Label-free silicon quantum dots as fluorescent probe for selective and sensitive detection of copper ions

In this work, label-free silicon quantum dots (SiQDs) were used as a novel fluorescence probe for the sensitive and selective detection of Cu2+. The fluorescence of the SiQDs was effectively quenched by H2O2 from the reaction of ascorbic acid with O2, and hydroxyl radicals from Fenton reaction between H2O2 and Cu+. The fluorescence intensity of SiQDs was quenched about 25% in 15 min after the addition of H2O2 (1 mM). While the SiQDs was incubated with AA (1 mM) and Cu2+ (1 µM) under the same conditions, the fluorescence intensity of SiQDs decreased about 55%. Obviously, the recycling of Cu2+ in the test system may lead to a dramatical decrease in the fluorescence of SiQDs. Under the optimized experimental conditions, the rate of fluorescence quenching of SiQDs was linearly dependent on the Cu2+ concentration ranging from 25 to 600 nM with the limit of detection as low as 8 nM, which was much lower than that of existing methods. Moreover, the probe was successfully applied to the determination of Cu2+ in different environmental water samples and human hair.