Papers by Keyword: Ag-Doped

Abstract: In this manuscript, we report the simulation of electronic structures of TiO₂ doped with Ag using first-principles calculation, based on the density functional theory (DFT) The mechanism to improve the visible-light photocatalytic activity for TiO₂ doped with Ag. E_F was displaced into the valence band (VB), narrowing the band gap. An independent energy band was also introduced above the VB and an energy band with the width of 0.9 eV is introduced under the conduction band (CB), also resulting in the narrowing of the band gap. New VB and CB were formed by three orbitals O-2p, Ti-3d and Ag-4d. Composite TiO₂ nanotubes with Ag-doping were synthesized using the alkaline fusion and hydrothermal method under ambient atmosphere. XRD results indicated composite Ag-TiO₂ nanotubes ranging from the single anatase phase to the anatase and rutile mixed phase. XPS showed an increase in the surface acidity and photo catalytic activity of TiO₂ nanotubes due to the presence of OH radicals. Furthermore Ag-doping also facilitated the separation of photo-holes and photo-electrons and enhanced the optical properties.

Abstract: Ag-TiO2@MnO2 nanoparticles prepared by two-step hydrothermal method were characterized by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), Brunauer-Emmett- Teller (BET) and UV-Visible diffuse reflectance spectra (UV-Vis DRS). The degradation of rhodamine B (RhB) and 2, 4-dichlorophenol (2, 4-DCP) under visible light (λ≥420 nm) were used as probe reactions to investigate the photocatalytic activity of Ag-TiO2@MnO2. The results showed that the basic structure of Ag-TiO2@MnO2 was composed of TiO2 with anatase crystalline structure and α-MnO2 with cubic crysatalline structure. The optimal molar ratio nAg/nMn was 6%. Ag-TiO2@MnO2 had the highest photocatalytic activity in neutral medium because of composing and modifying of Ag. The decolorization rate of RhB reached 100% after 600 min and the mineralization rate of 2, 4-DCP was 47.0% after 30 hr. The oxidation process was dominated by the •OH generated in the system.

Abstract: Ag doped TiO2 was formed on the surface of carbon nanotube(CNT) by the sol-gel method, and characterized by TEM, XRD. The photocatalytic activity of the Ag-TiO2 /CNT was evaluated in degradation of methyl orange with a 300 W high pressure mercury lamp. Effect of Ag doping quantity on the photocatalytic activity of the photocatalys was investigated.The photocatalytic experiment indicated that the photocatalytic activity was firstly improved and then decreased with an increase of amount of Ag doped in TiO2 nanoparticles,the optimal doping quantity was 0.8% silver （ mass fraction of TiO2）, methyl orange could be degraded 99.3 % by Ag-TiO2/CNT under the optimal conditions after 120min.

Abstract: In this paper, the structure, electrical and optical properties and stabilities of Ag doped p-type ZnO thin films, prepared by electrostatic-enhanced ultrasonic spray pyrolysis were investigated. XRD and Hall data analyses indicated that the resistivity of 4at. % Ag doped p-type ZnO was low, without Ag₂O phase separation. The optical transmission spectra illustrated that optical band gaps decreases with the gradual increase of Ag dopant. Moreover, ZnO: Ag films placed for 10 days still showed p-type, but the optical transmittance decreased, suggesting that Ag_Zn in the ZnO: Ag thin films captured electrons to generate Ag_i, which reunited to be Ag nano-particles and decreased the optical transmittance of ZnO: Ag.

Abstract: SnS and Ag films were deposited on glass substrates by vacuum thermal evaporation successively, then they were annealed in N2 ambience at a temperature of 300 oC for 2h. By controlling the Ag evaporation voltage to roughly alter content of Ag in SnS films, different Ag-doped SnS films were obtained. The microstructures, composition and properties of the films were characterized with X-ray diffraction ( XRD ), atomic force microscopy(AFM) and some other methods. With the increase of Ag evaporation voltage (VAg), there exist new phases of Ag8SnS6 and Ag2S, whose intensity of diffraction peaks increases with the increasing Ag-dopant, and the average roughness of the films varies from 18.7nm to 23.6nm, and grain size increases from 192nm to 348nm. With the increase of VAg, the evaluated direct band gap Eg of the films decreases from 2.28eV(undoped) to 2.05eV (VAg=70V), the carrier concentration value and Hall mobility of the films diminishes from 2.048×1014cm-3 and 25.96 cm2.v-2.s-1 to 1.035×1016 cm-3 and 5.66 cm2.v-2.s-1, respectively; while the resistivity of the films decreases sharply from 1174Ω.cm(undoped ) to 107Ω.cm (VAg=70V ). All the films are of p-type conductivity. The above results show that the semiconducting properties of the SnS films have been improved by silver-doping.