Green synthesis of reduced Ti3C2Tx MXene nanosheets with enhanced conductivity, oxidation stability, and SERS activity†
Transition metal carbides (MXenes) are an emerging family of highly conductive two-dimensional materials with additional functional properties introduced by surface terminations. Further modification of the surface terminations makes MXenes even more appealing for practical applications. Herein, we report a facile and environmentally benign synthesis of reduced Ti3C2Tx MXene (r-Ti3C2Tx) via a simple treatment with L-ascorbic acid at room temperature. r-Ti3C2Tx shows a six-fold increase in electrical conductivity, from 471 ± 49 for regular Ti3C2Tx to 2819 ± 306 S m−1 for the reduced version. Additionally, we show an enhanced oxidation stability of r-Ti3C2Tx as compared to regular Ti3C2Tx. An examination of the surface-enhanced Raman scattering (SERS) activity reveals that the SERS enhancement factor of r-Ti3C2Tx is an order of magnitude higher than that of regular Ti3C2Tx. The improved SERS activity of r-Ti3C2Tx is attributed to the charge transfer interaction between the MXene surface and probe molecules, re-enforced by an increased electronic density of states (DOS) at the Fermi level of r-Ti3C2Tx. The findings of this study suggest that reduced MXene could be a superior choice over regular MXene, especially for the applications that employ high electronic conductivity, such as electrode materials for batteries and supercapacitors, photodetectors, and SERS-based sensors.