Porous carbon quantum dots: one step green synthesis via L-cysteine and applications in metal ion detection

A bottom-up and wet-chemical method employing L-cysteine as a precursor has been proven to be an effective strategy for producing fluorescent porous CQDs for the first time, which exhibit stable and strong photoluminescence, and reach a quantum yield of 18.1%. Under optimum conditions, a good linear semilogarithmic correlation between the quenching efficiency (F0/F) and the concentration of chromium ions, even at 10−8 mol L−1, was achieved, and the limit of detection was 1.491 × 10−9 mol L−1. The quenching of the porous CQDs’ fluorescence intensity by Cr6+ may result from the inner filter effect. The application of these porous CQDs as probes for the detection of chromium ions is good, and they can be readily, rapidly and efficiently employed in the natural environment.