MXene/ZIF-67/PAN Nanofiber Film for Ultra-sensitive Pressure Sensors.

Flexible pressure sensors may be used in electronic skin (e-skin), artificial intelligence devices, and disease diagnosis, which require a large response range and high sensitivity. An appropriate design of the structure of the active layer can help effectively solve this problem. Herein, we aim at developing a wearable pressure sensor using the MXene/ZIF-67/polyacrylonitrile (PAN) nanofiber film, fabricated by electrospinning technology. Owing to the rough structure and three-dimensional network architecture, the MXene/ZIF-67/PAN film-based device displays a broad working range (0-100 kPa), good sensitivity (62.8 kPa-1), robust mechanical stability (over 10,000 cycles), and fast response/recovery time (10/8 ms). Moreover, the fabricated pressure sensors can be used to detect and differentiate between different body motion information, including elbow bending, finger movements, and wrist pulses. Overall, this design of a rough three-dimensional conductive network structure shows potential in the field of wearable electronics and medical devices.

Ti3 C2 Tx MXene Conductive Layers Supported Bio-Derived Fex -1 Sex /MXene/Carbonaceous Nanoribbons for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries.

Owing to their cost-effectiveness and high energy density, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are becoming the leading candidates for the next-generation energy-storage devices replacing lithium-ion batteries. In this work, a novel Fex -1 Sex heterostructure is prepared on fungus-derived carbon matrix encapsulated by 2D Ti3 C2 Tx MXene highly conductive layers, which exhibits high specific sodium ion (Na+ ) and potassium ion (K+ ) storage capacities of 610.9 and 449.3 mAh g-1 at a current density of 0.1 A g-1 , respectively, and excellent capacity retention at high charge-discharge rates. MXene acts as conductive layers to prevent the restacking and aggregation of Fex -1 Sex sheets on fungus-derived carbonaceous nanoribbons, while the natural fungus functions as natural nitrogen/carbon source to provide bionic nanofiber network structural skeleton, providing additional accessible pathways for the high-rate ion transport and satisfying surface-driven contribution ratios at high sweep rates for both Na/K ions storages. In addition, in situ synchrotron diffraction and ex situ X-ray photoelectron spectroscopy measurements are performed to reveal the mechanisms of storage and de-/alloying conversion process of Na+ in the Fex -1 Sex /MXene/carbonaceous nanoribbon heterostructure. As a result, the assembled Na/K full cells containing MXene-supported Fex -1 Sex @carbonaceous anodes possess stable large-ion storage capabilities.

Knitted Ti3C2Tx MXene based fiber strain sensor for human-computer interaction.

Fiber-based stretchable electronics with feasibility of weaving into textiles and advantages of light-weight, long-term stability, conformability and easy integration are highly desirable for wearable electronics to realize personalized medicine, artificial intelligence and human health monitoring. Herein, a fiber strain sensor is developed based on the Ti3C2Tx MXene wrapped by poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) polymer nanofibers prepared via electrostatic spinning. Owing to the good conductivity of Ti3C2Tx and unique 3D reticular structure with wave shape, the resistance of Ti3C2Tx@P(VDF-TrFE) polymer nanofibers changes under external force, thus providing remarkable strain inducted sensing performance. As-fabricated sensor exhibits high gauge factor (GF) of 108.8 in range of 45-66% strain, rapid response of 19 ms, and outstanding durability over 1600 stretching/releasing cycles. The strain sensor is able to monitor vigorous human motions (finger or wrist bending) and subtle physiological signals (blinking, pulse or voice recognition) in real-time. Moreover, a data glove is designed to connect different gestures and expressions to form an intelligent gesture-expression control system, further confirming the practicability of our Ti3C2Tx@P(VDF-TrFE) strain sensors in multifunctional wearable electronic devices.

Strongly Coupled 2D Transition Metal Chalcogenide-MXene-Carbonaceous Nanoribbon Heterostructures with Ultrafast Ion Transport for Boosting Sodium/Potassium Ions Storage.

HIGHLIGHTS: Unique "Janus" interfacial assemble strategy of 2D MXene nanosheets was proposed firstly. Ternary heterostructure consisting of high capacity transitional metal chalcogenide, high conductive 2D MXene and N rich fungal carbonaceous matrix was achieved for larger radius Na/K ions storages. The highly accessible surfaces and interfaces of the strongly coupled 2D based ternary heterostructures provide superb surficial pseudocapacitive storages for both Na and K ions with low energy barriers was verified. Combining with the advantages of two-dimensional (2D) nanomaterials, MXenes have shown great potential in next generation rechargeable batteries. Similar with other 2D materials, MXenes generally suffer severe self-agglomeration, low capacity, and unsatisfied durability, particularly for larger sodium/potassium ions, compromising their practical values. In this work, a novel ternary heterostructure self-assembled from transition metal selenides (MSe, M = Cu, Ni, and Co), MXene nanosheets and N-rich carbonaceous nanoribbons (CNRibs) with ultrafast ion transport properties is designed for sluggish sodium-ion (SIB) and potassium-ion (PIB) batteries. Benefiting from the diverse chemical characteristics, the positively charged MSe anchored onto the electronegative hydroxy (-OH) functionalized MXene surfaces through electrostatic adsorption, while the fungal-derived CNRibs bonded with the other side of MXene through amino bridging and hydrogen bonds. This unique MXene-based heterostructure prevents the restacking of 2D materials, increases the intrinsic conductivity, and most importantly, provides ultrafast interfacial ion transport pathways and extra surficial and interfacial storage sites, and thus, boosts the high-rate storage performances in SIB and PIB applications. Both the quantitatively kinetic analysis and the density functional theory (DFT) calculations revealed that the interfacial ion transport is several orders higher than that of the pristine MXenes, which delivered much enhanced Na+ (536.3 mAh g-1@ 0.1 A g-1) and K+ (305.6 mAh g-1@ 1.0 A g-1 ) storage capabilities and excellent long-term cycling stability. Therefore, this work provides new insights into 2D materials engineering and low-cost, but kinetically sluggish post-Li batteries.