Effect of the method of production of TiO2/CdS nanohetero film structures on the effectiveness of photoinduced charge separation

Abstract

The properties of TiO 2 /CdS nanohetero structures produced by the chemical and photocatalytic deposition of CdS nanoparticles on the surface of nanocrystalline films of TiO 2 under the conditions of laser pulse photolysis were studied. It was shown that in the case of photocatalytically formed TiO 2 /CdS nanocomposites the spatial separation of the photogenerated charges between the components of the hetero structure, leading to the formation of intermediates of the photochemical transformations (Ti III centers in the TiO 2 nanoparticles and S -× radical-anions in the CdS nanoparticles), is an order of magnitude more effective.In the arsenal of methods used today for the production of semiconducting (SC) nanostructures a special position is occupied by photochemical methods that make use of the tendency of the initial reagents to undergo transformations leading to the formation of semiconducting nanoparticles and the ability of the semiconducting materials to induce photocatalytic processes as a result of which binary semiconductors or metal-SC nanohetero structures are formed [1]. These methods make it possible to control freely the properties of the obtained products and in particular the size and the optical characteristics of the semiconducting nanoparticles and, in the case of semiconducting nanohetero structures, to obtain photocatalysts for redox transformations more active than those produced by traditional methods. Thus, we established [2] that TiO 2 /CdS, TiO 2 /PbS, and TiO 2 /Cu x S nanohetero structures are formed on the surface of nanocrystalline films of titanium dioxide during the photocatalytic reduction of sulfur by ethanol in the presence of Cd II , Pb II , or Cu II salts. It was shown on the basis of atomic-force microscopy that cadmium sulfide is deposited in the form of nanorods with lengths up to 70-80 nm normal to the surface of the TiO 2 film and consisting of individual CdS particles 5-6 nm in diameter. It was suggested that on account of their anisotropic 302 0040-5760/09/4505-0302

Photodeposition of Ag or Pt onto TiO2 Nanoparticles Decorated on Step Edges of HOPG

“…31,32 Also, nanoparticles photocatalytically deposited onto TiO 2 show evidence of effective charge transfer compared to deposition from solution. 33 Furthermore, the photocatalytic mechanism allows for the fabrication of multicomponent nanostructures through charge transfer and reduction, ensuring good contact between the components. 34 The photodeposition of nanoparticles onto TiO 2 films from a direct photocatalytic mechanism (heterogeneous photodeposition) cannot be visually distinguished from formation of nanoparticles in solution followed by adsorption onto the surface (homogeneous photodeposition).…”

“…Nanoparticles can be loaded onto TiO 2 via a photocatalytic mechanism or from nanoparticle formation in solution followed by adsorption onto the surface. The photocatalytic mechanism offers several advantages including the control of size and distribution of nanoparticles on TiO 2 . , Also, nanoparticles photocatalytically deposited onto TiO 2 show evidence of effective charge transfer compared to deposition from solution . Furthermore, the photocatalytic mechanism allows for the fabrication of multicomponent nanostructures through charge transfer and reduction, ensuring good contact between the components .…”