Cysteine-assisted growth of silver on gold nanorods

Au–Ag core–shell (Au@Ag) nanobars could be synthesized from gold nanorod (NR) seeds with cysteine additives by a two-step process of reaction temperatures. The lateral sides of gold NRs surrounded by surfactant bilayers render cysteine additives binding on both ends of the NRs, and restricted silver deposition to their lateral sides at room temperature. Further, silver deposition can take place at first on the pre-formed silver layers on the lateral sides at higher temperatures and finally resulted in the formation of Au@Ag nanobars in which gold NRs are in the corner positions of the nanobars and their longitudinal axes parallel to the longer sides of the nanobars.     

Production of double-sided targets by electrodeposition: initial evaluation and optimization of performance

The Detector for Advanced Neutron Capture Experiments (DANCE) located at the Los Alamos Neutron Science Center is used to perform neutron capture cross-section measurements on radioactive and non-radioactive isotopes. Thin actinide targets for the DANCE detector are typically prepared by molecular deposition on thin titanium foils. For the preparation of double-sided deposits, a Teflon electrodeposition cell was constructed with two liquid chambers with a foil substrate in between, allowing electrodeposition on both sides of the foil. We have been studying the electrodeposition of uranium from isopropyl alcohol solutions using this cell. Effects of acid composition, uranium concentration, current, and deposition time will be described.     

Magnetically Enhanced 15 kHz Glow Discharge of Methane

This work deals with the luminous chemical vapour deposition (plasma polymerization) of hydrocarbon polymeric thin films in a magnetic field enhanced discharge of methane. The films were deposited on 4″ <111> single crystal silicon substrates. We investigated the influence of the different glow discharge parameters (e.g. pressure, flow rate, power input, etc.) on the deposition rate of methane and the refractive index of the resulting polymeric films, as well as the distribution of these parameters across the wafer. We used a Shinko Seiki Plasma Polymerization equipment with a bell jar reactor comprising two electrodes connected to a symmetric AC power supply of 15 kHz. Two magnetrons were formed by placing two circular shaped concentric magnetic poles behind each electrode. The substrates were attached on both sides of a rotating wheel held at a floating potential in the middle of the two electrodes. This equipment allowed us to vary a single parameter and keep the other parameters constant over the whole process. We measured the thickness and the refractive index and their distribution over the wafer. The effect of the system pressure, decoupled from the effect of flow rate, is explained by the characteristic nature of luminous gas phase and by the polymerization/deposition mechanism of luminous chemical vapour deposition.     

Vapor phase self-assembly of electrooptic thin films via triple hydrogen bonds

The donor-acceptor pi-electron chromophore 5-{4-[2-(4,6-diamino-[1,3,5]triazin-2-yl)-vinyl]-benzylidene}-pyrimidine-2,4,6-trione (DTPT) was designed and synthesized. Triple H-bonding interactions between neighboring molecules direct self-assembled chromophore alignment in a head-to-tail orientation using a straightforward vapor phase deposition process. Angle-dependent SHG interference patterns and the quadratic dependence of the 532 nm light output intensity on the thickness of the DTPT films for glass substrates coated on both sides demonstrate high, reproducible film quality and uniformity. XRD also demonstrates long-range order in the film and yields a molecular tilt angle in good agreement with polarized SHG data, clearly showing that out-of-plane ordering of chromophore molecules has been achieved.     

Progress on the development of uniform distributed Pd electroless based catalysts on MEA for PEMFC application

Envisaging the scale-up production of fuel cell electrodes, it was established an electrode manufacturing method that enables a uniform distribution of Pd-based catalyst over the MEA, ensuring simultaneously a low catalyst loading. The new procedure relies on the direct immobilization of the catalyst on the gas diffusion substrate by the electroless deposition after substrate activation by the electrodeposition of metal nucleus of Pd using the galvanostatic mode. The effect of the novel method on the catalyst distribution uniformity, morphology, and electrocatalytic activity towards the oxygen reduction reaction (ORR) in 0.1 M HClO₄ solution is compared to samples prepared by the conventional Sn/Pd sensitization—activation route. The performance of the PEMFC containing the same Pd load (0.09 mg cm^?2) reveals to be slightly higher on depositing the Pd nucleus by the galvanostatic electrodeposition than by the conventional sensitization/activation method. The new method opens up new approaches to extend the electroless deposition to the preparation of a wide range of alloy catalysts for the cathode and anode sides of PEMFCs.     

Microscopic and electronic structure of semimetallic Sb and Semiconducting AlSb fabricated by nanoscale electrodeposition: An in situ scanning probe investigation

The nanoscale electrocrystallization of pure Sb and the compound semiconductor AlSb on Au(111) has been studied by in situ scanning probe techniques (STM and STS) employing an ionic liquid electrolyte, {AlCl3-[C4mim]+Cl-} (1:1) containing SbCl3. The characteristic changes of the electronic structures with varying potentials have been probed for the first time by normalized differential conductance spectra, (dI/dU)/(I/U). In the underpotential deposition range of Sb the formation of two layers is observed. For the first monolayer a (square root 3 x square root 3)R30 degrees structure is determined from atomically resolved STM images. During the deposition and dissolution of the Sb monolayers characteristic wormlike or spinodal structures appear indicating surface alloying of antimony with the gold substrate. Under overpotential conditions two different Sb structures have been observed. If the deposition potential is continuously stepped to -0.1 V, Sb nanostripes form. On the other hand, randomly dispersed small clusters occur if the potential is jumped from 0.0 to -0.3 V vs Al/Al(III). Both modifications exhibit typical semimetallic behavior as shown by the STS spectra. At -1.1 V the cyclic voltammogram shows a clear reduction wave that is assigned to AlSb compound formation. Deposits in this potential range are characterized by a homogeneous distribution of clusters with diameters of approximately 20 nm. Conductance spectra of these clusters exhibit the main features of the electronic structure of the bulk semiconductor AlSb, with a band gap of 2.0 +/- 0.2 eV. Electrodeposition experiments on both sides of the compound deposition potential show a strong doping effect that is manifest in the corresponding conductance spectra.     

Experimental and theoretical study of a surface stabilized monolayer phase of nickel oxide on Pd(100)

A surface stabilized monolayer phase of nickel oxide, c(4 x 2)-Ni(3)O(4), has been found to grow epitaxially under reactive deposition conditions on Pd(100), in the presence of other adsorbed phases and in competition with them. High-quality scanning tunneling microscopy data are reported and discussed, including a detailed analysis of the defects and of the border morphology of this new phase. The data are discussed in the light of ab initio simulations of the electronic, energetic, and geometric properties of such a phase. A hybrid-exchange density functional theory approach has been used, and a slab model is adopted where palladium is simulated by a thin film covered on both sides by regular epilayers. A growth model has been developed that explains both the unusual stoichiometry of the phase and the observed defects.     

Evolution of pore size distribution and average pore size of porous ceramic membranes during modification by counter-diffusion chemical vapor deposition

The modification of porous ceramic membranes by counter-diffusion chemical vapor deposition (CVD) is studied theoretically and experimentally. Numerical simulations of the evolution of the membrane permeance, average pore size and pore size distribution as a function of extent of modification are presented and compared with experimetal data. It is found that the change of the average pore size of the membranes after modification strongly depends on the initial pore size distribution of the membrane, CVD reaction kinetics and characterization method. Experimental data suggest that CVD of zirconia (and yttria) inside porous ceramic membranes by reaction of zirconium (and yttrium) chlorides with steam/air at elevated temperatures proceeds by quasi-zero reaction kinetics with respect to the oxidant, typical of non-stoichiometric supply of the reactants from opposite sides of the membrane. Under such conditions, CVD modification may result in a modest increase of the average pore size of coarse-pore ceramic membranes as suggested by numerical calculations and experimental data.     

Design of Clayware Separator-Electrode Assembly for Treatment of Wastewater in Microbial Fuel Cells

Performance of six different microbial fuel cells (MFCs) made from baked clayware, having 450 ml effective anodic chamber volume, was evaluated, with different configurations of separator electrode assemblies, to study the feasibility of bioelectricity generation and high-strength wastewater treatment in a single-chambered mediator-less air-cathode MFC. Superior performance of an air-cathode MFC (ACMFC) with carbon coating on both sides of the separator was observed over an aqueous cathode MFC, resulting in a maximum volumetric power of 4.38 W m^?3 and chemical oxygen demand (COD) removal efficiency of more than 90 % in a batch cycle of 4 days. Hydrophilic polymer polyvinyl alcohol (PVA) was successfully used as a binder. The problem of salt deposition and fouling of cathode could be minimized by using a sock net current collector, replacing the usual stainless steel wire. However, electrolyte loss due to evaporation is a problem that needs to be resolved for better performance of an ACMFC.     

Multiple flow profiles for two-phase flow in single microfluidic channels through site-selective channel coating

An approach to control two-phase flow systems in a poly(dimethylsiloxane) (PDMS) microfluidic device using spatially selective surface modification is demonstrated. Side-by-side flows of ethanol?:?water solutions containing different polymers are used to selectively modify both sides of a channel by laminar flow patterning. Introduction of air pockets during modification allows for control over the length of the channel section that is modified. This approach makes it possible to achieve slug flow and side-by-side flow of water : 1-octanol simultaneously within the same PDMS channel, without the need of additional structural elements. A key finding is that conditioning of the PDMS channels with 1-octanol before polymer deposition is crucial to achieving stable side-by-side flows.     

Charge injection into disordered molecular films

Light‐emitting devices made by organic or inorganic dielectric films placed between two metal electrodes emit light because of the radiative recombination of positive and negative charge carriers entering the dielectric from the anode and cathode sides, respectively, under applied voltage. Standard vapor‐deposition technology of the device construction suggests the remarkable disordering at the metal dielectric interface and in the structure of dielectric film. The structural imperfections strongly affect carrier injection and transport, device efficiency, performance, and stability. In this article we describe the effect of disordering on the injection current through the dielectric layer and discuss the implications for the device performance. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2601–2621, 2003     

Facial fabrication of superhydrophobic cellulose film with hierarchical morphologies

Hierarchical CuO spheres were firstly grown on the surface of cellulose film, and then stearic acid (STA) was utilized to decrease surface energy. The cupric ions fixed on the cellulose film transferred to one side and reacted with STA forming cupric stearates. The cupric stearates then self-assembled into nanobelts/nanoribbons and spread over the film, which induces to form hierarchical morphologies. Both sides of CuO modified film are black and superhydrophilic in air; after modification with STA, the film becomes superhydrophobic for both sides, whereas one side is blue and the other side is black showing different morphologies. Water contact angles (WCAs) of the superhydrophobic film for both black and blue sides are 153.9 ± 0.6° and 153.5 ± 0.8°, respectively. Sliding angles (SAs) for both sides are lower than 9.5°, indicating non-sticking superhydrophobic state. More importantly, the superhydrophobic cellulose–CuO–STA film is still superhydrophobic under hydrodynamic impact or pH of 3–11.     

Pt-V2O5/HM催化剂积炭机理的TPO研究

Ｐｔ┐Ｖ２Ｏ５／ＨＭ催化剂积炭机理的ＴＰＯ研究蔡炳新（湖南大学化学化工系，长沙４１００１２）周烈华郑小明（杭州大学催化研究所，杭州３１００２８）关键词铂，五氧化二钒，氢型丝光沸石，程序升温氧化酸性载体Ｐｔ系贵金属双功能催化剂表面积炭是导致其催化性能衰...     

Influence of solution chemistry on the deposition and detachment kinetics of RNA on silica surfaces

The deposition kinetics of RNA extracted from both virus and bacteria on silica surfaces were examined in both monovalent (NaCl) and divalent (CaCl(2)) solutions under a wide range of environmentally relevant ionic strength and pH conditions by utilizing a quartz crystal microbalance with dissipation (QCM-D). To better understand the RNA deposition mechanisms, QCM-D data were complemented by diffusion coefficients and zeta potentials of RNA as a function of examined solution chemistry conditions. Favorable deposition of RNA on poly-l-lysine-coated (positively charged) silica surfaces was governed by the convective-diffusive transport of RNA to the surfaces. The deposition kinetics of RNA on bare silica surfaces were controlled by classic Derjaguin-Landau-Verwey-Overbeek (DLVO) interactions. The presence of divalent cations (Ca(2+)) in solutions greatly enhanced the deposition kinetics of RNA on silica surfaces. Solution pH also affected the deposition behavior of RNA on silica surfaces. Release experiments showed that detachment of RNA from silica surfaces was significant in NaCl solutions, whereas, the deposited RNA on silica surfaces in CaCl(2) solutions was more likely to be irreversible.     

Electrochemical oxidation of aniline on the surface of an amorphous metal alloy Al87Ni8Y5

The oxidation of aniline is studied by the potentiodynamic method on an electrode of an amorphous metallic alloy Al₈₇Ni₈Y₅ and the results are compared with the analogous data on a polycrystalline aluminum electrode. The aniline oxidation and, correspondingly, the polyaniline deposition are shown to proceed more actively on the contact side of the amorphous metal alloy Al₈₇Ni₈Y₅ electrode. The morphology of synthesized polyaniline films is studied on both sides of the working electrode. It is found that the polyaniline layer structure is to the large extent granulated on the contact side and smooth on the external side.     

Deposition of polymer latices on grafted Nylon 6 fiber

Deposition of polymer latices on a grafted Nylon 6 fiber was studied as a function of pH and the degree of grafting. The latices were polystyrene (PS), styrene/acrylamide copolymer (P(St/AAm)) and styrene/acrylic acid copolymer (P(St/AA)). The deposition of the latices on the grafted fiber decreased in every case with increasing pH and no deposition was observed at alkaline pH. The grafting of fiber with acrylic and methacrylic acid reduced the deposition of P(St/AAm) and P(St/AA) latices but had no influence on the deposition of PS latex. The relation between the deposition rates and the interaction energy at acidic pH indicates that the deposition of PS latex on the grafted fiber mainly depends on the electrostatic interaction. These results suggest that the expansion of water-soluble polyelectrolyte layer on the surface of grafted fiber plays an important role on the deposition.     

Matrix Isolation-Vibrational Circular Dichroism Spectroscopic Study of Conformations and Non-Covalent Interactions of Tetrahydro-2-Furoic Acid

The conformational landscape and aggregation behaviour of tetrahydro-2-furoic acid (THFA) were investigated by using matrix isolation-vibrational circular dichroism (MI-VCD). The well-resolved experimental MI-IR and MI-VCD features in an argon matrix at 10 K allow one to identify two dominant monomeric conformations as trans-THFA where the hydroxyl and carbonyl groups of COOH are at opposite sides, as well as one cis-conformer. At 24 K and 30 K deposition temperatures, the experimental IR and VCD spectral features reveal further growth of the binary THFA aggregates. Systematic conformational searches identified three vastly different binary binding topologies, resulting in a few hundred stable (THFA)₂ conformers. Interestingly, the main binary structures observed correspond to an unusual type of structure which is made of two trans-THFA subunits, in contrast to the usual double H-bonded ring binary structures, identified in a previous solution study. The present work showcases the power of MI-VCD spectroscopy in revealing unusual structures formed in a cold rare gas matrix.     

Influence of natural organic matter on the deposition kinetics of extracellular polymeric substances (EPS) on silica

The influence of humic acid and alginate, two major components of natural organic matter (NOM), on deposition kinetics of extracellular polymeric substances (EPS) on silica was examined in both NaCl and CaCl(2) solutions over a wide range of environmentally relevant ionic strengths utilizing a quartz crystal microbalance with dissipation. Deposition kinetics of both soluble EPS and bound EPS extracted from four bacterial strains with different characteristics was investigated. EPS deposition on humic acid-coated silica surfaces was found to be much lower than that on bare silica surfaces under all examined conditions. In contrast, pre-coating the silica surfaces with alginate enhanced EPS deposition in both NaCl and CaCl(2) solutions. More repulsive electrostatic interaction between EPS and surface contributed to the reduced EPS deposition on humic acid-coated silica surface. The trapping effect induced by the rough alginate layer resulted in the greater EPS deposition on alginate-coated surfaces in NaCl solutions, whereas surface heterogeneities on alginate layer facilitated favorable interactions with EPS in CaCl(2) solutions. The presence of dissolved background humic acid and alginate in solutions both significantly retarded EPS deposition on silica surfaces due to the greater steric and electrostatics repulsion.     

In situ growth of CuS thin films on functionalized self-assembled monolayers using chemical bath deposition

Nano-structured CuS thin films were deposited on the functionalized -NH(2)-terminated self-assembled monolayers (SAMs) surface by chemical bath deposition (CBD). The deposition mechanism of CuS on the -NH(2)-terminated group was systematically investigated using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS), UV-vis absorption. The optical, electrical and photoelectrochemical performance of CuS thin films incorporating with the X-ray diffraction (XRD) analysis confirmed the nanocrystalline nature of CuS with hexagonal crystal structure and also revealed that CuS thin film is a p-type semiconductor with high electrical conductivity (12.3Ω/□). The functionalized SAMs terminal group plays a key role in the deposition of CuS thin films. The growth of CuS on the varying SAMs surface shows different deposition mechanisms. On -NH(2)-terminated surfaces, a combination of ion-by-ion growth and cluster-by-cluster deposition can interpret the observed behavior. On -OH- and -CH(3)-terminated surfaces, the dominant growth mechanism on the surface is cluster-by-cluster deposition in the solution. According to this principle, the patterned CuS microarrays with different feature sizes were successfully deposited on -NH(2)-terminated SAMs regions of -NH(2)/-CH(3) patterned SAMs surface.     

Polymerization of para-xylylene derivatives (parylene polymerization). I. Deposition kinetics for parylene N and parylene C

Kinetic aspects of parylene N [unsubstituted poly(para-xylylene)] and Parylene C [monochlorosubstituted poly(para-xylylene)] were studied. The conversion of starting material (dimer of either p-xylylene or chloro-para-xylylene) to polymer is quantitative (ca. 100%). Consequently, the total polymer formed in a closed system is directly proportional to the amount of dimer charged. However, the percentage of the total amount of polymer formed which deposits on substrate surfaces, placed in the deposition chamber, as well as the polymer film growth rate are dependent on operational factors such as the temperature of the substrate, sublimation of dimer temperature, flow pattern of the reactive species, etc. Parylene C, being a heavier and more polar molecule, has the tendency to deposit easily in the deposition chamber compared to the deposition of Parylene N. Parylene C also has a higher ceiling temperature for deposition than Parylene N. This situation has been investigated from the viewpoint of excess thermal energy which hinders polymer formation (deposition) due to the exceedingly high entropy change necessary for polymer deposition to occur. The addition of a cool (i.e., room temperature) inert gas was shown to increase the deposition of Parylene N on substrate surfaces placed in the deposition chamber. The deposition increase and acceleration of deposition (film growth) rate were found to be related to the size and molecular weight of the inert gas pressure maintained in the system. The accelerating effect is explained by the increase in third-body collisions to dissipate the excess thermal energy of the reactive species.