A principle of semiconductor nanophotocatalysis – a new trend in photochemistry deals with the photocatalytic redox-reactions with the participation of semiconductor nanoparticles. The origin of various size-dependent explanations in the semiconductor photocatalysis are spot light with the special attention paid to the quantum size effects originating from a spatial confinement of the photogenerated charge carriers (excitons) in ultra-small semiconductor nanoparticles (quantum dots). Our focus was the specifics of quantum-confined semiconductor nanoparticles including the size-dependent optical properties (the position and shape of absorption and photoluminescence bands, the oscillator strength of interband electron transitions, etc.), thermodynamic characteristics (the band gap, the potentials of conduction and valence band edges, the nature, number and depth of charge trapping sites, etc.), as well as the dynamics of photogenerated charge carriers (charge migration in semi¬conductor nanoparticles, its localization on the structure defects, interfacial charge transfer, etc.). The consequences of spatial confinement were characterized in semiconductor nanoparticles affecting their photocatalytic behavior. The development of the photocatalytic properties in narrow-band-gap semiconductors at the nanoscale increased a number of photocatalytic reactions for a given nanocrystalline semiconductor as compared with the bulk material. The acceleration of photocatalytic reactions enhanced with the participation of semiconductor nanoparticles due to their size-dependent growth of the energy in charge carriers. The photoinduced polarization caused by the accumulation of excessive charge by semiconductor nanoparticles resulted an increase of their photocatalytic activity. The specific features of the photocatalytic behavior of semiconductor nanoparticles were size-related phenomena in the photocatalytic metal reduction, photocatalytic formation of binary semiconductor nanoheterostructures, photoinduced poly¬merization of acrylic monomers, photocatalytic reduction of sulfur compounds, and photocatalytic water reduction with the participation of semiconductor nanoparticles. The photochemical behavior of quantum-confined semiconductor nanoparticles was observed under powerful pulse illumination. The simultaneous and additive influences of different size effects showed dependence upon the photocatalytic properties of semiconductor nanoparticles. In conclusion, perspectives of future development of the photocatalytic systems based on nanostructured semiconductors broaden the number of nanophotocatalysts and photocatalytic processes, as well as the benefits of the utilization of such systems in modern nanotechnology.
Journal: TechConnect Briefs
Volume: 2, Nanotechnology 2010: Electronics, Devices, Fabrication, MEMS, Fluidics and Computational
Published: June 21, 2010
Pages: 73 - 76
Industry sector: Sensors, MEMS, Electronics