Synthesis of highly structured spherical Ag@Pt core-shell NPs using bio-analytes for electrocatalytic Pb(II) sensing

Abstract

This research work is taken up to synthesize highly crystalline and ordered Ag@PtNPs core-shell nanoparticles (NPs) via a bio-inspired route using Psidium guajava leaves-extract with high ascorbic acid equivalent (284 /100 g fresh leaves). A short microwave exposure (900 W and 300 s) led to a quick formation of AgNPs-seed (25.7 nm avg). The seed was then subjected for a rapid growth (240 s) of Pt-shell (4.55 nm) which was synergized by bio-extract and microwave irradiation forming Ag@PtNPs. The graphite electrode was surface-modified using these NPs for electrocatalytic sensing of Pb(II) by square wave anodic stripping voltammetry. The electron transfer resistance of bare graphite was reduced by 1.2, 26, and 2.9 folds, respectively, with PtNPs, AgNPs, and Ag@PtNPs modification. The sensitivity of Ag@PtNPs/graphite electrode for Pb(II) sensing calculated against the electroactive area was about 4.5 and 20.2 folds higher than PtNPs/graphite and AgNPs/graphite electrodes at −0.43 V vs. Ag/AgCl and pH 5. The limit of detection was as low as 0.8 nM. The response of the sensor (max. 1.98 % variation in peak current) was almost invariant in the presence of co-ions (Cd(II), Cu(II) and Hg(II) from 0.25 to 10 μM). The sensor it could effectively determine Pb(II) from environmental water samples collected from river, domestic supply and sewage treatment plant.