Highly selective and sensitive probes for the detection of Cr(VI) in aqueous solutions using diglycolic acid-functionalized Au nanoparticles

In this study, a variety of diglycolic acid-functionalized gold nanoparticle (Au NP) probes are reported, which are highly sensitive for the detection of chromium ions, Cr(VI) ions, at low concentrations in aqueous solutions based on the application of surface plasmon resonance (SPR) theory. Due to its outstanding affinity for Cr(VI) ions, the capped diglycolic acid would induce the aggregation of the NP probes upon encountering them; this was evidenced by the obvious red-shifting of the SPR peak and the enlarged size of the NPs. For the same reason, the selectivity of the probe for Cr(VI) against other heavy metal ions was found to be remarkable. Under optimized conditions, the probe showed the limit of detection (LOD) of 0.32 ppb for Cr(VI) and a linear detection scale ranging from 0.32 ppb to 0.1 ppm. To the best of our knowledge, this is probably the lowest LOD reported for Cr(VI) detection among those of the methods based on SPR.