Selective detection of mercury ions based on tin oxide quantum dots: performance and fluorescence enhancement model

Abstract

The superiority of fluorescence-based methods in the metal ion detection is well established; however, the quantum dot (QD) fluorescent probes currently used for mercury ions (Hg2+) have many limitations, such as a narrow detection range and environmental toxicity. In this work, environment-friendly tin oxide (SnO2) quantum dots were prepared and applied as a fluorescent sensor for the selective determination of Hg2+. The synthesized SnO2QDs showed excellent performance in Hg2+ion detection, with a broad linear range of 10−2-105μM and a low detection limit of 5 nM. Remarkably, SnO2QDs illustrated high selectivity to Hg2+ions without interference from other metal ions. Furthermore, the mechanism of fluorescence enhancement in SnO2QDs was based on the ratio of non-radiative electrons, and the density of active Sn vacancies was further explained. A mathematical model is proposed to interpret the mechanism of the adsorptive process during Hg2+detection, thereby providing a quantitative understanding of the fluorescence sensing principle of semiconductor QDs. This work demonstrates the promising application of SnO2QDs for convenient, highly sensitive and low-cost determination of Hg2+ions in experimental and actual conditions.