Growth Of Silver Particles Research Articles

Functionalizing calcium phosphate biomaterials with antibacterial silver particles.

Antimicrobial silver particles are created on calcium phosphate (CaP) biomaterials by sequentially incubating in citric acid and silver nitrate solutions. The subsequent silver release kinetics and released dosage are controlled by simply changing the solution conditions during growth of silver particles. Released silver efficiently suppresses the growth of gram-positive Staphylococcus aureus and gram-negative Escherichia coli without significant cytotoxicity to eukaryotic cells. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Processing and Characterization of Porous Silica-Ag-Nanoparticle Composites Produced by Pulsed Electric Current Sintering

This paper studies influence of the process temperature and time on the properties of the compacts made of Ag-SiO2 powder by the pulsed electric current sintering (PECS). Silica particles doped with Ag nanoparticles were prepared by modified Stöber method, and calcinated at 573 K in air resulting in average silica particle size of ~1.1 µm and agglomerate size up to 32 µm. There was about 7 wt.% of silver in the structure and the diameter of the silver particles on the silica carriers was 30 ±7 nm on average. The composite powder was sintered into porous compacts by PECS at 873, 973, 1073, or 1173 K for 10, 20, or 30 min under pressure of 50 MPa. Samples were characterized by SEM, XRD, UV-vis-spectrometer, and laser diffraction. During PECS compaction grain growth of silver particles was observed and the measured average size of Ag in 873 K and in 1173 K samples were 65 nm and 170 nm, respectively. The porosity of the materials did not show remarkable change, as the relative density ranged from 76 to 79 %. Thus, it is possible to produce porous silica based materials with controlled Ag-nanoparticle size by PECS. These materials may be optimized for, e.g., different kinds of antibacterial filters.

Method to Synthesize Silver Nano-particles for Inkjet Inks to Reduce Environmental Load

We have been studying the method to prepare metal nano-particles in aqueous solution. We presented the role of low molecular compounds as a dispersing agent in aqueous solutions to synthesize silver particles at NIP27, last year. At NIP28 of this year, we would like to present the effect of PVA and polyacrylic acid compounds on the growth of silver particles. The PVA used in this experiment are as follows: Saponification ratio is 78.5-99.4 mol% and polymerization degree is 500-2600, where the saponification ratio is defined as the ratio of the number of OH group to total number of OH and COOCH3 groups. The above both factors have affected the growth of silver particles and we have found in a series of our experiments that the PVA with the polymerization degree of 500 and the saponification ratio of 99.4 mol% has produced mono-dispersed silver particles of 10nm in average diameter. Furthermore, we have found that polyacrylic acid compounds as a dispersing agent have resulted in around 5nm in average diameter. Since this method to synthesized silver nano-particles does not use any organic solvents, we can avoid the problem regarding environmental pollution caused by organic fluids.

Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers

The cationic photopolymerization of triethylene glycol divinyl ether and concomitant formation of silver particles by the use of radical photoinitiators (BAPO and BEE) and an organosoluble silver salt (AgSbF6) are reported for the first time. The rate of photopolymerization is increased with higher concentrations of BEE, but the effect of AgSbF6 concentration is more complex. A localized surface plasmon resonance due to the formation of silver particles was observed very shortly after the commencement of irradiation, and the maximum absorption was found to increase with irradiation time as the particle concentration and size grew. The simultaneous formation of the polymer also stabilizes the particles and prevents their agglomeration. After a certain irradiation period, the maximum absorption reaches a plateau, prior to depletion of either silver ion or photoinitiator, suggesting that the formation of the polymer matrix may restrict silver particle growth. TEM studies reveal the presence of ∼10 nm diamete...

DDA-Based Simulation of UV–vis Extinction Spectra of Ag Nanorods Synthesized Through Seed-Mediated Growth Process

Present investigation demonstrates a very simple seed-mediated route for the synthesis of silver nanorods in aqueous solution. Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centres to grow nanoparticles to a desired size and shape. Hydroxypropyl methyl cellulose (HPMC) has been used as soft template for one-dimensional growth of silver particles. Morphological, structural and spectral changes that are associated with the seed-mediated growth of the nanoparticles in presence of HPMC are characterized using UV–vis and HR-TEM spectroscopic study. Simulation of UV–vis extinction spectra of our synthesized silver nanorods has been carried out using discrete dipole approximation methodology. The broad red-shifted longitudinal extinction band of green-coloured silver sol has been explained, due to the presence of silver nanorods of different aspect ratios.

Ag(I)/Ag electrode reaction in amide-type room-temperature ionic liquids

Ag(I)/Ag electrode reaction was investigated in some amide-type room-temperature ionic liquids composed of different cations. The morphology of silver deposits and the electrochemical behavior were not sensitive to the difference in the cations of ionic liquids. On the other hand, it was suggested that the adsorption of bis(trifluoromethylsulfonyl)amide (TFSA −) is more important for electrodeposition of silver in both ionic liquids and aqueous solutions. The diffusion coefficients of silver cation in the ionic liquids indicated the silver cation is surrounded by TFSA − to form a bulky species. The rate of crystal growth of silver particles in the ionic liquids by electrochemical Ostwald ripening was much slower than that in a nitrate aqueous solution, suggesting the charge transfer in the ionic liquids is slower than that in the aqueous solution.

Electrodeposition of silver particles from alkaline aqueous solutions and their electrocatalytic activity for the reduction of nitrate, bromate and chlorite ions

A pulsed electrochemical method was used for the preparation of silver deposit onto glassy carbon surfaces from an alkaline medium containing ammonia ligand. The morphology of the silver deposit, obtained under pulsed and cyclic conditions was examined and compared using the scanning electron microscopy (SEM) technique. From the experimental evidences, it can be inferred that pulsed method induces a favourable dendritic growth of silver particles, while deposited films obtained under cyclic voltammetry appear formed of globular particles with well regular and defined surface geometry. The electroanalytical performance of the deposited silver, towards the electroreduction of NO 3 −, BrO 3 − and ClO 2 − ions, using cyclic voltammetry and chronoamperometry technique, was evaluated. Interesting analytical results, in terms of sensitivity and temporal reproducibility, in alkaline medium and under constant applied potentials (i.e., −1.45 and −0.6 V vs. SCE), were obtained.

Modelling Ag-particle activation and growth in a TSI WCPC model 3785

Abstract. In this work, we modelled activation and growth of silver particles in the water-operated TSI model 3785 water condensation particle counter (WCPC). Our objective was to investigate theoretically how various effects influence the counting efficiency of this CPC. Coupled fluid and particle dynamic processes were modelled with the computational fluid dynamics (CFD) code FLUENT in combination with the Fine Particle Model (FPM) to obtain profiles of temperature, vapour concentration, nucleation rate, and particle size. We found that the counting efficiency of the TSI 3785 for small particles might be affected by the presence of larger particles. Moreover, homogeneous nucleation processes can significantly influence counting efficiency.

On-column silver substrate synthesis and surface-enhanced Raman detection in capillary electrophoresis

A new, simple, and efficient approach for on-column surface-enhanced Raman scattering (SERS) detection in capillary electrophoresis (CE) is reported. A approximately 50-microm SERS substrate spot was prepared by laser-induced growth of silver particles in the 100-microm inner diameter CE capillary window or in a flow cell consisting of a 250-microm inner diameter fused silica capillary connector. For this purpose, the Raman laser was focused by a 20x objective into the detection window filled with a 0.5 mM silver nitrate and 10 mM citrate buffer solution. During the CE runs, the silver substrate spot was formed in a few seconds after the analyte injection, hence the analytes adsorbed sequentially to the silver surface when the detection window was reached, followed by desorption from the silver surface and continuing the electrophoretic migration to the capillary end. Thus, beyond migration time, valuable molecular specific information was delivered by the SERS spectra. Accurate separations and high-intensity SERS spectra are shown by CE-SERS time-dependent 3D electropherograms for the analytes rhodamine 6G, 4-(2-pyridylazo)resorcinol (PAR), PAR complex with Cu(II) and methylene blue at 0.25-25 ppm concentrations, by using 1.4-3.6 mW HeNe laser power and an acquisition time of 5 s for each spectrum. Before and after each analyte passes the detection window, clean background spectra were recorded and no memory effects perturbed the SERS detection. The silver substrate is characterized by a fast preparation rate, good reproducibility, a preparation success rate of over 95% and no mentionable influence on the electrophoretic migration time, the CE-SERS and CE-UV electropherograms being in good agreement. The successful coupling of CE and on-column SERS detection opens new perspectives for monitoring CE separations.

In situ growth of silver nanoparticles in mesoporous silica by spray pyrolysis

Silver-dispersed mesoporous silica was in situ synthesized in aerosol phase. The solidification of silica was catalyzed in the presence of the silver, which increased the order and d values of the mesophase at given reactor temperature. Silver nanoparticles grew confined in the pores when the atomic % of silver to Si was below 10 and the pore wall turned to be impermeable above 400 °C. Silver permeated through the pore wall below 400 °C to grow freely in the carrier gas. The mesophase deteriorated using spray pyrolysis above 800 °C due to the further densification of silica, or above 10 at.% of silver due to the excessive growth within the phase. The highest dispersion of silver ~4 nm in diameter with the highest order of the mesoporosity was obtained at 600 °C with 5 at.% silver. Calcination following the spray pyrolysis further densified the silica phase to freeze the growth of silver particles as well as lower the d value of the mesophase.

Photoinduced Shape Evolution: From Triangular to Hexagonal Silver Nanoplates

Successfully using the solution phase, we have prepared, in large quantities, uniform hexagonal silver nanoplates developed from silver triangular nanoprims by employing a photoinduced technique. The growth process was characterized by ultraviolet−visible (UV−vis) spectroscopy, transmission electron microscope (TEM), and high-resolution transmission electron microscope (HRTEM). The UV−vis spectra showed that three bands of hexagonal silver nanoplates appear at 341 (weak), 368 (medium), and 498 (strong) nm. TEM images showed that hexagonal silver nanoplates had an average edge size of 25.9 nm and thickness of 15.7 ± 1.0 nm. The mechanism of the conversion from triangular to hexagonal nanoplates has also been studied. Triangular silver nanoplates were at first fabricated through seed-mediated growth of silver particles in the presence of trisodium citrate. Subsequently, the truncation of triangular nanoplates led to the formation of hexagonal nanoplates.

Self-assembly of silver nanoparticles in a polymer solvent: formation of a nanochain through nanoscale soldering

By exploiting the orientation of the polymer methoxy polyethylene glycol (MPEG), directional growth of silver particles has been obtained in the presence of ultraviolet irradiation for the first time. MPEG generates free radicals, serves as the reducing agent in presence of ultraviolet irradiation towards the silver ions, and also acts as the template for the silver particles involved in the formation of a silver chain.

Modeling silver catalyst sintering and epoxidation selectivity evolution in ethylene oxidation

Catalyst sintering is a slow complex process which may last for years but is contributed by physical processes of atomic femtosecond scale. In this article, sintering caused silver particle growth is considered to be the result of random migration and coalescence, on the basis of which a random walk model is proposed. Simulation results show that the particle size evolution can be well fitted by generalized power law expression, indicating that the random walk model is valid for sintering processes with different sintering rates and time scales. With the assumption of identical grain sizes, changes in the specific surface intergrain boundary length during particle sintering are predicted by the random walk model and the epoxidation rate is related to the specific surface intergrain boundary length in terms of a selectivity factor. The results elucidate quite well the phenomenon of nonmonotonic change of the selectivity during silver catalyst sintering.

Silver Nanodisk: Synthesis, Characterization and Self-Assembly

ABSTRACTA new form of silver nanostructured materials, a silver nanodisk, is generated by a solution-phase approach. In this method, two main steps are applied: the first is the generation of the truncated triangular silver nanoplates, which are obtained by seed-mediated growth of silver particles using cetyltrimethylammonium bromide (CTAB) as the soft templates. The second is the mild aging of the above triangular silver nanoplate solution at 40 °C to get the desired silver nanodisks. Transmission electron microscopy and atomic force microscopy studies show that the nanodisk has a thickness of the order of 20 – 30 nm, and a diameter around 60 nm. X-ray and electron diffraction analysis reveal that the nanodisk is single crystal and with its basal plane as (111) lattice plane. These nanodisks display a strong surface plasmon absorption band at 475 nm; this band can be continuously tuned within 420 nm to 560 nm through adjusting the aging time. The formation of self-assembled monolayer of CTAB on the basal plane is suggested to account for both the anisotropic growth from triangular nanoplates to nanodisks, and the formation of large-scale necklace-like structures.

Oxidation of photochromic spirooxazines by coinage metal cations. Part I. Reaction with AgNO3 : formation and characterisation of silver particles

Thermal oxidation of the zwitterionic form of two photochromic spirooxazines: 1,3-dihydro-1,3,3-trimethylspiro(2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine) (1) and 1,3-dihydro-1,3,3-trimethylspiro(2H-indole-2,3′-[3H]phenanthr[9,10-b]-[1,4]oxazine) (2) has been studied in the presence of silver ions in anaerobic conditions. The products of the reaction have been identified and a mechanism for their formation is proposed. In alcohols (MeOH, EtOH), the major degradation product is the indolinooxazole salt together with either methoxy- or ethoxy-substituted spirooxazines at the C2′ carbon atom of the C2′N1′ bond. The four new spirooxazine derivatives display no photochromic properties although X-ray diffraction studies show that the bond lengths around the spiro carbon atom are similar to those observed for compounds revealing colouration. Photophysical properties of the indolinooxazole and of its hydroxylated derivative are also presented. High quantum yield and large Stokes shifts are observed. As a consequence of the reduction of silver ions to neutral atoms, silver colloids have been prepared after either thermal- or photo-oxidation of spirooxazine. They are stabilised by poly(N-vinylpyrrolidone). The formation and growth of silver colloids have been studied by electron microscopy, photon correlation spectroscopy and UV-vis absorption spectroscopy. The growth of silver particles of different sizes and morphologies is presented and the role of a photochromic electron donor on the growth process is discussed. The average particle sizes ranged from a few to approximately one hundred nanometers. The classical plasmon absorption band at 420 nm and a broad red-shifted peak at 790 nm due to the large non-spherical particles are thus observed. Both particle size and plasmon absorption are dependent upon UV irradiation. Size enlargement upon irradiation of silver colloids brings about colour changes from yellow through green to light blue.

Nanostructured Silver Particles Embedded in a Silica Matrix

AbstractA series of different nano-sized silver particles has been prepared using r.f. magnetic plasma co-sputtering apparatus. A combination of high-resolution lattice images and optical diffractograms has been used to characterize the atomic structures during nucleation and growth of silver particles embedded in a silica matrix. For particles with diameter of 2 ∼ 5 nm, most have single crystal structures, but some have singly twinned morphologies and a few have multiply twinned morphologies. In those particles, there are many defects such as dislocations, stacking faults, twin boundaries and lattice fringe bends. For particles with diameter of 5 ∼ 9 nm, we can detect some single crystals, singly twinned particles and multiply twinned particles including decahedral and icosahedral particles. Anomalous meta-stable structured particles with 90° cross {111} lattice fringes have been also found. For particles with diameters of larger than ∼ 9 nm, most have multiple lamellar twins and sometimes there are macroscopically irregular shaped particles.

ChemInform Abstract: Growth of Silver Particles in Aqueous Solution: Long‐Lived “Magic” Clusters and Ionic Strength Effects.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Growth of silver particles in aqueous solution: long-lived "magic" clusters and ionic strength effects

Pulse radiolytic reduction of silver ions leads to an oligomeric cluster absorbing at 295 nm and most intensely and sharply at 325 nm. The cluster has a half-life of >5 min in scrupulously clean reaction vessels. During its decay, larger metallic particles absorbing around 380 nm are produced. The cluster is long-lived only in the presence of excess Ag[sup +] ions. A second cluster absorbing at 345 nm is also formed during the oxidation. Tetranitromethane reacts with the cluster to form the nitroform anion, from which the absorption coefficient per Ag atom is calculated to be 2 [times] 10[sup 4] M[sup [minus]1] cm[sup [minus]1]. The formation of the cluster is accelerated by NaClO[sub 4]; the Bjerrum-Broenstedt evaluation of this effect shows that a precursor of the cluster carries three elementary charges. The formation of larger metallic particles is even more strongly accelerated by NaClO[sub 4]. In the presence of 10[sup [minus]4]M Na[sub 2]SO[sub 4], the formation and decay of the cluster occur practically at the diffusion-controlled rate. From the rate of the buildup under these conditions, it is estimated that the cluster contains eight reduced silver atoms. The effects of ionic strength on the growth of the clusters and metallicmore » particles are compared to the salt effects in slow and fast coagulation of colloids. 14 refs., 8 figs.« less

Effect of Additives on Ostwald Ripening of Silver in Glass

The effect of additives on the growth of silver particles in a lead borosilicate glass was studied. Growth of silver particles was expressed by the Ostwald ripening theory and controlled by diffusion. Addition of palladium retarded the growth of silver particles. This is attributed to the reduced activity of silver caused by the formation of silver–palladium solid solutions. Addition of ruthenium dioxide promoted the growth, whereas addition of tin dioxide had almost no effect on the growth rate. A “solubility parameter” was introduced to evaluate the temperature dependence of solubility of silver in glass, and the effect of additives has been discussed. Association of diffusion species has been proposed as a possible factor responsible for the temperature dependence of the solubility parameter.

Effect of Temperature on Ostwald Ripening of Silver in Glass

The effect of temperature and volume fraction on the growth of silver particles in a lead borosilicate glass has been studied. The particle growth obeyed the Ostwald ripening theory and was controlled by diffusion. An anomaly of growth rate coefficient was observed around 700°C and explained in terms of the dissolution behavior of silver. Also, the solubility of silver in glass was evaluated from the normalized rate coefficient K using volume fraction of silver particles and viscosity of the glass.