Sensitive and Selective Detection of Copper Ions with Highly Stable Polyethyleneimine-Protected Silver Nanoclusters

Abstract

Copper is a highly toxic environmental pollutant with bioaccumulative properties. Therefore, sensitive Cu²⁺ detection is very important to prevent over-ingestion, and visual detection using unaugmented vision is preferred for practical applications. In this study, hyperbranched polyethyleneimine-protected silver nanoclusters (hPEI-AgNCs) were successfully synthesized using a facile, one-pot reaction under mild conditions. The hPEI-AgNCs were very stable against extreme pH, ionic strength, temperature, and photoillumination and could act as sensitive and selective Cu²⁺ sensing nanoprobes in aqueous solutions with a 10 nM limit of detection. In addition, hPEI-AgNCs-doped agarose hydrogels were developed as an instrument-free and regenerable platform for visual Cu²⁺ and water quality monitoring.