Highly selective colorimetric detection of Zn(II) ions using label-free silver nanoparticles

•A facile silver nanoparticle sensor for the visual detection of Zn2+ ion.•A colorimetric Zn2+ ion sensor using label-free silver nanoparticle.•This sensor exhibits excellent selectivity for Zn2+ ion over other metal ions.•This simple sensor can detect ∼0.36 × 10−6 mol L−1 concentration of Zn2+ ion within 15 min.

A simple and facile colorimetric method for the detection of zinc ions (Zn2+) using label-free silver nanoparticles (AgNPs) has been developed. Zn2+ ions induced the aggregation of label-free AgNPs in solution, resulting in a color change from yellow to forest green, which was accompanied by the appearance of a new surface plasmon absorption band at 635 nm. The sensitivity of label-free AgNPs towards other metal ions was negligible, with the exception of Fe3+, which caused a modest interference. The binding site and sensing mechanism for Zn2+ ions in label-free AgNPs were characterized by Fourier Transform infrared spectroscopy, ultraviolet-visible spectroscopy, and transmission electron microscopy. The aggregation of AgNPs in the presence of Zn2+ ions was inhibited by polyvinyl alcohol, which formed a shell on the surface of AgNPs. Furthermore, Zn2+ ions coordinated with BH4− on AgNPs through a triangular sixdentate binding structure, thus inducing aggregation of AgNPs in solution.The sensor conditions were optimized with 6.0 μM of sodium dodecylbenzenesulfonate (NaDDBS) and 0.23 mM AgNPs at pH 6. The absorption ratios (A635/A390) of the label-free AgNPs solution exhibited a linear correlation with Zn2+ ion concentration within the range of 0.0 − 7.6 × 10−6 mol L−1, with a limit of detection of 0.36 × 10−6 mol L−1. This cost-effective sensing system allows rapid and facile determination of Zn2+ ions in various types of biological, mineral supplement, and environmental samples.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide