Role of 5-thio-(2-nitrobenzoic acid)-capped gold nanoparticles in the sensing of chromium(vi): remover and sensor

Abstract

This study describes a simple, rapid method for sensing Cr(VI) using 5-thio-(2-nitrobenzoic acid) modified gold nanoparticles (TNBA-AuNPs) as a remover for Cr(III) and as a sensor for Cr(VI). We discovered that TNBA-AuNPs were dispersed in the presence of Cr(VI), whereas Cr(III) induced the aggregation of TNBA-AuNPs. Due to this phenomenon, TNBA-AuNPs can be used as a sorbent material for the removal of >90% Cr(III), without removing Cr(VI). After centrifuging a solution containing Cr(III), Cr(VI), and TNBA-AuNPs, Cr(III) and Cr(VI) were separately present in the precipitate and supernatant. In other words, TNBA-AuNPs are capable of separating a mixture of Cr(III) and Cr(VI). The addition of ascorbic acid to the supernatant resulted in a reduction of Cr(VI) to Cr(III), driving the aggregation of TNBA-AuNPs. The selectivity of this approach is more than 1000-fold for Cr(VI) over other metal ions. The minimum detectable concentration of Cr(VI) was 1 μM using this approach. Inductively coupled plasma mass spectrometry provided an alternative for the quantification of Cr(III) and Cr(VI) after a mixture of Cr(III) and Cr(VI) had been separated by TNBA-AuNPs. The applicability of this approach was validated through the analysis of Cr(VI) in environmental water samples.