Gallotannin functionalized gold nanoparticles for rapid, selective and sensitive colorimetric detection of Ag+ in aqueous medium: Approach to eco-friendly water analysis

[Display omitted] •Ease of preparation for gold nanoparticles (AuNPs) using gallotannin (GT).•Sensitive, selective and rapid naked eye colorimetric detection of Ag+ only.•GT-AuNPs interacts with Ag+ forms nano clusters (GT-AuNPs-AgNPs).•Lower detection limit for Ag+ = 0.22 ng/mL (2.05 nM).•Prepared GT-AuNPs explored for Ag+ detection in real environmental samples. We have prepared gallotannin (GT) capped gold nanoparticles (AuNPs) for rapid, sensitive and naked eye colorimetric detection of silver ion (Ag+) in aqueous medium. Amongst the 21 different metal ion studied for absorption titration, only Ag+ ion induces the change in color and spectral properties of GT capped AuNPs. The formation of GT capped AuNPs and its interaction with Ag+ were discussed with change in pink to yellowish brown color, hypsochromic spectral shift in absorption maximum wavelength, decrease in zeta potential and increase in particle size. The sequential addition of Ag+ to the colloidal suspension of GT capped AuNPs simultaneously increases the absorbance along with hypsochromic shift in wavelength maxima. The absorption titration results were fits well to calibration plot in linearity range of 0–1 ng/mL of Ag+ showing correlation coefficient (R2) of 0.9983. The lower detection limit estimated for Ag+ is 0.22 ng/mL (2.05 nM) that shows sensitivity and selectivity of present analytical method towards detection of Ag+ in aqueous solution. The present method includes practical application for quantitative determination of Ag+ in real environmental water samples. Thus, the present study offers simple, cost-effective, selective, sensitive, speedy, profitable and naked eye detection of Ag+ in aqueous medium.