Abstract
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.
Highlights
Due to its large-scale applications in metallurgy, chemical engineering, steel making and many other areas, chromium is extensively discharged from the industries; this poses a severe threat to the environment and human health.[1,2,3] Compared with trivalent chromium, which is an essential nutrient for humans, hexavalent chromium is a lethal toxicant to human beings.[4,5,6] According to the rules of the United States Environmental Agency, the upper limit of Cr(VI) in drinking water is 0.05 ppm
To clarify the mechanism of the sensitivity and selectivity of the as-prepared sensor, a comparison was made between our products and those capped with only chitosan (C-Au)
According to an article reported by Sugunan et al, the purpose of the surface modi cation of acid-functionalized gold nanoparticle (Au NP) by pure chitosan is to distinguish the intensity of the UV-vis absorption peaks corresponding to the different concentrations of analytes.[46]
Summary
Due to its large-scale applications in metallurgy, chemical engineering, steel making and many other areas, chromium is extensively discharged from the industries; this poses a severe threat to the environment and human health.[1,2,3] Compared with trivalent chromium, which is an essential nutrient for humans, hexavalent chromium is a lethal toxicant to human beings.[4,5,6] According to the rules of the United States Environmental Agency, the upper limit of Cr(VI) in drinking water is 0.05 ppm. Some convenient and efficient detection strategies have been established such as uorescence,[14,15,16,17,18] electrochemical,[19,20,21] and surface plasmon resonance (SPR) methods.[22,23] Among these solutions, the sensors based on the SPR technique have received signi cant attention due to their characteristic superiorities such as convenience, high sensitivity, rapidity, and bio-friendliness.[21,24,25,26,27] They are triggered by a physical contact or a chemical reaction of the analyte with the surface of the sensors, usually in the forms of nanoparticles or thin lms; this causes shi s of the plasmon resonance peaks. The selectivity of this system towards other ions, including Cr(III), is relatively high; based on these ndings, the concentration of Cr(VI) in some practical samples has been tested in this study
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