Highly sensitive and selective determination of copper(II) based on a dual catalytic effect and by using silicon nanoparticles as a fluorescent probe

Abstract

The authors describe a silicon nanoparticle-based fluorometric method for sensitive and selective detection of Cu²⁺. It is based on the catalytic action of Cu²⁺ on the oxidation of cysteine (Cys) by oxygen to form cystine and the by-product H₂O₂. The generated H₂O₂ is catalytically decomposed by Cu²⁺ to generate hydroxyl radicals which oxidize and destroy the surface of SiNPs. As a result, the blue fluorescence of the SiNPs is quenched. The method has excellent selectivity due to the dual catalytic effects of Cu²⁺, which is much better than most previously reported nanomaterial-based assays for Cu²⁺. Under the optimal conditions, the method has low detection limit (29 nM) and a linear response in a concentration range from 0.05 μM to 15 μM. The method has been successfully applied to the determination of Cu²⁺ in spiked real water samples, and the results agreed well with those obtained by the Chinese National Standard method (GB/T 7475-1987; AAS). Graphical abstract Schematic presentation of a fluorometric method for the determination of Cu²⁺ based on the dual catalytic effects of Cu²⁺, and the oxidative effect of hydroxy radicals on the surface of silicon nanoparticles (SiNPs). The method has a 29 nM detection limit and good selectivity.

Keywords: Copper ions; Cysteine; Cystine; Dual catalytic effects; Fluorometry; Hydroxyl radicals; Quenching; Stern-Volmer plot.