Reusable thiophene-based fluorescent sensor for detection of toxic Au³ ⁺ in real samples: Integrated spectroscopic and computational insight

Gold exhibits fascinating photophysical and photochemical properties, making it valuable in various applications, including catalysis, fluorescent porous materials, fluorophores and medicine. However, high concentrations (0.075 and 0.006 mg/L) in fresh water are toxic, posing a threat to human health. Therefore, convenient chemical sensors are required for Au³⁺ monitoring. In this study, we present a novel carbazole-extended thiophene-containing electron rich organic compound (CT) and studied its interaction with Au³⁺ along with a range of sulphur containing small organic molecules through fluorescence, UV Vis. and NMR spectroscopy. Strong interaction between CT and Au³⁺ was further evaluated via SEM and DFT studies. Mechanism of interaction between CT and Au³⁺ was proposed to be chelation enhancement quenching effect (CHEQ) and the strong interaction explained based on the hard and soft acid and base (HSAB) theory. Interference studies showed highly selective interaction of CT with Au³⁺ in diverse conditions which makes CT a very promising fluorescent sensor. Therefore, real samples were also analyzed for the trace detection of Au³⁺ and ultra-fast, reversible and quantitative detection of Au³⁺ was achieved.