Efficient Mechanochemical Conversion of Elemental Sulfur to Circularly Polarized Luminescent Sulfur Quantum Dots

The chiroptical property of sulfur quantum dots (Sdots) is unexplored. Herein, we develop an efficient mechanochemical synthesis strategy for chiroptically active l-Sdots, revealing their ground-state and excited-state chiroptical properties. The detailed structural study confirmed a polymeric sulfur core with an orthorhombic α-S8 phase stabilized and capped by cystine functionalities. l-Sdots exhibit strong photoluminescence (PL), originating from defect states of the sulfur vacancy, and consequently facilitate electron migration toward the surface groups. The ground-state chiroptical property arises from the outer shell of the sulfur core, enriched with cystine-related functionalities. Conversely, the circularly polarized luminescence (CPL) of l-Sdots, revealing their excited-state chiroptical nature with a g lum value of +2.2 × 10–3, arises from the ligand-to-sulfur core interaction and size effect. Additionally, Sdots find application as UV-active gel ink for anticounterfeiting measures. This study demonstrates physical insights into the structure and optical properties of Sdots and develops chiroptical Sdots for CPL-based photonic applications.