Dual-modal light scattering and fluorometric detection of lead ion by stimuli-responsive aggregation of BSA-stabilized copper nanoclusters

Abstract

A new and facilely prepared light scattering (LS) and fluorometric dual-mode sensor is developed for lead ion (Pb²⁺) detection with high sensitivity and selectivity by use of bovine serum albumin stabilized copper nanoclusters (BSA–Cu NCs). This assay relied on changes in optical properties due to Pb²⁺-responsive state transformation from nanoclusters to nanoparticles. BSA protected Cu NCs exhibit strong fluorescence emission and the sensing mechanism is based on the Pb²⁺-responsive aggregation induced size change of BSA–Cu NCs and the fluorescence quenching of Cu NCs. While upon addition of Pb²⁺, the complexation between BSA and the lead ions would lead to the aggregation of BSA–Cu NCs which subsequently results in light scattering signal enhancement. The detection limit of Pb²⁺ can be as low as 1 nM. In addition, the Cu NCs show a dramatic fluorescence turn-off as a result of the Pb²⁺-responsive aggregation process from the complex attached Pb²⁺ to the BSA–Cu NCs, with a detection limit of 10 nM. Both the turn-on light scattering assay and the turn-off fluorometric assay of the dual-mode sensing system exhibit high selectivity toward Pb²⁺ over interfering substances. Furthermore, we demonstrate the application of the present approach in water samples, which suggests its potential applications such as environmental analysis in the future.