Two‐Step Oxidation Synthesis of Sulfur with a Red Aggregation‐Induced Emission

Abstract Sulfur is not normally considered a light‐emitting material, even though there have been reports of a dim luminescence of this compound in the blue‐to‐green spectral region. Now, it is shown how to make red‐emissive sulfur by a two‐step oxidation approach using elemental sulfur and Na 2 S as starting materials, with a high photoluminescence quantum yield of 7.2 %. Polysulfide is formed first and is partially transformed into Na 2 S 2 O 3 in the first step, and then turns back to elemental S in the second step. The elevated temperature and relatively oxygen‐deficient environment during the second step transforms Na 2 S 2 O 3 into Na 2 SO 3 incorporated with oxygen vacancies, thus resulting in the formation of a solid‐state powder consisting of elemental S embedded in Na 2 SO 3 . It shows aggregation‐induced emission properties, attributed to the influence of oxygen vacancies on the emission dynamics of sulfur by providing additional lower energy states that facilitate the radiative relaxation of excitons.