Label-free fluorescence “turn-on” detection of SO32− by gold nanoclusters: integration in a hydrogel platform and intracellular detection

A facile approach for the fluorescence based detection of sulfite (SO32−) using gold nanoclusters (Au NCs) has been reported. The detection assay relies on the effective quenching of the fluorescence of Au NCs in the presence of Cu2+, which could eventually be recovered upon the addition of SO32−. The proposed Cu2+ assisted fluorescence “turn-on” detection method for SO32− was highly sensitive and demonstrated a linear response towards SO32− within the desired concentration range. Importantly, the sensing system possessed high selectivity for SO32− compared to other competitive anionic analytes, allowing for an analytically robust and reliable detection. Further, fluorescent Au NC-hydrogels were developed, which present a way forward for solid sensing platforms for the detection of SO32− in aqueous solutions, making it a meaningful approach for instrument-free and visual monitoring. Owing to their excellent analytical characteristics, Au NCs were successfully employed for intracellular SO32− detection. Therefore, the present study encompasses the manifold detection aspects of Au NC based sensors.