Gelatin-templated mesoporous titania for photocatalytic air treatment and application in metal chalcogenide nanoparticle-sensitized solar cells.

Mesoporous titania as powders and thin films on ITO were prepared using gelatin as an available and non-expensive pore-forming agent. The mesoporous TiO2 manifested a much higher photocatalytic activity in the gas-phase air oxidation of ethanol and acetaldehyde than the commercial nanocrystalline TiO2 P25 (Degussa Corp.). The mesoporous ITO/TiO2 films exhibited 12-14% efficiency of photocurrent generation in aqueous Na2S electrolyte when illuminated by UV light. Deposition of CdS and PbS nanoparticles onto the surface of ITO/TiO2 further increases the photocurrent yields and expands the light sensitivity range of the films to 500-520 nm (CdS) and to 650-700 nm (PbS).

Size-dependent photoinduced interactions between ZnO nanocrystals and a nitronyl nitroxide radical Nit(o-OH)Ph.

Spectral and photochemical properties of ZnO nanocrystal solutions containing free nitronyl nitroxide radical 2-(o-hydroxyphenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (Nit(o-OH)Ph) were studied. The ZnO photoluminescence quenching by Nit(o-OH)Ph was observed and analysis of the dependences of ZnO photoluminescence intensity on radical concentrations revealed the prevalence of a static mechanism for this process. The changes in spectral properties of colloidal ZnO nanocrystal solutions in the presence of a Nit(o-OH)Ph radical under illumination were studied. The nitronyl nitroxide was found to undergo photoinduced reduction to the corresponding hydroxylamine both via the excited-state interaction with ethanol and capturing of the ZnO conduction band electrons. Photoreduction of the radical was observed under illumination with light of λ > 460 nm in the presence of 4.2 nm ZnO nanocrystals, while no changes took place in the case of larger 4.8 nm ZnO nanocrystals. This pronounced size effect was interpreted in terms of much stronger spatial exciton confinement in the smaller ZnO nanocrystals favouring the irreversible electron transfer from the photoexcited radical.

A spectroscopic and photochemical study of Ag(+)-, Cu(2+)-, Hg(2+)-, and Bi(3+)-doped Cd(x)Zn(1-x)S nanoparticles.

A combination of stationary and time-resolved absorption and photoluminescence spectroscopy with flash and steady-state photolysis of Ag(+), Cu(2+), Hg(2+), or Bi(3+)-doped Cd(x)Zn(1-)(x)S nanoparticles was used to assess the nature of the doping influence upon the optical properties of Cd(x)Zn(1-x)S nanoparticles. The relationships between the type and the concentration of a dopant and the dynamics of the photoinduced processes in the doped nanoparticles are derived and discussed. A correlation is found between the magnitude of doping-induced changes in the intensity and decay dynamics of the deep trap photoluminescence and an enhancement of the transient bleaching recovery and acceleration of the photocorrosive degradation of the doped Cd(x)Zn(1-x)S NPs compared to the undoped ones. The impact of the dopant upon the intensity of the luminescence and microsecond transient bleaching bands was found to grow substantially from Ag(+) to Cu(2+), Hg(2+) and Bi(3+). The same trend was found to hold for the acceleration of the steady-state photochemical corrosion of doped Cd(x)Zn(1-x)S nanoparticles. The differences among the effect of the dopant ions studied were interpreted in terms of the depth and charge of surface states created by Cd(2+) (Zn(2+)) substitution by a dopant.