Rapid determination of trace amount of chromium (VI) in water using carbon quantum dots as a fluorescence probe

Carbon quantum dots (CQDs) were prepared using one step hydrothermal method using ammonium citrate and lactose as nitrogen and carbon sources. The prepared CQDs were characterized using XRD, TEM, XPS, FT-IR, UV-Vis, and fluorescence spectroscopy. The fluorescence quantum yield of the CQDs is 17.6 %. The CQD fluorescence sensor based on the quenching effect by Cr (VI) was successfully developed for quantitative determination of Cr (VI). Moreover, CQDs exhibited a sensitive and selective response to Cr6+ compared to other common ions in water (Cu2+, Ca2+, Zn2+, Fe2+ and Mg2+). The prepared CQD fluorescence probe demonstrates good linear detection performance in the concentration range of 0.10 similar to 0.60 mg/L for Cr (VI) ion. It is thus potentially feasible to detect industrial wastewater with discharge standard of less than 0.50 mg/L.