Capture, Store, and Discharge. Shuttling Photogenerated Electrons across TiO₂–Silver Interface

Abstract

UV irradiation of TiO(2) nanoparticles in the presence of Ag(+) ions results in the quantitative reduction and deposition of silver on its surface. Continued UV irradiation following the deposition of Ag on the TiO(2) surface causes a blue shift in the surface plasmon peak from 430 to 415 nm as these particles become charged with excess electrons. Under UV irradiation, both the charging and discharging of electrons occur at different rates, thus allowing the system to attain a steady state. Upon stopping the UV irradiation, a fraction of these electrons remain stored. The electron storage is dependent on the amount of Ag deposited on TiO(2) nanoparticles with maximum capacity seen at 8.6 μM of Ag in a suspension containing 5.8 mM of TiO(2). Such electron charging and discharging processes in semiconductor-metal composites need to be taken into account while evaluating the plasmon resonance induced effects in photocatalysis and photoelectrochemistry.

Photocatalysis: Basic Principles, Diverse Forms of Implementations and Emerging Scientific Opportunities

“…Nevertheless, the true role of noble metal nanoparticles in such systems remains the subject of debates. [160] For one reason, the reported enhancements due to the plasmonic effect were limited. Furthermore, how the introduction of metal to a semiconducting light absorber influences the nature of the metal-semiconductor junction can be complicated.…”

Plasmonic Rectenna for Efficient Conversion of Light into Electricity

“…However, in these recent metal-TiO2 Schottky diode structures [37][38][39][40][41][42][43][44][45][46][47], it would appear that the barrier layer was actually quite a bit thicker than 10 nm (probably in excess of 1 um) and further details was unable to be found in these papers. Semi-classical models did not account for non-equilibrium energy distributions of carriers, or do so through a localize lattice temperature.…”

“…First, Tatsuma et al [37,38,45] and other workers [42,46] proposed that the photoexcited electrons in the metal nanoparticles transferred from the metal particle to the TiO2 conduction band since the photoresponse of these metal-TiO2 diode structures was consistent with the absorption spectra of Au or Ag nanoparticles. Second, Kamat et al [43,44] and Li et al [47] have suggested that the noble metal nanoparticles act as electron sinks or traps in the metal-TiO2 diode structures to accumulate the photogenerated electrons, which could minimize charge recombination in the semiconductor films. Obviously, a better understanding of these effects is crucial in exploiting the beneficial aspects of metal nanoparticles in photovoltaics.…”

Silver metalized mixed phase manganese-doped titania: Variation of electric field and band bending within the space charge region with respect to the silver content

“…Further as the silver content increases on the surface of the photocatalyst, the surface area available for photon absorption decreases thereby decreasing the rate of photogeneration of electron-hole pair. The photocatalytic activity decreases with increase in the silver content above the optimum level [48,49]. Addition of the electron acceptors such as HP and APS to the reaction mixture is one of the strategies employed to decrease the rate of electron-hole recombination process.…”