Highly sensitive and selective colorimetric detection of iodide based on anti-aggregation of gold nanoparticles

Abstract

A simple and reliable colorimetric detection method for iodide has been well established based on the anti-aggregation effect of AuNPs in this paper. This assay is highly sensitive and selective toward iodide over other interferent anions due to the high stability of the inorganic complex formed between Hg²⁺ and iodide. In the absence of iodide, T-rich single-stranded DNA (ssDNA) can specifically bind with Hg²⁺ to form a stable T–Hg²⁺–T complex, inducing the solution color change from wine-red to finally violet blue with increasing concentration of Hg²⁺. However, when Hg²⁺ is first treated with iodide, the T–Hg²⁺–T interaction will be interrupted, which results in the anti-aggregation of AuNPs. A linear response from 4 × 10⁻⁸ to 4 × 10⁻⁶ M was obtained for iodide, and a detection limit of 13 nM was achieved.