Colorimetric detection of arsenic and mercury ions based on the d-penicillamine induced aggregation of gold nanoparticles

Abstract

A simple and facile colorimetric method for the detection of arsenic ions (As3+) and mercury ions (Hg2+) using d-penicillamine coated silver nanoparticles (DPA-AuNPs) has been developed. As3+ and Hg2+ ions induced the aggregation of DPA-AuNPs in solution, resulting in a color change from red to blue, which was accompanied by the appearance of a new surface plasmon absorption band at 730 nm. The binding site and sensing mechanism for As3+ and Hg2+ ions in DPA-AuNPs were characterized by Fourier Transform infrared spectroscopy, ultraviolet-visible spectroscopy, and transmission electron microscopy. The aggregation of AuNPs in the presence of As3+ and Hg2+ ions was inhibited by d-penicillamine, which formed a shell on the surface of AuNPs. Furthermore, As3+ and Hg2+ ions coordinated with O？ on AuNPs through a binding structure, causing the aggregation and colorimetric response of AuNPs. The sensor conditions were optimized with 5 mM of d-penicillamine (DPA) and 20 nm AuNPs at pH 4.5 and 7. The absorption ratios (A730/A525) of the DPA-AuNPs solution exhibited a linear correlation with As3+ and Hg2+ ions concentration within the range of 0.0 ？ 2.0 × 10？3 mM. This sensitive and selective colorimetric assay opens up a fresh insight of development facile and fast detection methods for metal ions and biomolecules using the special catalytic reactivity of AuNPs.