Band-Gap States of AgIn5S8 and ZnS–AgIn5S8 Nanoparticles

The size-dependent band-gap energies of AgIn 5 S 8 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 AgIn 5 S 8 nanoparticles. The band-gap transition in steady-state and time-resolved photoluminescence spectra indicated that the stable structure of the AgIn 5 S 8 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–AgIn 5 S 8 solid solution, as supported by the significant changes in the electronic band structures of the AgIn 5 S 8 nanoparticles. Controlling the size and stoichiometry allowed the emission of the Ag–In–S nanoparticles to be tuned in the entire visible regime.