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.