Photoreduction Of Ag Research Articles

Photoreduction of Ag+ ions and coalescence of silver nanoparticles in aqueous polyacrylate solutions

It is shown that changes in the spectral composition of irradiating light makes it possible to realize the competing photoreduction of Ag+ ions by polyacrylate anions in the bulk of an aqueous solution and on the surface of silver nanoparticles, which is accompanied by their coalescence.

Photoinduced Ag n0 cluster deposition : Photoreduction of Ag + ions on a TiO 2-coated quartz crystal microbalance monitored in real time

The extent of photoreduction of a metal ion, such as Ag +, occurring on the TiO 2 particle surface was monitored in real time in the presence of hole scavengers methanol and ethanol by the quartz crystal microbalance (QCM) technique. Silver cluster deposition on metal-oxide particles that accompanies electron transfer from TiO 2 to Ag +(ads) depends on the surface charge of the particles, which also influences the close approach of Ag + ions to the particle surface. Formaldehyde and acetaldehyde produced, respectively, as intermediates during silver deposition in the presence of the alcohols contributed negligibly to the mass of silver deposited on the TiO 2 surface. The QCM technique provides a means to monitor photoadsorption.

Combinatorial discovery of anomalous substrate effect on the photochemical properties of transition metal-doped epitaxial SrTiO 3 heterostructures

Epitaxial Sr(V x Cr y Ti 1− x− y )O 3 ( 0 ≤ x + y ≤ 0.05 ) ternary composition spreads were grown on two different single crystal substrates, LaAlO 3 and Nb-doped SrTiO 3, by use of combinatorial laser molecular beam epitaxy with a specially patterned slide masking plate. The photocatalytic activity on the composition spreads was evaluated by the photo-reduction of Ag + in an AgNO 3 aqueous solution to deposit Ag metal on the spreads. The V-doping effect was found to depend greatly on the substrate: the photodeposition of Ag was much enhanced in the composition region of SrV 0.05Ti 0.95O 3 only on the Nb-doped SrTiO 3, but not on the LaAlO 3 and non-doped SrTiO 3.

Photoreduction of Ag+ in aluminoborate glasses induced by irradiation of a femtosecond laser

We report on photoreduction of Ag+ in aluminoborate glasses induced by irradiation of a femtosecond laser. Novel fluorescence was observed in the femtosecond laser irradiated glass when excited by a 365 nm ultraviolet lamp. Optical absorption, emission, and electron spin resonance spectra of the glass samples demonstrated that after the laser irradiation, portions of silver ions near the focused part of the laser beam inside the glass were reduced to silver atoms, which resulted in the formation of the characteristic fluorescence. The observed phenomenon may have promising applications in the fabrication of functional optical devices.

High-throughput Studies on Photochemical Properties of Transition Metal-Doped SrTiO3 Epitaxial Thin Films

AbstractCombinatorial pulsed laser deposition approach is suitable to study complex effects such as composition, thickness and surface structure on thin film-based photocatalysis in high-throughput manner. We fabricated composition spreads and thickness gradient films of transition metal-doped SrTiO3(001) on various oxide single crystal substrates and evaluated their photocatalytic activity by the use of photoreduction of Ag+ in AgNO3 solution. We found anomalous film thickness and substrate effects on the Ag-photodeposition in the V-doped SrTiO3 epitaxial thin films grown on the Nb:SrTiO3(001) substrate.

Photoreduction of silver ions in a colloidal titanium dioxide suspension

The photoreduction of Ag + ions at the surface of colloidal TiO 2 nanoparticles has been investigated. Irradiation of an aqueous solution containing TiO 2 and Ag + ions with near-UV light brings about the growth of a sharp absorption band of colloidal silver in absorption spectrum. The photoreduction of Ag + ions by TiO 2 is optically sensitized by a simple cyanine dye, 3,3′-disulfopropyl-5,5′-dichloro-thiacyanine sodium salt (TC). TC molecules are adsorbed at the surface of TiO 2 nanoparticles in the form of the J-aggregate (JA). Visible-light irradiation of the solution containing TiO 2, Ag + ions, and TC causes the growth of a broad absorption band of the colloidal silver and the decrease of whole absorption bands of TC. Experimental results have been interpreted in terms of electronic energy levels of the colloidal silver and the TC aggregate, as well as energy bands of TiO 2. In the sensitized photoreduction, TiO 2 could play the role of a medium to facilitate efficient electron transfer from the excited TC aggregate to Ag + ions adsorbed at the surface.

Photo-catalytic preparation of silver-coated TiO2 particles for antibacterial applications

Colloidal silver has been known to have unique antimicrobial activity that may be useful in the construction of antibacterial materials (self-cleaning materials) to aid in the fight against bacteria-related infections. In this study, silver-coated TiO2 (Ag/TiO2) particles prepared through the photo-reduction of Ag+ were investigated as an antibacterial agent against Escherichia coli and Staphylococcus aureus. The deposition of Ag onto the surface was confirmed with SEM and EDS analysis of the post-reaction particles. It was also determined that the initial concentration of Ag+ in solution played a significant role in the effective size of the post-irradiation particles. The antibacterial effectiveness of the Ag/TiO2 was evaluated through the determination of the minimum inhibitory concentration (MIC) of AgTiO2 for each species of bacteria. The MIC values for the Ag/TiO2, on both E. coli and S. aureus, were much lower than the MIC values for Ag metal, and quite comparable to the MIC values for AgNO3. A disc diffusion/antibiotic sensitivity test was also performed using the Ag/TiO2 particles and the results compared with the results obtained for Ag metal, AgNO3 and common antibacterial agents; tetracycline, chloramphenicol, erythromycin, and neomycin. The zone of inhibition diameters for the Ag/TiO2 particles were found to be comparable with those of the other antimicrobial agents.

Tapping Mode Atomic Force Microscopy Studies of the Photoreduction of Ag+ on Individual Submicrometer TiO2 Particles

In this paper we describe an experimental procedure that can be used to study the photoreduction of metal ions on the surfaces of individual TiO2 particles. The submicrometer-sized particles are isolated on porous membranes, characterized by atomic force microscopy (AFM), removed from the microscope, exposed to AgNO3 solution and light, and reimaged. Photoreduction of Ag+ produces 5−50 nm particles of Ag0 distributed over the surfaces of the TiO2 particle. This procedure allows the spatial distribution of the chemical reactivity of particle surfaces to be mapped at the nanometer scale resolution of the atomic force microscope. Using different excitation wavelengths (366, 400 and ∼600 nm), we demonstrate by AFM that the photoreduction of Ag on single anatase or rutile particles is consistent with the differences in the band gaps of the bulk samples. We also show that the Ag0 particles are not uniformly distributed over the TiO2 crystallite surfaces implying that a closer study of the unreacted particle sur...

Orientation Dependence of Photochemical Reactions on TiO2 Surfaces

The photochemistry of oriented rutile surfaces has been examined using the photoreduction of Ag+ to Ag metal from an aqueous solution onto the TiO2 surfaces. The photochemical reaction rates and quantum yields of rutile films were found to be a function of the orientation of the rutile surface. The (100) and (110) rutile orientations have lower photoreduction rates than the (101), (111), and (001). This dependence of the photochemical reaction rates on film surface orientation is observed over a range of light intensities, illumination wavelengths, and film thicknesses. Atomic force microscopy has been used to characterize the morphologies of the film surfaces and the photoreduced Ag at these surfaces. Several properties of rutile, such as the surface morphology, surface chemistry, space charge phenomena, and charge transport, are discussed in relation to their possible contributions to the orientation dependence of the photochemistry on the rutile films.

ChemInform Abstract: THE PHOTOREDUCTION OF THE SILVER ION IN A ZINC OXIDE SUSPENSION

AbstractFür die Photoreduktion von AgClO4 (5·10‐5 ‐ 1·10‐3 M) in einer wäßrigen ZnO‐Suspension mittels Licht der Wellenlänge 365 nm werden Quantenausbb.

The Photoreduction of the Silver Ion in a Zinc Oxide Suspension

Abstract Quantum yields of from 0.235 to 0.385 have been determined for the reduction of Ag+ by the irradiation of 365 nm light on a ZnO surface in aqueous solutions containing 5×10−5 to 1×10−3 M AgClO4. It is proposed that these results can be interpreted by a reaction scheme based on the assumption that some conduction-band electron produced in the ZnO by the irradiation transfers to the Ag+ adsorbed on the ZnO surface. The surface-energy barrier under the present experimental conditions was discussed with the aid of the electrochemical measurement of the ZnO sinter. The photoreduction of Ag+ is optically sensitized by the addition of xanthene dyes, such as Uranine and Rhodamine B. In this case, it is observed that the photoreduction of Ag+ is accompanied by the photolysis of dye molecules. The apparent quantum yields (the number of reacted molecules/the number of photons absorbed in the suspension) of the dye-sensitized photoreduction of Ag+ and the photolysis of dye molecules are 0.015 and 0.007 for Uranine, and 0.003 and 0.0003 for Rhodamine B, respectively.