Dual-emission ciprofloxacin-gold nanoclusters enable ratiometric sensing of Cu2+, Al3+, and Hg2.

Abstract

An innovative triple optical sensor is presentedthat utilizes gold nanoclusters (GNCs) stabilized with ciprofloxacin (CIP) and bovine serum albumin (BSA). The sensor is designed to identify three critical metal ions, namely Cu2+, Al3+, and Hg2+. Under 360nm excitation, the synthesized CIP-BSA-GNCs demonstrate dual fluorescence emission with peaks at 448nm (blue) and 612nm (red). The red emission is associated with the interior of the CIP-BSA-GNCs, whereas the blue emission results from the surface-bound CIP molecules. The sensitive and selective fluorescent nanosensor CIP-BSA-GNCs were employed to detect Cu2+, Al3+, and Hg2+ ions. Cu2+ effectively quenched the fluorescence intensity of the CIP-BSA-GNCs at both peaks via the internal charge transfer mechanism (ICT). Cu2+ could be detected within the concentration range 1.13 × 10-3 to 0.05µM, with a detection limit of 0.34nM. Al3+ increased the intensity of CIP fluorescence at 448nm via the chelation-induced fluorescence enhancement mechanism. The fluorescence intensity of the core CIP-BSA-GNCs at 612nm was utilized as a reference signal. Thus, the ratiometric detection of Al3+ succeeded with a limit of detection of 0.21nM within the dynamic range 0.69 × 10-3 to 0.07µM. Hg2+ effectively quenched the fluorescence intensity of the CIP-BSA-GNCs at 612nm via the metallophilic interaction mechanism. The fluorescence intensity of CIP molecules at 448nm was utilized as a reference signal. This allowed for the ratiometric detection of Hg2+ with a detection limit of 0.7nM within the concentration range 2.3 × 10-3 to 0.1µM.