Development of N,S-CDs fluorescent probe method for early detection of Cr(VI) in the environment

A fluorescent probe has been developed by synthesizing N,S co-doped carbon dots (N,S-CDs) through a microwave-assisted process for early detection of Cr(VI) in the environment. In this work, the optimization of irradiation time and ammonium persulfate mass as a source of N and S dopants were studied. The optimal conditions were then employed to synthesize N,S-CDs. Further research on pH, sensitivity, selectivity, and anti-interference to other metal ions were evaluated. Based on FT-IR spectra, it was confirmed that N and S atoms had been successfully passivated on the CDs surface as pointed by the presence of characteristic vibrations of N-H, C = N and C-N bonds for N atom as well as S-H and -SO3 for S atom. Characterization by TEM exhibited that N,S-CDs had an average size of 5 nm with some agglomerated parts. The highest fluorescence intensity was obtained at an irradiation time of 50 min with an ammonium persulfate mass of 50% (wt./wt. citric acid) at pH 5. The interaction mechanism between N,S-CDs and Cr(VI) can be associated with the fluorescence quenching process, especially Inner Filter Effect (IFE). By comparing fluorescence responses and Cr(VI) concentration, LOD and LOQ obtained were 0.038 ppm and 0.127 ppm, respectively. [GRAPHICS] .