Stable Ag nanoclusters-based nano-sensors: Rapid sonochemical synthesis and detecting Pb²⁺ in living cells

The preparation and applications of fluorescent Ag nanoclusters (AgNCs) have been developed rapidly. However, the poor stability and time-consuming in synthesis process limit their further application. Herein, a rapid sonochemical route is used to synthesize fluorescent AgNCs using hydrazine hydrate as reducing agent and glutathione (GSH) as capping agent. The AgNCs would be formed quickly (∼15 min) due to presence of ultrasonic wave, which show red fluorescence (λ_em = 645 nm), small size (∼2 nm) and good dispersion in aqueous solution. Moreover, GSH, as protecting agent on the surface of resultant AgNCs, has many functional groups including carboxyl and amino groups which make NCs show high photo-, time-, metal- and pH-stability. Then a stable Ag nanoclusters-based nano-sensor is designed for highly sensitive and selective label-free detection of Pb²⁺. This nanosensor shows a potential application as probe for monitoring Pb²⁺ not only in aqueous solution but also in living cells. Thus, these stable and fluorescent AgNCs could work as an alternative to conventional fluorescence probes for biolabeling, sensing and other applications.