Thiolate-Mediated Photoinduced Synthesis of Ultrafine Ag₂S Quantum Dots from Silver Nanoparticles

Photoinduced syntheses offer significant advantages over conventional thermal strategies, including improved control over reaction kinetics and low synthesis temperatures, affording nanoparticles with nontrivial and thermodynamically unstable structures. However, the photoinduced syntheses of non-metallic nanocrystalline products (such as metal sulfides) have not yet been reported. Herein, we demonstrate the first photoinduced synthesis of ultrafine (sub-2 nm) Ag₂S quantum dots (QDs) from Ag nanoparticles at 10 °C. By thorough investigation of the mechanism for the transformation, a fundamental link was established between the intrinsic structures of the molecular intermediates and the final Ag₂S products. Our results confirm the viability of low-temperature photochemical approaches in metal sulfide synthesis, and demonstrate a new rule which could be followed in it.