| Summary: | Heavy metals (HMs), pollution of major environmental matrices and its attendant effects on human health and the environment, continue to generate huge scientific interest, particularly in monitoring and detection. Herein, the optical property of carboxymethyl cellulose stabilized silver nanoparticles (CMC-AgNPs), supported with ascorbic acid, is exploited as a colorimetric probe for the detection of toxic Au3+ ion in solution. The as-synthesized CMC-AgNPs showed sharp absorption maximum at 403 nm, with sparkling yellow color and average particles size distribution less than 10 nm. It was further characterized using ATR-FTIR, TEM, FESEM/EDS, XRD and DLS/zeta potential analyzer. Au3+ ion detection strategy involves the addition of ascorbic acid (AA) to a pH adjusted CMC-AgNPs, followed by the analyte addition. AA would facilitate the reduction of Au3+ on CMC-AgNPs (seed), with resultant color perturbations from light yellow to yellow, orange, ruby red and purple red, under 8 min incubation, at room temperature (RT). The CMC-AgNPs could also serve as a catalyst, by promoting AA mediated reduction of Au3+, in-situ. Moreover, we propose, that the color and the absorption spectra change is attributed to the deposition of gold nanoparticles (AuNPs), on the CMC-AgNPs/AA probe, to form (CMC-Ag@Au) nanostructures, depending on the analyte concentration. Absorbance ratio (A540/A403) showed good linearity with Au3+ concentration from 0.25 to 100.0 µM, and an estimated LOD of 0.061 µM. The assay was applied to Au3+ detection in environmental wastewater sample, showing satisfactory real sample detection potentiality.
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