Microwave-assisted green synthesis of ultrasmall fluorescent water-soluble silver nanoclusters and its application in chiral recognition of amino acids

In this article, we established a fluorescent chiral recognition and detection method for cysteine based on the L-glutathione (L-GSH)-stabilized Ag nanoclusters (AgNCs) with high selectivity and sensitivity. A fast and green microwave (MW)-assisted strategy has been employed for synthesizing water-soluble fluorescent L-GSH–AgNCs. The reaction time was shortened from hours to several minutes. The synthetic process utilized L-glutathione as a stabilizing agent and a reducing agent without any other toxic reducing agent, such as NaBH4 or N2H4. The method is environmental friendly. Due to the different responses to AgNCs from chiral cysteine, we found D-cysteine hardly affects the fluorescence intensity of the AgNCs, whereas L-cysteine distinctly weakened its fluorescence intensity. This experiment indicated that fluorescence quenching efficiency of AgNCs was proportional to the concentration of L-cysteine in the range from 0.025 to 50 μmol L−1.