Colorimetric and paper-based detection of lead using PVA capped silver nanoparticles: Experimental and theoretical approach

We report a plasmonic colorimetric sensing strategy using polyvinyl alcohol (PVA) modified silver nanoparticles (AgNPs) and paper-based analytical devices (PADs) for selective detection of lead (Pb). Method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) absorption band of AgNPs/PVA in visible region after the addition of Pb(II) using UV-Vis spectrophotometry and color intensity of PADs was recorded with Smartphone followed by the processing in ImageJ software. The mechanism of color change and red shift (Delta lambda) of LSPR band from 410 nm to 550 nm is due to the interaction of Pb(II) ions towards the PVA through strong ion-dipole interaction perturbing the stability AgNPs which further directed the aggregation of particles. The density functional theory (DFT) using Gaussian (C.01) program assisted by experimental data was used to elucidate the plausible mechanism for selective detection of analyte. The calibration curve gave a good linearity in the range of 20-1000 mu gL(-1) with limit of detection (LOD) of 8 mu gL(-1) by colorimetry and 50-1000 mu gL(-1) with LOD value of 20 mu gL(-1) using PADs. In addition, the results obtained with UV-Vis and PADs were compared with ICP-AES for quantitative determination of Pb(II) in different water samples. The advantages of using AgNPs/PVA as plasmonic colorimetric probe and PADs found to be simple, low cost and selective for determination of lead from surface water and industrial waste water samples.