Plasmon-Enhanced Photoluminescence and Photocatalytic Activities of Visible-Light-Responsive ZnS-AgInS2 Solid Solution Nanoparticles

Semiconductor-metal nanocomposite materials composed of ZnS-AgInS2 solid solution (ZAIS) nanoparticles and SiO2-coated Au particles were prepared, the particle distance between ZAIS and Au being precisely adjusted in nanometer scale by changing the thickness of the SiO2 coating layer on Au core particles. The SiO2 layer also acted as an insulator layer to prevent direct electron transfer from photoexcited ZAIS to Au particles. The photoluminescent (PL) and photocatalytic properties of ZAIS particles were modulated by the locally intensified electric field produced by photoexcitation of the localized surface plasmon resonance (LSPR) peak of Au particles. The PL intensity was enhanced with an increase in the distance between ZAIS and Au particles (d(ZAIS-AU)), up to about 21 nm, due to the enhancement of photoexcitation of ZAIS particles by the LSPR-induced electric field, but a further increase in d(ZAIS-AU) inversely decreased the PL intensity. The photocatalytic H-2 evolution rate with ZAIS particles immobilized at the appropriate distance from Au core particles was tunable by controlling the chemical composition of ZAIS. The plasmonic enhancement of photocatalytic activity was increased with an increase in the overlapping between the absorption properties of ZAIS and the LSPR peak of Au, the maximum enhancement factor obtained being about 2 for particles of AgInS2.