Photodeposition Of Silver Research Articles

Functionalized BP@(Zn+Ag)/EPLA Nanofibrous Scaffolds Fabricated by Cryogenic 3D Printing for Bone Tissue Engineering.

This study fabricates a functionalized scaffold by cryogenic three-dimensional (3D) printing using an aminated poly-L-lactic acid (EPLA) solution containing nanosilver/zinc-coated black phosphorus (BP@(Zn+Ag)) nanocomposites. The nanocomposites are prepared by a green method of in situ photodeposition of silver and zinc nanoparticles (AgNPs and ZnNPs) on BP nanosheets (BPNs) under visible light irradiation without any chemical reductant. Scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) confirm the uniform distribution of BP@(Zn+Ag) nanoparticles in the EPLA nanofibrous matrix. The in vitro tests show that the fabricated BP@(Zn+Ag)/EPLA nanofibrous scaffold exhibits excellent antibacterial activity (over 96%) against E. coli and S. aureus, as well as enhanced cell viability and osteogenic activity to facilitate the growth and differentiation of osteoblasts. The in vivo rat calvarial defect model also demonstrates that the BP@(Zn+Ag)/EPLA nanofibrous scaffold promotes new bone tissue formation around the implant site. Therefore, the prepared multifunctional 3D printed BP@(Zn+Ag)/EPLA nanofibrous scaffold has great potential for bone tissue engineering (BTE) applications.

Ferroelectric Polarization in BaTiO3 Nanocrystals Controls Photoelectrochemical Water Oxidation and Photocatalytic Hydrogen Evolution.

Ferroelectric (FE) semiconductors such as BaTiO3 support a remnant polarization after the application of an electric field that can promote the separation of photogenerated charge carriers. Here, we demonstrate FE-enhanced photocatalytic hydrogen evolution and photoelectrochemical water oxidation with barium titanate nanocrystals for the first time. Nanocrystals of the ferroelectric tetragonal structure type were obtained by a hydrothermal synthesis from TiO2 and barium hydroxide in 63% yield. BaTiO3 nanocrystal films on tantalum substrates exhibit water oxidation photocurrents of 0.141 mA cm-2 at 1.23 V RHE under UV light (60 mW cm-2) illumination. Electric polarization at 52.8 kV cm-1 normal to the film plane increases the photocurrent by a factor of 2 or decreases it by a factor of 3.5, depending on the field polarity. It also shifts the onset potential by -0.15 or +0.09 V and it modifies the surface photovoltage signal. Lastly, exposure to an electric field increases the H2 evolution rate of Pt/BaTiO3 by a factor of ∼1.5, and it raises the selectivity of photodeposition of silver onto the (001) facets of the nanocrystal. All FE enhancements can be removed by heating samples above the Curie temperature of BaTiO3. These findings can be explained by FE dipole-induced changes to the potential drop across the space charge layer of the material. The ability to use the ferroelectric effect to enhance hydrogen evolution and water oxidation is of potential interest for the development of improved solar energy for fuel conversion systems.

Examining Silver Deposition Pathways onto Gold Nanorods with Liquid-Phase Transmission Electron Microscopy

Liquid-phase transmission electron microscopy (LP-TEM) enables one to directly visualize the formation of plasmonic nanoparticles and their postsynthetic modification, but the relative contributions of plasmonic hot electrons and radiolysis to metal precursor reduction remain unclear. Here we show silver deposition onto plasmonic gold nanorods (AuNRs) during LP-TEM is dominated by water radiolysis-induced chemical reduction. Silver was observed with LP-TEM to form bipyramidal shells at higher surfactant coverage and tip-preferential lobes at lower surfactant coverage. Ex situ silver photodeposition formed nanometer-thick shells on AuNRs with preferential deposition in inter-rod gaps, while chemical reduction deposited silver at AuNR tips at low surfactant coverage and formed pyramidal shells at higher surfactant coverage, consistent with LP-TEM. Silver deposition locations during LP-TEM were inconsistent with simulated near-field enhancement and hot electron generation hot spots. Collectively, the results indicate chemical reduction dominated during LP-TEM, indicating observation of plasmonic hot electron-induced photoreduction will necessitate suppression of radiolysis.

Enhanced sensitivity from Ag micro-flakes encapsulated Ag-doped ZnO nanorods-based UV photodetector

An innovative method of improving zinc oxide (ZnO) nanorods-based ultraviolet (UV) photodetectors was fabricated by photodeposition of silver (Ag) micro-flakes on top of Ag-encapsulated Ag-doped ZnO nanorods. Four concentrations are selected for the doping process (0, 1.7, 3.4, and 5.1 mol%). The Ag-doped ZnO nanorods are synthesized via the hydrothermal method, followed by photodeposition using AgNO3 solution, both of which are low-cost and simple. Ag doping resulted in thinner and shorter ZnO nanorods, improved crystallinity, and reduction of deep-level emissions as corroborated by field emission scanning electron microscopy, X-ray diffraction, and photoluminescence analyses. UV photodetectors fabricated from the samples showed that Ag-doped ZnO nanorods in addition to Ag micro-flakes have improved sensitivity and gain than non-doped ZnO nanorods. Excessive doping results in a higher dark current and reduced sensitivity. A proposed mechanism is given showing the source of photocurrents from Ag micro-flakes and Ag-doped ZnO nanorods.

Green Synthesis of Silver-Doped Titanium Dioxide Nanostructures for Acetaminophen Degradation Under Solar Radiation

Objective: In this paper, the photocatalytic degradation of acetaminophen was evaluated using silver-doped titanium dioxide nanoparticles in a cylindrical-parabolic composed photoreactor. Materials and methods: Titanium dioxide was synthesized via green synthesis using Cymbopogon citratus leaf extract and doped by silver photodeposition. Results and discussion: Morphological information shows that large agglomerates of approximately 49 nm can be attributed to the strong interaction between nanoparticles and their polycrystalline nature. The photodeposition of metallic silver reduces the surface effects, allowing a decrease in the electrostatic interaction and diameter size of the titanium dioxide, as well as the optical properties due to surface poising during the reduction of silver ions to metallic silver. The photocatalytic activity was performed to degrade acetaminophen as the drug model under visible-light radiation. The results are promising, with superior photodegradation of acetaminophen of approximately 37% and 11% for unmodified titanium dioxide and silver-doped titanium dioxide (0.75 at%) nanostructures compared to the commercial photocatalyst, respectively. Conclusions: Accordingly, the potential photocatalytic application of silver-doped titanium dioxide nanostructures is highlighted and represents a promising alternative for the photodegradation of organic compounds from wastewater eluents.

Silvered TiO2 for Facet-Dependent Photocatalytic Denitrification

In this paper, the influence of exposed facets of silvered TiO2 photocatalysts for photodenitrification was fundamentally investigated. We found that photodeposition of silver on 001-faceted TiO2 w...

High performance SERS platforms via parametric optimization of the laser-assisted photodeposition of silver and gold nanoparticles

Parametric optimization of the laser-assisted photocatalytic growth of Ag and Au nanoparticles for high SERS enhancement factor performance informed by design of experiment is demonstrated. The photodeposition process was divided into two phases –seeding and growth– in order to achieve the highest possible nanoparticle surface coverage for the size range from 10 to 100 nm. A substantial difference in the parameter effects between the Ag and Au seeding and growth was found. The SERS performance of the photodeposited Ag and Au nanostructures was evaluated at 532, 633 and 785 nm with thiophenol as a probe molecule. A high-enhancement broadband SERS operation was attained with Ag nanostructure grown at high laser fluences. The SERS enhancement factors of 105 were achieved with both Ag and Au nanostructures.

Double Z-scheme FeVO4/Bi4O5Br2/BiOBr ternary heterojunction photocatalyst for simultaneous photocatalytic removal of hexavalent chromium and rhodamine B

HypothesisFabrication of the heterojunction photocatalyst with appropriate band potentials as a promising method of inhibiting electron-hole pair recombination leading to enhanced photocatalytic properties. ExperimentsHerein, BiOBr, Bi4O5Br2, and binary BiOBr/Bi4O5Br2 composite were selectively synthesized by employing a one-step microwave irradiation method. Then, double Z-scheme FeVO4/Bi4O5Br2/BiOBr ternary composites with different weight percentages (%wt) of FeVO4 were fabricated and their photocatalytic applications were studied. The photodegradation of organic compounds (rhodamine B (RhB), methylene blue (MB) and salicylic acid (SA)), along with the photoreduction of hexavalent chromium (Cr(VI)) were investigated. FindingsComparing with the single and binary photocatalysts, and a commercial TiO2, the 1 %wt-FeVO4/Bi4O5Br2/BiOBr photocatalyst demonstrated superior visible-light-driven photocatalytic performance. In a Cr(VI)/RhB combined system, Cr(VI) photoreduction was further improved and coexisting RhB molecules were simultaneously degraded. Removal of Cr(VI) and RhB were maximized by adjusting both pH values and catalyst dosages. Based on UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, electrochemical investigations, active-species trapping, nitrotetrazolium blue transformation, and silver photo-deposition experiments, a double Z-scheme charge transfer mechanism with an RhB-sensitized effect was proposed. This special mechanism has led to significant enhancement in charge segregation and migration, along with higher redox properties of the ternary composite, which were responsible for the excellent photocatalytic activity.

Interactions of Plasmonic Silver Nanoparticles with High Energy Sites on Multi‐Faceted Rutile TiO2 Photoanodes

AbstractThe plasmonic interactions between silver nanoparticles and various rutile TiO2 facets are studied by correlating Advanced Electron Microscopy and Electrochemical Impedance Spectroscopy (EIS) to help design a route towards an optimised polycrystalline film fabrication. By using an Electron Backscatter Diffraction (EBSD) detector, it was determined that using HF as directing agent during the hydrothermal growth of TiO2 promotes the formation of high‐angle grain boundaries. Silver photodeposition occurs preferentially at these boundaries, consistent with the presence of high energy sites on the (100)‐oriented rutile TiO2 nanorods. Further EIS study showed an increase in the photoelectrochemical activity in the visible range of the solar spectrum for the samples consisting of silver nanoparticles deposited on these grain boundaries.

Photocatalytic evaluation of RGO/TiO2NWs/Pd-Ag nanocomposite as an improved catalyst for efficient dye degradation

In this work RGO/TiO2NWs/Pd-Ag nanocomposite was prepared by using a combination of hydrothermal and photo-deposition methods. The properties of all prepared products were evaluated by using SEM, XRD, DRS, FT-IR, EDS, BET, TEM, TGA and ICP-OES analysis. Nanodimension structure of all samples was confirmed by TEM and SEM results. The calculated band gap values which were obtained by using DRS technique, suggested that Gr/TiO2NWs/Pd-Ag nanocomposites have a semiconductor behavior with a direct band-gap value of 2.95 eV. The amount of loaded graphene in the nanocomposite was evaluated by using TGA analysis. The degradation of rhodamine B and methylene blue by TiO2-NWs and RGO/TiO2NWs/Pd-Ag nanocomposites were compared under UV light irradiation in similar conditions. The observations confirmed that the RGO/TiO2NWs/Pd-Ag nanocomposite have high photocatalytic performance toward both of pollutants owning to the much higher available surface area of TiO2 nanowires, the unique synergic effect of Pd and Ag species and high electric transport property of the graphene structure. The product synthesis procedure has valuable advantages like high surface area photocatalyst, facile photodeposition of silver and palladium on the TiO2 surface, and simple conversion of graphene oxide (GO) to reduced graphene oxide (RGO) during the hydrothermal process without using strong reducing agents, which can be a promising route for preparing various types of high active carbon based nanocomposite photocatalyst.

Lanthanum doped titania decorated with silver plasmonic nanoparticles with enhanced photocatalytic activity under UV-visible light

Lanthanum doped titanium dioxide decorated with silver plasmonic nanoparticles (Ag-La/TiO2 NPs) materials were prepared using a simple ultrasound-assisted wet impregnation method followed by silver photodeposition. The obtained photocatalysts with different Ag contents were characterized by XRD, FE-SEM, EDX, TEM, BET, XPS, DRS and PL techniques. Moreover, the size distribution of the nanoparticles aggregates was assessed. The characterization analysis revealed that La doping slightly changed the crystalline phase of TiO2, increased the amount of surface hydroxyl groups and interacted with TiO2 nanoparticles via Ti–O–La bond, while Ag photodeposition enhanced the absorption of visible light due to the effects of localized surface plamon resonance and significantly decreased electronic recombination rate by the Schottky junction. Furthermore, the combination of Ag-La induced the formation of oxygen vacancies, which increased the amount of adsorbed surface hydroxyl groups in Ag-La/TiO2. In addition, Ag-La possibly decreased the semiconductor surface energy, which acted positively in the reduction of NPs aggregation. These features along with better textural properties (greater surface areas) played a fundamental role in the enhancement of the photocatalytic activity of Ag-La/TiO2 composites for the decolorization of methylene blue under UV-visible irradiation compared to the mono-metallic (La/TiO2 and Ag/TiO2) modified photocatalysts. Finally, a mechanism for the transfer of charge carriers in Ag-La/TiO2 photocatalyst under UV-visible irradiation was proposed.

Photodeposition of silver on p-Cu2O/n-TiO2 nanocomposite applied to visible light degradation of 2,4-dichlorophenol in synthetic wastewater

Photodeposition of silver on p-Cu2O/n-TiO2 nanocomposite applied to visible light degradation of 2,4-dichlorophenol in synthetic wastewater

The Transfer Direction of Photogenerated Electrons in BaTiO3/TiO2 and CaTiO3/TiO2

BaTiO3/TiO2 and CaTiO3/TiO2 bilayer-type photocatalyst films have been prepared and characterised by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, UV-vis, and scanning electron microscopy techniques. The photodeposition of silver was done to confirm the reduction positions of the titanate/TiO2 films. Silver deposited preferentially on the side of TiO2 for BaTiO3/TiO2 whereas on the side of CaTiO3 for CaTiO3/TiO2. These results imply that the direction of photogenerated electron transfer is coincident with the semiconductor physical principles. Upon exposure to light, electron–hole pairs are generated and subsequently separated by an internal electrostatic field in the titanate–TiO2 heterojunction.

Enhanced photocatalytic removal of phenol from aqueous solutions using ZnO modified with Ag

Different photocatalysts based on commercial ZnO modified by silver photodeposition were prepared in this work. The samples were characterized by X-ray fluorescence spectrometry (XRF), specific surface area (SSA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance (UV–vis DRS). XRD and XPS showed that Ag/ZnO samples are composed of metallic Ag (Ag0) and ZnO structure was identified. Furthermore, TEM analysis evidenced that the number of silver particles increased with the Ag content. At last, UV–vis DRS results revealed a reflectance band for Ag/ZnO samples, ascribed to the surface plasmon resonance (SPR) absorption of metal silver particles. Commercial ZnO and Ag/ZnO samples were evaluated in the phenol removal under UV light irradiation. It was observed an enhancement of photocatalytic phenol removal from aqueous solutions by silver addition in comparison to commercial ZnO. In particular, the phenol removal increased with the silver content from 0.14 to 0.88wt%, after this content (i.e 1.28wt%) the phenol degradation significantly decreased indicating that the optimal Ag content was equal to 0.88wt%. The influence of the best photocatalyst dosage and the change of the initial phenol concentration in solution were also investigated in this work and the best photocatalytic performance was obtained by using 50mgL−1 of phenol initial concentration and 0.15gL−1 of photocatalyst dosage. Finally, the optimized Ag/ZnO photocatalyst was employed for the treatment of a real drinking wastewater containing phenol in which the almost total phenol removal was achieved after 180min of UV irradiation time.

Silver- and copper-modified decahedral anatase titania particles as visible light-responsive plasmonic photocatalyst

Decahedral anatase particles (DAPs) with eight equivalent (101) facets and two (001) facets were prepared by the gas-phase process. Monometallic and bimetallic photocatalysts were prepared by photodeposition of silver and copper on DAP. It was found that the method of metal deposition (sequential/simultaneous) is crucial for resultant properties and thus for photocatalytic performance. The fastest hydrogen evolution during metal deposition was observed for copper deposited on premodified DAP with silver (DAP/Ag/Cu), probably due to partial coverage of silver with fine clusters of Cu and thus facilitation of proton adsorption and reduction on well-dispersed Cu nanoclusters. Although DAP/Ag/Cu exhibited the fastest rate of hydrogen evolution, single-modified DAP with silver exhibited the best performance for oxidative decomposition of organic compounds under vis irradiation.

Silver decorated polymer supported semiconductor thin films by UV aided metalized laser printing

A facile ultraviolet assisted metalized laser printing technique is demonstrated through the ability to control selective photodeposition of silver on flexible substrates after atomic layer deposition pretreatment with zinc oxide and titania. The photodeposition of noble metals such as silver onto high surface area, polymer supported semiconductor metal oxides exhibits a new route for nanoparticle surface modification of photoactive enhanced substrates. Photodeposited silver is subsequently characterized using low voltage secondary electron microscopy, x-ray diffraction, and time of flight secondary ion mass spectroscopy. At the nanoscale, the formation of specific morphologies, flake and particle, is highlighted after silver is photodeposited on zinc oxide and titania coated substrates, respectively. The results indicate that the morphology and composition of the silver after photodeposition has a strong dependency on the morphology, crystallinity, and impurity content of the underlying semiconductor oxide. At the macroscale, this work demonstrates how the nanoscale features rapidly coalesce into a printed pattern through the use of masks or an X-Y gantry stage with virtually unlimited design control.

Photocatalytic Reduction of Carbon Dioxide over Shape-Controlled Titanium(IV) Oxide Nanoparticles with Co-catalyst Loading

Photocatalytic reduction of carbon dioxide (CO2) was carried out using titanium(IV) oxide (TiO2). Methanol (CH3OH) was detected as the main product, and trace amounts of formic acid, carbon monoxide, methane, and hydrogen were also detected. The prepared decahedral-shaped anatase TiO2 with larger {011} and smaller {001} exposed crystal faces showed larger CH3OH generation than that of commercial anatase TiO2 powder, ST-01 (Ishihara Sangyo Co.). Photodeposition of silver and gold nanoparticles on the decahedral-shaped anatase TiO2 induced an increase in CH3OH production because the deposited metal particles work as reductive sites for multi-electron reduction of CO2. Keywords: Photocatalysis, Reduction of carbon dioxide, Decahedral-shaped anatase Titanium(IV) oxide

나노 은을 광증착시킨 폴리(에틸렌 테레프탈레이트)/나노-TiO2복합체의 항균특성 연구

Nanocomposite films of poly(ethylene terephthalate)(PET) and nano titania(<TEX>$TiO_2$</TEX>) were prepared by melt compounding with a twin-screw extruder followed by hot pressing for the purpose of investigating antibacterial activity. FE-SEM, EDS and XRD measurements confirmed that nano <TEX>$TiO_2$</TEX> was successfully dispersed at the level of individual particles in the PET matrix. Silver was introduced through photocatalytic reduction by nano <TEX>$TiO_2$</TEX> under UV (254 nm) irradiation to the nanocomposite films after being immersed in aqueous solution <TEX>$AgNO_3$</TEX> (100 ppm Ag ion). Even at 1 wt% of <TEX>$TiO_2$</TEX> content, the nanocomposite with silver photodeposition exhibited strong antimicrobial activity against Klebsiella pneumoniae and Staphylococcus aureus in measurement by shaking flask method.

Gas phase photocatalytic bacteria inactivation using metal modified TiO2 catalysts

The present study describes the efficiency of heterogeneous photocatalytic reactor for the inactivation of three air born bacteria, Escherichia coli, Bacillus subtilis and Staphylococcus aureus using metal modified TiO2 photocatalysts and blacklight irradiation. The catalysts were prepared by photodeposition of silver, palladium or iron on commercial TiO2, immobilized on glass plates. X-ray photoelectron spectroscopy analysis was applied to determine the atomic percentage and species of each metal on the TiO2 surface, showing that 85% of silver, 73% of palladium and 45% of iron were present in metallic form on TiO2 surface. The plates were positioned on the inner lateral walls of a chamber through which the contaminated air flow passed for disinfection. Irradiation of bare TiO2 resulted in 50% inactivation of E. coli while 41% and 35% inactivation of B. subtilis and S. aureus were obtained, respectively. When metal modified TiO2 was applied, the inactivation of B. subtilis was improved to 91% using Pd–TiO2 while of S. aureus was improved to 94% with Fe–TiO2, showing in this case no significant difference when compared to Ag–TiO2 and Pd–TiO2. In contrast, inactivation of E. coli was not significantly increased when metal modified TiO2 was used, ranging from 47% to 57%.

Domain-selective photochemical reaction on oriented ferroelectric Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals

The domain-selective photoreduction of silver on (001) and (111) oriented 0.25Pb(In1/2Nb1/2)O3–0.44Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 (PIMNT) ferroelectric single crystals is investigated via piezoresponse force microscopy and Kelvin force microscopy. It is found that the crystallographic orientation as well as the direction and magnitude of the voltage used for domain switching strongly affects the amount and distribution of silver photodeposition. Additionally, the scanning direction of the tip during domain switching significantly affects silver photodeposition at c−/c+ domain boundaries when a high voltage is applied for domain switching. These phenomena can be explained and thus controlled by polarisation induced band bending, the space charge layer of the ferroelectric crystal and tip induced charge injection during domain switching. This work demonstrates a potential means to achieve an arbitrary spatial distribution of photodeposited metal.