A highly flexible and highly sensitive piezoresistive sensor was fabricated by using MXenes and polyvinyl butyral.

Two-dimensional (2D) material-controllable degradation under light radiation is crucial for their photonics and medical-related applications, which are yet to be investigated. In this paper, we first report the laser illumination method to regulate the degradation rate of Ti3C2Tx nanosheets in aqueous solution. Comprehensive characterization of intermediates and final products confirmed that plasmonic laser promoting the oxidation was strikingly different from heating the aqueous solution homogeneously. Laser illumination would nearly 10 times accelerate the degradation of Ti3C2Tx nanosheets in initial stage and create many smaller-sized oxidized products in a short time.Laser-induced fast degradation was principally ascribed to surface plasmonic resonance effect of Ti3C2Tx nanosheets.The degradation ability of such illumination could be controlled either by tuning the excitation wavelength or changing the excitation power. Furthermore, the laser-or thermal-induced degradation could be retarded by surface protection of Ti3C2Tx nanosheets. Our results suggest that plasmonic electron excitation of Ti3C2Tx nanosheets could build a new reaction channel and lead to the fast oxidation of nanosheets in aqueous solution, potentially enabling a series of waterbased applications.

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The development of flexible capacitive pressure sensors has wide application prospects in the fields of electronic skin and intelligent wearable electronic devices, but it is still a great challenge to fabricate capacitive sensors with high sensitivity. Few reports have considered the use of interdigital electrode structures to improve the sensitivity of capacitive pressure sensors. In this work, a new strategy for the fabrication of a high-performance capacitive flexible pressure sensor based on MXene/polyvinylpyrrolidone (PVP) by an interdigital electrode is reported. By increasing the number of interdigital electrodes and selecting the appropriate dielectric layer, the sensitivity of the capacitive sensor can be improved. The capacitive sensor based on MXene/PVP here has a high sensitivity (~1.25 kPa−1), low detection limit (~0.6 Pa), wide sensing range (up to 294 kPa), fast response and recovery times (~30/15 ms) and mechanical stability of 10000 cycles. The presented sensor here can be used for various pressure detection applications, such as finger pressing, wrist pulse measuring, breathing, swallowing and speech recognition. This work provides a new method of using interdigital electrodes to fabricate a highly sensitive capacitive sensor with very promising application prospects in flexible sensors and wearable electronics.

There are emerging applications for photothermal conversion utilizing MXene, but the mechanism under these applications related interfacial energy migration from MXene to the attached surface layer is still unknown. Here, the femtosecond pump–probe spectroscopy is employed to elucidate the ultrafast electronic energy dissipation pathways of MXene (Ti3C2T x ) under plasmonic excitation. The experimental results suggest that in water, nearly 80% energy in MXene gained from the photoexcitation quickly dissipates into surrounding water molecules within 7 ps as a hydrogen bond mediated fast channel, and the remaining energy vanishes with time constant ∼100 ps as a lattice motion mediated slow channel. This flash energy migration results in a prominent interfacial thermal conductance ∼162 MW·m–2·K–1 for the MXene–water interface. Tuning the solvent into ethanol could not only narrow the hydrogen bond mediated energy dissipation channel to 24% but also slow down the lattice motion mediated energy transport rate. Molecular dynamics simulation results further confirm that different solvents have significantly different hydrogen bond forming abilities on MXene surfaces. Our results suggest that the interfacial interaction is crucial for effective hydrogen bond formation on MXene surface to channel the excitation dissipation, providing important insights into the photothermal applications with MXene.