Surface-assisted electron transfer reaction and stabilization of reduced state

Abstract

The present study aims to probe the effect of silver nanoparticles (AgNPs) on the sorption behaviour of boroaluminosilicate glass (BASG). Firstly, BASG was loaded with AgNPs and benzotriazole (BT) and the glass exhibited surface-enhanced Raman spectrum of BT. The loaded BASG was equilibrated with copper (II) chloride solution and was investigated using ICP-AES, Raman spectroscopy, and luminescence measurements. It was observed that the glass matrix along with the sorbed copper ions showed luminescence, with a broad peak centered at ∼400nm, indicating the presence of copper ions in the Cu (I) state. However, in the absence of AgNPs, the glass matrix containing BT and sorbed copper ions failed to show luminescence implying that the copper ions are in the Cu (II) state. The glass matrix containing copper ions in addition to AgNPs and BT gave an enhanced Raman peak at 240 cm−1 (corresponding to Ag-Cl stretch with overlapping Ag-N stretch mode) and a shift of peak from 1022 (inplane trigonal ring breathing mode) to 1040 cm−1 and a broadening of the ring stretching modes at 1390 and 1575 cm−1. All these observations could be attributed to the interaction of copper ions with BT and the simultaneous uptake of chloride ions along with copper. The studies suggest that both AgNPs and copper ions bind to the nitrogen atoms of BT and form a nanoarray like assembly AgNPs-BT-Cu which facilitates the diffusion/tunnelling of electrons from AgNPs to Cu (II) ions resulting in the reduction of Cu (II) to Cu (I).