In2O3 nanocubes/Ti3C2Tx MXene composites for enhanced methanol gas sensing properties at room temperature

Highly active two-dimensional (2D) nanocomposites, integrating the unique merits of individual components and synergistic effects of composites, have been recently receiving attention for gas sensing. In this work, In₂O₃ nanocubes/Ti₃C₂T_x MXene nanocomposites were synthesized using In₂O₃ nanocubes and layered Ti₃C₂T_x MXene via a facile hydrothermal self-assembly method. Characterization results indicated that the In₂O₃ nanocubes with sizes approximately 20–130 nm in width were well dispersed on the surface of layered Ti₃C₂T_x MXene to form numerous heterostructure interfaces. Based on the synergistic effects of electronic properties and gas-adsorption capabilities, In₂O₃ nanocubes/Ti₃C₂Tx MXene nanocomposites exhibited high response (29.6%–5 ppm) and prominent selectivity to methanol at room temperature. Meanwhile, the low detection concentration could be reduced to ppm-level, the response/recovery times are shortened to 6.5/3.5 s, excellent linearity and outstanding repeatability. The strategy of compositing layered MXene with metal oxide semiconductor provides a novel pathway for the future development of room temperature gas sensors.     

Synthesis,characterization and antifungal property of Ti3C2Tx MXene nanosheets

Although the antibacterial properties of MXene nanosheets containing Ti₃C₂T_x are known, their antifungal properties have not been well studied. Herein, we present for the first time a report on the antifungal properties of Ti₃C₂T_x MXene. The Ti₃C₂T_x MXene was obtained by first exfoliating MAX phase of Ti₃AlC₂ with concentrated hydrofluoric acid, then the Ti₃C₂T_x was intercalated and deliminated by ethanol treatment and ultrasonication process. The delaminated Ti₃C₂T_x MXene nanosheets (d-Ti₃C₂Tx) were characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), X-ray diffraction spectroscopy (XRD), and Raman spectroscopy. It was found that Ti₃C₂T_x MXene was characterized by lamellar structure alternating with layers of Ti, Al and C. The EDX results revealed that the delaminated Ti₃C₂T_x MXene nanosheets were composed of Ti, C, Si, O, F, and a trace amount of Al. The XRD and Raman spectra further indicated the elimination of Al and the formation of two-dimensional Ti₃C₂T_x MXene nanosheets. The antifungal activity of the delaminated Ti₃C₂T_x MXene was determined against Trichoderma reesei using the modified agar disc method. Observation using inverted phase contrastmicroscopy revealed inhibited fungus growth with the absence of hyphae around the discs treated wtih MXene. The surrounding of the control groups without an inclusion of MXene was found with large number of hyphae and spores. In addition, the spores of the fungi treated with the samples containing d-Ti₃C₂T_x MXene nanosheets did not germinate even after 11 days of culture. The results demonstrated disruption to the hemispheric structural formation of fungi colony, inhibition of hyphae growth and cell damage for fungi grown on the d-Ti₃C₂T_x MXene nanosheets. These new findings suggest that d-Ti₃C₂T_x MXene nanosheets developed in this work could be a promising anti-fungi material.     

Broadband electromagnetic absorption of Ti3C2Tx MXene/WS2 composite via constructing two-dimensional heterostructure

Ti₃C₂T_x MXene, an emerging two-dimensional (2D) ceramic material, has rich interfaces and strong conductive networks. Herein, we have successfully built a heterostructure between Ti₃C₂T_x MXene and WS₂ to improve electromagnetic absorption performance. X-ray diffraction and X-ray photoelectron spectroscopy were used to determine the successful synthesis of Ti₃C₂T_x/WS₂ composite. Field emission scanning electron microscopy and transmission electron microscopy images show that WS₂ nanosheets are evenly dispersed on the accordion-like Ti₃C₂T_x MXene. Importantly, Ti₃C₂T_x MXene/WS₂ composite has sufficiently high dielectric loss and impedance matching due to self-adjusting conductivity and 2D heterostructure interfaces. As a result, the Ti₃C₂T_x/WS₂ composite has a minimum reflection loss (RL_min) of −61.06 dB at 13.28 GHz. Besides, it has a broad effective absorption bandwidth (EAB) of 6.5 GHz, with EAB >5.0 GHz covering a wide range of thickness. Such impressive results may provide experience for the application of Ti₃C₂T_x ceramics and 2D materials.     

Tuning the photoluminescence of large Ti3C2Tx MXene flakes

Ti₃C₂T_x MXene has been reported to be a metallic two-dimensional (2D) material with high conductivity, whereas its photoluminescence (PL) mechanism is still under debate. Herein, we demonstrate that large Ti₃C₂T_x MXene flakes exhibit tunable PL under ambient conditions. The as-prepared Ti₃C₂T_x MXene flakes emit blue, yellow-green and red light under different excitation wavelengths. Their PL emission wavelengths redshift as the excitation wavelength changes from violet to red light. Surface modification of the MXenes can further tune the PL peak wavelength into the near infrared region. Using density function theory (DFT) calculations, this excitation wavelength-dependent PL can be correlated to TiO₂ defects that exist on the surface of Ti₃C₂T_x. Our study expounds on the optical properties of Ti₃C₂T_x MXene and is helpful for comprehensively understanding this novel material.     

2D/2D SnO2 nanosheets/Ti3C2Tx MXene nanocomposites for detection of triethylamine at low temperature

Highly active two-dimensional (2D) nanocomposites have been widely concerned in the field of gas sensors because of their unique advantages and synergistic effects. 2D/2D SnO₂ nanosheets/Ti₃C₂T_x MXene nanocomposites were synthesized by using layered Ti₃C₂T_x MXene and uniform SnO₂ nanosheets by hydrothermal method. Characterization results show that the SnO₂ nanosheets are well dispersed and vertically anchored on the layered Ti₃C₂T_x MXene surface, forming heterogeneous interfaces. Based on the gas-adsorption capabilities and synergistic effects of electronic properties, SnO₂ nanosheets/Ti₃C₂T_x MXene nanocomposites show high triethylamine (TEA) gas-sensing performance at low temperature (140 °C). The sensor responses of the nanocomposites and pure SnO₂ nanosheets to 50 ppm of TEA are 33.9 and 3.4, respectively. An enhancement mechanism for SnO₂ nanosheets/Ti₃C₂T_x MXene nanocomposites is proposed for highly sensitive and selective detection of TEA at low temperature. The combination strategy of two-dimensional metal oxide semiconductor and multilayer MXene provides a new way for the development of cryogenic gas sensors in the future.     

Scavenging activity and reaction mechanism of Ti3C2Tx MXene as a novel free radical scavenger

A novel free radical scavenger, multi-layered Ti₃C₂T_x MXene (ML-Ti₃C₂T_x), has been studied by evaluating its scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH?). It exhibits high scavenging efficiency (95% in 10 min) at low dosage (0.06 mg/mL). Based on the analysis of structure and surface states of ML-Ti₃C₂T_x before and after reaction with DPPH? and a series of comparative experiments, including few-layered Ti₃C₂T_x MXene (FL-Ti₃C₂T_x), original Ti₃AlC₂, and soluble Ti species derived from ML-Ti₃C₂T_x, the observed high scavenging activity is attributed to the intrinsic reducing property of ML-Ti₃C₂T_x rather than the hydrogen donation ability from surface functional groups. A model is proposed to explain the scavenging mechanism.     

Improvement of gas sensing property for two-dimensional Ti3C2Tx treated with oxygen plasma by microwave energy excitation

Two-dimensional layered Ti₃C₂T_x MXene was prepared through hydrothermal etching method with LiF and hydrochloric (HCl) acid. Ti₃C₂T_x was further treated with oxygen plasma activated by microwave energy to obtain the activated Ti₃C₂T_x at different temperatures ranging from 350 °C to 550 °C. The gas-sensing properties of raw Ti₃C₂T_x and Ti₃C₂T_x activated with oxygen microwave plasma were tested toward different volatile organic compounds gases. The results indicated that Ti₃C₂T_x activated at 500 °C exhibited excellent gas-sensing properties at room temperature (25 °C) to 100 ppm ethanol with a value of 22.47, which is attributed to the enhancement of the amount of oxygen functional groups and defects on the MXene Ti₃C₂T_x film, and in turn to lead to more oxygen molecules adsorption and desorption reaction in the active defect sites. The enhancement of ethanol-sensing performance demonstrated that the activated Ti₃C₂T_x possess great potential in gas sensing.     

Advanced Ti3C2Tx MXene-modified cement nanocomposites toward high efficiency electromagnetic functional materials for green buildings

The proliferation of electronic devices and wireless communication is leading to serious electromagnetic (EM) interference. In this work, Ti₃C₂/cement composites were developed as high efficiency EM functional materials by introducing exfoliated Ti₃C₂T_x MXene with cement for green buildings with EM shielding function. In the composites, few-layered Ti₃C₂ MXene were dispersed homogeneously throughout the cement matrix. The EM properties of the composites were studied as a function of the MXene content. With increasing MXene content, real and imaginary part of permittivity was significantly improved owing to the polarization and electrical conduction caused by the MXene phase. Composites with 15 wt.% MXene showed good EM absorbing properties with a maximum effective absorbing bandwidth of 2.67 GHz. Strong EM shielding can be achieved when MXene content increased to 25 wt.%. The EM shielding effectiveness of such composites was higher than 22.0 dB, and the dominating shielding mechanism was EM absorption. This work finds new materials for the development of advanced green buildings with EM shielding function.     

Electrochemical storage mechanism of interstratification-assembled Ti3C2Tx MXene/NiCo-LDHs electrode in alkaline,acid and neutral electrolytes

Different kinds of two-dimensional hybrid electrodes have high theoretical capacitance and energy density. However, the origin of the electrochemical storage mechanism still remains elusive in alkaline, acid and neutral electrolytes. Herein, the interstratification-assembled Ti₃C₂T_x MXene/NiCo-LDHs electrodes were successfully prepared and studied in different electrolytes by in-situ Raman spectroscopy. The results show that H₂O molecules in neutral electrolyte combine with –OH at the end of Ti₃C₂T_x MXene during charging, and debonding occurs during discharge. Similarly, this reaction also occurs in the discharge process with NiCo-LDHs and provides smaller pseudocapacitance characteristics. Although this pseudocapacitance reaction also occurs in acidic and alkaline electrolytes, however, the difference is that the hydrogen ions will promote the electrochemical performance of Ti₃C₂T_x MXene and has a certain corrosion consumption effect on NiCo-LDHs, but generally improve the electrochemical performance of Ti₃C₂T_x MXene/NiCo-LDHs. Interestingly, the OH^? in alkaline electrolyte can promote the electrochemical performance of NiCo-LDHs, and produce a new electrochemical reaction with –F between the layers of Ti₃C₂T_x MXene, which greatly improves the overall electrochemical performance of this hybrid electrodes. As a result, Ti₃C₂T_x MXene/NiCo-LDHs electrodes have the best electrochemical performance in alkaline electrolyte with capacitance of 283 F g^?1, energy density of 14.2 Wh kg^?1 and power density of 3007.1 W kg^?1. This work lays a foundation for the preparation of high-performance two-dimensional hybrid electrochemical energy storage devices.     

P-doped MoS2/Ni2P/Ti3C2Tx heterostructures for efficient hydrogen evolution reaction in alkaline media

By combining the advantages of doping to change the electronic structure of molybdenum disulfide (MoS₂), transition metal phosphides, and MXene, we proposed the idea of designing and preparing a new type of composite material, P-doped MoS₂/Ni₂P/Ti₃C₂T_x heterostructures (denoted as P@MNTC), to serve as the hydrogen evolution reaction (HER) catalyst of electrochemical water splitting. The as-prepared P@MNTC heterostructures show a significant HER activity with an overpotential of 120 mV at 10 mA cm^–2 in alkaline electrolyte, with decreasing 105 and 125 mV compared with those of MoS₂ and MXene, respectively. The density functional theory indicates that the P doping and synergy effect of Ti₃C₂T_x can enhance the activation of MoS₂ and thus promote dissociation and absorption of H₂O during HER process. This strategy provides a promising way to develop high-efficiency MoS₂- and Ti₃C₂T_x-based composite catalysts for alkaline HER.     

Enhancing the lithium storage capabilities of TiO2 nanoparticles using delaminated MXene supports

MXenes, an emerging family of two-dimensional materials, were promising electrode materials due to their excellent electronic conductivity and hydrophilicity. MXenes exhibit extraordinary rate performance and cycling stability when serving as the anode materials for Li-ion batteries, but they have relatively low capacities. We thus prepared Ti₃C₂T_x/TiO₂ composites using a simple route to coat TiO₂ nanoparticles onto the delaminated few-layered MXenes, which functioned as spacers in the composite to suppress the restacking of MXene layers. The sample demonstrated excellent performance in the galvanostatic charge-discharge test, where a reversible capacity of 143?mA?h?g^?1 could still be maintained after 200 cycles at 0.5?A?g^?1 and a distinct plateau region could be clearly observed in the charge-discharge profiles. Density Theory Function calculation revealed that the hybridization of few-layered MXene was able to improve the structural stability of the composite during the insertion/de-insertion of Li atoms.     

Ti2CTx MXene: A novel p-type sensing material for visible light-enhanced room temperature methane detection

The development of semiconductor-based room-temperature methane (CH₄) gas sensors is appealing but challenging. Herein, we report a CH₄ gas sensor operating at room temperature based on Ti₂CT_x MXene, a novel p-type sensing material, achieving high-performance CH₄ detection with visible light assistance. The Ti₂CT_x MXene based device showed more than seven-fold improvement for CH₄ detection under visible-light irradiation, and the response/recovery times were also sharply decreased. The excellent CH₄ sensing performance at room temperature could be attributed to the visible-light photocatalytic CH₄ oxidation activity of the Ti₂CT_x sensing material. CH₄ oxidation was revealed by photocatalytic measurement, O₂-TPD and in-situ IR spectroscopies. The present work demonstrates the novel application of Ti₂CT_x MXene as a promising p-type sensing material for methane detection at room temperature. Moreover, the concept of “photocatalysis-enhanced gas sensing” can be employed in room-temperature gas sensors based on other novel semiconductors.     

Co-Catalyst Ti3C2TX MXene-Modified ZnO Nanorods Photoanode for Enhanced Photoelectrochemical Water Splitting

In order to obtain a high photoelectrochemical performance, co-catalysts loading is the most commonly used way, which can facilitate reactions and suppress the charge recombination. In this paper, a novel composite of ZnO/Ti₃C₂T_X photoanode was fabricated by a facile spin coating of precipitating Ti₃C₂T_X (MXene) flakes onto the surface of ZnO, as co-catalyst for enhanced photoelectrochemical (PEC) water splitting. Under simulated sunlight, the optimum composite of ZnO/Ti₃C₂T_X photoanode showed the photocurrent density as 1.2 mA cm^?2 at 1.23 V_RHE, which is 1.4 times higher than that of pristine ZnO without Ti₃C₂T_X co-catalyst (0.83 mA cm^?2 at 1.23 V_RHE). The ZnO/Ti₃C₂T_X photoanode showed a photoconversion efficiency of 0.32% and maintained a stable photocurrent over 2000s. The Ti₃C₂T_X (MXene) flakes as co-catalyst to promote the charge transfer and accelerates the reaction kinetics in ZnO/Ti₃C₂T_X photoanode. This work delivers a two-dimensional (2D) material Ti₃C₂T_X (MXene) as co-catalyst for enhanced ZnO photoanode PEC water splitting.

     

Enhanced room temperature ammonia response of 2D-Ti3C2Tx MXene decorated with Ni(OH)2 nanoparticles

Due to the expansion of human production activities, toxic ammonia (NH₃) is excessively released into the atmosphere, being a huge threat to human health and the natural environment. Therefore, it is of great significance to design an easy-synthesized gas-sensing material with both good room temperature sensitivity and selectivity for trace-level NH₃ detection. Herein, we fabricate a chemiresistive NH₃ gas sensor with enhanced performance based on Ni(OH)₂/Ti₃C₂T_x hybrid materials. The Ni(OH)₂/Ti₃C₂T_x hybrid materials are synthesized by an in-situ electrostatic self-assembly method. Attributed to the formation of interfacial heterojunctions and the modulation of carrier density, the Ni(OH)₂/Ti₃C₂T_x hybrid sensor exhibits high response, outstanding repeatability, good selectivity and stability in low concentrations of NH₃. Moreover, the Ni(OH)₂/Ti₃C₂T_x hybrid sensor has a higher response to 10 ppm NH₃ at the relative humidity of 40% and 60%, which makes it promising for applications in real complex environments with high humidity. Benefitting from the low power consumption and easy fabrication process, the Ni(OH)₂/Ti₃C₂T_x hybrid sensor possesses a broad application prospect in the internet of things (IoT) environmental monitoring.     

Lightweight and robust Ti3C2Tx/carbon nanotubes foam with tuneable and highly efficient microwave absorption performance

In this study, a lightweight and robust Ti₃C₂T_x/carbon nanotubes (CNTs) foam (TCF) was fabricated using HCl-induced self-assembly, followed by vacuum freeze-drying. The electrical conductivity and mechanical elasticity of the TCF was higher than those of monolithic Ti₃C₂T_x foams. This was ascribed to the incorporation of CNTs into Ti₃C₂T_x preventing the stacking of the Ti₃C₂T_x nanosheets and producing a well-developed three-dimensional honeycomb-like porous network structure, which considerably improved impedance matching, promoted multiple reflection loss, increased conduction loss and polarisation loss, thus imparting remarkable microwave absorption properties to the TCF. The 1.72 and 1.92 mm thick TCF samples with absorber loadings of 4 wt%, which were obtained by immersing TCF into molten paraffin, followed by cutting it into coaxial rings, presented an optimum reflection loss of ?48.8 dB and a maximum effective absorption bandwidth (EAB) of 5.44 GHz, respectively. Moreover, upon increasing the thickness of the TCF samples from 1.52 to 4.92 mm, the EAB could be regulated from 4.16 to 18 GHz, respectively. In this study, we developed a facile method for fabricating a lightweight and robust TCF, which met the ‘light, thin, broad, and strong’ criteria and presented a broad EAB and remarkable dissipation capability, for microwave absorption materials.     

Multilayer Ti3C2Tx: From microwave absorption to electromagnetic interference shielding

Ti₃C₂T_x MXene has attracted extensive attention in the field of electromagnetic (EM) protection over recent years. Multilayer Ti₃C₂T_x (M-Ti₃C₂T_x), as an intermediate product of MXene ultra-thin structure, has potential advantages in the field of EM protection. Herein, the M-Ti₃C₂T_x was obtained by HCl/LiF etching Ti₃AlC₂. The microwave absorption (MA) and electromagnetic interference (EMI) shielding performance of Ti₃AlC₂ and M-Ti₃C₂T_x were compared. The mechanism research of MA and EMI shielding indicates that the construction of local conductive network plays a leading role in the EM wave attenuation. The sample with 30% M-Ti₃C₂T_x display RL_min of ?50.26 dB, and corresponding bandwidth of 4.64 GHz at the thickness of 1.7 mm. Especially, the metastructure based on the EM parameters of M-Ti₃C₂T_x/wax exhibits ultra-wide bandwidth (15.54 GHz). Our research will provide a basis for the design of MXene-based EM protection performance.     

Bifunctional Ti3C2Tx–CNT/PANI composite with excellent electromagnetic shielding and supercapacitive performance

Ti₃C₂T_x exhibits excellent electromagnetic (EM) shielding and electrochemical properties. However, the inherent re-stacking tendency and easy oxidation of Ti₃C₂T_x limit its further application. In this study, a multi-walled carbon nanotube/polyaniline composite (CNT/PANI, denoted as C–P) was introduced into Ti₃C₂T_x nanosheets to obtain a Ti₃C₂T_x–CNT/PANI composite (T@CP). Owing to the integrated effects of Ti₃C₂T_x and C–P, the contribution of absorption was significantly improved, which finally enhanced the EM shielding performance of T@CP. The highest total EM shielding effectiveness (SE_T) was close to 50 dB (49.8 dB), which was substantially higher than that of pure Ti₃C₂T_x (45.3 dB). Moreover, T@CP demonstrated outstanding supercapacitive performance. The specific capacitance of T@CP (2134.5 mF/cm² at 2 mV/s) was considerably higher than that of pure Ti₃C₂T_x (414.3 mF/cm² at 2 mV/s). These findings provide a new route for the development of high-efficiency Ti₃C₂T_x-based bifunctional EM shielding and electrochemical materials.     

Morphology and photocatalytic activity of TiO2/MXene composites by in-situ solvothermal method

In this work, TiO₂/MXene composites were successfully synthesized through an in-situ solvothermal method, where the morphology of TiO₂ nanoparticles (NPs) was modified by different concentrations of agents. Ti₃C₂T_x with electronic storage characteristics was employed as a co-catalyst to enhance the photocatalytic degradation activity by capturing photogenerated electrons. The experimental results reveal that, with the help of C₃H₈O agents, TiO₂ NPs are uniformly distributed on the surface of Ti₃C₂T_x. The TiO₂/Ti₃C₂T_x-C₃H₈O composite showed the highest photocatalytic activity of 90.5% after 75 min under mercury light irradiation, which is 57.9% higher than that of the pure TiO₂ photocatalyst. The photocatalytic activity is promoted due to the high photoelectron transmission performance of the TiO₂/Ti₃C₂T_x composites.     

Core@shell and sandwich-like Ti3C2Tx@Ni particles with enhanced electromagnetic interference shielding performance

Novel and highly effective electromagnetic interference (EMI) shielding materials are desirable to attenuate unwanted electromagnetic radiation or interference produced by electrical communication devices. Here, functional Ti₃C₂T_x@Ni particles with a core@shell and sandwich like structure were fabricated using the facile electroless plating technique. The core@shell structured Ti₃C₂T_x@Ni consists of a Ti₃C₂T_x core and a Ni shell. In the core, thin Ni layers are sandwiched in between Ti₃C₂T_x flakes. EMI shielding effectiveness (SE) values of Ti₃C₂T_x@Ni/wax composites increased with increasing Ti₃C₂T_x@Ni content. The average EMI SE value of 60 wt% Ti₃C₂T_x@Ni/wax composite was 43.12 dB, increased by 73% as compared with 24.93 dB for the same content of pristine Ti₃C₂T_x in wax in the frequency range 2–18 GHz. An average EMI SE of 74.14 dB was achieved in the 80 wt% Ti₃C₂T_x@Ni/wax. The enhanced EMI shielding performance should be ascribed to the synergic effect of the absorption loss of the Ti₃C₂T_x core and the magnetic loss of the Ni shell and the inner Ni layers.     

Fabrication of PANI@Ti3C2Tx/PVA hydrogel composite as flexible supercapacitor electrode with good electrochemical performance

Developing a new strategy to effectively prevent the restacking of MXene nanosheets will have significant impacts on designing flexible supercapacitor electrodes. Herein, a novel Ti₃C₂T_x/polyvinyl alcohol (PVA) porous sponge with 3D interconnected structures is prepared by sol-gel and freeze-dried methods. This Ti₃C₂T_x/PVA porous sponge is used as the template of in-situ polyaniline (PANI) polymerization, and the fabricated PANI@Ti₃C₂T_x/PVA hydrogel composite is applied as flexible supercapacitors electrodes. 1D conductive polymer chains PVA could increase the interlayer spacing of Ti₃C₂T_x nanosheets, which is beneficial to expose more electrochemical active sites. The supercapacitor based on PANI@Ti₃C₂T_x/PVA hydrogel composite exhibits the coexistence of double-layer capacitance and pseudocapacitance behavior. This supercapacitor shows a maximum areal specific capacitance of 103.8 mF cm^?2 at 2 A m^?2, and it also exhibits a maximum energy density of 9.2 μWh·cm^?2 and an optimum power density of 800 μW cm^?2. The capacitance of this supercapacitor is almost not change under different bending angles. Moreover, 99% capacitance retention is achieved after 10 000 charge/discharge cycles of the supercapacitor. The synergistic effect between PANI and Ti₃C₂T_x/PVA composite may improve the number of reactive sites and provide efficient channels for ion diffusion/electron transport.