Acidophilic S-doped carbon quantum dots derived from cellulose fibers and their fluorescence sensing performance for metal ions in an extremely strong acid environment

To achieve a rapid qualitative and quantitative evaluation of the total soluble heavy metal contamination in an aquatic environment, acidophilic fluorescent sensors with excellent metal ion detection capacity in strong acid (pH < 2) solutions require development. In this study, novel S-doped carbon quantum dots (S-CQDs) are synthesized from widely available cellulose fibers as carbon precursors and sulfuric acid as the carbonization agent and dopant. The S-CQDs exhibit extremely acidophilic high luminescence and a high quantum yield (up to 32%) in strong acid solutions. More importantly, the as-prepared S-CQDs are successfully utilized to detect Fe3+ in pH 0 solutions with excellent selectivity and sensitivity, with a detection limit as low as 0.96 μM. Based on the results, this study provides a foundation for the development of CQD sensors that can be used under strong acid conditions.