Controlling the Electronic Energy Structure of ZnS–AgInS2 Solid Solution Nanocrystals for Photoluminescence and Photocatalytic Hydrogen Evolution

Abstract

Simultaneous control of the size and chemical composition is an advantageous strategy to obtain the desired photochemical properties of multinary semiconductor nanocrystals, ZnS-AgInS2 solid solution ((AgIn)xZn2(1–x)S2, ZAIS) nanocrystals (NCs), being different from conventional binary nanocrystals. The energy gap (Eg) of ZAIS NCs was enlarged with a decrease in particle size due to the quantum size effect or with an increase in ZnS content in the ZAIS solid solution. The levels of the conduction band edge and valence band edge, determined by photoelectron spectroscopy in air, were shifted more negatively and more positively, respectively, with an increase in Eg. A volcano-type dependence was observed between the PL quantum yield (QY) and the size of ZAIS NCs, in which the optimal PL QY for each x value was obtained at a similar particle size around 5–6 nm, except for x = 1.0, and maximum QY was recorded to be 79% for ZAIS NCs prepared with x = 0.5. The photocatalytic activity for H2 evolution was also gr...