On partially absorbing layers and interference

The complex reflection and transmission coefficients of partially absorbing layers cannot be manipulated independently. The restrictions are evaluated by considering the layer as a beam splitter in an interferometric configuration and requiring the conservation of energy. It is also shown that interference effects can reduce the absorption in an absorbing beam splitter and, under certain conditions, absorption can be eliminated completely.     

Multistate resistive switching in silver nanoparticle films

Resistive switching devices have garnered significant consideration for their potential use in nanoelectronics and non-volatile memory applications. Here we investigate the nonlinear current–voltage behavior and resistive switching properties of composite nanoparticle films comprising a large collective of metal–insulator–metal junctions. Silver nanoparticles prepared via the polyol process and coated with an insulating polymer layer of tetraethylene glycol were deposited onto silicon oxide substrates. Activation required a forming step achieved through application of a bias voltage. Once activated, the nanoparticle films exhibited controllable resistive switching between multiple discrete low resistance states that depended on operational parameters including the applied bias voltage, temperature and sweep frequency. The films’ resistance switching behavior is shown here to be the result of nanofilament formation due to formative electromigration effects. Because of their tunable and distinct resistance states, scalability and ease of fabrication, nanoparticle films have a potential place in memory technology as resistive random access memory cells.     

Multistate resistive switching in silver nanoparticle films

Abstract

Resistive switching devices have garnered significant consideration for their potential use in nanoelectronics and non-volatile memory applications. Here we investigate the nonlinear current–voltage behavior and resistive switching properties of composite nanoparticle films comprising a large collective of metal–insulator–metal junctions. Silver nanoparticles prepared via the polyol process and coated with an insulating polymer layer of tetraethylene glycol were deposited onto silicon oxide substrates. Activation required a forming step achieved through application of a bias voltage. Once activated, the nanoparticle films exhibited controllable resistive switching between multiple discrete low resistance states that depended on operational parameters including the applied bias voltage, temperature and sweep frequency. The films’ resistance switching behavior is shown here to be the result of nanofilament formation due to formative electromigration effects. Because of their tunable and distinct resistance states, scalability and ease of fabrication, nanoparticle films have a potential place in memory technology as resistive random access memory cells.     

Mechanism study of silver nanoparticle production using Neurospora intermedia

Elucidation of the molecular mechanism of silver nanoparticle (AgNP) synthesis is necessary to control nanoparticle size, shape, and monodispersity. In this study, the mechanism of AgNP formation by Neurospora intermedia was investigated. The higher production rate of AgNP formation using a culture supernatant heat‐treated at 100° and 121°C relative to that with an un‐treated culture supernatant indicated that the native form of the molecular species is not essential. The effect of the protein molecular weight (MW) on the nanoparticle size distribution and average size was studied by means of ultraviolet–visible spectroscopy and dynamic light scattering. Using un‐treated and concentrated cell‐free filtrate passed through 10 and 20 kDa cut‐off filters led to the production of AgNPs with average sizes of 25, 30, and 34 nm, respectively. Also, using the permeate fraction of cell‐free filtrate passed through a 100 kDa cut‐off filter led to the formation of the smallest nanoparticles with the narrowest size distribution (average size of 16 nm and polydispersity index of 0.18). Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis of the fungal extracellular proteins showed two notable bands with the MWs of 15 and 23 kDa that are involved in the reduction and stabilisation of the nanoparticles, respectively.Inspec keywords: silver, nanoparticles, nanofabrication, proteins, molecular weight, ultraviolet spectra, visible spectra, cellular biophysics, electrophoresis, molecular biophysicsOther keywords: Neurospora intermedia, molecular mechanism, silver nanoparticle synthesis, nanoparticle shape, nanoparticle monodispersity, AgNP formation, untreated culture supernatant, molecular species, protein molecular weight, MW, nanoparticle size distribution, ultraviolet‐visible spectroscopy, dynamic light scattering, untreated cell‐free filtrate, concentrated cell‐free filtrate, cut‐off filters, permeate fraction, polydispersity index, Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis, fungal extracellular proteins, nanoparticle reduction, nanoparticle stabilisation, temperature 100 degC, temperature 121 degC, size 25 nm, size 30 nm, size 34 nm, size 16 nm, Ag     

Fluorescence blinking dynamics of silver nanoparticle and silver nanorod films

Fluorescence blinking of silver nanoparticle films is observed when illuminated with red light (635?nm). The observed power-law off-time distribution is attributed to random surface diffusion and subsequent agglomeration of atomic Ag leading to the formation of photo-active Ag nanoclusters. These nanoclusters can in turn diffuse randomly to form non-emitting Ag clusters after aggregation with another Ag species. This is revealed in the power-law on-time distribution. Silver oxides found on the surfaces of Ag nanostructures are important for photoblinking to take place since nanostructures with a protective layer of polymeric citrate or cetyltrimethylammonium bromide (CTAB) against atmospheric O(2) do not display obvious emission intermittency.     

Production of silver ions from colloidal silver by nanoparticle iontophoresis system

Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion release application. For medical purposes, conversion of colloidal silver into an ionic form is necessary, but not using silver salts (e.g., AgNO3, Ag2SO4), due to the fact that the counter-ion of silver salts may cause problems to the body as the silver ion (Ag+) is consumed. The goal of this research is to develop a silver nanoparticle iontophoresis system (NIS) which can provide a relatively safe bactericidal silver ion solution with a controllable electric field. In this study, ion-selective electrodes were used to identify and observe details of the system's activity. Both qualitative and quantitative data analyses were performed. The experimental results show that the ion releasing peak time (R(PT)) has an inversely proportional relationship with the applied current and voltage. The ion releasing maximum level (R(ML)) and dosage (R(D)) are proportional to the current density and inversely proportional to the voltage, respectively. These results reveal that the nanoparticle iontophoresis system (NIS) is an alternative method for the controlled release of a metal ion and the ion's concentration profile, by controlling the magnitude of current density (1 microA/cm2 equal to 1 ppm/hour) and applied voltage.     

Experimental study of the thermal conductivity of weakly absorbing liquids in layers transparent to infrared radiation

The thermal conductivities of a number of organic liquids are determined by a transient method under irregular thermal conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 6, pp. 972–978, June, 1976.     

Parameters controlling silver nanoparticle growth in sol-gel silica coatings

Silica based sol-gel coatings doped with different silver amounts have been prepared. Apart from silver concentration, other experimental parameters such as thermal densification conditions, presence of other co-dopants and the nature of the substrate have been varied in order to determine their influence on the final microstructure and properties. Characterisation of the materials prepared was carried out by optical spectroscopy (photoluminescence and absorption), secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The study was oriented to determine the parameters governing the nucleation and growth of silver nanoparticles. The results showed that formation of silver nanoparticles was promoted when one or more of the following conditions were achieved: silver concentration in the initial sol over 5%, thermal densification under reducing atmosphere and use of pure silica substrate (in general, glass substrates without modifier ions and, therefore, with few non-bridging oxygen positions).     

Genetic algorithm for ellipsometric data inversion of absorbing layers

A new data reduction method is presented for single-wavelength ellipsometry. A genetic algorithm is applied to ellipsometric data to find the best fit. The sample consists of a single absorbing layer on a semi-infinite substrate. The genetic algorithm has good convergence and is applicable to many different problems, including those with different independent measurements and situations with more than two angles of incidence. Results are similar to those obtained by other inversion techniques.     

Synthesis of contamination-free silver nanoparticle suspensions for micro-interconnects

Silver nanoparticle suspensions synthesized by chemical reduction from silver nitrate in a formaldehyde reductant and PVP stabilizer using organic bases as the reaction promoter were studied in this research. Two different organic bases of different basicity, triethylamine and pyridine, were used in the reaction. The sizes of the silver particles prepared from the more basic triethylamine were around 20-30 nm. The particles made from the less basic pyridine had smaller sizes (10-20 nm). The suspensions of silver nanoparticles prepared by both methods are free from any metal ion contamination, and are suitable for use in semiconductor industry. The suspensions will be used to make micro-interconnects in integrated circuits (IC) devices by ink-jet printing.     

Plasmonic enhancement of fluorescence on silver nanoparticle films

The localized plasmon controlled fluorescence has been discussed by comparing the fluorescence enhancement of dyes on different shaped silver nanoparticle self-assembled films. A trilayer structure, composed of a silver nanoparticle monolayer, a proper thickness polyelectrolyte spacing layer and a dye-adsorbed layer, was constructed to study the plasmon enhanced fluorescence properties. The effective coupling of the plasmon band with the excitation or emission of dye resulted in different enhancement factors. Moreover, the plasmon enhanced fluorescence resonance energy transfer (FRET) of two dyes was observed. The FRET efficiency of the spherical silver nanoparticle self-assembled film had a 2.8-fold increase. The improvement of FRET efficiency via localized surface plasmons would increase the sensitivity of FRET-based bioassays.     

Size-dependent gas sensing properties of indium oxide nanoparticle layers

In2O3 nanoparticle layers having an average size of 8, 11, 15, 21, and 29 nm have been deposited using a two-step method consisting of chemical capping and dip coating techniques. The gas sensing properties in terms of sensor response and response time of the nanoparticle layers towards ethanol have been studied as a function of ethanol concentration and operating temperature. It has been observed that the sensor response increases and the response time decreases with decreasing size in the size range of 5-15 nm. The increase in sensor response at smaller nanoparticle size has been explained in terms of the increase in surface area and particle size becoming comparable to the electron Debye length.     

Tailoring silver nanoparticle construction using dendrimer templated silica networks

We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles.     

Antibacterial surfaces through dopamine functionalization and silver nanoparticle immobilization

Immobilization of silver nanoparticles on the dopamine functionalized polyimide (PI) films was carried out by photo-induced silver ion-reduction under atmosphere conditions. The dopamine has been successfully deposited on the PI surface in mild aqueous environments. The effects of pH, dopamine concentration and reaction time on the dopamine polymerization were investigated. The water contact angles of the poly(dopamine) functionalized PI films reduced remarkably in comparison with that of the pristine PI film. The chemical composition and structure of the UV-induced deposited-silver on the modified PI films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The topography of the modified PI films was investigated by scanning electron microscope (SEM). The deposited poly(dopamine) layer acted as binding sites for the silver ions. The silver-plated PI films showed good antibacterial activity due to that biofilm formation was inhibited on the polymeric surfaces in contact with bacteria.     

纳米银抗菌材料研发现状

介绍了纳米银抗菌材料的研究与开发现状 ,并叙述了纳米银的制备及其应用     

Characterization of the optical properties of silver nanoparticle films

To understand the collective properties of nanoparticles, it is necessary to control the particle size, spacing and ordering. Here we describe the chemical synthesis of well-controlled silver nanoparticles, the wet coat preparation and the optical properties of its film. The light incidence angle and polarization dependency of the resonant spectra show distinctive surface plasmon resonance extinction peaks for isolated particles and the coupled modes of neighbouring particles. Furthermore, we discuss the thermal treatment and dielectric surrounding effects on the optical properties of silver nanoparticle film.     

Hydrogen-induced electrical and optical switching in Pd capped Pr nanoparticle layers

In this study, modification in the properties of hydrogen-induced switchable mirror based on Pr nanoparticle layers is reported. The reversible changes in hydrogen-induced electrical and optical properties of Pd capped Pr nanoparticle layers have been studied as a function of hydrogenation time and compared with the conventional device based on Pd capped Pr thin films. Faster electrical and optical response, higher optical contrast and presence of single absorption edge corresponding to Pr trihydride state in hydrogen loaded state have been observed in the case of nanoparticle layers. The improvement in the electrical and optical properties have been explained in terms of blue shift in the absorption edge due to quantum confinement effect, larger number of interparticle boundaries, presence of defects, loose adhesion to the substrate and enhanced surface to volume atom ratio at nanodimension.     

Auger analysis of thick silver films and of silver layers grown on copper

A sensitive new measure of the line broadening of an Auger doublet, called the R factor, was applied to the growth of (1) thick silver films and (2) thin silver films on a thick copper substrate. It is shown that periodic fluctuations in R with thickness give evidence for monocrystalline layer growth while the absence of such fluctuations is characteristic of polycrystalline growth. By combining measurements of the Auger amplitude and the R factor as functions of the silver film thickness for silver films deposited onto copper, it was shown that a Stranski-Krastanov growth mode is characteristic of the epitaxial growth of Ag(111) on Cu(111) at 210°C. The initial layer in this case is two (111) atom spacings thick on which high flat islands form. Continued growth of these islands is shown to take place by two-atom-thick flat islands.     

Silver sulfide nanoparticle assembly obtained by reacting an assembled silver nanoparticle template with hydrogen sulfide gas

A fast, simple procedure is described for obtaining an assembly of silver sulfide nanoparticles (Ag(2)S NPs) on a glass substrate through reaction of a template of an assembled layer of silver nanoparticles (Ag NPs) with hydrogen sulfide (H(2)S) gas. The Ag NP template was prepared by assembling a monolayer of spherical Ag NPs (mean diameter of 7.4?nm) on a polyethylenimine-treated glass substrate. Exposure to pure H(2)S for 10?min converted the Ag NPs of the template to Ag(2)S NPs. The resulting Ag(2)S NP assembly, which retains the template nanostructure and particle distribution, was characterized by optical absorption spectroscopy, atomic force microscopy, transmission electron microscopy (TEM), scanning high resolution TEM, energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. The Ag(2)S NPs have a crystal structure of monoclinic acanthite, and while they retained the spherical shape of the original Ag NPs, their mean particle size increased to 8.4?nm due to changes to the crystal structure when the Ag NPs are converted into Ag(2)S NPs. The measured optical absorption edge of the Ag(2)S NP assembly indicated an indirect interband transition with a band gap energy of 1.71?eV. The Ag(2)S NP assembly absorbed light with wavelengths below 725?nm, and the absorbance increased monotonically toward the UV region.     

Electrical, optical and morphological properties of nanoparticle indium-tin-oxide layers

Porous layers were prepared from DEGUSSA's ITO (In₂O₃:Sn) nanoparticle dispersion by doctor blading followed by annealing in air. We investigated the influence of various annealing parameters on electrical, optical and morphological thin film properties.Conductance rises with increasing annealing temperature and time by more than three orders of magnitude up to 44 Ω^− 1cm^− 1. Besides this we found an abrupt decrease in free charge carrier concentration above a critical annealing temperature of 250 °C, which leads to a step in conductance curve. In spite of particle growing during annealing no decrease in porosity was observed and in opposite to compact material, nanoparticle layers do not exhibit an appreciable shrinkage below recrystallisation temperature. These both indicate a densification hindering particle pinning effect, which is believed to be currently the main obstruction to achieve higher electrical conductivities.