Surface photovoltage spectroscopy of Ag-modified composite TiO_2 nanotubes

Ag-modified,composite TiO2 nanotubes were synthesized using molten alkali-hydrothermal method under an ambient atmospheric pressure.The organization and morphology of the composite TiO2 nanotubes were characterized.Nanotubes have clear,uniform and neat morphology with diameter of around 3 to 5nm,each nanotube composed of 3 to 5 layers and wall thickness of around 0.5nm.In particular,TiO2 and Ag nanoparticles clearly adhere in between nanotubes and at the exterior surface of nanotubes.XRD results display that,the composite TiO2 nanotubes from the single anatase phase to the anatase and rutile mixed phase.The band-band transition occurs within a wavelength span of 350nm.SPS(surface photovoltage spectroscopy)and FISPS(electric field-induced surface photovoltage spectroscopy) demonstrate the bound exciton sub-band-gap transition characteristics from its asymmetric changes corresponding to changes in polarity of the external electric field.Ag modifing has imposed considerable influence on both the photovoltaic response of composite TiO2 nanotubes and the separation of photoinduced electrons and holes at the surface of nanotubes.