Crumpled MXene nanosheets for sensing of ascorbic acid in food, biological fluids, and erythrocytes in-vitro microenvironment

In this work, a simple and facile method was developed to achieve controlled oxidation and enhance the surface area of MXene nanosheets and their utilization in the efficient sensing of ascorbic acid (AA or vitamin C). After etching of MAX phase to MXene via the MILD technique, controlled flash oxidation was carried out in the open air environment for 1.5 h, followed by flocculation of oxidized MXene nanosheets by using H2SO4, consequently achieving crumpled MXene possessing anatase phase, porosity, and improved surface area as revealed and confirmed by SEM, TEM, Raman, and BET analysis results. The as-prepared crumpled MXene was coated over a glassy carbon electrode (GCE) and used to determine AA successfully via cyclic voltammetry (CV), electro-chemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) with a linear concentration range of 300 & mu;M to 0.005 & mu;M with a detection limit (LOD) of 2 nM (2.8 % RSD and S/N = 3). The developed electrochemical sensor was used to determine the AA in various actual samples such as juice, urine, serum, and erythrocytes spiked with AA with excellent recoveries in the 94-103 % range. The sensor also demonstrated excellent reproducibility (-1 % RSD for five repetitive assays) and a shelf life of nearly one month with a negligible decrease in response. Furthermore, it lost only 10 % of its response for the next ten days. It also showed satisfactory selectivity toward AA in the presence of other similar compounds, including uric acid (UA), dopa -mine (DA), and glucose.

Automated summary

A simple and facile method was developed to achieve controlled oxidation and enhance the surface area of MXene nanosheets for the efficient sensing of ascorbic acid (AA). The crumpled MXene showed anatase phase, porosity, and improved surface area, and was successfully used to determine AA with a linear concentration range of 300 μM to 0.005 μM and a detection limit (LOD) of 2 nM. The developed electrochemical sensor exhibited excellent reproducibility, a long shelf life, and satisfactory selectivity.