Novel N, F co-doped carbon dots to detect sulfide and cadmium ions with high selectivity and sensitivity based on a “turn-off-on” mechanism

Abstract

In this work, novel nitrogen, fluorine co-doped carbon dots (N, F-CDs) have been synthesized by a hydrothermal method using melamine and 2, 4-difluorobenzoic acid as precursors. The obtained N, F-CDs exhibit excellent optical stability with high quantum yield. The N, F-CDs are highly selective to S²⁻ detection by forming N, F-CDs@S²⁻, with a detection limit of 168 nM. The N, F-CDs@S²⁻ were shown to be a highly selective Cd²⁺ detector by forming CdS, with a detection limit of 340 nM. The fluorescence quenching of N, F-CDs by S²⁻ occurs via a static quenching mechanism and the fluorescence recovery was due to the high affinity of Cd²⁺ to S²⁻. The fluorescent sensor was used to determine Cd²⁺ and S²⁻ in tap waters with satisfactory results.