Fe~(3+) -stabilized Ti_3C_2T_x MXene enables ultrastable Li-ion storage at low temperature

It is highly important to develop ultrastable electrode materials for Li-ion batteries(LIBs),especially in the low temperature.Herein,we report Fe³⁺-stabilized Ti₃C₂T_x MXene(donated as T/F-4:1)as the anode material,which exhibits an ultrastable low-temperature Li-ion storage property(135.2 m A h g^-1after300 cycles under the current density of 200 m A g^-1at-10℃),compared with the negligible capacity for the pure Ti₃C₂T_x MXene(26 m A h g^-1at 200 m A g^-1).We characterized as-made T/F samples via the Xray photoelectron spectroscopy(XPS),Fourier transformed infrared(FT-IR)and Raman spectroscopy,and found that the terminated functional groups(-O and-OH)in T/F are Li⁺ storage sites.Fe³⁺-stabilization makes-O/-OH groups in MXene interlayers become active towards Li⁺,leading to much more active sites and thus an enhanced capacity and well cyclic stability.In contrast,only-O/-OH groups on the top and bottom surfaces of pure Ti₃C₂T_x MXene can be used to adsorb Li⁺,resulting in a low capacity.Transmission electron microscopy(TEM)and XPS data confirm that T/F-4:1 holds the highly stable solid electrolyte interphase(SEI)layer during the cycling at-10℃.Density functional theory(DFT)calculations further uncover that T/F has fast diffusion of Li⁺ and consequent better electrochemical performances than pure Ti₃C₂T_x MXene.It is believed that the new strategy used here will help to fabricate advanced MXene-based electrode materials in the energy storage application.     

Low-Temperature Growing Anatase TiO2/SnO2 Multi-dimensional Heterojunctions at MXene Conductive Network for High-Efficient Perovskite Solar Cells

A multi-dimensional conductive heterojunction structure,composited by TiO2,SnO2,and Ti3C2TX MXene,is facilely designed and applied as electron transport layer in efficient and stable planar perovskite solar cells.Based on an oxygen vacancy scramble effect,the zero-dimensional anatase TiO2 quantum dots,surrounding on two-dimensional conductive Ti3C2TX sheets,are in situ rooted on three-dimensional SnO2 nanoparticles,constructing nanoscale TiO2/SnO2 heterojunctions.The fabrication is implemented in a controlled lowtemperature anneal method in air and then in N2 atmospheres.With the optimal MXene content,the optical property,the crystallinity of perovskite layer,and internal interfaces are all facilitated,contributing more amount of carrier with effective and rapid transferring in device.The champion power conversion efficiency of resultant perovskite solar cells achieves 19.14%,yet that of counterpart is just 16.83%.In addition,it can also maintain almost 85%of its initial performance for more than 45 days in 30–40%humidity air;comparatively,the counterpart declines to just below 75%of its initial performance.     

Needle-like Zn-doped SnO2 nanorods with enhanced photocatalytic and gas sensing properties

Zn-doped SnO(2) nanorods have been prepared by a simple hydrothermal method on a large scale. The as-prepared samples were characterized by x-ray powder diffraction, scanning electron microscope, transmission electron microscope, energy dispersive spectrometer, x-ray photoelectron spectroscopy, UV-vis absorption spectra and photoluminescence spectra. Studies found that the products are needle-like single-crystalline nanorods grown along the [[Formula: see text]] orientation. The photocatalytic properties of the synthesized Zn-doped SnO(2) were investigated by decomposing acid fuchsine, showing much higher photocatalytic activity than pure SnO(2) nanorods and bulk SnO(2) powders. An enhanced gas sensing ability toward methanal, ethanol and acetone gases is also achieved in high sensitivity and fast response. The origins of the enhanced performances are discussed.     

Design and development of SnO decorated BaTiO3 heterostructure device platform for ethanol vapor detection

Herein, we reported the SnO decorated BaTiO₃ heterostructure as well as pristine BaTiO₃ based ethanol gas sensing properties examined. Barium titanate (BaTiO₃) and tin oxide (SnO) materials have been successfully synthesized by the hydrothermal alkaline solution technique. Structural investigations carried out by X-ray diffraction (XRD) analysis suggested the cubic phase of BaTiO₃ and the tetragonal SnO phase of the materials. Transmission electron microscopy (TEM) suggested irregular nanospheres of BaTiO₃ and micro sheets of SnO. The macroporous nature of BaTiO₃ and mesoporous nature of SnO were confirmed through Brunauer–Emmett–Teller (BET) analysis.   The fabricated device of BaTiO₃/SnO heterostructure shows sensor response of 10% with the fast response/recovery time of 1.9/1.6 s at the operating temperature of 150 °C for 500 ppm of ethanol vapor. The highest performance for the BaTiO₃/SnO heterostructure device was found to be sensor performance of 343% for 500 ppm of ethanol vapor with fast response time of 2.4 s at the operating temperature of 250 °C and it shows excellent sensor response at higher temperature. 

     

Fabrication of Fe nanocomplex pillared few-layered Ti3C2Tx MXene with enhanced rate performance for lithium-ion batteries

Pillaring technologies have been considered as an effective way to improve lithium storage performance of Ti₃C₂T_xMXene.Nevertheless,the pillared hybrids suffer from sluggish Li⁺diffusion kinetics and electronic transportation due to the compact multi-layered MXene structure,thus exhibiting inferior rate performance.Herein,the few-layered Ti₃O₂MXene(f-Ti₃C₂MXene)which is free from restacking can be prepared quickly based on the NH4⁺ions method.Besides,Fe nanocomplex pillared few-layered Ti₃C₂T_x(FPTC)heterostructures are fabricated via the intercalation of Fe ions into the interlayer of f-Ti₃C₂MXene.The f-Ti₃C₂MXene which is immune to restacking can provide a highly conductive substrate for the rapid transport of Li+ions and electrons and possess adequate electrolyte accessible area.Moreover,f-Ti₃C₂MXene can efficiently relieve the aggregation,prevent the pulverization and buffer the large volume change of Fe nanocomplex during lithiation/delithiation process,leading to enhanced charge transfer kinetics and excellent structural stability of FPTC composites.Consequently,the FPTC hybrids exhibit a high capacity of 535 mAh·g^-1after 150 cycles at 0.5 A·g^-1and an enhanced rate performance with 310 mAh·g^-1after 850 cycles at 5 A·g^-1.This strategy is facile,universal and can be extended tofabricate various few-layered MXene-derived hybrids with superior rate capability.     

Influence of surfaces and interfaces on MXene and MXene hybrid polymeric nanoarchitectures,properties, and applications

Journal of Materials Science - The inculcation of interlayer spacing sarchitectures between MXene (M-X) sheets is a simplified approach to inhibit restacking of Ti3C2Tx sheets and hinder this...     

Enhanced Q-switching performance of magnetite nanoparticle via compositional engineering with Ti3C2 MXene in the near infrared region

In this work,we reported a new strategy to improve the nonlinear saturable absorption performance of magnetite (Fe3O4) nanoparticles (FONPs) via the compositional engineering with the Ti3C2 MXene in the near-infrared (NIR) region.Based on the DFT simulation,the band structures and work function were significantly modified by the Ti3C2 MXene doping.By using the open-aperture Z-scan technology,the nonlinear optical features of the FONPs@Ti3C2 nanocomposite were significantly improved,show-ing the great potential as the saturable absorber in the pulsed laser.With the nanocomposite as the saturable absorber,the passively Q-switched Nd∶GdVO4 lasers emitted much shorter pulse durations when compared with the pristine FONP saturable absorber.These findings indicated that FONPs@Ti3C2 heterostructure was a promising saturable absorber for the short pulse generation in the NIR region.     

Facile control of C₂H₅OH sensing characteristics by decorating discrete Ag nanoclusters on SnO₂ nanowire networks

The effect of Ag decoration on the gas sensing characteristics of SnO(2) nanowire (NW) networks was investigated. The Ag layers with thicknesses of 5-50 nm were uniformly coated on the surface of SnO(2) NWs via e-beam evaporation, which were converted into isolated or continuous configurations of Ag islands by heat treatment at 450 °C for 2 h. The SnO(2) NWs decorated by isolated Ag nano-islands displayed a 3.7-fold enhancement in gas response to 100 ppm C(2)H(5)OH at 450 °C compared to pristine SnO(2) NWs. In contrast, as the Ag decoration layers became continuous, the response to C(2)H(5)OH decreased significantly. The enhancement and deterioration of the C(2)H(5)OH sensing characteristics by the introduction of the Ag decoration layer were strongly governed by the morphological configurations of the Ag catalysts on SnO(2) NWs and their sensitization mechanism.     

The template-free synthesis of square-shaped SnO(2) nanowires: the temperature effect and acetone gas sensors

Square-shaped single-crystalline SnO(2) nanowires and their sphere-like hierarchical structures were synthesized successfully with a template-free hydrothermal approach. It was found that an intermediate phase-Na(2)Sn(OH)(6)-is first produced because it is slow to dissolve in ethanol/water media. The intermediate phase gradually decomposes and converts into SnO(2) at temperatures higher than 200?°C. The reaction temperature also affects the microstructure of SnO(2) nanomaterials. Uniform square-shaped SnO(2) nanowires, which form sphere-like hierarchical structures in 100% structure yield, can be produced at 285?°C on a large scale. The diameter of the nanowires shows a decrease accompanying the increase of the reaction temperature. The temperature effect could be a result of the faster and oriented growth of SnO(2) nanowires along their [Formula: see text] direction at higher temperature. Chemical sensors constructed with square-shaped SnO(2) nanowires exhibit excellent stability, good sensitivity and selectivity, as well as a quick response and short recovery times under exposure to acetone gas in practical applications.     

Sol—Gel法制备ZrO2—SnO2薄膜的常温气敏机理

根据Ｓｏｌ－Ｇｅｌ工艺制备的ＺｒＯ２－ＳｎＯ２薄膜的气敏性能数据，提出了常温下ＳｎＯ２（ＺｒＯ２）薄膜对Ｈ２Ｓ的气敏机理模型。根据此模型所得定量分析结果与实验结果一致。     

Investigation of adjacent spacing dependent microwave absorption properties of lamellar structural Ti3C2Tx MXenes

Ti₃C₂Tx MXenes and their composites play a vital role in the research on microwave absorbing materials. Herein, the different interlamellar spaces of Ti₃C₂Tx MXene materials were prepared by an etching process. The dependence of the microwave absorbing properties of the Ti₃C₂Tx MXene nanosheets on different interlamellar spaces was studied. The complex permittivity, dielectric loss, impedance matching characteristic and the minimum reflection loss (RL) value with the variation in interlamellar space were systematically investigated. Results showed that 40% ratio paraffin-bonded composites (S3) have a strong electromagnetic wave absorption performance and large effective absorbing bandwidth. The maximum RL reaches −36.3 dB at 4.67 GHz with the thickness of 4.5 mm, ascribed to its a high dielectric loss and good impedance matching characteristics. The RL value of Ti₃C₂Tx MXenes is strongly dependent on the inter-lamellar space. The enhanced microwave absorption originates from the unique 2-D structure, good impedance matching characteristics, and enhanced space-charge polarization effects. This work provides a new avenue for exploring high-performance microwave absorbers based on MXene materials.     

SnO/SnO2 heterojunction: an alternative candidate for sensing NO2 with fast response at room temperature

The SnO₂-based family is a traditional but important gas-sensitive material. However, the requirement for high working temperature limits its practical application. Much work has been done to explore ways to improve its gas-sensing performance at room temperature (RT). For this report, SnO₂, SnO, and SnO/SnO₂ heterojunction was successfully synthesized by a facile hydrothermal combined with subsequent calcination. Pure SnO₂ requires a high operating temperature (145 °C), while SnO/SnO₂ heterojunction exhibits an excellent performance for sensing NO₂ at RT. Moreover, SnO/SnO₂ exhibits a fast response, of 32 s, to 50 ppm NO₂ at RT (27 °C), which is much faster than that of SnO (139 s). The superior sensing properties of SnO/SnO₂ heterojunction are attributed to the unique hierarchical structures, large number of adsorption sites, and enhanced electron transport. Our results show that SnO/SnO₂ heterojunction can be used as a promising high-performance NO₂ sensitive material at RT.     

Y_2O_3-SnO_2常温气敏薄膜的Sol-Gel制备及性能研究

以无机盐ＳｎＣｌ２·２Ｈ２Ｏ,Ｙ（ＮＯ３）３·６Ｈ２Ｏ为原料,无水乙醇为溶剂,采用溶胶－凝胶工艺制备了Ｙ２Ｏ３掺杂的ＳｎＯ２薄膜．采用差热－失重分析研究了Ｙ２Ｏ３掺杂的ＳｎＯ２干凝胶粉末的热分解、晶化过程．研究了Ｙ２Ｏ３－ＳｎＯ２薄膜的电学和气敏性能．从实验中得到了Ｙ２Ｏ３掺杂份量对ＳｎＯ２薄膜电学及气敏性能的影响．实验表明Ｙ２Ｏ３掺杂的ＳｎＯ２薄膜在常温下对ＮＯｘ具有较好的灵敏度和选择性,并具有较好的响应恢复性能;在常温下对Ｈ２Ｓ气体也具有一定的灵敏度．     

Fabrication and highly sensitive gas sensors based on h-MoO3/SnO2 hollow nanostructures operated at low temperatures

Simulated by the synthesis of one dimensional hollow nanostructures with significant sensing, electrical, and optical properties, we have successfully synthesized 1D hollow nanostructures of h-MoO3/SnO2 with well-defined multi-side walls. These hollow nanostructured materials synthesized via a hydrothermal method with SnCl2.2H2O as the precursor and h-MoO3 as the template. SnO2 nanoparticles grew on the surface of h-MoO3 with preferential direction [001]. The morphological change was observed with variation of the growth conditions, such as HNO3, and h-MoO3 concentration. 1D hollow nanostructures of h-MoO3/SnO2 were studied and their growth mechanism was discussed. The result revealed that the existence of h-MoO3 caused to increase the sensor response to ethanol gas and downshift the sensor operating temperature at low temperatures.     

Nanowires assembled SnO2 nanopolyhedrons with enhanced gas sensing properties

Self-assembly of one-dimensional nanoscale building blocks into functional 2-D or 3-D complex superstructures has stimulated a great deal of interest. We report the synthesis and characterization of nanopolyhedrons assembled from ultrathin SnO(2) nanowires based on the sodium dodecyl sulfate (SDS)-assisted hydrothermal process. As-synthesized SnO(2) nanopolyhedrons have uniform diameters around 300 nm and are self-assembled by numerous ultrathin SnO(2) nanowires with diameters of 5-10 nm. The growth mechanism was also studied by investigating the samples synthesized at different reaction time. Thin films of the assembled SnO(2) nanopolyhedrons were configured as high performance sensors to detect methanol, ethanol, and acetone, which exhibited 1 ppm sensitivity, very fast response and recovery times (several seconds for different gases with concentrations of 1-200 ppm) to all the target gases and highly selective detection to acetone.     

Room temperature CO and H2 sensing with carbon nanoparticles

We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.     

Rutile structured SnO2 nanowires synthesized with metal catalyst by thermal evaporation method

One-dimensional (1-D) nanostructures such as tubes, rods, wires, and belts have attracted considerable research activities owing to their strong application potential as components for nanosize electronic or optoelectronic devices utilizing superior optical and electrical properties. Characterizing the mechanical properties of nanostructure is of great importance for their applications in electronics, optoelectronics, sensors, actuators. Wide-bandgap SnO2 semiconducting material (Eg = 3.6 eV at room temperature) is one of the attractive candidates for optoelectronic devices operating at room temperature, gas sensors, and transparent conducting electrodes. The synthesis and gas sensing properties of semiconducting SnO2 nanomaterials have became one of important research issues since the first synthesis of SnO2 nanobelts. Considering the important application of SnO2 in sensors, these structures are not only ideal systems for fundamental understanding at the nanoscale level, but they also have potential applications as nanoscale sensors, resonator, and transducers. The structured SnO2 nanorods have been grown on silicon substrates with Au catalytic layer by thermal evporation process over 800 degrees C. The resulting sample is characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS). The morphology and structural properties of SnO2 nanowires were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The mean diameter of the SnO2 nanorods grown on Au coated silicon (100) substrate is approximately 80 nm. In addition, X-ray diffraction measurements show that SnO2 nanorods have a rutile structure. The formation of SnO2 nanowires has been attributed to the vapor-liquid-solid (VLS) growth mechanisms depending on the processing conditions. We investigated the growth behavior of the SnO2 nanowires by variation of the growth conditions such as gas partial pressure and temperature.     

ZrO2掺杂对SnO2薄膜电性及气敏性的影响

本研究不用金属醇盐而以无机盐ＳｎＣｌ２．２Ｈ２Ｏ为主体原料，以Ｚｒ（ＯＣ３Ｈ７）４为掺杂剂，无水乙醇为溶剂，采用溶胶－疑胶Ｓｏｌ－Ｇｅｌ）工艺制备了不同ＺｒＯ２掺杂份量的ＳｎＯ２薄膜，发现ＺｒＯ２薄膜在常温下对Ｈ２Ｓ气体具有较好的气敏性能，同时本文研究了ＺｒＯ２掺杂份量对ＳｎＯ２薄膜导电率及气敏性能的影响。     

Effect of thickness on nanostructured SnO2 thin films by spray pyrolysis as highly sensitive H2S gas sensor

Nanostructured SnO2 thin films were prepared by spray pyrolysis technique onto glass substrates with different thickness by varying quantity of precursor solution. The structural, optical and electrical properties of these films have been studied. The crystallographic structure of the films was studied by X-ray diffraction (XRD). It is found that the films are tetragonal with (110) orientation. The grain size increases with thickness. Atomic Force Microscopy (AFM) showed that the nanocrystalline nature of the films with porous nature. The grain size increased 14 to 29 nm with increase in film thickness. The studies on the optical properties show that the direct band gap value decreases from 3.75 to 3.50 eV. The temperature dependence of the electrical conductivity was studied. The activation energies of the films are calculated from the conductance temperature characteristics. The nanostructured SnO2 thin films were used as sensing layers for resistive gas sensors. The dependence of gas sensing properties on the thickness of SnO2 thin films was investigated. The gas response of the SnO2 thin films towards the H2S gas was determined at an operating temperature of 150 degrees C. The sensitivity towards H2S gas is strongly depending on surface morphology of the SnO2 thin films.     

纳米SnO2基气敏元件对甲醛气体的检测

采用溶胶-凝胶法制备了纳米SnO2粉末,利用X射线衍射仪(XRD)以及原子力显微镜(AFM)对材料的晶体结构及晶粒尺寸进行了表征.采用制备的纳米SnO2作为基底材料,掺杂纳米TiO2粉末(SnO2与TiO2的物质的量之比为9:1)以及少量的Ag+(物质的量百分比为0.2%～0.4%),以此材料制成气敏元件,检测了元件的甲醛气敏性能.结果表明:该元件在工作温度为300℃时,对200×10-6的甲醛具有较好的敏感性,在不同的工作温度下,元件表现出良好的气敏选择性.理论计算表明,气体分子轨道能量的差异是元件气敏选择性的定性因素.