Sensitive signal-on fluorescent sensing for copper ions based on the polyethyleneimine-capped silver nanoclusters–cysteine system

• Polyethyleneimine-capped silver nanoclusters were label-free, cost-effective.
• This method for copper ions detection possesses a fluorescence signal-on response.
• This sensor for copper ions was selective, simple, and highly sensitive.

In this work, we present a label-free sensor for copper ions. This sensor is composed of silver nanoclusters and cysteine. The fluorescence of the silver nanoclusters was quenched by cysteine, which was recovered in the presence of copper ions. This binding of silver nanoclusters to cysteine promoted agglomeration of silver nanoclusters to yield larger non-fluorescent silver nanoparticles. The presence of copper ions resulted in the oxidation of cysteine to form a disulfide compound, leading to recovery of fluorescence of the silver nanoclusters. The fluorescence of the silver nanoclusters in the presence of cysteine increased with increasing concentration of copper ions in the range of 10–200 nM. The detection limit of this sensor for copper ions was 2.3 nM. The silver nanoclusters–cysteine sensor provides a simple, cost-effective, and sensitive platform for the detection of copper ions.

A signal-on method to monitor copper ions is proposed based on the suppression of cysteine-induced fluorescence quenching of silver nanoclusters by copper ions.Figure optionsDownload as PowerPoint slide