Simple preparation and highly selective detection of silver ions using an electrochemical sensor based on sulfur-doped graphene and a 3,3′,5,5′-tetramethylbenzidine composite modified electrode

Abstract

A novel electrochemical sensor based on sulfur (S)-doped graphene (S-Gr) and a 3,3′,5,5′-tetramethylbenzidine (TMB) composite (S-Gr-TMB) modified glassy carbon (GCE) electrode for highly selective quantitative detection of silver ions (Ag⁺) were fabricated. The S-Gr-TMB composite was first prepared via electrostatic interaction between TMB and S-Gr and then, the composite was coated on the surface of GCE. The resultant S-Gr-TMB/GCE electrode showed a significant voltammetric response to Ag⁺ at 0.3 V vs. Ag/AgCl due to the synergistic effect of S-Gr and TMB. The sensor showed good linearity from 50 μM to 400 μM with a detection limit of 2.15 μM towards the determination of Ag⁺. In addition, after the addition of Fe³⁺ and other metal ions, including Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, K⁺, Mg²⁺, Na⁺, Ni²⁺, Pb²⁺ and Zn²⁺, in the same concentration, the current signal remained almost unchanged, revealing that the proposed electrochemical sensor exhibited a high selectivity for Ag⁺, which solves the nonselective problem of TMB as a spectral probe. This enhanced detection performance is attributed to two factors: (1) S-Gr has excellent electrical conductivity; (2) the coupling interactions between Ag–S are speculated to result in strengthened enrichment for Ag and good selective performance.