Band-Gap States of AgIn₅S₈ and ZnS-AgIn₅S₈ Nanoparticles

The size-dependent band-gap energies of AgIn₅S₈ nanoparticles were directly measured for the first time using absorption and photoluminescence spectroscopies, which enabled an explanation of the evolution of the band-gap energy with the quantum-confinement effect in AgIn₅S₈ nanoparticles. The band-gap transition in steady-state and time-resolved photoluminescence spectra indicated that the stable structure of the AgIn₅S₈ nanoparticles was the cubic phase. The electronic band structures of the Ag-In-S nanoparticles were mainly related to the crystal structures, although the stoichiometry affected the band energies to some extent. Zn doping led to the formation of a ZnS-AgIn₅S₈ solid solution, as supported by the significant changes in the electronic band structures of the AgIn₅S₈ nanoparticles. Controlling the size and stoichiometry allowed the emission of the Ag-In-S nanoparticles to be tuned in the entire visible regime.