Effect of doping in small-size hybrid nanostructures for plasmonic catalysis

Abstract

The effect of doping on the lowest quantum state of hot electron trapped in the semiconductor shell of small size hybrid nanoparticles is investigated. Assuming a spherical Ag-AgBr hybrid nanoparticle with a metal core and a semiconductor shell, we study the changes in the spatial profile of the contact electric potential in the Schottky barrier as a function of the doping density under the Sze approximation of a completely depleted layer. The energy of the lowest quantum state of an electron in the semiconductor shell is estimated along with the tunneling time into the metal core. It is found that when the characteristic size of the depletion layer of the Schottky barrier exceeds the size of the semiconductor shell, this energy varies throughout the Schottky barrier height by changing the shell thickness and the doping density, with the tunneling lifetime varying from subpicoseconds to submicroseconds. This possibility can be exploited to improve the efficiency of plasmonic photocatalysis with small-sized hybrid nanoparticles: By adjusting the energy of the discrete electron state to the given lowest unoccupied molecular orbit level of the chemical adsorbed on the surface of the hybrid nanoparticle, one should expect the resonance transfer of an electron, thus a dramatic increase in the rate of photocatalysis. The proposed method introduces Quantum-Size Resonance-Enhanced Photocatalysis in the hybrid structure.