Ultrasound-electrochemistry assisted liquid-phase co-exfoliation of phosphorene decorated by Au−Ag bimetallic nanoparticles as nanozyme for smartphone-based portable sensing of 4-nitrophenol.

The stability of black phosphorene (BP) and its preparation and modification for developing and applying devices have become a hot topic in the interdisciplinary field. We propose ultrasound-electrochemistry co-assisted liquid-phase exfoliation as an eco-friendly one-step method to prepare gold–silver bimetallic nanoparticles (Au−AgNPs)-decorated BP nanozyme for smartphone-based portable sensing of 4-nitrophenol (4-NP) in different water sources. The structure, morphology, composition, and properties of Au−AgNPs−BP nanozyme are characterized by multiple instrumental analyses. Bimetallic salts are induced to efficiently occupy oxidative sites of BP to form highly stable Au−AgNPs−BP nanozyme and guarantee the integrity of the lamellar BP. The electrochemistry shortens the exfoliation time of the BP nanosheet and contributes to the loading efficiency of bimetallic nanoparticles on the BP nanosheet. Au−AgNPs−BP-modified screen-printed carbon electrode coupled with palm-sized smartphone-controlled wireless electrochemical analyzer as a portable wireless intelligent sensing platform was applied to the determination of 4-NP in a linear range of 0.6−10 μM with a limit of detection of 63 nM. It enables on-site determination of 4-NP content in lake water, river water, and irrigation ditch water. This work will provide a reference for an eco-friendly one-step preparation of bimetallic nanoparticle-decorated graphene-like materials as nanozymes and their smartphone-based portable sensing application outdoors. [ABSTRACT FROM AUTHOR]