Vertically Oriented Assembly of a Few-Layer Ti₃C₂T_x Grid by Electric Field Inducing and Freeze Drying for Wearable...

Compared with the parallel assembly, the vertical assembly of MXene nanosheets on the substrate exhibits open three-dimensional porous structure, which is beneficial to the construction of high-performance electrodes. Herein, the vertically oriented assembly of Ti₃C₂T_x nanosheets is proposed by a novel preparation process of electric field inducing and freeze drying, resulting in the Ti₃C₂T_x grid with thin-wall and open porous structure. First, the electric field induces the formation of Ti₃C₂T_x hydrogel layer on the substrate. Second, freeze drying causes the growth of ice crystals for squeezing few-layer Ti₃C₂T_x nanosheets to stand up. More importantly, such a Ti₃C₂T_x grid with large surface area and intrinsic conductivity can effectively load electrocatalysts, resulting in the Au-Ti₃C₂T_x grid as a high-performance working electrode for the electrochemical detection of levodopa. The main parameters include 1-30 μM and 30-160 μM two-stage linear ranges and 37 nM detection limit. The structural advantages of Ti₃C₂T_x grid-based electrode materials are their three-dimensional conductive network and interconnected porous structure, which contribute to the penetration of the electrolyte, the diffusion of the analyte, and the electrocatalytic reaction. Furthermore, the self-adapting shape of the Ti₃C₂T_x grid leads to the fan-shaped Au-Ti₃C₂T_x grid collaborated with a self-designed leaf-like microfluidic. Ultimately, a wearable levodopa sensor composed of Au-Ti₃C₂T_x grid, microfluidic, flexible electronic system, and mobile phone client is established for detecting levodopa in human sweat, which is expected to help Parkinson's patients control the drug dosage. Our work proposes the vertically assembled Ti₃C₂T_x nanosheet loaded noble metal electrocatalysts to develop high-performance electrodes for electrochemical sensing.