Nearly monodisperse ZnS nanoparticles for portable recognition, enrichment and detection of Cd(II)

Abstract

As cadmium ions (Cd2+) pose a serious threat to environment and human health, it is significant to develop portable, fast-response and sensitive Cd2+ sensors for both real-time and on-site collection of such critical information. In this study, nearly monodisperse ZnS nanoparticles (NPs) were prepared and used to recognize, enrich and detect Cd2+ ions. ZnS NPs demonstrated fast adsorption kinetics towards Cd2+ ions (removing 99.3 % of Cd2+ in 12 min), surpassing previously reported multiple Cd2+ adsorption materials. Upon adsorbing Cu2+ and Cd2+ ions via substitution reaction, ZnS NPs gain strong peroxidase activity, and demonstrate the ability to selectively detect Cu2+ and Cd2+ ions among common metal ions. By further conjugating with our previous HSnS NFs (Hollow SnS nanoflower) nanosensor to eliminate the interference of Cu2+, the ZnS NPs nanosensor could selectively detect Cd2+ ions with recoveries above 80 %. The ZnS NPs nanosensor can cover a wide range of Cd2+ concentration from 0.5 to 100 μg L−1 with an extremely low detection limit of 0.38 μg L−1. When coupling to a portable RGB sensor, as low as 0.5 μg L−1 Cd2+ ions could be reached on-site for river water, giving an outstanding recovery of 99.4 %. The current results provide a new avenue to the on-site detection of Cd2+ ions, and would doubtlessly contribute to the future construction of portable and intelligent sensor arrays towards complex environmental samples.