CoMnO x Nanoflower-Based Smartphone Sensing Platform and Virtual Reality Display for Colorimetric Detection of Ziram and Cu 2 .

Transition metal doping is an ideal strategy to construct multifunctional and efficient nanozymes for biosensing. In this work, a metal-doped CoMnO _x nanozyme was designed and synthesized by hydrothermal reaction and high-temperature calcination. Based on its oxidase activity, an "on-off-on" smartphone sensing platform was established to detect ziram and Cu ²⁺ . The obtained flower-shaped CoMnO _x could exhibit oxidase-, catalase-, and laccase-like activities. The oxidase activity mechanism of CoMnO _x was deeply explored. O ₂ molecules adsorbed on the surface of CoMnO _x were activated to produce a large amount of O ₂ ^·- , and then, O ₂ ^·- could extract acidic hydrogen from TMB to produce blue oxTMB. Meanwhile, TMB was oxidized directly to the blue product oxTMB via the high redox ability of Co species. According to the excellent oxidase-like activity of CoMnO _x , a versatile colorimetric detection platform for ziram and Cu ²⁺ was successfully constructed. The linear detection ranges for ziram and Cu ²⁺ were 5~280 μM and 80~360 μM, and the detection limits were 1.475 μM and 3.906 μM, respectively. In addition, a portable smartphone platform for ziram and Cu ²⁺ sensing was established for instant analysis, showing great application promise in the detection of real samples including environmental soil and water.