Nitrilotriacetate Stabilized Gold Nanoparticles: A Novel Strategy for Colorimetric Detection of Cr(III)/Cr(VI) and Mechanistic Aspect
Nitrilotriacetate (NTA) is reported to behave as both reductant and stabilizer for gold nanoparticle (AuNP) preparation in one-pot synthesis and colorimetric assay. The goal is to avoid the negative influence of citrate residues on the detection of chromium ions, because citrate always remained in the modification of AuNPs by common ligand-exchange methods. This colorimetric assay was shown to be highly efficient and selective for the detection of Cr(III) and Cr(VI). The detection limits of Cr(III) by nake eye was as low as 2.0 µM. Interestingly, a much lower detection limit was found for Cr(VI) than that of Cr(III) (0.4 µM by nake eye). Additionally, Cr(III) and Cr(VI) were easily distinguished upon pretreatment with K2CO3. The feasibility of this technique was evaluated for the successful detection of Cr(III) and Cr(VI) in tap water samples with good recoveries. The detection mechanism is discussed with the help of several techniques including transmission electron microscopy (TEM) images, FT-IR spectra, Zeta potential (ζ-potential) data and inductively coupled plasma mass spectrometry (ICP-MS) measurements.