Spectrofluorimetric determination of Cr(VI) and Cr(III) by quenching effect of Cr(III) based on the Cu-CDs with peroxidase-mimicking activity.

Abstract

The study presents a spectrofluorimetric method for the determination of Cr(III) based on 2,3-diaminophenazine (DAP) as fluorescent nano sensor. With the peroxidase-mimicking activity of copper-doped carbon dots (Cu-CDs), colorless o-phenylenediamine (OPD) was oxidized to fluorescent DAP in the presence of H2O2 via generation of hydroxyl radicals. The Cr(III) was found to decrease the fluorescent intensity of the Cu-CDs-mediated OPD oxidation system. Cr(VI) species were reduced to Cr(III) by employing 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) as the reductant, and a novel spectrofluorimetric method for the highly sensitive detection of speciation Cr(VI) and Cr(III) was developed. The Cu-CDs nanozyme was prepared from ethylenediaminetetraacetic acid copper disodium salt (Na2[Cu (EDTA)]) by one-step pyrolysis method. Under optimal conditions, the fluorescence intensity of DAP is linearly proportional to the Cr(III) ion concentration in the range of 5×10-6 to 1.5×10-4molL-1 and the detection limit is 1.2×10-7molL-1. The method has a good anti-interference performance against some metal ions, such as, Hg2+, Co2+, Cu2+, Mg2+, Ba2+, K+, Mn2+, Ni2+, Al3+, and Fe3+. The proposed method was successfully applied in the determination of Cr(VI) and Cr(III) in water samples.