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

Abstract

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.