O-phenylenediamine triggered two-step sequential fluorescence-enhanced sensor for speciation of Cr(VI)/Cr(III) in red wine/waters and photoreduction of Cr(VI).

Abstract

Speciation of Cr(VI)/Cr(III) and degradation of Cr(VI) with high toxicity to Cr(III) are required. We constructed a technique of o-phenylenediamine (OPD) triggered two-step sequential fluorescence-enhanced sensor for speciation of Cr(VI)/Cr(III) and photoreduction of Cr(VI). With FeN chelation between Fe3O4 QDs and OPD, the fluorescence intensity of Fe3O4 QDs was not only enhanced by 1.5 times, but that of Fe3O4 QDs/OPD sensor further increased by Cr(VI), and showed no response to Cr(III). Hence, OPD is the key triggered factor for establishing the sensor, and the detection limit of Cr(VI) by Fe3O4 QDs/OPD sensor was 2.44 μg L-1. Furthermore, under the irradiation at 385 nm, Fe3O4 QDs were activated and generated e-, which played a leading role in the reduction of Cr(VI) to Cr(III). The reduction efficiency of Cr(VI) was over 99 % within 2 h. This work provides an efficient, green and convenient method for rapid monitoring and treatment of Cr(VI).