A novel colorimetric probe for highly selective recognition of Hg2+ ions in aqueous media based on inducing the aggregation of CPB-capped AgNPs: accelerating direct detection for environmental analysis

Abstract

In this study, we have developed a novel and highly selective naked-eye colorimetric probe for the detection of mercury ions (Hg²⁺) in aqueous solution, using cetylpyridinium bromide (CPB)-capped colloidal silver nanoparticles (AgNPs), based on induced aggregation. The synthesized AgNPs and their interaction with Hg²⁺ were characterized using UV-Vis absorption spectroscopy, Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) measurements and zeta potential measurement techniques. The color of the AgNP solution changed from yellowish-brown to colorless within a few minutes following the addition of Hg²⁺, resulting in a blue shift from 408–354 nm with quenching in the absorption spectra. Under the most favorable conditions, the calibration plot of (A₀−A) against concentration of Hg²⁺ was linear in the range of 0.5–10 μg mL⁻¹ with a correlation coefficient of 0.9931. The concentration of Hg²⁺ is quantitatively determined using a UV-Vis spectrophotometer with a Limit of Detection (LOD) of 0.80 μg mL⁻¹. In addition, this method shows an excellent selectivity towards Hg²⁺ over sixteen other interfering cations tested. The accuracy and reliability of the method were further ascertained for the detection of Hg²⁺ from water bodies via a standard addition method, with percentage recoveries in the range of 99.96–100.13%. The probable mechanism for the observed color changes was also discussed. The method is simple, rapid, specific, and highly selective with good precision.