Abstract
Mercury and its compounds are widely distributed in the environment and have a significant negative impact on human health. In this paper, we report the development of a rapid and facile method for the detection of mercury ions (Hg2+) using heteroepitaxially synthesized unmodified silver nanoparticle-based smart probes using UV–Vis spectrophotometer and also through the naked eye by means of a paper-based sensor strip. The silver nanoparticles were prepared by heteroepitaxial growth method using gold seed nanoparticle of ~2.4 nm size as the template. The silver is grown on the seed particles by reducing the silver–ammonia complex using glucose, which resulted in Glu–AgNPs having an average size of 14.65 ± 3.53 nm. The sensing of mercury ions was carried out in aqueous solution and the reaction response was monitored by UV–Vis spectrophotometer. The interaction of Hg2+ with Glu–AgNPs resulted in a significant drop in the absorbance at 402 nm along with a prominent color change (from bright yellow to colorless) and wavelength shift (blue shift). The limit of detection (LOD) of this assay was found to be 100 nM (i.e., 20 ppb) with a good linearity in the concentration range of 100–10 mM. To further ease the detection process and make it field deployable, we attempted to develop a paper-based sensor strip by immobilizing Glu–AgNPs on a paper strip. Upon interaction with mercury solution of varying concentrations, the decoloration of the spots could be observed easily through naked eyes, with the limit of detection under sub-optical conditions being 1 µM.
Highlights
Accumulation of mercury, in every aspect of environmental samples including water and soil, can cause severe health problems to animal and human beings
The faster synthesis of nanoparticles was attributed to the presence of pre-formed seed AuNPs, which facilitated in bypassing the burst nucleation phase and resulting in their rapid seedmediated growth
The extinction maxima of Glu–AgNPs was observed at 402 ± 3.75 nm (n [ 10) with full width at half maximum (FWHM) value of 58.45 ± 1.15 (n [ 10) indicating the formation of monodisperse nanoparticles with very narrow size distribution (Fig. 1a)
Summary
Accumulation of mercury, in every aspect of environmental samples including water and soil, can cause severe health problems to animal and human beings. All the oxidation states of mercury are toxic, Hg2? Form is the most stable and exists primarily in surface water due to its high aqueous solubility. Once introduced into the aquatic ecosystem, it accumulates in the food chain in the form of methylmercury (a neurotoxin), especially in the edible fishes, and can cause prenatal brain damage, various cognitive and motion disorders, and the most deadly Minamata disease (Trasande et al 2005; Graeme 1998). Can create serious health risks to human body due to its highly toxic effects on brain, kidney, and immune and nervous systems (Clarkson and Magos 2006; Tchounwou et al 2003). Monitoring the Hg2? ions in aqueous system is highly demanding so as to maintain the environment
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