A Highly Sensitive Dual-Signal Strategy via Inner Filter Effect between Tween 20-Gold Nanoparticles and CdSe/ZnS Quantum Dots for Detecting Cu(2+)

A highly sensitive and accurate dual-signal strategy is developed for trace Cu(2+) detection based on the inner filter effect (IFE) between Tween 20-gold nanoparticles (AuNPs) and CdSe/ZnS quantum dots (QDs). Tween 20-AuNPs are utilized as colorimetric probes and excellent fluorescent absorbers. The fluorescence of CdSe/ZnS QDs can be quenched efficiently by Tween 20-AuNPs via IFE. In the presence of D-penicillamine, D-penicillamine induces the aggregation of Tween 20-AuNPs and the fluorescent recovery of CdSe/ZnS QDs at high ionic strength. Upon addition of Cu(2+), D-penicillamine tends to selectively chelate with Cu(2+) and then forms the mixed-valence complexes, which consequently inhibits the aggregation of Tween 20-AuNPs and the fluorescent recovery. The dual-signal method is used to quantitatively detect trace Cu(2+), with low detection limits of 0.57 μg/L and 0.36 μg/L for colorimetry and fluorescence, respectively. In addition, the proposed method using a portable spectrometer is applied to the detection of Cu(2+) in water. This sensitive, accurate and miniature sensing system has potential in environmental evaluations.