottlenecks associated with the synthesis of water-soluble gold nanoclusters. Water-soluble gold nanoclusters hold great potential in biological labeling, bio-catalysis and nano-bioconjugates. To overcome this problem, a new ligand with structural rigidity is needed. After considering various possibilities, we chose Captopril as a candidate ligand. In my thesis research, the synthesis of Au25 nanocluster capped with captopril has been reported. Captopril-protected Au25 nanocluster showed significantly higher thermal stability and enhanced chiroptical properties than the Glutathione-capped cluster, which confirms our initial rationale, that the ligand is critical in protecting the nanocluster. The optical absorption properties of these Au25 nanoclusters are studied and compared to the plasmonic nanoparticles. The high thermal stability and solubility of Au25 cluster capped with Captopril motivated us to explore this ligand for the synthesis of other gold clusters. Captopril is a chiral molecule with two chiral centers. The chiral ligand can induce chirality to the overall cluster, even if the core is achiral

Photophysical and redox properties of molecule-like CdSe nanoclusters.

PubMed

Dolai, Sukanta; Dass, Amala; Sardar, Rajesh

2013-05-21

Advancing our understanding of the photophysical and electrochemical properties of semiconductor nanoclusters with a molecule-like HOMO-LUMO energy level will help lead to their application in photovoltaic devices and photocatalysts. Here we describe an approach to the synthesis and isolation of molecule-like CdSe nanoclusters, which displayed sharp transitions at 347 nm (3.57 eV) and 362 nm (3.43 eV) in the optical spectrum with a lower energy band extinction coefficient of ~121,000 M(-1) cm(-1). Mass spectrometry showed a single nanocluster molecular weight of 8502. From this mass and various spectroscopic analyses, the nanoclusters are determined to be of the single molecular composition Cd34Se20(SPh)28, which is a new nonstiochiometric nanocluster. Their reversible electrochemical band gap determined in Bu4NPF6/CH3CN was found to be 4.0 V. There was a 0.57 eV Coulombic interaction energy of the electron-hole pair involved. The scan rate dependent electrochemistry suggested diffusion-limited transport of nanoclusters to the electrode. The nanocluster diffusion coefficient (D = 5.4 × 10 (-4) cm(2)/s) in acetonitrile solution was determined from cyclic voltammetry, which suggested Cd34Se20(SPh)28 acts as a multielectron donor or acceptor. We also present a working model of the energy level structure of the newly discovered nanocluster based on its photophysical and redox properties.

The role of protein characteristics in the formation and fluorescence of Au nanoclusters

NASA Astrophysics Data System (ADS)

Xu, Yaolin; Sherwood, Jennifer; Qin, Ying; Crowley, Dorothy; Bonizzoni, Marco; Bao, Yuping

2014-01-01

Protein-encapsulated gold nanoclusters have shown many advantages over other gold nanocluster systems, including green synthesis, biocompatibility, high water solubility, and the ease of further conjugation. In this article, we systematically investigated the effects of the protein size and amino acid content on the formation and fluorescent properties of gold nanoclusters using four model proteins (bovine serum albumin, lysozyme, trypsin, and pepsin). We discovered that the balance of amine and tyrosine/tryptophan containing residues was critical for the nanocluster formation. Protein templates with low cysteine contents caused blue shifts in the fluorescent emissions and difference in fluorescent lifetimes of the gold nanoclusters. Furthermore, the protein size was found to be a critical factor for the photostability and long-term stability of gold nanoclusters. The size of the protein also affected the Au nanocluster behaviour after immobilization.Protein-encapsulated gold nanoclusters have shown many advantages over other gold nanocluster systems, including green synthesis, biocompatibility, high water solubility, and the ease of further conjugation. In this article, we systematically investigated the effects of the protein size and amino acid content on the formation and fluorescent properties of gold nanoclusters using four model proteins (bovine serum albumin, lysozyme, trypsin, and pepsin). We discovered that the balance of amine and tyrosine/tryptophan containing residues was critical for the nanocluster formation. Protein templates with low cysteine contents caused blue shifts in the fluorescent emissions and difference in fluorescent lifetimes of the gold nanoclusters. Furthermore, the protein size was found to be a critical factor for the photostability and long-term stability of gold nanoclusters. The size of the protein also affected the Au nanocluster behaviour after immobilization. Electronic supplementary information (ESI) available See DOI: 10

Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.

PubMed

Dore, Sabina; Montes-Helu, Mario; Hart, Stephen C; Hungate, Bruce A; Koch, George W; Moon, John B; Finkral, Alex J; Kolb, Thomas E

2012-10-01

Carbon uptake by forests is a major sink in the global carbon cycle, helping buffer the rising concentration of CO 2 in the atmosphere, yet the potential for future carbon uptake by forests is uncertain. Climate warming and drought can reduce forest carbon uptake by reducing photosynthesis, increasing respiration, and by increasing the frequency and intensity of wildfires, leading to large releases of stored carbon. Five years of eddy covariance measurements in a ponderosa pine (Pinus ponderosa)-dominated ecosystem in northern Arizona showed that an intense wildfire that converted forest into sparse grassland shifted site carbon balance from sink to source for at least 15 years after burning. In contrast, recovery of carbon sink strength after thinning, a management practice used to reduce the likelihood of intense wildfires, was rapid. Comparisons between an undisturbed-control site and an experimentally thinned site showed that thinning reduced carbon sink strength only for the first two posttreatment years. In the third and fourth posttreatment years, annual carbon sink strength of the thinned site was higher than the undisturbed site because thinning reduced aridity and drought limitation to carbon uptake. As a result, annual maximum gross primary production occurred when temperature was 3 °C higher at the thinned site compared with the undisturbed site. The severe fire consistently reduced annual evapotranspiration (range of 12-30%), whereas effects of thinning were smaller and transient, and could not be detected in the fourth year after thinning. Our results show large and persistent effects of intense fire and minor and short-lived effects of thinning on southwestern ponderosa pine ecosystem carbon and water exchanges. © 2012 Blackwell Publishing Ltd.

Thin Carbon Layers on Nanostructured Silicon-Properties and Applications

NASA Astrophysics Data System (ADS)

Angelescu, Anca; Kleps, Irina; Miu, Mihaela; Simion, Monica; Bragaru, Adina; Petrescu, Stefana; Paduraru, Crina; Raducanu, Aurelia

Thin carbon layers such as silicon carbide (SiC) and diamond like carbon (DLC) layers on silicon, or on nanostructured silicon substrats were obtained by different methods. This paper is a review of our results in the areas of carbon layer microfabrication technologies and their properties related to different microsystem apllications. So, silicon membranes using a-SiC or DLC layers as etching mask, as well as silicon carbide membranes using a combined porous silicon — DLC structure were fabricated for sensor applications. A detailed evaluation of the field emission (FE) properties of these films was done to demonstrate their capability to be used in field emission devices. Carbon thin layers on nanostructured silicon samples were also investigated with respect to the living cell adhesion on these structures. The experiments indicate that the cell attachment on the surface of carbon coatings can be controlled by deposition parameters during the technological process.

A thermochromic silver nanocluster exhibiting dual emission character

NASA Astrophysics Data System (ADS)

Xu, Qing-Qing; Dong, Xi-Yan; Huang, Ren-Wu; Li, Bo; Zang, Shuang-Quan; Mak, Thomas C. W.

2015-01-01

A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow.A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow. Electronic supplementary information (ESI) available: Experimental section and supporting Fig. S1-S6. CCDC 1004246. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr05122j

Nanocluster irradiation evolution in Fe-9%Cr ODS and ferritic-martensitic alloys

NASA Astrophysics Data System (ADS)

Swenson, M. J.; Wharry, J. P.

2017-12-01

The objective of this study is to evaluate the influence of dose rate and cascade morphology on nanocluster evolution in a model Fe-9%Cr oxide dispersion strengthened steel and the commercial ferritic/martensitic (F/M) alloys HCM12A and HT9. We present a large, systematic data set spanning the three alloys, three irradiating particle types, four orders of magnitude in dose rate, and doses ranging 1-100 displacements per atom over 400-500 °C. Nanoclusters are characterized using atom probe tomography. ODS oxide nanoclusters experience partial dissolution after irradiation due to inverse Ostwald ripening, while F/M nanoclusters undergo Ostwald ripening. Damage cascade morphology is indicative of nanocluster number density evolution. Finally, the effects of dose rate on nanocluster morphology provide evidence for a temperature dilation theory, which purports that a negative temperature shift is necessary for higher dose rate irradiations to emulate nanocluster evolution in lower dose rate irradiations.

Methods of making non-covalently bonded carbon-titania nanocomposite thin films and applications of the same

DOEpatents

Liang, Yu Teng; Vijayan, Baiju K.; Gray, Kimberly A.; Hersam, Mark C.

2016-07-19

In one aspect, a method of making non-covalently bonded carbon-titania nanocomposite thin films includes: forming a carbon-based ink; forming a titania (TiO.sub.2) solution; blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films. In certain embodiments, the carbon-based titania nanocomposite thin films may include solvent-exfoliated graphene titania (SEG-TiO.sub.2) nanocomposite thin films, or single walled carbon nanotube titania (SWCNT-TiO.sub.2) nanocomposite thin films.

Ab initio Investigation of Helium in Vanadium Oxide Nanoclusters

NASA Astrophysics Data System (ADS)

Danielson, Thomas; Tea, Eric; Hin, Celine

Nanostructured ferritic alloys (NFAs) are strong candidate materials for the next generation of fission reactors and future fusion reactors. They are characterized by a large number density of oxide nanoclusters dispersed throughout a BCC iron matrix, where current oxide nanoclusters are primarily comprised of Y-Ti-O compounds. The oxide nanoclusters provide the alloy with high resistance to neutron irradiation, high yield strength and high creep strength at the elevated temperatures of a reactor environment. In addition, the oxide nanoclusters serve as trapping sites for transmutation product helium providing substantially increased resistance to catastrophic cracking and embrittlement. Although the mechanical properties and radiation resistance of the existing NFAs is promising, the problem of forming large scale reactor components continues to present a formidable challenge due to the high hardness and unpredictable fracture behavior of the alloys. An alternative alloy has been previously proposed and fabricated where vanadium is added in order to form vanadium oxide nanoclusters that serve as deflection sites for crack propagation. Although experiments have shown evidence that the fracture behavior of the alloys is improved, it is unknown whether or not the vanadium oxide nanoclusters are effective trapping sites for helium. We present results obtained using density functional theory investigating the thermodynamic stability of helium with the vanadium oxide matrix to make a comparison of trapping effectiveness to traditional Y-Ti-O compounds.

An oscillator based on a single Au nanocluster

NASA Astrophysics Data System (ADS)

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

2017-01-01

Metal nanoclusters embedded into the ultrathin dielectric films attracted much attention in recent years due to their unusual electronic, optical, etc., properties differing from those of the bulk metals essentially and, hence, to the prospects of their applications in novel nanoelectronic, single electronic, non-volatile memory, etc., devices. Here, we report on the experimental observation of the electrical oscillations in an oscillating loop connected to a contact of a conductive probe of an Atomic Force Microscope to a tunnel-transparent ( ˜6.5 nm thick) yttria stabilized zirconia film with embedded Au nanoclusters on the Si substrate. The oscillations were attributed to the negative differential resistance of the probe-to-sample contact originating from the resonant electron tunnelling between the probe and the Si substrate via the quantum confined electron energy levels in small ( ≈2.5 nm in diameter) Au nanoclusters. This observation demonstrates the prospects of building an oscillator nanoelectronic device based on an individual nanometer-sized metal nanocluster.

Role of structurally and magnetically modified nanoclusters in colossal magnetoresistance

PubMed Central

Tao, Jing; Niebieskikwiat, Dario; Jie, Qing; Schofield, Marvin A.; Wu, Lijun; Li, Qiang; Zhu, Yimei

2011-01-01

It is generally accepted that electronic and magnetic phase separation is the origin of many of exotic properties of strongly correlated electron materials, such as colossal magnetoresistance (CMR), an unusually large variation in the electrical resistivity under applied magnetic field. In the simplest picture, the two competing phases are those associated with the material state on either side of the phase transition. Those phases would be paramagnetic insulator and ferromagnetic metal for the CMR effect in doped manganites. It has been speculated that a critical component of the CMR phenomenon is nanoclusters with quite different properties than either of the terminal phases during the transition. However, the role of these nanoclusters in the CMR effect remains elusive because the physical properties of the nanoclusters are hard to measure when embedded in bulk materials. Here we show the unexpected behavior of the nanoclusters in the CMR compound La1-xCaxMnO3 (0.4 ≤ x < 0.5) by directly correlating transmission electron microscopy observations with bulk measurements. The structurally modified nanoclusters at the CMR temperature were found to be ferromagnetic and exhibit much higher electrical conductivity than previously proposed. Only at temperatures much below the CMR transition, the nanoclusters are antiferromagnetic and insulating. These findings substantially alter the current understanding of these nanoclusters on the material’s functionality and would shed light on the microscopic study on the competing spin-lattice-charge orders in strongly correlated systems. PMID:22160678

The carbon consequences of thinning techniques: stand structure makes a difference

Treesearch

Coeli Hoover; Susan Stout

2007-01-01

Using results from a 25-year study of thinning in a northwestern Pennsylvania Allegheny hardwood stand, we assess whether and how thinning method affected carbon sequestration and merchantable volume production. Plots were thinned to similar residual relative density by removing trees from different portions of the diameter distribution. Plots that were thinned from...

Method for fabricating thin films of pyrolytic carbon

DOEpatents

Brassell, Gilbert W.; Lewis, Jr., John; Weber, Gary W.

1982-01-01

The present invention relates to a method for fabricating ultra-thin films of pyrolytic carbon. Pyrolytic carbon is vapor deposited onto a concave surface of a heated substrate to a total uniform thickness in the range of about 0.1 to 1.0 micrometer. The carbon film on the substrate is provided with a layer of adherent polymeric resin. The resulting composite film of pyrolytic carbon and polymeric resin is then easily separated from the substrate by shrinking the polymeric resin coating with thermally induced forces.

Carbon-Nanotube Conductive Layers for Thin-Film Solar Cells

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2005-01-01

Thin, transparent layers comprising mats of carbon nanotubes have been proposed for providing lateral (that is, inplane) electrical conductivities for collecting electric currents from the front surfaces of the emitter layers of thin-film solar photovoltaic cells. Traditionally, thin, semitransparent films of other electrically conductive materials (usually, indium tin oxide, zinc oxide, or cadmium sulfide) have been used for this purpose. As in the cases of the traditional semitransparent conductive films, the currents collected by the nanotube layers would, in turn, be further collected by front metal contact stripes. Depending on details of a specific solar-cell design, the layer of carbon nanotubes would be deposited in addition to, or instead of, a semitransparent layer of one of these traditional conductive materials (see figure). The proposal is expected to afford the following advantages: The electrical conductivity of the carbon- nanotube layer would exceed that of the corresponding semitransparent layer of traditional electrically conductive material. The greater electrical conductivity of the carbon-nanotube layer would make it possible to retain adequate lateral electrical conductivity while reducing the thickness of, or eliminating entirely, the traditional semitransparent conductive layer. As a consequence of thinning or elimination of the traditional semitransparent conductive layer, less light would be absorbed, so that more of the incident light would be available for photovoltaic conversion. The greater electrical conductivity of the carbon-nanotube layer would make it possible to increase the distance between front metal contact stripes, in addition to (or instead of) thinning or eliminating the layer of traditional semitransparent conductive material. Consequently, the fraction of solar-cell area shadowed by front metal contact stripes would be reduced again, making more of the incident light available for photovoltaic conversion. The electrical

Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

PubMed Central

Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

2013-01-01

Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms. PMID:28348350

Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires.

PubMed

Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

2013-09-09

Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

Atomically precise metal nanoclusters: stable sizes and optical properties

NASA Astrophysics Data System (ADS)

Jin, Rongchao

2015-01-01

Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ~3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure-property relationships.

Photo-oxidation method using MoS2 nanocluster materials

DOEpatents

Wilcoxon, Jess P.

2001-01-01

A method of photo-oxidizing a hydrocarbon compound is provided by dispersing MoS.sub.2 nanoclusters in a solvent containing a hydrocarbon compound contaminant to form a stable solution mixture and irradiating the mixture to photo-oxide the hydrocarbon compound. Hydrocarbon compounds of interest include aromatic hydrocarbon and chlorinated hydrocarbons. MoS.sub.2 nanoclusters with an average diameter less than approximately 10 nanometers are shown to be effective in decomposing potentially toxic aromatic and chlorinated hydrocarbons, such as phenol, pentachlorophenol, chlorinated biphenols, and chloroform, into relatively non-toxic compounds. The irradiation can occur by exposing the MoS.sub.2 nanoclusters and hydrocarbon compound mixture with visible light. The MoS.sub.2 nanoclusters can be introduced to the toxic hydrocarbons as either a MoS.sub.2 solution or deposited on a support material.

Growth and Stability of Titanium Dioxide Nanoclusters on Graphene/Ru(0001)

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

Frederick, Ryan T.; Novotny, Zbynek; Netzer, Falko P.

Titanium dioxide/graphene composites have recently been demonstrated to improve the photocatalytic activity of TiO2 in visible light. To better understand the interactions of TiO2 with graphene we have investigated the growth of TiO2 nanoclusters on single-layer graphene/Ru(0001) using scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Deposition of Ti in the O2 background at 300 K resulted in the formation of nanoclusters nucleating on intrinsic defects in the graphene (Gr) layer. The saturation nanocluster density decreased as the substrate temperature was increased from 300 to 650 K, while deposition at 700 K resulted in the significant etching of themore » Gr layer. We have also prepared nanoclusters with Ti2O3 stoichiometry using lower O2 pressures at 650 K. Thermal stability of the TiO2 nanoclusters prepared at 300 K was evaluated with AES and STM. No change in oxidation state for the TiO2 nanoclusters or etching of the Gr layer was observed up to ~900 K. Annealing studies characterized using STM revealed that cluster ripening proceeds via a Smoluchowski mechanism below 800 K and that Ostwald ripening dominates above 800 K. At even higher temperatures, the nanoclusters undergo reduction to TiOx (x ≈ 1 - 1.5) which is accompanied by oxidation and etching of the Gr. Our studies demonstrate that highly thermally stable TiOx nanoclusters of controlled composition and morphology can be prepared on Gr supports.« less

Cluster perturbation theory for calculation of electronic properties of ensembles of metal nanoclusters

NASA Astrophysics Data System (ADS)

Zhumagulov, Yaroslav V.; Krasavin, Andrey V.; Kashurnikov, Vladimir A.

2018-05-01

The method is developed for calculation of electronic properties of an ensemble of metal nanoclusters with the use of cluster perturbation theory. This method is applied to the system of gold nanoclusters. The Greens function of single nanocluster is obtained by ab initio calculations within the framework of the density functional theory, and then is used in Dyson equation to group nanoclusters together and to compute the Greens function as well as the electron density of states of the whole ensemble. The transition from insulator state of a single nanocluster to metallic state of bulk gold is observed.

Pure white-light emitting ultrasmall organic-inorganic hybrid perovskite nanoclusters.

PubMed

Teunis, Meghan B; Lawrence, Katie N; Dutta, Poulami; Siegel, Amanda P; Sardar, Rajesh

2016-10-14

Organic-inorganic hybrid perovskites, direct band-gap semiconductors, have shown tremendous promise for optoelectronic device fabrication. We report the first colloidal synthetic approach to prepare ultrasmall (∼1.5 nm diameter), white-light emitting, organic-inorganic hybrid perovskite nanoclusters. The nearly pure white-light emitting ultrasmall nanoclusters were obtained by selectively manipulating the surface chemistry (passivating ligands and surface trap-states) and controlled substitution of halide ions. The nanoclusters displayed a combination of band-edge and broadband photoluminescence properties, covering a major part of the visible region of the solar spectrum with unprecedentedly large quantum yields of ∼12% and photoluminescence lifetime of ∼20 ns. The intrinsic white-light emission of perovskite nanoclusters makes them ideal and low cost hybrid nanomaterials for solid-state lighting applications.

Enhanced pulsed magneto-motive ultrasound imaging using superparamagnetic nanoclusters

PubMed Central

Mehrmohammadi, M; Yoon, KY; Qu, M; Johnston, KP; Emelianov, SY

2011-01-01

Recently, pulsed magneto-motive ultrasound (pMMUS) imaging augmented with ultra-small magnetic nanoparticles has been introduced as a tool capable of imaging events at molecular and cellular levels. The sensitivity of a pMMUS system depends on several parameters, including the size, geometry and magnetic properties of the nanoparticles. Under the same magnetic field, larger magnetic nanostructures experience a stronger magnetic force and produce larger displacement, thus improving the sensitivity and signal-to-noise ratio (SNR) of pMMUS imaging. Unfortunately, large magnetic iron-oxide nanoparticles are typically ferromagnetic and thus are very difficult to stabilize against colloidal aggregation. In the current study we demonstrate improvement of pMMUS image quality by using large size superparamagnetic nanoclusters characterized by strong magnetization per particle. Water-soluble magnetic nanoclusters of two sizes (15 and 55 nm average size) were synthesized from 3 nm iron precursors in the presence of citrate capping ligand. The size distribution of synthesized nanoclusters and individual nanoparticles was characterized using dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM). Tissue mimicking phantoms containing single nanoparticles and two sizes of nanoclusters were imaged using a custom-built pMMUS imaging system. While the magnetic properties of citrate-coated nanoclusters are identical to those of superparamagnetic nanoparticles, the magneto-motive signal detected from nanoclusters is larger, i.e. the same magnetic field produced larger magnetically induced displacement. Therefore, our study demonstrates that clusters of superparamagnetic nanoparticles result in pMMUS images with higher contrast and SNR. PMID:21157009

Silicon nanocluster-sensitized emission from erbium: The role of stress in the formation of silicon nanoclusters

NASA Astrophysics Data System (ADS)

Ahmad, I.; Temple, M. P.; Kallis, A.; Wojdak, M.; Oton, C. J.; Barbier, D.; Saleh, H.; Kenyon, A. J.; Loh, W. H.

2008-12-01

Erbium-doped silicon-rich silicon oxide films deposited by plasma enhanced chemical vapor deposition suffer from compressive stress as deposited, which converts to a large tensile stress on annealing due to the release of hydrogen. Although the cracking that results from this stress can be avoided by patterning the films into ridges, significant stress remains along the ridge axis. Measurements of erbium photoluminescence sensitized by silicon nanoclusters in stressed and relaxed films suggest an important role for internal film stresses in promoting the phase separation of excess silicon into nanoclusters, which has previously been thought of as a thermally driven process.

Analysis of carbonated thin liquids in pediatric neurogenic dysphagia

PubMed Central

Lundine, Jennifer P.; Bates, David G.; Yin, Han

2015-01-01

Background Aspiration of liquids is a serious complication of neurological impairments such as traumatic brain injury or stroke. Carbonated liquids have been examined as a possible alternative to thickened liquids to help reduce aspiration in cases of dysphagia in adults, but no published literature to the best of our knowledge has evaluated this technique in children. If carbonated liquids result in safer swallowing in children, they could provide a preferred alternative to thickened liquids. Objective This pilot study examined whether carbonated thin liquids (CARB) improved swallowing compared to noncarbonated thin liquids (NOCARB) for children with neurogenic dysphagia. Materials and methods Twenty-four children admitted to a level I trauma center for acute neurological injury/disease were evaluated via videofluoroscopic swallow studies. Four descriptive outcome measures were contrasted. Results CARB significantly decreased pooling (P=0.0006), laryngeal penetration/aspiration (P=0.0044) and Penetration-Aspiration Scale scores (P=0.0127) when compared to NOCARB. On average, CARB improved scores on the Penetration-Aspiration Scale by 3.7 points for participants who aspirated NOCARB. There was no significant difference in pharyngeal residue noted between CARB and NOCARB (P=0.0625). Conclusion These findings support the hypothesis that carbonated thin liquids may provide an alternative to thickened liquids for children with neurogenic dysphagia. Implications for future research and clinical practice are discussed. PMID:25758792

Reduction of furnace temperature in ultra long carbon nanotube growth by plasmonic excitation of electron Fermi gas of catalytic nanocluster

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

Saeidi, Mohammadreza, E-mail: Saeidi.mr@gmail.com, E-mail: m.saeidi@shahed.ac.ir

2016-06-15

In this paper, a novel physical method is presented to reduce the temperature of the furnace and prevent loss of thermal energy in ultra long carbon nanotube (CNT) growth process by catalytic chemical vapor deposition. This method is based on the plasmonic excitation of electron Fermi gas of catalytic nanocluster sitting at tip end of CNT by ultraviolet (UV) irradiation. Physical concepts of the method are explained in detail. The results of applying the presented method consequences to an appropriate tip-growth mechanism of the ultra long CNTs show that, in the presence of plasmonic excitation, the growth rate of themore » CNT is enhanced. Demonstration of temperature reduction and simultaneous increase in CNT length by UV irradiation with the proper frequency are the most important and practical result of the paper. All results are interpreted and discussed.« less

Photoluminescence and structural characteristics of CdS nanoclusters synthesized by hydrothermal microemulsion

NASA Astrophysics Data System (ADS)

Liu, Bing; Xu, G. Q.; Gan, L. M.; Chew, C. H.; Li, W. S.; Shen, Z. X.

2001-01-01

Spherical and uniform CdS nanoclusters were synthesized by hydrothermal microemulsion. The reaction of Cd2+ ions with S2- ions generated from the decomposition of thioacetamide proceeded in water microdroplets. The mean diameter of the CdS nanoclusters can be varied from 20 to 80 nm by increasing the reaction temperature from 30 to 120 °C. XRD results indicate that the resulting CdS nanoclusters have a reduced and distorted hexagonal lattice compared to bulk materials. Two intense luminescence bands, i.e., green and red, were observed to coexist in the CdS nanoclusters. Their peak positions and relative intensities were found to be sensitive to the size and structure of nanoclusters. These emissions are attributed to surface defects (green emission) and the Cd-Cl composite vacancies (red emission).

Selective hydrogenation of acetylene in the presence of ethylene on palladium nanocluster surfaces: A DFT study

NASA Astrophysics Data System (ADS)

Abdollahi, Tahereh; Farmanzadeh, Davood

2018-03-01

In this work, by density functional theory, the palladium nanoclusters were investigated in order to design new catalysts for the selective hydrogenation of acetylene present in olefin feeds. At first, the palladium nanoclusters were studied using PBE-G functional with DNP-ECP basis set. According to the performed calculations, among all the Pdn (n = 2-15) nanoclusters, two Pd12 and Pd2 nanoclusters can be used as catalysts in the reactions of hydrogenation of acetylene and ethylene. The adsorption energy of hydrogen on the Pd12 nanocluster is higher than that of acetylene and ethylene, and therefore, the Pd12 nanocluster is more appropriate for the hydrogenation of acetylene and ethylene. However, the calculated activation energy barriers for the reactions of hydrogenation of acetylene and ethylene showed that the Pd2 nanocluster has more selectivity in comparison to the Pd12 nanocluster. According to our results, the activation energy of the hydrogenation of acetylene to vinyl on the Pd2 nanocluster is 23.96 kJ/mol lower than that on the Pd12 nanocluster. Also, the activation energy of the hydrogenation of ethylene to ethyl on the Pd2 nanocluster is higher than that on the Pd12 nanocluster Therefore, it seems that the Pd2 surface can be used as a catalyst for the selective hydrogenation of acetylene.

Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing.

PubMed

Zhou, Zhengping; Liu, Guoliang

2017-04-01

Herein an approach to controlling the pore size of mesoporous carbon thin films from metal-free polyacrylonitrile-containing block copolymers is described. A high-molecular-weight poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The authors systematically investigate the self-assembly behavior of PAN-b-PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA is microphase-separated into uniformly spaced globular nanostructures, and these globular nanostructures evolve into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN-b-PMMA into mesoporous carbon thin films, the pore size and center-to-center spacing increase significantly with thermal annealing temperature, different from most block copolymers. In addition, the choice of solvent in solvent annealing strongly influences the block copolymer nanostructure and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon accretion in unthinned and thinned young-growth forest stands of the Alaskan perhumid coastal temperate rainforest.

PubMed

D'Amore, David V; Oken, Kiva L; Herendeen, Paul A; Steel, E Ashley; Hennon, Paul E

2015-12-01

Accounting for carbon gains and losses in young-growth forests is a key part of carbon assessments. A common silvicultural practice in young forests is thinning to increase the growth rate of residual trees. However, the effect of thinning on total stand carbon stock in these stands is uncertain. In this study we used data from 284 long-term growth and yield plots to quantify the carbon stock in unthinned and thinned young growth conifer stands in the Alaskan coastal temperate rainforest. We estimated carbon stocks and carbon accretion rates for three thinning treatments (basal area removal of 47, 60, and 73 %) and a no-thin treatment across a range of productivity classes and ages. We also accounted for the carbon content in dead trees to quantify the influence of both thinning and natural mortality in unthinned stands. The total tree carbon stock in naturally-regenerating unthinned young-growth forests estimated as the asymptote of the accretion curve was 484 (±26) Mg C ha -1 for live and dead trees and 398 (±20) Mg C ha -1 for live trees only. The total tree carbon stock was reduced by 16, 26, and 39 % at stand age 40 y across the increasing range of basal area removal. Modeled linear carbon accretion rates of stands 40 years after treatment were not markedly different with increasing intensity of basal area removal from reference stand values of 4.45 Mg C ha -1  year -1 to treatment stand values of 5.01, 4.83, and 4.68 Mg C ha -1  year -1 respectively. However, the carbon stock reduction in thinned stands compared to the stock of carbon in the unthinned plots was maintained over the entire 100 year period of observation. Thinning treatments in regenerating forest stands reduce forest carbon stocks, while carbon accretion rates recovered and were similar to unthinned stands. However, that the reduction of carbon stocks in thinned stands persisted for a century indicate that the unthinned treatment option is the optimal choice for short

Nanoclustering phase competition induces the resistivity hump in colossal magnetoresistive manganites

NASA Astrophysics Data System (ADS)

Pradhan, Kalpataru; Yunoki, Seiji

2017-12-01

Using a two-band double-exchange model with Jahn-Teller lattice distortions and superexchange interactions, supplemented by quenched disorder, at an electron density n =0.65 , we explicitly demonstrate the coexistence of the n =1 /2 -type (π ,π ) charge-ordered and the ferromagnetic nanoclusters above the ferromagnetic transition temperature Tc in colossal magnetoresistive (CMR) manganites. The resistivity increases due to the enhancement of the volume fraction of the charge-ordered and the ferromagnetic nanoclusters upon decreasing the temperature down to Tc. The ferromagnetic nanoclusters start to grow and merge, and the volume fraction of the charge-ordered nanoclusters decreases below Tc, leading to the sharp drop in the resistivity. By applying a small external magnetic field h , we show that the resistivity above Tc increases, as compared with the case when h =0 , a fact that further confirms the coexistence of the charge-ordered and the ferromagnetic nanoclusters. In addition, we show that the volume fraction of the charge-ordered nanoclusters decreases upon increasing the bandwidth, and consequently the resistivity hump diminishes for large bandwidth manganites, in good qualitative agreement with experiments. The obtained insights from our calculations provide a complete pathway to understand the phase competition in CMR manganites.

Electrical transport properties in Fe-Cr nanocluster-assembled granular films

NASA Astrophysics Data System (ADS)

Wang, Xiong-Zhi; Wang, Lai-Sen; Zhang, Qin-Fu; Liu, Xiang; Xie, Jia; Su, A.-Mei; Zheng, Hong-Fei; Peng, Dong-Liang

2017-09-01

The Fe100-xCrx nanocluster-assembled granular films with Cr atomic fraction (x) ranging from 0 to 100 were fabricated by using a plasma-gas-condensation cluster deposition system. The TEM characterization revealed that the uniform Fe clusters were coated with a Cr layer to form a Fe-Cr core-shell structure. Then, the as-prepared Fe100-xCrx nanoclusters were randomly assembled into a granular film in vacuum environments with increasing the deposition time. Because of the competition between interfacial resistance and shunting effect of Cr layer, the room temperature resistivity of the Fe100-xCrx nanocluster-assembled granular films first increased and then decreased with increasing the Cr atomic fraction (x), and revealed a maximum of 2 × 104 μΩ cm at x = 26 at.%. The temperature-dependent longitudinal resistivity (ρxx), magnetoresistance (MR) effect and anomalous Hall effect (AHE) of these Fe100-xCrx nanocluster-assembled granular films were also studied systematically. As the x increased from 0 to 100, the ρxx of all samples firstly decreased and then increased with increasing the measuring temperature. The dependence of ρxx on temperature could be well addressed by a mechanism incorporated for the fluctuation-induced-tunneling (FIT) conduction process and temperature-dependent scattering effect. It was found that the anomalous Hall effect (AHE) had no legible scaling relation in Fe100-xCrx nanocluster-assembled granular films. However, after deducting the contribution of tunneling effect, the scaling relation was unambiguous. Additionally, the Fe100-xCrx nanocluster-assembled granular films revealed a small negative magnetoresistance (MR), which decreased with the increase of x. The detailed physical mechanism of the electrical transport properties in these Fe100-xCrx nanocluster-assembled granular films was also studied.

Finely controlled multimetallic nanocluster catalysts for solvent-free aerobic oxidation of hydrocarbons

PubMed Central

Takahashi, Masaki; Koizumi, Hiromu; Chun, Wang-Jae; Kori, Makoto; Imaoka, Takane; Yamamoto, Kimihisa

2017-01-01

The catalytic activity of alloy nanoparticles depends on the particle size and composition ratio of different metals. Alloy nanoparticles composed of Pd, Pt, and Au are widely used as catalysts for oxidation reactions. The catalytic activities of Pt and Au nanoparticles in oxidation reactions are known to increase as the particle size decreases and to increase on the metal-metal interface of alloy nanoparticles. Therefore, multimetallic nanoclusters (MNCs) around 1 nm in diameter have potential as catalysts for oxidation reactions. However, there have been few reports describing the preparation of uniform alloy nanoclusters. We report the synthesis of finely controlled MNCs (around 1 nm) using a macromolecular template with coordination sites arranged in a gradient of basicity. We reveal that Cu-Pt-Au MNCs supported on graphitized mesoporous carbon show catalytic activity that is 24 times greater than that of a commercially available Pt catalyst for aerobic oxidation of hydrocarbons. In addition, solvent-free aerobic oxidation of hydrocarbons to ketones at room temperature, using small amounts of a radical initiator, was achieved as a heterogeneous catalytic reaction for the first time. PMID:28782020

Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application

NASA Astrophysics Data System (ADS)

Chen, Yongdong; Wang, Jin; Liu, Chao; Li, Zhimin; Li, Gao

2016-05-01

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S(&z.dbd;O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent

Chemistry of one-dimensional metallic edge states in MoS2 nanoclusters

NASA Astrophysics Data System (ADS)

Lauritsen, J. V.; Nyberg, M.; Vang, R. T.; Bollinger, M. V.; Clausen, B. S.; Topsøe, H.; Jacobsen, K. W.; Lægsgaard, E.; Nørskov, J. K.; Besenbacher, F.

2003-03-01

Nanostructures often have unusual properties that are linked to their small size. We report here on extraordinary chemical properties associated with the edges of two-dimensional MoS2 nanoclusters, which we show to be able to hydrogenate and break up thiophene (C4H4S) molecules. By combining atomically resolved scanning tunnelling microscopy images of single-layer MoS2 nanoclusters and density functional theory calculations of the reaction energetics, we show that the chemistry of the MoS2 nanoclusters can be associated with one-dimensional metallic states located at the perimeter of the otherwise insulating nanoclusters. The new chemistry identified in this work has significant implications for an important catalytic reaction, since MoS2 nanoclusters constitute the basis of hydrotreating catalysts used to clean up sulfur-containing molecules from oil products in the hydrodesulfurization process.

Graphene-multiwall carbon nanotube-gold nanocluster composites modified electrode for the simultaneous determination of ascorbic acid, dopamine, and uric acid.

PubMed

Liu, Xiaofang; Wei, Shaping; Chen, Shihong; Yuan, Dehua; Zhang, Wen

2014-08-01

In this paper, graphene-multiwall carbon nanotube-gold nanocluster (GP-MWCNT-AuNC) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical behavior of the sensor was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The combination of GP, MWCNTs, and AuNCs endowed the electrode with a large surface area, good catalytic activity, and high selectivity and sensitivity. The linear response range for simultaneous detection of AA, DA, and UA at the sensor were 120-1,701, 2-213, and 0.7-88.3 μM, correspondingly, and the detection limits were 40, 0.67, and 0.23 μM (S/N=3), respectively. The proposed method offers a promise for simple, rapid, selective, and cost-effective analysis of small biomolecules.

pH-Induced transformation of ligated Au25 to brighter Au23 nanoclusters.

PubMed

Waszkielewicz, Magdalena; Olesiak-Banska, Joanna; Comby-Zerbino, Clothilde; Bertorelle, Franck; Dagany, Xavier; Bansal, Ashu K; Sajjad, Muhammad T; Samuel, Ifor D W; Sanader, Zeljka; Rozycka, Miroslawa; Wojtas, Magdalena; Matczyszyn, Katarzyna; Bonacic-Koutecky, Vlasta; Antoine, Rodolphe; Ozyhar, Andrzej; Samoc, Marek

2018-05-01

Thiolate-protected gold nanoclusters have recently attracted considerable attention due to their size-dependent luminescence characterized by a long lifetime and large Stokes shift. However, the optimization of nanocluster properties such as the luminescence quantum yield is still a challenge. We report here the transformation of Au25Capt18 (Capt labels captopril) nanoclusters occurring at low pH and yielding a product with a much increased luminescence quantum yield which we have identified as Au23Capt17. We applied a simple method of treatment with HCl to accomplish this transformation and we characterized the absorption and emission of the newly created ligated nanoclusters as well as their morphology. Based on DFT calculations we show which Au nanocluster size transformations can lead to highly luminescent species such as Au23Capt17.

Thinning and opening of carbon nanotubes by oxidation using carbon dioxide

NASA Astrophysics Data System (ADS)

Tsang, S. C.; Harris, P. J. F.; Green, M. L. H.

1993-04-01

THE discovery1 and bulk synthesis2 of carbon nanotubes has stimulated great interest. It has been suggested that these structures may have useful electronic3-5 and mechanical6 properties, and these might be modified by introducing foreign materials into the nanotubes. But the tubes are invariably capped at the ends. Ajayan and lijima7 have succeeded in drawing molten material (lead or one of its compounds) into the tubes by heating them in the presence of lead and oxygen; less than 1% of the tubes in the sample studied could be filled in this way. Here we report that heating in carbon dioxide gas can result in the partial or complete destruction of the tube caps and stripping of the outer layers to produce thinner tubes. In some cases, we have thinned the extremity of tubes to a single layer. The opened tubes can be regarded as nanoscale test-tubes for adsorption of other molecules, and this controlled method of thinning may allow studies of the properties of single tubes.

Stability of nanoclusters in an oxide dispersion strengthened alloy under neutron irradiation

DOE PAGES

Liu, Xiang; Miao, Yinbin; Wu, Yaqiao; ...

2017-06-01

In this paper, we report atom probe tomography results of the nanoclusters in a neutron-irradiated oxide dispersion strengthened alloy. Following irradiation to 5 dpa at target temperatures of 300 °C and 450 °C, fewer large nanoclusters were found and the residual nanoclusters tend to reach an equilibrium Guinier radius of 1.8 nm. With increasing dose, evident decrease in peak oxygen and titanium (but not yttrium) concentrations in the nanoclusters was observed, which was explained by atomic weight, solubility, diffusivity, and chemical bonding arguments. Finally, the chemical modifications indicate the equilibrium size is indeed a balance of two competing processes: radiationmore » enhanced diffusion and collisional dissolution.« less

Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application.

PubMed

Chen, Yongdong; Wang, Jin; Liu, Chao; Li, Zhimin; Li, Gao

2016-05-21

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S([double bond, length as m-dash]O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.

A DFT study for the structural and electronic properties of Zn m Se n nanoclusters

NASA Astrophysics Data System (ADS)

Yadav, Phool Singh; Pandey, Dheeraj Kumar

2012-09-01

An ab initio study has been performed for the stability, structural and electronic properties of 19 small zinc selenide Zn m Se n ( m + n = 2-4) nanoclusters. Out of these nanoclusters, one nanocluster is found to be unstable due to its imaginary vibrational frequency. A B3LYP-DFT/6-311G(3df) method is used in the optimization of the geometries of the nanoclusters. We have calculated the zero point energy (ZPE), which is ignored by the other workers. The binding energies (BE), HOMO-LUMO gaps and bond lengths have been obtained for all the optimized nanoclusters. For the same value of ` m' and ` n', we designate the most stable structure the one, which has maximum final binding energy (FBE) per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), dipole moments and charge on atoms have been investigated for the most stable nanoclusters. For the same value of ` m' and ` n', the nanocluster containing maximum number of Se atoms is found to be most stable.

Polarization properties of fluorescent BSA protected Au25 nanoclusters.

PubMed

Raut, Sangram; Chib, Rahul; Rich, Ryan; Shumilov, Dmytro; Gryczynski, Zygmunt; Gryczynski, Ignacy

2013-04-21

BSA protected gold nanoclusters (Au25) are attracting a great deal of attention due to their unique spectroscopic properties and possible use in biophysical applications. Although there are reports on synthetic strategies, spectroscopy and applications, little is known about their polarization behavior. In this study, we synthesized the BSA protected Au25 nanoclusters and studied their steady state and time resolved fluorescence properties including polarization behavior in different solvents: glycerol, propylene glycol and water. We demonstrated that the nanocluster absorption spectrum can be separated from the extinction spectrum by subtraction of Rayleigh scattering. The nanocluster absorption spectrum is well approximated by three Gaussian components. By a comparison of the emissions from BSA Au25 clusters and rhodamine B in water, we estimated the quantum yield of nanoclusters to be higher than 0.06. The fluorescence lifetime of BSA Au25 clusters is long and heterogeneous with an average value of 1.84 μs. In glycerol at -20 °C the anisotropy is high, reaching a value of 0.35. However, the excitation anisotropy strongly depends on the excitation wavelengths indicating a significant overlap of the different transition moments. The anisotropy decay in water reveals a correlation time below 0.2 μs. In propylene glycol the measured correlation time is longer and the initial anisotropy depends on the excitation wavelength. BSA Au25 clusters, due to long lifetime and high polarization, can potentially be used in studying large macromolecules such as protein complexes with large molecular weight.

Kernel Tuning and Nonuniform Influence on Optical and Electrochemical Gaps of Bimetal Nanoclusters.

PubMed

He, Lizhong; Yuan, Jinyun; Xia, Nan; Liao, Lingwen; Liu, Xu; Gan, Zibao; Wang, Chengming; Yang, Jinlong; Wu, Zhikun

2018-03-14

Fine tuning nanoparticles with atomic precision is exciting and challenging and is critical for tuning the properties, understanding the structure-property correlation and determining the practical applications of nanoparticles. Some ultrasmall thiolated metal nanoparticles (metal nanoclusters) have been shown to be precisely doped, and even the protecting staple metal atom could be precisely reduced. However, the precise addition or reduction of the kernel atom while the other metal atoms in the nanocluster remain the same has not been successful until now, to the best of our knowledge. Here, by carefully selecting the protecting ligand with adequate steric hindrance, we synthesized a novel nanocluster in which the kernel can be regarded as that formed by the addition of two silver atoms to both ends of the Pt@Ag 12 icosohedral kernel of the Ag 24 Pt(SR) 18 (SR: thiolate) nanocluster, as revealed by single crystal X-ray crystallography. Interestingly, compared with the previously reported Ag 24 Pt(SR) 18 nanocluster, the as-obtained novel bimetal nanocluster exhibits a similar absorption but a different electrochemical gap. One possible explanation for this result is that the kernel tuning does not essentially change the electronic structure, but obviously influences the charge on the Pt@Ag 12 kernel, as demonstrated by natural population analysis, thus possibly resulting in the large electrochemical gap difference between the two nanoclusters. This work not only provides a novel strategy to tune metal nanoclusters but also reveals that the kernel change does not necessarily alter the optical and electrochemical gaps in a uniform manner, which has important implications for the structure-property correlation of nanoparticles.

Some properties of solid helium and helium nanoclusters using the effective HFD-like interaction potential: Adsorption and desorption inside carbon nanotube

NASA Astrophysics Data System (ADS)

Abbaspour, M.; Akbarzadeh, H.; Banihashemi, S. Z.; Sotoudeh, A.

2018-02-01

We have calculated the zero equation of state of solid helium using a two-body Hartree-Fock dispersion (HFD)-like potential from molecular dynamics (MD) simulation. To take many-body forces into account, our simple and accurate empirical expression is used with the HFD-like potential without requiring an expensive three-body calculation. This potential model also includes the quantum effects for helium at low temperatures. The results indicate that our effective HFD-like potential improves the prediction of the classical two-body results to get better agreement with experiment than many other two-body and three-body potentials of helium reported in the literature. We have also simulated the adsorption and desorption processes of the (He)55, (He)147, (He)309, (He)561, and (He)923 icosahedral nanoclusters confined into the different armchair and zigzag CNTs from 0 to 50 K using our effective model. We have observed an interesting phenomenon at 0 K for helium. The nanoclusters adsorb to the inner CNT wall as a melting process. But, the heavier noble gas clusters (such as Ne and Xe) show the different behavior than the He clusters. They form a multilayered solid structure into the CNT at zero temperature and adsorb into the inner wall of the CNT at higher temperatures. Our results for He clusters show that the absolute value of the adsorption energy increases as the size of the nanocluster increases. The desorption process begins at a certain temperature and represents itself by a jump in the configurational energy values. We have also investigated the structural and dynamical properties of the confined helium nanoclusters during the adsorption and desorption processes at different temperatures.

Fundamental Studies and Isolation Strategies for Metal Compound Nanoclusters

DTIC Science & Technology

2009-02-28

probe nanocluster structure, bonding and stability, metal oxide, carbide and silicide clusters with up to 50 atoms were investigated with mass...transition metal compounds (carbides, oxides, silicides ) that are expected to have high stability, an essential property for their isolation...Metal carbide, oxide and silicide nanoclusters are studied in the size range from a few up to about 300 atoms. New infrared laser spectroscopy

Spray-coated carbon nanotube thin-film transistors with striped transport channels

NASA Astrophysics Data System (ADS)

Jeong, Minho; Lee, Kunhak; Choi, Eunsuk; Kim, Ahsung; Lee, Seung-Beck

2012-12-01

We present results for the transfer characteristics of carbon nanotube thin-film transistors (CNT-TFTs) that utilize single-walled carbon nanotube thin-films prepared by direct spray-coating on the substrate. By varying the number of spray-coatings (Nsp) and the concentration of nanotubes in solution (CNT), it was possible to control the conductivity of the spray-coated nanotube thin-film from 129 to 0.1 kΩ/□. Also, by introducing stripes into the channel of the CNT-TFT, and thereby reducing the number of metallic percolation paths between source and drain, it was possible to enhance the on/off current ratio 1000-fold, from 10 to 104, demonstrating that it may be possible to utilize spray-coating as a method to fabricate CNT-TFTs for large area switching array applications.

Adsorption of Bromine on Gold Nanoclusters

NASA Astrophysics Data System (ADS)

Salvo, Christopher; Keagy, Josiah; Yarmoff, Jory

Small metal nanoclusters are extremely effective as catalysts, with rates that rival those of enzymes in biological systems. The first step in a catalytic reaction is the adsorption of a precursor molecule. The neutralization of alkali projectiles during low energy ion scattering (LEIS), which is acutely sensitive to the local electrostatic potential a few Å's above the surface, is used here to probe Au nanoclusters grown on SiO2 as they are reacted with Br2. Previous work had demonstrated very efficient neutralization in scattering from small catalytically active Au clusters, which was interpreted as an indication that the bare clusters are negatively charged. X-ray photoelectron spectroscopy and LEIS show little or no Br signal after exposing SiO2 and Au foil to Br2, suggesting that adsorption does not occur because the Br-Br bond does not break. Dissociative adsorption occurs rapidly, however, when small Au nanoclusters are reacted with Br2. 1.5 keV Na+ ions scattered from the Au clusters show a decrease in the neutralization probability as Br is reacted, indicating that adsorption results in charge being transferred from the cluster to the Br adatom. This material is based upon work supported by the National Science Foundation under CHE - 1611563.

Au38Cu1(2-PET)24 nanocluster: synthesis, enantioseparation and luminescence.

PubMed

Kazan, Rania; Zhang, Bei; Bürgi, Thomas

2017-06-20

A CuAu 38 bimetallic nanocluster was synthesized by adding a single copper atom to the Au 38 (2-PET) 24 nanocluster. The absence of Cu x Au 38-x (2-PET) 24 doped species was demonstrated by MALDI-TOF mass spectrometry. A separation of bimetallic clusters was attained for the first time where isomers of the E2 enantiomer of the Au 38 Cu 1 (2-PET) 24 adduct were successfully isolated from their parent cluster using chiral HPLC. The CD of the isolated isomers revealed a change in their electronic structure upon copper addition. The luminescence of the Au 38 Cu 1 adduct is significantly enhanced in comparison with the parent Au 38 nanocluster. The stability of the newly formed adduct is strongly dependent on the coexistence of the Au 38 nanoclusters.

Growth of Pd Nanoclusters on Single-Layer Graphene on Cu(111)

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

Soy, Esin; Guisinger, Nathan P.; Trenary, Michael

We report scanning tunneling microscopy results on the nucleation and growth of Pd nanoclusters on a single layer of graphene on the Cu(111) surface. The shape, organization, and structural evolution of the Pd nanoclusters were investigated using two different growth methods, continuous and stepwise. The size and shape of the formed nanoclusters were found to greatly depend on the growth technique used. The size and density of spherical Pd nanoclusters increased with increasing coverage during stepwise deposition as a result of coarsening of existing clusters and continued nucleation of new clusters. In contrast, continuous deposition gave rise to well-defined triangularmore » Pd clusters as a result of anisotropic growth on the graphene surface. Exposure to ethylene caused a decrease in the size of the Pd clusters. As a result, this is attributed to the exothermic formation of ethylidyne on the cluster surfaces and an accompanying weakening of the Pd–Pd bonding.« less

Growth of Pd Nanoclusters on Single-Layer Graphene on Cu(111)

DOE PAGES

Soy, Esin; Guisinger, Nathan P.; Trenary, Michael

2017-07-05

We report scanning tunneling microscopy results on the nucleation and growth of Pd nanoclusters on a single layer of graphene on the Cu(111) surface. The shape, organization, and structural evolution of the Pd nanoclusters were investigated using two different growth methods, continuous and stepwise. The size and shape of the formed nanoclusters were found to greatly depend on the growth technique used. The size and density of spherical Pd nanoclusters increased with increasing coverage during stepwise deposition as a result of coarsening of existing clusters and continued nucleation of new clusters. In contrast, continuous deposition gave rise to well-defined triangularmore » Pd clusters as a result of anisotropic growth on the graphene surface. Exposure to ethylene caused a decrease in the size of the Pd clusters. As a result, this is attributed to the exothermic formation of ethylidyne on the cluster surfaces and an accompanying weakening of the Pd–Pd bonding.« less

Electron localization in rod-shaped triicosahedral gold nanocluster

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

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

Electron localization in rod-shaped triicosahedral gold nanocluster

DOE PAGES

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.; ...

2017-05-30

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

Split-GFP: SERS Enhancers in Plasmonic Nanocluster Probes.

PubMed

Chung, Taerin; Koker, Tugba; Pinaud, Fabien

2016-09-08

The assembly of plasmonic metal nanoparticles into hot spot surface-enhanced Raman scattering (SERS) nanocluster probes is a powerful, yet challenging approach for ultrasensitive biosensing. Scaffolding strategies based on self-complementary peptides and proteins are of increasing interest for these assemblies, but the electronic and the photonic properties of such hybrid nanoclusters remain difficult to predict and optimize. Here, split-green fluorescence protein (sGFP) fragments are used as molecular glue and the GFP chromophore is used as a Raman reporter to assemble a variety of gold nanoparticle (AuNP) clusters and explore their plasmonic properties by numerical modeling. It is shown that GFP seeding of plasmonic nanogaps in AuNP/GFP hybrid nanoclusters increases near-field dipolar couplings between AuNPs and provides SERS enhancement factors above 10 8 . Among the different nanoclusters studied, AuNP/GFP chains allow near-infrared SERS detection of the GFP chromophore imidazolinone/exocyclic CC vibrational mode with theoretical enhancement factors of 10 8 -10 9 . For larger AuNP/GFP assemblies, the presence of non-GFP seeded nanogaps between tightly packed nanoparticles reduces near-field enhancements at Raman active hot spots, indicating that excessive clustering can decrease SERS amplifications. This study provides rationales to optimize the controlled assembly of hot spot SERS nanoprobes for remote biosensing using Raman reporters that act as molecular glue between plasmonic nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure and electronic properties of a thiolate-protected Au24 nanocluster

NASA Astrophysics Data System (ADS)

Das, Anindita; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Rosi, Nathaniel L.; Jin, Rongchao

2014-05-01

Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''.Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''. Electronic supplementary information (ESI) available: Experimental and supporting Fig. S1-S3. CCDC NUMBER(1000102). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr01350f

RF heating of nanoclusters for cancer therapy

NASA Astrophysics Data System (ADS)

Letfullin, Renat R.; Letfullin, Alla R.; George, Thomas F.

2015-03-01

Nanodrugs selectively delivered to a tumor site can be activated by radiation for drug release, or nanoparticles (NPs) can be used as a drug themselves by producing biological damage in cancer cells through thermal, mechanical ablations or charged particle emission. Radio-frequency (RF) waves have an excellent ability to penetrate into the human body without causing healthy tissue damage, which provides a great opportunity to activate/heat NPs delivered inside the body as a contrast agent for diagnosis and treatment purposes. However the heating of NPs in the RF range of the spectrum is controversial in the research community because of the low power load of RF waves and low absorption of NPs in the RF range. To resolve these weaknesses in the RF activation of NPs and dramatically increase absorption of contrast agents in tumor, we suggest aggregating the nanoclusters inside or on the surface of the cancer cells. We simulate space distribution of temperature changes inside and outside metal and dielectric nanopraticles/nanoclusters, determine the number of nanoparticles needed to form a cluster, and estimate the thermal damage area produced in surrounding medium by nanopraticles/nanoclusters heated in the RF field.

Influence of the size and charge of gold nanoclusters on complexation with siRNA: a molecular dynamics simulation study.

PubMed

Mudedla, Sathish Kumar; Azhagiya Singam, Ettayapuram Ramaprasad; Balamurugan, Kanagasabai; Subramanian, Venkatesan

2015-11-11

The complexation of small interfering RNA (siRNA) with positively charged gold nanoclusters has been studied in the present investigation with the help of classical molecular dynamics and steered molecular dynamics simulations accompanied by free energy calculations. The results show that gold nanoclusters form a stable complex with siRNA. The wrapping of siRNA around the gold nanocluster depends on the size and charge on the surface of the gold cluster. The binding pattern of the gold nanocluster with siRNA is also influenced by the presence of another cluster. The interaction between the positively charged amines in the gold nanocluster and the negatively charged phosphate group in the siRNA is responsible for the formation of complexes. The binding free energy value increases with the size of the gold cluster and the number of positive charges present on the surface of the gold nanocluster. The results reveal that the binding energy of small gold nanoclusters increases in the presence of another gold nanocluster while the binding of large gold nanoclusters decreases due to the introduction of another gold nanocluster. Overall, the findings have clearly demonstrated the effect of size and charge of gold nanoclusters on their interaction pattern with siRNA.

The theoretical and empirical basis for understanding the impact of thinning on carbon stores in forests

Treesearch

Mark E. Harmon

2013-01-01

Th inning of forests has been proposed as a means to increase the carbon stores of forests. Th e justifi cation often offered is that thinning increases stand productivity, which in turn leads to higher carbon stores. While thinning of forests clearly increases the growth of residual trees and increases the amount of harvested carbon compared to an unthinned stand,...

Thermal annealing and SHI irradiation induced modifications in sandwiched structured Carbon-gold-Carbon (a-C/Au/a-C) nanocomposite thin film

NASA Astrophysics Data System (ADS)

Singh, S. K.; Singhal, R.

2017-09-01

In the present work, we study the annealing and swift heavy ion (SHI) beam induced modifications in the optical and structural properties of sandwiched structured Carbon-gold-Carbon (a-C/Au/a-C) nanocomposite (NCs) thin films. The NCs thin films were synthesized by electron-beam evaporation technique at room temperature with ∼30 nm thickness for both carbon layer and ∼6 nm for gold layer. Gold-carbon NCs thin films were annealed in the presence of argon at a temperature of 500 °C, 600 °C and 750 °C. The NCs thin films were also irradiated with 90 MeV Ni ions beam with different ion fluences in the range from 3 × 1012, 6 × 1012 and 1 × 1013 ions/cm2. Surface plasmon resonance (SPR) of Au nanoparticles are not observed in the pristine film but, after annealing at temperature of 600 °C and 750 °C, it was clearly seen at ∼534 nm as confirmed by UV-visible absorption spectroscopy. 90 MeV Ni irradiated thin film at the fluence of 1 × 1013 ions/cm2 also show strong absorption band at ∼534 nm. The growth and size of Au nanoparticle for pristine and 90 MeV Ni ion irradiated thin film with fluence of 1 × 1013 ions/cm2, were estimated by Transmission electron microscopy (TEM) images with the bi-model distribution. The size of the gold nanoparticle (NPs) was found to be ∼4.5 nm for the pristine film and ∼5.4 nm for the irradiated film at a fluence of 1 × 1013 ions/cm2. The thickness and metal atomic fraction in carbon matrix were estimated by Rutherford backscattering spectroscopy (RBS). The effect of annealing as well as heavy ion irradiation on D and G band of carbon matrix were studied by Raman spectroscopy.

Polyethyleneimine Capped Silver Nanoclusters as Efficient Antibacterial Agents.

PubMed

Xu, Dong; Wang, Qingyun; Yang, Tao; Cao, Jianzhong; Lin, Qinlu; Yuan, Zhiqin; Li, Le

2016-03-18

Development of efficient antibacterial agents is critical for human health. In the present study, we investigated the antibacterial activity of polyethyleneimine (PEI)-capped silver nanoclusters (PEI-AgNCs), based on the fact that nanoclusters normally have higher surface-to-volume ratios than traditional nanomaterials and PEI itself has a strong antimicrobial capacity. We synthesized stable silver nanoclusters by altering PEI molecular weight from 0.6 kDa to 25 kDa and characterized them by UV-Vis absorption and fluorescence spectroscopy and high resolution transmission electron microscopy. The sizes of AgNCs were around 2 nm in diameter and were little influenced by the molecular weight of PEIs. The antibacterial abilities of the four PEI-AgNCs were explored on agar plate and in liquid systems. Our results revealed that the antibacterial activity of PEI-AgNCs is excellent and the reduction of PEI molecular weight could result in the increased antibacterial capacity of PEI-AgNCs. Such proposed new materials might be useful as efficient antibacterial agents in practical clinical applications.

Applications of thin carbon coatings and films in injection molding

NASA Astrophysics Data System (ADS)

Cabrera, Eusebio Duarte

In this research, the technical feasibility of two novel applications of thin carbon coatings is demonstrated. The first application consists of using thin carbon coatings on molds for molding ultra-thin plastic parts (<0.5 mm thickness) with lower pressures by promoting wall slip. The second application consists of a new approach to provide electromagnetic interference (EMI) shielding for plastic parts using in mold coated nanoparticle thin films or nanopapers to create a conductive top layer. During this research, the technical feasibility of a new approach was proven which provides injection molding of ultra-thin parts at lower pressures, without the need of fast heating/fast cooling or other expensive mold modification. An in-house developed procedure by other members of our group, was employed for coating the mold surface using chemical vapor deposition (CVD) resulting in a graphene coating with carbide bonding to the mold surface. The coating resulted in a significant decrease of surface friction and consequently easiness of flow when compared to their uncoated counterparts. Thermoplastic polymers and their composites are a very attractive alternative but are hindered by the non-conductive nature of polymers. There are two general approaches used to date to achieve EMI shielding for plastic products. One is to spray a conductive metal coating onto the plastic surface forming a layer that must maintain its shielding effectiveness (SE), and its adhesion to the plastic throughout the expected life of the product. However, metal coatings add undesirable weight and tend to corrode over time. Furthermore, scratching the coating may create shielding failure; therefore, a protective topcoat may be required. The other approach is to use polymer composites filled with conductive fillers such as carbon black (CB), carbon nanofiber (CNF), and carbon nanotube (CNT). While conductive fillers may increase the electrical conductivity of polymer composites, the loading of

Microstructural properties and evolution of nanoclusters in liquid Si during a rapid cooling process

NASA Astrophysics Data System (ADS)

Gao, T.; Hu, X.; Li, Y.; Tian, Z.; Xie, Q.; Chen, Q.; Liang, Y.; Luo, X.; Ren, L.; Luo, J.

2017-11-01

The formation of amorphous structures in Si during the rapid quenching process was studied based on molecular dynamics simulation by using the Stillinger-Weber potential. The evolution characteristics of nanoclusters during the solidification were analyzed by several structural analysis methods. The amorphous Si has been formed with many tetrahedral clusters and few nanoclusters. During the solidification, tetrahedral polyhedrons affect the local structures by their different positions and connection modes. The main kinds of polyhedrons randomly linked with one another to form an amorphous network structures in the system. The structural evolution of crystal nanocluster demonstrates that the nanocluster has difficulty to growth because of the high cooling rate of 1012 K/s.

Novel and remarkable enhanced-fluorescence system based on gold nanoclusters for detection of tetracycline.

PubMed

Yang, Xiaoming; Zhu, Shanshan; Dou, Yao; Zhuo, Yan; Luo, Yawen; Feng, Yuanjiao

2014-05-01

Tetracycline and Eu(3+), while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. Gold nanoclusters (AuNCs), emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu(3+)-Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01-5 μM, with a detection limit of 4 nM at a signal-to-noise ratio of 3. Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. Interestingly, this system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence. © 2013 Published by Elsevier B.V.

Mass spectrometric identification of Au68(SR)34 molecular gold nanoclusters with 34-electron shell closing.

PubMed

Dass, Amala

2009-08-26

The molecular formula Au(68)(SCH(2)CH(2)Ph)(34) has been assigned to the 14 kDa nanocluster using MALDI-TOF mass spectrometry. The 34-electron shell closing in a macroscopically obtained thiolated gold nanocluster is demonstrated. The Au(68) nanocluster is predicted to have a 49 atom Marks decahedral core with 19 inner core atoms and 30 outer atoms chelating with the staple motifs. The nanoclusters' predicted formulation is [Au](19+30) [Au(SR)(2)](11) [Au(2)(SR)(3)](4).

Self-Assembled Superparamagnetic Iron Oxide Nanoclusters for Universal Cell Labeling and MRI

NASA Astrophysics Data System (ADS)

Chen, Shuzhen; Zhang, Jun; Jiang, Shengwei; Lin, Gan; Luo, Bing; Yao, Huan; Lin, Yuchun; He, Chengyong; Liu, Gang; Lin, Zhongning

2016-05-01

Superparamagnetic iron oxide (SPIO) nanoparticles have been widely used in a variety of biomedical applications, especially as contrast agents for magnetic resonance imaging (MRI) and cell labeling. In this study, SPIO nanoparticles were stabilized with amphiphilic low molecular weight polyethylenimine (PEI) in an aqueous phase to form monodispersed nanocomposites with a controlled clustering structure. The iron-based nanoclusters with a size of 115.3 ± 40.23 nm showed excellent performance on cellular uptake and cell labeling in different types of cells, moreover, which could be tracked by MRI with high sensitivity. The SPIO nanoclusters presented negligible cytotoxicity in various types of cells as detected using MTS, LDH, and flow cytometry assays. Significantly, we found that ferritin protein played an essential role in protecting stress from SPIO nanoclusters. Taken together, the self-assembly of SPIO nanoclusters with good magnetic properties provides a safe and efficient method for universal cell labeling with noninvasive MRI monitoring capability.

Carbon nanotube thin film strain sensors: comparison between experimental tests and numerical simulations

NASA Astrophysics Data System (ADS)

Lee, Bo Mi; Loh, Kenneth J.

2017-04-01

Carbon nanotubes can be randomly deposited in polymer thin film matrices to form nanocomposite strain sensors. However, a computational framework that enables the direct design of these nanocomposite thin films is still lacking. The objective of this study is to derive an experimentally validated and two-dimensional numerical model of carbon nanotube-based thin film strain sensors. This study consisted of two parts. First, multi-walled carbon nanotube (MWCNT)-Pluronic strain sensors were fabricated using vacuum filtration, and their physical, electrical, and electromechanical properties were evaluated. Second, scanning electron microscope images of the films were used for identifying topological features of the percolated MWCNT network, where the information obtained was then utilized for developing the numerical model. Validation of the numerical model was achieved by ensuring that the area ratios (of MWCNTs relative to the polymer matrix) were equivalent for both the experimental and modeled cases. Strain sensing behavior of the percolation-based model was simulated and then compared to experimental test results.

Carbon nanotube network thin-film transistors on flexible/stretchable substrates

DOEpatents

Takei, Kuniharu; Takahashi, Toshitake; Javey, Ali

2016-03-29

This disclosure provides systems, methods, and apparatus for flexible thin-film transistors. In one aspect, a device includes a polymer substrate, a gate electrode disposed on the polymer substrate, a dielectric layer disposed on the gate electrode and on exposed portions of the polymer substrate, a carbon nanotube network disposed on the dielectric layer, and a source electrode and a drain electrode disposed on the carbon nanotube network.

Spectroscopy of metal "superatom" nanoclusters and high-Tc superconducting pairing

NASA Astrophysics Data System (ADS)

Halder, Avik; Kresin, Vitaly V.

2015-12-01

A unique property of metal nanoclusters is the "superatom" shell structure of their delocalized electrons. The electronic shell levels are highly degenerate and therefore represent sharp peaks in the density of states. This can enable exceptionally strong electron pairing in certain clusters composed of tens to hundreds of atoms. In a finite system, such as a free nanocluster or a nucleus, pairing is observed most clearly via its effect on the energy spectrum of the constituent fermions. Accordingly, we performed a photoionization spectroscopy study of size-resolved aluminum nanoclusters and observed a rapid rise in the near-threshold density of states of several clusters (A l37 ,44 ,66 ,68 ) with decreasing temperature. The characteristics of this behavior are consistent with compression of the density of states by a pairing transition into a high-temperature superconducting state with Tc≳100 K. This value exceeds that of bulk aluminum by two orders of magnitude. These results highlight the potential of novel pairing effects in size-quantized systems and the possibility to attain even higher critical temperatures by optimizing the particles' size and composition. As a new class of high-temperature superconductors, such metal nanocluster particles are promising building blocks for high-Tc materials, devices, and networks.

Effects of thinning on aboveground carbon sequestration by a 45-year-old eastern white pine plantation: A case study

Treesearch

W. Henry McNab

2012-01-01

Aboveground carbon sequestration by a 45-year-old plantation of eastern white pines was determined in response to thinning to three levels of residual basal area: (1) Control (no thinning), (2) light thinning to 120 feet2/acre and (3) heavy thinning to 80 feet2/acre. After 11 years carbon stocks were lowest on the heavily...

On the possibility of controlling the hydrophilic/hydrophobic characteristics of toroid Mo138 nanocluster polyoxometalates

NASA Astrophysics Data System (ADS)

Grzhegorzhevskii, K. V.; Adamova, L. V.; Eremina, E. V.; Ostroushko, A. A.

2017-03-01

The possibility of changing the hydrophilic (polar) surfaces of toroid nanocluster polyoxomolibdates to hydrophobic (nonpolar) surfaces via the modification of Mo138 nanoclusters by surfactant molecules (dodecylpyridinium chloride) as a result of the interaction between these compounds in solutions is demonstrated. Benzene and methanol are used as molecular probes (indicators of the condition of nanocluster surfaces). Comparative characteristics of the equilibrium sorption of benzene and methanol vapors on the initial and modified surfaces of the solid polyoxometalate, and data on the sorption of organic molecules on the surfaces of Rhodamine B-modified nanoclusters of the toroid (Mo138) and keplerate (Mo132) types are obtained.

A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

NASA Astrophysics Data System (ADS)

Yang, Qi; Lan, Fang; Yi, Qiangying; Wu, Yao; Gu, Zhongwei

2015-10-01

A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c5nr05800g

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

1998-01-01

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

Optimal packing size of non-ligated CdSe nanoclusters for microstructure synthesis

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

Tefera, Anteneh G.; Mochena, Mogus D.; Johnson, Elijah

2014-09-14

Structural and electrostatic properties of nanoclusters of CdSe of diameter 1–2 nm are studied with first principle calculations to determine the optimal size for synthesizing microstructures. Based on robustness of the core structure, i.e., the retention of tetrahedral geometry, hexagonal ring structure, and overall wu{sup ¨}rtzite structure to surface relaxations, we conclude that nanoclusters of ~2 nm diameter are the best candidates to form a dense microstructure with minimal interstitial space. Se-terminated surfaces retain a zigzag structure as Se atoms are pulled out and Cd atoms are pulled in due to relaxation, therefore, are best suited for inter-nanocluster formations.

Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols

NASA Astrophysics Data System (ADS)

Li, Lun; Dou, Liguang; Zhang, Hui

2014-03-01

M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h-1) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity

Carbon Nanotube Thin Film Transistors for Flat Panel Display Application.

PubMed

Liang, Xuelei; Xia, Jiye; Dong, Guodong; Tian, Boyuan; Peng, Lianmao

2016-12-01

Carbon nanotubes (CNTs) are promising materials for both high performance transistors for high speed computing and thin film transistors for macroelectronics, which can provide more functions at low cost. Among macroelectronics applications, carbon nanotube thin film transistors (CNT-TFT) are expected to be used soon for backplanes in flat panel displays (FPDs) due to their superior performance. In this paper, we review the challenges of CNT-TFT technology for FPD applications. The device performance of state-of-the-art CNT-TFTs are compared with the requirements of TFTs for FPDs. Compatibility of the fabrication processes of CNT-TFTs and current TFT technologies are critically examined. Though CNT-TFT technology is not yet ready for backplane production line of FPDs, the challenges can be overcome by close collaboration between research institutes and FPD manufacturers in the short term.

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

1998-09-29

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

Virus templated plasmonic nanoclusters with icosahedral symmetry via directed assembly

NASA Astrophysics Data System (ADS)

Ratna, Banahalli; Fontana, Jake; Dressick, Walter; Phelps, Jamie; Johnson, John; Sampson, Travian; Rendell, Ronald; Soto, Carissa

2015-03-01

Controlling the spatial and orientational order of plasmonic nanoparticles may lead to structures with novel electromagnetic properties and applications such as sub-wavelength imaging and ultra-sensitive chemical sensors. Here we report the directed assembly of three-dimensional, icosahedral plasmonic nanoclusters with resonances at visible wavelengths. We show using transmission electron microcopy and in situ dynamic light scattering the nanoclusters consist of twelve gold nanospheres attached to thiol groups at predefined locations on the surface of a genetically engineered cowpea mosaic virus with icosahedral symmetry. We measured the bulk absorbance from aqueous suspensions of nanoclusters and reproduced the major features of the spectrum using finite-element simulations. Furthermore, because the viruses are easily produced in gram quantities the directed assembly approach is capable of high-throughput, providing a strategy to realize large quantities for applications. NRL summer intern under the HBCU/MI Summer Research Program.

Large-scale complementary macroelectronics using hybrid integration of carbon nanotubes and IGZO thin-film transistors.

PubMed

Chen, Haitian; Cao, Yu; Zhang, Jialu; Zhou, Chongwu

2014-06-13

Carbon nanotubes and metal oxide semiconductors have emerged as important materials for p-type and n-type thin-film transistors, respectively; however, realizing sophisticated macroelectronics operating in complementary mode has been challenging due to the difficulty in making n-type carbon nanotube transistors and p-type metal oxide transistors. Here we report a hybrid integration of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors to achieve large-scale (>1,000 transistors for 501-stage ring oscillators) complementary macroelectronic circuits on both rigid and flexible substrates. This approach of hybrid integration allows us to combine the strength of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors, and offers high device yield and low device variation. Based on this approach, we report the successful demonstration of various logic gates (inverter, NAND and NOR gates), ring oscillators (from 51 stages to 501 stages) and dynamic logic circuits (dynamic inverter, NAND and NOR gates).

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

PubMed

Liu, Lichen; Corma, Avelino

2018-05-23

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

Concentrated dispersions of equilibrium protein nanoclusters that reversibly dissociate into active monomers

NASA Astrophysics Data System (ADS)

Truskett, Thomas M.; Johnston, Keith; Maynard, Jennifer; Borwankar, Ameya; Miller, Maria; Wilson, Brian; Dinin, Aileen; Khan, Tarik; Kaczorowski, Kevin

2012-02-01

Stabilizing concentrated protein solutions is of wide interest in drug delivery. However, a major challenge is how to reliably formulate concentrated, low viscosity (i.e., syringeable) solutions of biologically active proteins. Unfortunately, proteins typically undergo irreversible aggregation at intermediate concentrations of 100-200 mg/ml. In this talk, I describe how they can effectively avoid these intermediate concentrations by reversibly assembling into nanoclusters. Nanocluster assembly is achieved by balancing short-ranged, cosolute-induced attractions with weak, longer-ranger electrostatic repulsions near the isoelectric point. Theory predicts that native proteins are stabilized by a self-crowding mechanism within the concentrated environment of the nanoclusters, while weak cluster-cluster interactions can result in colloidally-stable dispersions with moderate viscosities. I present experimental results where this strategy is used to create concentrated antibody dispersions (up to 260 mg/ml) comprising nanoclusters of proteins [monoclonal antibody 1B7, polyclonal sheep Immunoglobin G and bovine serum albumin], which upon dilution in vitro or administration in vivo, are conformationally stable and retain activity.

Theoretical Studies of Nanoclusters (Briefing Charts)

DTIC Science & Technology

2015-07-23

nanoclusters. However, scanning transmission electron microscopy ( STEM ) measures show cluster inversion occurred to produce MgyCux(!) a) copper atoms b...methane (née CLL -1) as a potential explosive ingredient: a theoretical study”, Propellants, Explosives, Pyrotechnics 38, 9-13 (2013). Jesus Paulo L

Binder-free manganese oxide/carbon nanomaterials thin film electrode for supercapacitors.

PubMed

Wang, Ning; Wu, Chuxin; Li, Jiaxin; Dong, Guofa; Guan, Lunhui

2011-11-01

A ternary thin film electrode was created by coating manganese oxide onto a network composed of single-walled carbon nanotubes and single-walled carbon nanohorns. The electrode exhibited a porous structure, which is a promising architecture for supercapacitors applications. The maximum specific capacitances of 357 F/g for total electrode at 1 A/g were achieved in 0.1 M Na(2)SO(4) aqueous solution.

Galectin-1 dimers can scaffold Raf-effectors to increase H-ras nanoclustering

PubMed Central

Blaževitš, Olga; Mideksa, Yonatan G.; Šolman, Maja; Ligabue, Alessio; Ariotti, Nicholas; Nakhaeizadeh, Hossein; Fansa, Eyad K.; Papageorgiou, Anastassios C.; Wittinghofer, Alfred; Ahmadian, Mohammad R.; Abankwa, Daniel

2016-01-01

Galectin-1 (Gal-1) dimers crosslink carbohydrates on cell surface receptors. Carbohydrate-derived inhibitors have been developed for cancer treatment. Intracellularly, Gal-1 was suggested to interact with the farnesylated C-terminus of Ras thus specifically stabilizing GTP-H-ras nanoscale signalling hubs in the membrane, termed nanoclusters. The latter activity may present an alternative mechanism for how overexpressed Gal-1 stimulates tumourigenesis. Here we revise the current model for the interaction of Gal-1 with H-ras. We show that it indirectly forms a complex with GTP-H-ras via a high-affinity interaction with the Ras binding domain (RBD) of Ras effectors. A computationally generated model of the Gal-1/C-Raf-RBD complex is validated by mutational analysis. Both cellular FRET as well as proximity ligation assay experiments confirm interaction of Gal-1 with Raf proteins in mammalian cells. Consistently, interference with H-rasG12V-effector interactions basically abolishes H-ras nanoclustering. In addition, an intact dimer interface of Gal-1 is required for it to positively regulate H-rasG12V nanoclustering, but negatively K-rasG12V nanoclustering. Our findings suggest stacked dimers of H-ras, Raf and Gal-1 as building blocks of GTP-H-ras-nanocluster at high Gal-1 levels. Based on our results the Gal-1/effector interface represents a potential drug target site in diseases with aberrant Ras signalling. PMID:27087647

Growth of silicon nanoclusters in thermal silicon dioxide under annealing in an atmosphere of nitrogen

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

Ivanova, E. V., E-mail: Ivanova@mail.ioffe.ru; Sitnikova, A. A.; Aleksandrov, O. V.

2016-06-15

It is found for the first time that silicon nanoclusters are formed in the surface layer of thermal silicon dioxide under high-temperature annealing (T = 1150°C) in dried nitrogen. Analysis of the cathodoluminescence spectra shows that an imperfect surface layer appears upon such annealing of silicon dioxide, with silicon nanoclusters formed in this layer upon prolonged annealing. Transmission electron microscopy demonstrated that the silicon clusters are 3–5.5 nm in size and lie at a depth of about 10 nm from the surface. Silicon from the thermal film of silicon dioxide serves as the material from which the silicon nanoclusters aremore » formed. This method of silicon-nanocluster formation is suggested for the first time.« less

Synthesizing a nano-composite of BSA-capped Au nanoclusters/graphitic carbon nitride nanosheets as a new fluorescent probe for dopamine detection.

PubMed

Guo, Xinrong; Wu, Fangying; Ni, Yongnian; Kokot, Serge

2016-10-26

A strong red fluorescent nanocomposite, consisting of graphite-like carbon nitride nanosheets (g-C 3 N 4 NSs) and serum albumin-capped Au nanoclusters (AuNCs), was synthesized. Dopamine (DA) can quench the red fluorescence of the nanocomposite, based on the Forster resonance energy transfer (FRET) mechanism. In this quenching process, the energy is transferred from the fluorescent g-C 3 N 4 NSs-AuNCs to the oxidized DA quinine molecules (DA is easily oxidated to form DA quinine in air). The red fluorescence emission at 420 nm decreases dramatically and the quenching ratio (F 0 - F)/F 0 is linearly related to the concentration of DA in the range of 0.05-8.0 μmol L -1 with a detection limit of 0.018 μmol L -1  (S/N = 3). Additionally, this sensor has a potential of application to assay the DA in the real samples, such as human serum and human urine. Copyright © 2016 Elsevier B.V. All rights reserved.

A hybrid DNA-templated gold nanocluster for enhanced enzymatic reduction of oxygen

DOE PAGES

Chakraborty, Saumen; Babanova, Sofia; Rocha, Reginaldo C.; ...

2015-08-19

We report the synthesis and characterization of a new DNA-templated gold nanocluster (AuNC) of ~1 nm in diameter and possessing ~7 Au atoms. When integrated with bilirubin oxidase (BOD) and single walled carbon nanotubes (SWNTs), the AuNC acts as an enhancer of electron transfer (ET) and lowers the overpotential of electrocatalytic oxygen reduction reaction (ORR) by ~15 mV as compared to the enzyme alone. In addition, the presence of AuNC causes significant enhancements in the electrocatalytic current densities at the electrode. Control experiments show that such enhancement of ORR by the AuNC is specific to nanoclusters and not to plasmonicmore » gold particles. Rotating ring disk electrode (RRDE) measurements confirm 4e– reduction of O 2 to H 2O with minimal production of H 2O 2, suggesting that the presence of AuNC does not perturb the mechanism of ORR catalyzed by the enzyme. This unique role of the AuNC as enhancer of ET at the enzyme-electrode interface makes it a potential candidate for the development of cathodes in enzymatic fuel cells, which often suffer from poor electronic communication between the electrode surface and the enzyme active site. In conclusion, the AuNC displays phosphorescence with large Stokes shift and microsecond lifetime.« less

Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.

PubMed

Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

2014-07-07

Nanohybrids consisting of Au nanocluster and polythiophene nanowire assemblies exhibit unique thermal-responsive optical behaviors and charge-transfer controlled magnetic and optoelectronic properties. The ultrasmall Au nanocluster enhanced photoabsorption and conductivity effectively improves the photocurrent of nanohybrid based photovoltaics, leading to an increase of power conversion efficiency by 14 % under AM 1.5 illumination. In addition, nanohybrids exhibit electric field controlled spin resonance and magnetic field sensing behaviors, which open up the potential of charge-transfer complex system where the magnetism and optoelectronics interact. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Platinum-gold nanoclusters as catalyst for direct methanol fuel cells.

PubMed

Giorgi, L; Giorgi, R; Gagliardi, S; Serra, E; Alvisi, M; Signore, M A; Piscopiello, E

2011-10-01

Nanosized platinum-gold alloys clusters have been deposited on gas diffusion electrode by sputter deposition. The deposits were characterized by FE-SEM, TEM and XPS in order to verify the formation of alloy nanoparticles and to study the influence of deposition technique on the nanomorphology. The deposition by sputtering process allowed a uniform distribution of metal particles on porous surface of carbon supports. Typical island growth mode was observed with the formation of a dispersed metal nanoclusters (mean size about 5 nm). Cyclic voltammetry was used to determine the electrochemical active surface and the electrocatalytic performance of the PtAu electrocatalysts for methanol oxidation reaction. The data were re-calculated in the form of mass specific activity (MSA). The sputter-catalyzed electrodes showed higher performance and stability compared to commercial catalysts.

Protein-templated gold nanoclusters based sensor for off-on detection of ciprofloxacin with a high selectivity.

PubMed

Chen, Zhanguang; Qian, Sihua; Chen, Junhui; Cai, Jie; Wu, Shuyan; Cai, Ziping

2012-05-30

In this contribution, bovine serum albumin stabilized gold nanoclusters as novel fluorescent probes were successfully utilized for the detection of ciprofloxacin for the first time. Our prepared gold nanoclusters exhibited strong emission with peak maximum at 635 nm. Cu(2+) was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of ciprofloxacin caused the fluorescence intensity restoration of the Cu(2+)-gold nanoclusters system. The increase in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by ciprofloxacin allows the sensitive detection of ciprofloxacin in the range of 0.4 ng mL(-1) to 50 ng mL(-1). The detection limit for ciprofloxacin is 0.3 ng mL(-1) at a signal-to-noise ratio of 3. The present sensor for ciprofloxacin detection possesses a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results. Copyright © 2012 Elsevier B.V. All rights reserved.

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

NASA Astrophysics Data System (ADS)

D'Arcy, Julio M.; Tran, Henry D.; Stieg, Adam Z.; Gimzewski, James K.; Kaner, Richard B.

2012-05-01

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated. Electronic supplementary information (ESI) available: Droplet coalescence, catenoid formation, mechanism of film growth, scanning electron micrographs showing carbon nanotube alignment, flexible transparent films of SWCNTs, AFM images of a chemically converted graphene film, and SEM images of SWCNT free-standing thin films. See DOI: 10.1039/c2nr00010e

Defects and nanocluster engineering in MgO

NASA Astrophysics Data System (ADS)

Fedorov, A. V.; van Veen, A.; van Huis, M. A.; Schut, H.; Kooi, B. J.; De Hosson, J. Th.; Zimmerman, R. L.

2001-07-01

The optical properties of MgO crystals are known to change after introduction of nanosize metal precipitates. In this work the formation of metallic nanoclusters in the presence of nanosize rectangular shaped cavities was studied. The rectangular cavities were formed by 30 keV He+ implantation followed by 1273 K annealing. The formation of cavities and their location was established by Positron Beam Analysis (PBA). The rectangular shape and their alignment in (100) direction was observed by X-TEM. Subsequently, the samples were implanted with 600 keV Ag and 1000 keV Au in order to introduce the metal ions in the vicinity of the cavities. The samples were then annealed to provide the formation of nanoclusters. The evolution of the implantation induced defects was monitored by PBA. The optical properties were studied by light absorption measurements.

Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols.

PubMed

Li, Lun; Dou, Liguang; Zhang, Hui

2014-04-07

M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 ± 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ∼0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h(-1)) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.

Active and inactive β1 integrins segregate into distinct nanoclusters in focal adhesions.

PubMed

Spiess, Matthias; Hernandez-Varas, Pablo; Oddone, Anna; Olofsson, Helene; Blom, Hans; Waithe, Dominic; Lock, John G; Lakadamyali, Melike; Strömblad, Staffan

2018-06-04

Integrins are the core constituents of cell-matrix adhesion complexes such as focal adhesions (FAs) and play key roles in physiology and disease. Integrins fluctuate between active and inactive conformations, yet whether the activity state influences the spatial organization of integrins within FAs has remained unclear. In this study, we address this question and also ask whether integrin activity may be regulated either independently for each integrin molecule or through locally coordinated mechanisms. We used two distinct superresolution microscopy techniques, stochastic optical reconstruction microscopy (STORM) and stimulated emission depletion microscopy (STED), to visualize active versus inactive β1 integrins. We first reveal a spatial hierarchy of integrin organization with integrin molecules arranged in nanoclusters, which align to form linear substructures that in turn build FAs. Remarkably, within FAs, active and inactive β1 integrins segregate into distinct nanoclusters, with active integrin nanoclusters being more organized. This unexpected segregation indicates synchronization of integrin activities within nanoclusters, implying the existence of a coordinate mechanism of integrin activity regulation. © 2018 Spiess et al.

Chiral Antioxidant-based Gold Nanoclusters Reprogram DNA Epigenetic Patterns

PubMed Central

Ma, Yue; Fu, Hualin; Zhang, Chunlei; Cheng, Shangli; Gao, Jie; Wang, Zhen; Jin, Weilin; Conde, João; Cui, Daxiang

2016-01-01

Epigenetic modifications sit ‘on top of’ the genome and influence DNA transcription, which can force a significant impact on cellular behavior and phenotype and, consequently human development and disease. Conventional methods for evaluating epigenetic modifications have inherent limitations and, hence, new methods based on nanoscale devices are needed. Here, we found that antioxidant (glutathione) chiral gold nanoclusters induce a decrease of 5-hydroxymethylcytosine (5hmC), which is an important epigenetic marker that associates with gene transcription regulation. This epigenetic change was triggered partially through ROS activation and oxidation generated by the treatment with glutathione chiral gold nanoclusters, which may inhibit the activity of TET proteins catalyzing the conversion of 5-methylcytosine (5mC) to 5hmC. In addition, these chiral gold nanoclusters can downregulate TET1 and TET2 mRNA expression. Alteration of TET-5hmC signaling will then affect several downstream targets and be involved in many aspects of cell behavior. We demonstrate for the first time that antioxidant-based chiral gold nanomaterials have a direct effect on epigenetic process of TET-5hmC pathways and reveal critical DNA demethylation patterns. PMID:27633378

Sol processing of conjugated carbon nitride powders for thin-film fabrication.

PubMed

Zhang, Jinshui; Zhang, Mingwen; Lin, Lihua; Wang, Xinchen

2015-05-18

The chemical protonation of graphitic carbon nitride (CN) solids with strong oxidizing acids, for example HNO3, is demonstrated as an efficient pathway for the sol processing of a stable CN colloidal suspension, which can be translated into thin films by dip/disperse-coating techniques. The unique features of CN colloids, such as the polymeric matrix and the reversible hydrogen bonding, result in the thin-film electrodes derived from the sol solution exhibiting a high mechanical stability with improved conductivity for charge transport, and thus show a remarkably enhanced photo-electrochemical performance. The polymer system can in principle be broadly tuned by hybridization with desired functionalities, thus paving the way for the application of CN for specific tasks, as exemplified here by coupling with carbon nanotubes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural evolution and properties of small-size thiol-protected gold nanoclusters

NASA Astrophysics Data System (ADS)

Ma, Miaomiao; Liu, Liren; Zhu, Hengjiang; Lu, Junzhe; Tan, Guiping

2018-07-01

Ligand-protected gold clusters are widely used in biosensors and catalysis. Understanding the structural evolution of these kinds of nanoclusters is important for experimental synthesis. Herein, based on the particle swarm optimisation algorithm and density functional theory method, we use [Au1(SH)2]n, [Au2(SH)3]n, [Au3(SH)4]n (n = 1-3) as basic units to research the structural evolution relationships from building blocks to the final whole structures. Results show that there is a 'line-ring-core' structural evolution pattern in the growth process of the nanoclusters. The core structures of the ligand-protected gold clusters consist of Au3, Au4, Au6 and Au7 atoms. The electronics and optics analysis reflects that stability and optical properties gradually enhance with increase in size. These results can be used to understand the initial growth stage and design new ligand-protected nanoclusters.

Non-Toxic Gold Nanoclusters for Solution-Processed White Light-Emitting Diodes.

PubMed

Chao, Yu-Chiang; Cheng, Kai-Ping; Lin, Ching-Yi; Chang, Yu-Li; Ko, Yi-Yun; Hou, Tzu-Yin; Huang, Cheng-Yi; Chang, Walter H; Lin, Cheng-An J

2018-06-11

Solution-processed optoelectronic devices are attractive because of the potential low-cost fabrication and the compatibility with flexible substrate. However, the utilization of toxic elements such as lead and cadmium in current optoelectronic devices on the basis of colloidal quantum dots raises environmental concerns. Here we demonstrate that white-light-emitting diodes can be achieved by utilizing non-toxic and environment-friendly gold nanoclusters. Yellow-light-emitting gold nanoclusters were synthesized and capped with trioctylphosphine. These gold nanoclusters were then blended with the blue-light-emitting organic host materials to form the emissive layer. A current efficiency of 0.13 cd/A was achieved. The Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.33) were obtained from our experimental analysis, which is quite close to the ideal pure white emission coordinates (0.33, 0.33). Potential applications include innovative lighting devices and monitor backlight.

One-step preparation of multiwall carbon nanotube/silicon hybrids for solar energy conversion

NASA Astrophysics Data System (ADS)

Lobiak, Egor V.; Bychanok, Dzmitry S.; Shlyakhova, Elena V.; Kuzhir, Polina P.; Maksimenko, Sergey A.; Bulusheva, Lyubov G.; Okotrub, Alexander V.

2016-03-01

The hybrid material consisting of a thin layer of multiwall carbon nanotubes (MWCNTs) on an n-doped silicon wafer was obtained in one step using an aerosol-assisted catalytic chemical vapor deposition. The MWCNTs were grown from a mixture of acetone and ethanol with ˜0.2 wt.% of iron polyoxomolybdate nanocluster of the keplerate-type structure. The samples produced at 800°C and 1050°C were tested as a solar energy converter. It was shown that photoresponse of the hybrid material significantly depends on the presence of structural defects in MWCNTs, being much higher in the case of more defective nanotubes. This is because defects lead to p-doping of nanotubes, whereas the p-n heterojunction between MWCNTs and silicon provides a high efficiency of the solar cell.

Thermally robust Au99(SPh)42 nanoclusters for chemoselective hydrogenation of nitrobenzaldehyde derivatives in water.

PubMed

Li, Gao; Zeng, Chenjie; Jin, Rongchao

2014-03-05

We report the synthesis and catalytic application of thermally robust gold nanoclusters formulated as Au99(SPh)42. The formula was determined by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry in conjunction with thermogravimetric analysis. The optical spectrum of Au99(SPh)42 nanoclusters shows absorption peaks at ~920 nm (1.35 eV), 730 nm (1.70 eV), 600 nm (2.07 eV), 490 nm (2.53 eV), and 400 nm (3.1 eV) in contrast to conventional gold nanoparticles, which exhibit a plasmon resonance band at 520 nm (for spherical particles). The ceria-supported Au99(SPh)42 nanoclusters were utilized as a catalyst for chemoselective hydrogenation of nitrobenzaldehyde to nitrobenzyl alcohol in water using H2 gas as the hydrogen source. The selective hydrogenation of the aldehyde group catalyzed by nanoclusters is a surprise because conventional nanogold catalysts instead give rise to the product resulting from reduction of the nitro group. The Au99(SPh)42/CeO2 catalyst gives high catalytic activity for a range of nitrobenzaldehyde derivatives and also shows excellent recyclability due to its thermal robustness. We further tested the size-dependent catalytic performance of Au25(SPh)18 and Au36(SPh)24 nanoclusters, and on the basis of their crystal structures we propose a molecular adsorption site for nitrobenzaldehyde. The nanocluster material is expected to find wide application in catalytic reactions.

Electron microscopy and positron annihilation study of CdSe nanoclusters embedded in MgO

NASA Astrophysics Data System (ADS)

van Huis, M. A.; van Veen, A.; Schut, H.; Eijt, S. W. H.; Kooi, B. J.; De Hosson, J. Th. M.

2004-06-01

CdSe nanoclusters are created in MgO by means of co-implantation of 280 keV, 1 × 10 16 Cd ions cm -2 and 210 keV, 1 × 10 16 Se ions cm -2 in single crystals of MgO(0 0 1) and subsequent thermal annealing at a temperature of 1300 K. The structural properties and the orientation relationship between the CdSe and the MgO are investigated using cross-sectional transmission electron microscopy (XTEM). The crystal structure of the nanoclusters depends on their size. The smallest nanoclusters with a size below 5 nm have the cubic rocksalt crystal structure. The larger nanoclusters have a different (most likely the cubic sphalerite) crystal structure. The defect evolution in the sample after ion implantation and during thermal annealing is investigated using Doppler broadening positron beam analysis (PBA). The defect evolution in samples co-implanted with Cd and Se is compared to the defect evolution in samples implanted with only Cd or only Se ions.

Formation and emission mechanisms of Ag nanoclusters in the Ar matrix assembly cluster source

NASA Astrophysics Data System (ADS)

Zhao, Junlei; Cao, Lu; Palmer, Richard E.; Nordlund, Kai; Djurabekova, Flyura

2017-11-01

In this paper, we study the mechanisms of growth of Ag nanoclusters in a solid Ar matrix and the emission of these nanoclusters from the matrix by a combination of experimental and theoretical methods. The molecular dynamics simulations show that the cluster growth mechanism can be described as "thermal spike-enhanced clustering" in multiple sequential ion impact events. We further show that experimentally observed large sputtered metal clusters cannot be formed by direct sputtering of Ag mixed in the Ar. Instead, we describe the mechanism of emission of the metal nanocluster that, at first, is formed in the cryogenic matrix due to multiple ion impacts, and then is emitted as a result of the simultaneous effects of interface boiling and spring force. We also develop an analytical model describing this size-dependent cluster emission. The model bridges the atomistic simulations and experimental time and length scales, and allows increasing the controllability of fast generation of nanoclusters in experiments with a high production rate.

Oxygen evolution reaction in nanoconfined carbon nanotubes

NASA Astrophysics Data System (ADS)

Li, Ying; Lu, Xuefeng; Li, Yunfang; Zhang, Xueqing

2018-05-01

Improving oxygen electrochemistry through nanoscopic confinement has recently been highlighted as a promising strategy. In-depth understanding the role of confinement is therefore required. In this study, we simulate the oxygen evolution reaction (OER) on iron oxide nanoclusters under confinement of (7,7) and (8,8) armchair carbon nanotubes (CNTs). The free energies of the four proton coupled electron transfer (PCET) steps and the OER overpotentials are calculated. The Fe4O6 nanocluster confined in (7,7) CNT is found to be the most active for OER among the systems considered in this work. This leads to an increase in catalytic efficiency of OER compared to the hematite (110) surface, which was reported recently as an active surface towards OER. The calculated results show that the OER overpotential depends strongly on the magnetic properties of the iron oxide nanocluster. These findings are helpful for experimental design of efficient catalyst for water splitting applications.

Magnetic behavior of Si-Ge bond in SixGe4-x nano-clusters

NASA Astrophysics Data System (ADS)

Nahali, Masoud; Mehri, Ali

2018-06-01

The structure of SixGe4-x nano-clusters were optimized by MPW1B95 level of theory using MG3S and SDB-aug-cc-PVTZ basis set. The agreement of the calculated ionization and dissociation energies with experimental values validates the reported structures of nano-clusters and justifies the use of hybrid meta density functional method. Since the Si-Si bond is stronger than Si-Ge and Ge-Ge bonds, the Si-Si, Si-Ge, and Ge-Ge diagonal bonds determine the precedence of the stability in these nano-clusters. The hybrid meta density functional calculations were carried out to investigate the adsorption of CO on all possible SixGe4-x nano-clusters. It was found that the silicon atom generally makes a stronger bond with CO than germanium and thereby preferentially affects the shape of structures having higher multiplicity. In Si-Ge structures with higher spin more than 95% of spins accumulate on positions with less bonds to other atoms of the cluster. Through CO adsorption on these clusters bridge structures are made that behave as spin bridge which conduct the spin from the nano-cluster surface to the adsorbate atoms. A better understanding of bridged structures was achieved upon introducing the 'spin bridge' concept. Based on exhaustive spin density analysis, it was found that the reason for the extra negative charge on oxygen in the bridged structures is the relocation of spin from the surface through the bridge.

Phenotypic Screening Identifies Protein Synthesis Inhibitors as H-Ras-Nanocluster-Increasing Tumor Growth Inducers.

PubMed

Najumudeen, Arafath K; Posada, Itziar M D; Lectez, Benoit; Zhou, Yong; Landor, Sebastian K-J; Fallarero, Adyary; Vuorela, Pia; Hancock, John; Abankwa, Daniel

2015-12-15

Ras isoforms H-, N-, and K-ras are each mutated in specific cancer types at varying frequencies and have different activities in cell fate control. On the plasma membrane, Ras proteins are laterally segregated into isoform-specific nanoscale signaling hubs, termed nanoclusters. As Ras nanoclusters are required for Ras signaling, chemical modulators of nanoclusters represent ideal candidates for the specific modulation of Ras activity in cancer drug development. We therefore conducted a chemical screen with commercial and in-house natural product libraries using a cell-based H-ras-nanoclustering FRET assay. Next to established Ras inhibitors, such as a statin and farnesyl-transferase inhibitor, we surprisingly identified five protein synthesis inhibitors as positive regulators. Using commonly employed cycloheximide as a representative compound, we show that protein synthesis inhibition increased nanoclustering and effector recruitment specifically of active H-ras but not of K-ras. Consistent with these data, cycloheximide treatment activated both Erk and Akt kinases and specifically promoted H-rasG12V-induced, but not K-rasG12V-induced, PC12 cell differentiation. Intriguingly, cycloheximide increased the number of mammospheres, which are enriched for cancer stem cells. Depletion of H-ras in combination with cycloheximide significantly reduced mammosphere formation, suggesting an exquisite synthetic lethality. The potential of cycloheximide to promote tumor cell growth was also reflected in its ability to increase breast cancer cell tumors grown in ovo. These results illustrate the possibility of identifying Ras-isoform-specific modulators using nanocluster-directed screening. They also suggest an unexpected feedback from protein synthesis inhibition to Ras signaling, which might present a vulnerability in certain tumor cell types.

Silicon solar cell performance deposited by diamond like carbon thin film ;Atomic oxygen effects;

NASA Astrophysics Data System (ADS)

Aghaei, Abbas Ail; Eshaghi, Akbar; Karami, Esmaeil

2017-09-01

In this research, a diamond-like carbon thin film was deposited on p-type polycrystalline silicon solar cell via plasma-enhanced chemical vapor deposition method by using methane and hydrogen gases. The effect of atomic oxygen on the functioning of silicon coated DLC thin film and silicon was investigated. Raman spectroscopy, field emission scanning electron microscopy, atomic force microscopy and attenuated total reflection-Fourier transform infrared spectroscopy were used to characterize the structure and morphology of the DLC thin film. Photocurrent-voltage characteristics of the silicon solar cell were carried out using a solar simulator. The results showed that atomic oxygen exposure induced the including oxidation, structural changes, cross-linking reactions and bond breaking of the DLC film; thus reducing the optical properties. The photocurrent-voltage characteristics showed that although the properties of the fabricated thin film were decreased after being exposed to destructive rays, when compared with solar cell without any coating, it could protect it in atomic oxygen condition enhancing solar cell efficiency up to 12%. Thus, it can be said that diamond-like carbon thin layer protect the solar cell against atomic oxygen exposure.

Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

DOE PAGES

Antony, Jiji; Nutting, Joseph; Baer, Donald R.; ...

2006-01-01

Nmore » anoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7 ∘ C . Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM). The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET) process are size-dependent and compared with the calculated data.« less

Improvement in interfacial characteristics of low-voltage carbon nanotube thin-film transistors with solution-processed boron nitride thin films

NASA Astrophysics Data System (ADS)

Jeon, Jun-Young; Ha, Tae-Jun

2017-08-01

In this article, we demonstrate the potential of solution-processed boron nitride (BN) thin films for high performance single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) with low-voltage operation. The use of BN thin films between solution-processed high-k dielectric layers improved the interfacial characteristics of metal-insulator-metal devices, thereby reducing the current density by three orders of magnitude. We also investigated the origin of improved device performance in SWCNT-TFTs by employing solution-processed BN thin films as an encapsulation layer. The BN encapsulation layer improves the electrical characteristics of SWCNT-TFTs, which includes the device key metrics of linear field-effect mobility, sub-threshold swing, and threshold voltage as well as the long-term stability against the aging effect in air. Such improvements can be achieved by reduced interaction of interfacial localized states with charge carriers. We believe that this work can open up a promising route to demonstrate the potential of solution-processed BN thin films on nanoelectronics.

An investigation into the melting of silicon nanoclusters using molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Fang, Kuan-Chuan; Weng, Cheng-I.

2005-02-01

Using the Stillinger-Weber (SW) potential model, we have performed molecular dynamics (MD) simulations to investigate the melting of silicon nanoclusters comprising a maximum of 9041 atoms. This study investigates the size, surface energy and root mean square displacement (RMSD) characteristics of the silicon nanoclusters as they undergo a heating process. The numerical results reveal that an intermediate nanocrystal regime exists for clusters with more than 357 atoms. Within this regime, a linear relationship exists between the cluster size and its melting temperature. It is found that melting of the silicon nanoclusters commences at the surface and that Tm,N = Tm,Bulk-αN-1/3. Therefore, the extrapolated melting temperature of the bulk with a surface decreases from Tm,Bulk = 1821 K to a value of Tm,357 = 1380 K at the lower limit of the intermediate nanocrystal regime.

A ratiometric nanoprobe based on silver nanoclusters and carbon dots for the fluorescent detection of biothiols

NASA Astrophysics Data System (ADS)

Zhang, Shuming; Lin, Bixia; Yu, Ying; Cao, Yujuan; Guo, Manli; Shui, Lingling

2018-04-01

Ratiometric fluorescent probes could eliminate the influence from experimental factors and improve the detection accuracy. In this article, a ratiometric nanoprobe was constructed based on silver nanoclusters (AgNCs) with nitrogen-doped carbon dots (NCDs) and used for the detection of biothiols. The fluorescence peak of AgNCs was observed at 650 nm with excitation wavelength at 370 nm. In order to construct the ratiometric fluorescent probe, NCDs with the excitation and emission wavelengths at 370 nm and 450 nm were selected. After adding AgNCs, the fluorescence of NCDs was quenched. The mechanism of the fluorescence quenching was studied by fluorescence, UV-Vis absorption and the fluorescence lifetime spectra. The results indicated that the quenching could be ascribed to the inner filter effect (IFE). With the addition of biothiols, the fluorescence of AgNCs at 650 nm decreased due to the breakdown of AgNCs, and the fluorescence of NCDs at 450 nm recovered accordingly. Thus, the relationship between the ratio of the fluorescence intensities (I450/I650) and biothiol concentration was used to establish the determination method for biothiols. Cysteine (Cys) was taken as the model of biothiols, and the working curve for Cys was I450/I650 = 0.60CCys - 1.86 (CCys: μmol/L) with the detection limit of 0.14 μmol/L (S/N = 3). Then, the method was used for the detection of Cys in human urine and serum samples with satisfactory accuracy and recovery ratios. Furthermore, the probe could be applied for the visual semi-quantitative determination of Cys by naked eyes.

Time-resolved electronic and optical properties of a thiolate-protected Au38 nanocluster

NASA Astrophysics Data System (ADS)

Meng, Qingguo; May, Stanley P.; Berry, Mary T.; Kilin, Dmitri S.

2015-02-01

Density functional theory and density matrix theory are employed to investigate the time-dependent optical and electronic properties of an Au14 nanocluster protected by six cyclic thiolate ligands, Au4(SCH3)4. The Au14[Au4(SCH3)4]6 nanocluster, i.e. Au38(SCH3)24, is equivalent to a truncated-octahedral face-centred cubic Au38 core coated by a monolayer of 24 methylthiol molecules. The electronic and optical properties, such as density of states, linear absorption spectra, nonradiative nonadiabatic dissipative electronic dynamics and radiative emission spectra were calculated and compared for the core Au14 and thiolate-protected Au38(SCH3)24 nanocluster. The main observation from computed photoluminescence for both models is a mechanism of radiative emission. Specifically, a strong contribution to light emission intensity originates from intraband transitions inside the conduction band (CB) in addition to interband LUMO → HOMO transition (HOMO: highest occupied molecular orbital and LUMO: lowest unoccupied molecular orbital). Such comparison clarifies the contributions from Au core and methylthiol ligands to the electronic and optical properties of the Au38(SCH3)24 nanocluster.

Photophysical characterization of fluorescent metal nanoclusters synthesized using oligonucleotides, proteins and small molecule ligands

NASA Astrophysics Data System (ADS)

Yeh, Hsin-Chih; Sharma, Jaswinder; Yoo, Hyojong; Martinez, Jennifer S.; Werner, James H.

2010-02-01

The size transition from bulk conducting metals to insulating nanoparticles and eventually to single atoms passes through the relatively unexplored few-atom nanocluster region. With dimensions close to the Fermi wavelength, these nanoclusters demonstrate molecule-like properties distinct from bulk metals or atoms, such as discrete and size-tunable electronic transitions which lead to photoluminescence. Current research aims to elucidate the fundamental photophysical properties of metal nanoclusters made by different means and based on different encapsulation agents. Here, we report the study of the photophysical properties, including quantum yields, lifetimes, extinction coefficients, blinking dynamics and sizes, of silver and gold nanoclusters synthesized using oligonucleotides, a protein (bovine serum albumin) and a Good's buffer molecule (MES, 2-(N-morpholino) ethanesulfonic acid) as encapsulation agents. We also investigate the change of photoluminescence as a function of temperature. Furthermore, we show that the fluorescent metal clusters can be used as a donor in forming a resonance energy transfer pair with a commercial organic quencher. These new fluorophores have great potential as versatile tools for a broad range of applications in biological and chemical detection.

Ab Initio Study of Structural and Electronic Properties of (ZnO) n "Magical" Nanoclusters n = (34, 60)

NASA Astrophysics Data System (ADS)

Bovhyra, Rostyslav; Popovych, Dmytro; Bovgyra, Oleg; Serednytski, Andrew

2017-01-01

Density functional theory studies of the structural and electronic properties of nanoclusters (ZnO) n ( n = 34, 60) in different geometric configurations were conducted. For each cluster, an optimization (relaxation) of structure geometry was performed, and the basic properties of the band structure were investigated. It was established that for the (ZnO)34 nanoclusters, the most stable are fullerene-like hollow structures that satisfy the rule of six isolated quadrangles. For the (ZnO)60 nanoclusters, different types of isomers, including hollow structures and sodalite-like structures composed from (ZnO)12 nanoclusters, were investigated. It was determined that the most energetically favorable structure was sodalite-type structure composed of seven (ZnO)12 clusters with common quadrangle edges.

Thermoacoustic chips with carbon nanotube thin yarn arrays.

PubMed

Wei, Yang; Lin, Xiaoyang; Jiang, Kaili; Liu, Peng; Li, Qunqing; Fan, Shoushan

2013-10-09

Aligned carbon nanotube (CNT) films drawn from CNT arrays have shown the potential as thermoacoustic loudspeakers. CNT thermoacoustic chips with robust structures are proposed to promote the applications. The silicon-based chips can play sound and fascinating rhythms by feeding alternating currents and audio signal to the suspending CNT thin yarn arrays across grooves in them. In additional to the thin yarns, experiments further revealed more essential elements of the chips, the groove depth and the interdigital electrodes. The sound pressure depends on the depth of the grooves, and the thermal wavelength can be introduced to define the influence-free depth. The interdigital fingers can effectively reduce the driving voltage, making the chips safe and easy to use. The chips were successfully assembled into earphones and have been working stably for about one year. The thermoacoustic chips can find many applications in consumer electronics and possibly improve the audiovisual experience.

Cluster-to-cluster transformation among Au6, Au8 and Au11 nanoclusters.

PubMed

Ren, Xiuqing; Fu, Junhong; Lin, Xinzhang; Fu, Xuemei; Yan, Jinghui; Wu, Ren'an; Liu, Chao; Huang, Jiahui

2018-05-22

We present the cluster-to-cluster transformations among three gold nanoclusters, [Au6(dppp)4]2+ (Au6), [Au8(dppp)4Cl2]2+ (Au8) and [Au11(dppp)5]3+ (Au11). The conversion process follows a rule that states that the transformation of a small cluster to a large cluster is achieved through an oxidation process with an oxidizing agent (H2O2) or with heating, while the conversion of a large cluster to a small one occurs through a reduction process with a reducing agent (NaBH4). All the reactions were monitored using UV-Vis spectroscopy and ESI-MS. This work may provide an alternative approach to the synthesis of novel gold nanoclusters and a further understanding of the structural transformation relationship of gold nanoclusters.

Raman studied of undoped amorphous carbon thin film deposited by bias assisted-CVD

NASA Astrophysics Data System (ADS)

Ishak, A.; Fadzilah, A. N.; Dayana, K.; Saurdi, I.; Malek, M. F.; Nurbaya, Z.; Shafura, A. K.; Rusop, M.

2018-05-01

The undoped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The effect of different substrate deposition temperatures on structural and electrical properties of undoped doped amorphous carbon film was discussed. The structural of undoped amorphous carbon films were correlated with Raman analysis through the evolution of D and G bands, Fourier spectra, and conductivity measurement. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. The spectral evolution observed at different substrate deposition temperatures show progressive formation of crystallites. It was predicted that small number of hydrogen is terminated with carbon at surface of thin film as shown by FTIR spectra since palm oil has high number of hydrogen (C67H127O8). These structural changes were further correlated with conductivity and the results obtained are discussed and compared. The conductivity is found in the range of 10-8 Scm-1. The increase of conductivity is correlated by the change of structural properties as correlated with characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG and FTIR result.

Supersensitive and selective detection of picric acid explosive by fluorescent Ag nanoclusters.

PubMed

Zhang, Jian Rong; Yue, Yuan Yuan; Luo, Hong Qun; Li, Nian Bing

2016-02-07

Picric acid (PA) explosive is a hazard to public safety and health, so the sensitive and selective detection of PA is very important. In the present work, polyethyleneimine stabilized Ag nanoclusters were successfully used for the sensitive and selective quantification of PA on the basis of fluorescence quenching. The quenching efficiency of Ag nanoclusters is proportional to the concentration of PA and the logarithm of PA concentration over two different concentration ranges (1.0 nM-1 μM for the former and 0.25-20 μM for the latter), thus the proposed quantitative strategy for PA provides a wide linear range of 1.0 nM-20 μM. The detection limit based on 3σ/K is 0.1 nM. The quenching mechanism of Ag nanoclusters by PA is discussed in detail. The results indicate that the selective detection of PA over other nitroaromatics including 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), p-nitrotoluene (p-NT), m-dinitrobenzene (m-DNB), and nitrobenzene (NB), is due to the electron transfer and energy transfer between PA and polyethyleneimine-capped Ag nanoclusters. In addition, the experimental data obtained for the analysis of artificial samples show that the proposed PA sensor is potentially applicable in the determination of trace PA explosive in real samples.

Investigation of the Emissivity and Suitability of a Carbon Thin Film for Terahertz Absorbers

DTIC Science & Technology

2016-06-01

Carbonization In order to verify whether the carbon soot coated THz sensor produces sufficient spectral emissivity for IR-based readout, dummy test...ABSTRACT (maximum 200 words) The main goal of this work is to optimize the emissivity of terahertz (THz) thermal sensors by deposition of a carbon thin...film. Previously, these thermal sensors were designed to detect THz radiation utilizing metamaterials in a complicated optical probing scheme. We

Screen printing as a scalable and low-cost approach for rigid and flexible thin-film transistors using separated carbon nanotubes.

PubMed

Cao, Xuan; Chen, Haitian; Gu, Xiaofei; Liu, Bilu; Wang, Wenli; Cao, Yu; Wu, Fanqi; Zhou, Chongwu

2014-12-23

Semiconducting single-wall carbon nanotubes are very promising materials in printed electronics due to their excellent mechanical and electrical property, outstanding printability, and great potential for flexible electronics. Nonetheless, developing scalable and low-cost approaches for manufacturing fully printed high-performance single-wall carbon nanotube thin-film transistors remains a major challenge. Here we report that screen printing, which is a simple, scalable, and cost-effective technique, can be used to produce both rigid and flexible thin-film transistors using separated single-wall carbon nanotubes. Our fully printed top-gated nanotube thin-film transistors on rigid and flexible substrates exhibit decent performance, with mobility up to 7.67 cm2 V(-1) s(-1), on/off ratio of 10(4)∼10(5), minimal hysteresis, and low operation voltage (<10 V). In addition, outstanding mechanical flexibility of printed nanotube thin-film transistors (bent with radius of curvature down to 3 mm) and driving capability for organic light-emitting diode have been demonstrated. Given the high performance of the fully screen-printed single-wall carbon nanotube thin-film transistors, we believe screen printing stands as a low-cost, scalable, and reliable approach to manufacture high-performance nanotube thin-film transistors for application in display electronics. Moreover, this technique may be used to fabricate thin-film transistors based on other materials for large-area flexible macroelectronics, and low-cost display electronics.

Synthesis of nickel entities: From highly stable zerovalent nanoclusters to nanowires. Growth control and catalytic behavior.

PubMed

Peinetti, Ana S; Mizrahi, Martín; Requejo, Félix G; Buceta, David; López-Quintela, M Arturo; González, Graciela A; Battaglini, Fernando

2018-04-15

Non-noble metal nanoclusters synthesis is receiving increased attention due to their unique catalytic properties and lower cost. Herein, the synthesis of ligand-free Ni nanoclusters with an average diameter of 0.7 nm corresponding to a structure of 13 atoms is presented; they exhibit a zero-valence state and a high stability toward oxidation and thermal treatment. The nanoclusters formation method consists in the electroreduction of nickel ions inside an ordered mesoporous alumina; also, by increasing the current density, other structures can be obtained reaching to nanowires of 10 nm diameter. A seed-mediated mechanism is proposed to explain the growth to nanowires inside these mesoporous cavities. The size dependence on the catalytic behavior of these entities is illustrated by studying the reduction of methylene blue where the nanoclusters show an outstanding performance. Copyright © 2018 Elsevier Inc. All rights reserved.

Thin-film hermeticity - A quantitative analysis of diamondlike carbon using variable angle spectroscopic ellipsometry

NASA Technical Reports Server (NTRS)

Orzeszko, S.; De, Bhola N.; Woollam, John A.; Pouch, John J.; Alterovitz, Samuel A.

1988-01-01

This paper reports on the successful application of variable-angle spectroscopic ellipsometry to quantitative thin-film hermeticity evaluation. It is shown that, under a variety of film preparations and moisture introduction conditions, water penetrates only a very thin diamondlike carbon (DLC) top surface-roughness region. Thus, DLC is an excellent candidate for use as protective coatings in adverse chemical and aqueous environments.

Room-temperature low-voltage electroluminescence in amorphous carbon nitride thin films

NASA Astrophysics Data System (ADS)

Reyes, R.; Legnani, C.; Ribeiro Pinto, P. M.; Cremona, M.; de Araújo, P. J. G.; Achete, C. A.

2003-06-01

White-blue electroluminescent emission with a voltage bias less than 10 V was achieved in rf sputter-deposited amorphous carbon nitride (a-CN) and amorphous silicon carbon nitride (a-SiCN) thin-film-based devices. The heterojunction structures of these devices consist of: Indium tin oxide (ITO), used as a transparent anode; amorphous carbon film as an emission layer, and aluminum as a cathode. The thickness of the carbon films was about 250 Å. In all of the produced diodes, a stable visible emission peaked around 475 nm is observed at room temperature and the emission intensity increases with the current density. For an applied voltage of 14 V, the luminance was about 3 mCd/m2. The electroluminescent properties of the two devices are discussed and compared.

Adsorption-Coupled Diffusion of Gold Nanoclusters within a Large-Pore Protein Crystal Scaffold.

PubMed

Hartje, Luke F; Munsky, Brian; Ni, Thomas W; Ackerson, Christopher J; Snow, Christopher D

2017-08-17

Large-pore protein crystals (LPCs) are ordered biologically derived nanoporous materials exhibiting pore diameters greater than 8 nm. These substantial pores distinguish LPCs from typical nanoporous scaffolds, enabling engineered LPC materials to readily uptake, immobilize, and release macromolecular guests. In this study, macromolecular transport within an LPC environment was experimentally and computationally investigated by studying adsorption-coupled diffusion of Au 25 (glutathione) 18 nanoclusters within a cross-linked LPC scaffold via time-lapse confocal microscopy, bulk equilibrium adsorption, and hindered diffusion simulation. Equilibrium adsorption data is congruent with a Langmuir adsorption model, exhibiting strong binding behavior between nanoclusters and the scaffold. The standard Gibbs free energy of binding is equivalent to -37.2 kJ/mol, and the maximum binding capacity of 1.25 × 10 3 mg/g corresponds to approximately 29 nanoclusters per LPC unit cell. The hindered diffusion model showed good agreement with experimental data, revealing a pore diffusion coefficient of 3.7 × 10 -7 cm 2 /s under low nanocluster concentration. Furthermore, the model was sufficient to determine adsorption and desorption kinetic values for k a and k d equal to 13 cm 3 /mol·s and 1.7 × 10 -7 s -1 , respectively. At higher nanocluster concentrations, the simulated pore diffusion coefficient could be reduced by 3 orders of magnitude to 3.4 × 10 -10 cm 2 /s due to the effects of pore occlusion. This study demonstrates a strategy to analyze adsorption-coupled diffusion data to better understand complex transport of fluorescent macromolecules into LPCs. This approach fits the observable fluorescence data to the key molecular details and will benefit downstream efforts to engineer LPC-based nanoporous materials.

Initial Study on Thin Film Preparation of Carbon Nanodots Composites as Luminescence Material

NASA Astrophysics Data System (ADS)

Iskandar, F.; Aimon, A. H.; Akmaluddin, A. R.; Nuryadin, B. W.; Abdullah, M.

2016-08-01

Nowadays, the developments of phosphors materials require elements without noble metals and simple production process. Carbon nanodots (C-dots) are one of phosphor materials with wide range of emission band, and high biocompatibility. In this research thin film carbon nanodots composite have been prepared by spin coating method. Prior deposition, powder carbon nanodots were synthesized from a mixture of commercial urea as the nitrogen sources and citric acid as a carbon source by using hydrothermal and microwave-assisted heating method. The prepared powder was dispersed in transparent epoxy resin and then coated on glass substrate. The photoluminescence result for sample with 0.035 g citric acid exhibited an intense, single, homogeneous and broad spectrum with yellowish emission upon excitation at 365 nm. The Fourier Transform Infrared Spectroscopy (FTIR) result showed the existences of C=C, C-H, C=O, N-H and O-H functional groups which confirmed the quality of the sample. Further, based on UV-Vis measurement, the prepared thin film was highly transparent (transmittance 90%) with estimated film thickness around 764 nm. This result may open an opportunity for optoelectronic devices.

Diphosphine-Protected Au 22 Nanoclusters on Oxide Supports Are Active for Gas-Phase Catalysis without Ligand Removal

DOE PAGES

Wu, Zili; Hu, Guoxiang; Jiang, De-en; ...

2016-09-29

Investigation of monodispersed and atomically-precise Au nanoclusters provides a route to understand the roles of coordination, size, and ligand effects in Au catalysis. We have explored the catalytic behavior of a newly-synthesized Au 22(L 8) 6 nanocluster (L = 1,8-bis(diphenylphosphino) octane) with in situ uncoordinated Au sites supported on TiO 2, CeO 2 and Al 2O 3. Stability of the supported Au 22 nanoclusters was probed structurally by EXAFS and HAADF-STEM, and their adsorption and reactivity for CO oxidation were investigated by IR absorption spectroscopy and temperature programed flow reaction. Low temperature CO oxidation activity was observed for the supportedmore » pristine Au 22(L 8) 6 nanoclusters without ligand removal. Isotopically labeled O 2 was used to demonstrate that the reaction pathway occurs through a redox mechanism, consistent with the observed support-dependent activity trend: CeO 2 > TiO 2 > Al 2O 3. Substantiated by density functional theory (DFT) calculations, we conclude that the uncoordinated Au sites in the intact Au 22(L 8) 6 nanoclusters are capable of adsorbing CO, activating O2 and promoting CO oxidation reaction. Thanks to the presence of the in situ coordination unsaturated Au atoms, this work is the first clear demonstration of a ligand-protected Au nanocluster that are active for gas phase catalysis without the need of ligand removal.« less

Numerical insights into the early stages of nanoscale electrodeposition: nanocluster surface diffusion and aggregative growth.

PubMed

Mamme, Mesfin Haile; Köhn, Christoph; Deconinck, Johan; Ustarroz, Jon

2018-04-19

Fundamental understanding of the early stages of electrodeposition at the nanoscale is key to address the challenges in a wide range of applications. Despite having been studied for decades, a comprehensive understanding of the whole process is still out of reach. In this work, we introduce a novel modelling approach that couples a finite element method (FEM) with a random walk algorithm, to study the early stages of nanocluster formation, aggregation and growth, during electrochemical deposition. This approach takes into account not only electrochemical kinetics and transport of active species, but also the surface diffusion and aggregation of adatoms and small nanoclusters. The simulation results reveal that the relative surface mobility of the nanoclusters compared to that of the adatoms plays a crucial role in the early growth stages. The number of clusters, their size and their size dispersion are influenced more significantly by nanocluster mobility than by the applied overpotential itself. Increasing the overpotential results in shorter induction times and leads to aggregation prevalence at shorter times. A higher mobility results in longer induction times, a delayed transition from nucleation to aggregation prevalence, and as a consequence, a larger surface coverage of smaller clusters with a smaller size dispersion. As a consequence, it is shown that a classical first-order nucleation kinetics equation cannot describe the evolution of the number of clusters with time, N(t), in potentiostatic electrodeposition. Instead, a more accurate representation of N(t) is provided. We show that an evaluation of N(t), which neglects the effect of nanocluster mobility and aggregation, can induce errors of several orders of magnitude in the determination of nucleation rate constants. These findings are extremely important towards evaluating the elementary electrodeposition processes, considering not only adatoms, but also nanoclusters as building blocks.

Structure Evolution and Thermoelectric Properties of Carbonized Polydopamine Thin Films.

PubMed

Li, Haoqi; Aulin, Yaroslav V; Frazer, Laszlo; Borguet, Eric; Kakodkar, Rohit; Feser, Joseph; Chen, Yan; An, Ke; Dikin, Dmitriy A; Ren, Fei

2017-03-01

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. The largest room-temperature ZT of 2 × 10 -4 was obtained on samples heat-treated at 800 °C, which is higher than that of reduced graphene oxide.

Periodic silver nanocluster arrays over large-area silica nanosphere template as highly sensitive SERS substrate

NASA Astrophysics Data System (ADS)

Hou, Xu; Wang, Qi; Mao, Guoming; Liu, Hao; Yu, Rongdi; Ren, Xiaomin

2018-04-01

Periodic Ag nanocluster arrays for surface enhanced Raman spectroscopy (SERS) were fabricated through magnetron sputtering Ag over a large-area monolayer template which is based on silica (SiO2) nanospheres. High-density nanogaps between the adjacent Ag nanoclusters acted as "hot-spots", making a dominant contribution to the high-performance SERS detection. Moreover, the nanospheres and Ag nanoclusters effectively increased the surface roughness and also enlarged the surface area of as-obtained SERS substrate, which resulted in a further enhancement in Raman signals. As-prepared SERS substrates showed very high sensitivity with the enhancement factor (EF) value of 4.1 × 1012 for Rhodamine 6G (R6G), allowing the corresponding detection limit as low as 10-16 M. Additionally, SERS signal of melamine was still strong even though its concentration was lowered to 10-7 M. Our results show that preparing highly sensitive SERS substrate with periodic Ag nanoclusters over SiO2 nanosphere template is a convenient and promising pathway for chemical and biologic sensing.

Preparation, characterization and nonlinear absorption studies of cuprous oxide nanoclusters, micro-cubes and micro-particles

NASA Astrophysics Data System (ADS)

Sekhar, H.; Narayana Rao, D.

2012-07-01

Cuprous oxide nanoclusters, micro-cubes and micro-particles were successfully synthesized by reducing copper(II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction and FTIR studies revealed that the formation of pure single-phase cubic. Raman and EPR spectral studies show the presence of CuO in as-synthesized powders of Cu2O. Transmission electron microscopy and field emission scanning electron microscopy data revealed that the morphology evolves from nanoclusters to micro-cubes and micro-particles by increasing the concentration of NaOH. Linear optical measurements show absorption peak maximum shifts towards red with changing morphology from nanoclusters to micro-cubes and micro-particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm 6 ns laser pulses. Samples-exhibited both saturable as well as reverse saturable absorption. Due to confinement effects (enhanced band gap), we observed enhanced nonlinear absorption coefficient (β) in the case of nanoclusters compared to their micro-cubes and micro-particles.

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

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

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

We use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated and therebymore » the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

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

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE PAGES

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin; ...

2017-09-05

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Optical properties of diamond like carbon nanocomposite thin films

NASA Astrophysics Data System (ADS)

Alam, Md Shahbaz; Mukherjee, Nillohit; Ahmed, Sk. Faruque

2018-05-01

The optical properties of silicon incorporated diamond like carbon (Si-DLC) nanocomposite thin films have been reported. The Si-DLC nanocomposite thin film deposited on glass and silicon substrate by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) process. Fourier transformed infrared spectroscopic analysis revealed the presence of different bonding within the deposited films and deconvolution of FTIR spectra gives the chemical composition i.e., sp3/sp2 ratio in the films. Optical band gap calculated from transmittance spectra increased from 0.98 to 2.21 eV with a variation of silicon concentration from 0 to 15.4 at. %. Due to change in electronic structure by Si incorporation, the Si-DLC film showed a broad photoluminescence (PL) peak centered at 467 nm, i.e., in the visible range and its intensity was found to increase monotonically with at. % of Si.

Phosphatidylserine and GTPase activation control Cdc42 nanoclustering to counter dissipative diffusion.

PubMed

Sartorel, Elodie; Ünlü, Caner; Jose, Mini; Massoni-Laporte, Aurélie; Meca, Julien; Sibarita, Jean-Baptiste; McCusker, Derek

2018-04-18

The anisotropic organization of plasma membrane constituents is indicative of mechanisms that drive the membrane away from equilibrium. However, defining these mechanisms is challenging due to the short spatio-temporal scales at which diffusion operates. Here, we use high-density single protein tracking combined with photoactivation localization microscopy (sptPALM) to monitor Cdc42 in budding yeast, a system in which Cdc42 exhibits anisotropic organization. Cdc42 exhibited reduced mobility at the cell pole, where it was organized in nanoclusters. The Cdc42 nanoclusters were larger at the cell pole than those observed elsewhere in the cell. These features were exacerbated in cells expressing Cdc42-GTP, and were dependent on the scaffold Bem1, which contributed to the range of mobility and nanocluster size exhibited by Cdc42. The lipid environment, in particular phosphatidylserine levels, also played a role in regulating Cdc42 nanoclustering. These studies reveal how the mobility of a Rho GTPase is controlled to counter the depletive effects of diffusion, thus stabilizing Cdc42 on the plasma membrane and sustaining cell polarity. Movie S1 Movie S1 sptPALM imaging of live yeast expressing Pil1-mEOS expressed at the genomic locus. Pil1-mEOS was simultaneously photo-converted with a 405 nm laser and imaged with a 561 nm laser using HiLo illumination. Images were acquired at 20 ms intervals, of which 300 frames are shown at 7 frames per second.

Semiconducting Properties of Nanostructured Amorphous Carbon Thin Films Incorporated with Iodine by Thermal Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Kamaruzaman, Dayana; Ahmad, Nurfadzilah; Annuar, Ishak; Rusop, Mohamad

2013-11-01

Nanostructured iodine-post doped amorphous carbon (a-C:I) thin films were prepared from camphor oil using a thermal chemical vapor deposition (TCVD) technique at different doping temperatures. The structural properties of the films were studied by field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman, and Fourier transform infrared (FTIR) studies. FESEM and EDS studies showed successful iodine doping. FTIR and Raman studies showed that the a-C:I thin films consisted of a mixture of sp2- and sp3-bonded carbon atoms. The optical and electrical properties of a-C:I thin films were determined by UV-vis-NIR spectroscopy and current-voltage (I-V) measurement respectively. The optical band gap of a-C thin films decreased upon iodine doping. The highest electrical conductivity was found at 400 °C doping. Heterojunctions are confirmed by rectifying the I-V characteristics of an a-C:I/n-Si junction.

Fabrication and in vitro characterization of gadolinium-based nanoclusters for simultaneous drug delivery and radiation enhancement

NASA Astrophysics Data System (ADS)

Yoo, Shannon S.; Guo, Linghong; Sun, Xuejun; Shaw, Andrew R.; Yuan, Zhipeng; Löbenberg, Raimar; Roa, Wilson H.

2016-09-01

We report the synthesis of a gadolinium hydroxide (Gd(OH)3) nanorod based doxorubicin (Dox) delivery system that can enhance both magnetic resonance imaging contrast and radiation sensitivity. A simple and cost effective wet-chemical method was utilized in the presence of manganese (Mn) ions and Dox to produce the Gd(OH)3:Mn·Dox nanocluster structure. The Gd(OH)3:Mn·Dox nanocluster was composed of Mn-doped Gd(OH)3 nanorods arranged in parallel with Dox as a linker molecule between the adjacent nanorods. No other studies have utilized Dox as both the linker and therapeutic molecule in a nanostructure to date. The Gd(OH)3 nanorod is reported to have no significant cellular or in vivo toxicity, which makes it an ideal base material for this biomedical application. The Gd(OH)3:Mn·Dox nanocluster exhibited paramagnetic behavior and was stable in a colloidal solution. The nanocluster also enabled high Dox loading capacity and specifically released Dox in a sustained and pH-dependent manner. The positively charged Gd(OH)3:Mn·Dox nanoclusters were readily internalized into MDA-MB-231 breast cancer cells via endocytosis, which resulted in intracellular release of Dox. The released Dox in cells was effective in conferring cytotoxicity and inhibiting proliferation of cancer cells. Furthermore, a synergistic anticancer effect could be observed with radiation treatment. Overall, the Gd(OH)3:Mn·Dox nanocluster drug delivery system described herein may have potential utility in clinics as a multifunctional theranostic nanoparticle with combined benefits in both diagnosis and therapy in the management of cancer.

Elastic properties of single-walled carbon nanotube thin film by nanoindentation test.

PubMed

Tang, Xingling; El-Hami, Abdelkhalak; El-Hami, Khalil; Eid, Mohamed; Si, Chaorun

2017-09-12

This paper carries out a preliminary study for the elastic properties of single walled carbon nanotube (SWCNT) thin film. The SWCNT thin films (~250 nm) are prepared by a simple and cost effective method of spin-coating technology. Nanoindentation test with a Berkovich indenter is used to determine the hardness and elastic modulus of the SWCNT thin film. It is important to note that the elastic properties of SWCNT film are indirectly derived from the information of load and displacement of the indenter under certain assumptions, deviation of the 'test value' is inevitable. In this regard, uncertainty analysis is an effective process in guarantying the validity of the material properties. This paper carries out uncertainty estimation for the tested elastic properties of SWCNT film by nanoindentation. Experimental results and uncertainty analysis indicates that nanoindentation test could be an effective and reliable method in determine the elastic properties of SWCNT thin film. Moreover, the obtained values of hardness and elastic modulus can further benefit the design of SWCNT thin film based components.

The Anti-inflammatory Drug Indomethacin Alters Nanoclustering in Synthetic and Cell Plasma Membranes*

PubMed Central

Zhou, Yong; Plowman, Sarah J.; Lichtenberger, Lenard M.; Hancock, John F.

2010-01-01

The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. Fluorescence lifetime imaging of cells expressing lipid-anchored probes revealed that treatment of BHK cells with therapeutic levels of indomethacin enhances cholesterol-dependent nanoclustering, but not cholesterol-independent nanoclustering. Immuno-electron microscopy and quantitative spatial mapping of intact plasma membrane sheets similarly showed a selective effect of indomethacin on promoting cholesterol-dependent, but not cholesterol-independent, nanoclustering. To further evaluate the biophysical effects of indomethacin, we measured fluorescence polarization of the phase-sensitive probe Laurdan and FRET between phase-partitioning probes in model bilayers. Therapeutic levels of indomethacin enhanced phase seperation in DPPC/DOPC/Chol (1:1:1) and DPPC/Chol membranes in a temperature-dependent manner, but had minimal effect on the phase behavior of pure DOPC at any temperature. Taken together, the imaging results on intact epithelial cells and the biophysical assays of model membranes suggest that indomethacin can enhance phase separation and stabilize cholesterol-dependent nanoclusters in biological membranes. These effects on membrane lateral heterogeneity may have significant consequences for cell signaling cascades that are assembled on the plasma membrane. PMID:20826816

Solid-state, ambient-operation thermally activated delayed fluorescence from flexible, non-toxic gold-nanocluster thin films: towards the development of biocompatible light-emitting devices

NASA Astrophysics Data System (ADS)

Talite, M. J. A.; Lin, H. T.; Jiang, Z. C.; Lin, T. N.; Huang, H. Y.; Heredia, E.; Flores, A.; Chao, Y. C.; Shen, J. L.; Lin, C. A. J.; Yuan, C. T.

2016-08-01

Luminescent gold nanoclusters (AuNCs) with good biocompatibility have gained much attention in bio-photonics. In addition, they also exhibit a unique photo-physical property, namely thermally activated delayed fluorescence (TADF), by which both singlet and triplet excitons can be harvested. The combination of their non-toxic material property and unique TADF behavior makes AuNCs biocompatible nano-emitters for bio-related light-emitting devices. Unfortunately, the TADF emission is quenched when colloidal AuNCs are transferred to solid states under ambient environment. Here, a facile, low-cost and effective method was used to generate efficient and stable TADF emissions from solid AuNCs under ambient environment using polyvinyl alcohol as a solid matrix. To unravel the underlying mechanism, temperature-dependent static and transient photoluminescence measurements were performed and we found that two factors are crucial for solid TADF emission: small energy splitting between singlet and triplet states and the stabilization of the triplet states. Solid TADF films were also deposited on the flexible plastic substrate with patterned structures, thus mitigating the waveguide-mode losses. In addition, we also demonstrated that warm white light can be generated based on a co-doped single emissive layer, consisting of non-toxic, solution-processed TADF AuNCs and fluorescent carbon dots under UV excitation.

The fourth crystallographic closest packing unveiled in the gold nanocluster crystal

NASA Astrophysics Data System (ADS)

Gan, Zibao; Chen, Jishi; Wang, Juan; Wang, Chengming; Li, Man-Bo; Yao, Chuanhao; Zhuang, Shengli; Xu, An; Li, Lingling; Wu, Zhikun

2017-03-01

Metal nanoclusters have recently attracted extensive interest not only for fundamental scientific research, but also for practical applications. For fundamental scientific research, it is of major importance to explore the internal structure and crystallographic arrangement. Herein, we synthesize a gold nanocluster whose composition is determined to be Au60S6(SCH2Ph)36 by using electrospray ionization mass spectrometry and single crystal X-ray crystallography (SCXC). SCXC also reveals that Au60S6(SCH2Ph)36 consists of a fcc-like Au20 kernel protected by a pair of giant Au20S3(SCH2Ph)18 staple motifs, which contain 6 tetrahedral-coordinate μ4-S atoms not previously reported in the Au-S interface. Importantly, the fourth crystallographic closest-packed pattern, termed 6H left-handed helical (6HLH) arrangement, which results in the distinct loss of solid photoluminescence of amorphous Au60S6(SCH2Ph)36, is found in the crystals of Au60S6(SCH2Ph)36. The solvent-polarity-dependent solution photoluminescence is also demonstrated. Overall, this work provides important insights about the structure, Au-S bonding and solid photoluminescence of gold nanoclusters.

Prereduction of Metal Oxides via Carbon Plasma Treatment for Efficient and Stable Electrocatalytic Hydrogen Evolution.

PubMed

Zhang, Yongqi; Ouyang, Bo; Xu, Kun; Xia, Xinhui; Zhang, Zheng; Rawat, Rajdeep Singh; Fan, Hong Jin

2018-04-01

Prereduction of transition metal oxides is a feasible and efficient strategy to enhance their catalytic activity for hydrogen evolution. Unfortunately, the prereduction via the common H 2 annealing method is unstable for nanomaterials during the hydrogen evolution process. Here, using NiMoO 4 nanowire arrays as the example, it is demonstrated that carbon plasma (C-plasma) treatment can greatly enhance both the catalytic activity and the long-term stability of transition metal oxides for hydrogen evolution. The C-plasma treatment has two functions at the same time: it induces partial surface reduction of the NiMoO 4 nanowire to form Ni 4 Mo nanoclusters, and simultaneously deposits a thin graphitic carbon shell. As a result, the C-plasma treated NiMoO 4 can maintain its array morphology, chemical composition, and catalytic activity during long-term intermittent hydrogen evolution process. This work may pave a new way for simultaneous activation and stabilization of transition metal oxide-based electrocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bulky Counterions: Enhancing the Two-Photon Excited Fluorescence of Gold Nanoclusters.

PubMed

Bertorelle, Franck; Moulin, Christophe; Soleilhac, Antonin; Comby-Zerbino, Clothilde; Dugourd, Philippe; Russier-Antoine, Isabelle; Brevet, Pierre-François; Antoine, Rodolphe

2018-01-19

Increasing fluorescence quantum yields of ligand-protected gold nanoclusters has attracted wide research interest. The strategy consisting in using bulky counterions has been found to dramatically enhance the fluorescence. In this Communication, we push forward this concept to the nonlinear optical regime. We show that by an appropriate choice of bulky counterions and of solvent, a 30-fold increase in two-photon excited fluorescence (TPEF) signal at ≈600 nm for gold nanoclusters can be obtained. This would correspond to a TPEF cross-section in the range of 0.1 to 1 GM. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold nanoclusters confined in a supercage of Y zeolite for aerobic oxidation of HMF under mild conditions.

PubMed

Cai, Jiaying; Ma, Hong; Zhang, Junjie; Song, Qi; Du, Zhongtian; Huang, Yizheng; Xu, Jie

2013-10-11

Au nanoclusters with an average size of approximately 1 nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furandicarboxylic acid (FDCA). It achieved >99 % yield of 2,5-furandicarboxylic acid in water under mild conditions (60 °C, 0.3 MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO2 , CeO2 , and Mg(OH)2 ) and channel-type zeolites (ZSM-5 and H-MOR). Detailed characterizations, such as X-ray diffraction, transmission electron microscopy, N2 -physisorption, and H2 -temperature-programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combination of active targeting, enzyme-triggered release and fluorescent dye into gold nanoclusters for endomicroscopy-guided photothermal/photodynamic therapy to pancreatic ductal adenocarcinoma.

PubMed

Li, Hui; Wang, Ping; Deng, Yunxiang; Zeng, Meiying; Tang, Yan; Zhu, Wei-Hong; Cheng, Yingsheng

2017-09-01

Pancreatic ductal adenocarcinoma (PDAC) is one of the most devastating malignancies in patients, and there is an urgent need for an effective treatment method. Herein, we report a novel gold nanocluster-based platform for confocal laser endomicroscopy-guided photothermal therapy (PTT)/photodynamic therapy (PDT) for PDAC, which consists of four components: the PTT-carrier gold nanocluster, an active targeting ligand U11 peptide, a Cathepsin E (CTSE)-sensitive PDT therapy prodrug, and a CTSE-sensitive imaging agent (cyanine dye Cy5.5). Due to the strong coupling among cross-linked gold nanoparticles (AuNPs), the surface plasmon resonance peak of nanoclusters shifts to the near-infrared (NIR) region, thus making the nanoclusters useful in the effective PTT therapy. In the system, the labeling of nanoclusters with U11 peptide can distinctly increase their affinity and accelerate their uptake by pancreatic cancer cells. Cell apoptosis staining demonstrates that, upon incorporation of the uPAR-targeted unit, the antitumor efficacy of CTSE-sensitive nanocluster AuS-U11 is significantly enhanced with respect to that of the non-targeted nanocluster AuS-PEG and the insensitive nanocluster AuC-PEG. In vivo and ex vivo optical imaging confirms the high accumulation of AuS-U11 in the in situ pancreatic tumor model. Therapeutic studies further show that the combination of active targeting for tumor tissue, enzyme-triggered drug release of 5-ALA and fluorescent dye Cy5.5 in nanoclusters AuS-U11 could achieve optimal therapeutic efficacy with endomicroscopy-guided photothermal/photodynamic therapy with minimal side effects. As a consequence, the delicate gold nanocluster concept provides a promising strategy to enhance the therapy efficiency in the most challenging PDAC treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Exploring Strategies for Labeling Viruses with Gold Nanoclusters through Non-equilibrium Molecular Dynamics Simulations.

PubMed

Pohjolainen, Emmi; Malola, Sami; Groenhof, Gerrit; Häkkinen, Hannu

2017-09-20

Biocompatible gold nanoclusters can be utilized as contrast agents in virus imaging. The labeling of viruses can be achieved noncovalently but site-specifically by linking the cluster to the hydrophobic pocket of a virus via a lipid-like pocket factor. We have estimated the binding affinities of three different pocket factors of echovirus 1 (EV1) in molecular dynamics simulations combined with non-equilibrium free-energy calculations. We have also studied the effects on binding affinities with a pocket factor linked to the Au 102 pMBA 44 nanocluster in different protonation states. Although the absolute binding affinities are over-estimated for all the systems, the trend is in agreement with recent experiments.3 Our results suggest that the natural pocket factor (palmitic acid) can be replaced by molecules pleconaril (drug) and its derivative Kirtan1 that have higher estimated binding affinities. Our results also suggest that including the gold nanocluster does not decrease the affinity of the pocket factor to the virus, but the affinity is sensitive to the protonation state of the nanocluster, i.e., to pH conditions. The methodology introduced in this work helps in the design of optimal strategies for gold-virus bioconjugation for virus detection and manipulation.

Glutathione-capped gold nanoclusters as photosensitizers. Visible light-induced hydrogen generation in neutral water.

PubMed

Chen, Yong-Siou; Kamat, Prashant V

2014-04-23

Glutathione-capped metal nanoclusters (Aux-GSH NCs) which exhibit molecular-like properties are employed as a photosensitizer for hydrogen generation in a photoelectrochemical cell (PEC) and a photocatalytic slurry reactor. The reversible reduction (E(0) = -0.63 V vs RHE) and oxidation (E(0) = 0.97 and 1.51 V vs RHE) potentials of these metal nanoclusters make them suitable for driving the water-splitting reaction. When a mesoscopic TiO2 film sensitized by Aux-GSH NCs is used as the photoanode with a Pt counter electrode in aqueous buffer solution (pH = 7), we observe significant photocurrent activity under visible light (400-500 nm) excitation. Additionally, sensitizing Pt/TiO2 nanoparticles with Aux-GSH NCs in an aqueous slurry system and irradiating with visible light produce H2 at a rate of 0.3 mmol of hydrogen/h/g of Aux-GSH NCs. The rate of H2 evolution is significantly enhanced (∼5 times) when a sacrificial donor, such as EDTA, is introduced into the system. Using metal nanoclusters as a photosensitizer for hydrogen generation lays the foundation for the future exploration of other metal nanoclusters with well-controlled numbers of metal atoms and capping ligands.

Stabilizing subnanometer Ag(0) nanoclusters by thiolate and diphosphine ligands and their crystal structures

NASA Astrophysics Data System (ADS)

Yang, Huayan; Wang, Yu; Zheng, Nanfeng

2013-03-01

The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions.The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions. Electronic supplementary information (ESI) available: Experimental details, more pictures of the structure and XPS spectra of the clusters. CCDC 916463 and 916464. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3nr34328f

Structure evolution and thermoelectric properties of carbonized polydopamine thin films

DOE PAGES

Li, Haoqi; Aulin, Yaroslav V.; Frazer, Laszlo; ...

2017-02-13

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. Finally, the largest room-temperature ZT of 2 × 10 –4 was obtained on samples heat-treated at 800 °C, which is higher than that of reducedmore » graphene oxide.« less

A fluorescence detection of D-penicillamine based on Cu(2+)-induced fluorescence quenching system of protein-stabilized gold nanoclusters.

PubMed

Wang, Peng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

2015-01-25

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

A nanocluster-based fluorescent sensor for sensitive hemoglobin detection.

PubMed

Yang, Dongqin; Meng, Huijie; Tu, Yifeng; Yan, Jilin

2017-08-01

In this report, a fluorescence sensor for sensitive detection of hemoglobin was developed. Gold nanoclusters were first synthesized with bovine serum albumin. It was found that both hydrogen peroxide and hemoglobin could weakly quench the fluorescence from the gold nanoclusters, but when these two were applied onto the nanolcusters simultaneously, a much improved quenching was resulted. This enhancing effect was proved to come from the catalytic generation of hydroxyl radical by hemoglobin. Under an optimized condition, the quenching linearly related to the concentration of hemoglobin in the range of 1-250nM, and a limit of detection as low as 0.36nM could be obtained. This provided a sensitive means for the quantification of Hb. The sensor was then successfully applied for blood analyses with simple sample pretreatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Formation of manganese nanoclusters in a sputtering/aggregation source and the roles of individual operating parameters

NASA Astrophysics Data System (ADS)

Khojasteh, Malak; Kresin, Vitaly V.

2016-12-01

We describe the production of size selected manganese nanoclusters using a dc magnetron sputtering/aggregation source. Since nanoparticle production is sensitive to a range of overlapping operating parameters (in particular, the sputtering discharge power, the inert gas flow rates, and the aggregation length) we focus on a detailed map of the influence of each parameter on the average nanocluster size. In this way it is possible to identify the main contribution of each parameter to the physical processes taking place within the source. The discharge power and argon flow supply the atomic vapor, and argon also plays the crucial role in the formation of condensation nuclei via three-body collisions. However, neither the argon flow nor the discharge power have a strong effect on the average nanocluster size in the exiting beam. Here the defining role is played by the source residence time, which is governed by the helium supply and the aggregation path length. The size of mass selected nanoclusters was verified by atomic force microscopy of deposited particles.

Light-induced Self-Assembly and Diffusion of Nanoclusters

NASA Astrophysics Data System (ADS)

Lian, Wenxuan

Novel methods to build multiple types of three-dimensional structures from various nanoscale components are the most exciting and challenging questions in nano-science. The properties of the assembled structures can be potentially and designed, but the development of such approaches is challenging. In order to realize such rational assembly, a tunable interaction medium is often introduced into the system. Soft matter, such as polymers, surfactants and biomolecules are used to modify the surfaces of the nanoscale building blocks. Deoxyribonucleic acid (DNA) strands are known as polynucleotides since they are composed of simpler units called nucleotides. There are unique base pairing rules that are predictable and programmable, which can be used to regulate self-assembly process with high degree of control. Besides controlling static structure, it is important to develop methods for controlling systems in dynamic matter, with chemical stimuli or external fields. For example, here we study the use of azobezene-trimethylammonium bromide (AzoTAB) as a molecular agent that can control self-assembly via light excitation. In this thesis, DNA assisted self-assembly was conducted. The ability of AzoTAB as a light induced surfactant to control DNA assisted self-assembly was confirmed. The mechanism of AzoTAB as a light controlled self-assembly promoter was studied. In the second project, diffusion of nanoclusters was studied. The presence of polymers brings strong entanglement with nanoclusters. This entanglement is more obvious when the nanocluster is a framed structure like the octahedron in the study. The diffusion coefficient of the octahedron becomes larger during traveling. The following up studies are required to elucidate the origin of the observed effect.

Reactive magnetron sputtering of N-doped carbon thin films on quartz glass for transmission photocathode applications

NASA Astrophysics Data System (ADS)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Sasinková, V.; Boháček, P.; Arbet, J.

2018-03-01

N-doped carbon thin films were deposited on a silicon substrate and quartz glass by RF reactive magnetron sputtering using a carbon target and an Ar+N2 gas mixture. During the magnetron sputtering, the substrate holder temperatures was kept at 800 °C. The carbon film thickness on the silicon substrate was about 70 nm, while on the quartz glass it was in the range 15 nm – 60 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy was used to evaluate the intensity ratios I D/I G of the D and G peaks of the carbon films. The transmission photocathodes prepared were placed in the hollow-cathode assembly of a Pierce-structure DC gun to produce photoelectrons. The quantum efficiency (QE) was calculated from the laser energy and cathode charge measured. The properties of the transmission photocathodes based on semitransparent N-doped carbon thin films on quartz glass and their potential for application in DC gun technology are discussed.

Plasmon generation in sputtered Ga-doped MgZnO thin films for solar cell applications

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

Awasthi, Vishnu; Garg, Vivek; Sengar, Brajendra S.

2016-06-21

The crystalline, electrical, morphological, optical properties and plasmonic behaviour of Ga doped MgZnO (GMZO) thin films grown at different substrate temperatures (200–600 °C) by a dual ion beam sputtering (DIBS) system are investigated. Transmittance value of more than ∼94% in 400–1000 nm region is observed for all GMZO films. The particle plasmon features can be detected in the absorption coefficient spectra of GMZO grown at 500 and 600 °C in the form of a peak at ∼4.37 eV, which corresponds to a plasmon resonance peak of nanoclusters formed in GMZO. The presence of such plasmonic features is confirmed by ultraviolet photoelectron spectroscopy measurements. Themore » values of particle plasmon resonance energy of various nanoclusters are in the range of solar spectrum, and these can easily be tuned and excited at the desirable wavelengths while optimizing the efficiency of solar cells (SCs) by simple alteration of DIBS growth temperature. These nanoclusters are extremely promising to enhance the optical scattering and trapping of the incident light, which increases the optical path length in the absorber layer of cost-effective SCs and eventually increases its efficiency.« less

Pathways to Mesoporous Resin/Carbon Thin Films with Alternating Gyroid Morphology

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

Zhang, Qi; Matsuoka, Fumiaki; Suh, Hyo Seon

Three-dimensional (3D) mesoporous thin films with sub-100 nm periodic lattices are of increasing interest as templates for a number of nanotechnology applications, yet are hard to achieve with conventional top-down fabrication methods. Block copolymer self-assembly derived mesoscale structures provide a toolbox for such 3D template formation. In this work, single (alternating) gyroidal and double gyroidal mesoporous thin-film structures are achieved via solvent vapor annealing assisted co-assembly of poly(isoprene-block-styrene-block-ethylene oxide) (PI-b-PS-b-PEO, ISO) and resorcinol/phenol formaldehyde resols. In particular, the alternating gyroid thin-film morphology is highly desirable for potential template backfilling processes as a result of the large pore volume fraction. Inmore » situ grazing-incidence small-angle X-ray scattering during solvent annealing is employed as a tool to elucidate and navigate the pathway complexity of the structure formation processes. The resulting network structures are resistant to high temperatures provided an inert atmosphere. The thin films have tunable hydrophilicity from pyrolysis at different temperatures, while pore sizes can be tailored by varying ISO molar mass. A transfer technique between substrates is demonstrated for alternating gyroidal mesoporous thin films, circumventing the need to re-optimize film formation protocols for different substrates. Increased conductivity after pyrolysis at high temperatures demonstrates that these gyroidal mesoporous resin/carbon thin films have potential as functional 3D templates for a number of nanomaterials applications.« less

First-principles calculated decomposition pathways for LiBH4 nanoclusters

PubMed Central

Huang, Zhi-Quan; Chen, Wei-Chih; Chuang, Feng-Chuan; Majzoub, Eric H.; Ozoliņš, Vidvuds

2016-01-01

We analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathways markedly differ from those in bulk LiBH4. While experiments have found that the bulk material decomposes into LiH and B, with Li2B12H12 as a kinetically inhibited intermediate phase, (LiBH4)n nanoclusters with n ≤ 12 are predicted to decompose into mixed LinBn clusters via a series of intermediate clusters of LinBnHm (m ≤ 4n). The calculated pressure-composition isotherms and temperature-pressure isobars exhibit sloping plateaus due to finite size effects on reaction thermodynamics. Generally, decomposition temperatures of free-standing clusters are found to increase with decreasing cluster size due to thermodynamic destabilization of reaction products. PMID:27189731

Large-area, electronically monodisperse, aligned single-walled carbon nanotube thin films fabricated by evaporation-driven self-assembly.

PubMed

Shastry, Tejas A; Seo, Jung-Woo T; Lopez, Josue J; Arnold, Heather N; Kelter, Jacob Z; Sangwan, Vinod K; Lauhon, Lincoln J; Marks, Tobin J; Hersam, Mark C

2013-01-14

By varying the evaporation conditions and the nanotube and surfactant concentrations, large-area, aligned single-walled carbon nanotube (SWCNT) thin films are fabricated from electronically monodisperse SWCNT solutions by evaporation-driven self-assembly with precise control over the thin film growth geometry. Tunability is possible from 0.5 μm stripes to continuous thin films. The resulting SWCNT thin films possess highly anisotropic electrical and optical properties that are well suited for transparent conductor applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Linear and Nonlinear Optical Response in Silver Nanoclusters: Insight from a Computational Investigation (Postprint)

DTIC Science & Technology

2016-01-05

applying DFT and TDDFT. Synthesis and optical characterization of the silver glutathione nanoclusters Ag32(SG)19 and Ag15(SG)11 were recently reported by...Ag15. Synthesis and optical characterization of the Ag32(SG)19, Ag31(SG)19, and Ag15(SG)11 silver glutathione nanoclusters have been reported.19,20 A...Barnett, R. N.; Monahan, B. M.; Kirschbaum, K.; Griffith, W. P.; Whetten, R. L.; Landman, U.; Bigioni, T. P. Ultrastable Silver Nanoparticles . Nature

Conversion treatment of thin titanium layer deposited on carbon steel

NASA Astrophysics Data System (ADS)

Benarioua, Younes; Wendler, Bogdan; Chicot, Didier

2018-05-01

The present study has been conducted in order to obtain titanium carbide layer using a conversion treatment consisting of two main steps. In the first step a thin pure titanium layer was deposited on 120C4 carbon steel by PVD. In the second step, the carbon atoms from the substrate diffuse to the titanium coating due to a vacuum annealing treatment and the Ti coating transforms into titanium carbide. Depending on the annealing temperature a partial or complete conversion into TiC is obtained. The hardness of the layer can be expected to differ depending on the processing temperatures. By a systematic study of the hardness as a function of the applied load, we confirm the process of growth of the layer.

Aqueous synthesis of near-infrared highly fluorescent platinum nanoclusters

NASA Astrophysics Data System (ADS)

García Fernández, Jenifer; Trapiella-Alfonso, Laura; Costa-Fernández, José M.; Pereiro, Rosario; Sanz-Medel, Alfredo

2015-05-01

A one-step synthesis of near infrared fluorescent platinum nanoclusters (PtNCs) in aqueous medium is described. The proposed optimized procedure for PtNC synthesis is rather simple, fast and it is based on the direct metal reduction with NaBH4. Bidentated thiol ligands (lipoic acid) were selected as nanoclusters stabilizers in water media. The structural characterization revealed attractive features of the PtNCs, including small size, high water solubility, near-infrared luminescence centered at 680 nm, long-term stability and the highest quantum yield in water reported so far (47%) for PtNCs. Moreover, their stability in different pH media and an ionic strength of 0.2 M NaCl was studied and no significant changes in fluorescence emission were detected. In brief, they offer a new type of fluorescent noble metal nanoprobe with a great potential to be applied in several fields, including biolabeling and imaging experiments.

Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance

NASA Astrophysics Data System (ADS)

Zhang, Xiao-Dong; Luo, Zhentao; Chen, Jie; Song, Shasha; Yuan, Xun; Shen, Xiu; Wang, Hao; Sun, Yuanming; Gao, Kai; Zhang, Lianfeng; Fan, Saijun; Leong, David Tai; Guo, Meili; Xie, Jianping

2015-03-01

Radiotherapy is often the most straightforward first line cancer treatment for solid tumors. While it is highly effective against tumors, there is also collateral damage to healthy proximal tissues especially with high doses. The use of radiosensitizers is an effective way to boost the killing efficacy of radiotherapy against the tumor while drastically limiting the received dose and reducing the possible damage to normal tissues. Here, we report the design and application of a good radiosensitizer by using ultrasmall Au29-43(SG)27-37 nanoclusters (<2 nm) with a naturally-occurring peptide (e.g., glutathione or GSH) as the protecting shell. The GSH-coated Au29-43(SG)27-37 nanoclusters can escape the RES absorption, leading to a good tumor uptake (~8.1% ID/g at 24 h post injection). As a result, the as-designed Au nanoclusters led to a strong enhancement for radiotherapy, as well as a negligible damage to normal tissues. After the treatment, the ultrasmall Au29-43(SG)27-37 nanoclusters can be efficiently cleared by the kidney, thereby avoiding potential long-term side-effects caused by the accumulation of gold atoms in the body. Our data suggest that the ultrasmall peptide-protected Au nanoclusters are a promising radiosensitizer for cancer radiotherapy.

Al-C hybrid nanoclustered anodes for lithium ion batteries with high electrical capacity and cyclic stability.

PubMed

Park, Ji Hun; Hudaya, Chairul; Kim, A-Young; Rhee, Do Kyung; Yeo, Seon Ju; Choi, Wonchang; Yoo, Pil J; Lee, Joong Kee

2014-03-18

Structurally regulated and hybridized Al-C nanoclusters are prepared from C60 and Al precursors by thermal evaporation-combined plasma-enhanced chemical vapour deposition. The resulting Al-C hybrid nanoclustered anodes for Li-ion batteries exhibit a high reversible capacity of >900 mA h g(-1) at an optimized current density of 6 A g(-1) for over 100 cycles.

Theoretical Investigation of the Structural Stabilities of Ceria Surfaces and Supported Metal Nanocluster in Vapor and Aqueous Phases

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

Ren, Zhibo; Liu, Ning; Chen, Biaohua

Understanding the structural stability and dynamics at the interface between the solid metal oxide and aqueous phase is significant in a variety of industrial applications including heterogeneous catalysis and environmental remediation. In the present work, the stabilities of three low-index ceria (CeO2) surfaces, i.e., (111), (110) and (100) in vapor and aqueous phases were studied using ab initio molecular dynamics simulations and density functional theory (DFT) calculations. Gibbs surface free energies as a function of temperature, water partial pressure, and water coverages were calculated using DFT based atomistic thermodynamic approach. On the basis of surface free energies, the morphology andmore » exposed surface structures of the CeO2 nanoparticle were predicted using Wulff construction principle. It is found that the partially hydroxylated (111) and (100) are two major surface structures of CeO2 nanoparticles in vapor phase at ambient temperature (300 K). As the temperature increases, the fully dehydrated (111) surface gradually becomes the most dominant surface structure. While in aqueous phase, the exposed surface of the CeO2 nanoparticle is dominated by the hydroxylated (110) structure at 393 K. Finally, the morphology and stability of a cuboctahedron Pt13 nanocluster supported on CeO2 surfaces in both gas and aqueous phases were investigated. In gas phase, the supported Pt13 nanocluster has the tendency to wetting the CeO2 surface due to the strong metal-support interaction. The calculated interaction energies suggest the CeO2(110) surface provides the best stability for the Pt13 nanocluster. The CeO2 supported Pt13 nanoclusters are oxidized. Compared to the gas phase, the morphology of the CeO2 supported Pt13 nanocluster is less distorted due to the solvation effect provided by surrounding water molecules in aqueous phase. More electrons are transferred from the Pt13 nanocluster to the CeO2 support, implying the supported Pt13 nanocluster is

Layered Double Hydroxide Nanoclusters: Aqueous, Concentrated, Stable, and Catalytically Active Colloids toward Green Chemistry.

PubMed

Tokudome, Yasuaki; Morimoto, Tsuyoshi; Tarutani, Naoki; Vaz, Pedro D; Nunes, Carla D; Prevot, Vanessa; Stenning, Gavin B G; Takahashi, Masahide

2016-05-24

Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems.

DFT study of hydrogen production from formic acid decomposition on Pd-Au alloy nanoclusters

NASA Astrophysics Data System (ADS)

Liu, D.; Gao, Z. Y.; Wang, X. C.; Zeng, J.; Li, Y. M.

2017-12-01

Recently, it has been reported that the hydrogen production rate of formic acid decomposition can be significantly increased using Pd-Au binary alloy nano-catalysts [Wang et al. J. Mater. Chem. A 1 (2013) 12721-12725]. To explain the reaction mechanism of this alloy catalysis method, formic acid decomposition reactions on pure Pd and Pd-Au alloy nanoclusters are studied via density functional theory simulations. The simulation results indicate that the addition of inert element Au would not influence formic acid decomposition on Pd surface sites of Pd-Au alloy nanoclusters. On the other hand, the existence of Au surface sites brings relative weak hydrogen atom adsorption. On Pd-Au alloy nanoclusters, the dissociated hydrogen atoms from formic acid are easier to combine as hydrogen molecules than that on pure Pd clusters. Via the synergetic effect between Pd and Au, both formic acid decomposition and hydrogen production are events with large probability, which eventually results in high hydrogen production rate.

First-principles calculated decomposition pathways for LiBH 4 nanoclusters

DOE PAGES

Huang, Zhi -Quan; Chen, Wei -Chih; Chuang, Feng -Chuan; ...

2016-05-18

Here, we analyze thermodynamic stability and decomposition pathways of LiBH 4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH 4) n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li) n, (B) n, (LiB) n, (LiH) n, and Li 2B nH n; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathwaysmore » markedly differ from those in bulk LiBH 4. While experiments have found that the bulk material decomposes into LiH and B, with Li 2B 12H 12 as a kinetically inhibited intermediate phase, (LiBH 4) n nanoclusters with n ≤ 12 are predicted to decompose into mixed Li nB n clusters via a series of intermediate clusters of Li nB nH m (m ≤ 4n). The calculated pressure-composition isotherms and temperature-pressure isobars exhibit sloping plateaus due to finite size effects on reaction thermodynamics. Generally, decomposition temperatures of free-standing clusters are found to increase with decreasing cluster size due to thermodynamic destabilization of reaction products.« less

The expanding universe of thiolated gold nanoclusters and beyond.

PubMed

Jiang, De-en

2013-08-21

Thiolated gold nanoclusters form a universe of their own. Researchers in this field are constantly pushing the boundary of this universe by identifying new compositions and in a few "lucky" cases, solving their structures. Such solved structures, even if there are only few, provide important hints for predicting the many identified compositions that are yet to be crystallized or structure determined. Structure prediction is the most pressing issue for a computational chemist in this field. The success of the density functional theory method in gauging the energetic ordering of isomers for thiolated gold clusters has been truly remarkable, but to predict the most stable structure for a given composition remains a great challenge. In this feature article from a computational chemist's point of view, the author shows how one understands and predicts structures for thiolated gold nanoclusters based on his old and new results. To further entertain the reader, the author also offers several "imaginative" structures, claims, and challenges for this field.

One-dimensional ordering of Ge nanoclusters along atomically straight steps of Si(111)

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

Sekiguchi, Takeharu; Yoshida, Shunji; Itoh, Kohei M.

2007-01-01

Ge nanostructures grown by molecular beam epitaxy on a vicinal Si(111) surface with atomically well-defined steps are studied by means of scanning tunneling microscopy and spectroscopy. When the substrate temperature during deposition is around 250 degree sign C, Ge nanoclusters of diameters less than 2.0 nm form a one-dimensional array of the periodicity 2.7 nm along each step. This self-organization is due to preferential nucleation of Ge on the unfaulted 7x7 half-unit cells at the upper step edges. Scanning tunneling spectroscopy reveals localized electronic states of the nanoclusters.

Development of an ultra-thin film comprised of a graphene membrane and carbon nanotube vein support.

PubMed

Lin, Xiaoyang; Liu, Peng; Wei, Yang; Li, Qunqing; Wang, Jiaping; Wu, Yang; Feng, Chen; Zhang, Lina; Fan, Shoushan; Jiang, Kaili

2013-01-01

Graphene, exhibiting superior mechanical, thermal, optical and electronic properties, has attracted great interest. Considering it being one-atom-thick, and the reduced mechanical strength at grain boundaries, the fabrication of large-area suspended chemical vapour deposition graphene remains a challenge. Here we report the fabrication of an ultra-thin free-standing carbon nanotube/graphene hybrid film, inspired by the vein-membrane structure found in nature. Such a square-centimetre-sized hybrid film can realize the overlaying of large-area single-layer chemical vapour deposition graphene on to a porous vein-like carbon nanotube network. The vein-membrane-like hybrid film, with graphene suspended on the carbon nanotube meshes, possesses excellent mechanical performance, optical transparency and good electrical conductivity. The ultra-thin hybrid film features an electron transparency close to 90%, which makes it an ideal gate electrode in vacuum electronics and a high-performance sample support in transmission electron microscopy.

Methanol, ethanol and hydrogen sensing using metal oxide and metal (TiO(2)-Pt) composite nanoclusters on GaN nanowires: a new route towards tailoring the selectivity of nanowire/nanocluster chemical sensors.

PubMed

Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Mulpuri, Rao V

2012-05-04

We demonstrate a new method for tailoring the selectivity of chemical sensors using semiconductor nanowires (NWs) decorated with metal and metal oxide multicomponent nanoclusters (NCs). Here we present the change of selectivity of titanium dioxide (TiO(2)) nanocluster-coated gallium nitride (GaN) nanowire sensor devices on the addition of platinum (Pt) nanoclusters. The hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO(2) and/or Pt nanoclusters (NCs) using the sputtering technique. This paper present the sensing characteristics of GaN/(TiO(2)-Pt) nanowire-nanocluster (NWNC) hybrids and GaN/(Pt) NWNC hybrids, and compare their selectivity with that of the previously reported GaN/TiO(2) sensors. The GaN/TiO(2) NWNC hybrids showed remarkable selectivity to benzene and related aromatic compounds, with no measurable response for other analytes. Addition of Pt NCs to GaN/TiO(2) sensors dramatically altered their sensing behavior, making them sensitive only to methanol, ethanol and hydrogen, but not to any other chemicals we tested. The GaN/(TiO(2)-Pt) hybrids were able to detect ethanol and methanol concentrations as low as 100 nmol mol(-1) (ppb) in air in approximately 100 s, and hydrogen concentrations from 1 µmol mol(-1) (ppm) to 1% in nitrogen in less than 60 s. However, GaN/Pt NWNC hybrids showed limited sensitivity only towards hydrogen and not towards any alcohols. All these hybrid sensors worked at room temperature and are photomodulated, i.e. they responded to analytes only in the presence of ultraviolet (UV) light. We propose a qualitative explanation based on the heat of adsorption, ionization energy and solvent polarity to explain the observed selectivity of the different hybrids. These results are significant from the standpoint of applications requiring room-temperature hydrogen sensing and sensitive alcohol monitoring. These results demonstrate the tremendous potential for

Conduction properties of thin films from a water soluble carbon nanotube/hemicellulose complex

NASA Astrophysics Data System (ADS)

Shao, Dongkai; Yotprayoonsak, Peerapong; Saunajoki, Ville; Ahlskog, Markus; Virtanen, Jorma; Kangas, Veijo; Volodin, Alexander; Van Haesendonck, Chris; Burdanova, Maria; Mosley, Connor D. W.; Lloyd-Hughes, James

2018-04-01

We have examined the conductive properties of carbon nanotube based thin films, which were prepared via dispersion in water by non-covalent functionalization of the nanotubes with xylan, a type of hemicellulose. Measurements of low temperature conductivity, Kelvin probe force microscopy, and high frequency (THz) conductivity elucidated the intra-tube and inter-tube charge transport processes in this material. The measurements show excellent conductive properties of the as prepared thin films, with bulk conductivity up to 2000 S cm-1. The transport results demonstrate that the hemicellulose does not seriously interfere with the inter-tube conductance.

Electrocatalytic activity of spots of electrodeposited noble-metal catalysts on carbon nanotubes modified glassy carbon.

PubMed

Chen, Xingxing; Eckhard, Kathrin; Zhou, Min; Bron, Michael; Schuhmann, Wolfgang

2009-09-15

A strategy for the screening of the electrocatalytic activity of electrocatalysts for possible application in fuel cells and other devices is presented. In this approach, metal nanoclusters (Pt, Au, Ru, and Rh and their codeposits) were prepared using a capillary-based droplet-cell by pulsed electrodeposition in a diffusion-restricted viscous solution. A glassy carbon surface was modified with carbon nanotubes (CNTs) by electrophoretic accumulation and was used as substrate for metal nanoparticle deposition. The formed catalyst spots on the CNT-modified glassy carbon surface were investigated toward their catalytic activity for oxygen reduction as a test reaction employing the redox competition mode of scanning electrochemical microscopy (RC-SECM). Qualitative information on the electrocatalytic activity of the catalysts was obtained by varying the potential applied to the substrate; semiquantitative evaluation was based on the determination of the electrochemically deposited catalyst loading by means of the charge transferred during the metal nanoparticle deposition. Qualitatively, Au showed the highest electrocatalytic activity toward the oxygen reduction reaction (ORR) in phosphate buffer among all investigated single metal catalysts which was attributed to the much higher loading of Au achieved during electrodeposition. Coelectrodeposited Au-Pt catalysts showed a more positive onset potential (-150 mV in RC-SECM experiments) of the ORR in phosphate buffer at pH 6.7. After normalizing the SECM image by the charge during the metal nanocluster deposition which represents the mass loading of the catalyst, Ru showed a higher electrocatalytic activity toward the ORR than Au.

High-Temperature Annealing as a Method for the Silicon Nanoclusters Growth in Stoichiometric Silicon Dioxide

NASA Astrophysics Data System (ADS)

Ivanova, E. V.; Dementev, P. A.; Sitnikova, A. A.; Aleksandrov, O. V.; Zamoryanskaya, M. V.

2018-07-01

A method for the growth of nanocomposite layers in stoichiometric amorphous silicon dioxide is proposed. It is shown that, after annealing at a temperature of 1150°C in nitrogen atmosphere, a layer containing silicon nanoclusters is formed. Silicon nanoclusters have a crystal structure and a size of 3-6 nm. In a film grown on a n-type substrate, a layer of silicon nanoclusters with a thickness of about 10 nm is observed. In the case of a film grown on a p-type substrate, a nanocomposite layer with a thickness of about 100 nm is observed. The difference in the formation of a nanocomposite layer in films on various substrates is associated with the doping of silicon dioxide with impurities from the substrate during the growth of the film. The formation of the nanocomposite layer was confirmed by transmission electron microscopy, XPS and local cathodoluminescence studies.

Preparation of electrochromic thin films by transformation of manganese(II) carbonate

NASA Astrophysics Data System (ADS)

Stojkovikj, Sasho; Najdoski, Metodija; Koleva, Violeta; Demiri, Sani

2013-10-01

A new chemical bath method for deposition of manganese(II) carbonate thin film on electroconductive FTO glass substrates is designed. The homogeneous thin films with thickness in the range of 70 to 500 nm are deposited at about 98 °C from aqueous solution containing urea and MnCl2. The chemical process is based on a low temperature hydrolysis of the manganese complexes with urea. Three types of films are under consideration: as-deposited, annealed and electrochemically transformed thin films. The structure of the films is studied by XRD, IR and Raman spectroscopy. Electrochemical and optical properties are examined in eight different electrolytes (neutral and alkaline) and the best results are achieved in two component aqueous solution of 0.1 M KNO3 and 0.01 M KOH. It is established that the as-deposited MnCO3 film undergoes electrochemically transformation into birnessite-type manganese(IV) oxide films, which exhibit electrochromic color changes (from bright brown to pale yellow and vice versa) with 30% difference in the transmittance of the colored and bleached state at 400 nm.

Fabrication of peptide stabilized fluorescent gold nanocluster/graphene oxide nanocomplex and its application in turn-on detection of metalloproteinase-9.

PubMed

Nguyen, Phuong-Diem; Cong, Vu Thanh; Baek, Changyoon; Min, Junhong

2017-03-15

This study introduces the double-ligands stabilizing gold nanoclusters and the fabrication of gold nanocluster/graphene nanocomplex as a "turn-on" fluorescent probe for the detection of cancer-related enzyme matrix metalloproteinase-9. A facile, one-step approach was developed for the synthesis of fluorescent gold nanoclusters using peptides and mercaptoundecanoic acid as co-templating ligands. The peptide was designed to possess a metalloproteinase-9 cleavage site and to act not only as a stabilizer but also as a targeting ligand for the enzyme detection. The prepared gold nanoclusters show an intense red fluorescence with a broad adsorption spectrum. In the presence of the enzyme, due to the excellent quenching properties and the negligible background of graphene oxide, the developed peptide-gold nanocluster/graphene nanocomplex yielded an intense "turn-on" fluorescent response, which strongly correlated with the enzyme concentration. The limit of detection of the nanocomplex was 0.15nM. The sensor was successfully applied for "turn-on" detection of metalloproteinase-9 secreted from human breast adenocarcinoma MCF-7 cells with high sensitivity, selectivity, significant improvement in terms of detection time and simplicity. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of thin films in boron-carbon-nitrogen ternary system by microwave plasma enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kukreja, Ratandeep Singh

The Boron Carbon Nitorgen (B-C-N) ternary system includes materials with exceptional properties such as wide band gap, excellent thermal conductivity, high bulk modulus, extreme hardness and transparency in the optical and UV range that find application in most fields ranging from micro-electronics, bio-sensors, and cutting tools to materials for space age technology. Interesting materials that belong to the B-C-N ternary system include Carbon nano-tubes, Boron Carbide, Boron Carbon Nitride (B-CN), hexagonal Boron Nitride ( h-BN), cubic Boron Nitride (c-BN), Diamond and beta Carbon Nitride (beta-C3N4). Synthesis of these materials requires precisely controlled and energetically favorable conditions. Chemical vapor deposition is widely used technique for deposition of thin films of ceramics, metals and metal-organic compounds. Microwave plasma enhanced chemical vapor deposition (MPECVD) is especially interesting because of its ability to deposit materials that are meta-stable under the deposition conditions, for e.g. diamond. In the present study, attempt has been made to synthesize beta-carbon nitride (beta-C3N4) and cubic-Boron Nitride (c-BN) thin films by MPECVD. Also included is the investigation of dependence of residual stress and thermal conductivity of the diamond thin films, deposited by MPECVD, on substrate pre-treatment and deposition temperature. Si incorporated CNx thin films are synthesized and characterized while attempting to deposit beta-C3N4 thin films on Si substrates using Methane (CH4), Nitrogen (N2), and Hydrogen (H2). It is shown that the composition and morphology of Si incorporated CNx thin film can be tailored by controlling the sequence of introduction of the precursor gases in the plasma chamber. Greater than 100mum size hexagonal crystals of N-Si-C are deposited when Nitrogen precursor is introduced first while agglomerates of nano-meter range graphitic needles of C-Si-N are deposited when Carbon precursor is introduced first in the

Memory characteristics of metal-oxide-semiconductor structures based on Ge nanoclusters-embedded GeO(x) films grown at low temperature.

PubMed

Lin, Tzu-Shun; Lou, Li-Ren; Lee, Ching-Ting; Tsai, Tai-Cheng

2012-03-01

The memory devices constructed from the Ge-nanoclusters embedded GeO(x) layer deposited by the laser-assisted chemical vapor deposition (LACVD) system were fabricated. The Ge nanoclusters were observed by a high-resolution transmission electron microscopy. Using the capacitance versus voltage (C-V) and the conductance versus voltage (G-V) characteristics measured under various frequencies, the memory effect observed in the C-V curves was dominantly attributed to the charge storage in the Ge nanoclusters. Furthermore, the defects existed in the deposited film and the interface states were insignificant to the memory performances. Capacitance versus time (C-t) measurement was also executed to evaluate the charge retention characteristics. The charge storage and retention behaviors of the devices demonstrated that the Ge nanoclusters grown by the LACVD system at low temperature are promising for memory device applications.

Electrical transport properties in Co nanocluster-assembled granular film

NASA Astrophysics Data System (ADS)

Zhang, Qin-Fu; Wang, Lai-Sen; Wang, Xiong-Zhi; Zheng, Hong-Fei; Liu, Xiang; Xie, Jia; Qiu, Yu-Long; Chen, Yuanzhi; Peng, Dong-Liang

2017-03-01

A Co nanocluster-assembled granular film with three-dimensional cross-connection paralleled conductive paths was fabricated by using the plasma-gas-condensation method in a vacuum environment. The temperature-dependent longitudinal resistivity and anomalous Hall effect of this new type granular film were systematically studied. The longitudinal resistivity of the Co nanocluster-assembled granular film first decreased and then increased with increasing measuring temperature, revealing a minimum value at certain temperature, T min . In a low temperature region ( T < T min ), the barrier between adjacent nanoclusters governed the electrical transport process, and the temperature coefficient of resistance (TCR) showed an insulator-type behavior. The thermal fluctuation-induced tunneling conduction progressively increased with increasing temperature, which led to a decrease in the longitudinal resistivity. In a high temperature region, the TCR showed a metallic-type behavior, which was primarily attributed to the temperature-dependent scattering. Different from the longitudinal resistivity behavior, the saturated anomalous Hall resistivity increased monotonically with increasing measuring temperature. The value of the anomalous Hall coefficient ( R S ) reached 2.3 × 10-9 (Ω cm)/G at 300 K, which was about three orders of magnitude larger than previously reported in blocky single-crystal Co [E. N. Kondorskii, Sov. Phys. JETP 38, 977 (1974)]. Interestingly, the scaling relation ( ρx y A ∝ ρx x γ ) between saturated anomalous Hall resistivity ( ρx y A ) and longitudinal resistivity ( ρ x x ) was divided into two regions by T min . However, after excluding the contribution of tunneling, the scaling relation followed the same rule. The corresponding physical mechanism was also proposed to explain these phenomena.

Nanoclusters as a new family of high temperature superconductors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Halder, Avik; Kresin, Vitaly V.

2017-03-01

Electrons in metal clusters organize into quantum shells, akin to atomic shells in the periodic table. Such nanoparticles are referred to as "superatoms". The electronic shell levels are highly degenerate giving rise to sharp peaks in the density of states, which can enable exceptionally strong electron pairing in certain clusters containing tens to hundreds of atoms. A spectroscopic investigation of size - resolved aluminum nanoclusters has revealed a sharp rise in the density of states near the Fermi level as the temperature decreases towards 100 K. The effect is especially prominent in the closed-shell "magic" cluster Al66 [1, 2]. The characteristics of this behavior are fully consistent with a pairing transition, implying a high temperature superconducting state with Tc < 100K. This value exceeds that of bulk aluminum by two orders of magnitude. As a new class of high-temperature superconductors, such metal nanocluster particles are promising building blocks for high-Tc materials, devices, and networks. ---------- 1. Halder, A., Liang, A., Kresin, V. V. A novel feature in aluminum cluster photoionization spectra and possibility of electron pairing at T 100K. Nano Lett 15, 1410 - 1413 (2015) 2. Halder, A., Kresin, V. V. A transition in the density of states of metal "superatom" nanoclusters and evidence for superconducting pairing at T 100K. Phys. Rev. B 92, 214506 (2015).

Unraveling the Planar-Globular Transition in Gold Nanoclusters through Evolutionary Search

DOE PAGES

Kinaci, Alper; Narayanan, Badri; Sen, Fatih G.; ...

2016-11-28

Au nanoclusters are of technological relevance for catalysis, photonics, sensors, and of fundamental scientific interest owing to planar to globular structural transformation at an anomalously high number of atoms i.e. in the range 12-14. The nature and causes of this transition remain a mystery. In order to unravel this conundrum, high throughput density functional theory (DFT) calculations, coupled with a global structural optimization scheme based on a modified genetic algorithm (GA) are conducted. Furthermore, more than 20,000 Au 12, Au 13, and Au 14 nanoclusters are evaluated. With any DFT functional, globular and planar structures coexist across the size rangemore » of interest. Contrary to what was previously believed, the planar-globular transition is gradual at room temperature rather than a sharp transition. The effects of anionicity, s-d band hybridization and long range interactions on the dimensional transition are quantified by using the structures adjacent to minima. Anionicity marginally changes the relative stability of the clusters. The degree of s-d hybridization is varied via changing the Hubbard U value which corroborate that s-d hybridization alone does not stabilize planar structures. van der Waals interactions, on the other hand, stabilize globular structures. Our results elucidate the balance between the different reasons of the dimensional transition in gold nanoclusters.« less

Electro-optical properties of the metal oxide-carbon thin film system of CdO-LCC

NASA Astrophysics Data System (ADS)

Kokshina, A. V.; Smirnov, A. V.; Razina, A. G.

2016-08-01

This article presents the results of a study electrical and optical properties of the thin film system of CdO-LCC. Cadmium oxide films were obtained by method of thermal oxidation. CdO-LCC thin film system was produced by applying on a CdO film a linear chain carbon film in thickness of 100 nm using the ion-plasma method, after which the obtained system was annealed. The studies showed that the obtained CdO-LCC films are quite transparent in the visible region; it has polycrystalline structure, thickness around 300 nm, the band gap to 2.3 eV. The obtained thin film system has photosensitive properties.

Building machine learning force fields for nanoclusters

NASA Astrophysics Data System (ADS)

Zeni, Claudio; Rossi, Kevin; Glielmo, Aldo; Fekete, Ádám; Gaston, Nicola; Baletto, Francesca; De Vita, Alessandro

2018-06-01

We assess Gaussian process (GP) regression as a technique to model interatomic forces in metal nanoclusters by analyzing the performance of 2-body, 3-body, and many-body kernel functions on a set of 19-atom Ni cluster structures. We find that 2-body GP kernels fail to provide faithful force estimates, despite succeeding in bulk Ni systems. However, both 3- and many-body kernels predict forces within an ˜0.1 eV/Å average error even for small training datasets and achieve high accuracy even on out-of-sample, high temperature structures. While training and testing on the same structure always provide satisfactory accuracy, cross-testing on dissimilar structures leads to higher prediction errors, posing an extrapolation problem. This can be cured using heterogeneous training on databases that contain more than one structure, which results in a good trade-off between versatility and overall accuracy. Starting from a 3-body kernel trained this way, we build an efficient non-parametric 3-body force field that allows accurate prediction of structural properties at finite temperatures, following a newly developed scheme [A. Glielmo et al., Phys. Rev. B 95, 214302 (2017)]. We use this to assess the thermal stability of Ni19 nanoclusters at a fractional cost of full ab initio calculations.

Ultra-thin passivating film induced by vinylene carbonate on highly oriented pyrolytic graphite negative electrode in lithium-ion cell

NASA Astrophysics Data System (ADS)

Matsuoka, O.; Hiwara, A.; Omi, T.; Toriida, M.; Hayashi, T.; Tanaka, C.; Saito, Y.; Ishida, T.; Tan, H.; Ono, S. S.; Yamamoto, S.

We investigated the influence of vinylene carbonate, as an additive molecule, on the decomposition phenomena of electrolyte solution [ethylene carbonate (EC)—ethyl methyl carbonate (EMC) (1:2 by volume) containing 1 M LiPF 6] on a highly oriented pyrolytic graphite (HOPG) negative electrode by using cyclic voltammetry (CV) and atomic force microscopy (AFM). Vinylene carbonate deactivated reactive sites (e.g. radicals and oxides at the defects and the edge of carbon layer) on the cleaved surface of the HOPG negative electrode, and prevented further decomposition of the other solvents there. Further, vinylene carbonate induced an ultra-thin film (less than 1.0 nm in thickness) on the terrace of the basal plane of the HOPG negative electrode, and this film suppressed the decomposition of electrolyte solution on the terraces of the basal plane. We consider that this ultra-thin passivating film is composed of a reduction product of vinylene carbonate (VC), and might have a polymer structure. These induced effects might explain how VC improves the life performance of lithium-ion cells.

Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

PubMed

Poudel, P R; Paramo, J A; Poudel, P P; Diercks, D R; Strzhemechny, Y M; Rout, B; McDaniel, F D

2012-03-01

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001).

PubMed

Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

2015-01-01

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001)

PubMed Central

Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

2015-01-01

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots. PMID:26285135

Correlation study of nanocrystalline carbon doped thin films prepared by a thermionic vacuum arc deposition technique

NASA Astrophysics Data System (ADS)

Dinca-Balan, Virginia; Vladoiu, Rodica; Mandes, Aurelia; Prodan, Gabriel

2017-11-01

The synthesis of Ag, Mg and Si nanocrystalline, embedded in a hydrogen-free amorphous carbon (a-C) matrix, deposited by a high vacuum and free buffer gas technique, were investigated. The films with compact structures and extremely smooth surfaces were prepared using the thermionic vacuum arc method in one electron gun configuration, on glass and silicon substrates. The surface morphology and wettability of the obtained multifunctional thin films were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and free surface energy (FSE) by See System. The results from the TEM measurements show how the Ag, Mg and Si interacted with carbon and the influence these materials have on the thin film structure formation and the grain size distribution. SEM correlated with EDX results reveal a very precise comparative study, regarding the quantity of the elements that morphed into carbides nanostructures. Also, the FSE results prove how different materials in combination with carbon can make changes to the surface properties.

Atomic characterization of Si nanoclusters embedded in SiO2 by atom probe tomography

PubMed Central

2011-01-01

Silicon nanoclusters are of prime interest for new generation of optoelectronic and microelectronics components. Physical properties (light emission, carrier storage...) of systems using such nanoclusters are strongly dependent on nanostructural characteristics. These characteristics (size, composition, distribution, and interface nature) are until now obtained using conventional high-resolution analytic methods, such as high-resolution transmission electron microscopy, EFTEM, or EELS. In this article, a complementary technique, the atom probe tomography, was used for studying a multilayer (ML) system containing silicon clusters. Such a technique and its analysis give information on the structure at the atomic level and allow obtaining complementary information with respect to other techniques. A description of the different steps for such analysis: sample preparation, atom probe analysis, and data treatment are detailed. An atomic scale description of the Si nanoclusters/SiO2 ML will be fully described. This system is composed of 3.8-nm-thick SiO layers and 4-nm-thick SiO2 layers annealed 1 h at 900°C. PMID:21711666

Calculation of density of states of transition metals: From bulk sample to nanocluster

NASA Astrophysics Data System (ADS)

Krasavin, Andrey V.; Borisyuk, Petr V.; Vasiliev, Oleg S.; Zhumagulov, Yaroslav V.; Kashurnikov, Vladimir A.; Kurelchuk, Uliana N.; Lebedinskii, Yuriy Yu.

2018-03-01

A technique is presented of restoring the electronic density of states of the valence band from data of X-ray photoelectron spectroscopy (XPS). The originality of the technique consists in using a stochastic procedure to solve an integral equation relating the density of states and the experimental X-ray photoelectron spectra via the broadening function. To obtain the broadening function, only the XPS spectra of the core levels are needed. The results are presented for bulk sample of gold and tungsten and nanoclusters of tantalum; the possibility of using the results to determine the density of states of low-dimensional structures, including ensembles of metal nanoclusters, is demonstrated.

Surface Enhanced Raman Scattering studies of L-amino acids adsorbed on silver nanoclusters

NASA Astrophysics Data System (ADS)

Botta, Raju; Rajanikanth, A.; Bansal, C.

2015-01-01

Silver nanocluster films were prepared using plasma inert gas phase condensation technique. These were used as Raman active substrates for Surface Enhanced Raman Scattering (SERS) studies of 19 standard L-amino acids adsorbed on the surface of Ag nanoclusters via Agsbnd N bonds. A detailed study of two essential aromatic amino acids viz. L-Phenylalanine and L-Tryptophan showed a correlation between the Raman intensity of the characteristic lines of phenol and indole side chains and their molar concentrations in the range 1 μM-1 mM. This indicates that Raman studies can be used for quantitative determination of the amino acids in proteins.

Fabrication of periodical surface structures by picosecond laser irradiation of carbon thin films: transformation of amorphous carbon in nanographite

NASA Astrophysics Data System (ADS)

Popescu, C.; Dorcioman, G.; Bita, B.; Besleaga, C.; Zgura, I.; Himcinschi, C.; Popescu, A. C.

2016-12-01

Thin films of carbon were synthesized by ns pulsed laser deposition in vacuum on silicon substrates, starting from graphite targets. Further on, the films were irradiated with a picosecond laser source emitting in visible at 532 nm. After tuning of laser parameters, we obtained a film surface covered by laser induced periodical surface structures (LIPSS). They were investigated by optical, scanning electron and atomic force microscopy. It was observed that changing the irradiation angle influences the LIPSS covered area. At high magnification it was revealed that the LIPSS pattern was quite complex, being composed of other small LIPSS islands, interconnected by bridges of nanoparticles. Raman spectra for the non-irradiated carbon films were typical for a-C type of diamond-like carbon, while the LIPSS spectra were characteristic to nano-graphite. The pristine carbon film was hydrophilic, while the LIPSS covered film surface was hydrophobic.

Ab initio study of structural, electronic, optical, and vibrational properties of Zn x S y ( x + y = 2 to 5) nanoclusters

NASA Astrophysics Data System (ADS)

Yadav, P. S.; Pandey, D. K.; Agrawal, S.; Agrawal, B. K.

2010-03-01

An ab initio study of the stability, structural, electronic. and optical properties has been performed for 46 zinc sulfide nanoclusters Zn x S y ( x + y = n = 2 to 5). Five out of them are seen to be unstable as their vibrational frequencies are found to be imaginary. A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO-LUMO gaps and the bond lengths have been obtained for all the clusters. For the ZnS2, ZnS3, and ZnS4 nanoclusters, our stable structures are seen to be different from those obtained earlier by using the effective core potentials. We have also considered the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charges on the atoms, dipole moments, optical properties, vibrational frequencies, infrared intensities, relative infrared intensities, and Raman scattering activities have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each n is found to be most stable. The HOMO-LUMO gap decreases from n = 2-3 and then increases above n = 3. The IP and EA both fluctuate with the cluster size n. The optical absorption is quite weak in visible region but strong in the ultraviolet region in most of the nanoclusters except a few. The optical absorption spectrum or electron energy loss spectrum (EELS) is unique for every nanocluster and may be used to characterize a specific nanocluster. The growth of most stable nanoclusters may be possible in the experiments.

Real-time ab initio KMC simulation of the self-assembly and sintering of bimetallic epitaxial nanoclusters: Au + Ag on Ag(100).

PubMed

Han, Yong; Liu, Da-Jiang; Evans, James W

2014-08-13

Far-from-equilibrium shape and structure evolution during formation and post-assembly sintering of bimetallic nanoclusters is extremely sensitive to the periphery diffusion and intermixing kinetics. Precise characterization of the many distinct local-environment-dependent diffusion barriers is achieved for epitaxial nanoclusters using density functional theory to assess interaction energies both with atoms at adsorption sites and at transition states. Kinetic Monte Carlo simulation incorporating these barriers then captures structure evolution on the appropriate time scale for two-dimensional core-ring and intermixed Au-Ag nanoclusters on Ag(100).

Real-Time Ab Initio KMC Simulation of the Self-Assembly and Sintering of Bimetallic Epitaxial Nanoclusters: Au + Ag on Ag(100)

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

Han, Yong; Liu, Da-Jiang; Evans, James W

2014-08-13

Far-from-equilibrium shape and structure evolution during formation and post-assembly sintering of bimetallic nanoclusters is extremely sensitive to the periphery diffusion and intermixing kinetics. Precise characterization of the many distinct local-environment-dependent diffusion barriers is achieved for epitaxial nanoclusters using density functional theory to assess interaction energies both with atoms at adsorption sites and at transition states. Kinetic Monte Carlo simulation incorporating these barriers then captures structure evolution on the appropriate time scale for two-dimensional core-ring and intermixed Au-Ag nanoclusters on Ag(100).

Carbon nanotube thin film strain sensor models assembled using nano- and micro-scale imaging

NASA Astrophysics Data System (ADS)

Lee, Bo Mi; Loh, Kenneth J.; Yang, Yuan-Sen

2017-07-01

Nanomaterial-based thin films, particularly those based on carbon nanotubes (CNT), have brought forth tremendous opportunities for designing next-generation strain sensors. However, their strain sensing properties can vary depending on fabrication method, post-processing treatment, and types of CNTs and polymers employed. The objective of this study was to derive a CNT-based thin film strain sensor model using inputs from nano-/micro-scale experimental measurements of nanotube physical properties. This study began with fabricating ultra-low-concentration CNT-polymer thin films, followed by imaging them using atomic force microscopy. Image processing was employed for characterizing CNT dispersed shapes, lengths, and other physical attributes, and results were used for building five different types of thin film percolation-based models. Numerical simulations were conducted to assess how the morphology of dispersed CNTs in its 2D matrix affected bulk film electrical and electromechanical (strain sensing) properties. The simulation results showed that CNT morphology had a significant impact on strain sensing performance.

Ultrasonic Fatigue Endurance of Thin Carbon Fiber Sheets

NASA Astrophysics Data System (ADS)

Domínguez Almaraz, Gonzalo M.; Ruiz Vilchez, Julio A.; Dominguez, Aymeric; Meyer, Yann

2016-04-01

Ultrasonic fatigue tests were carried out on thin carbon fiber sheets (0.3 mm of thickness) to determine the fatigue endurance under very high-frequency loading (20 kHz). This material, called the gas diffusion layer (GDL), plays a major role in the overall performances of proton exchange membrane fuel cells (PEMFCs). The study of its physical-chemical properties is an on-going subject in the literature; nevertheless, no knowledge is available concerning the high-frequency fatigue endurance. A principal difficulty in carrying out ultrasonic fatigue tests on this material was to determine the dimensions of testing specimen to fit the resonance condition. This aspect was solved by modal numerical simulation: The testing specimen has been a combination of a low-strength steel frame (to facilitate the attachment to the ultrasonic machine and to increase the mass of the specimen), and the carbon fiber hourglass-shape profile. Under resonance condition, a stationary elastic wave is generated along the specimen that induces high stress at the neck section and high displacements at the ends. Results show that fatigue life was close to 3 × 108 cycles when the high Von Misses stress at the neck section was 170 MPa, whereas fatigue life attains the 4.5 × 109 cycles when stress decreases to 117 MPa. Crack initiation and propagation were analyzed, and conclusions were drawn concerning the fatigue endurance of these fiber carbon sheets under ultrasonic fatigue testing.

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering

NASA Astrophysics Data System (ADS)

Okamoto, A.; Suzuki, Y.; Yoshitake, M.; Ogawa, S.; Nakano, N.

1997-01-01

We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH 3 gas ranging from 0.1 to 1.0 ppm is increasing.

In situ fluorescence activation of DNA-silver nanoclusters as a label-free and general strategy for cell nucleus imaging.

PubMed

Li, Duo; Qiao, Zhenzhen; Yu, Yanru; Tang, Jinlu; He, Xiaoxiao; Shi, Hui; Ye, Xiaosheng; Lei, Yanli; Wang, Kemin

2018-01-25

A facile, general and turn-on nucleus imaging strategy was first developed based on in situ fluorescence activation of C-rich dark silver nanoclusters by G-rich telomeres. After a simple incubation without washing, nanoclusters could selectively stain the nucleus with intense red luminescence, which was confirmed using fixed/living cells and several cell lines.

Ability of a beta-casein phosphopeptide to modulate the precipitation of calcium phosphate by forming amorphous dicalcium phosphate nanoclusters.

PubMed Central

Holt, C; Wahlgren, N M; Drakenberg, T

1996-01-01

The ability of casein in the form of colloidal-sized casein micelles to modulate the phase separation of calcium phosphate during milk secretion is adapted to produce nanometre-sized particles of calcium phosphate stabilized by a casein phosphopeptide (nanoclusters). The nanoclusters were prepared from an undersaturated solution of salts and the peptide by raising the pH homogeneously from about 5.5 to 6.7 with urea plus urease. Chemical analysis and IR spectroscopy showed that they comprise an amorphous dicalcium phosophate bound to the phosphopeptide. Multinuclear NMR spectroscopy of the cluster solutions showed that the small ions and free peptide in the solution were in a state of dynamic exchange with the nanoclusters. The peptide is linked to the calcium phosphate through its sequence of phosphorylated residues, but, in a proportion of adsorbed conformational states, the termini retain the conformational freedom of the unbound peptide. The ability of casein to form nanoclusters in milk suggests a more general mechanism for avoiding pathological calcification and regulating calcium flow in tissues and biological fluids exposed to or containing high concentrations of calcium. PMID:8615755

Nanoporous Substrate with Mixed Nanoclusters for Surface Enhanced Raman Scattering.

NASA Astrophysics Data System (ADS)

Chang, Sehoon; Ko, Hyunhyub; Singamaneni, Srikanth; Gunawidjaja, Ray; Tsukruk, Vladimir

2009-03-01

Rapid detection of plastic and liquid explosives is an urgent need due to various societal and technological reasons. We employed a novel design of surface enhanced Raman scattering (SERS)-active substrate based on porous alumina membranes decorated with mixed nanoclusters of gold nanorods and nanoparticles. We demonstrated trace level detection of several important explosives such as dinitrotolene (DNT), trinitrotoluene (TNT), and hexamethylenetriperoxidediamine (HMTD) by fast, sensitive, reliable Raman spectroscopic method. We achieved near molecular-level detection (about 15˜ 30 molecules) of DNT and TNT utilizing the SERS substrate. However, trace level detection is challenging due to the lack of common optical signatures (fluorescence, absorption in UV-vis range) or chemical functionality of peroxide-based explosives such as HMTD. To overcome this, we employed photochemical decomposition approach and analyzed chemical fragments using SERS. We suggest that tailored polymer coating, mixed nanoclusters, and laser-induced photocatalytic decomposition are all critical for achieving this unprecedented sensitivity level..

Exploring luminescence-based temperature sensing using protein-passivated gold nanoclusters

NASA Astrophysics Data System (ADS)

Chen, Xi; Essner, Jeremy B.; Baker, Gary A.

2014-07-01

We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol-gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers.We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol-gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers. Electronic supplementary information (ESI) available: Supplemental figures and experimental details. See DOI: 10.1039/c4nr02069c

3D contour fluorescence spectroscopy with Brus model: Determination of size and band gap of double stranded DNA templated silver nanoclusters

NASA Astrophysics Data System (ADS)

Kamalraj, Devaraj; Yuvaraj, Selvaraj; Yoganand, Coimbatore Paramasivam; Jaffer, Syed S.

2018-01-01

Here, we propose a new synthetic methodology for silver nanocluster preparation by using a double stranded-DNA (ds-DNA) template which no one has reported yet. A new calculative method was formulated to determine the size of the nanocluster and their band gaps by using steady state 3D contour fluorescence technique with Brus model. Generally, the structure and size of the nanoclusters determine by using High Resolution Transmission Electron Microscopy (HR-TEM). Before imaging the samples by using HR-TEM, they are introduced to drying process which causes aggregation and forms bigger polycrystalline particles. It takes long time duration and expensive methodology. In this current methodology, we found out the size and band gap of the nanocluster in the liquid form without any polycrystalline aggregation for which 3D contour fluorescence technique was used as an alternative approach to the HR-TEM method.

Low frequency ultrasound (42 kHz) assisted degradation of Acid Blue 113 in the presence of visible light driven rare earth nanoclusters loaded TiO2 nanophotocatalysts.

PubMed

Sathishkumar, Panneerselvam; Mangalaraja, Ramalinga Viswanathan; Rozas, Oscar; Mansilla, Héctor D; Gracia-Pinilla, M A; Anandan, Sambandam

2014-09-01

An attempt has been made to render the visible light driven photocatalytic activity to the TiO2 nanocatalysts by loading 1 wt% of rare earth (RE) nanoclusters (Gd(3+), Nd(3+) and Y(3+)) using a low frequency (42 kHz) producing commercial sonicator. The STEM-HAADF analysis confirms that the RE nanoclusters were residing at the surface of the TiO2. Transmission electron microscopic (TEM) and X-ray diffraction (XRD) analyses confirm that the loading of RE nanoclusters cannot make any significant changes in the crystal structure of TiO2. However, the optical properties of the resulted nanocatalysts were significantly modified and the nanocatalysts were employed to study the sonocatalytic, photocatalytic and sonophotocatalytic decolorization as well as mineralization of Acid Blue 113 (AB113). Among the experimented nanocatalysts maximum degradation of AB113 was achieved in the presence Y(3+)-TiO2 nanocatalysts. The decolorization of AB113 in the presence and absence of Y(3+) loaded TiO2 ensues the following order sonolysiscarbon (TOC) can be removed from AB113 after the 5h of continuous irradiation however the mineralization cannot be able to show the synergetic effect. Copyright © 2014 Elsevier B.V. All rights reserved.

Boron oxynitride nanoclusters on tungsten trioxide as a metal-free cocatalyst for photocatalytic oxygen evolution from water splitting

NASA Astrophysics Data System (ADS)

Xie, Ying Peng; Liu, Gang; Lu, Gao Qing (Max); Cheng, Hui-Ming

2012-02-01

Here we show that B2O3-xNx nanoclusters can be formed on the surface of WO3 particles by a combination of thermal oxidation of tungsten boride (WB) in air and the subsequent nitriding process in gaseous ammonia. The resultant nanoclusters are found to play an apparent role in improving the photocatalytic oxygen evolution of WO3 by promoting the surface separation of photoexcited charge-carriers.Here we show that B2O3-xNx nanoclusters can be formed on the surface of WO3 particles by a combination of thermal oxidation of tungsten boride (WB) in air and the subsequent nitriding process in gaseous ammonia. The resultant nanoclusters are found to play an apparent role in improving the photocatalytic oxygen evolution of WO3 by promoting the surface separation of photoexcited charge-carriers. Electronic supplementary information (ESI) available: (1) Experimental section. (2) XRD patterns, FT-IR and Raman spectra of B2O3@WO3 and B2O3-xNx@WO3. (3) Time course of O2 evolution from water splitting using B2O3@WO3 and B2O3-xNx@WO3. (4) XRD pattern and SEM image of pure WO3, UV-visible absorption spectra of pure WO3 and N-WO3. (5) UV-visible absorption spectra of bulk B2O3 and schematic of band edges of WO3, bulk B2O3, and B2O3-xNx nanocluster. See DOI: 10.1039/c2nr11846g

Various Silver Nanostructures on Sapphire Using Plasmon Self-Assembly and Dewetting of Thin Films

NASA Astrophysics Data System (ADS)

Kunwar, Sundar; Sui, Mao; Zhang, Quanzhen; Pandey, Puran; Li, Ming-Yu; Lee, Jihoon

2017-04-01

Silver (Ag) nanostructures demonstrate outstanding optical, electrical, magnetic, and catalytic properties and are utilized in photonic, energy, sensors, and biomedical devices. The target application and the performance can be inherently tuned by control of configuration, shape, and size of Ag nanostructures. In this work, we demonstrate the systematical fabrication of various configurations of Ag nanostructures on sapphire (0001) by controlling the Ag deposition thickness at different annealing environments in a plasma ion coater. In particular, the evolution of Ag particles (between 2 and 20 nm), irregular nanoclusters (between 30 and 60 nm), and nanocluster networks (between 80 and 200 nm) are found be depended on the thickness of Ag thin film. The results were systematically analyzed and explained based on the solid-state dewetting, surface diffusion, Volmer-Weber growth model, coalescence, and surface energy minimization mechanism. The growth behavior of Ag nanostructures is remarkably differentiated at higher annealing temperature (750 °C) due to the sublimation and temperature-dependent characteristic of dewetting process. In addition, Raman and reflectance spectra analyses reveal that optical properties of Ag nanostructures depend on their morphology.

First-principles study of MoS2 and MoSe2 nanoclusters in the framework of evolutionary algorithm and density functional theory

NASA Astrophysics Data System (ADS)

Hashemi, Zohreh; Rafiezadeh, Shohreh; Hafizi, Roohollah; Hashemifar, S. Javad; Akbarzadeh, Hadi

2018-04-01

Evolutionary algorithm is combined with full-potential ab initio calculations to investigate conformational space of (MoS2)n and (MoSe2)n (n = 1-10) nanoclusters and to identify the lowest energy structural isomers of these systems. It is argued that within both BLYP and PBE functionals, these nanoclusters favor sandwiched planar configurations, similar to their ideal planar sheets. The second order difference in total energy (Δ2 E) of the lowest energy isomers is computed to estimate the abundance of the clusters at different sizes and to determine the magic sizes of (MoS2)n and (MoSe2)n nanoclusters. In order to investigate the electronic properties of nanoclusters, their energy gap is calculated by several methods, including hybrid functionals (B3LYP and PBE0), GW approach, and Δ scf method. At the end, the vibrational modes of the lowest lying isomers are calculated by using the force constants method and the IR active modes of the systems are identified. The vibrational spectra are used to calculate the Helmholtz free energy of the systems and then to investigate abundance of the nanoclusters at finite temperatures.

Electronic structure and orientation relationship of Li nanoclusters embedded in MgO studied by depth-selective positron annihilation two-dimensional angular correlation

NASA Astrophysics Data System (ADS)

Falub, C. V.; Mijnarends, P. E.; Eijt, S. W.; van Huis, M. A.; van Veen, A.; Schut, H.

2002-08-01

Quantum-confined positrons are sensitive probes for determining the electronic structure of nanoclusters embedded in materials. In this work, a depth-selective positron annihilation 2D-ACAR (two-dimensional angular correlation of annihilation radiation) method is used to determine the electronic structure of Li nanoclusters formed by implantation of 1016-cm-2 30-keV 6Li ions in MgO (100) and (110) crystals and by subsequent annealing at 950 K. Owing to the difference between the positron affinities of lithium and MgO, the Li nanoclusters act as quantum dots for positrons. 2D-ACAR distributions for different projections reveal a semicoherent fitting of the embedded metallic Li nanoclusters to the host MgO lattice. Ab initio Korringa-Kohn-Rostoker calculations of the momentum density show that the anisotropies of the experimental distributions are consistent with an fcc crystal structure of the Li nanoclusters. The observed reduction of the width of the experimental 2D-ACAR distribution is attributed to positron trapping in vacancies associated with Li clusters. This work proposes a method for studying the electronic structure of metallic quantum dots embedded in an insulating material.

Influence of inert gases on the reactive high power pulsed magnetron sputtering process of carbon-nitride thin films

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

Schmidt, Susann; Czigany, Zsolt; Greczynski, Grzegorz

2013-01-15

The influence of inert gases (Ne, Ar, Kr) on the sputter process of carbon and carbon-nitride (CN{sub x}) thin films was studied using reactive high power pulsed magnetron sputtering (HiPIMS). Thin solid films were synthesized in an industrial deposition chamber from a graphite target. The peak target current during HiPIMS processing was found to decrease with increasing inert gas mass. Time averaged and time resolved ion mass spectroscopy showed that the addition of nitrogen, as reactive gas, resulted in less energetic ion species for processes employing Ne, whereas the opposite was noticed when Ar or Kr were employed as inertmore » gas. Processes in nonreactive ambient showed generally lower total ion fluxes for the three different inert gases. As soon as N{sub 2} was introduced into the process, the deposition rates for Ne and Ar-containing processes increased significantly. The reactive Kr-process, in contrast, showed slightly lower deposition rates than the nonreactive. The resulting thin films were characterized regarding their bonding and microstructure by x-ray photoelectron spectroscopy and transmission electron microscopy. Reactively deposited CN{sub x} thin films in Ar and Kr ambient exhibited an ordering toward a fullerene-like structure, whereas carbon and CN{sub x} films deposited in Ne atmosphere were found to be amorphous. This is attributed to an elevated amount of highly energetic particles observed during ion mass spectrometry and indicated by high peak target currents in Ne-containing processes. These results are discussed with respect to the current understanding of the structural evolution of a-C and CN{sub x} thin films.« less

Superlattice Multinanolayered Thin Films of SiO2/SiO2 + Ge for Thermoelectric Device Applications

DTIC Science & Technology

2013-04-05

radioiso- tope sources in the past. In a space nuclear reactor system, the energy source is the heat generated by the controlled fission of uranium ...to the nanodots and/or nanocluster formations in the multilayered thin films. This is one of the expected results of the ion beam bombardments on...very large (150 W m 1 K 1 for Si and 63 W m 1 K 1 for Ge). The lattice thermal conductivity can be substantially reduced by alloy formation between

Two-Dimensional Ordering of Solute Nanoclusters at a Close-Packed Stacking Fault: Modeling and Experimental Analysis

PubMed Central

Kimizuka, Hajime; Kurokawa, Shu; Yamaguchi, Akihiro; Sakai, Akira; Ogata, Shigenobu

2014-01-01

Predicting the equilibrium ordered structures at internal interfaces, especially in the case of nanometer-scale chemical heterogeneities, is an ongoing challenge in materials science. In this study, we established an ab-initio coarse-grained modeling technique for describing the phase-like behavior of a close-packed stacking-fault-type interface containing solute nanoclusters, which undergo a two-dimensional disorder-order transition, depending on the temperature and composition. Notably, this approach can predict the two-dimensional medium-range ordering in the nanocluster arrays realized in Mg-based alloys, in a manner consistent with scanning tunneling microscopy-based measurements. We predicted that the repulsively interacting solute-cluster system undergoes a continuous evolution into a highly ordered densely packed morphology while maintaining a high degree of six-fold orientational order, which is attributable mainly to an entropic effect. The uncovered interaction-dependent ordering properties may be useful for the design of nanostructured materials utilizing the self-organization of two-dimensional nanocluster arrays in the close-packed interfaces. PMID:25471232

Reduction-resistant and reduction-catalytic double-crown nickel nanoclusters

NASA Astrophysics Data System (ADS)

Zhu, Min; Zhou, Zhou, Shiming; Yao, Chuanhao; Liao, Lingwen; Wu, Zhikun

2014-11-01

In this work, an attempt to synthesize zero-valent Ni nanoclusters using the Brust method resulted in an unexpected material, Ni6(SCH2CH2Ph)12, which is a nanoscale Ni(ii)-phenylethanethiolate complex and a hexameric, double-crown-like structure, as determined by a series of characterizations, including mass spectrometry (MS), thermal gravimetric analysis (TGA), single-crystal X-ray diffraction (XRD), and X-ray photoelectron spectrometry (XPS). An interesting finding is that this complex is resistant to aqueous BH4-. Investigations into other metal-phenylethanethiolate and Ni-thiolate complexes reveal that this property is not universal and appears only in complexes with a double-crown-like structure, indicating the correlation between this interesting property and the complexes' special structure. Another interesting finding is that the reduction-resistant Ni6(SCH2CH2Ph)12 exhibits remarkably higher catalytic activity than a well-known catalyst, Au25(SCH2CH2Ph)18, toward the reduction of 4-nitrophenol at low temperature (e.g., 0 °C). This work will help stimulate more research on the properties and applications of less noble metal nanoclusters.In this work, an attempt to synthesize zero-valent Ni nanoclusters using the Brust method resulted in an unexpected material, Ni6(SCH2CH2Ph)12, which is a nanoscale Ni(ii)-phenylethanethiolate complex and a hexameric, double-crown-like structure, as determined by a series of characterizations, including mass spectrometry (MS), thermal gravimetric analysis (TGA), single-crystal X-ray diffraction (XRD), and X-ray photoelectron spectrometry (XPS). An interesting finding is that this complex is resistant to aqueous BH4-. Investigations into other metal-phenylethanethiolate and Ni-thiolate complexes reveal that this property is not universal and appears only in complexes with a double-crown-like structure, indicating the correlation between this interesting property and the complexes' special structure. Another interesting

Characterizing the Conductivity and Enhancing the Piezoresistivity of Carbon Nanotube-Polymeric Thin Films

PubMed Central

Zhao, Yingjun; Schagerl, Martin; Viechtbauer, Christoph

2017-01-01

The concept of lightweight design is widely employed for designing and constructing aerospace structures that can sustain extreme loads while also being fuel-efficient. Popular lightweight materials such as aluminum alloy and fiber-reinforced polymers (FRPs) possess outstanding mechanical properties, but their structural integrity requires constant assessment to ensure structural safety. Next-generation structural health monitoring systems for aerospace structures should be lightweight and integrated with the structure itself. In this study, a multi-walled carbon nanotube (MWCNT)-based polymer paint was developed to detect distributed damage in lightweight structures. The thin film’s electromechanical properties were characterized via cyclic loading tests. Moreover, the thin film’s bulk conductivity was characterized by finite element modeling. PMID:28773084

Quasi-Dual-Packed-Kerneled Au49 (2,4-DMBT)27 Nanoclusters and the Influence of Kernel Packing on the Electrochemical Gap.

PubMed

Liao, Lingwen; Zhuang, Shengli; Wang, Pu; Xu, Yanan; Yan, Nan; Dong, Hongwei; Wang, Chengming; Zhao, Yan; Xia, Nan; Li, Jin; Deng, Haiteng; Pei, Yong; Tian, Shi-Kai; Wu, Zhikun

2017-10-02

Although face-centered cubic (fcc), body-centered cubic (bcc), hexagonal close-packed (hcp), and other structured gold nanoclusters have been reported, it was unclear whether gold nanoclusters with mix-packed (fcc and non-fcc) kernels exist, and the correlation between kernel packing and the properties of gold nanoclusters is unknown. A Au 49 (2,4-DMBT) 27 nanocluster with a shell electron count of 22 has now been been synthesized and structurally resolved by single-crystal X-ray crystallography, which revealed that Au 49 (2,4-DMBT) 27 contains a unique Au 34 kernel consisting of one quasi-fcc-structured Au 21 and one non-fcc-structured Au 13 unit (where 2,4-DMBTH=2,4-dimethylbenzenethiol). Further experiments revealed that the kernel packing greatly influences the electrochemical gap (EG) and the fcc structure has a larger EG than the investigated non-fcc structure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

DOEpatents

Rogers, John A; Cao, Qing; Alam, Muhammad; Pimparkar, Ninad

2015-02-03

The present invention provides device components geometries and fabrication strategies for enhancing the electronic performance of electronic devices based on thin films of randomly oriented or partially aligned semiconducting nanotubes. In certain aspects, devices and methods of the present invention incorporate a patterned layer of randomly oriented or partially aligned carbon nanotubes, such as one or more interconnected SWNT networks, providing a semiconductor channel exhibiting improved electronic properties relative to conventional nanotubes-based electronic systems.

Recyclable magnetic nanocluster crosslinked with poly(ethylene oxide)-block-poly(2-vinyl-4,4-dimethylazlactone) copolymer for adsorption with antibody.

PubMed

Prai-In, Yingrak; Boonthip, Chatchai; Rutnakornpituk, Boonjira; Wichai, Uthai; Montembault, Véronique; Pascual, Sagrario; Fontaine, Laurent; Rutnakornpituk, Metha

2016-10-01

Surface modification of magnetic nanoparticle (MNP) with poly(ethylene oxide)-block-poly(2-vinyl-4,4-dimethylazlactone) (PEO-b-PVDM) diblock copolymers and its application as recyclable magnetic nano-support for adsorption with antibody were reported herein. PEO-b-PVDM copolymers were first synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization using poly(ethylene oxide) chain-transfer agent as a macromolecular chain transfer agent to mediate the RAFT polymerization of VDM. They were then grafted on amino-functionalized MNP by coupling with some azlactone rings of the PVDM block to form magnetic nanoclusters with tunable cluster size. The nanocluster size could be tuned by adjusting the chain length of the PVDM block. The nanoclusters were successfully used as efficient and recyclable nano-supports for adsorption with anti-rabbit IgG antibody. They retained higher than 95% adsorption of the antibody during eight adsorption-separation-desorption cycles, indicating the potential feasibility in using this novel hybrid nanocluster as recyclable support in cell separation applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Carbon tolerance of Ni-Cu and Ni-Cu/YSZ sub-μm sized SOFC thin film model systems

NASA Astrophysics Data System (ADS)

Götsch, Thomas; Schachinger, Thomas; Stöger-Pollach, Michael; Kaindl, Reinhard; Penner, Simon

2017-04-01

Thin films of YSZ, unsupported Ni-Cu 1:1 alloy phases and YSZ-supported Ni-Cu 1:1 alloy solutions have been reproducibly prepared by magnetron sputter deposition on Si wafers and NaCl(001) single crystal facets at two selected substrate temperatures of 298 K and 873 K. Subsequently, the layer properties of the resulting sub-μm thick thin films as well as the tendency towards carbon deposition following treatment in pure methane at 1073 K has been tested comparatively. Well-crystallized structures of cubic YSZ, cubic NiCu and cubic NiCu/YSZ have been obtained following deposition at 873 K on both substrates. Carbon is deposited on all samples following the trend Ni-Cu (1:1) = Ni-Cu (1:1)/YSZ > pure YSZ, indicating that at least the 1:1 composition of layered Ni-Cu alloy phases is not able to suppress the carbon deposition completely, rendering it unfavorable for usage as anode component in sub-μm sized fuel cells. It is shown that surfaces with a high Cu/Ni ratio nevertheless prohibit any carbon deposition.

Biomimetic one-pot synthesis of gold nanoclusters/nanoparticles for targeted tumor cellular dual-modality imaging

NASA Astrophysics Data System (ADS)

Lin, Jing; Zhou, Zhijun; Li, Zhiming; Zhang, Chunlei; Wang, Xiansong; Wang, Kan; Gao, Guo; Huang, Peng; Cui, Daxiang

2013-04-01

Biomimetic synthesis has become a promising green pathway to prepare nanomaterials. In this study, bovine serum albumin (BSA)-conjugated gold nanoclusters/nanoparticles were successfully synthesized in water at room temperature by a protein-directed, solution-phase, green synthetic method. The synthesized BSA-Au nanocomplexes have fluorescence emission (588 nm) of gold nanoclusters and surface plasmon resonance of gold nanoparticles. The BSA-Au nanocomplexes display non-cytotoxicity and excellent biocompatibility on MGC803 gastric cancer cells. After conjugation of folic acid molecules, the obtained BSA-Au nanocomplexes showed highly selective targeting for MGC803 cells and dual-modality dark-field and fluorescence imaging.

A cuboctahedral platinum (Pt79) nanocluster enclosed by well defined facets favours di-sigma adsorption and improves the reaction kinetics for methanol fuel cells.

PubMed

Mahata, Arup; Choudhuri, Indrani; Pathak, Biswarup

2015-08-28

The methanol dehydrogenation steps are studied very systematically on the (111) facet of a cuboctahedral platinum (Pt79) nanocluster enclosed by well-defined facets. The various intermediates formed during the methanol decompositions are adsorbed at the edge and bridge site of the facet either vertically (through C- and O-centres) or in parallel. The di-sigma adsorption (in parallel) on the (111) facet of the nanocluster is the most stable structure for most of the intermediates and such binding improves the interaction between the substrate and the nanocluster and thus the catalytic activity. The reaction thermodynamics, activation barrier, and temperature dependent reaction rates are calculated for all the successive methanol dehydrogenation steps to understand the methanol decomposition mechanism, and these values are compared with previous studies to understand the catalytic activity of the nanocluster. We find the catalytic activity of the nanocluster is excellent while comparing with any previous reports and the methanol dehydrogenation thermodynamics and kinetics are best when the intermediates are adsorbed in a di-sigma manner.

Relativistic DFT investigation of electronic structure effects arising from doping the Au25 nanocluster with transition metals.

PubMed

Alkan, Fahri; Muñoz-Castro, Alvaro; Aikens, Christine M

2017-10-26

We perform a theoretical investigation using density functional theory (DFT) and time-dependent DFT (TDDFT) on the doping of the Au 25 (SR) 18 -1 nanocluster with group IX transition metals (M = cobalt, rhodium and iridium). Different doping motifs, charge states and spin multiplicities were considered for the single-atom doped nanoclusters. Our results show that the interaction (or the lack of interaction) between the d-type energy levels that mainly originate from the dopant atom and the super-atomic levels plays an important role in the energetics, the electronic structure and the optical properties of the doped systems. The evaluated MAu 24 (SR) 18 q (q = -1, -3) systems favor an endohedral disposition of the doping atom typically in a singlet ground state, with either a 6- or 8-valence electron icosahedral core. For the sake of comparison, the role of the d energy levels in the electronic structure of a variety of doped Au 25 (SR) 18 -1 nanoclusters was investigated for dopant atoms from other families such as Cd, Ag and Pd. Finally, the effect of spin-orbit coupling (SOC) on the electronic structure and absorption spectra was determined. The information in this study regarding the relative energetics of the d-based and super-atom energy levels can be useful to extend our understanding of the preferred doping modes of different transition metals in protected gold nanoclusters.

Fluorescent Pressure Response of Protein-Nanocluster Polymer Composites

DTIC Science & Technology

2016-05-01

composites as pressure sensitive indicators of brain damage. The PNC composites are made up of protein coated gold nanoclusters and a styrene- ethylene ...styrene- ethylene /butylene-styrene (SEBS):mineral oil composites that were developed as a brain tissue surrogate at ARL. Finally, we would like to...allowing us to use solid samples and create a model for brain damage. To this end, we used styrene- ethylene /butylene-styrene (SEBS) as the matrix to

Network-Forming Nanoclusters in Binary As-S/Se Glasses: From Ab Initio Quantum Chemical Modeling to Experimental Evidences.

PubMed

Hyla, M

2017-12-01

Network-forming As 2 (S/Se) m nanoclusters are employed to recognize expected variations in a vicinity of some remarkable compositions in binary As-Se/S glassy systems accepted as signatures of optimally constrained intermediate topological phases in earlier temperature-modulated differential scanning calorimetry experiments. The ab initio quantum chemical calculations performed using the cation-interlinking network cluster approach show similar oscillating character in tendency to local chemical decomposition but obvious step-like behavior in preference to global phase separation on boundary chemical compounds (pure chalcogen and stoichiometric arsenic chalcogenides). The onsets of stability are defined for chalcogen-rich glasses, these being connected with As 2 Se 5 (Z = 2.29) and As 2 S 6 (Z = 2.25) nanoclusters for As-Se and As-S glasses, respectively. The physical aging effects result preferentially from global phase separation in As-S glass system due to high localization of covalent bonding and local demixing on neighboring As 2 Se m+1 and As 2 Se m-1 nanoclusters in As-Se system. These nanoclusters well explain the lower limits of reversibility windows in temperature-modulated differential scanning calorimetry, but they cannot be accepted as signatures of topological phase transitions in respect to the rigidity theory.

Redox-Triggered Bonding-Induced Emission of Thiol-Functionalized Gold Nanoclusters for Luminescence Turn-On Detection of Molecular Oxygen.

PubMed

Ao, Hang; Feng, Hui; Zhao, Mengting; Zhao, Meizhi; Chen, Jianrong; Qian, Zhaosheng

2017-11-22

Most optical sensors for molecular oxygen were developed based on the quenching effect of the luminescence of oxygen-sensitive probes; however, the signal turn-off mode of these probes is undesirable to quantify and visualize molecular oxygen. Herein, we report a novel luminescence turn-on detection strategy for molecular oxygen via the specific oxygen-triggered bonding-induced emission of thiol-functionalized gold nanoclusters. Thiol-functionalized gold nanoclusters were prepared by a facile one-step synthesis, and as-prepared gold nanoclusters possess significant aggregation-induced emission (AIE) property. It is the first time to discover the oxygen-triggered bonding-induced emission (BIE) behavior of gold nanoclusters, which results in disulfide-linked covalent bonding assemblies with intensely red luminescence. This specific redox-triggered BIE is capable of quantitatively detecting dissolved oxygen in aqueous solution in a light-up manner, and trace amount of dissolved oxygen at ppb level is achieved based on this detection method. A facile and convenient test strip for oxygen detection was also developed to monitor molecular oxygen in a gas matrix. Covalent bonding-induced emission is proven to be a more efficient way to attain high brightness of AIEgens than a physical aggregation-induced emission process, and provides a more convenient and desirable detection method for molecular oxygen than the previous sensors.

A display module implemented by the fast high-temperatue response of carbon nanotube thin yarns.

PubMed

Wei, Yang; Liu, Peng; Jiang, Kaili; Fan, Shoushan

2012-05-09

Suspending superaligned multiwalled carbon nanotube (MWCNT) films were processed into CNT thin yarns, about 1 μm in diameter, by laser cutting and an ethanol atomization bath treatment. The fast high-temperature response under a vacuum was revealed by monitoring the incandescent light with a photo diode. The thin yarns can be electrically heated up to 2170 K in 0.79 mS, and the succeeding cool-down time is 0.36 mS. The fast response is attributed to the ultrasmall mass of the independent single yarn, large radiation coefficient, and improved thermal conductance through the two cool ends. The millisecond response time makes it possible to use the visible hot thin yarns as light-emitting elements of an incandescent display. A fully sealed display with 16 × 16 matrix was successfully fabricated using screen-printed thick electrodes and CNT thin yarns. It can display rolling characters with a low power consumption. More applications can be further developed based on the addressable CNT thermal arrays.

Supported Pd nanoclusters with enhanced hydrogen spillover for NOx removal via H2-SCR: the elimination of "volcano-type" behaviour.

PubMed

Peng, Zhezhe; Li, Zongyuan; Liu, Yun-Quan; Yan, Shuai; Tong, Jianing; Wang, Duo; Ye, Yueyuan; Li, Shuirong

2017-05-30

A rational design of a Pd catalyst with highly dispersed Pd nanoclusters on an Al doped ceria-based oxide for low temperature selective catalytic reduction of NO x by hydrogen with excess O 2 was achieved. The supported Pd nanocluster shows a high hydrogen spillover ability and a NO x conversion of >84% within 100-300 °C.

The impact of electron correlations on the energetics and stability of silicon nanoclusters

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

Matsko, N. L.; Baturin, V. S.; Lepeshkin, S. V.

2016-08-21

The first-principles prediction of stable nanocluster structure is often hampered by the existence of many isomer configurations with energies close to the ground state. This fact attaches additional importance to many-electron effects beyond density functional theory (DFT), because their contributions can change a subtle energy order of competitive structures. To analyze this problem, we consider, as an example, the energetics of silicon nanoclusters passivated by hydrogen Si{sub 10}H{sub 2n} (0 ≤ n ≤ 11), where passivation changes the structure from compact to loosely packed and branched. Our calculations performed with DFT, hybrid functionals, and Hartree-Fock methods, as well as bymore » the GW approximation, confirm a considerable sensitivity of isomer energy ordering to many-electron effects.« less

A highly-active and poison-tolerant Pt12 sub-nanocluster catalyst for the reductive amination of aldehydes with amines.

PubMed

Takahashi, Masaki; Imaoka, Takane; Hongo, Yushi; Yamamoto, Kimihisa

2013-12-07

A one-atom controlled platinum sub-nanocluster (under 1 nm) was synthesized using a phenylazomethine dendrimer template. This sub-nanocluster (SNC) catalyst exhibits a remarkable catalytic activity during reductive amination compared to the standard platinum nanoparticles of 2.2 ± 0.8 nm under mild conditions and a low catalyst loading. In addition, this catalyst has a remarkable poison-tolerance to amines without adding protic acid.

Carbon nanotubes/fluorinated polymers nanocomposite thin films for electrical contacts lubrication

NASA Astrophysics Data System (ADS)

Benedetto, A.; Viel, P.; Noël, S.; Izard, N.; Chenevier, P.; Palacin, S.

2007-09-01

The need to operate in extreme environmental conditions (ultra high vacuum, high temperatures, aerospatial environment, …) and the miniaturization toward micro electromechanical systems is demanding new materials in the field of low-level electrical contacts lubrication. Dry and chemically immobilized lubrication is expected to be an alternative to the traditional wet lubricants oils. With the goal to conciliate electrical conductivity and lubricant properties we designed nanocomposite thin films composed of a 2D carbon nanotubes network embedded in an organic matrix. The nanotubes networks were deposited on gold surfaces modified by electrochemical cathodic grafting of poly(acrylonitrile). The same substrate served for covalently bonding the low-friction organic matrix. Three different matrixes were tested: a perfluorinated oligomer chemically grafted and two different polyfluorinated acrylates electrochemically grafted. The nanocomposite thin films have been characterized by ATR FT-IR, XPS and Raman spectroscopy. We measured the effects of the different matrixes and the nanotubes addition on the tribological properties and on the contact resistances of the films.

The actin cytoskeleton modulates the activation of iNKT cells by segregating CD1d nanoclusters on antigen-presenting cells

PubMed Central

Torreno-Pina, Juan A.; Manzo, Carlo; Salio, Mariolina; Aichinger, Michael C.; Oddone, Anna; Lakadamyali, Melike; Shepherd, Dawn; Besra, Gurdyal S.; Cerundolo, Vincenzo

2016-01-01

Invariant natural killer T (iNKT) cells recognize endogenous and exogenous lipid antigens presented in the context of CD1d molecules. The ability of iNKT cells to recognize endogenous antigens represents a distinct immune recognition strategy, which underscores the constitutive memory phenotype of iNKT cells and their activation during inflammatory conditions. However, the mechanisms regulating such “tonic” activation of iNKT cells remain unclear. Here, we show that the spatiotemporal distribution of CD1d molecules on the surface of antigen-presenting cells (APCs) modulates activation of iNKT cells. By using superresolution microscopy, we show that CD1d molecules form nanoclusters at the cell surface of APCs, and their size and density are constrained by the actin cytoskeleton. Dual-color single-particle tracking revealed that diffusing CD1d nanoclusters are actively arrested by the actin cytoskeleton, preventing their further coalescence. Formation of larger nanoclusters occurs in the absence of interactions between CD1d cytosolic tail and the actin cytoskeleton and correlates with enhanced iNKT cell activation. Importantly and consistently with iNKT cell activation during inflammatory conditions, exposure of APCs to the Toll-like receptor 7/8 agonist R848 increases nanocluster density and iNKT cell activation. Overall, these results define a previously unidentified mechanism that modulates iNKT cell autoreactivity based on the tight control by the APC cytoskeleton of the sizes and densities of endogenous antigen-loaded CD1d nanoclusters. PMID:26798067

Pre-Incubation of Auric Acid with DNA Is Unnecessary for the Formation of DNA-Templated Gold Nanoclusters.

PubMed

Chen, Yang; Tao, Guangyu; Lin, Ruoyun; Pei, Xiaojing; Liu, Feng; Li, Na

2016-06-06

The rationale for the preparation of DNA-templated gold nanoclusters (DNA-Au NCs) has not been well understood, thereby slowing down the advancement of the synthesis and applications of DNA-Au NCs. The interaction between metal ions and the DNA template seems to be the key factor for the successful preparation of DNA-templated metal nanoclusters. With the help of circular dichroism in this contribution, we put efforts into interrogating the necessity of pre-incubation of HAuCl4 with poly-adenine template in the formation of Au NCs by citrate reduction. Our results revealed that the pre-incubation of HAuCl4 with poly-adenine is not favorable for the formation of Au NCs, which is distinctly different from the formation process for silver nanoclusters. It is our hope that this study can provide guidance in the preparation of Au NCs with more DNA templates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of oxidation on the plasmonic properties of aluminum nanoclusters.

PubMed

Douglas-Gallardo, Oscar A; Soldano, Germán J; Mariscal, Marcelo M; Sánchez, Cristián Gabriel

2017-11-16

The scouting of alternative plasmonic materials able to enhance and extend the optical properties of noble metal nanostructures is on the rise. Aluminum is endowed with a set of interesting properties which turn it into an attractive plasmonic material. Here we present the optical and electronic features of different aluminum nanostructures stemming from a multilevel computational study. Molecular Dynamics (MD) simulations using a reactive force field (ReaxFF), carefully validated with Density Functional Theory (DFT), were employed to mimic the oxidation of icosahedral aluminum nanoclusters. Resulting structures with different oxidation degrees were then studied through the Time-Dependent Density Functional Tight Binding (TD-DFTB) method. A similar approach was used in aluminum nanoclusters with a disordered structure to study how the loss of crystallinity affects the optical properties. To the best of our knowledge, this is the first report that addresses this issue from the fully atomistic time-dependent approach by means of two different and powerful simulation tools able to describe quantum and physicochemical properties associated with nanostructured particles.

Observation of gold sub-nanocluster nucleation within a crystalline protein cage

NASA Astrophysics Data System (ADS)

Maity, Basudev; Abe, Satoshi; Ueno, Takafumi

2017-03-01

Protein scaffolds provide unique metal coordination environments that promote biomineralization processes. It is expected that protein scaffolds can be developed to prepare inorganic nanomaterials with important biomedical and material applications. Despite many promising applications, it remains challenging to elucidate the detailed mechanisms of formation of metal nanoparticles in protein environments. In the present work, we describe a crystalline protein cage constructed by crosslinking treatment of a single crystal of apo-ferritin for structural characterization of the formation of sub-nanocluster with reduction reaction. The crystal structure analysis shows the gradual movement of the Au ions towards the centre of the three-fold symmetric channels of the protein cage to form a sub-nanocluster with accompanying significant conformational changes of the amino-acid residues bound to Au ions during the process. These results contribute to our understanding of metal core formation as well as interactions of the metal core with the protein environment.

Lithographically patterned thin activated carbon films as a new technology platform for on-chip devices.

PubMed

Wei, Lu; Nitta, Naoki; Yushin, Gleb

2013-08-27

Continuous, smooth, visibly defect-free, lithographically patterned activated carbon films (ACFs) are prepared on the surface of silicon wafers. Depending on the synthesis conditions, porous ACFs can either remain attached to the initial substrate or be separated and transferred to another dense or porous substrate of interest. Tuning the activation conditions allows one to change the surface area and porosity of the produced carbon films. Here we utilize the developed thin ACF technology to produce prototypes of functional electrical double-layer capacitor devices. The synthesized thin carbon film electrodes demonstrated very high capacitance in excess of 510 F g(-1) (>390 F cm(-3)) at a slow cyclic voltammetry scan rate of 1 mV s(-1) and in excess of 325 F g(-1) (>250 F cm(-3)) in charge-discharge tests at an ultrahigh current density of 45,000 mA g(-1). Good stability was demonstrated after 10,000 galvanostatic charge-discharge cycles. The high values of the specific and volumetric capacitances of the selected ACF electrodes as well as the capacity retention at high current densities demonstrated great potential of the proposed technology for the fabrication of various on-chip devices, such as micro-electrochemical capacitors.

Geometrical flexibility of platinum nanoclusters: impacts on catalytic decomposition of ethylene glycol.

PubMed

Mahmoodinia, Mehdi; Trinh, Thuat T; Åstrand, Per-Olof; Tran, Khanh-Quang

2017-11-01

Catalytic decomposition of ethylene glycol on the Pt 13 cluster was studied as a model system for hydrogen production from a lignocellulosic material. Ethylene glycol was chosen as a starting material because of two reasons, it is the smallest oxygenate with a 1 : 1 carbon to oxygen ratio and it contains the C-H, O-H, C-C, and C-O bonds also present in biomass. Density functional theory calculations were employed for predictions of reaction pathways for C-H, O-H, C-C and C-O cleavages, and Brønsted-Evans-Polanyi relationships were established between the final state and the transition state for all mechanisms. The results show that Pt 13 catalyzes the cleavage reactions of ethylene glycol more favourably than a Pt surface. The flexibility of Pt 13 clusters during the reactions is the key factor in reducing the activation barrier. Overall, the results demonstrate that ethylene glycol and thus biomass can be efficiently converted into hydrogen using platinum nanoclusters as catalysts.

Morphological Evolution of Nanocluster Aggregates and Single Crystals in Alkaline Zinc Electrodeposition

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

Desai, D; Turney, DE; Anantharaman, B

2014-04-24

The morphology of Zn electrodeposits is studied on carbon-coated transmission electron microscopy grids. At low over-potentials (eta = -50 mV), the morphology develops by aggregation at two distinct length scales: similar to 5 nm diameter monocrystalline nanoclusters form similar to 50 nm diameter polycrystalline aggregates, and the aggregates form a branched network. Epitaxial (00 (0) over bar2) growth above an overpotential of vertical bar eta(c)vertical bar > 125 mV leads to the formation of hexagonal single crystals up to 2 mu m in diameter. Potentiostatic current transients were used to calculate the nucleation rate from Scharifker et al.'s model. Themore » exp(eta) dependence of the nucleation rates indicates that atomistic nucleation theory explains the nucleation process better than Volmer-Weber theory. A kinetic model is provided using the rate equations of vapor solidification to simulate the evolution of the different morphologies. On solving these equations, we show that aggregation is attributed to cluster impingement and cluster diffusion while single-crystal formation is attributed to direct attachment.« less

Control of electron-lattice interaction in organic nanoclusters

NASA Astrophysics Data System (ADS)

Malyukin, Yu. V.; Gnap, B. A.; Sorokin, A. V.; Yefimova, S. L.

2012-10-01

In this study we demonstrate that the electron-lattice interaction (ELI) could be controlled by changing exciton delocalization length in ordered organic nanoclusters called J-aggregates. Particularly it could be done via the J-aggregates solvate shell manipulation using surfactants. The strong correlation between the J-aggregates luminescence quantum yield and the ELI strength has been reviled that allows us to consider the exciton self-trapping as the main mechanism of the J-aggregates luminescence losses.

A molecule-like PtAu24(SC6H13)18 nanocluster as an electrocatalyst for hydrogen production

PubMed Central

Kwak, Kyuju; Choi, Woojun; Tang, Qing; Kim, Minseok; Lee, Yongjin; Jiang, De-en; Lee, Dongil

2017-01-01

The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster. The catalytic activity of the resulting bimetallic nanocluster, PtAu24(SC6H13)18, for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The molecule-like bimetallic nanocluster represents a class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts. PMID:28281526

RBS, TEM and SEM Characterization of Gold Nanoclusters in TiO2(110)

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

Shutthanandan, V; Zhang, Yanwen; Wang, Chong M.

2004-05-01

Nucleation of gold nanoclusters in TiO2(110) single crystal using ion implantation and subsequent annealing were studied by Rutherford backscattering spectrometry /channeling (RBS/C), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Approximately 1000 Au2+/nm2 was implanted at room temperature in TiO2(110) substrates. TEM and SEM measurements revel that rounded nanoclusters were formed during the implantation. In contrast subsequent annealing in air for 10 hours at 1275 K promoted the formation of faceted (rectangular shaped) Au nano structures in TiO2. RBS channeling measurements further reveled that Au atoms randomly occupied in the host TiO2 lattice during the implantation. However, some ofmore » the gold atoms were moved into the Ti lattice position after annealing.« less

Size and Shape of Amyloid Fibrils Induced by Ganglioside Nanoclusters: Role of Sialyl Oligosaccharide in Fibril Formation.

PubMed

Matsubara, Teruhiko; Nishihara, Masaya; Yasumori, Hanaki; Nakai, Mako; Yanagisawa, Katsuhiko; Sato, Toshinori

2017-12-05

Ganglioside-enriched microdomains in the presynaptic neuronal membrane play a key role in the initiation of amyloid ß-protein (Aß) assembly related to Alzheimer's disease. We previously isolated lipids from a detergent-resistant membrane microdomain fraction of synaptosomes prepared from aged mouse brain and found that spherical Aß assemblies were formed on Aß-sensitive ganglioside nanoclusters (ASIGN) of reconstituted lipid bilayers in the synaptosomal fraction. In the present study, we investigated the role of oligosaccharides in Aß fibril formation induced by ganglioside-containing mixed lipid membranes that mimic the features of ASIGN. Ganglioside nanoclusters were constructed as ternary mixed lipid bilayers composed of ganglioside (GM1, GM2, GM3, GD1a, or GT1b), sphingomyelin, and cholesterol, and their surface topography was visualized by atomic force microscopy. Aß fibril formation on the nanocluster was strongly induced in the presence of 10 mol % ganglioside, and Aß-sensitive features were observed at cholesterol contents of 35-55 mol %. GM1-, GD1a-, and GT1b-containing membranes induced longer fibrils than those containing GD1b and GM2, indicating that the terminal galactose of GM1 along with N-acetylneuraminic acid accelerates protofibril elongation. These results demonstrate that Aß fibril formation is induced by ASIGN that are highly enriched ganglioside nanoclusters with a limited number of components and that the generation and elongation of Aß protofibrils are regulated by the oligosaccharide structure of gangliosides.

Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry.

PubMed

Berlind, T; Tengvall, P; Hultman, L; Arwin, H

2011-03-01

Thin films of amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride were deposited by reactive magnetron sputtering and optically characterized with spectroscopic ellipsometry. Complementary studies using scanning electron microscopy and atomic force microscopy were performed. The films were exposed to human serum albumin (HSA) and the adsorption was monitored in situ using dynamic ellipsometry. From the ellipsometric data the adsorbed amount of proteins was quantified in terms of surface mass density using de Feijter's model. The results indicate larger adsorption of proteins onto the amorphous films compared to the films with a more textured structure. Complementary studies with 125I-labeled HSA showed an apparent protein adsorption up to six times larger compared to the ellipsometry measurement. In addition, the four types of films were incubated in blood plasma followed by exposure to anti-fibrinogen, anti-HMWK or anti-C3c, revealing the materials' response to complement and contact activation. The amorphous and graphitic carbon nitride exhibit rather high immune activity compared to a titanium reference, whereas the amorphous carbon and the fullerene-like CNx show less immune complement deposition. Compared to the reference, all films exhibit indications of a stronger ability to initiate the intrinsic pathway of coagulation. Finally, the surfaces' bone-bonding ability was investigated by examination of their ability to form calcium phosphate crystals in a simulated body fluid, with a-CNx depositing most calcium phosphate after 21 days of incubation. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Trap-state-dominated suppression of electron conduction in carbon nanotube thin-film transistors.

PubMed

Qian, Qingkai; Li, Guanhong; Jin, Yuanhao; Liu, Junku; Zou, Yuan; Jiang, Kaili; Fan, Shoushan; Li, Qunqing

2014-09-23

The often observed p-type conduction of single carbon nanotube field-effect transistors is usually attributed to the Schottky barriers at the metal contacts induced by the work function differences or by the doping effect of the oxygen adsorption when carbon nanotubes are exposed to air, which cause the asymmetry between electron and hole injections. However, for carbon nanotube thin-film transistors, our contrast experiments between oxygen doping and electrostatic doping demonstrate that the doping-generated transport barriers do not introduce any observable suppression of electron conduction, which is further evidenced by the perfect linear behavior of transfer characteristics with the channel length scaling. On the basis of the above observation, we conclude that the environmental adsorbates work by more than simply shifting the Fermi level of the CNTs; more importantly, these adsorbates cause a poor gate modulation efficiency of electron conduction due to the relatively large trap state density near the conduction band edge of the carbon nanotubes, for which we further propose quantitatively that the adsorbed oxygen-water redox couple is responsible.

Titanyl phthalocyanine ambipolar thin film transistors making use of carbon nanotube electrodes

NASA Astrophysics Data System (ADS)

Coppedè, Nicola; Valitova, Irina; Mahvash, Farzaneh; Tarabella, Giuseppe; Ranzieri, Paolo; Iannotta, Salvatore; Santato, Clara; Martel, Richard; Cicoira, Fabio

2014-12-01

The capability of efficiently injecting charge carriers into organic films and finely tuning their morphology and structure is crucial to improve the performance of organic thin film transistors (OTFTs). In this work, we investigate OTFTs employing carbon nanotubes (CNTs) as the source-drain electrodes and, as the organic semiconductor, thin films of titanyl phthalocyanine (TiOPc) grown by supersonic molecular beam deposition (SuMBD). While CNT electrodes have shown an unprecedented ability to improve charge injection in OTFTs, SuMBD is an effective technique to tune film morphology and structure. Varying the substrate temperature during deposition, we were able to grow both amorphous (low substrate temperature) and polycrystalline (high substrate temperature) films of TiOPc. Regardless of the film morphology and structure, CNT electrodes led to superior charge injection and transport performance with respect to benchmark Au electrodes. Vacuum annealing of polycrystalline TiOPc films with CNT electrodes yielded ambipolar OTFTs.

Nanostructures nucleation in carbon-metal gaseous phase: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Galiullina, G. M.; Orekhov, N. D.; Stegailov, V. V.

2018-01-01

We perform nonequilibrium molecular dynamics simulation of carbon nanoclusters nucleation and early stages of growth from the gaseous phase. We analyze the catalytic effect of iron atoms on the nucleation kinetics and structure of the resultant nanoparticles. Reactive Force Field (ReaxFF) is used in the simulations for the description of bond formation and dissociation during the nucleation process at the nanoscale. The catalytic effect of iron reveals itself even on nanosecond simulation times: iron atoms accelerate the process of clustering but result in less graphitized carbon structures.

Fabrication and characterization of carbon-backed thin 208Pb targets.

PubMed

Thakur, Meenu; Dubey, R; Abhilash, S R; Behera, B R; Mohanty, B P; Kabiraj, D; Ojha, Sunil; Duggal, Heena

2016-01-01

Thin carbon-backed isotopically enriched 208 Pb targets were required for our experiment aimed to study the reaction dynamics for 48 Ti +  208 Pb system, populating the near super-heavy nucleus 256 Rf, through mass-energy correlation of the fission fragments. Purity and thickness of the targets are of utmost importance in such studies as these factors have strong influence on the measurement accuracy of mass and energy distribution of fission fragments. 208 Pb targets with thickness ranging from 60 μg/cm 2 to 250 μg/cm 2 have been fabricated in high vacuum environment using physical vapor deposition method. Important points in the method are as follows: • 208 Pb was deposited using resistive heating method, whereas carbon (backing foil) deposition was performed by using the electron beam bombardment technique.•Different characterization techniques such as Particle Induced X-ray Emission (PIXE), Energy Dispersive X-Ray Fluorescence (EDXRF) and Rutherford Backscattering Spectrometry (RBS) were used to assert the purity and thickness of the targets.•These targets have successfully been used to accomplish our experimental objectives.

Preparation of Au Nanoclusters-Modified Polylactic Acid Fiber with Bright Red Fluorescence and its Use as Sensing Probe.

PubMed

Zhu, Wenli; Li, Huili; Wan, Ajun; Liu, Lanbo

2017-01-01

In present work, the Au nanoclusters-modified polylactic acid fiber (PLA-Au NCs) with bright red fluorescence were fabricated by the encapsulation of Au nanoclusters (Au NCs) in the PLA fiber treated with H 2 O 2 . The Au 25 nanoclusters stabilized by bovine serum albumin (BSA-Au NCs) were prepared via an improved "green" synthetic routine. With pretreatment of the PLA fiber in H 2 O 2 concentration of 12 and 18 %, the as-prepared PLA-Au NCs exhibited brighter red emission with a strong peak centered at ~640 nm than BSA-Au NCs. The fluorescence can be quenched by nitric oxide (NO). A good linear relationship between the relative fluorescence quenching intensity of the as-prepared PLA-Au NCs and the concentration of NO can be obtained in the range of 0.0732 to 0.7320 mM, and the detection limit was 0.0070 mM.

Self-Assembled Peptide-Lanthanide Nanoclusters for Safe Tumor Therapy: Overcoming and Utilizing Biological Barriers to Peptide Drug Delivery.

PubMed

Yan, Jin; He, Wangxiao; Yan, Siqi; Niu, Fan; Liu, Tianya; Ma, Bohan; Shao, Yongping; Yan, Yuwei; Yang, Guang; Lu, Wuyuan; Du, Yaping; Lei, Bo; Ma, Peter X

2018-02-27

Developing a sophisticated nanomedicine platform to deliver therapeutics effectively and safely into tumor/cancer cells remains challenging in the field of nanomedicine. In particular, reliable peptide drug delivery systems capable of overcoming biological barriers are still lacking. Here, we developed a simple, rapid, and robust strategy to manufacture nanoclusters of ∼90 nm in diameter that are self-assembled from lanthanide-doped nanoparticles (5 nm), two anticancer peptides with different targets (BIM and PMI), and one cyclic peptide iNGR targeted to cancer cells. The peptide-lanthanide nanoclusters (LDC-PMI-BIM-iNGR) enhanced the resistance of peptide drugs to proteolysis, disassembled in response to reductive conditions that are present in the tumor microenvironment and inhibited cancer cell growth in vitro and in vivo. Notably, LDC-PMI-BIM-iNGR exhibited extremely low systemic toxicity and side effects in vivo. Thus, the peptide-lanthanide nanocluster may serve as an ideal multifunctional platform for safe, targeted, and efficient peptide drug delivery in cancer therapy.

Gadolinium embedded iron oxide nanoclusters as T1-T2 dual-modal MRI-visible vectors for safe and efficient siRNA delivery

NASA Astrophysics Data System (ADS)

Wang, Xiaoyong; Zhou, Zijian; Wang, Zhiyong; Xue, Yunxin; Zeng, Yun; Gao, Jinhao; Zhu, Lei; Zhang, Xianzhong; Liu, Gang; Chen, Xiaoyuan

2013-08-01

This report illustrates a new strategy of designing a T1-T2 dual-modal magnetic resonance imaging (MRI)-visible vector for siRNA delivery and MRI. Hydrophobic gadolinium embedded iron oxide (GdIO) nanocrystals are self-assembled into nanoclusters in the water phase with the help of stearic acid modified low molecular weight polyethylenimine (stPEI). The resulting water-dispersible GdIO-stPEI nanoclusters possess good stability, monodispersity with narrow size distribution and competitive T1-T2 dual-modal MR imaging properties. The nanocomposite system is capable of binding and delivering siRNA for knockdown of a gene of interest while maintaining its magnetic properties and biocompatibility. This new gadolinium embedded iron oxide nanocluster provides an important platform for safe and efficient gene delivery with non-invasive T1-T2 dual-modal MRI monitoring capability.This report illustrates a new strategy of designing a T1-T2 dual-modal magnetic resonance imaging (MRI)-visible vector for siRNA delivery and MRI. Hydrophobic gadolinium embedded iron oxide (GdIO) nanocrystals are self-assembled into nanoclusters in the water phase with the help of stearic acid modified low molecular weight polyethylenimine (stPEI). The resulting water-dispersible GdIO-stPEI nanoclusters possess good stability, monodispersity with narrow size distribution and competitive T1-T2 dual-modal MR imaging properties. The nanocomposite system is capable of binding and delivering siRNA for knockdown of a gene of interest while maintaining its magnetic properties and biocompatibility. This new gadolinium embedded iron oxide nanocluster provides an important platform for safe and efficient gene delivery with non-invasive T1-T2 dual-modal MRI monitoring capability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02797j

Logic circuits composed of flexible carbon nanotube thin-film transistor and ultra-thin polymer gate dielectric

PubMed Central

Lee, Dongil; Yoon, Jinsu; Lee, Juhee; Lee, Byung-Hyun; Seol, Myeong-Lok; Bae, Hagyoul; Jeon, Seung-Bae; Seong, Hyejeong; Im, Sung Gap; Choi, Sung-Jin; Choi, Yang-Kyu

2016-01-01

Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm2 V−1 sec−1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 104), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process. PMID:27184121

Logic circuits composed of flexible carbon nanotube thin-film transistor and ultra-thin polymer gate dielectric

NASA Astrophysics Data System (ADS)

Lee, Dongil; Yoon, Jinsu; Lee, Juhee; Lee, Byung-Hyun; Seol, Myeong-Lok; Bae, Hagyoul; Jeon, Seung-Bae; Seong, Hyejeong; Im, Sung Gap; Choi, Sung-Jin; Choi, Yang-Kyu

2016-05-01

Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm2 V-1 sec-1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 104), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process.

Structural and optical properties of the naked and passivated Al{sub 5}Au{sub 5} bimetallic nanoclusters

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

Grande-Aztatzi, Rafael; Formoso, Elena; Matxain, Jon M.

The structural and optical properties of both the naked and passivated bimetallic Al{sub 5}Au{sub 5} nanoclusters have been analyzed based on data obtained from ab initio density functional theory and quantum molecular dynamics simulations. It has been found that the Al{sub 5}Au{sub 5} nanocluster possesses a hollow shaped minimum energy structure with segregated Al and Au layered domains, the former representing the electrophilic domain and the latter the nucleophilic domain. In particular, it has been shown that alkali metal cations attach in the nucleophilic domain and hop from one Au site to the next one in the picoseconds time scale,more » while anions are bound tightly to the Al atoms of the electrophilic domain. Simulating annealing studies are very suggestive of the proneness of the nanocluster towards coalescence into large cluster units, when the cluster is left unprotected by appropriate ligands. Further passivation studies with NaF salt suggest, nonetheless, the possibility of the isolation of the Al{sub 5}Au{sub 5} cluster in molten salts or ionic liquids.« less

Raman spectra boron doped amorphous carbon thin film deposited by bias assisted-CVD

NASA Astrophysics Data System (ADS)

Ishak, A.; Fadzilah, A. N.; Dayana, K.; Saurdi, I.; Malek, M. F.; Nurbaya, Z.; Shafura, A. K.; Rusop, M.

2018-05-01

Boron doped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The structural boron doped amorphous carbon films were discussed by Raman analysis through the evolution of D and G bands. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. These structural changes were further correlated with optical gap and the results obtained are discussed and compared. The estimated optical band gap is found to be 1.9 to 2.05 eV and conductivity is to be in the range of 10-5 Scm-1 to 10-4 Scm-1. The decrease of optical band gap is associated to conductivity increased which change the characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG.

In Situ Biosynthesis of Fluorescent Platinum Nanoclusters: Toward Self-Bioimaging-Guided Cancer Theranostics.

PubMed

Chen, Donghua; Zhao, Chunqiu; Ye, Jing; Li, Qiwei; Liu, Xiaoli; Su, Meina; Jiang, Hui; Amatore, Christian; Selke, Matthias; Wang, Xuemei

2015-08-19

Among the noble-metal clusters, very few reports about platinum clusters were used as bioimaging probes of tumors except as a reducing catalyst. It is first established herein that the biocompatible platinum nanoclusters are spontaneously biosynthesized by cancerous cells (i.e., HepG2 (human hepatocarcinoma), A549 (lung cancer), and others) rather than noncancerous cells (i.e., L02 (human embryo liver cells)) when incubated with micromolar chloroplatinic acid solutions. These in situ biosynthesized platinum nanoclusters could be readily realized in a biological environment and emit a bright fluorescence at 460 nm, which could be further utilized to facilitate an excellent cancer-cell-killing efficiency when combined with porphyrin derivatives for photothermal treatment. This raises the possibility of providing a promising and precise bioimaging strategy for specific fluorescent self-biomarking of tumor locations and realizing fluorescence imaging-guided photothermal therapy of tumors.

Sodium-Ion Batteries: Improving the Rate Capability of 3D Interconnected Carbon Nanofibers Thin Film by Boron, Nitrogen Dual-Doping.

PubMed

Wang, Min; Yang, Yang; Yang, Zhenzhong; Gu, Lin; Chen, Qianwang; Yu, Yan

2017-04-01

Boron, nitrogen dual-doping 3D hard carbon nanofibers thin film is synthesized using a facile process. The nanofibers exhibit high specific capacity and remarkable high-rate capability due to the synergistic effect of 3D porous structure, large surface area, and enlarged carbon layer spacing, and the B, N codoping-induced defects.

Dimethylammonium hexanoate stabilized rhodium(0) nanoclusters identified as true heterogeneous catalysts with the highest observed activity in the dehydrogenation of dimethylamine-borane.

PubMed

Zahmakiran, Mehmet; Ozkar, Saim

2009-09-21

Herein we report the discovery of a superior dimethylamine-borane dehydrogenation catalyst, more active than the prior best heterogeneous catalyst (Jaska, C. A.; Manners, I. J. Am. Chem. Soc. 2004, 126, 9776) reported to date for the dehydrogenation of dimethylamine-borane. The new catalyst system consists of rhodium(0) nanoclusters stabilized by C(5)H(11)COO(-) anions and Me(2)H(2)N(+) cations and can reproducibly be formed from the reduction of rhodium(II) hexanoate during dehydrogenation of dimethylamine-borane at room temperature. Rhodium(0) nanoclusters in an average particle size of 1.9 +/- 0.6 nm Rh(0)(approximately 190) nanoclusters) provide 1040 turnovers over 26 h with a record initial turnover frequency (TOF) of 60 h(-1) (the average TOF value is 40 h(-1)) in the dehydrogenation of dimethylamine-borane, yielding 100% of the cyclic product (Me(2)NBH(2))(2) at room temperature. The work reported here also includes the full experimental details of the following major components: (i) Characterization of dimethylammonium hexanoate stabilized rhodium(0) nanoclusters by using TEM, STEM, EDX, XRD, UV-vis, XPS, FTIR, (1)H, (13)C, and (11)B NMR spectroscopy, and elemental analysis. (ii) Collection of a wealth of previously unavailable kinetic data to determine the rate law and activation parameters for catalytic dehydrogenation of dimethylamine-borane. (iii) Monitoring of the formation kinetics of the rhodium(0) nanoclusters by a fast dimethylamine-borane dehydrogenation catalytic reporter reaction (Watzky, M. A.; Finke, R. G. J. Am. Chem. Soc. 1997, 119, 10382) at various [Me(2)NH.BH(3)]/[Rh] ratios and temperatures. Significantly, sigmoidal kinetics of catalyst formation was found to be well fit to the two-step, slow nucleation and then autocatalytic surface growth mechanism, A --> B (rate constant k(1)) and A + B --> 2B (rate constant k(2)), in which A is [Rh(C(5)H(11)CO(2))(2)](2) and B is the growing, catalytically active rhodium(0) nanoclusters. (iv) Mercury

Growth of in situ functionalized luminescent silver nanoclusters by direct reduction and size focusing.

PubMed

Muhammed, Madathumpady Abubaker Habeeb; Aldeek, Fadi; Palui, Goutam; Trapiella-Alfonso, Laura; Mattoussi, Hedi

2012-10-23

We have used one phase growth reaction to prepare a series of silver nanoparticles (NPs) and luminescent nanoclusters (NCs) using sodium borohydride (NaBH(4)) reduction of silver nitrate in the presence of molecular scale ligands made of polyethylene glycol (PEG) appended with lipoic acid (LA) groups at one end and reactive (-COOH/-NH(2)) or inert (-OCH(3)) functional groups at the other end. The PEG segment in the ligand promotes solubility in a variety of solvents including water, while LAs provide multidentate coordinating groups that promote Ag-ligand complex formation and strong anchoring onto the NP/NC surface. The particle size and properties were primarily controlled by varying the Ag-to-ligand (Ag:L) molar ratios and the molar amount of NaBH(4) used. We found that while higher Ag:L ratios produced NPs, luminescent NCs were formed at lower ratios. We also found that nonluminescent NPs can be converted into luminescent clusters, via a process referred to as "size focusing", in the presence of added excess ligands and reducing agent. The nanoclusters emit in the far red region of the optical spectrum with a quantum yield of ~12%. They can be redispersed in a number of solvents with varying polarity while maintaining their optical and spectroscopic properties. Our synthetic protocol also allowed control over the number and type of reactive functional groups per nanocluster.

Iron Oxide Colloidal Nanoclusters as Theranostic Vehicles and Their Interactions at the Cellular Level.

PubMed

Kostopoulou, Athanasia; Brintakis, Konstantinos; Fragogeorgi, Eirini; Anthousi, Amalia; Manna, Liberato; Begin-Colin, Sylvie; Billotey, Claire; Ranella, Anthi; Loudos, George; Athanassakis, Irene; Lappas, Alexandros

2018-05-09

Advances in surfactant-assisted chemical approaches have led the way for the exploitation of nanoscale inorganic particles in medical diagnosis and treatment. In this field, magnetically-driven multimodal nanotools that perform both detection and therapy, well-designed in size, shape and composition, are highly advantageous. Such a theranostic material—which entails the controlled assembly of smaller (maghemite) nanocrystals in a secondary motif that is highly dispersible in aqueous media—is discussed here. These surface functionalized, pomegranate-like ferrimagnetic nanoclusters (40⁻85 nm) are made of nanocrystal subunits that show a remarkable magnetic resonance imaging contrast efficiency, which is better than that of the superparamagnetic contrast agent Endorem © . Going beyond this attribute and with their demonstrated low cytotoxicity in hand, we examine the critical interaction of such nanoprobes with cells at different physiological environments. The time-dependent in vivo scintigraphic imaging of mice experimental models, combined with a biodistribution study, revealed the accumulation of nanoclusters in the spleen and liver. Moreover, the in vitro proliferation of spleen cells and cytokine production witnessed a size-selective regulation of immune system cells, inferring that smaller clusters induce mainly inflammatory activities, while larger ones induce anti-inflammatory actions. The preliminary findings corroborate that the modular chemistry of magnetic iron oxide nanoclusters stimulates unexplored pathways that could be driven to alter their function in favor of healthcare.

Polyelectrolyte-assisted preparation of gold nanocluster-doped silica particles with high incorporation efficiency and improved stability

NASA Astrophysics Data System (ADS)

Wang, Haonan; Huang, Zhenzhen; Guo, Zilong; Yang, Wensheng

2017-07-01

In this paper, we reported an approach for efficient incorporation of glutathione-capped gold nanoclusters (GSH-Au NCs) into silica particles with the assistance of a polyelectrolyte, poly-diallyldimethyl-ammoniumchloride (PDDA). In this approach, the negatively charged GSH-Au NCs were firstly mixed with the positively charged PDDA to form PDDA-Au NC complexes. Then, the complexes were added into a pre-hydrolyzed Stöber system to get the Au NCs-doped silica particles. With increased ratio of PDDA in the complexes, the negative charges on surface of the Au NCs were neutralized gradually and finally reversed to positive in presence of excess PDDA, which facilitated the incorporation of the Au NCs into the negatively charged silica matrix. Under the optimal amount of PDDA in the complexes, the incorporation efficiency of Au NCs could be as high as 88%. After being incorporated into the silica matrix, the Au NCs become much robust against pH and heavy metal ions attributed to the protection effect of silica and PDDA. This approach was also extendable to highly efficient incorporation of other negatively charged metal nanoclusters, such as bovine serum albumin-capped Cu nanoclusters, into silica matrix.

Cytidine-directed rapid synthesis of water-soluble and highly yellow fluorescent bimetallic AuAg nanoclusters.

PubMed

Zhang, Yuanyuan; Jiang, Hui; Ge, Wei; Li, Qiwei; Wang, Xuemei

2014-09-16

Fluorescent gold/silver nanoclusters templated by DNA or oligonucleotides have been widely reported since DNA or oligonucleotides could be designed to position a few metal ions at close proximity prior to their reduction, but nucleoside-templated synthesis is more challenging. In this work, a novel type of strategy taking cytidine (C) as template to rapid synthesis of fluorescent, water-soluble gold and silver nanoclusters (C-AuAg NCs) has been developed. The as-prepared C-AuAg NCs have been characterized by UV-vis absorption spectroscopy, fluorescence, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and inductively coupled plasma mass spectroscopy (ICP-MS). The characterizations demonstrate that C-AuAg NCs with a diameter of 1.50 ± 0.31 nm, a quantum yield ∼9%, and an average lifetime ∼6.07 μs possess prominent fluorescence properties, good dispersibility, and easy water solubility, indicating the promising application in bioanalysis and biomedical diagnosis. Furthermore, this strategy by rapid producing of highly fluorescent nanoclusters could be explored for the possible recognition of some disease-related changes in blood serum. This raises the possibility of their promising application in bioanalysis and biomedical diagnosis.

Responses of forest carbon and water coupling to thinning treatments at both the leaf and individual tree levels in a 16-year-old natural Pinus Contorta stand

NASA Astrophysics Data System (ADS)

Wang, Y.; Wei, A.; del Campo, A.; Li, Q.; Giles-Hansen, K.

2017-12-01

Large-scale disturbances in Canadian forests, including mountain pine beetle infestation in western Canada, forest fires, timber harvesting and climate change impacts, have significantly affected both forest carbon and water cycles. Thinning, which selectively removes trees at a given forest stand, may be an effective tool to mitigate the effect of these disturbances. Various studies have been conducted to assess the thinning effect on growth, transpiration, and nutrient availability; however, relatively few studies have been conducted to examine its effect on the coupling of forest carbon and water. Thus, the objective of this research is to evaluate the effect of thinning on forest carbon and water coupling at both the leaf and tree levels in a 16-year-old natural Pinus Contorta forest in the interior of British Columbia in Canada. We used water-use efficiency (WUE), the ratio of basal area increment (BA) to tree transpiration (E), as the indicator of the carbon and water coupling at individual tree level, and use intrinsic water-use efficiency (iWUE), the ratio of photosynthesis (A) to stomatal conductance (G), to represent the coupling at the leaf level. Field experiments were conducted in the Upper Penticton Watershed where the mean annual precipitation is 750 mm with seasonal drought during summer. A randomized block design was used, with three blocks each containing two thinning intensities and one unthinned plot (T1: 4,500, T2: 1,100, C: 26,400 trees per ha.). From May to October 2016, basal diameter, sap flow, and environmental conditions were monitored continuously at every 20 minutes, while A and G were measured weekly. Preliminary results showed that thinning significantly increased solar radiation, wind speed, and soil moisture in the treatment plots, where the changes observed were proportional to the intensity of the thinning; but thinning did not change stand level temperature and relative humidity. Thinning also significantly enhanced tree E and BA

Copper Phthalocyanine Functionalized Single-Walled Carbon Nanotubes: Thin Films for Optical Detection.

PubMed

Banimuslem, Hikmat; Hassan, Aseel; Basova, Tamara; Durmuş, Mahmut; Tuncel, Sinem; Esenpinar, Aliye Asli; Gürek, Ayşe Gül; Ahsen, Vefa

2015-03-01

Thin films of non-covalently hybridized single-walled carbon nanotubes (SWCNT) and tetra-substituted copper phthalocyanine (CuPcR4) molecules have been produced from their solutions in dimethylformamide (DMF). FTIR spectra revealed the 7π-7π interaction between SWCNTs and CuPcR4 molecules. DC conductivity of films of acid-treated SWCNT/CuPcR4 hybrid has increased by more than three orders of.magnitude in comparison with conductivity of CuPcR4 films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements have shown that films obtained from the acid-treated SWCNTs/CuPcR4 hybrids demonstrated more homogenous surface which is ascribed to the highly improved solubility of the hybrid powder in DMF Using total internal reflection ellipsometry spectroscopy (TIRE), thin films of the new hybrid have been examined as an optical sensing membrane for the detection of benzo[a]pyrene in water to demonstrate the sensing properties of the hybrid.

Effect of ordered mesoporous carbon contact layer on the sensing performance of sputtered RuO2 thin film pH sensor.

PubMed

Lonsdale, W; Maurya, D K; Wajrak, M; Alameh, K

2017-03-01

The effect of contact layer on the pH sensing performance of a sputtered RuO 2 thin film pH sensor is investigated. The response of pH sensors employing RuO 2 thin film electrodes on screen-printed Pt, carbon and ordered mesoporous carbon (OMC) contact layers are measured over a pH range from 4 to 10. Working electrodes with OMC contact layer are found to have Nernstian pH sensitivity (-58.4mV/pH), low short-term drift rate (5.0mV/h), low hysteresis values (1.13mV) and fast reaction times (30s), after only 1h of conditioning. A pH sensor constructed with OMC carbon contact layer displays improved sensing performance compared to Pt and carbon-based counterparts, making this electrode more attractive for applications requiring highly-accurate pH sensing with reduced conditioning time. Copyright © 2016 Elsevier B.V. All rights reserved.

Specific cancer-associated mutations in the switch III region of Ras increase tumorigenicity by nanocluster augmentation

PubMed Central

Šolman, Maja; Ligabue, Alessio; Blaževitš, Olga; Jaiswal, Alok; Zhou, Yong; Liang, Hong; Lectez, Benoit; Kopra, Kari; Guzmán, Camilo; Härmä, Harri; Hancock, John F; Aittokallio, Tero; Abankwa, Daniel

2015-01-01

Hotspot mutations of Ras drive cell transformation and tumorigenesis. Less frequent mutations in Ras are poorly characterized for their oncogenic potential. Yet insight into their mechanism of action may point to novel opportunities to target Ras. Here, we show that several cancer-associated mutations in the switch III region moderately increase Ras activity in all isoforms. Mutants are biochemically inconspicuous, while their clustering into nanoscale signaling complexes on the plasma membrane, termed nanocluster, is augmented. Nanoclustering dictates downstream effector recruitment, MAPK-activity, and tumorigenic cell proliferation. Our results describe an unprecedented mechanism of signaling protein activation in cancer. DOI: http://dx.doi.org/10.7554/eLife.08905.001 PMID:26274561

Imaging nanoclusters in the constant height mode of the dynamic SFM.

PubMed

Barth, Clemens; Pakarinen, Olli H; Foster, Adam S; Henry, Claude R

2006-04-14

For the first time, high quality images of metal nanoclusters which were recorded in the constant height mode of a dynamic scanning force microscope (dynamic SFM) are shown. Surfaces of highly ordered pyrolytic graphite (HOPG) were used as a test substrate since metal nanoclusters with well defined and symmetric shapes can be created by epitaxial growth. We performed imaging of gold clusters with sizes between 5 and 15 nm in both scanning modes, constant Δf mode and constant height mode, and compared the image contrast. We notice that clusters in constant height images appear much sharper, and exhibit more reasonable lateral shapes and sizes in comparison to images recorded in the constant Δf mode. With the help of numerical simulations we show that only a microscopically small part of the tip apex (nanotip) is probably the main contributor for the image contrast formation. In principle, the constant height mode can be used for imaging surfaces of any material, e.g. ionic crystals, as shown for the system Au/NaCl(001).

DNA-stabilized silver nanoclusters and carbon nanoparticles oxide: A sensitive platform for label-free fluorescence turn-on detection of HIV-DNA sequences.

PubMed

Ye, Yu-Dan; Xia, Li; Xu, Dang-Dang; Xing, Xiao-Jing; Pang, Dai-Wen; Tang, Hong-Wu

2016-11-15

Based on the remarkable difference between the interactions of carbon nanoparticles (CNPs) oxide with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), and the fact that fluorescence of DNA-stabilized silver nanoclusters (AgNCs) can be quenched by CNPs oxide, DNA-functionalized AgNCs were applied as label-free fluorescence probes and a novel fluorescence resonance energy transfer (FRET) sensor was successfully constructed for the detection of human immunodeficiency virus (HIV) DNA sequences. CNPs oxide were prepared with the oxidation of candle soot, hence it is simple, time-saving and low-cost. The strategy of dual AgNCs probes was applied to improve the detection sensitivity by using dual- probe capturing the same target DNA in a sandwich mode and as the fluorescence donor, and using CNPs oxide as the acceptor. In the presence of target DNA, a dsDNA hybrid forms, leading to the desorption of the ssDNA-AgNCs probes from CNPs oxide, and the recovering of fluorescence of the AgNCs in a HIV-DNA concentration-dependent manner. The results show that HIV-DNA can be detected in the range of 1-50nM with a detection limit of 0.40nM in aqueous buffer. The method is simple, rapid and sensitive with no need of labeled fluorescent probes, and moreover, the design of fluorescent dual-probe makes full use of the excellent fluorescence property of AgNCs and further improves the detection sensitivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Piezoresistivity of mechanically drawn single-walled carbon nanotube (SWCNT) thin films-: mechanism and optimizing principle

NASA Astrophysics Data System (ADS)

Obitayo, Waris

The individual carbon nanotube (CNT) based strain sensors have been found to have excellent piezoresistive properties with a reported gauge factor (GF) of up to 3000. This GF on the other hand, has been shown to be structurally dependent on the nanotubes. In contrast, to individual CNT based strain sensors, the ensemble CNT based strain sensors have very low GFs e.g. for a single walled carbon nanotube (SWCNT) thin film strain sensor, GF is ~1. As a result, studies which are mostly numerical/analytical have revealed the dependence of piezoresistivity on key parameters like concentration, orientation, length and diameter, aspect ratio, energy barrier height and Poisson ratio of polymer matrix. The fundamental understanding of the piezoresistive mechanism in an ensemble CNT based strain sensor still remains unclear, largely due to discrepancies in the outcomes of these numerical studies. Besides, there have been little or no experimental confirmation of these studies. The goal of my PhD is to study the mechanism and the optimizing principle of a SWCNT thin film strain sensor and provide experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like orientation, network density, bundle diameter (effective tunneling area), and length is studied, and how one can effectively optimize the piezoresistive behavior of a SWCNT thin film strain sensors. To reach this goal, my first research accomplishment involves the study of orientation of SWCNTs and its effect on the piezoresistivity of mechanically drawn SWCNT thin film based piezoresistive sensors. Using polarized Raman spectroscopy analysis and coupled electrical-mechanical test, a quantitative relationship between the strain sensitivity and SWCNT alignment order parameter was established. As compared to randomly oriented SWCNT thin films, the one with draw ratio of 3.2 exhibited ~6x increase on the GF. My second accomplishment involves studying the

Exploring luminescence-based temperature sensing using protein-passivated gold nanoclusters.

PubMed

Chen, Xi; Essner, Jeremy B; Baker, Gary A

2014-08-21

We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol-gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers.

Thin films composed of multiwalled carbon nanotubes, gold nanoparticles and myoglobin for humidity detection at room temperature.

PubMed

Qi, Zhi-mei; Wei, Mingdeng; Honma, Itaru; Zhou, Haoshen

2007-02-02

Optically transparent and electrically conductive nanocomposite thin films consisting of multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and myoglobin molecules that glue GNPs and MWCNTs together are fabricated for the first time on glass substrates from aqueous solution. The nanocomposite thin film is capable of varying its resistance, impedance or optical transmittance at room temperature in response to changes in ambient humidity. The conductometric sensitivity to relative humidity (RH) of the nanocomposite thin film is compared with those of the pure and Mb-functionalized MWCNT layers. The pure MWCNT layer shows a small increase in its resistance with increasing RH due to the effect of p-type semiconducting nanotubes present in the film. In contrast, a four times higher sensitivity to RH is observed for both the nanocomposite and Mb-functionalized MWCNT thin films. The sensitivity enhancement is attributable to swelling of the thin films induced by water absorption in the presence of Mb molecules, which increases the inter-nanotube spacing and thereby causes a further increase of the film resistance. A humidity change as low as DeltaRH=0.3 % has been readily detected by conductometry using the nanocomposite thin film.

Structure of disordered gold-polymer thin films using small angle x-ray scattering

NASA Astrophysics Data System (ADS)

Teixeira, F. S.; Salvadori, M. C.; Cattani, M.; Brown, I. G.

2010-11-01

We have investigated the structure of disordered gold-polymer thin films using small angle x-ray scattering and compared the results with the predictions of a theoretical model based on two approaches—a structure form factor approach and the generalized Porod law. The films are formed of polymer-embedded gold nanoclusters and were fabricated by very low energy gold ion implantation into polymethylmethacrylate (PMMA). The composite films span (with dose variation) the transition from electrically insulating to electrically conducting regimes, a range of interest fundamentally and technologically. We find excellent agreement with theory and show that the PMMA-Au films have monodispersive or polydispersive characteristics depending on the implanted ion dose.

Metal nanoparticles as a conductive catalyst

DOEpatents

Coker, Eric N [Albuquerque, NM

2010-08-03

A metal nanocluster composite material for use as a conductive catalyst. The metal nanocluster composite material has metal nanoclusters on a carbon substrate formed within a porous zeolitic material, forming stable metal nanoclusters with a size distribution between 0.6-10 nm and, more particularly, nanoclusters with a size distribution in a range as low as 0.6-0.9 nm.

Organic/carbon nanotubes hybrid thin films for chemical detection

NASA Astrophysics Data System (ADS)

Banimuslem, Hikmat Adnan

Metallophthalocyanines (MPcs) are classified as an important class of conjugated materials and they possess several advantages attributed to their unique chemical structure. Carbon nanotubes (CNT), on the other hand, are known to enhance the properties of nano-composites in the conjugated molecules, due to their one dimensional electronic skeleton, high surface area and high aspect ratio. In this thesis, work has been carried out on the investigation of different substituted metal-phthalocyanines with the aim of developing novel hybrid film structures which incorporates these phthalocyanines and single-walled carbon nanotubes (SWCNT) for chemical detection applications. Octa-substituted copper phthalocyanines (CuPcR[8]) have been characterised using UV-visible absorption spectroscopy. Obtained spectra have yielded an evidence of a thermally induced molecular reorganization in the films. Influence of the nature of substituents in the phthalocyanine molecule on the thin films conductivity was also investigated. Octa-substituted lead (II) phthalocyanines (PbPcR[8]) have also been characterized using UV-visible spectroscopy. Sandwich structures of ITO/PbPcR[8]/In were prepared to investigate the electronic conduction in PbPcR[8]. The variation in the J(V) behavior of the films as a result of heat treatment is expected to be caused by changes in the alignment inside the columnar stacking of the molecules of the films. Thin films of non-covalently hybridised SWCNT and tetra-substituted copper phthalocyanine (CuPcR[4]) molecules have been produced. FTIR, DC conductivity, SEM and AFM results have revealed the [mathematical equation]; interaction between SWCNTs and CuPCR[4] molecules and shown that films obtained from the acid-treated SWCNTs/CuPcR[4] hybrids demonstrated more homogenous surface. Thin films of pristine CuPCR[4] and CuPcR[4]/S WCNT were prepared by spin coating onto gold-coated glass slides and applied as active layers for the detection of benzo

Hollow Silicon Nanospheres Encapsulated with a Thin Carbon Shell: An Electrochemical Study

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

Ashuri, Maziar; He, Qianran; Liu, Yuzi

In this study we have investigated the electrochemical properties of hollow silicon nanospheres encapsulated with a thin carbon shell, HSi@C, as a potential candidate for lithium-ion battery anodes. Hollow Si nanospheres are formed using a templating method which is followed by carbon coating via carbonization of a pyrrole precursor to form HSi@C. The synthesis conditions and the resulting structure of HSi@C have been studied in detail to obtain the target design of hollow Si nanospheres encapsulated with a carbon shell. The HSi@C obtained exhibits much better electrochemical cycle stability than both micro-and nano-size silicon anodes and deliver a stable specificmore » capacity of 700 mA h g(-1) after 100 cycles at a current density of 2 A g(-1) and 800 mA h g(-1) after 120 cycles at a current density of 1 A g(-1). The superior performance of HSi@C is attributed to the synergistic combination of the nanostructured material, the enhanced conductivity, and the presence of the central void space for Si expansion with little or no change in the volume of the entire HSi@C particle. This study is the first detailed investigation of the synthesis conditions to attain the desired structure of a hollow Si core with a conductive carbon shell. This study also offers guidelines to further enhance the specific capacity of HSi@C anodes in the future.« less

Hollow Silicon Nanospheres Encapsulated with a Thin Carbon Shell: An Electrochemical Study

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

Ashuri, Maziar; He, Qianran; Liu, Yuzi

In this study we have investigated the electrochemical properties of hollow silicon nanospheres encapsulated with a thin carbon shell, HSi@C, as a potential candidate for lithium-ion battery anodes. Hollow Si nanospheres are formed using a templating method which is followed by carbon coating via carbonization of a pyrrole precursor to form HSi@C. The synthesis conditions and the resulting structure of HSi@C have been studied in detail to obtain the target design of hollow Si nanospheres encapsulated with a carbon shell. The HSi@C obtained exhibits much better electrochemical cycle stability than both micro-and nano-size silicon anodes and deliver a stable specificmore » capacity of 700 mA h g(-1) after 100 cycles at a current density of 2 A g(-1) and 800 mA h g(-1) after 120 cycles at a current density of 1 A g(-1). The superior performance of HSi@C is attributed to the synergistic combination of the nanostructured material, the enhanced conductivity, and the presence of the central void space for Si expansion with little or no change in the volume of the entire HSi@C particle. This study is the first detailed investigation of the synthesis conditions to attain the desired structure of a hollow Si core with a conductive carbon shell. This study also offers guidelines to further enhance the specific capacity of HSi@C anodes in the future. (C) 2016 Elsevier Ltd. All rights reserved.« less

Bioturbation delays attenuation of DDT by clean sediment cap but promotes sequestration by thin-layered activated carbon.

PubMed

Lin, Diana; Cho, Yeo-Myoung; Werner, David; Luthy, Richard G

2014-01-21

The effects of bioturbation on the performance of attenuation by sediment deposition and activated carbon to reduce risks from DDT-contaminated sediment were assessed for DDT sediment-water flux, biouptake, and passive sampler (PE) uptake in microcosm experiments with a freshwater worm, Lumbriculus variegatus. A thin-layer of clean sediment (0.5 cm) did not reduce the DDT flux when bioturbation was present, while a thin (0.3 cm) AC cap was still capable of reducing the DDT flux by 94%. Bioturbation promoted AC sequestration by reducing the 28-day DDT biouptake (66%) and DDT uptake into PE (>99%) compared to controls. Bioturbation further promoted AC-sediment contact by mixing AC particles into underlying sediment layers, reducing PE uptake (55%) in sediment compared to the AC cap without bioturbation. To account for the observed effects from bioturbation, a mass transfer model together with a biodynamic model were developed to simulate DDT flux and biouptake, respectively, and models confirmed experimental results. Both experimental measurements and modeling predictions imply that thin-layer activated carbon placement on sediment is effective in reducing the risks from contaminated sediments in the presence of bioturbation, while natural attenuation process by clean sediment deposition may be delayed by bioturbation.

Foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Mao, Yiyin; Li, Gaoran; Guo, Yi; Li, Zhoupeng; Liang, Chengdu; Peng, Xinsheng; Lin, Zhan

2017-03-01

Lithium-sulfur batteries are promising technologies for powering flexible devices due to their high energy density, low cost and environmental friendliness, when the insulating nature, shuttle effect and volume expansion of sulfur electrodes are well addressed. Here, we report a strategy of using foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for binder-free advanced lithium-sulfur batteries through a facile confinement conversion. The carbon nanotubes interpenetrate through the metal-organic frameworks crystal and interweave the electrode into a stratified structure to provide both conductivity and structural integrity, while the highly porous metal-organic frameworks endow the electrode with strong sulfur confinement to achieve good cyclability. These hierarchical porous interpenetrated three-dimensional conductive networks with well confined S8 lead to high sulfur loading and utilization, as well as high volumetric energy density.

High-performance carbon nanotube thin-film transistors on flexible paper substrates

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

Liu, Na; Yun, Ki Nam; Yu, Hyun-Yong

Single-walled carbon nanotubes (SWCNTs) are promising materials as active channels for flexible transistors owing to their excellent electrical and mechanical properties. However, flexible SWCNT transistors have never been realized on paper substrates, which are widely used, inexpensive, and recyclable. In this study, we fabricated SWCNT thin-film transistors on photo paper substrates. The devices exhibited a high on/off current ratio of more than 10{sup 6} and a field-effect mobility of approximately 3 cm{sup 2}/V·s. The proof-of-concept demonstration indicates that SWCNT transistors on flexible paper substrates could be applied as low-cost and recyclable flexible electronics.

Carbon isotope exchange between gaseous CO2 and thin solution films: Artificial cave experiments and a complete diffusion-reaction model

NASA Astrophysics Data System (ADS)

Hansen, Maximilian; Scholz, Denis; Froeschmann, Marie-Louise; Schöne, Bernd R.; Spötl, Christoph

2017-08-01

Speleothem stable carbon isotope (δ13C) records provide important paleoclimate and paleo-environmental information. However, the interpretation of these records in terms of past climate or environmental change remains challenging because of various processes affecting the δ13C signals. A process that has only been sparsely discussed so far is carbon isotope exchange between the gaseous CO2 of the cave atmosphere and the dissolved inorganic carbon (DIC) contained in the thin solution film on the speleothem, which may be particularly important for strongly ventilated caves. Here we present a novel, complete reaction diffusion model describing carbon isotope exchange between gaseous CO2 and the DIC in thin solution films. The model considers all parameters affecting carbon isotope exchange, such as diffusion into, out of and within the film, the chemical reactions occurring within the film as well as the dependence of diffusion and the reaction rates on isotopic mass and temperature. To verify the model, we conducted laboratory experiments under completely controlled, cave-analogue conditions at three different temperatures (10, 20, 30 °C). We exposed thin (≈0.1 mm) films of a NaHCO3 solution with four different concentrations (1, 2, 5 and 10 mmol/l, respectively) to a nitrogen atmosphere containing a specific amount of CO2 (1000 and 3000 ppmV). The experimentally observed temporal evolution of the pH and δ13C values of the DIC is in good agreement with the model predictions. The carbon isotope exchange times in our experiments range from ca. 200 to ca. 16,000 s and strongly depend on temperature, film thickness, atmospheric pCO2 and the concentration of DIC. For low pCO2 (between 500 and 1000 ppmV, as for strongly ventilated caves), our time constants are substantially lower than those derived in a previous study, suggesting a potentially stronger influence of carbon isotope exchange on speleothem δ13C values. However, this process should only have an

A study for anticorrosion and tribological behaviors of thin/thick diamond-like carbon films in seawater

NASA Astrophysics Data System (ADS)

Ye, Yewei; Jia, Shujuan; Zhang, Dawei; Liu, Wei; Zhao, Haichao

2018-03-01

The thin and thick diamond-like carbon (DLC) films were prepared by unbalanced magnetron sputtering technique on 304L stainless steels and (100) silicon wafers. Microstructure, mechanical, corrosion and tribological properties were systematically investigated by SEM, Raman, nanoindenter, scratch tester, modulab electrochemical workstation and R-tec multifunctional tribological tester. Results showed that the adhesion force presented a descending trend with the growth in soaking time. The adhesion force of the thin DLC film with high residual compressive stress (‑3.72 GPa) was higher than that of the thick DLC film (‑2.96 GPa). During the corrosion test, the thick DLC film showed a higher impendence and a lower corrosion current density than the thin DLC film, which is attributed to the barrier action of large thickness. Compared to bare 304L substrate, the friction coefficients and wear rates of DLC films in seawater were obviously decreased. Meanwhile, the thin DLC film with ideal residual compressive stress, super adhesion force and good plastic deformation resistance revealed an excellent anti-wear ability in seawater.

Stable isomers and electronic, vibrational, and optical properties of WS2 nano-clusters: A first-principles study

NASA Astrophysics Data System (ADS)

Hafizi, Roohollah; Hashemifar, S. Javad; Alaei, Mojtaba; Jangrouei, MohammadReza; Akbarzadeh, Hadi

2016-12-01

In this paper, we employ an evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS2)n nano-clusters (n = 1 - 9), within three different exchange-correlation functionals. Our results suggest that n = 5 and 8 are possible candidates for the low temperature magic sizes of WS2 nano-clusters while at temperatures above 500 Kelvin, n = 7 exhibits a comparable relative stability with n = 8. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal Perdew-Burke-Ernzerhof and Becke-Lee-Yang-Parr functionals, hybrid B3LYP functional, many body based DFT+GW approach, ΔSCF method, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in a real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS2 nano-clusters.

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

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

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Rapid and efficient crossing blood-brain barrier: Hydrophobic drug delivery system based on propionylated amylose helix nanoclusters.

PubMed

Gao, Wei; Liu, Yongchun; Jing, Guixia; Li, Ke; Zhao, Yuan; Sha, Baoyong; Wang, Qiang; Wu, Daocheng

2017-01-01

A novel strategy of rapid transport across the blood-brain barrier (BBB) via phosphatidylethanolamine-triggered release is developed through both molecular dynamics (MD) simulation and experiments. Hydrophobic drugs, namely, propofol, iodine, and 1,1'-dioctadecyltetramethyl indotricarbocyanine iodide, were loaded with propionylated amylose helix (HLPAH) nanoclusters to form PLPAH, ILPAH, and DLPAH nanoclusters, respectively. These clusters were subjected to MD simulation, structure measurement, in vitro triggered study, in vivo DLPAH imaging, and analysis of PLPAH sedative effects on rabbits. Results indicated that HLPAH nanoclusters were initially located on the BBB, and the helix was unfolded to release the loaded hydrophobic drugs. The released drugs crossed the BBB and performed their functions in the central nervous system (CNS) through concentration gradient and hydrophobicity. This mechanism of HLPAH across the BBB featured high membrane permeability and specificity, rapid onset, short maintenance, rapid recovery, and lower dosage of drugs. Hence, this novel strategy is very meaningful for the development of CNS drug carriers and the proposed system could be used to improve the therapeutic effects of CNS diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

DOE PAGES

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.; ...

2017-08-10

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Experimental setup for investigation of nanoclusters at cryogenic temperatures by electron spin resonance and optical spectroscopies

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

Mao, S., E-mail: maoshunghost@tamu.edu; Meraki, A.; McColgan, P. T.

2014-07-15

We present the design and performance of an experimental setup for simultaneous electron spin resonance (ESR) and optical studies of nanoclusters with stabilized free radicals at cryogenic temperatures. A gas mixture of impurities and helium after passing through a RF discharge for dissociation of molecules is directed onto the surface of superfluid helium to form the nanoclusters of impurities. A specially designed ESR cavity operated in the TE{sub 011} mode allows optical access to the sample. The cavity is incorporated into a homemade insert which is placed inside a variable temperature insert of a Janis {sup 4}He cryostat. The temperaturemore » range for sample investigation is 1.25–300 K. A Bruker EPR 300E and Andor 500i optical spectrograph incorporated with a Newton EMCCD camera are used for ESR and optical registration, respectively. The current experimental system makes it possible to study the ESR and optical spectra of impurity-helium condensates simultaneously. The setup allows a broad range of research at low temperatures including optically detected magnetic resonance, studies of chemical processes of the active species produced by photolysis in solid matrices, and investigations of nanoclusters produced by laser ablation in superfluid helium.« less

Structural and optical properties of gold-incorporated diamond-like carbon thin films deposited by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Majeed, Shahbaz; Siraj, K.; Naseem, S.; Khan, Muhammad F.; Irshad, M.; Faiz, H.; Mahmood, A.

2017-07-01

Pure and gold-doped diamond-like carbon (Au-DLC) thin films are deposited at room temperature by using RF magnetron sputtering in an argon gas-filled chamber with a constant flow rate of 100 sccm and sputtering time of 30 min for all DLC thin films. Single-crystal silicon (1 0 0) substrates are used for the deposition of pristine and Au-DLC thin films. Graphite (99.99%) and gold (99.99%) are used as co-sputtering targets in the sputtering chamber. The optical properties and structure of Au-DLC thin films are studied with the variation of gold concentration from 1%-5%. Raman spectroscopy, atomic force microscopy (AFM), Vickers hardness measurement (VHM), and spectroscopic ellipsometry are used to analyze these thin films. Raman spectroscopy indicates increased graphitic behavior and reduction in the internal stresses of Au-DLC thin films as the function of increasing gold doping. AFM is used for surface topography, which shows that spherical-like particles are formed on the surface, which agglomerate and form larger clusters on the surface by increasing the gold content. Spectroscopy ellipsometry analysis elucidates that the refractive index and extinction coefficient are inversely related and the optical bandgap energy is decreased with increasing gold content. VHM shows that gold doping reduces the hardness of thin films, which is attributed to the increase in sp2-hybridization.

A review of production methods of carbon nanotube and graphene thin films for electrothermal applications

NASA Astrophysics Data System (ADS)

Janas, D.; Koziol, K. K.

2014-02-01

Electrothermal materials transform electric energy into heat due to the Joule effect. To date, resistive wires made of heavy metal alloys have primarily been used as the heat source in many appliances surrounding us. Recent discoveries in the field of carbon nanostructures revealed that they can offer a spectrum of advantages over the traditional materials. We review the production methods of thin films composed of carbon nanotubes or graphene and depict how they can be used as conductive coatings for electrothermal applications. We screen all reports from the field up to now and highlight the features of designed nanoheaters. A particular focus is placed on the analysis of general findings of how to tune their electrothermal properties, why carbon nanostructure devices operate the way they do and in what aspects they are superior to the currently available materials on the market.

Free-standing mesoporous carbon thin films with highly ordered pore architectures for nanodevices.

PubMed

Feng, Dan; Lv, Yingying; Wu, Zhangxiong; Dou, Yuqian; Han, Lu; Sun, Zhenkun; Xia, Yongyao; Zheng, Gengfeng; Zhao, Dongyuan

2011-09-28

We report for the first time the synthesis of free-standing mesoporous carbon films with highly ordered pore architecture by a simple coating-etching approach, which have an intact morphology with variable sizes as large as several square centimeters and a controllable thickness of 90 nm to ∼3 μm. The mesoporous carbon films were first synthesized by coating a resol precursors/Pluronic copolymer solution on a preoxidized silicon wafer and forming highly ordered polymeric mesostructures based on organic-organic self-assembly, followed by carbonizing at 600 °C and finally etching of the native oxide layer between the carbon film and the silicon substrate. The mesostructure of this free-standing carbon film is confirmed to be an ordered face-centered orthorhombic Fmmm structure, distorted from the (110) oriented body-centered cubic Im3̅m symmetry. The mesoporosity of the carbon films has been evaluated by nitrogen sorption, which shows a high specific BET surface area of 700 m(2)/g and large uniform mesopores of ∼4.3 nm. Both mesostructures and pore sizes can be tuned by changing the block copolymer templates or the ratio of resol to template. These free-standing mesoporous carbon films with cracking-free uniform morphology can be transferred or bent on different surfaces, especially with the aid of the soft polymer layer transfer technique, thus allowing for a variety of potential applications in electrochemistry and biomolecule separation. As a proof of concept, an electrochemical supercapacitor device directly made by the mesoporous carbon thin films shows a capacitance of 136 F/g at 0.5 A/g. Moreover, a nanofilter based on the carbon films has shown an excellent size-selective filtration of cytochrome c and bovine serum albumin.

On the Non-Metallicity of 2.2 nm Au 246 (SR) 80 Nanoclusters

DOE PAGES

Zhou, Meng; Zeng, Chenjie; Song, Yongbo; ...

2017-11-22

The transition from molecular to plasmonic behaviour in metal nanoparticles with increasing size remains a central question in nanoscience. Here, we report that the giant 246-gold-atom nanocluster (2.2 nm in gold core diameter) protected by 80 thiolate ligands is surprisingly non-metallic based on UV/Vis and femtosecond transient absorption spectroscopy as well as electrochemical measurements. Specifically, the Au246 nanocluster exhibits multiple excitonic peaks in transient absorption spectra and electron dynamics independent of the pump power, which are in contrast to the behaviour of metallic gold nanoparticles. Moreover, a prominent oscillatory feature with frequency of 0.5 THz can be observed in almostmore » all the probe wavelengths. The phase and amplitude analysis of the oscillation suggests that it arises from the wavepacket motion on the ground state potential energy surface, which also indicates the presence of a small band-gap and thus non-metallic or molecular-like behaviour.« less

High Performance Electrocatalytic Reaction of Hydrogen and Oxygen on Ruthenium Nanoclusters

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

Ye, Ruquan; Liu, Yuanyue; Peng, Zhiwei

2017-01-18

The development of catalytic materials for the hydrogen oxidation, hydrogen evolution, oxygen reduction or oxygen evolution reactions with high reaction rates and low overpotentials are key goals for the development of renewable energy. We report here Ru(0) nanoclusters supported on nitrogen-doped graphene as high-performance multifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), showing activities similar to that of commercial Pt/C in alkaline solution. For HER performance in alkaline media, sample Ru/NG-750 reaches 10 mA cm-2 at an overpotential of 8 mV with a Tafel slope of 30 mV dec-1. The high HER performance in alkalinemore » solution is advantageous because most catalysts for ORR and oxygen evolution reaction (OER) also prefer alkaline solution environment whereas degrade in acidic electrolytes. For ORR performance, Ru/NG effectively catalyzes the conversion of O2 into OH- via a 4e process at a current density comparable to that of Pt/C. The unusual catalytic activities of Ru(0) nanoclusters reported here are important discoveries for the advancement of renewable energy conversion reactions.« less

Foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for lithium–sulfur batteries

PubMed Central

Mao, Yiyin; Li, Gaoran; Guo, Yi; Li, Zhoupeng; Liang, Chengdu; Peng, Xinsheng; Lin, Zhan

2017-01-01

Lithium–sulfur batteries are promising technologies for powering flexible devices due to their high energy density, low cost and environmental friendliness, when the insulating nature, shuttle effect and volume expansion of sulfur electrodes are well addressed. Here, we report a strategy of using foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for binder-free advanced lithium–sulfur batteries through a facile confinement conversion. The carbon nanotubes interpenetrate through the metal-organic frameworks crystal and interweave the electrode into a stratified structure to provide both conductivity and structural integrity, while the highly porous metal-organic frameworks endow the electrode with strong sulfur confinement to achieve good cyclability. These hierarchical porous interpenetrated three-dimensional conductive networks with well confined S8 lead to high sulfur loading and utilization, as well as high volumetric energy density. PMID:28262801

Study on the electronic structure of Al12N12 and Al12P12 fullerene-like nano-clusters upon adsorption of CH3F and CH3Cl

NASA Astrophysics Data System (ADS)

Shokuhi Rad, A.; Zareyee, D.; Pouralijan Foukolaei, V.; Kamyab Moghadas, B.; Peyravi, M.

2016-11-01

We study the interaction of two mono-halomethanes (CH3F and CH3Cl) on Al12N12 and Al12P12 fullerene-like nano-clusters based on density functional theory (DFT). We search on fully optimised adsorbed systems by theoretical investigation considering binding energies, total density of states, natural bond orbital (NBO) charges, and molecular electrostatic potential. We found that the direction of electron transfer is from halomethane to nano-cluster for all systems, indicating p-type semiconductor property of the mentioned nano-clusters. The interaction energy of halomethanes on nano-clusters is evaluated with dispersion corrected (wB97XD) and non-corrected (B3LYP) methods in order to estimate the dispersion effects. The binding energies are found in order of Al12N12-CH3F > Al12N12-CH3Cl > Al12P12-CH3F > Al12P12-CH3Cl with the values of -102.7, -83.7, -64.2, and -48.9 kJ mol-1 based on wB97XD, respectively. We found significant changes in the location of HOMO as well as LUMO of nano-clusters upon adsorption of the above-mentioned molecules. As a result, we suggest the suitability of Al12N12 nano-cluster as a strong adsorbent for practical applications.

Sizing protein-templated gold nanoclusters by time resolved fluorescence anisotropy decay measurements

NASA Astrophysics Data System (ADS)

Soleilhac, Antonin; Bertorelle, Franck; Antoine, Rodolphe

2018-03-01

Protein-templated gold nanoclusters (AuNCs) are very attractive due to their unique fluorescence properties. A major problem however may arise due to protein structure changes upon the nucleation of an AuNC within the protein for any future use as in vivo probes, for instance. In this work, we propose a simple and reliable fluorescence based technique measuring the hydrodynamic size of protein-templated gold nanoclusters. This technique uses the relation between the time resolved fluorescence anisotropy decay and the hydrodynamic volume, through the rotational correlation time. We determine the molecular size of protein-directed AuNCs, with protein templates of increasing sizes, e.g. insulin, lysozyme, and bovine serum albumin (BSA). The comparison of sizes obtained by other techniques (e.g. dynamic light scattering and small-angle X-ray scattering) between bare and gold clusters containing proteins allows us to address the volume changes induced either by conformational changes (for BSA) or the formation of protein dimers (for insulin and lysozyme) during cluster formation and incorporation.

Sizing protein-templated gold nanoclusters by time resolved fluorescence anisotropy decay measurements.

PubMed

Soleilhac, Antonin; Bertorelle, Franck; Antoine, Rodolphe

2018-03-15

Protein-templated gold nanoclusters (AuNCs) are very attractive due to their unique fluorescence properties. A major problem however may arise due to protein structure changes upon the nucleation of an AuNC within the protein for any future use as in vivo probes, for instance. In this work, we propose a simple and reliable fluorescence based technique measuring the hydrodynamic size of protein-templated gold nanoclusters. This technique uses the relation between the time resolved fluorescence anisotropy decay and the hydrodynamic volume, through the rotational correlation time. We determine the molecular size of protein-directed AuNCs, with protein templates of increasing sizes, e.g. insulin, lysozyme, and bovine serum albumin (BSA). The comparison of sizes obtained by other techniques (e.g. dynamic light scattering and small-angle X-ray scattering) between bare and gold clusters containing proteins allows us to address the volume changes induced either by conformational changes (for BSA) or the formation of protein dimers (for insulin and lysozyme) during cluster formation and incorporation. Copyright © 2017 Elsevier B.V. All rights reserved.

Domain growth of carbon nanotubes assisted by dewetting of thin catalyst precursor films

NASA Astrophysics Data System (ADS)

Srivastava, Alok Kumar; Sachan, Priyanka; Samanta, Chandan; Mukhopadhyay, Kingsuk; Sharma, Ashutosh

2014-01-01

We explore self-organized dewetting of ultrathin films of a novel metal complex as a one step surface patterning method to create nanoislands of iron, using which spatially separated carbon nanostructures were synthesized. Dewetting of ultrathin metal complex films was induced by two different methods: liquid solvent exposure and thermal annealing to engender surface patterning. For thermal dewetting, thin films of the iron oleate complex were dewetted at high temperature. In the case of liquid solvent assisted dewetting, the metal complex, mixed with a sacrificial polymer (polystyrene) was spin coated as thin films (<40 nm) and then dewetted under an optimal solution mixture consisting of methyl ethyl ketone, acetone and water. The carrier polymer was then selectively removed to produce the iron metal islands. These metal islands were used for selective growth of discrete patches of multiwall CNTs and CNFs by a chemical vapor deposition (CVD) process. Solvent induced dewetting showed clear advantages over thermal dewetting owing to reduced size of catalyst domains formed by dewetting, an improved control over CNT growth as well as in its ability to immobilize the seed particles. The generic solution mediated dewetting and pattern generation in thin films of various catalytic precursors can thus be a powerful method for selective domain growth of a variety of functional nanomaterials.

Investigating Catalyst–Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo 3 S 13 ] 2– Nanoclusters

DOE PAGES

Hellstern, Thomas R.; Kibsgaard, Jakob; Tsai, Charlie; ...

2017-09-22

Molybdenum sulfides have been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo 3S 13] 2- nanocluster catalyst contains a structural motif that resembles the active site of MoS 2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo 3S 13] 2- catalysts through catalyst-support interactions. We synthesize [Mo 3S 13] 2- on gold, silver, glassy carbon, and copper supports to demonstrate the ability tomore » tune the hydrogen binding energy of [Mo 3S 13] 2- using catalyst-support electronic interactions and optimize HER activity.« less

Investigating Catalyst–Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo 3 S 13 ] 2– Nanoclusters

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

Hellstern, Thomas R.; Kibsgaard, Jakob; Tsai, Charlie

Molybdenum sulfides have been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo 3S 13] 2- nanocluster catalyst contains a structural motif that resembles the active site of MoS 2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo 3S 13] 2- catalysts through catalyst-support interactions. We synthesize [Mo 3S 13] 2- on gold, silver, glassy carbon, and copper supports to demonstrate the ability tomore » tune the hydrogen binding energy of [Mo 3S 13] 2- using catalyst-support electronic interactions and optimize HER activity.« less

Effect of diamond-like carbon thin film coated acrylic resin on candida albicans biofilm formation.

PubMed

Queiroz, José Renato Cavalcanti; Fissmer, Sara Fernanda; Koga-Ito, Cristiane Yumi; Salvia, Ana C R D; Massi, Marcos; Sobrinho, Argermiro Soares da Silva; Júnior, Lafayette Nogueira

2013-08-01

The purpose of this study was to evaluate the effect of diamond-like carbon thin films doped and undoped with silver nanoparticles coating poly(methyl methacrylate) (PMMA) on Candida albicans biofilm formation. The control of biofilm formation is important to prevent oral diseases in denture users. Forty-five PMMA disks were obtained, finished, cleaned in an ultrasonic bath, and divided into three groups: Gc, no surface coating (control group); Gdlc, coated with diamond-like carbon film; and Gag, coated with diamond-like carbon film doped with silver nanoparticles. The films were deposited using a reactive magnetron sputtering system (physical vapor deposition process). The specimens were characterized by optical profilometry, atomic force microscopy, and Rutherford backscattering spectroscopy analyses that determined differences in chemical composition and morphological structure. Following sterilization of the specimens by γ-ray irradiation, C. albicans (ATCC 18804) biofilms were formed by immersion in 2 ml of Sabouraud dextrose broth inoculated with a standardized fungal suspension. After 24 hours, the number of colony forming units (cfu) per specimen was counted. Data concerning biofilm formation were analyzed using ANOVA and the Tukey test (p < 0.05). C. albicans biofilm formation was significantly influenced by the films (p < 0.00001), reducing the number of cfu, while not affecting the roughness parameters (p > 0.05). The Tukey test showed no significant difference between Gdlc and Gag. Films deposited were extremely thin (∼50 nm). The silver particles presented a diameter between 60 and 120 nm and regular distribution throughout the film surface (to Gag). Diamond-like carbon films, doped or undoped with silver nanoparticles, coating the base of PMMA-based dentures could be an alternative procedure for preventing candidosis in denture users. © 2013 by the American College of Prosthodontists.

A comprehensive study of catalytic, morphological and electronic properties of ligand-protected gold nanoclusters using XPS, STM, XAFS, and TPD techniques

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

Wu, Qiyuan; Cen, Jiajie; Zhao, Yue

Ultra-small gold nanoclusters were synthesized via a ligand exchange method and deposited onto different TiO2 supports to study their properties. STM imaging revealed that the as-synthesized gold nanoclusters had 2-D morphology consisting of monolayers of gold atoms. In conclusion, subsequent XPS, XAFS, and CO oxidation TPD results indicated that heat treatments of gold clusters at different temperatures significantly altered their electronic and catalytic properties due to ligand deprotection and cluster agglomeration.

A comprehensive study of catalytic, morphological and electronic properties of ligand-protected gold nanoclusters using XPS, STM, XAFS, and TPD techniques

DOE PAGES

Wu, Qiyuan; Cen, Jiajie; Zhao, Yue; ...

2017-12-08

Ultra-small gold nanoclusters were synthesized via a ligand exchange method and deposited onto different TiO2 supports to study their properties. STM imaging revealed that the as-synthesized gold nanoclusters had 2-D morphology consisting of monolayers of gold atoms. In conclusion, subsequent XPS, XAFS, and CO oxidation TPD results indicated that heat treatments of gold clusters at different temperatures significantly altered their electronic and catalytic properties due to ligand deprotection and cluster agglomeration.

Thin-film optical initiator

DOEpatents

Erickson, Kenneth L.

2001-01-01

A thin-film optical initiator having an inert, transparent substrate, a reactive thin film, which can be either an explosive or a pyrotechnic, and a reflective thin film. The resultant thin-film optical initiator system also comprises a fiber-optic cable connected to a low-energy laser source, an output charge, and an initiator housing. The reactive thin film, which may contain very thin embedded layers or be a co-deposit of a light-absorbing material such as carbon, absorbs the incident laser light, is volumetrically heated, and explodes against the output charge, imparting about 5 to 20 times more energy than in the incident laser pulse.

Organic Inorganic Hybrid Solar Cell Efficiency Improvement By Employing Au Nanocluster

DTIC Science & Technology

2015-06-14

ABSTRACT 16. SECURITY CLASSIFICATION OF: Poly( 3,4-ethyllenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS), a P-type organic polymer is frequently...Addition of small volume percentage of organic additives such as dimethyl sulfoxide (DMSO) has a positive effect on the conductivity of this polymer . In...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 hybrid solar cell, tunable conductivity, organic polymer , heterojunction, nanocluster

Polyacrylonitrile block copolymers for the preparation of a thin carbon coating around TiO2 nanorods for advanced lithium-ion batteries.

PubMed

Oschmann, Bernd; Bresser, Dominic; Tahir, Muhammad Nawaz; Fischer, Karl; Tremel, Wolfgang; Passerini, Stefano; Zentel, Rudolf

2013-11-01

Herein, a new method for the realization of a thin and homogenous carbonaceous particle coating, made by carbonizing RAFT polymerization derived block copolymers anchored on anatase TiO2 nanorods, is presented. These block copolymers consist of a short anchor block (based on dopamine) and a long, easily graphitizable block of polyacrylonitrile. The grafting of such block copolymers to TiO2 nanorods creates a polymer shell, which can be visualized by atomic force microscopy (AFM). Thermal treatment at 700 °C converts the polyacrylonitrile block to partially graphitic structures (as determined by Raman spectroscopy), establishing a thin carbon coating (as determined by transmission electron microscopy, TEM, analysis). The carbon-coated TiO2 nanorods show improved electrochemical performance in terms of achievable specific capacity and, particularly, long-term cycling stability by reducing the average capacity fading per cycle from 0.252 mAh g(-1) to only 0.075 mAh g(-1) . © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical sensing employingpH sensitive emeraldine base thin film for carbon dioxide detection

NASA Astrophysics Data System (ADS)

Irimia-Vladu, Mihai

Respiration, or CO2 evolution, is a universal indicator for all the biological activities. Among many potential applications, the measurement of CO2 evolution has been found to be a rapid and nondestructive means for examining microbial contamination of food. The sensor developed in this work consists of a thin emeraldine base-polyaniline (EB-PAni) film. In the first half of the project the effect of carbon dioxide over the conductivity of a composite film of emeraldine base polyaniline and poly(vinyl alcohol) in N-methyl pyrrolidone (NMP) respectively was tested. Argon gas or mixture of argon and 5% CO2 were circulated through the glass cell containing the polymer film deposited on interdigitated electrode and exposed to specific humidity levels fixed by aqueous supersaturated salt solutions. In the second half of the project, a thin emeraldine base film in NMP was directly deposited on interdigitated electrode and the respective sensor inserted in water. Carbonic acid solutions of various pHs were generated by bubbling specific mixtures of carbon dioxide and argon. Conductivity measurements were performed by impedance spectroscopy throughout the project. The sensing mechanism is based on intermediate stages of the transformation of the emeraldine base polyaniline to a conductive salt type (ES-PAni). This EB-ES transformation is the consequence of the exposure of EB-PAni to a protonic acid and is accompanied by a change in the conductivity of the polymer film. Carbonic acid, unfortunately, is a very weak acid and is unable to induce a conductivity change, but the intermediate steps that predetermine this transformation are detected by impedance spectroscopy even when the overall conductivity of the film is unchanged. The composite thin film developed in the first part of the project showed poor sensing characteristics: limited dynamic range, drift, instability and slow time response. However, the sensor design employed in the second half of this work, coupled with

Hydrogen in thin Pd-based layers deposited on reticulated vitreous carbon-A new system for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Łukaszewski, M.; Żurowski, A.; Czerwiński, A.

Reticulated vitreous carbon (RVC) has been used as a matrix for electrodeposition of thin layers of Pd and Pd-rich Pd-Rh alloys. It was found that RVC substrate does not affect qualitatively hydrogen absorption behavior of Pd-based deposits. Similarly to thin Pd or Pd alloy layers deposited on Au wires, the α-β phase transition controls the overall rate of hydrogen absorption and desorption into/from Pd-based/RVC electrodes. The possibility of the application of these materials as phase charging-discharging systems was investigated. The values of specific pseudocapacitance, specific power and specific energy were comparable with those for supercapacitors utilizing various redox reactions.

Shell effect on the electron and hole reorganization energy of core-shell II-VI nanoclusters

NASA Astrophysics Data System (ADS)

Cui, Xianhui; Wang, Xinqin; Yang, Fang; Cui, Yingqi; Yang, Mingli

2017-09-01

Density functional theory calculations were performed to study the effect of shell encapsulation on the geometrical and electronic properties of pure and hybrid core-shell CdSe nanoclusters. The CdSe cores are distorted by the shells, and the shells exhibit distinct surface activity from the cores, which leads to remarkable changes in their electron transition behaviors. Although the electron and hole reorganization energies, which are related to the formation and recombination of electron-hole pairs, vary in a complicated way, their itemized contributions, potentials of electron extraction, ionization and affinity, and hole extraction (HEP), are dependent on the cluster size, shell composition and/or solvent. Our calculations suggest that the behaviors of charge carriers, free electrons and holes, in the semiconductor core-shell nanoclusters can be modulated by selecting appropriate cluster size and controlling the chemical composition of the shells.

Anomalous nanoclusters, anisotropy, and electronic nematicity in the doped manganite L a 1 / 3 C a 2 / 3 Mn O 3

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

Tao, J.; Sun, K.; Tranquada, J. M.

In doped manganites, a superlattice (SL) modulation associated with charge/orbital ordering is accepted as a key component in understanding many intriguing properties. It has been reported that the SL modulation always appears on the a axis of the crystals. Here in this study, by using multiple transmission electron microscopic techniques, we observe a type of anomalous nanocluster in which the SL modulation appears on the c axis of La 1/3Ca 2/3MnO 3. By correlating the thermal evolution of the anomalous nanoclusters to other property measurements, we suggest that strain is responsible for the formation of the anomalous nanoclusters. The phasemore » separation and phase transition scenario in La 1/3Ca 2/3MnO 3 are also described using electronic-liquid-crystal (ELC) phases. Lastly, an ELC phase diagram in La 1/3Ca 2/3MnO 3 is constructed as a function of temperature based on our observations.« less

Anomalous nanoclusters, anisotropy, and electronic nematicity in the doped manganite L a 1 / 3 C a 2 / 3 Mn O 3

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

Tao, J.; Sun, K.; Tranquada, J. M.

2017-06-07

In doped manganites, a superlattice (SL) modulation associated with charge/orbital ordering is accepted as a key component in understanding many intriguing properties. It has been reported that the SL modulation always appears on the a axis of the crystals. Here in this study, by using multiple transmission electron microscopic techniques, we observe a type of anomalous nanocluster in which the SL modulation appears on the c axis of La 1/3Ca 2/3MnO 3. By correlating the thermal evolution of the anomalous nanoclusters to other property measurements, we suggest that strain is responsible for the formation of the anomalous nanoclusters. The phasemore » separation and phase transition scenario in La 1/3Ca 2/3MnO 3 are also described using electronic-liquid-crystal (ELC) phases. Lastly, an ELC phase diagram in La 1/3Ca 2/3MnO 3 is constructed as a function of temperature based on our observations.« less

High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems

DTIC Science & Technology

2013-12-01

pr.ac Semenova 1a Russia EOARD ISTC 09-7006/P-4084p Report Date: December 2013 Final Report from 01 October 2010 to 30 September 2013...CONTRACT NUMBER ISTC PPA 4084p 5b. GRANT NUMBER ISTC 09-7006 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S...discussed in the conventional theory. High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems ISTC Project No. 4084p

Plasmon tsunamis on metallic nanoclusters.

PubMed

Lucas, A A; Sunjic, M

2012-03-14

A model is constructed to describe inelastic scattering events accompanying electron capture by a highly charged ion flying by a metallic nanosphere. The electronic energy liberated by an electron leaving the Fermi level of the metal and dropping into a deep Rydberg state of the ion is used to increase the ion kinetic energy and, simultaneously, to excite multiple surface plasmons around the positively charged hole left behind on the metal sphere. This tsunami-like phenomenon manifests itself as periodic oscillations in the kinetic energy gain spectrum of the ion. The theory developed here extends our previous treatment (Lucas et al 2011 New J. Phys. 13 013034) of the Ar(q+)/C(60) charge exchange system. We provide an analysis of how the individual multipolar surface plasmons of the metallic sphere contribute to the formation of the oscillatory gain spectrum. Gain spectra showing characteristic, tsunami-like oscillations are simulated for Ar(15+) ions capturing one electron in distant collisions with Al and Na nanoclusters.

Surface modification of TiO2 with metal oxide nanoclusters: a route to composite photocatalytic materials.

PubMed

Nolan, Michael

2011-08-14

Density functional theory simulations show that modifying rutile TiO(2) with metal oxide nanoclusters produces composite materials with potential visible light photocatalytic activity. This journal is © The Royal Society of Chemistry 2011

In vivo self-bio-imaging of tumors through in situ biosynthesized fluorescent gold nanoclusters

NASA Astrophysics Data System (ADS)

Wang, Jianling; Zhang, Gen; Li, Qiwei; Jiang, Hui; Liu, Chongyang; Amatore, Christian; Wang, Xuemei

2013-01-01

Fluorescence imaging in vivo allows non-invasive tumor diagnostic thus permitting a direct monitoring of cancer therapies progresses. It is established herein that fluorescent gold nanoclusters are spontaneously biosynthesized by cancerous cell (i.e., HepG2, human hepatocarcinoma cell line; K562, leukemia cell line) incubated with micromolar chloroauric acid solutions, a biocompatible molecular Au(III) species. Gold nanoparticles form by Au(III) reduction inside cells cytoplasms and ultimately concentrate around their nucleoli, thus affording precise cell imaging. Importantly, this does not occur in non-cancerous cells, as evidenced with human embryo liver cells (L02) used as controls. This dichotomy is exploited for a new strategy for in vivo self-bio-imaging of tumors. Subcutaneous injections of millimolar chloroauric acid solution near xenograft tumors of the nude mouse model of hepatocellular carcinoma or chronic myeloid leukemia led to efficient biosynthesis of fluorescent gold nanoclusters without significant dissemination to the surrounding normal tissues, hence allowing specific fluorescent self-bio-marking of the tumors.

Effect of (Ag, Sn) Doping on the Structure and Optical Properties of Au Nanocluster

NASA Astrophysics Data System (ADS)

Balu, Radhakrishnan; Karna, Shashi

2014-03-01

Noble metal nanoclusters (NCs) consisting of a few to 35 atoms in size in the sub 2 nm range dimension are considered to be nontoxic as opposed to nanoparticles that are cytotoxic. Also, due to the quantum confinement of electrons, these NCs exhibit atom-like energy spectrum and display fluorescent properties useful in a wide range of applications, including medical diagnosis. The unique features of NCs such as size-tunable optical properties, intense fluorescence in the visible, and biocompatibility have stimulated an active area of investigation of noble metal NCs comprised of Au, Ag, Cu, and Pt. Furthermore, the electronic properties of nanoclusters can be modified by combining them with other elements. In this study, we consider the space-filled configuration of Au32 NC and investigate the effects of Ag and Sn atom incorporation on geometry and electronic spectrum. Our study suggests that Ag and Sn doping of Au32 NC red-shifts the absorption maximum and also reduces the oscillator strength.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker.

PubMed

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Marty, Jean Louis; Hayat, Akhtar

2016-10-06

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett- Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker

PubMed Central

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Louis Marty, Jean; Hayat, Akhtar

2016-01-01

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications. PMID:27782067

Thin Films of Reduced Hafnium Oxide with Excess Carbon for High-Temperature Oxidation Protection

DTIC Science & Technology

2010-02-01

Cho, N. V. Nguyen, C. A. Richter, J. R. Ehrstein, B . H. Lee, and J. C. Lee, "Spectroscopic Ellipsometry Characterization of High- k Dielectric Hf02...34 Canadian Journal of Chemistry, 61 850-55 (1983). I6D. B . Chrisey and G. K . Hubler (Eds.), "Pulsed Laser Deposition of Thin Films." John Wiley...smaller than b rim. It was shown that high carbon content in the films inhibits crystaliization of HtO( at temperatures at least up to 333 C. Study ot

Melting of Cu nanoclusters by molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Wang, Li; Zhang, Yanning; Bian, Xiufang; Chen, Ying

2003-04-01

We present a detailed molecular dynamics study of the melting of copper nanoclusters with up to 8628 atoms within the framework of the embedded-atom method. The finding indicates that there exists an intermediate nanocrystal regime above 456 atoms. The linear relation between the cluster size and its thermodynamics properties is obeyed in this regime. Melting first occurs at the surface of the clusters, leading to Tm, N= Tm,Bulk- αN-1/3, dropping from Tm,Bulk=1360 K to Tm,456=990 K. In addition, the size, surface energy as well as the root mean square displacement (RMSD) of the clusters in the intermediate regime have been investigated.

Optical properties and electronic energy relaxation of metallic Au144(SR)60 nanoclusters.

PubMed

Yi, Chongyue; Tofanelli, Marcus A; Ackerson, Christopher J; Knappenberger, Kenneth L

2013-12-04

Electronic energy relaxation of Au144(SR)60(q) ligand-protected nanoclusters, where SR = SC6H13 and q = -1, 0, +1, and +2, was examined using femtosecond time-resolved transient absorption spectroscopy. The observed differential transient spectra contained three distinct components: (1) transient bleaches at 525 and 600 nm, (2) broad visible excited-state absorption (ESA), and (3) stimulated emission (SE) at 670 nm. The bleach recovery kinetics depended upon the excitation pulse energy and were thus attributed to electron-phonon coupling typical of metallic nanostructures. The prominent bleach at 525 nm was assigned to a core-localized plasmon resonance (CLPR). ESA decay kinetics were oxidation-state dependent and could be described using a metal-sphere charging model. The dynamics, emission energy, and intensity of the SE peak exhibited dielectric-dependent responses indicative of Superatom charge transfer states. On the basis of these data, the Au144(SR)60 system is the smallest-known nanocluster to exhibit quantifiable electron dynamics and optical properties characteristic of metals.

Theoretical Insights into Direct Methane to Methanol Conversion over Supported Dicopper Oxo Nanoclusters

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

Doan, Hieu A.; Li, Zhanyong; Farha, Omar K.

In this study, the prospect of using copper oxide nanoclusters grown by atomic layer deposition on a porphyrin support for selective oxidation of methane to methanol was examined by means of density functional theory (DFT) calculations. Ab initio thermodynamic analysis indicates that an active site in the form of Cu(μ-O)Cu can be stabilized by activation in O2 at 465K. Furthermore, a moderate methane activation energy barrier (Ea=54kJ/mol) is predicted, and the hydrogen abstraction activity of the active site could be attributed to the radical character of the bridging oxygen. Methanol extraction in this system is limited by a thermodynamic barriermore » to desorption of ΔG=57kJ/mol at 473K; however, desorption can be facilitated by the addition of water in a “stepped conversion” process. Overall, our results indicate similar activity between porphyrin-supported copper oxide nanoclusters and existing Cu-exchanged zeolites and provide a computational proof-of-concept for utilizing functionalized organic linkers in metal-organic frameworks (MOFs) for selective oxidation of methane to methanol.« less

Theoretical Insights into Direct Methane to Methanol Conversion over Supported Dicopper Oxo Nanoclusters

DOE PAGES

Doan, Hieu A.; Li, Zhanyong; Farha, Omar K.; ...

2018-04-08

In this study, the prospect of using copper oxide nanoclusters grown by atomic layer deposition on a porphyrin support for selective oxidation of methane to methanol was examined by means of density functional theory (DFT) calculations. Ab initio thermodynamic analysis indicates that an active site in the form of Cu(μ-O)Cu can be stabilized by activation in O2 at 465K. Furthermore, a moderate methane activation energy barrier (Ea=54kJ/mol) is predicted, and the hydrogen abstraction activity of the active site could be attributed to the radical character of the bridging oxygen. Methanol extraction in this system is limited by a thermodynamic barriermore » to desorption of ΔG=57kJ/mol at 473K; however, desorption can be facilitated by the addition of water in a “stepped conversion” process. Overall, our results indicate similar activity between porphyrin-supported copper oxide nanoclusters and existing Cu-exchanged zeolites and provide a computational proof-of-concept for utilizing functionalized organic linkers in metal-organic frameworks (MOFs) for selective oxidation of methane to methanol.« less

Crystal structure of Au25(SePh)18 nanoclusters and insights into their electronic, optical and catalytic properties

NASA Astrophysics Data System (ADS)

Song, Yongbo; Zhong, Juan; Yang, Sha; Wang, Shuxin; Cao, Tiantian; Zhang, Jun; Li, Peng; Hu, Daqiao; Pei, Yong; Zhu, Manzhou

2014-10-01

The crystal structure of selenolate-capped Au25(SePh)18- nanoclusters has been unambiguously determined for the first time, and provides a solid basis for a deeper understanding of the structure-property relationships. The selenolate-capped Au25 cluster shows noticeable differences from the previously reported Au25(SCH2CH2Ph)18- counterpart, albeit both share the icosahedral Au13 core and semi-ring Au2(SeR)3 or Au2(SR)3 motifs. Distinct differences in the electronic structure and optical, catalytic and electrochemical properties are revealed by the coupling experiments with density functional theory (TD-DFT) calculations. Overall, the successful determination of the Au25(SePh)18- structure removes any ambiguity about its structure, and comparison with the thiolated Au25 counterpart helps us to further understand how the ligands affect the properties of the nanocluster.The crystal structure of selenolate-capped Au25(SePh)18- nanoclusters has been unambiguously determined for the first time, and provides a solid basis for a deeper understanding of the structure-property relationships. The selenolate-capped Au25 cluster shows noticeable differences from the previously reported Au25(SCH2CH2Ph)18- counterpart, albeit both share the icosahedral Au13 core and semi-ring Au2(SeR)3 or Au2(SR)3 motifs. Distinct differences in the electronic structure and optical, catalytic and electrochemical properties are revealed by the coupling experiments with density functional theory (TD-DFT) calculations. Overall, the successful determination of the Au25(SePh)18- structure removes any ambiguity about its structure, and comparison with the thiolated Au25 counterpart helps us to further understand how the ligands affect the properties of the nanocluster. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04631e

One-step aqueous synthesis of fluorescent copper nanoclusters by direct metal reduction

NASA Astrophysics Data System (ADS)

Fernández-Ujados, Mónica; Trapiella-Alfonso, Laura; Costa-Fernández, José M.; Pereiro, Rosario; Sanz-Medel, Alfredo

2013-12-01

A one-step aqueous synthesis of highly fluorescent water-soluble copper nanoclusters (CuNCs) is here described, based on direct reduction of the metal precursor with NaBH4 in the presence of bidentate ligands (made of lipoic acid anchoring groups, appended with a poly(ethylene glycol) short chain). A complete optical and structural characterization was carried out: the optical emission was centred at 416 nm, with a luminescence quantum yield in water of 3.6% (the highest one reported so far in water for this kind of nanocluster). The structural characterization reveals a homogeneous size distribution (of 2.5 nm diameter) with spherical shape. The CuNCs obtained offer long-term stability (the luminescence emission remained unaltered after more than two months) under a broad range of chemical conditions (e.g. stored at pH 3-12 or even in a high ionic strength medium such as 1 M NaCl) and high photostability, keeping their fluorescence emission intact after more than 2 h of daylight and UV-light exposition. All those advantageous features warrant synthesized CuNCs being promising fluorescent nanoprobes for further developments including (bio)applications.

Thin-film versus slurry-phase carbonation of steel slag: CO₂ uptake and effects on mineralogy.

PubMed

Baciocchi, R; Costa, G; Di Gianfilippo, M; Polettini, A; Pomi, R; Stramazzo, A

2015-01-01

The results of direct aqueous accelerated carbonation of three types of steel manufacturing residues, including an electric arc furnace (EAF) slag and two basic oxygen furnace (BOF) slags, are reported. Batch accelerated carbonation tests were conducted at different temperatures and CO2 pressures applying the thin-film route (liquid to solid, L/S, ratio=0.3L/kg) or the slurry-phase route (L/S ratio=5L/kg). The CO2 uptake strongly depended on both the slag characteristics and the process route; maximum yields of 280 (EAF), 325 (BOF1) and 403 (BOF2) gCO2/kg slag were achieved in slurry phase at T=100°C and pCO2=10 bar. Differently from previous studies, additional carbonates (other than Ca-based phases) were retrieved in the carbonated BOF slags, indicating that also Mg-, Fe- and Mn-containing phases partially reacted with CO2 under the tested conditions. The results hence show that the effects of accelerated carbonation in terms of CO2 uptake capacity, yield of mineral conversion into carbonates and mineralogy of the treated product, strongly rely on several factors. These include, above all, the mineralogy of the original material and the operating conditions adopted, which thus need specific case-by-case optimization to maximize the CO2 sequestration yield. Copyright © 2014 Elsevier B.V. All rights reserved.

Size, shape, and compositional effects on the order-disorder phase transitions in Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys.

PubMed

Kaatz, Forrest H; Bultheel, Adhemar

2018-08-24

Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys are currently being investigated world-wide by many researchers for their interesting catalytic and nanophase properties. The low temperature behavior of the phase diagrams is not well understood for alloys with nanometer sizes and shapes. We consider two models for low temperature ordering in the phase diagrams of Au-Cu and Pt-M nanocluster alloys. These models are valid for sizes ∼5 nm and approach bulk values for sizes ∼20 nm. We study the phase transitions in nanoclusters with cubic, octahedral, and cuboctahedral shapes, covering the compositions of interest. These models are based on studying the melting temperatures in nanoclusters using the regular solution, mixing model for alloys. From our data, experiments on nanocubes about 5 nm in size, of stoichiometric AuCu and PtM composition, could help differentiate between the models. Dispersion data shows that for the three shapes considered, octahedra have the highest percentage of surface atoms for the same relative diameter. We summarize the effects of structural ordering on the catalytic activity and suggest a method to avoid sintering during annealing of Pt-M alloys.

Plasma CVD of hydrogenated boron-carbon thin films from triethylboron

NASA Astrophysics Data System (ADS)

Imam, Mewlude; Höglund, Carina; Schmidt, Susann; Hall-Wilton, Richard; Birch, Jens; Pedersen, Henrik

2018-01-01

Low-temperature chemical vapor deposition (CVD) of B—C thin films is of importance for neutron voltaics and semiconductor technology. The highly reactive trialkylboranes, with alkyl groups of 1-4 carbon atoms, are a class of precursors that have been less explored for low-temperature CVD of B—C films. Herein, we demonstrate plasma CVD of B—C thin films using triethylboron (TEB) as a single source precursor in an Ar plasma. We show that the film density and B/C ratio increases with increasing plasma power, reaching a density of 2.20 g/cm3 and B/C = 1.7. This is attributed to a more intense energetic bombardment during deposition and more complete dissociation of the TEB molecule in the plasma at higher plasma power. The hydrogen content in the films ranges between 14 and 20 at. %. Optical emission spectroscopy of the plasma shows that BH, CH, C2, and H are the optically active plasma species from TEB. We suggest a plasma chemical model based on β-hydrogen elimination of C2H4 to form BH3, in which BH3 and C2H4 are then dehydrogenated to form BH and C2H2. Furthermore, C2H2 decomposes in the plasma to produce C2 and CH, which together with BH and possibly BH3-x(C2H5)x are the film forming species.

Stabilizing Protein Effects on the Pressure Sensitivity of Fluorescent Gold Nanoclusters

DTIC Science & Technology

2016-01-13

excess Au salt. The purified sample was lyophilized and resuspended at a concentration of 10 mg/mL in ultrapure water . BSA ( PDB :3v03) 100 % α...effect of scaffold protein secondary structure on the pressure response of protein-stabilized gold nanoclusters (P:NCs). These studies were...demonstrate that the pressure response of P:NCs is indeed dependent on the secondary structure of the protein. Proteins with high beta sheet content

Crystallization-induced emission enhancement: A novel fluorescent Au-Ag bimetallic nanocluster with precise atomic structure

PubMed Central

Chen, Tao; Yang, Sha; Chai, Jinsong; Song, Yongbo; Fan, Jiqiang; Rao, Bo; Sheng, Hongting; Yu, Haizhu; Zhu, Manzhou

2017-01-01

We report the first noble metal nanocluster with a formula of Au4Ag13(DPPM)3(SR)9 exhibiting crystallization-induced emission enhancement (CIEE), where DPPM denotes bis(diphenylphosphino)methane and HSR denotes 2,5-dimethylbenzenethiol. The precise atomic structure is determined by x-ray crystallography. The crystalline state of Au4Ag13 shows strong luminescence at 695 nm, in striking contrast to the weak emission of the amorphous state and hardly any emission in solution phase. The structural analysis and the density functional theory calculations imply that the compact C–H⋯π interactions significantly restrict the intramolecular rotations and vibrations and thus considerably enhance the radiative transitions in the crystalline state. Because the noncovalent interactions can be easily modulated via varying the chemical environments, the CIEE phenomenon might represent a general strategy to amplify the fluorescence from weakly (or even non-) emissive nanoclusters. PMID:28835926

Ejection of nanoclusters from gold nanoislet layers by 38 keV Au ions in the elastic stopping mode.

PubMed

Baranov, I A; Della-Negra, S; Domaratsky, V P; Chemezov, A V; Kirillov, S N; Novikov, A C; Obnorsky, V V; Pautrat, M; Urbassek, H M; Wien, K; Yarmiychuk, S V; Zhurkin, E E

2009-07-01

Total absolute yields of the ejected gold were obtained regardless of the type of the particles are--atoms, clusters, nanoclusters,--as well as absolute yields of gold nanoclusters, from nanoislet gold targets under bombardment by monoatomic gold ions at 45 degrees to the target surface with the energy 38 keV, i.e., in the "purely" elastic stopping mode -6 keV/nm up to the fluence of 4 x 10(12) cm2. Three targets had gold nanoislets on the substrate surface: 2-12 nm; -18 nm; -35 nm, the most probable sizes being 7.1; 9.4; 17.5 nm respectively. The part of the surface area covered with gold was known. Total transfer of gold was determined by means of the neutron-activation analysis and decreased from 450 to 20 at/ion. The number of the ejected gold nanoclusters was determined using TEM and decreased from approximately 0.06 to < 0.01 per one 38 keV Au ion with the increase of the most probable sizes of the nanoislets on the target from 7.1 to 17.5 nm. The yields appeared to be surprisingly high, which is of scientific and practical importance. Tentative estimations were made using molecular dynamics simulations.

Tuning thin-film electrolyte for lithium battery by grafting cyclic carbonate and combed poly(ethylene oxide) on polysiloxane.

PubMed

Li, Jie; Lin, Yue; Yao, Hehua; Yuan, Changfu; Liu, Jin

2014-07-01

A tunable polysiloxane thin-film electrolyte for all-solid-state lithium-ion batteries was developed. The polysiloxane was synthesized by hydrosilylation of polymethylhydrosiloxane with cyclic [(allyloxy)methyl]ethylene ester carbonic acid and vinyl tris(2-methoxyethoxy)silane. (1) H NMR spectroscopy and gel-permeation chromatography demonstrated that the bifunctional groups of the cyclic propylene carbonate (PC) and combed poly(ethylene oxide) (PEO) were well grafted on the polysiloxane. At PC/PEO=6:4, the polysiloxane-based electrolyte had an ionic conductivity of 1.55 × 10(-4) and 1.50 × 10(-3)  S cm(-1) at 25 and 100 °C, respectively. The LiFePO4 /Li batteries fabricated with the thin-film electrolyte presented excellent cycling performance in the temperature range from 25 to 100 °C with an initial discharge capacity at a rate of 1 C of 88.2 and 140 mA h g(-1) at 25 and 100 °C, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-probe versus van der Pauw method in studying the piezoresistivity of single-wall carbon nanotube thin films

NASA Astrophysics Data System (ADS)

Yao, Yanbo; Duan, Xiaoshuang; Luo, Jiangjiang; Liu, Tao

2017-11-01

The use of the van der Pauw (VDP) method for characterizing and evaluating the piezoresistive behavior of carbon nanomaterial enabled piezoresistive sensors have not been systematically studied. By using single-wall carbon nanotube (SWCNT) thin films as a model system, herein we report a coupled electrical-mechanical experimental study in conjunction with a multiphysics finite element simulation as well as an analytic analysis to compare the two-probe and VDP testing configuration in evaluating the piezoresistive behavior of carbon nanomaterial enabled piezoresistive sensors. The key features regarding the sample aspect ratio dependent piezoresistive sensitivity or gauge factor were identified for the VDP testing configuration. It was found that the VDP test configuration offers consistently higher piezoresistive sensitivity than the two-probe testing method.

Thin randomly aligned hierarchical carbon nanotube arrays as ultrablack metamaterials

NASA Astrophysics Data System (ADS)

De Nicola, Francesco; Hines, Peter; De Crescenzi, Maurizio; Motta, Nunzio

2017-07-01

Ultrablack metamaterials are artificial materials able to harvest all the incident light regardless of wavelength, angle, or polarization. Here, we show the ultrablack properties of randomly aligned hierarchical carbon nanotube arrays with thicknesses below 200 nm. The thin coatings are realized by solution processing and dry-transfer deposition on different substrates. The hierarchical surface morphology of the coatings is biomimetic and provides a large effective area that improves the film optical absorption. Also, such a morphology is responsible for the moth-eye effect, which leads to the omnidirectional and polarization-independent suppression of optical reflection. The films exhibit an emissivity up to 99.36% typical of an ideal black body, resulting in the thinnest ultrablack metamaterial ever reported. Such a material may be exploited for thermal, optical, and optoelectronic devices such as heat sinks, optical shields, solar cells, light and thermal sensors, and light-emitting diodes.

Size Dependence of S-bonding on (111) Facets of Cu Nanoclusters

DOE PAGES

Boschen, Jeffery S.; Lee, Jiyoung; Windus, Theresa L.; ...

2016-04-21

We demonstrate a strong damped oscillatory size dependence of the adsorption energy for sulfur on the (111) facets of tetrahedral Cu nanoclusters up to sizes of ~300 atoms. This behavior reflects quantum size effects. Consistent results are obtained from density functional theory analyses utilizing either atomic orbital or plane-wave bases and using the same Perdew–Burke–Ernzerhof functional. Behavior is interpreted via molecular orbitals (MO), density of states (DOS), and crystal orbital Hamilton population (COHP) analyses.

On the Evolution from Non-Plasmonic Metal Nanoclusters to Plasmonic Nanocrystals

DTIC Science & Technology

2014-09-24

structures as well as for thiol binding on extended gold surfaces in self-assembled-monolayer (SAM) systems. Figure 1. Total structure of Au36( SPh ...thiolate ligands (Fig. 2). Remarkably, the Au133(SR)52 nanocluster (where, R = SPh -p-But) exhibits aesthetic orderings in structure from the gold kernel...and the trimeric and monomeric staples. As the smallest member in the TBBT (abbreviation of SPh -But) “magic series”, Au20(TBBT)16 together with Au28

Ligand-core NLO-phores: a combined experimental and theoretical approach to the two-photon absorption and two-photon excited emission properties of small-ligated silver nanoclusters.

PubMed

Russier-Antoine, Isabelle; Bertorelle, Franck; Calin, Nathalie; Sanader, Željka; Krstić, Marjan; Comby-Zerbino, Clothilde; Dugourd, Philippe; Brevet, Pierre-François; Bonačić-Koutecký, Vlasta; Antoine, Rodolphe

2017-01-19

We report a combined experimental and theoretical study of the two-photon absorption and excited emission properties of monodisperse ligand stabilized Ag 11 , Ag 15 and Ag 31 nanoclusters in aqueous solutions. The nanoclusters were synthesized using a cyclic reduction under oxidative conditions and separated by vertical gel electrophoresis. The two-photon absorption cross-sections of these protected noble metal nanoclusters measured within the biologically attractive 750-900 nm window are several orders of magnitude larger than that reported for commercially available standard organic dyes. The two-photon excited fluorescence spectra are also presented for excitation wavelengths within the same excitation spectral window. They exhibit size-tunability. Because the fundamental photophysical mechanisms underlying these multiphoton processes in ligand protected clusters with only a few metal atoms are not fully understood yet, a theoretical model is proposed to identify the key driving elements. Elements that regulate the dipole moments and the nonlinear optical properties are the nanocluster size, its structure and the charge distribution on both the metal core and the bound ligands. We coined this new class of NLO materials as "Ligand-Core" NLO-phores.

Absorptive carbon nanotube electrodes: Consequences of optical interference loss in thin film solar cells

NASA Astrophysics Data System (ADS)

Tait, Jeffrey G.; de Volder, Michaël F. L.; Cheyns, David; Heremans, Paul; Rand, Barry P.

2015-04-01

A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle devices. Additionally, other candidate absorber materials for thin film photovoltaics were simulated with absorptive contacts, elucidating device design in the absence of optical interference and reflection.A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle

Thin and Flexible Carbon Nanotube-Based Pressure Sensors with Ultra-wide Sensing Range.

PubMed

Doshi, Sagar M; Thostenson, Erik T

2018-06-26

A scalable electrophoretic deposition (EPD) approach is used to create novel thin, flexible and lightweight carbon nanotube-based textile pressure sensors. The pressure sensors can be produced using an extensive variety of natural and synthetic fibers. These piezoresistive sensors are sensitive to pressures ranging from the tactile range (< 10 kPa), in the body weight range (~ 500 kPa), and very high pressures (~40 MPa). The EPD technique enables the creation of a uniform carbon nanotube-based nanocomposite coating, in the range of 250-750 nm thick, of polyethyleneimine (PEI) functionalized carbon nanotubes on non-conductive fibers. In this work, non-woven aramid fibers are coated by EPD onto a backing electrode followed by film formation onto the fibers creating a conductive network. The electrically conductive nanocomposite coating is firmly bonded to the fiber surface and shows piezoresistive electrical/mechanical coupling. The pressure sensor displays a large in-plane change in electrical conductivity with applied out-of-plane pressure. In-plane conductivity change results from fiber/fiber contact as well as the formation of a sponge-like piezoresistive nanocomposite "interphase" between the fibers. The resilience of the nanocomposite interphase enables sensing of high pressures without permanent changes to the sensor response, showing high repeatability.

Hierarchical self-assembly of magnetic nanoclusters for theranostics: Tunable size, enhanced magnetic resonance imagability, and controlled and targeted drug delivery.

PubMed

Nguyen, Dai Hai; Lee, Jung Seok; Choi, Jong Hoon; Park, Kyung Min; Lee, Yunki; Park, Ki Dong

2016-04-15

Nanoparticle-based imaging and therapy are of interest for theranostic nanomedicine. In particular, superparamagnetic iron oxide (SPIO) nanoparticles (NPs) have attracted much attention in cancer imaging, diagnostics, and treatment because of their superior imagability and biocompatibility (approved by the Food and Drug Administration). Here, we developed SPIO nanoparticles (NPs) that self-assembled into magnetic nanoclusters (SAMNs) in aqueous environments as a theranostic nano-system. To generate multi-functional SPIO NPs, we covalently conjugated β-cyclodextrin (β-CD) to SPIO NPs using metal-adhesive dopamine groups. Polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the β-CD cavity through high affinity complexation. The core-shell structure of the magnetic nanoclusters was elucidated based on the condensed SPIO core and a PEG shell using electron microscopy and the composition was analyzed by thermogravimetric analysis (TGA). Our results indicate that nanocluster size could be readily controlled by changing the SPIO/PEG ratio in the assemblies. Interestingly, we observed a significant enhancement in magnetic resonance contrast due to the large cluster size and dense iron oxide core. In addition, tethering a tumor-targeting peptide to the SAMNs enhanced their uptake into tumor cells. PTX was efficiently loaded into β-CDs and released in a controlled manner when exposed to competitive guest molecules. These results strongly indicate that the SAMNs developed in this study possess great potential for application in image-guided cancer chemotherapy. In this study, we developed multi-functional SPIO NPs that self-assembled into magnetic nanoclusters (SAMNs) in aqueous conditions as a theranostic nano-system. The beta-cyclodextrin (β-CD) was immobilized on the surfaces of SPIO NPs and RGD-conjugated polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the β-CD cavity through high affinity complexation. We found that nanocluster size could be

Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

PubMed

Gómez, L; Rodríguez-Amaro, R

2009-04-21

On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode.

Thermodynamics, kinetics, and catalytic effect of dehydrogenation from MgH2 stepped surfaces and nanocluster: a DFT study

NASA Astrophysics Data System (ADS)

Reich, Jason; Wang, Linlin; Johnson, Duane

2013-03-01

We detail the results of a Density Functional Theory (DFT) based study of hydrogen desorption, including thermodynamics and kinetics with(out) catalytic dopants, on stepped (110) rutile and nanocluster MgH2. We investigate competing configurations (optimal surface and nanoparticle configurations) using simulated annealing with additional converged results at 0 K, necessary for finding the low-energy, doped MgH2 nanostructures. Thermodynamics of hydrogen desorption from unique dopant sites will be shown, as well as activation energies using the Nudged Elastic Band algorithm. To compare to experiment, both stepped structures and nanoclusters are required to understanding and predict the effects of ball milling. We demonstrate how these model systems relate to the intermediary sized structures typically seen in ball milling experiments.

Ultrafast coherence transfer in DNA-templated silver nanoclusters

PubMed Central

Thyrhaug, Erling; Bogh, Sidsel Ammitzbøll; Carro-Temboury, Miguel R; Madsen, Charlotte Stahl; Vosch, Tom; Zigmantas, Donatas

2017-01-01

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure and dynamics in these clusters. Here we report on a multidimensional spectroscopy investigation of the energy-level structure and the early-time relaxation cascade, which eventually results in the population of an emitting state. We find that the ultrafast intramolecular relaxation is strongly coupled to a specific vibrational mode, resulting in the concerted transfer of population and coherence between excited states on a sub-100 fs timescale. PMID:28548085

Structural evolutions and hereditary characteristics of icosahedral nano-clusters formed in Mg70Zn30 alloys during rapid solidification processes

NASA Astrophysics Data System (ADS)

Liang, Yong-Chao; Liu, Rang-Su; Xie, Quan; Tian, Ze-An; Mo, Yun-Fei; Zhang, Hai-Tao; Liu, Hai-Rong; Hou, Zhao-Yang; Zhou, Li-Li; Peng, Ping

2017-02-01

To investigate the structural evolution and hereditary mechanism of icosahedral nano-clusters formed during rapid solidification, a molecular dynamics (MD) simulation study has been performed for a system consisting of 107 atoms of liquid Mg70Zn30 alloy. Adopting Honeycutt-Anderson (HA) bond-type index method and cluster type index method (CTIM-3) to analyse the microstructures in the system it is found that for all the nano-clusters including 2~8 icosahedral clusters in the system, there are 62 kinds of geometrical structures, and those can be classified, by the configurations of the central atoms of basic clusters they contained, into four types: chain-like, triangle-tailed, quadrilateral-tailed and pyramidal-tailed. The evolution of icosahedral nano-clusters can be conducted by perfect heredity and replacement heredity, and the perfect heredity emerges when temperature is slightly less than Tm then increase rapidly and far exceeds the replacement heredity at Tg; while for the replacement heredity, there are three major modes: replaced by triangle (3-atoms), quadrangle (4-atoms) and pentagonal pyramid (6-atoms), rather than by single atom step by step during rapid solidification processes.

Continuous and rapid synthesis of nanoclusters and nanocrystals using scalable microstructured reactors

NASA Astrophysics Data System (ADS)

Jin, Hyung Dae

Recent advances in nanocrystalline materials production are expected to impact the development of next generation low-cost and/or high efficiency solar cells. For example, semiconductor nanocrystal inks are used to lower the fabrication cost of the absorber layers of the solar cells. In addition, some quantum confined nanocrystals display electron-hole pair generation phenomena with greater than 100% quantum yield, called multiple exciton generation (MEG). These quantum dots could potentially be used to fabricate solar cells that exceed the Schockley-Queisser limit. At present, continuous syntheses of nanoparticles using microreactors have been reported by several groups. Microreactors have several advantages over conventional batch synthesis. One advantage is their efficient heat transfer and mass transport. Another advantage is the drastic reduction in the reaction time, in many cases, down to minutes from hours. Shorter reaction time not only provides higher throughput but also provide better particle size control by avoiding aggregation and by reducing probability of oxidizing precursors. In this work, room temperature synthesis of Au11 nanoclusters and high temperature synthesis of chalcogenide nanocrystals were demonstrated using continuous flow microreactors with high throughputs. A high rate production of phosphine-stabilized Au11 nanoclusters was achieved using a layer-up strategy which involves the use of microlamination architectures; the patterning and bonding of thin layers of material (laminae) to create a multilayered micromixer in the range of 25-250 mum thick was used to step up the production of phosphine-stabilized Au11 nanoclusters. Continuous production of highly monodispersed phosphine-stabilized Au 11 nanoclusters at a rate of about 11.8 [mg/s] was achieved using a microreactor with a size of 1.687cm3. This result is about 30,000 times over conventional batch synthesis according to production rate/per reactor volume. We have elucidated the

Small size yet big action: a simple sulfate anion templated a discrete 78-nuclearity silver sulfur nanocluster with a multishell structure.

PubMed

Cheng, Li-Ping; Wang, Zhi; Wu, Qiao-Yu; Su, Hai-Feng; Peng, Tao; Luo, Geng-Geng; Li, Yan-An; Sun, Di; Zheng, Lan-Sun

2018-03-07

A discrete 78-nucleus silver-sulfur nanocluster with a sulfate-centered multishell structure was isolated and characterized. Its crystal structure revealed 18 and 60 Ag atoms in the inner and outer shell, respectively. The inner shell of 18-nuclearity Ag atoms is a very rare convex polyhedron featuring an elongated triangular orthobicupola. The incorporation of a sulfate anion and multishell arrangement in the nanocluster led to a dramatic decrease in the band gap (E g = 1.40 eV). Our study showed that simple anions can also induce the formation of high-nuclearity silver clusters with excellent optical properties.

Self-assembly of magnetic nanoclusters in diamond-like carbon by diffusion processes enhanced by collision cascades

NASA Astrophysics Data System (ADS)

Gupta, P.; Williams, G. V. M.; Hübner, R.; Vajandar, S.; Osipowicz, T.; Heinig, K.-H.; Becker, H.-W.; Markwitz, A.

2017-04-01

Mono-energetic cobalt implantation into hydrogenated diamond-like carbon at room temperature results in a bimodal distribution of implanted atoms without any thermal treatment. The ˜100 nm thin films were synthesised by mass selective ion beam deposition. The films were implanted with cobalt at an energy of 30 keV and an ion current density of ˜5 μA cm-2. Simulations suggest the implantation profile to be single Gaussian with a projected range of ˜37 nm. High resolution Rutherford backscattering measurements reveal that a bimodal distribution evolves from a single near-Gaussian distribution as the fluence increases from 1.2 to 7 × 1016 cm-2. Cross-sectional transmission electron microscopy further reveals that the implanted atoms cluster into nanoparticles. At high implantation doses, the nanoparticles assemble primarily in two bands: one near the surface with nanoparticle diameters of up to 5 nm and the other beyond the projected range with ˜2 nm nanoparticles. The bimodal distribution along with the nanoparticle formation is explained with diffusion enhanced by energy deposited during collision cascades, relaxation of thermal spikes, and defects formed during ion implantation. This unique distribution of magnetic nanoparticles with the bimodal size and range is of significant interest to magnetic semiconductor and sensor applications.

Carbon nanotube synthesis via the catalytic chemical vapor deposition of methane in the presence of iron, molybdenum, and iron-molybdenum alloy thin layer catalysts

NASA Astrophysics Data System (ADS)

Yahyazadeh, Arash; Khoshandam, Behnam

In this study, we documented the catalytic chemical vapor deposition synthesis of carbon nanotubes (CNTs) using ferrocene and molybdenum hexacarbonyl as catalyst nanoparticle precursors and methane as a nontoxic and economical carbon source for the first time. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive X-ray spectrometry and transmission electron microscopy of the thin layer catalyst as a simple and cost effective catalyst preparation after methane decomposition reaction, along with Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the growth of CNTs, from bimetallic nanoparticles, which are converted into iron-molybdenum alloy nanoparticles at 700 °C for pretreatment by hydrogen after chemical vapor deposition of thin layers. An investigation of the weight percentages of the chemical elements present in the CNTs synthesized from iron-molybdenum catalyst using quartz sheet substrate at 750 °C, confirmed a significant carbon yield of 75.4% which represents high catalyst activity. Additionally, multi-walled carbon nanotubes (∼16-55 nm in diameter and 1.2 μm in length) were observed in the iron-molybdenum alloy sample after methane decomposition reaction at 750 °C for 35 min. To show the role of iron and molybdenum coated on silicon substrate as two thin layer catalysts, samples were considered for CNTs growth (diameter ∼47-69 nm) at 800 °C and 830 °C, respectively. Moreover, the effect of hydrogen pretreatment was evaluated in terms of active metal coating properly. The best graphitic structure due to Raman spectroscopy outcomes (ID/IG ratio) was obtained for iron coated on a quartz sheet, which was estimated at 0.8505. Thermogravimetric analysis proved the thermal stability of the synthesized CNTs using iron thin-layer catalyst up to 350 °C.

Thin graphite bipolar plate with associated gaskets and carbon cloth flow-field for use in an ionomer membrane fuel cell

DOEpatents

Marchetti, George A.

2003-01-03

The present invention comprises a thin graphite plate with associated gaskets and pieces of carbon cloth that comprise a flow-field. The plate, gaskets and flow-field comprise a "plate and gasket assembly" for use in an ionomer membrane fuel cell, fuel cell stack or battery.

Thin and flexible all-solid supercapacitor prepared from novel single wall carbon nanotubes/polyaniline thin films obtained in liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

de Souza, Victor Hugo Rodrigues; Oliveira, Marcela Mohallem; Zarbin, Aldo José Gorgatti

2014-08-01

The present work describes for the first time the synthesis and characterization of single wall carbon nanotubes/polyaniline (SWNTs/PAni) nanocomposite thin films in a liquid-liquid interface, as well as the subsequent construction of a flexible all-solid supercapacitor. Different SWNTs/PAni nanocomposites were prepared by varying the ratio of SWNT to aniline, and the samples were characterized by scanning and transmission electron microscopy, Raman and UV-Vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The pseudo-capacitive behavior of the nanocomposites was evaluated by charge/discharge galvanostatic measurements. The presence of the SWNTs affected the electronic and vibrational properties of the polyaniline and also improved the pseudo-capacitive behavior of the conducting polymer. A very thin and flexible all-solid device was manufactured using two electrodes (polyethylene terephthalate-PET covered with the SWNT/PAni nanocomposite separated by a H2SO4-PVA gel electrolyte). The pseudo-capacitive behavior was characterized by a volumetric specific capacitance of approximately 76.7 F cm-3, even under mechanical deformation, indicating that this nanocomposite has considerable potential for application in new-generation energy storage devices.

Changes in Soil Carbon and Moisture over the Six Year after Thinning of a Natural Oak Forest

NASA Astrophysics Data System (ADS)

Kim, S.; Han, S. H.; Li, G.; Chang, H.; Kim, H. J.; Son, Y.

2017-12-01

The objective of this study was to assess the effects of thinning on soil carbon (C) in a natural oak forest in central Korea. The study forest received three different thinning treatments consisting of un-thinned control (UTC) and two thinning intensities (15% and 30% basal area reductions) in March in 2010. Precipitation near the study forest maintained the normal level from 2010 to 2013 (average 1,400 mm year-1), but abnormally decreased from 2014 to 2016 (average 800 mm year-1). To measure total soil C stock and soil moisture conditions, soils were collected from 0-10, 10-20, and 20-30 cm depths in June, 2010, 2013, and 2016, respectively. Soil microbial biomass C and C-cycling enzymes (β-glucosidase, cellobiohydrolase, β-xylosidase, phenol oxidase, and peroxidase) at 0-10 cm depth were determined in June, 2016. Total soil C stock at 0-30 cm depth increased throughout the study period, whereas soil moisture decreased at all depths from 2013 to 2016. Both thinning treatments had higher total soil C stock at 0-30 cm depth and moisture at 10-20 and 20-30 cm depths than the UTC in 2013 and 2016, whereas the treatments showed no effects in 2010. Microbial biomass C at 0-10 cm depth in 2016 also increased because of the thinning treatments, which was positively correlated to total soil C stock. However, any effects of thinning on C-cycling enzymes were not significant. Our results indicate that thinning could contribute to relieving the impacts of decreasing precipitation by enhancing the storage of soil moisture. Furthermore, the change in total soil C stock under thinning might result from the stimulation of microbial potential for retaining organic C as a form of biomass. This study was supported by the Ministry of Environment (2014001810002) and the National Institute of Forest Science of Korea (FM0101-2009-01).

Comparison of S-adsorption on (111) and (100) facets of Cu nanoclusters

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

Boschen, Jeffery S.; Lee, Jiyoung; Windus, Theresa L.

2016-10-31

In order to gain insight into the nature of chemical bonding of sulfur atoms on coinage metal surfaces, we compare the adsorption energy and structural parameters for sulfur at four-fold hollow (4fh) sites on (100) facets and at three-fold hollow (3fh) sites on (111) facets of Cu nanoclusters. Consistent results are obtained from localized atomic orbital and plane-wave based density functional theory using the same functionals. PBE and its hybrid counterpart (PBE0 or HSE06) also give similar results. 4fh sites are preferred over 3fh sites with stronger bonding by ~0.6 eV for nanocluster sizes above ~280 atoms. However, for smallermore » sizes there are strong variations in the binding strength and the extent of the binding site preference. In addition, we show that suitable averaging over clusters of different sizes, or smearing the occupancy of orbitals, provide useful strategies to aid assessment of the behavior in extended surface systems. From site-projected density of states analysis using the smearing technique, we show that S adsorbed on a 4fh site has similar bonding interactions with the substrate as that on a 3fh site, but with much weaker antibonding interactions.« less

An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

PubMed

Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

2015-04-08

An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility.

Design and mechanistic study of a novel gold nanocluster-based drug delivery system.

PubMed

Li, Qinzhen; Pan, Yiting; Chen, Tiankai; Du, Yuanxin; Ge, Honghua; Zhang, Buchang; Xie, Jianping; Yu, Haizhu; Zhu, Manzhou

2018-05-22

Chemically-triggered drug delivery systems (DDSs) have been extensively studied as they do not require specialized equipment to deliver the drug and can deeply penetrate human tissue. However, their syntheses are complicated and they tend to be cytotoxic, which restricts their clinical utility. In this work, the self-regulated drug loading and release capabilities of peptide-protected gold nanoclusters (Pep-Au NCs) are investigated using vancomycin (Van) as the model drug. Gold nanoclusters (Au NCs) coated with a custom-designed pentapeptide are synthesized as drug delivery nanocarriers and loaded with Van - a spontaneous process reliant on the specific binding between Van and the custom-designed peptide. The Van-loaded Au NCs show comparable antimicrobial activity with Van on its own, and the number of Van released by the Pep-Au NCs is found to be proportional to the amount of bacteria present. The controlled nature of the Van release is very encouraging, and predominantly due to the stronger binding affinity of Van with bacteria than that with Au NCs. In addition, these fluorescent Au NCs could also be used to construct temperature sensors, which enable the in vitro and in vivo bioimaging.

Thinning, Age, and Site Quality Influence Live Tree Carbon Stocks in Upland Hardwood Forests of the Southern Appalachians

Treesearch

Tara L. Keyser; Stanley J. Zarnoch

2012-01-01

This study examines the effects of thinning, age, and site quality on aboveground live tree carbon (ATC) (Mg/ha) stocks in upland hardwood forests of mixed-species composition in the southern Appalachian Mountains. In 1974, 80 plots ranging in size from 0.06 to 0.1 ha were established in even-aged, mixed-hardwood forests throughout the southern Appalachians. All trees...

How Does Amino Acid Ligand Modulate Au Core Structure and Characteristics in Peptide Coated Au Nanocluster?

PubMed

Li, Nan; Li, Xu; Zhao, Hongkang; Zhao, Lina

2018-03-01

The atomic structures and the corresponding physicochemical properties of peptide coated Au nanoclusters determine their distinctive biological targeting applications. To learn the modulation of amino acid ligand on the atomic structure and electronic characteristics of coated Au core is the fundamental knowledge for peptide coated Au nanocluster design and construction. Based on our recent coated Au nanocluster configuration study (Nanoscale, 2016, 8, 11454), we built the typically simplified Au13(Cys-Au-Cys) system to more clearly learn the basic modulation information of amino acid ligand on Au core by the density functional theory (DFT) calculations. There are two isomers as ligand adjacent bonding (Iso1) and diagonal bonding (Iso2) to Au13 cores. The geometry optimizations indicate the adjacent bonding Iso1 is more stable than Iso2. More important, the Au13 core of Iso1 distorts much more significantly than that of Iso2 by Cys-Au-Cys bonding through the root-mean-square deviation (RMSD) analysis, which modulate their electronic characteristics in different ways. In addition, the frontier molecular orbital results of Au13(Cys-Au-Cys) isomers confirm that the Au cores mainly determine the blue shifts of Au13(Cys-Au-Cys) systems versus the original Au13 core in their UV-visible absorption spectrum studies. The configuration of Au13 core performs deformation under Cys-Au-Cys ligand modulation to reach new stability with distinct atomic structure and electronic properties, which could be the theory basis for peptide coated AuNCs design and construction.

Transparent and flexible supercapacitors with single walled carbon nanotube thin film electrodes.

PubMed

Yuksel, Recep; Sarioba, Zeynep; Cirpan, Ali; Hiralal, Pritesh; Unalan, Husnu Emrah

2014-09-10

We describe a simple process for the fabrication of transparent and flexible, solid-state supercapacitors. Symmetric electrodes made up of binder-free single walled carbon nanotube (SWCNT) thin films were deposited onto polydimethylsiloxane substrates by vacuum filtration followed by a stamping method, and solid-state supercapacitor devices were assembled using a gel electrolyte. An optical transmittance of 82% was found for 0.02 mg of SWCNTs, and a specific capacitance of 22.2 F/g was obtained. The power density can reach to 41.5 kW · kg(-1) and shows good capacity retention (94%) upon cycling over 500 times. Fabricated supercapacitors will be relevant for the realization of transparent and flexible devices with energy storage capabilities, displays and touch screens in particular.

Energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding.

PubMed

Shu, G W; Lin, C C; Lin, H T; Lin, T N; Shen, J L; Chiu, C H; Li, Z Y; Kuo, H C; Lin, C C; Wang, S C; Lin, C A J; Chang, W H

2011-03-14

We present the first observation of resonance energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding. Steady-state and time-resolved photoluminescence measurements provide conclusive evidence of resonance energy transfer and obtain an optimum transfer efficiency of ~72%. A set of rate equations is successfully used to model the kinetics of resonance energy transfer.

Study of optical properties of vacuum evaporated carbon nanotube containing Se80Te16Cu4 thin films

NASA Astrophysics Data System (ADS)

Upadhyay, A. N.; Tiwari, R. S.; Singh, Kedar

2016-08-01

Thin films of Se80Te16Cu4 glassy alloy and 3 wt.% of carbon nanotubes (CNTs) containing Se80Te16Cu4 glassy composite were deposited on clean glass substrate by thermal evaporation technique. The scanning electron microscope and energy dispersive x-ray analysis were performed to investigate the surface morphology and elemental composition of as synthesised samples. The reflectance and transmittance spectra of as-deposited thin films were recorded (200-1100 nm) by using UV/VIS/NIR spectrophotometer. The optical band gap and optical constants such as absorption coefficient (α), refractive index (n) and extinction coefficient (k) of Se80Te16Cu4 and 3 wt.% CNTs-Se80Te16Cu4 glassy composite thin films were calculated. It is observed that optical properties alter due to CNTs incorporation in Se80Te16Cu4 glassy alloy. Effect on optical properties due to CNTs incorporation can be explained in terms of concentration of unsaturated bonds/defects in the localised states.

The effects of temperature on the surface resistivity of polyvinyl alcohol (PVA) thin films doped with silver nanoparticles and multi-walled carbon-nanotubes for optoelectronic and sensor applications

NASA Astrophysics Data System (ADS)

Polius, Jemilia R.

This thesis reports measurements of the temperature-dependent surface resistivity of multi-wall carbon nanotube doped polyvinyl alcohol (PVA) thin films. In the temperature range from 22°C to 40°C in a humidity controlled environment, it was found that the surface resistivity decreased initially but raised as the temperature continued to increase. I report surface resistivity measurements as a function of temperature of both multiwall and single-wall carbon nanotube doped PVA thin films, with comparison of the similarities and differences between the two types of film types. This research was conducted using the combined instrumentation of the KEITHLEY Model 6517 Electrometer and the KEITHLEY Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films.

Carbon nanotube macroelectronics

NASA Astrophysics Data System (ADS)

Zhang, Jialu

In this dissertation, I discuss the application of carbon nanotubes in macroelectronis. Due to the extraordinary electrical properties such as high intrinsic carrier mobility and current-carrying capacity, single wall carbon nanotubes are very desirable for thin-film transistor (TFT) applications such as flat panel display, transparent electronics, as well as flexible and stretchable electronics. Compared with other popular channel material for TFTs, namely amorphous silicon, polycrystalline silicon and organic materials, nanotube thin-films have the advantages of low-temperature processing compatibility, transparency, and flexibility, as well as high device performance. In order to demonstrate scalable, practical carbon nanotube macroelectroncis, I have developed a platform to fabricate high-density, uniform separated nanotube based thin-film transistors. In addition, many other essential analysis as well as technology components, such as nanotube film density control, purity and diameter dependent semiconducting nanotube electrical performance study, air-stable n-type transistor fabrication, and CMOS integration platform have also been demonstrated. On the basis of the above achievement, I have further demonstrated various kinds of applications including AMOLED display electronics, PMOS and CMOS logic circuits, flexible and transparent electronics. The dissertation is structured as follows. First, chapter 1 gives a brief introduction to the electronic properties of carbon nanotubes, which serves as the background knowledge for the following chapters. In chapter 2, I will present our approach of fabricating wafer-scale uniform semiconducting carbon nanotube thin-film transistors and demonstrate their application in display electronics and logic circuits. Following that, more detailed information about carbon nanotube thin-film transistor based active matrix organic light-emitting diode (AMOLED) displays is discussed in chapter 3. And in chapter 4, a technology to

Composite carbon foam electrode

DOEpatents

Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

1997-05-06

Carbon aerogels used as a binder for granulated materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. 1 fig.

Composite carbon foam electrode

DOEpatents

Mayer, Steven T.; Pekala, Richard W.; Kaschmitter, James L.

1997-01-01

Carbon aerogels used as a binder for granularized materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivty and power to system energy.

Mathematical simulation of the amplification of 1790-nm laser radiation in a nuclear-excited He - Ar plasma containing nanoclusters of uranium compounds

NASA Astrophysics Data System (ADS)

Kosarev, V. A.; Kuznetsova, E. E.

2014-02-01

The possibility of applying dusty active media in nuclearpumped lasers has been considered. The amplification of 1790-nm radiation in a nuclear-excited dusty He - Ar plasma is studied by mathematical simulation. The influence of nanoclusters on the component composition of the medium and the kinetics of the processes occurring in it is analysed using a specially developed kinetic model, including 72 components and more than 400 reactions. An analysis of the results indicates that amplification can in principle be implemented in an active laser He - Ar medium containing 10-nm nanoclusters of metallic uranium and uranium dioxide.

Sensitive Detection of Single-Cell Secreted H2O2 by Integrating a Microfluidic Droplet Sensor and Au Nanoclusters.

PubMed

Shen, Rui; Liu, Peipei; Zhang, Yiqiu; Yu, Zhao; Chen, Xuyue; Zhou, Lu; Nie, Baoqing; Żaczek, Anna; Chen, Jian; Liu, Jian

2018-04-03

As an important signaling molecule, hydrogen peroxide (H 2 O 2 ) secreted externally by the cells influences cell migration, immunity generation, and cellular communications. Herein, we have developed a microfluidic approach with droplets in combination with Au nanoclusters for the sensitive detection of H 2 O 2 secreted by a single cell. Isolated in the ultrasmall volume (4.2 nL) of a microdroplet, single-cell secreted H 2 O 2 can initiate dramatic fluorescence changes of horseradish peroxidase-Au nanoclusters. We have demonstrated an ultrahigh sensitivity (200-400 attomole H 2 O 2 directly measured from a single cell) with good specificity. It offers a useful research tool to study the cell-to-cell differences of H 2 O 2 secretion at the single-cell level.

Use of near-infrared luminescent gold nanoclusters for detection of macrophages

PubMed Central

Sapozhnikova, Veronika; Willsey, Brian; Asmis, Reto; Wang, Tianyi; Jenkins, James Travis; Mancuso, Jacob; Ma, Li Leo; Kuranov, Roman; Milner, Thomas E.; Johnston, Keith

2012-01-01

Abstract. We determined the effect of aggregation and coating thickness of gold on the luminescence of nanoparticles engulfed by macrophages and in gelatin phantoms. Thin gold-coated iron oxide nanoclusters (nanoroses) have been developed to target macrophages to provide contrast enhancement for near-infrared optical imaging applications. We compare the brightness of nanoroses luminescent emissions in response to 635 nm laser excitation to other nanoparticles including nanoshells, nanorods, and Cy5 conjugated iron oxide nanoparticles. Luminescent properties of all these nanoparticles were investigated in monomeric and aggregated form in gelatin phantoms and primary macrophage cell cultures using confocal microscopy. Aggregation of the gold nanoparticles increased luminescence emission and correlated with increased surface mass of gold per nanoparticle (nanoshells 37±14.30×10−3 brightness with 1.23×10−4 wt of gold (g)/nanoparticle versus original nanorose 1.45±0.37×10−3 with 2.10×10−16 wt of gold/nanoparticle, p<0.05). Nanoshells showed greater luminescent intensity than original nanoroses or Cy5 conjugated iron oxide nanoparticles when compared as nanoparticles per macrophage (38±10 versus 11±2.8 versus 17±6.5, p<0.05, respectively, ANOVA), but showed relatively poor macrophage uptake (1025±128 versus 7549±236 versus 96,000  nanoparticles/cell, p<0.05, student t-test nanoshells versus nanoroses). Enhancement of gold fluorescent emissions by nanoparticles can be achieved by reducing the thickness of the gold coating, by clustering the gold on the surface of the nanoparticles (nanoshells), and by clustering the gold nanoparticles themselves. PMID:22463038

Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

NASA Astrophysics Data System (ADS)

Pablo-Pedro, Ricardo; Lopez-Rios, Hector; Mendoza-Cortes, Jose-L.; Kong, Jing; Fomine, Serguei; Van Voorhis, Troy; Dresselhaus, Mildred S.

2018-05-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we perform density-functional-theory calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n -type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the "zigzag" and "armchair" directions may permit the design of novel n -type electronic materials and spintronics devices that incorporate both high electron affinities and very low internal reorganization energies.

Ratiometric electrochemiluminescent strategy regulated by electrocatalysis of palladium nanocluster for immunosensing.

PubMed

Huang, Yin; Lei, Jianping; Cheng, Yan; Ju, Huangxian

2016-03-15

This work designed a novel ratiometric electrochemiluminescence (ECL) immunosensing approach based on two different ECL emitters: CdS quantum dots (QDs) as cathodic emitter and luminol as anodic emitter. The ECL immunosensor was constructed by a layer-by-layer modification of CdS QDs, Au nanoparticles and capture antibody on a glassy carbon electrode. With hydrogen peroxide as ECL coreactant, the immunosensor showed a cathodic ECL emission of CdS QDs at -1.5 V (vs Ag/AgCl) in air-saturated pH 8.0 buffer. Upon the formation of sandwich immunoassay, the lumiol/palladium nanoclusters (Pd NCs)@graphene oxide probe was introduced to the electrode. Therefore, the cathodic ECL intensity decreased and luminol anodic ECL emission was appeared at +0.3 V (vs Ag/AgCl) owing to the competition of the coreactant of hydrogen peroxide. Using carcino-embryonic antigen as model, this ratiometric ECL strategy could be used for immunoassay with a linear range of 1.0-100 pg mL(-1) and a detection limit of 0.62 pg mL(-1). The enhanced ratiometric ECL signal resulted from the high density and excellent electrocatalysis of the loaded Pd NCs. The immunosensor exhibited good stability and acceptable fabrication reproducibility and accuracy, showing a great promising for clinical application. This electrocatalysis-regulated ratiometric ECL provides a new concept for ECL measurement, and could be conveniently extended for detection of other protein biomarkers. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel electrochemiluminescence of silver nanoclusters fabricated on triplex DNA scaffolds for label-free detection of biothiols.

PubMed

Feng, Lingyan; Wu, Li; Xing, Feifei; Hu, Lianzhe; Ren, Jinsong; Qu, Xiaogang

2017-12-15

Electrochemiluminescence (ECL) of metal nanoclusters and their application have been widely reported due to the good biocompatibility, fascinating electrocatalytic activity and so on. Using DNA as synthesis template opens new opportunities to modulate the physical properties of AgNCs. Triplex DNA has been reported for the site-specific, homogeneous and highly stable silver nanoclusters (AgNCs) fabrication from our recent research. Here we further explore their extraordinary ECL properties and applications in biosensor utilization. By reasonable design of DNA sequence, AgNCs were obtained in the predefined position of CG.C + sites of triplex DNA, and the ECL emission at a low potential was observed with this novel DNA template. Finally, a simple and label-free method was developed for biothiols detection based on the enhanced catalytic reaction and a robust interaction between the triplex-AgNCs and cysteine, by influencing the microenvironment provided by DNA template. Copyright © 2017 Elsevier B.V. All rights reserved.

L1(0)-FePd nanocluster wires by template-directed thermal decomposition and subsequent hydrogen reduction

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

Cui, BZ; Marinescu, M; Liu, JF

2013-12-14

This paper reports the nanostructure, formation mechanism, and magnetic properties of tetragonal L1(0)-type Fe55Pd45 (at. %) nanocluster wires (NCWs) fabricated by thermal decomposition of metal nitrates and subsequent hydrogen reduction in nanoporous anodized aluminum oxide templates. The as-synthesized NCWs have diameters in the range of 80-300 nm, and lengths in the range of 0.5-10 mu m. The NCWs are composed of roughly round-shaped nanoclusters in the range of 3-30 nm in size and a weighted average size of 10 nm with a mixture of single-crystal and poly-crystalline structures. The obtained intrinsic coercivity H-i(c) of 3.32 kOe at room temperature formore » the tetragonal Fe55Pd45 NCWs is higher than those of electrodeposited Fe-Pd solid nanowires while among the highest values reported so far for L1(0)-type FePd nanoparticles. (C) 2013 AIP Publishing LLC.« less

Fully integrated carbon nanotube composite thin film strain sensors on flexible substrates for structural health monitoring

NASA Astrophysics Data System (ADS)

Burton, A. R.; Lynch, J. P.; Kurata, M.; Law, K. H.

2017-09-01

Multifunctional thin film materials have opened many opportunities for novel sensing strategies for structural health monitoring. While past work has established methods of optimizing multifunctional materials to exhibit sensing properties, comparatively less work has focused on their integration into fully functional sensing systems capable of being deployed in the field. This study focuses on the advancement of a scalable fabrication process for the integration of multifunctional thin films into a fully integrated sensing system. This is achieved through the development of an optimized fabrication process that can create a broad range of sensing systems using multifunctional materials. A layer-by-layer deposited multifunctional composite consisting of single walled carbon nanotubes (SWNT) in a polyvinyl alcohol and polysodium-4-styrene sulfonate matrix are incorporated with a lithography process to produce a fully integrated sensing system deposited on a flexible substrate. To illustrate the process, a strain sensing platform consisting of a patterned SWNT-composite thin film as a strain-sensitive element within an amplified Wheatstone bridge sensing circuit is presented. Strain sensing is selected because it presents many of the design and processing challenges that are core to patterning multifunctional thin film materials into sensing systems. Strain sensors fabricated on a flexible polyimide substrate are experimentally tested under cyclic loading using standard four-point bending coupons and a partial-scale steel frame assembly under lateral loading. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with linearity and sensitivity exceeding 0.99 and 5 {{V}}/{ε }, respectively. The thin film strain sensors are robust and are capable of high strain measurements beyond 3000 μ {ε }.

Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(II) ion in aqueous solution.

PubMed

Lin, Zhijin; Luo, Fenqiang; Dong, Tongqing; Zheng, Liyan; Wang, Yaxian; Chi, Yuwu; Chen, Guonan

2012-05-21

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu(2+) in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane (i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu(2+) ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material.

High Voltage Magnesium-ion Battery Enabled by Nanocluster Mg3Bi2 Alloy Anode in Noncorrosive Electrolyte.

PubMed

Tan, Yi-Hong; Yao, Wei-Tang; Zhang, Tianwen; Ma, Tao; Lu, Lei-Lei; Zhou, Fei; Yao, Hong-Bin; Yu, Shu-Hong

2018-05-03

Currently, developing high voltage (beyond 2 V) rechargeable Mg-ion batteries still remains a great challenge owing to the limit of corrosive electrolyte and low compatibility of anode material. Here we report a facile one step solid state alloying route to synthesize nanoclustered Mg 3 Bi 2 alloy as a high-performance anode to build up a 2 V Mg-ion battery using noncorrosive electrolyte. The fabricated nanoclustered Mg 3 Bi 2 anode delivers a high reversible specific capacity (360 mAh g -1 ) with excellent stability (90.7% capacity retention over 200 cycles) and high Coulombic efficiency (average 98%) at 0.1 A g -1 . The good performance is attributed to the stable nanostructures, which effectively accommodate the reversible Mg 2+ ion insertion/deinsertion without losing electric contact among clusters. Significantly, the nanoclustered Mg 3 Bi 2 anode can be coupled with high voltage cathode Prussian Blue to assemble a full cell using noncorrosive electrolyte, showing a stable cycling (88% capacity retention over 200 cycles at 0.2 A g -1 ) and good rate capability (103 mAh g -1 at 0.1 A g -1 and 58 mAh g -1 at 2 A g -1 ). The energy and power density of the as-fabricated full cell can reach up to 81 Wh kg -1 and 2850 W kg -1 , respectively, which are both the highest values among the reported Mg-ion batteries using noncorrosive electrolytes. This study demonstrates a cost-effective route to fabricate stable and high voltage rechargeable Mg-ion battery potentially for grid-scale energy storage.

Quantification of NS1 dengue biomarker in serum via optomagnetic nanocluster detection

NASA Astrophysics Data System (ADS)

Antunes, Paula; Watterson, Daniel; Parmvi, Mattias; Burger, Robert; Boisen, Anja; Young, Paul; Cooper, Matthew A.; Hansen, Mikkel F.; Ranzoni, Andrea; Donolato, Marco

2015-11-01

Dengue is a tropical vector-borne disease without cure or vaccine that progressively spreads into regions with temperate climates. Diagnostic tools amenable to resource-limited settings would be highly valuable for epidemiologic control and containment during outbreaks. Here, we present a novel low-cost automated biosensing platform for detection of dengue fever biomarker NS1 and demonstrate it on NS1 spiked in human serum. Magnetic nanoparticles (MNPs) are coated with high-affinity monoclonal antibodies against NS1 via bio-orthogonal Cu-free ‘click’ chemistry on an anti-fouling surface molecular architecture. The presence of the target antigen NS1 triggers MNP agglutination and the formation of nanoclusters with rapid kinetics enhanced by external magnetic actuation. The amount and size of the nanoclusters correlate with the target concentration and can be quantified using an optomagnetic readout method. The resulting automated dengue fever assay takes just 8 minutes, requires 6 μL of serum sample and shows a limit of detection of 25 ng/mL with an upper detection range of 20000 ng/mL. The technology holds a great potential to be applied to NS1 detection in patient samples. As the assay is implemented on a low-cost microfluidic disc the platform is suited for further expansion to multiplexed detection of a wide panel of biomarkers.

Evolution of magnetism of Cr nanoclusters on a Au(111) surface

NASA Astrophysics Data System (ADS)

Gotsis, Harry; Kioussis, Nicholas; Papaconstantopoulos, Dimitri

2004-03-01

Advances in low-temperature scanning tunneling microscopy under ultrahigh vacuum have provided new opportunities for investigating the magnetic structures of nanoclusters adsorbed on surfaces. Recent STM studies of Cr trimers on the Au(111) surface suggest a switching between two distinct electronic states. We have carried out ab initio electronic structure calculations to investigate the structural, electronic and magnetic properties of isolated Cr atoms, Cr dimers and trimers in different geometry. We will present results for the evolution of magnetic behavior including noncollinear magnetism and provide insight in the connection between magnetism and geometry.

High rate deposition system for metal-cluster/SiO x C y H z -polymer nanocomposite thin films

NASA Astrophysics Data System (ADS)

Peter, T.; Rehders, S.; Schürmann, U.; Strunskus, T.; Zaporojtchenko, V.; Faupel, F.

2013-06-01

A system for deposition of nanocomposite materials consisting of a SiO x C y H z -polymer matrix and Ag nanoclusters is presented. Ag nanoclusters with sizes between 2 and 20 nm are produced in a gas aggregation cluster source and are deposited through a focused beam at a high rate. This cluster source is presented in detail and the characteristics of the produced nanoclusters are shown. Simultaneously, a SiO x C y H z -polymer matrix is grown from the precursor hexamethyldisiloxane in an RF plasma. The beam of clusters is deposited into the growing polymer, forming the composite material. This process allows the rapid deposition of composite material with varying metal nanocluster concentrations and properties. Since the cluster generation is separated from the matrix growth, the properties of both can be controlled independently. In this study, we present two types of nanocomposite samples, in the first the Ag nanoclusters are homogeneously distributed in the matrix, in the second type the Ag nanoclusters form a layer which is covered by the matrix. These samples are investigated using transmission electron micrography to determine the morphology. Furthermore, the optical properties are probed using optical transmission spectroscopy and the plasmonic resonance behavior is discussed.

Enzyme activity of α-chymotrypsin: Deactivation by gold nano-cluster and reactivation by glutathione.

PubMed

Ghosh, Catherine; Mondal, Tridib; Bhattacharyya, Kankan

2017-05-15

Effect of gold nanoclusters (Au-NCs) on the circular dichroism (CD) spectra and enzymatic activity of α-chymotrypsin (ChT) (towards hydrolysis of a substrate, N-succinyl-l-phenylalanine p-nitroanilide) are studied. The CD spectra indicate that on binding to Au-NC, ChT is completely unfolded, resulting in nearly zero ellipticity. α-chymotrypsin (ChT) coated gold nano-clusters exhibit almost no enzymatic activity. Addition of glutathione (GSH) or oxidized glutathione (GSSG) restore the enzyme activity of α-chymotrypsin by 30-45%. ChT coated Au-NC exhibits two emission maxima-one at 480nm (corresponding to Au 10 ) and one at 640nm (Au 25 ). On addition of glutathione (GSH) or oxidized glutathione (GSSG) the emission peak at 640nm vanishes and only one peak at 480nm (Au 10 ) remains. MALDI mass spectrometry studies suggest addition of glutathione (GSH) to α-chymotrypsin capped Au-NCs results in the formation of glutathione-capped Au-NCs and α-chymotrypsin is released from Au-NCs. CD spectroscopy indicates that the conformation of the released α-chymotrypsin is different from that of the native α-chymotrypsin. Copyright © 2017 Elsevier Inc. All rights reserved.

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

PubMed

Kocabas, Coskun; Hur, Seung-Hyun; Gaur, Anshu; Meitl, Matthew A; Shim, Moonsub; Rogers, John A

2005-11-01

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.

Controlled Zn-mediated grafting of thin layers of bipodal diazonium salt on gold and carbon substrates.

PubMed

Torréns, Mabel; Ortiz, Mayreli; Turner, Anthony P F; Beni, Valerio; O'Sullivan, Ciara K

2015-01-07

A controlled, rapid, and potentiostat-free method has been developed for grafting the diazonium salt (3,5-bis(4-diazophenoxy)benzoic acid tetrafluoroborate (DCOOH)) on gold and carbon substrates, based on a Zn-mediated chemical dediazonation. The highly stable thin layer organic platforms obtained were characterized by cyclic voltammetry, AFM, impedance, XP, and Raman spectroscopies. A dediazonation mechanism based on radical formation is proposed. Finally, DCOOH was proved as a linker to an aminated electroactive probe. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microwave-Assisted Synthesis of Red-Light Emitting Au Nanoclusters with the Use of Egg White

ERIC Educational Resources Information Center

Tian, Jinghan; Yan, Lei; Sang, Aohua; Yuan, Hongyan; Zheng, Baozhan; Xiao, Dan

2014-01-01

We developed a simple, cost-effective, and eco-friendly method to synthesize gold nanoclusters (AuNCs) with red fluorescence. The experiment was performed using HAuCl[subscript 4], egg white, Na[subscript 2]CO[subscript 3] (known as soda ash or washing soda), and a microwave oven. In our experiment, fluorescent AuNCs were prepared within a…

Positron annihilation 2D-ACAR study of semi-coherent Li nanoclusters in MgO( 1 0 0 ) and MgO( 1 1 0 )

NASA Astrophysics Data System (ADS)

Falub, C. V.; Mijnarends, P. E.; Eijt, S. W. H.; van Huis, M. A.; van Veen, A.; Schut, H.

2002-05-01

Depth selective positron annihilation two-dimensional angular correlation of annihilation radiation (2D-ACAR) is used to determine the electronic structure of Li nanoclusters formed by implantation of 10 16 cm -26Li ions (with an energy of 30 keV) in MgO(1 0 0) and (1 1 0) crystals, and subsequently annealed at 950 K. The 2D-ACAR spectra of Li-implanted MgO obtained with 4 keV positrons reveal the semi-coherent ordering state of the embedded metallic Li nanoclusters. The results agree with ab initio Korringa-Kohn-Rostoker calculations.

The thin section rock physics: Modeling and measurement of seismic wave velocity on the slice of carbonates

NASA Astrophysics Data System (ADS)

Wardaya, P. D.; Noh, K. A. B. M.; Yusoff, W. I. B. W.; Ridha, S.; Nurhandoko, B. E. B.

2014-09-01

This paper discusses a new approach for investigating the seismic wave velocity of rock, specifically carbonates, as affected by their pore structures. While the conventional routine of seismic velocity measurement highly depends on the extensive laboratory experiment, the proposed approach utilizes the digital rock physics view which lies on the numerical experiment. Thus, instead of using core sample, we use the thin section image of carbonate rock to measure the effective seismic wave velocity when travelling on it. In the numerical experiment, thin section images act as the medium on which wave propagation will be simulated. For the modeling, an advanced technique based on artificial neural network was employed for building the velocity and density profile, replacing image's RGB pixel value with the seismic velocity and density of each rock constituent. Then, ultrasonic wave was simulated to propagate in the thin section image by using finite difference time domain method, based on assumption of an acoustic-isotropic medium. Effective velocities were drawn from the recorded signal and being compared to the velocity modeling from Wyllie time average model and Kuster-Toksoz rock physics model. To perform the modeling, image analysis routines were undertaken for quantifying the pore aspect ratio that is assumed to represent the rocks pore structure. In addition, porosity and mineral fraction required for velocity modeling were also quantified by using integrated neural network and image analysis technique. It was found that the Kuster-Toksoz gives the closer prediction to the measured velocity as compared to the Wyllie time average model. We also conclude that Wyllie time average that does not incorporate the pore structure parameter deviates significantly for samples having more than 40% porosity. Utilizing this approach we found a good agreement between numerical experiment and theoretically derived rock physics model for estimating the effective seismic wave

Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

PubMed

Salvatierra, Rodrigo Villegas; Zakhidov, Dante; Sha, Junwei; Kim, Nam Dong; Lee, Seoung-Ki; Raji, Abdul-Rahman O; Zhao, Naiqin; Tour, James M

2017-03-28

Here we show that a versatile binary catalyst solution of Fe 3 O 4 /AlO x nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlO x nanoclusters over Fe 3 O 4 crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg -1 ), high-power density capabilities (∼20,500 W kg -1 at 29 Wh kg -1 ), and a large operating voltage window (4.3 to 0.01 V).

Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction

NASA Astrophysics Data System (ADS)

Zhang, Teng-Fei; Li, Zhi-Peng; Wang, Jiu-Zhen; Kong, Wei-Yu; Wu, Guo-An; Zheng, Yu-Zhen; Zhao, Yuan-Wei; Yao, En-Xu; Zhuang, Nai-Xi; Luo, Lin-Bao

2016-12-01

In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50-5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW-1 and 4.87 × 1010 cm Hz1/2 W-1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems.

Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction

PubMed Central

Zhang, Teng-Fei; Li, Zhi-Peng; Wang, Jiu-Zhen; Kong, Wei-Yu; Wu, Guo-An; Zheng, Yu-Zhen; Zhao, Yuan-Wei; Yao, En-Xu; Zhuang, Nai-Xi; Luo, Lin-Bao

2016-01-01

In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50–5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW−1 and 4.87 × 1010 cm Hz1/2 W−1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems. PMID:27929053

SPM Investigation of superhard carbon prepared from C{sub 60} fullerene

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

Hassanien, A.; Tokumoto, M.; Kozlov, M. E.

1999-09-30

A very hard and conducting form of carbon was obtained from C{sub 60} fullerene at moderately high pressure (2.6-3GPa) and temperature (700C). The hardness of the material is more than 4000 kg/mm{sup 2}. Its electrical conductivity is about 100 S/cm and is weakly dependent on temperature. A comparative {sup 13}C NMR study shows no explicit evidence for the presence of diamond like sp{sup 3}-character. So far, it has been of great difficulties to correlate between the atomic structure and these remarkable physical properties, as X-ray diffraction and Raman measurements show lack of long-range crystalline order. In this report we shallmore » present structure and property analysis measured by STM and STS techniques. High-resolution topographic images reveal the mesoscopic structure in which spherical metallic nano-clusters of size up to 6 nm, are covalently interlinked. The atomic structure of the nanoclusters contains pentagon rings, which in turn introduces a curvature in the graphene lattice. The presence of pentagon rings suggests that the bonding carry non-planer sp{sup 2}-character which might be correlated with the observed significant hardness.« less

Fabrication of air-stable n-type carbon nanotube thin-film transistors on flexible substrates using bilayer dielectrics.

PubMed

Li, Guanhong; Li, Qunqing; Jin, Yuanhao; Zhao, Yudan; Xiao, Xiaoyang; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan

2015-11-14

Single-walled carbon nanotube (SWNT) thin-film transistors hold great potential for flexible electronics. However, fabrication of air-stable n-type devices by methods compatible with standard photolithography on flexible substrates is challenging. Here, we demonstrated that by using a bilayer dielectric structure of MgO and atomic layer deposited (ALD) Al2O3 or HfO2, air-stable n-type devices can be obtained. The mechanism for conduction type conversion was elucidated and attributed to the hole depletion in SWNT, the decrease of the trap state density by MgO assimilating adsorbed water molecules in the vicinity of SWNT, and the energy band bending because of the positive fixed charges in the ALD layer. The key advantage of the method is the relatively low temperature (120 or 90 °C) required here for the ALD process because we need not employ this step to totally remove the absorbates on the SWNTs. This advantage facilitates the integration of both p-type and n-type transistors through a simple lift off process and compact CMOS inverters were demonstrated. We also demonstrated that the doping of SWNTs in the channel plays a more important role than the Schottky barriers at the metal contacts in carbon nanotube thin-film transistors, unlike the situation in individual SWNT-based transistors.

Facile synthesis of hierarchical mesoporous weirds-like morphological MnO2 thin films on carbon cloth for high performance supercapacitor application.

PubMed

Shinde, Pragati A; Lokhande, Vaibhav C; Ji, Taeksoo; Lokhande, Chandrakant D

2017-07-15

The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO 2 have been successfully fabricated on flexible carbon cloth by simple but capable hydrothermal method at different deposition temperatures. The deposition temperature has strong influence on reaction kinetics, which subsequently alters the morphology and electrochemical performance. Among different nanostructured MnO 2 thin films, the mesoporous weirds composed thin film obtained at temperature of 453K exhibits excellent physical and electrochemical features for supercapacitor application. The weirds composed MnO 2 thin film exhibits specific surface area of 109m 2 g -1 , high specific capacitance of 595Fg -1 with areal capacitance of 4.16Fcm -2 at a scan rate of 5mVs -1 and high specific energy of 56.32Whkg -1 . In addition to this, MnO 2 weirds attain capacity retention of 87 % over 2000 CV cycles, representing better cycling stability. The enhanced electrochemical performance could be ascribed to direct growth of highly porous MnO 2 weirds on carbon cloth which provide more pathways for easy diffusion of electrolyte into the interior of electroactive material. The as-fabricated electrode with improved performance could be ascribed as a potential electrode material for energy storage devices. Copyright © 2017 Elsevier Inc. All rights reserved.

Enhanced thermal conductance of polymer composites through embedding aligned carbon nanofibers

DOE PAGES

Nicholas, Roberts; Hensley, Dale K.; Wood, David

2016-07-08

The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers

Enhanced thermal conductance of polymer composites through embedding aligned carbon nanofibers

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

Nicholas, Roberts; Hensley, Dale K.; Wood, David

The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers

Blowing Carbon Nanotubes to Carbon Nanobulbs

NASA Astrophysics Data System (ADS)

Su, D. S.; Zhu, Z. P.; Lu, Y.; Schlögl, R.; Weinberg, G.; Liu, Z. Y.

2004-09-01

We report the blowing of multi-walled carbon nanotubes into carbon nanobulbs. This is realized in a unique tube growth environment generated by explosive decomposition of picric acid mixed with nickel formate. The carbon spherical bulbs are characterized by large dimensions (up to 900 nm), thin walls (around 10 nm), and fully hollow cores. The walls are in graphitic structure of sp2 hybridized carbons. Bulb-tube assemblies are found as intermediate derivatives of blowing. A joint action of the filled high-pressure gases and the structural defects in the carbon nanotubes is responsible to the formation of the carbon nanobulbs. Our finding may indicate the possibility to engineer the carbon nanotubes to the designed nanostructures.

Electrolytic synthesis of aqueous aluminum nanoclusters and in situ characterization by femtosecond Raman spectroscopy and computations

PubMed Central

Wang, Wei; Liu, Weimin; Chang, I-Ya; Wills, Lindsay A.; Zakharov, Lev N.; Boettcher, Shannon W.; Cheong, Paul Ha-Yeon; Fang, Chong; Keszler, Douglas A.

2013-01-01

The selective synthesis and in situ characterization of aqueous Al-containing clusters is a long-standing challenge. We report a newly developed integrated platform that combines (i) a selective, atom-economical, step-economical, scalable synthesis of Al-containing nanoclusters in water via precision electrolysis with strict pH control and (ii) an improved femtosecond stimulated Raman spectroscopic method covering a broad spectral range of ca. 350–1,400 cm−1 with high sensitivity, aided by ab initio computations, to elucidate Al aqueous cluster structures and formation mechanisms in real time. Using this platform, a unique view of flat [Al13(μ3-OH)6(μ2-OH)18(H2O)24](NO3)15 nanocluster formation is observed in water, in which three distinct reaction stages are identified. The initial stage involves the formation of an [Al7(μ3-OH)6(μ2-OH)6(H2O)12]9+ cluster core as an important intermediate toward the flat Al13 aqueous cluster. PMID:24167254

One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution.

PubMed

Yang, Xiaoming; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

2014-10-17

Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV-vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg(2+) on the basis of the interactions between Hg(2+) and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg(2+) in a linear range of 1.0×10(-7) mol L(-1)×10(-3) mol L(-1), with a detection limit of 2.4×10(-8) mol L(-1) at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

NASA Astrophysics Data System (ADS)

Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

2016-08-01

Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

PubMed Central

Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

2016-01-01

Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size. PMID:27476577

Metal-Folded Single-Chain Nanoparticle: Nanoclusters and Self-Assembled Reduction-Responsive Sub-5-nm Discrete Subdomains.

PubMed

Cao, Hui; Cui, Zhigang; Gao, Pan; Ding, Yi; Zhu, Xuechao; Lu, Xinhua; Cai, Yuanli

2017-09-01

Easy access to discrete nanoclusters in metal-folded single-chain nanoparticles (metal-SCNPs) and independent ultrafine sudomains in the assemblies via coordination-driven self-assembly of hydrophilic copolymer containing 9% imidazole groups is reported herein. 1 H NMR, dynamic light scattering, and NMR diffusion-ordered spectroscopy results demonstrate self-assembly into metal-SCNPs (>70% imidazole-units folded) by neutralization in the presence of Cu(II) in water to pH 4.6. Further neutralization induces self-assembly of metal-SCNPs (pH 4.6-5.0) and shrinkage (pH 5.0-5.6), with concurrent restraining residual imidazole motifs and hydrophilic segment, which organized into constant nanoparticles over pH 5.6-7.5. Atomic force microscopy results evidence discrete 1.2 nm nanoclusters and sub-5-nm subdomains in metal-SCNP and assembled nanoparticle. Reduction of metal center using sodium ascorbate induces structural rearrangement to one order lower than the precursor. Enzyme mimic catalysis required media-tunable discrete ultrafine interiors in metal-SCNPs and assemblies have hence been achieved. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low-Dimensional Nanomaterials as Active Layer Components in Thin-Film Photovoltaics

NASA Astrophysics Data System (ADS)

Shastry, Tejas Attreya

Thin-film photovoltaics offer the promise of cost-effective and scalable solar energy conversion, particularly for applications of semi-transparent solar cells where the poor absorption of commercially-available silicon is inadequate. Applications ranging from roof coatings that capture solar energy to semi-transparent windows that harvest the immense amount of incident sunlight on buildings could be realized with efficient and stable thin-film solar cells. However, the lifetime and efficiency of thin-film solar cells continue to trail their inorganic silicon counterparts. Low-dimensional nanomaterials, such as carbon nanotubes and two-dimensional metal dichalcogenides, have recently been explored as materials in thin-film solar cells due to their exceptional optoelectronic properties, solution-processability, and chemical inertness. Thus far, issues with the processing of these materials has held back their implementation in efficient photovoltaics. This dissertation reports processing advances that enable demonstrations of low-dimensional nanomaterials in thin-film solar cells. These low-dimensional photovoltaics show enhanced photovoltaic efficiency and environmental stability in comparison to previous devices, with a focus on semiconducting single-walled carbon nanotubes as an active layer component. The introduction summarizes recent advances in the processing of carbon nanotubes and their implementation through the thin-film photovoltaic architecture, as well as the use of two-dimensional metal dichalcogenides in photovoltaic applications and potential future directions for all-nanomaterial solar cells. The following chapter reports a study of the interaction between carbon nanotubes and surfactants that enables them to be sorted by electronic type via density gradient ultracentrifugation. These insights are utilized to construct of a broad distribution of carbon nanotubes that absorb throughout the solar spectrum. This polychiral distribution is then shown

Inkjet printed circuits based on ambipolar and p-type carbon nanotube thin-film transistors

PubMed Central

Kim, Bongjun; Geier, Michael L.; Hersam, Mark C.; Dodabalapur, Ananth

2017-01-01

Ambipolar and p-type single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) are reliably integrated into various complementary-like circuits on the same substrate by inkjet printing. We describe the fabrication and characteristics of inverters, ring oscillators, and NAND gates based on complementary-like circuits fabricated with such TFTs as building blocks. We also show that complementary-like circuits have potential use as chemical sensors in ambient conditions since changes to the TFT characteristics of the p-channel TFTs in the circuit alter the overall operating characteristics of the circuit. The use of circuits rather than individual devices as sensors integrates sensing and signal processing functions, thereby simplifying overall system design. PMID:28145438

Inkjet printed circuits based on ambipolar and p-type carbon nanotube thin-film transistors

NASA Astrophysics Data System (ADS)

Kim, Bongjun; Geier, Michael L.; Hersam, Mark C.; Dodabalapur, Ananth

2017-02-01

Ambipolar and p-type single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) are reliably integrated into various complementary-like circuits on the same substrate by inkjet printing. We describe the fabrication and characteristics of inverters, ring oscillators, and NAND gates based on complementary-like circuits fabricated with such TFTs as building blocks. We also show that complementary-like circuits have potential use as chemical sensors in ambient conditions since changes to the TFT characteristics of the p-channel TFTs in the circuit alter the overall operating characteristics of the circuit. The use of circuits rather than individual devices as sensors integrates sensing and signal processing functions, thereby simplifying overall system design.

A generalized electrochemical aggregative growth mechanism.

PubMed

Ustarroz, Jon; Hammons, Joshua A; Altantzis, Thomas; Hubin, Annick; Bals, Sara; Terryn, Herman

2013-08-07

The early stages of nanocrystal nucleation and growth are still an active field of research and remain unrevealed. In this work, by the combination of aberration-corrected transmission electron microscopy (TEM) and electrochemical characterization of the electrodeposition of different metals, we provide a complete reformulation of the Volmer-Weber 3D island growth mechanism, which has always been accepted to explain the early stages of metal electrodeposition and thin-film growth on low-energy substrates. We have developed a Generalized Electrochemical Aggregative Growth Mechanism which mimics the atomistic processes during the early stages of thin-film growth, by incorporating nanoclusters as building blocks. We discuss the influence of new processes such as nanocluster self-limiting growth, surface diffusion, aggregation, and coalescence on the growth mechanism and morphology of the resulting nanostructures. Self-limiting growth mechanisms hinder nanocluster growth and favor coalescence driven growth. The size of the primary nanoclusters is independent of the applied potential and deposition time. The balance between nucleation, nanocluster surface diffusion, and coalescence depends on the material and the overpotential, and influences strongly the morphology of the deposits. A small extent of coalescence leads to ultraporous dendritic structures, large surface coverage, and small particle size. Contrarily, full recrystallization leads to larger hemispherical monocrystalline islands and smaller particle density. The mechanism we propose represents a scientific breakthrough from the fundamental point of view and indicates that achieving the right balance between nucleation, self-limiting growth, cluster surface diffusion, and coalescence is essential and opens new, exciting possibilities to build up enhanced supported nanostructures using nanoclusters as building blocks.

A molecular beacon based on DNA-templated silver nanoclusters for the highly sensitive and selective multiplexed detection of virulence genes.

PubMed

Han, Dan; Wei, Chunying

2018-05-01

In this work, we develop a fluorescent molecular beacon based on the DNA-templated silver nanoclusters (DNA-Ag NCs). The skillfully designed molecular beacon can be conveniently used for detection of diverse virulence genes as long as the corresponding recognition sequences are embedded. Importantly, the constructed detection system allows simultaneous detection of multiple nucleic acids, which is attributed to non-overlapping emission spectra of the as-synthesized silver nanoclusters. Based on the target-induced fluorescence enhancement, three infectious disease-related genes HIV, H1N1, and H5N1 are detected, and the corresponding detection limits are 3.53, 0.12 and 3.95nM, respectively. This design allows specific, versatile and simultaneous detection of diverse targets with easy operation and low cost. Copyright © 2017 Elsevier B.V. All rights reserved.

Photoinduced relaxation dynamics of nitrogen-capped silicon nanoclusters: a TD-DFT study

NASA Astrophysics Data System (ADS)

Liu, Xiang-Yang; Xie, Xiao-Ying; Fang, Wei-Hai; Cui, Ganglong

2018-04-01

Herein we have developed and implemented a TD-DFT-based surface-hopping dynamics simulation method with a recently proposed numerical algorithm capable of efficiently computing nonadiabatic couplings, a semiclassical spectrum simulation method, and an excited-state character analysis method based on one-electron transition density matrix. With the use of these developed methods, we have studied the spectroscopic properties, excited-state characters, and photoinduced relaxation dynamics of three silicon nanoclusters capped with different chromophores (Cl@SiQD, Car@SiQD, Azo@SiQD). Spectroscopically, the main absorption peak is visibly red-shifted from Cl@SiQD via Car@SiQD to Azo@SiQD. In contrast to Cl@SiQD and Car@SiQD, there are two peaks observed in Azo@SiQD. Mechanistically, the excited-state relaxation to the lowest S1 excited singlet state is ultrafast in Cl@SiQD, which is less than 190 fs and without involving excited-state trapping. In comparison, there are clear excited-state trappings in Car@SiQD and Azo@SiQD. In the former, the S2 state is trapped more than 300 fs; in the latter, the S3 excited-state trapping is more than 615 fs. These results demonstrate that the interfacial interaction has significant influences on the spectroscopic properties and excited-state relaxation dynamics. The knowledge gained in this work could be helpful for the design of silicon nanoclusters with better photoluminescence performance.

PET and NIR Optical Imaging Using Self-Illuminating 64Cu-Doped Chelator-Free Gold Nanoclusters

PubMed Central

Hu, Hao; Huang, Peng; Weiss, Orit Jacobson; Yan, Xuefeng; Yue, Xuyi; Zhang, Molly Gu; Tang, Yuxia; Nie, Liming; Ma, Ying; Niu, Gang; Wu, Kaichun; Chen, Xiaoyuan

2014-01-01

Self-illuminating fluorescence imaging without autofluorescence background interference has recently aroused more research interests in molecular imaging. Currently, only a few self-illuminating probes were developed, based mainly on toxic quantum dots such as CdSe, CdTe. Herein, we report a novel design of nontoxic self-illuminating gold nanocluster (64Cu-doped AuNCs) for dual-modality positron emission tomography (PET) and near-infrared (NIR) fluorescence imaging based on Cerenkov resonance energy transfer (CRET). PET radionuclide 64Cu was introduced by a chelator-free doping method, which played dual roles as the energy donor and the PET imaging source. Meanwhile, AuNCs acted as the energy acceptor for NIR fluorescence imaging. 64Cu-doped AuNCs exhibited efficient CRET-NIR and PET imaging both in vitro and in vivo. In a U87MG glioblastoma xenograft model, 64Cu-doped AuNCs showed high tumor uptake (14.9%ID/g at 18 h) and produced satisfactory tumor self-illuminating NIR images in the absence of external excitation. This self-illuminating nanocluster with non-toxicity and good biocompatibility can be employed as a novel imaging contrast agent for biomedical applications, especially for molecular imaging. PMID:25224367

PET and NIR optical imaging using self-illuminating (64)Cu-doped chelator-free gold nanoclusters.

PubMed

Hu, Hao; Huang, Peng; Weiss, Orit Jacobson; Yan, Xuefeng; Yue, Xuyi; Zhang, Molly Gu; Tang, Yuxia; Nie, Liming; Ma, Ying; Niu, Gang; Wu, Kaichun; Chen, Xiaoyuan

2014-12-01

Self-illuminating fluorescence imaging without autofluorescence background interference has recently aroused more research interests in molecular imaging. Currently, only a few self-illuminating probes were developed, based mainly on toxic quantum dots such as CdSe, CdTe. Herein, we report a novel design of nontoxic self-illuminating gold nanocluster ((64)Cu-doped AuNCs) for dual-modality positron emission tomography (PET) and near-infrared (NIR) fluorescence imaging based on Cerenkov resonance energy transfer (CRET). PET radionuclide (64)Cu was introduced by a chelator-free doping method, which played dual roles as the energy donor and the PET imaging source. Meanwhile, AuNCs acted as the energy acceptor for NIR fluorescence imaging. (64)Cu-doped AuNCs exhibited efficient CRET-NIR and PET imaging both in vitro and in vivo. In a U87MG glioblastoma xenograft model, (64)Cu-doped AuNCs showed high tumor uptake (14.9 %ID/g at 18 h) and produced satisfactory tumor self-illuminating NIR images in the absence of external excitation. This self-illuminating nanocluster with non-toxicity and good biocompatibility can be employed as a novel imaging contrast agent for biomedical applications, especially for molecular imaging. Published by Elsevier Ltd.

Effects of Nitrogen Fertilization and Thinning Treatments on Subsurface Soil Carbon and Nitrogen

NASA Astrophysics Data System (ADS)

Gross, C. D.; James, J. N.; Harrison, R. B.

2016-12-01

Increases in intensively managed forest plantations have caused concern for the long-term productivity and sustainability of these stands, as decreased organic matter retention and shorter rotations can substantially impact soil nutrition both in the short- and long-term. This study aims to provide data for regional responses of soil carbon (C) and nitrogen (N) by depth to fertilization and thinning treatments. Soil was sampled at an intensively managed Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation in northwestern Oregon, USA. Nine 0.2-ha plots were sampled with at least three pits per plot. Management regimes included no treatment (control), fertilization (F+), minimal thinning (mT), repeated thinning (rT), and combination treatments (mTF+ and rTF+). Fertilized plots received a total of 1120 kg N ha-1 as urea over 16 years. Bulk density and chemical analysis samples were taken in the middle of succeeding soil layers at depths of 0.1, 0.2, 0.5, 1.0, and 1.5 m. Forest floor samples were collected from a randomly placed quadrat. Preliminary results show an increase in total soil C and N of 113 and 106%, respectively, on the mTF+ plot compared to a control plot. The subsoil, defined here as below 0.2 m, contained over 50% of both soil C and N on the mTF+ plot and experienced greater C and N increases than the surface soil following treatment. This study demonstrates that forest management practices over a relatively short time span (<30 years) can significantly alter subsoil, which comprises a substantial portion of biologically available C and N in terrestrial ecosystems. Subsoil processes are critical to our understanding of changes in soil quality and our ability to accurately assess changes in soil C and N reservoirs.

Fully Screen-Printed, Large-Area, and Flexible Active-Matrix Electrochromic Displays Using Carbon Nanotube Thin-Film Transistors.

PubMed

Cao, Xuan; Lau, Christian; Liu, Yihang; Wu, Fanqi; Gui, Hui; Liu, Qingzhou; Ma, Yuqiang; Wan, Haochuan; Amer, Moh R; Zhou, Chongwu

2016-11-22

Semiconducting single-wall carbon nanotubes are ideal semiconductors for printed electronics due to their advantageous electrical and mechanical properties, intrinsic printability in solution, and desirable stability in air. However, fully printed, large-area, high-performance, and flexible carbon nanotube active-matrix backplanes are still difficult to realize for future displays and sensing applications. Here, we report fully screen-printed active-matrix electrochromic displays employing carbon nanotube thin-film transistors. Our fully printed backplane shows high electrical performance with mobility of 3.92 ± 1.08 cm 2 V -1 s -1 , on-off current ratio I on /I off ∼ 10 4 , and good uniformity. The printed backplane was then monolithically integrated with an array of printed electrochromic pixels, resulting in an entirely screen-printed active-matrix electrochromic display (AMECD) with good switching characteristics, facile manufacturing, and long-term stability. Overall, our fully screen-printed AMECD is promising for the mass production of large-area and low-cost flexible displays for applications such as disposable tags, medical electronics, and smart home appliances.

EXAFS and XANES investigation of (Li, Ni) codoped ZnO thin films grown by pulsed laser deposition.

PubMed

Mino, Lorenzo; Gianolio, Diego; Bardelli, Fabrizio; Prestipino, Carmelo; Senthil Kumar, E; Bellarmine, F; Ramanjaneyulu, M; Lamberti, Carlo; Ramachandra Rao, M S

2013-09-25

Ni doped, Li doped and (Li, Ni) codoped ZnO thin films were successfully grown using a pulsed laser deposition technique. Undoped and doped ZnO thin films were investigated using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES). Preliminary investigations on the Zn K-edge of the undoped and doped ZnO thin films revealed that doping has not influenced the average Zn-Zn bond length and Debye-Waller factor. This shows that both Ni and Li doping do not appreciably affect the average local environment of Zn. All the doped ZnO thin films exhibited more than 50% of substitutional Ni, with a maximum of 77% for 2% Ni and 2% Li doped ZnO thin film. The contribution of Ni metal to the EXAFS signal clearly reveals the presence of Ni clusters. The Ni-Ni distance in the Ni(0) nanoclusters, which are formed in the film, is shorter with respect to the reference Ni metal foil and the Debye-Waller factor is higher. Both facts perfectly reflect what is expected for metal nanoparticles. At the highest doping concentration (5%), the presence of Li favors the growth of a secondary NiO phase. Indeed, 2% Ni and 5% Li doped ZnO thin film shows %Nisub = 75 ± 11, %Nimet = 10 ± 8, %NiO = 15 ± 8. XANES studies further confirm that the substitutional Ni is more than 50% in all the samples. These results explain the observed magnetic properties.

SERS activity of Ag decorated nanodiamond and nano-β-SiC, diamond-like-carbon and thermally annealed diamond thin film surfaces.

PubMed

Kuntumalla, Mohan Kumar; Srikanth, Vadali Venkata Satya Siva; Ravulapalli, Satyavathi; Gangadharini, Upender; Ojha, Harish; Desai, Narayana Rao; Bansal, Chandrahas

2015-09-07

In the recent past surface enhanced Raman scattering (SERS) based bio-sensing has gained prominence owing to the simplicity and efficiency of the SERS technique. Dedicated and continuous research efforts have been made to develop SERS substrates that are not only stable, durable and reproducible but also facilitate real-time bio-sensing. In this context diamond, β-SiC and diamond-like-carbon (DLC) and other related thin films have been promoted as excellent candidates for bio-technological applications including real time bio-sensing. In this work, SERS activities of nanodiamond, nano-β-SiC, DLC, thermally annealed diamond thin film surfaces were examined. DLC and thermally annealed diamond thin films were found to show SERS activity without any metal nanostructures on their surfaces. The observed SERS activities of the considered surfaces are explained in terms of the electromagnetic enhancement mechanism and charge transfer resonance process.