Anion-Driven Bandgap\nTuning of AgIn(S<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub>)<sub>2</sub> Quantum Dots

Accurate tuning of the electronic and photophysical properties\nof quantum dots is required to maximize the light conversion efficiencies\nin semiconductor-assisted processes. Herein, we report a facile synthetic\nprocedure for AgIn(S<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub>)<sub>2</sub> quantum dots with S content (<i>x</i>) ranging from 1 to 0. This simple approach allowed us\nto tune the bandgap (2.6–1.9 eV) and extend the absorption\nof AgIn(S<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub>)<sub>2</sub> quantum dots to lower photon energies (near-IR)\nwhile maintaining a small QD size (∼5 nm). Ultraviolet spectroscopy\nstudies revealed that the change in the bandgap is modulated by the\nelectronic shifts in both the valence band and the conduction band\npositions. The negative overall charge of the as-synthesized quantum\ndots enabled us to make films of quantum dots on mesoscopic TiO<sub>2</sub>. Excited state studies of the AgIn(S<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub>)<sub>2</sub> quantum\ndot films demonstrated a fast charge injection to TiO<sub>2</sub>,\nand the electron transfer rate constant was found to be 1.5–3.5\n× 10<sup>11</sup> s<sup>–1</sup>. The results of this\nwork present AgIn(S<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub>)<sub>2</sub> quantum dots synthesized by the one-step\nmethod as a potential candidate for designing light-harvesting assemblies.