Homocytosine-templated gold nanoclusters as a label-free fluorescent probe: Ferrous ions and glucose detection based on Fenton and enzyme-Fenton reaction

Construction of facile fluorescent probe which own excellent sensing ability for targets is quite challenging. Herein, analytical performance of AuNCs@C20 probe integrated with Fenton and enzyme-Fenton reaction has been developed for ferrous ions (Fe 2+ ) and glucose sensing. Fluorescence of AuNCs@C20 is significantly quenched by ferric ions (Fe 3+ ) and hydroxyl radicals (·OH) which are generated from Fenton reaction between Fe 2+ and H 2 O 2 , and the above approach for turn-off fluorescence probing determination of Fe 2+ and H 2 O 2 is obtained. Glucose can be oxidized by Glucose oxidase (GOx) to generate H 2 O 2 , and then H 2 O 2 is immediately used as substrates for enzyme-Fenton reaction. AuNCs@C20 is further exploited for glucose sensing with satisfactory results. Attributing to the excellent fluorescence quenching efficiency of Fe 3+ and ·OH and the specific catalysis of GOx, this approach exhibits an extremely high sensitivity and selectivity. The limit of detection for Fe 2+ ion and glucose are 67.5 nmol/L and 2.3 μmol/L, respectively. Moreover, preliminary mechanistic investigation demonstrates that the fluorescence quench of AuNCs@C20 is highly related to the efficiency of Fe 3+ and ·OH production in Fenton reaction. Oligonucleotides served as a template in AuNCs@C20 is irreversibly cleaved by ·OH, and nanoclusters aggregate to form the non-fluorescent, larger-sized nanoparticles. This detection strategy provides the valuable insights in exploring nanoclusters based on Fenton or Fenton-like reactions for detecting diverse targets. An innovative strategy based on AuNCs@C20, Fenton and enzyme-Fenton reaction was presented for sensitivity and selectivity detection of Fe 2+ and glucose, and preliminary mechanism investigation was performed. • AuNCs@C20 were prepared by a facile one-step synthesized method. • AuNCs@C20 integrated with Fenton reaction was designed to detect Fe 2+ and glucose. • Possible detecting mechanism has been proposed.