Inositol directed facile “green” synthesis of fluorescent gold nanoclusters as selective and sensitive detecting probes of ferric ions

In this paper, we developed one-pot facile synthetic approach for preparing fluorescent gold nanoclusters (AuNCs) by utilizing reducing-cum-stabilizing inositol (INOS). The as-prepared INOS protected gold nanoclusters (INOS@AuNCs) have excellent monodispersity with uniform size <2.0 nm and exhibit strong inherent fluorescence at 470 nm with a decay time of 12.01 ns. Interestingly, ferric ions (Fe³⁺) can significantly quench the fluorescence of the synthesized INOS@AuNCs leading to the efficient Fe³⁺ sensing. On the basis of results obtained from high-resolution transmission electron microscopy (HRTEM), an aggregation-induced fluorescence quenching mechanism was proposed. Based on these fascinating findings, a facile, fast, “green” and highly sensitive AuNCs-dependant fluorescent sensor probe was developed to detect Fe³⁺ ions in water resources and Over-The-Counter (OTC) medicines. Stern-Volmer plot showed a good linear calibration curve for Fe³⁺ assay in the range of 1.0–1000 μM (R² = 0.996) and good precision response to 100.0 μM Fe³⁺ with RSD of 2.94% (n = 3) was also achieved. The obtained limit of detection of 0.54 μM for the determination of Fe³⁺ ions is 10 times lower than the limit value (≈5.5 μM) allowed by the U.S. Environmental Protection Agency in drinkable water, indicating the sensitivity of the fluorescent probe of Fe³⁺ sensing. The excellent selectivity obtained among 16 types of metal ions underpins INOS@AuNCs as a promising sensor for real time detection of Fe³⁺ in environmental water samples and pharmaceutical tablets.