Search Results (13)

MXenes, as emerging 2D sensing materials for next-generation electronics, have attracted tremendous attention owing to their extraordinary electrical conductivity, mechanical strength, and flexibility. However, challenges remain due to the weak stability in the oxygen environment and nonnegligible aggregation of layered MXenes, which severely affect the durability and sensing performances of the corresponding MXene-based pressure sensors, respectively. Here, in this work, we propose an easy-to-fabricate self-assembly strategy to prepare multilayered MXene composite films, where the first layer MXene is hydrogen-bond self-assembled on the electrospun thermoplastic urethane (TPU) fibers surface and the anti-oxidized functionalized-MXene (f-MXene) is subsequently adhered on the MXene layer by spontaneous electrostatic attraction. Remarkably, the f-MXene surface is functionalized with silanization reagents to form a hydrophobic protective layer, thus preventing the oxidation of the MXene-based pressure sensor during service. Simultaneously, the electrostatic self-assembled MXene and f-MXene successfully avoid the invalid stacking of MXene, leading to an improved pressure sensitivity. Moreover, the adopted electrospinning method can facilitate cyclic self-assembly and the formation of a hierarchical micro-nano porous structure of the multilayered f-MXene/MXene/TPU (M-fM²T) composite. The gradient pores can generate changes in the conductive pathways within a wide loading range, broadening the pressure detection range of the as-proposed multilayered f-MXene/MXene/TPU piezoresistive sensor (M-fM²TPS). Experimentally, these novel features endow our M-fM²TPS with an outstanding maximum sensitivity of 40.31 kPa⁻¹ and an extensive sensing range of up to 120 kPa. Additionally, our M-fM²TPS exhibits excellent anti-oxidized properties for environmental stability and mechanical reliability for long-term use, which shows only ~0.8% fractional resistance changes after being placed in a natural environment for over 30 days and provides a reproducible loading–unloading pressure measurement for more than 1000 cycles. As a proof of concept, the M-fM²TPS is deployed to monitor human movements and radial artery pulse. Our anti-oxidized self-assembly strategy of multilayered MXene is expected to guide the future investigation of MXene-based advanced sensors with commercial values. Full article

In this study, waterborne polyurethane acrylate (WPUA)/MXene nanocomposite films with varying MXene loadings were fabricated using UV-curing technology, where MXene (Ti₃C₂T_x) was employed as a nanofiller. The microstructure and chemical structure of the WPUA/MXene nanocomposite films were examined by XRD and FTIR, respectively. The water contact angle testing demonstrated that the incorporation of MXene into the nanocomposite films led to an increase in their hydrophilic properties. The tensile strength, the elongation at break, and Young’s modulus of the WPUA/MXene nanocomposite coatings exhibited an initial increase followed by a decrease with increasing MXene loadings. Compared to the pure WPUA film, the tensile strength and elongation at break of nanocomposites with 0.077 wt% MXene loading reached their maximum values, which increased by 39.9% and 38.5%, respectively. Furthermore, the glass transition temperature and the thermal stability were both enhanced by MXene to some extent. This study introduces a novel method for utilizing MXene in UV-curable waterborne coatings. Full article

MXene materials have the metallic conductivity of transition metal carbides. Among them, Ti₃C₂T_X with an accordion structure has great application prospects in the field of wearable devices. However, flexible wearable electronic devices face the problem of single function in practical application. Therefore, it is particularly important to study a flexible sensor with multiple functions for electronic skin. In this work, the near-field electrohydrodynamic printing (NFEP) method was proposed to prepare the composite thin film with a micro/nanofiber structure on the flexible substrate using a solution of poly(vinylidene fluoride)/MXene nanosheet/reduced graphene oxide (PMR) nanocomposites as the printing solution. A dual-mode flexible sensor for electronic skin based on the PMR nanocomposite thin film was fabricated. The flexible sensor had the detection capability of the piezoresistive mode and the piezoelectric mode. In the piezoresistive mode, the sensitivity was 29.27 kPa⁻¹ and the response/recovery time was 36/55 ms. In the piezoelectric mode, the sensitivity was 8.84 kPa⁻¹ and the response time was 18.2 ms. Under the synergy of the dual modes, functions that cannot be achieved by a single mode sensor can be accomplished. In the process of detecting the pressure or deformation of the object, more information is obtained, which broadens the application range of the flexible sensor. The experimental results show that the dual-mode flexible sensor has great potential in human motion monitoring and wearable electronic device applications. Full article

The traditional self-supported piezoelectric thin films prepared by filtration methods are limited in practical applications due to their poor tensile properties. The strategy of using flexible polyethylene terephthalate (PET) fabric as the flexible substrate is beneficial to enhancing the flexibility and stretchability of the flexible device, thus extending the applications of pressure sensors. In this work, a novel wearable pressure sensor is prepared, of which uniform and dense ZnO nanoarray-coated PET fabrics are covered by a two-dimensional MXene nanosheet. The ternary structure incorporates the advantages of the three components including the superior piezoelectric properties of ZnO nanorod arrays, the excellent flexibility of the PET substrate, and the outstanding conductivity of MXene, resulting in a novel wearable sensor with excellent pressure-sensitive properties. The PET/ZnO@MXene pressure sensor exhibits excellent sensing performance (S = 53.22 kPa⁻¹), fast response/recovery speeds (150 ms and 100 ms), and superior flexural stability (over 30 cycles at 5% strain). The composite fabric also shows high sensitivity in both motion monitoring and physiological signal detection (e.g., device bending, elbow bending, finger bending, wrist pulse peaks, and sound signal discrimination). These findings provide insight into composite fabric-based pressure-sensitive materials, demonstrating the great significance and promising prospects in the field of flexible pressure sensing. Full article

The flexible self-powered display system integrating a flexible triboelectric nanogenerator (TENG) and flexible alternating current electroluminescence (ACEL) has attracted increasing attention for its promising potential in human–machine interaction applications. In this work, a performance-enhanced MXene/cellulose nanofibril (CNF)/MXene-based TENG (MCM-TENG) is reported for powering a flexible patterned ACEL device in order to realize self-powered display. The MCM multilayer composite film was self-assembled through the layer-by-layer method. The MCM film concurrently acted as a triboelectric layer and electrode layer due to its high conductivity and strength. Moreover, the effect of CNF concentration and number of layers on the output performance of TENG was investigated. It was found that the MCM-TENG realized the optimum output performance. Finally, a flexible self-powered display device was realized by integrating the flexible TENG and ACEL. The MCM-TENG with an output voltage of ≈90 V at a frequency of 2 Hz was found to be efficient enough to power the ACEL device. Therefore, the as-fabricated flexible TENG demonstrates a promising potential in terms of self-powered displays and human–machine interaction. Full article

Here, rational design electrodes are fabricated by mixing MXene with an aqueous solution of chloroauric acid (HAuCl₄). In order to prevent MXene from self-restacking, the groups of -OH on the surface of Ti₃C₂T_x nanosheets underwent a one-step simultaneous self-reduction from AuCl₄-, generating spaces for rapid ion transit. Additionally, by using this procedure, MXene’s surface oxidation can be decreased while preserving its physio-chemical properties. The interlayered MX/Au NPs that have been obtained are combined into a conducting network structure that offers more active electrochemical sites and improved mass transfer at the electrode–electrolyte interface, both of which promote quick electron transfer during electrochemical reactions and excellent structural durability. The Ti₃C₂T_x-AuNPs film thus demonstrated a rate performance that was preferable to that of pure Ti₃C₂T_x film. According to the results of the characterization, the AuNPs effectively adorn the MXene nanosheets. Due to the renowned pseudocapacitance charge storage mechanism, MXene-based electrode materials also work well as supercapacitors in sulfuric acid, which is why MXene AuNPs electrodes have been tested in 3 M and 1 M H₂SO₄. The symmetric supercapacitors made of MXene and AuNPs have shown exceptional specific capacitance of 696.67 Fg⁻¹ at 5 mVs⁻¹ in 3 M H₂SO₄ electrolyte, and they can sustain 90% of their original capacitance for 5000 cycles. The highest energy and power density of this device, which operates within a 1.2 V potential window, are 138.4 Wh kg⁻¹ and 2076 W kg⁻¹, respectively. These findings offer a productive method for creating high-performance metal oxide-based symmetric capacitors and a straightforward, workable approach for improving MXene-based electrode designs, which can be applied to other electro-chemical systems that are ion transport-restricted, such as metal ion batteries and catalysis. Full article

Two-dimensional MXenes possessed exceptional physiochemical properties such as high electrical conductivity (20,000 Scm⁻¹), flexibility, mechanical strength (570 MPa), and hydrophilic surface functionalities that have been widely explored for energy storage, sensing, and catalysis applications. Recently, the fabrication of MXenes thin films has attracted significant attention toward electronic devices and sensor applications. This review summarizes the exciting features of MXene thin film fabrication methods such as vacuum-assisted filtration (VAF), electrodeposition techniques, spin coating, spray coating, dip-coating methods, and other physical/chemical vapor deposition methods. Furthermore, a comparison between different methods available for synthesizing a variety of MXenes films was discussed in detail. This review further summarizes fundamental aspects and advances of MXenes thin films in solar cells, batteries, electromagnetic interference shielding, sensing, etc., to date. Finally, the challenges and opportunities in terms of future research, development, and applications of MXenes-based films are discussed. A comprehensive understanding of these competitive features and challenges shall provide guidelines and inspiration for further growth in MXenes-based functional thin films and contribute to the advances in MXenes technology. Full article

This paper provides an overview of the application of conducting polymers (CPs) used in the design of tactile sensors. While conducting polymers can be used as a base in a variety of forms, such as films, particles, matrices, and fillers, the CPs generally remain the same. This paper, first, discusses the chemical and physical properties of conducting polymers. Next, it discusses how these polymers might be involved in the conversion of mechanical effects (such as pressure, force, tension, mass, displacement, deformation, torque, crack, creep, and others) into a change in electrical resistance through a charge transfer mechanism for tactile sensing. Polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), polydimethylsiloxane, and polyacetylene, as well as application examples of conducting polymers in tactile sensors, are overviewed. Attention is paid to the additives used in tactile sensor development, together with conducting polymers. There is a long list of additives and composites, used for different purposes, namely: cotton, polyurethane, PDMS, fabric, Ecoflex, Velostat, MXenes, and different forms of carbon such as graphene, MWCNT, etc. Some design aspects of the tactile sensor are highlighted. The charge transfer and operation principles of tactile sensors are discussed. Finally, some methods which have been applied for the design of sensors based on conductive polymers, are reviewed and discussed. Full article

Glucose is one of the most important monosaccharides found in the food, as a part of more complex structures, which is a primary energy source for the brain and body. Thus, the monitoring of glucose concentration is more important in food and biological samples in order to maintain a healthy lifestyle. Herein, an electrochemical glucose biosensor was fabricated by immobilization of glucose oxidase (GOX) onto poly(3,4-ethylenedioxythiophene):4-sulfocalix [4]arene (PEDOT:SCX)/MXene modified electrode. For this purpose, firstly, PEDOT was synthesized in the presence of SCX (counterion) by the chemical oxidative method. Secondly, MXene (a 2D layered material) was synthesized by using a high-temperature furnace under a nitrogen atmosphere. After that, PEDOT:SCX/MXene (1:1) dispersion was prepared by ultrasonication which was later utilized to prepare PEDOT:SCX/MXene hybrid film. A successful formation of PEDOT:SCX/MXene film was confirmed by HR-SEM, Fourier transform infrared (FT-IR), and Raman spectroscopies. Due to the biocompatibility nature, successful immobilization of GOX was carried out onto chitosan modified PEDOT:SCX/MXene/GCE. Moreover, the electrochemical properties of PEDOT:SCX/MXene/GOX/GCE was studied through cyclic voltammetry and amperometry methods. Interestingly, a stable redox peak of FAD-GOX was observed at a formal potential of –0.435 V on PEDOT:SCX/MXene/GOX/GCE which indicated a direct electron transfer between the enzyme and the electrode surface. PEDOT:SCX/MXene/GOX/GCE also exhibited a linear response against glucose concentrations in the linear range from 0.5 to 8 mM. The effect of pH, sensors reproducibility, and repeatability of the PEDOT:SCX/MXene/GOX/GCE sensor were studied. Finally, this new biosensor was successfully applied to detect glucose in commercial fruit juice sample with satisfactory recovery. Full article

Electrochromic materials and devices are attracting intense attention because of their low energy consumption and open-circuit memory effect. Considering the difficult processing characteristics of electrochromic conductive polymers, we developed a facile and scalable strategy to prepare solution processable polyaniline (PANI)-based nanocomposites by introducing two-dimensional titanium carbon nanosheets (MXene) through a self-assembly approach. The PANI/MXene nanocomposite can be fabricated into porous films via spray-coating process, which show an obvious synergetic effect of both materials, leading to superior electrochromic properties. The optical contrast of the optimized PANI/MXene film reached as high as 55% at =700 nm, and its response times were 1.3 s for coloration and 2.0 s for bleaching, respectively. In addition, the composite film also showed excellent cycle stability (after 500 cycles, the ΔT retention was above 87%). The improved electrochromic properties are owed to the high conductivity of MXene and the formation of the porous composite film structure, which promote the electronic/ionic transfer and migration efficiency. This research suggests that the self-assembly method and the conductive polymer/MXene nanocomposites have a potential application in the fields of electronic functional films and devices. Full article

Inks printing is an innovative and practicable technology capable of fabricating the next generation of flexible functional systems with various designs and desired architectures. As a result, inks printing is extremely attractive in the development of printed wearables, including wearable sensors, micro supercapacitor (MSC) electrodes, electromagnetic shielding, and thin-film batteries. The discovery of Ti₃C₂T_x in 2011, a 2D material known as a MXene, which is a compound composed of layered nitrides, carbides, or carbonitrides of transition metals, has attracted significant interest within the research community because of its exceptional physical and chemical properties. MXene has high metallic conductivity of transition metal carbides combined with hydrophilic behavior due to its surface terminated functional groups, all of which make it an excellent candidate for promising inks printing applications. This paper reviews recent progress in the development of 2D MXene inks, including synthesis procedures, inks formulation and performance, and printing methods. Further, the review briefly provides an overview of future guidelines for the study of this new generation of 2D materials. Full article

Molybdenum carbide (Mo₂C) is a two-dimensional (2D) MXene material which makes it a promising photoelectric material. In this study, reflective type MXene Mo₂C thin films were coated on a silver mirror by a magnetron sputtering method and were subsequently used in a passively Q-switched solid-state pulsed laser generator at the central wavelengths of 1.06 and 1.34 μm, respectively. The fabricated thin films of reflective type MXene Mo₂C exhibited large modulation depth of 6.86% and 5.38% at the central wavelengths of 1064 and 1342 nm, respectively. By inserting the Mo₂C saturable absorbers (SAs) into V-shaped Nd:YAG laser, short pulses were generated having a pulse duration, pulse energy, and average output power of 254 ns, 2.96 μJ, and 275 mW, respectively, at a wavelength of 1.06 μm. Similarly, shorter laser pulses were obtained in Nd:YVO₄ laser at 1.34 μm. Our results illustrated potential of the 2D MXene Mo₂C films for laser applications. Full article

The monotonic work function of graphene makes it difficult to meet the electrode requirements of every device with different band structures. Two-dimensional (2D) transition metal carbides (TMCs), such as carbides in MXene, are considered good candidates for electrodes as a complement to graphene. Carbides in MXene have been used to make electrodes for use in devices such as lithium batteries. However, the small lateral size and thermal instability of carbides in MXene, synthesized by the chemically etching method, limit its application in optoelectronic devices. The chemical vapor deposition (CVD) method provides a new way to obtain high-quality ultrathin TMCs without functional groups. However, the TMCs film prepared by the CVD method tends to grow vertically during the growth process, which is disadvantageous for its application in the transparent electrode. Herein, we prepared an ultrathin Mo₂C—graphene (Mo₂C—Gr) hybrid film by CVD to solve the above problem. The work function of Mo₂C—Gr is between that of graphene and a pure Mo₂C film. The Mo₂C—Gr hybrid film was selected as a transparent hole-transporting layer to fabricate novel Mo₂C—Gr/Sb₂S_0.42Se_2.58/TiO₂ two-sided photodetectors. The Mo₂C—Gr/Sb₂S_0.42Se_2.58/TiO₂/fluorine-doped tin oxide (FTO) device could detect light from both the FTO side and the Mo₂C—Gr side. The device could realize a short response time (0.084 ms) and recovery time (0.100 ms). This work is believed to provide a powerful method for preparing Mo₂C—graphene hybrid films and reveals its potential applications in optoelectronic devices. Full article