Fabrication of sulfur quantum dots via a bottom-up strategy and its application for enhanced fluorescence monitoring of o-phenylenediamine

Abstract

Nowadays, the synthesis of luminescent sulfur quantum dots (SQDs) mainly depends on a top-down method, which requires abnormally long reaction time by etching bulk sulfur powder. To overcome this limitation, a facile bottom-up strategy has been provided to fabricate fluorescent SQDs enabled by the reaction between thioacetamide (TAA) and hydrogen peroxide (H2O2) using carboxymethyl cellulose (CMC) as a passivation agent. Herein, TAA acts as sulfur source to release sulfide ions (S2-), which react directly with H2O2 to generate element sulfur to assemble the CMC-stabilized SQDs (SQDs@CMC). The prepared SQDs@CMC emits blue fluorescence, and owns good water dispersibility, superior photostability, excitation dependent luminescence and a reasonable quantum yield up to 9.31 %. Herein, the prepared SQDs@CMC combined with Cu2+ has a sensitive response toward o-phenylenediamine (OPD) by forming ternary SQDs@CMC/Cu2+/OPD complex, which can emit enhanced blue-shift fluorescence. The fluorescence of the ternary complex is 10 times higher than that of SQDs@CMC and the proposed SQDs@CMC-Cu2+ assembly has been successfully used to monitor OPD in various waters with high selectivity. Therefore, this paper not only provides a bottom-up strategy to prepare SQDs, but also develops a novel fluorescence “turn on” sensing platform for OPD detection.