•The research highlights of this work are presented as following.•We synthesized a novel metal complex, [Cu(DDS)2(Cl)2(MeOH)2], as sensing material to construct mass sensitive QCM formaldehyde sensor. The complex is synthesized and grown in-situ on the copper layer deposited on QCM silver electrode so as to enhance the stability of sensing film.•The QCM sensor exhibits high sensitivity and selectivity toward gaseous formaldehyde. The detection limit for formaldehyde detection reaches down to 50 ppb.•Based on the temperature-varying micro-gravimetric experiment, enthalpy change is quantitatively obtained, which indicates that the interaction between the complex and HCHO molecules belongs to chemical adsorption. The values of ΔH calculated by Gaussian 09 indicate that chemical adsorption between NH2 group and aldehyde group play a leading role in detecting selectively formaldehyde gas.In order to construct highly sensitive and stable QCM gas sensor, we present an innovative strategy. Firstly, we employ a physical vapor deposition (PVD) method to coat a thin layer of copper on the surface of QCM silver electrode. Then, a novel metal complex as sensing material, [Cu(DDS)2(Cl)2(MeOH)2], is grown in-situ on the copper layer to ensure a strong coupling between metal complex sensing materials and QCM electrode. The sensing material is characterized through following instruments: elemental analysis, single crystal XRD, SEM, PXRD, IR spectra and TGA. The sensing test results indicate that the QCM sensor exhibit high sensitivity and selectivity toward gaseous formaldehyde because of a reversible interaction between amino group and HCHO molecule. The detection limit reaches down to 50 ppb. This implies the facile-fabricated sensor has a great potential in the area of rapid, stable, sensitive, and selective formaldehyde on-site detection. Based on the temperature-varying micro-gravimetric experiment, enthalpy change is quantitatively obtained, which indicates that the interaction between the complex and HCHO molecules belongs to chemical adsorption. The values of ΔH calculated by Gaussian 09 indicate that chemical adsorption between NH2 group and aldehyde group play a leading role in detecting selectively formaldehyde gas.

•Mesoporous TiO2-SiO2 functionalized with p-hexa-fluoroisopropanol aniline (HFIP) was synthesized to achieve highly sensitive toward nerve agent simulant dimethyl methylphosphonate.•The sensor was found that the observed frequency shifts gradually and turned saturated in the range from 10 to 60 ppm.•Gas sensing test results revealed that sensors had enhanced sensitivity due to the decoration of HFIP on TiO2-SiO2 in a ppb level.•Furthermore, when the doping of HFIP reached 20 wt%, the sensors achieved the best sensing performance.Mesoporous TiO2-SiO2 functionalized with p-hexa-fluoroisopropanol aniline (HFIP) was designed and synthesized to achieve highly sensitive and selective sensing toward nerve agent simulant dimethyl methylphosphonate (DMMP) due to a hydrogen bonding between target DMMP and TiO2-SiO2-HFIP. The sensing experiments were conducted by coating compounds onto quartz crystal microbalance (QCM) transducers. It was found that the observed frequency shifts gradually and turned saturated in the range from 10 to 60 ppm. Gas sensing test results revealed that sensors had enhanced sensitivity due to the decoration of HFIP on TiO2-SiO2 in a ppb level. Furthermore, when the doping of HFIP reached 20 wt%, the sensors achieved the best sensing performance. In conclusion, the QCM sensor coated with mesoporous TiO2-SiO2-HFIP exhibited fast response, excellent reversibility and high selectivity to nerve agent stimulant DMMP vapor, implying that mesoporous TiO2-SiO2-HFIP may be a good candidate for sensing DMMP.

•Through linking effectively sensing probe and a hydrophobic group, the formaldehyde sensor exhibits excellent response stability and gas selectivity under a wide relative humidity range.•We discovered that the amount of probe molecule can be tuned by controlling their dispersity under ultrasonic irradiation.•The calculation results reveal Schiff base interaction between the amine group and aldehyde group is more responsible for formaldehyde sensing instead of hydrogen bond interaction between carbamido and aldehyde group.•We design an adsorption isotherm experiment to extract the ΔH of formaldehyde adsorption. The adsorption isotherm experiments reveal that adsorption enthalpy change between DDS urea dry-gel and HCHO molecules locates the range of chemical adsorption, endowing the sensor satisfactory selectivity and reversibility.The work designs a novel hydrophobic organic dry-gel named diamino diphenyl sulfone (DDS) urea for selectively detecting formaldehyde in air. It is synthesized by using octadecylisothiocyanate and diamino diphenyl sulfone as reactants in tetrahydrofuran solution at 70 °C. The dry-gel is obtained by freezing drying. Sulfanilamide urea dry-gel acts as the contrastive material which is synthesized in a similar condition. The dry-gel coated Quartz Crystal Microbalance (QCM) sensor exhibits a rapid and reversible selective response towards formaldehyde gas. Repeated measurement results show high sensitivity and low detection limit (1 ppm) for formaldehyde detection. The gas sensing and contact angle tests indicate its stability under different humidity conditions. Based on the adsorption isotherm experiments, it reveals that adsorption enthalpy change between DDS urea dry-gel and HCHO molecules locates the range of chemical adsorption, endowing the sensor satisfactory selectivity and reversibility. Sensing mechanism of formaldehyde sensor has been proved by a simulation calculation based on a quantum chemistry software Gaussian though comparing the interaction between amine group or carbamido and formaldehyde. The calculation results reveal that Schiff base interaction between the amine group and aldehyde group is more responsible for formaldehyde sensing instead of hydrogen bond interaction between carbamido and aldehyde group.

•A novel biosensing method combining target recycling signal-amplification strategy and a homemade electrochemical device.•The target recycling was achieved by a strand displacement process, no needing the help of any nucleases.•This biosensing method can detect target DNA at aM level and can distinguish target DNA from interfering DNAs.•The biosensing method can work well with serum samples.Ultrasensitive biosensing technologies without gene amplification held great promise for direct detection of DNA. Herein we report a novel biosensing method, combining target recycling signal-amplification strategy and a homemade electrochemical device. Especially, the target recycling was achieved by a strand displacement process, no needing the help of any nucleases. In the presence of target DNA, the recycling system could be activated to generate a cascade of assembly steps with three hairpin DNA segments. Each recycling process were accompanied by a disassembly step that the last hairpin DNA segment displaces target DNA from the complex at the end of each circulation, freeing targets to activate the self-assembly of more trefoil DNA structures. This biosensing method could detect target DNA at aM level and can distinguish target DNA from interfering DNAs, demonstrating its high sensitivity and high selectivity. Importantly, the biosensing method could work well with serum samples.

A two-dimensional porous framework SHU-1 could undergo solvent-induced structural transformations to SHU-1a in methanol and SHU-1b in water. SHU-1, SHU-1a and SHU-1b showed selective adsorption towards malachite green.

Correction for ‘Synthesis and chlorine sensing properties of nanocrystalline hierarchical porous SnO2 by a phenol formaldehyde resin-assisted process’ by Wang Hui et al., CrystEngComm, 2010, 12, 1280–1285.

Heterojunction structured MASnI3/TiO2 photocatalysts (MA represents CH3NH3+) are prepared via a facile wet-chemical method and characterized by various techniques. The characterization demonstrates the formation of a heterojunction structure and the good crystallinity of MASnI3/TiO2 (1 : 9) (mass ratio of MASnI3 and TiO2 is 1 : 9). Moreover, the results also display the improved visible light absorption of MASnI3/TiO2 (1 : 9) and low recombination of photoinduced carriers. As a result, MASnI3/TiO2 (1 : 9) could completely degrade rhodamine B (97%) in 40 min, which has higher photocatalytic ability than pure MASnI3 and pure TiO2. The improved photocatalytic activity could be ascribed to the improved light harvesting ability and easy transfer of photogenerated carriers of the materials generated by the formation of a heterojunction structure and the suitable energy band position between MASnI3 and TiO2. In particular, coupling of MASnI3 and TiO2 could also avoid oxidation and hydrolysis of MASnI3 so that the long-term stability of the composite could be efficiently maintained. It is the first report on MASnI3 and TiO2 composites being used as photocatalysts for dye degradation. A possible mechanism for the enhancement of photocatalytic activity under light irradiation is also proposed.

In this work, we demonstrated the enhanced oxygen evolution reaction (OER) activity of flower-shaped cobalt-nickel oxide (NiCo2O4) decorated with iridium-nickel bimetal as an electrode material. The samples were prepared by carefully depositing pre-synthesized IrNi nanoparticles on the surfaces of the NiCo2O4 nano-flowers. Compared with bare NiCo2O4, IrNi, and IrNi/Co3O4, the IrNi/NiCo2O4 exhibited significantly enhanced electrocatalytic activity in the OER, including a lower overpotential of 210 mV and a higher current density at an overpotential of 540 mV. We found that the IrNi/NiCo2O4 showed more efficient electron transport behavior and reduced polarization because of its bimetal IrNi modification by analyzing its Tafel slope and turnover frequency. Furthermore, the electrocatalytic mechanism of IrNi/NiCo2O4 in the OER was studied, and it was found that the combined active sites of the composite effectively improved the rate determining step. The synergic effect of the bimetal and metal oxide plays an important role in this reaction, enhancing the transmission efficiency of electrons and providing more active sites for the OER. The results reveal that IrNi/NiCo2O4 is an excellent electrocatalyst for OER.本文制备了一种双金属IrNi修饰的花状NiCo2O4复合材料, 并研究了其对于氧析出反应的电化学活性, 结果显示其电化学活性明显提升. NiCo2O4和IrNi分别通过水热法和热分解法制备, 再通过超声复合, 使得双金属附着在复合氧化物表面. 通过与纯NiCo2O4, IrNi以及IrNi/Co3O4相比较, 所制备的IrNi/NiCo2O4对于氧析出反应的性能最为优异. 在各个参数指标中, 拥有最低的过电势210 mV, 在540 mV的过电势下具有最高的电流密度. 电子转移数和塔菲尔斜率分析表明该复合材料由于修饰上了双金属材料, 极大地降低了极化, 具有更高效的电子转移速率. 此外本文还对电催化机理进行了研究, 发现复合材料结合反应位点有效改善了反应速率决定步骤. 其中, 协同效应起着至关重要的作用, 这一效应明显提高电子传输效率的同时提供了更多的活性位点. IrNi/NiCo2O4是一种出色的氧析出反应电催化剂.

•To clarify the fundamental question of how (0001) facet of ZnO exhibits a better gas sensing performance than (10 0) facet, we calculated the chemisorption energy of an oxygen molecule (O2) on different facets of ZnO by density functional theory.•Our calculations show that the reduced energy is 1.0665 eV when the O2 molecule is chemically absorbed on the (0001) facet while 0.5233 eV on the (10 0) facet.•The higher the reduced energy is, the stronger the chemisorption of oxygen will be.•It is easier for the reactive (0001) facet to chemically absorb O2 molecules than it is for the (10 0) facet under the same conditions.•It can well explain why ZnO nanostructure with more (0001) facets shows a superior gas sensing performance.Herein, we focused on the effects of exposed crystal planes on the gas sensing property of ZnO. For this purpose, we designed and synthesized two porous ZnO nanosheets with different exposed crystal facets (0001) and (101¯0) by a facile hydrothermal routes. The characterization results show that both the porous nanosheets have a near specific surface area about 7.5 m2/g, thickness about 100 nm, diameter about 5 μm and pore size of tens of nanometers. However, their dominating exposed crystal facets are (0001) and (101¯0), respectively. When employed them as sensing materials in gas sensors, porous ZnO nanosheets with dominating exposed (0001) facet exhibit a superior sensitivity than the (101¯0) one. The enhanced gas response is attributed to a large amount of oxygen vacancy defects and unsaturated dangling bonds existing in the ZnO nanosheets with exposed crystal facet (0001), which is favorable for the adsorption of gas molecular on the sensor surface and result in improvement of the gas response. Finally, the calculation of the chemisorption energy of oxygen on ZnO crystal facets also proves the reactive-facet-enhanced gas sensitivity.

Lithium-sulfur batteries can potentially be used as a chemical power source because of their high energy density. However, the sulfur cathode has several shortcomings, including fast capacity attenuation, poor electrochemical activity, and low Coulombic efficiency. Herein, multi-walled carbon nanotubes (CNTs), graphene oxide (GO), and manganese dioxide are introduced to the sulfur cathode. A MnO2/GO/CNTs-S composite with a unique three-dimensional (3D) architecture was synthesized by a one-pot chemical method and heat treatment approach. In this structure, the innermost CNTs work as a conducting additive and backbone to form a conducting network. The MnO2/GO nanosheets anchored on the sidewalls of CNTs have a dual-efficient absorption capability for polysulfide intermediates as well as afford adequate space for sulfur loading. The outmost nanosized sulfur particles are well-distributed on the surface of the MnO2/GO nanosheets and provide a short transmission path for Li+ and the electrons. The sulfur content in the MnO2/GO/CNTs-S composite is as high as 80 wt %, and the as-designed MnO2/GO/CNTs-S cathode displays excellent comprehensive performance. The initial specific capacities are up to 1500, 1300, 1150, 1048, and 960 mAh g–1 at discharging rates of 0.05, 0.1, 0.2, 0.5, and 1 C, respectively. Moreover, the composite cathode shows a good cycle performance: the specific capacity remains at 963.5 mAh g–1 at 0.2 C after 100 cycles when the area density of sulfur is 2.8 mg cm–2.Keywords: carbon nanotube; graphene oxide; lithium sulfur; MnO2; polysulfide adsorption

SnCdxTe materials were synthesized by the zone-melting method for this thermoelectric performance study. The X-ray diffraction results show that the lattice parameter decreases with increasing x, following Vegard's law of rock-salt structure SnTe and CdTe. Besides, the room temperature Seebeck coefficients of the SnCdxTe system are enhanced to >60 μV K−1, larger than those of Cd-doped SnTe synthesized by spark plasma sintering. A large power factor of ∼25 μW cm−1 K−1 is achieved in SnCd0.12Te at 820 K, which rivals those of high performance PbTe-based materials. As a result, the highest ZT of ∼1.03 at 820 K was achieved for SnCd0.12Te.

The authors describe vertically aligned gold nanotube arrays (Au-NTAs) and gold nanowire arrays (Au-NWAs) that were directly grown in alumina oxide templates by galvanostatic deposition. The morphology of the gold arrays can be controlled by adjusting the pH value of the plating bath. Scanning electron microscopy shows the nanoarrays to be highly ordered (with an average length of around 2 μm), and the opening width of the gold nanotube arrays to be uniform (with diameters of around 50 nm). The electrocatalytic activities of the Au-NTAs and Au-NWAs deposited on a glassy carbon electrode toward glucose oxidation were compared by cyclic voltammetry and amperometry at pH 7.2. The Au-NTAs yield higher amperometric currents. The respective glucose sensor, when operated at a working potential of 0.25 V (vs. SCE), exhibits a linear range that extends from 5 μM to 16.4 mM concentrations of glucose, a sensitivity of 44.2 μA mM−1 cm−2, and a detection limit of 2.1 μM (at an S/N ratio of 3). The excellent sensing performance is attributed to the large surface area and the fast electron transfer rate for the one-dimensional gold nanoarrays.

Two-dimensional (2D) nanomaterials show great potential for electrocatalysis or other applications that require large surface area. In this work, we developed porous zinc–cobalt layered double hydroxide (Zn–Co-LDH) nanosheets by using a one-step microwave-assisted approach, and examine their oxygen evolution reaction (OER) performance. The Zn–Co-LDH nanosheets with a high specific surface area of 116.4 m2 g−1 exhibit good OER activity, expressed as low onset overpotential, small Tafel slope and large exchange current density. At the overpotential of 0.54 V, the current density of Zn–Co-LDH nanosheets is about 15.06 mA cm−2, which is much higher than that of Zn–Co-LDH nanoparticles. The comparable electrocatalytic performance may be attributed to the porous 2D structure generating more active sites and higher electronic conductivity. Furthermore, the obtained Zn–Co-LDH nanosheets show good stability during long time running at 1.55 V vs. RHE. Accordingly, an effective OER catalyst is exploited by using a simple microwave-assisted synthesis. Such an effective method could be extended to large-scale synthesis of uniform and stable 2D LDH nanomaterials.

A high-performance α-MoO3/multiwalled carbon nanotube (MWCNT) nanocomposite material is synthesized via a novel surfactant-assisted solvothermal process followed by low-temperature calcination. Its structure, composition, and morphology are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, carbon element analysis, nitrogen adsorption–desorption determination, scanning electron microscopy, and transmission electron microscopy techniques. Its electrochemical performance as a high-capacity lithium-ion-battery anode material is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/recharge methods. This composite material exhibits not only high capacity but also excellent rate capability and cyclability. For example, when the discharge/charge current density is increased from 0.1 to 2 A g–1, the reversible charge capacity is only decreased from 1138.3 to 941.4 mAh g–1, giving a capacity retention of 82.7%. Even if it is cycled at a high current density of 20 A g–1, a reversible charge capacity of 490.2 mAh g–1 is still retained, showing a capacity retention of 43.1%. When it is repeatedly cycled at a current of 0.5 A g–1, the initial reversible charge capacity is 1041.1 mAh g–1. A maximum charge capacity of 1392.2 mAh g–1 is achieved at the 292th cycle. After 300 cycles, a high charge capacity of 1350.3 mAh g–1 is maintained. Enhancement of the electrical conduction contributed by the MWCNT composite component as well as the loose and porous texture of the MoO3/MWCNT composite is suggested to be responsible for the excellent performance.Keywords: composite; conversion-type anode; crystalline α-MoO3 nanoparticles; lithium-ion battery; multiwalled carbon nanotubes;

•A novel two-step approach for synthesis of LiMn2O4/multiwalled carbon nanotube (MWCNT) composite Li-ion cathode materials is reported.•The synthetic approach possesses the merits of adjustable Li/Mn ratios for Li-Mn spinel, is time- and cost-saving as well as environmentally benign.•The LiMn2O4/MWCNT composite material has the features of high crystallinity of LiMn2O4 active material and low content of carbon nanotubes.•The LiMn2O4/MWCNT composite material exhibits very high specific capacity and excellent high-rate capability and long-term cyclability.Facile synthesis of highly crystalline spinel-type LiMn2O4/multiwalled carbon nanotube (MWCNT) composite by a novel two-step approach is achieved. This approach involves an acetone-assisted hydrothermal reaction in LiOH solution using previously prepared birnessite MnO2/MWCNT composite as a manganese containing precursor. The lithium manganate spinel Li0.81Mn2O4/MWCNT composite delivers a high specific capacity of 145.4 mAh g−1 at 0.1 C-rate, which is close to the theoretic capacity of LiMn2O4 (148 mAh g−1). Besides, it exhibits excellent high-rate capability and cyclability. For example, a discharge capacity of 114.8 mAh g−1 is retained even at a high charge/discharge current rate of 20C. When it is repeatedly cycled at 1C rate for 1000 cycles, the specific capacity is decreased from the initial value of 140.4 mAh g−1 to an end value of 98.7 mAh g−1, giving 70.3% capacity retention.

Porous rhombohedral In2O3 (corundum-type In2O3, rh-In2O3) with a morphology of uniform nanoflowers was fabricated by using a mild, facile solvent-thermal method. The formation mechanism and transformation of phase were studied. The results revealed that the precursors were transformed from In(OH)3 to InOOH with an increase in reaction time. The phase transformation was attributed to the stability of the InOOH phase at small crystal volume, less water molecules and small pH value, which in turn led to the formation of metastable rh-In2O3. The optimal working temperature of the sensor based on porous rh-In2O3 nanoflowers was proved to be 280 °C, corresponding to chemisorbed oxygen analysis based on a temperature changeable XPS, further demonstrating the surface resistance controlled gas sensing mechanism of In2O3. The sensor exhibited an enhanced response and rapid response/recovery toward ethanol vapour, which was ascribed to hierarchical porous structures and more active defects.

Tin telluride (SnTe) has recently attracted much attention as a promising thermoelectric material. In this work, SnTe is alloyed with additional Pb, and the high density crystalline ingots of SnPbxTe (x = 0, 0.02, 0.04, and 0.06) have been synthesized by a zone-melting method. Through this method, SnPbxTe samples show larger power factors than those prepared by other methods, and a maximum value of 30.5 μW cm−1 K−2 at 823 K has been reached in p-type SnPb0.02Te, which is the highest value reported so far. As a result, a promising figure of merit ZT of ∼0.81 has been obtained at 823 K.

A novel foam carbon (FC) material with partly graphitized and 3D interlaced thin carbon interlayer as skeleton was synthesized by an eco-friendly route. Fe3O4 nanoparticles (~20 nm) were loaded homogenously into pores of FC through simple impregnating and thermal treatment. The electrochemical property of Fe3O4/FC composite was evaluated by galvanostatic discharge/charge cycling, cyclic voltammetry, and impedance spectroscopy. The results showed that Fe3O4/FC nanocomposite possessed superior cycling stability and C-rate performance. A stable capacity of 1100 mAh g−1 was maintained at a current density of 0.1 C and the reversible capacity reached to 440 mAh g−1 at 5 C in C-rate test. The excellent performance is attributed to the desired composite structure of Fe3O4/FC, including homogenous distribution of nano-sized Fe3O4 particles, 3D interconnected electron transmission carbon network, and abundant interlinked pore channel, which guarantee quick electron and Li+ transfer as well as electrode structure undamaged during (de)lithiation process.

Fruit waste pomelo peel was employed as raw material to prepare a highly porous and partial graphitized carbon material (pomelo peel-derived carbon (PPDC)). Se/PPDC nanocomposite was fabricated through ball milling and melt diffusion of selenium and PPDC mixture powder. The characterization results showed that selenium with 47 % loading content were confined homogenously in the small pores (<4 nm) of the PPDC matrix. As a novel cathode material for rechargeable lithium batteries, Se/PPDC exhibited high specific capacity, good cycling stability, and C-rate performance when using sodium alginate (SA) as binder and low-cost LiPF6-EC-DEC as electrolyte. During the initial 30 cycles, a steady capacity of 650 mAh g−1 approaching to theoretic specific capacity was obtained at a current density of 150 mA g−1. At a high current density of 900 mA g−1, Se/PPDC delivered a reversible capacity of 410 mAh g−1 with nearly 100 % coulombic efficiency. The advanced electrochemical performance of Se/PPDC demonstrated that PPDC would be a promising porous carbon substrate to develop space-confined selenium cathode for rechargeable lithium batteries.

This work reports the synthesis, electrocatalytic performance and structure-dependent catalytic activity of Pt2Ni alloy@Pt core–shell nanoarchitectures (denoted as Pt2Ni alloy@Pt). The core–shell nanoarchitecture of Pt2Ni alloy@Pt catalyst is confirmed as consisting of a single concave-tetrahedral alloy nanocrystal core decorated with nanodendritic Pt particles. The oxygen reduction reaction (ORR) activity measurement indicates that the Pt2Ni alloy@Pt nanoarchitecture can enhance the ORR activity, accelerate the catalytic reaction and improve the durability of the catalyst during the electrocatalytic process. The atomic ratio between Pt and Ni is tuned to obtain various PtxNi1−x bimetallic nanostructures, and used for elucidation of structure dependence of catalytic activity. The resultant different PtxNi1−x catalysts exhibit considerable structure-dependent catalytic activity. The measurement results indicate that the order of ORR activity is as follows: cubic alloy nanocrystals (PtNi2) < cubic alloy crystal@Pt particles (PtNi2@Pt) < concave-tetrahedral alloy nanocrystals (Pt2Ni) < Pt2Ni alloy@Pt. Accordingly, the considerable ORR activity of Pt2Ni alloy@Pt catalyst is achieved by introducing an optimal amount of Ni atoms into PtxNi1−x catalyst and formulating the bimetallic crystal into a core–shell nanoarchitecture. In this integrated core–shell nanoarchitecture, the extended Pt nanoparticles shell provides high surface area, rich adsorption sites, and favorable surface permeability. Furthermore, the concave-tetrahedral alloy crystal core suppresses the activity loss derived from the agglomeration and/or corrosion of Pt active sites. Therefore, the two different components (alloy crystal core and extended Pt particles shell) contribute to different functions and further generate a synergistic effect towards ORR activity.

•S@rGO composite was synthesized via HI reduction and surfactant assisted chemical method.•The mechanism of HI reduction of GO with high conductivity is suggested.•980 mAh g−1 capacity is kept after 200 cycles charge/discharge process.•High C-rate current activation is used to prevent the shuttle of polysulfide ions.We developed hydrogen iodide (HI) reduction of rGO and surfactant-assisted chemical reaction- deposition method to form hybrid material of sulfur (S) encapsulated in reduced graphene oxide (rGO) sheets for rechargeable lithium batteries. The surfactant-assisted chemical reaction–deposition method strategy provides intimate contact between the S and graphene oxide. Chemical reduced rGO with high conductivity as carbon coating layer prevented the dissolution of polysulfide ions and improved the electron transfer. This novel core–shell structured S@rGO composites with high S content showed high reversible capacity, good discharge capacity retention and enhanced rate capability used as cathodes in rechargeable Li/S cells. We demonstrated here that an electrode prepared from a S@rGO with up to 85 wt% S maintains a stable discharge capacity of about 980 mAh g−1 at 0.05 C and 570 mAh g−1 at 1C after 200 cycles charge/discharge. These results emphasize the importance of rGO with high electrical conductivity after HI-reduced rGO homogeneously coating on the surface of S, therefore, effectively alleviating the shuttle phenomenon of polysulfides in organic electrolyte. Our surfactant-assisted chemical reaction-HI reduction approach should offer a new technique for the design and synthesis of battery electrodes based on highly conducting carbon materials.

Herein, the evolution of ZnO structures from hexagonal disk to prismoid, prism and pyramid was found via a facile two-step low temperature hydrothermal reaction, and the evolution was achieved by only adjusting the pH value of the reactive solution without the assistance of a template or a surfactant. The characterization results showed that the precursor (hexagonal Zn5(OH)8Cl2·2H2O disk) played a key role in the morphology evolution of ZnO during the early stage of the growth process and that the disks tended to stack together layer by layer in both directions (up and down) to form prismoid, prism and pyramid structures with the increase in pH value from 7 to 10. After calcination, the corresponding hexagonal ZnO microstructures were obtained. This structure evolution resulted in the weakening dominance of the (0001) plane in the total exposed crystal facets. Furthermore, despite the similar specific surface areas of the four hexagonal ZnO microstructures, the gas sensing properties of the sensors based on these microstructures deteriorated sequentially. At a working temperature of 330 °C, the ZnO disk with the most exposed (0001) plane showed the highest gas response toward ethanol, which was nearly 2, 3, and 6 times higher than those of the prismoid, prism and pyramid structures, respectively. This superior gas sensing performance strongly depends on the predominantly exposed polar facets (0001), which can provide more active sites for oxygen adsorption and subsequent reaction with the detected gas than other apolar facets. It demonstrates that the (0001) crystal facet plays a significant role in the gas sensing behavior of ZnO. This research will bring some inspiration to researchers for the fabrication of a high performance ZnO gas sensor as well as other metal oxides.

4,4′-Diaminodiphenyl sulfone functionalized SBA-15 (DDS/SBA-15) with various loading amounts of DDS has been prepared via a postsynthesis grafting method. The 2D hexagonal mesoporous structures of these hybrids have been confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption–desorption isotherms. The covalent grafting of DDS onto the SBA-15 was further confirmed by Fourier transform infrared spectroscopy (FT-IR). DDS/SBA-15 based quartz crystal microbalance (QCM) sensor shows good selectivity and quick response toward toluene vapor, and the detection limit is down to 20 ppb. Impedance spectroscopy measurements showed that the proton conductivity properties of DDS/SBA-15 depended on the loading amount of DDS. These hybrids demonstrated improved proton conductivities compared with pristine SBA-15, and a highest value of 2.26 × 10–4 S cm–1 has been observed when the DDS loading amount is 0.37 mmol g–1. Therefore, DDS/SBA-15 could serve as a promising candidate for both volatile organic compound (VOC) vapor sensing and proton conducting materials.

Mesoporous silica nanoparticles (MSNs) are a new class of carrier materials promising for drug/gene delivery and many other important applications. Stealth coatings are necessary to maintain their stability in complex media. Herein, a biomimetic polymer conjugate containing one ultralow fouling poly(carboxybetaine) (pCBMA) chain and one surface-adhesive catechol (DOPA) residue group was efficiently grafted to the outer surface of SBA-15 type MSNs using a convenient and robust method. The cytotoxicity of SBA-15-DOPA-pCBMAs was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results showed no significant decrease in cell viability at the tested concentration range. Macrophage cell uptake studies revealed that the uptake ratios of SBA-15-DOPA-pCBMAs were much lower than that of parent MSNs. Furthermore, inductively coupled plasma mass spectrometry (ICP-MS) analysis results showed that after SBA-15-DOPA-pCBMAs were conjugated with a targeting cyclo-[Arg-Gly-Asp-d-Tyr-Lys] (cRGD) peptide, uptake by bovine aortic endothelial cells (BAECs) was notably increased. Results indicated that cRGD-functionalized MSNs were able to selectively interact with cells expressing αvβ3 integrin. Thus, MSNs with DOPA-pCBMAs are promising as stealth multifunctional biocarriers for targeted drug delivery or diagnostics.

A Co3O4/reduced graphene oxide (rGO) composite was prepared by a convenient PVP (polyvinylpyrrolidone)-assisted method under reflux conditions. The prepared composite material consists of uniform Co3O4 nanoparticles (NPs about 100 nm), which are tightly enwrapped by rGO in the presence of PVP. This has been confirmed through observations by field emission scanning electron microscopy and transmission electron microscopy. The Co3O4/rGO composite exhibits superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, which is higher than that of the previously reported pure rGO and Co3O4 NPs. The anode was able to deliver a discharge capacity of 860 mA h g−1 during the 120th cycle at 40 mA g−1. The superior electrochemical performance of the Co3O4/rGO composite is attributed to its unique nanostructure, which closely combines the conductive graphene network with the uniformly dispersed Co3O4 NPs. X-ray absorption near-edge spectroscopy (XANES) was used to analyze the Co oxidation state of the Co3O4/rGO composite electrode.

A facile approach to the surface reduced graphene oxide (rGO) modification of micro-nano structured vanadium oxides composites are developed as cathode materials of lithium ions batteries (LIBs) and supercapacitors (SCPs) for the first time. The as-prepared V2O5–rGO and VO2–rGO composites exhibit remarkably enhanced cycling performance when being used as cathode materials in LIBs and SCPs, respectively. The uniform coating of graphene around the surface of vanadium oxides ensures good close electrical contact, therefore higher specific capacity and enhanced cycling performance than pure VO2 and V2O5 electrodes. Meanwhile, the cycling performance enhancement and capacity decay mechanism are presented, which is not only important to design electrode materials in LIBs and SCPs, but also extendable to the design and fabrication of other functional materials for energy storage and transfer systems.Graphical abstractHighlights► Vanadium oxides–rGO were synthesized at first time by hydrothermal reduction-heat treatment. ► Enhanced stable performance for Lithium-ion batteries and supercapacitors was obtained. ► The uniform coating of graphene ensures good close electrical contact and cycling performance.

Enhanced upconversion (UC) luminescence was obtained from a CaxYF3+2x host by doping with Yb3+/Er3+ or Yb3+/Tm3+. Lattice perturbation of YF3 by doping Ca2+ ions increased the energy transfer process between the absorbed Yb3+ ions and the activated Er3+ or Tm3+ ions, resulting in the emission of a bright multicolored UC luminescence.

A series of SnO2/V2O5 composites were designed and developed for selectively sensing BTEX (benzene, toluene, ethylbenzene, and xylol) based on a catalytic oxidation reaction. These composites were prepared with a facile solid phase reaction using sol–gel synthesized SnO2 and commercial V2O5 as raw materials. XRD and TEM were employed to characterize these composites. The results revealed forming process of the SnO2/V2O5 composites. Gas sensing tests of side-heating sensors showed that the SnO2/V2O5 composites had a much better response to BTEX rather than other VOCs such as ethanol, acetone, methanal, methanol and acetic acid compared with pure SnO2. Among these composites, the one containing 10 wt% V2O5 has the best selectivity and response (Ra/Rg) toward BTEX. At 270 °C, an optimal working temperature, the values of gas response to 50 ppm (parts per million) BTEX are more than 5 times, meanwhile the limit of detection is as low as 0.5 ppm. The influence of V2O5 on BTEX sensing of SnO2-based gas sensor was also discussed.

This paper employed a measurement of quartz crystal microbalance (QCM) to investigate the effects of mesopore structures and amount of organic loadings of fluoroalcohol derivatives/SBA-15 (a kind of ordered mesoporous silica sieve) hybrids on the sensing behavior of nerve agent simulant DMMP (dimethyl methylphosphonate). The meso-structure and functional groups of silica-based mesoporous hybrids were examined by SAXS, TEM, N2 adsorption–desorption isotherms and elemental analysis. The results show that much higher response value and sensitivity are achieved when the hybrid materials have relative higher pore volume and surface area. However, this effect only appears when the mesoporous hybrids have well-ordered porous structure, indicating that ordered meso-structure is critical in fabricating high-performance DMMP sensors. The reason is likely that the ordered meso-structure not only provides a larger number of contactable HFIP groups, but also facilitates molecules diffusion in porous structure. On the other hand, the specific interaction between HFIP/SBA-15 hybrids and DMMP vapor is greatly enhanced as the amount of fluoroalcohol derivatives increases. Therefore, the amount of organic functional groups incorporated plays an important role in determining the selectivity of sensors.

Two new mesoporous SBA-15/organic hybrids featuring fluoroalcohol and fluorinated-phenol derivatives were successfully synthesized via a co-condensation route. Hexafluorobisphenol and hexafluoroisopropanol were chosen to graft onto mesostructured silica, respectively. The as-synthesized hybrids preserve their mesoscopic structures with relative large surface areas and pore volume, as confirmed by SAXS, TEM and N2 adsorption–desorption porosimetry. Moreover, FT-IR and solid-state MAS NMR spectroscopy proved covalent anchoring of the organic functional groups onto the SBA-15. In order to confirm the potential application of the hybrids in gas sensing, investigations on the sensing properties toward the nerve agent simulant dimethyl methylphosphonate (DMMP) were carried out by QCM transducer. The QCM sensors based on hybrid materials exhibit excellent sensitivity toward trace DMMP vapour down to 26 ppb. In comparison with pristine SBA-15, the hybrids also show remarkably enhanced selectivity to DMMP due to suitable H-bonding interactions. Therefore, the well-defined mesoscopic porosity of the organic–inorganic hybrids together with the grafted fluoroalcohol and fluorinated-phenol derivatives lead to excellent sensing properties to DMMP vapour, and show great potential in the area of nerve agent detection.

Amine-functionalized SBA-15 with uniform morphology and well-defined mesostructure was prepared using a postgrafting route. The morphology, mesostructure, and functionality of the materials were characterized by scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering, nitrogen adsorption–desorption, Fourier transform infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy techniques. The results show that hexagonal lamelliform SBA-15 with a uniform particle size and short vertical channels plays two significant roles in uniformly dispersing amine-functionalizing groups and effectively adjusting the loadings of the functional groups within the mesopore channels. To confirm the potential application of the hybrids in gas sensors, using amine-functionalized SBA-15 as a sensing material and a quartz crystal microbalance as a transducer, a parts per billion level formaldehyde sensor with high sensitivity (response time about 11 s, recovery time about 15 s) and good chemoselectivity was achieved. This material holds great potential in the area of rapid, sensitive, and highly convenient formaldehyde detection.

Thiol-functionalized SBA-15 mesoporous silica materials with various pore sizes and specific surface areas were prepared by using a post-grafting process. All the obtained materials were characterized by SAXS, FT-IR, TGA, TEM and N2 adsorption isotherms. By using these functionalized mesoporous silica as sensing materials, the QCM sensor was constructed and used for detecting heavy metal ions. The experimental results indicated that the QCM sensor can detect 1 ppm Hg2+ with the response frequency of 175 Hz in the response time of 1 min. The influence of response time, the amount of thiol groups, pore size and specific surface area of SBA-15 mesoporous silica on Hg2+ detection was studied systematically in this paper.

Micro–nanosized vanadium pentoxide (V2O5) was synthesized by hydrothermal reduction of amorphous V2O5, followed by thermal treatment in air atmosphere. Pyrrole was in-situ polymerization on the surface of V2O5 to obtain V2O5@PPy hybrid material.The as-synthesized V2O5 with about 100 nm in diameter and several hundreds nanometers in length were obtained and PPy layer with about 100 nm in thickness coated on the surface of V2O5. Electrochemical measurement showed that V2O5@PPy hybrid material had improved lithium storage ability and cycling performance compared with pure V2O5. PPy modification supplied a new route to obtain V2O5 hybrid cathode with significantly improved cyclic performance and showed promising applications in recharged lithium batteries.

Ordered mesoporous carbon (OMC) supported nanosized Pt and PtCo alloy electrocatalysts were synthesized by ethylene glycol hydrothermal reduction route and their electrochemical oxidation activity toward several typical small organic molecules (SOMs) was investigated. Structural characterization revealed that Pt and PtCo nanoparticles with mean diameter of 3–4 nm were well dispersed on OMC (BET specific surface of 2220 cm2/g). Electrochemical measurements confirmed that electrochemical oxidation behaviors of SOMs on synthesized Pt/OMC and PtCo/OMC catalysts were complicated and the carbon chain length of SOMs and the intermediates, especially COads oxidation behaviors on Pt active sites are two main factors which affect the SOMs oxidation.Highlights► Ordered mesoporous carbon supported Pt and PtCo bimetal composites were synthesized. ► Electrochemical oxidation activity toward small organic molecules were investigated. ► Electro-oxidation is related to the chain length of SOMs and their intermediates.

Ir(ppy)2(VPHD) (ppy=2-phenyl pyridine, VPHD=6-(4-vinylphenyl)-2,4-hexanedione) was copolymerized with methyl methacrylate (MMA). The copolymer had high quantum yield of 52.3±0.5% in dilute ethyl acetate solution, and the yield increased around 45% than that of the iridium monomer. The maximum emission peaks for the copolymers shifted from 515 to 489 nm while the iridium complex content was less than 0.005 mol% in the feed. The blue emission at 489 nm and the green emission at 520 nm were analyzed by Lorenz function. They are attributed to 1MLCT and 3MLCT emissions, respectively.Highlights► PMMA-Ir(ppy)2(VPHD) as luminescent material with high yield of 53%.► The blue color emission at 489 nm from 1MLCT in conformity with Lorenz function.► The quantum yield for the copolymer increases 45% than that of the iridium monomer.► The 3MLCT Ex. intensity versus the monomer concentration is in conformity with Boltzmann function.

Vapor phase treatment with tetraethyl orthosilicate (TEOS) is used to improve the performance of methylated mesoporous silica films spin-coated on silicon wafers. Subsequent calcination leads to formation of ultra low dielectric-constant (k) films with high hydrophobicity and structural stability. The k value of the films is about 1.75, and remains as low as 1.82 in an 80%-relative-humidity environment over seven days. Mechanical strength (elastic modulus and hardness) is high enough to withstand the stresses that occur during the chemical mechanical polishing and wire bonding process (E = 10.9 GPa). Effects of the methyl group and TEOS vapor treatment on the structural stability and hydrophobicity are systematically studied.Highlights• Ultra low-k films • High hydrophobicity and structural stability. • Vapor phase treatment.

Ferrocene (Fc) was encapsulated in the cavities of a NaY zeolite by vapor diffusion via sublimation at below 100 °C. The resulting Fc@NaY zeolite composite was investigated by power X-ray diffraction, diffuse reflectance UV–vis and FT-IR spectroscopy, and by cyclic voltammetry. The results indicated that Fc was encapsulated into the zeolite whose microporous structure had remained intact. The Fc in the silica matrix had retained its electroactivity and did not leach out. A glucose biosensor was obtained by immobilization of the modified zeolite and glucose oxidase on a carbon paste electrode. It displays a linear response to glucose (from 0.8 μM to 4.0 mM), a detection limit of 0.2 μM, and a response time of 4 s. The good performance of the biosensor is ascribed to the biocompatibility of the zeolite and presence of Fc which facilitates the electron transfer from the enzyme to the surface of the electrode.

Copper(I) bromide (CuBr) was considered to be a good gas sensing material with a high sensitivity and selectivity to ammonia (NH3) at ambient temperature. The NH3 sensing mechanism was generally considered to be a result of the strong interaction between NH3 molecules and Cu+ ions. When CuBr-coated quartz-crystal microbalance (QCM), a typical gravimetric transducer, was exposed to NH3, the device displayed a decrease rather than an increase in total mass. This was an unusual phenomenon. In situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) was employed to examine the reasons of this total mass decrease. Probing of species formed on the CuBr surface revealed that a complex form between the Cu+ ions and the O2 molecules in air existed. Consequently, O2 gas with a higher molecular weight than NH3 was substituted by NH3 gas, inducing the decrease in mass. The band at 1123 cm−1 of the DRIFT spectrum of CuBr corresponding to the complex formed between O2 molecules and Cu+ ions was identified. The intensity of this band which decreased with the formation of NH3 complex was also observed. The observation was a result of the substitution process for O2 adsorption instead of NH3.

Undoped SnO2 and porous Al2O3 powders were obtained through a simple chemical precipitation process. SnO2-based gas sensing materials and Al2O3 catalytic coating loaded with a noble metal were prepared by impregnation. The SnO2 and Al2O3 powders were characterized by TEM, SEM, nitrogen adsorption–desorption experiment, FT-IR and in situ XRD. Gas responses of the SnO2-based gas sensors were measured in a static state. The experimental results indicated that the response towards R134a of the SnO2-based gas sensor can be significantly enhanced by loading noble metal and using catalytic coating. The sensor based on a double layer film SnO2 (Au)/Al2O3 (Au) showed satisfactory results including large response, good selectivity, high long-term stability, fast response and recovery, revealing its potential application in the detection of refrigerants and the maintenance of air condition systems. Finally, a gas sensing mechanism for R134a is suggested and proved by bond energy data, FT-IR spectrum and in situ XRD.

Nanocrystalline tin dioxide (SnO2) materials with very interesting architectures (well-defined pores, hierarchical pores) were synthesized by a suitable heat treatment of SnO2/phenol formaldehyde resin (PFR) nanocomposite. The composite was obtained through a facile hydrothermal approach by using tin(IV) tetrachloride pentahydrate (SnCl4·5H2O) as a raw material, hexamethylenetetramine (HMT) as a pore-forming agent and monomer (HCHO) source for polymerization with phenol. Compared with the fine porous SnO2 sensor, the hierarchical porous SnO2 sensor showed a higher response. Owing to the hierarchical porous structure, the as-prepared materials exhibit satisfactory selectivity to chlorine along with high-sensitivity (249.3 at 10 ppm), fast response (7 s), very short recovery time (15 s), long-term stability as well as low power. The excellent sensing performance was discussed concerning the architectures of the materials.

SnO2 nanowires with an average 0.6 μm in length and about 25 nm in diameter were prepared by a hydrothermal method. The sensors were fabricated using SnO2 nanowires assembled with Pd nanocrystals. The sensing properties of the sensors such as selectivity, response–recovery time and stability were tested at 290 °C. After assembling Pd nanocrystals onto the surface of SnO2 nanowires, the gas sensing properties of the sensors toward H2S were improved. The sensors based on Pd nanoparticle@SnO2 nanowires exhibit high stability owing to stable single crystal structure. The mechanism of promoting sensing properties with Pd nanoparticles is discussed.

A facile photochemical method was used to synthesize Ag nanoparticle (Ag NP) embedded-ZnO nanorods in this article. The as-synthesized Ag NP embedded-ZnO nanorod samples were characterized systematically by TEM, XPS, DSC, XRD and SEM. The characterization results confirmed that Ag NPs had been embedded in ZnO nanorods. The gas-sensing properties of Ag NP embedded-ZnO nanorods were also investigated. While the performances of the sensors can be enhanced by embedding Ag NPs onto the surfaces of ZnO nanorods, the response of Ag NP embedded-ZnO nanorod sensors to 50 ppm ethanol is almost three times as high as that of those made from pure-ZnO nanorods. The responses of the sensors have no apparent degradation after being exposed to ethanol of 30 ppm for 100 days. Our Ag NP embedded-ZnO nanorod sensors have long-term stability and exhibit highly enhanced gas-sensing performances in their response and selectivity for detecting ethanol vapor.

A novel mesoporous silica SBA-15 with monodisperse hexagonal lamelliform was prepared, and deposited on the quartz crystal microbalances (QCMs) to construct highly stable and sensitive humidity sensors. The humidity sensing characteristics of the sensors were investigated by measuring the resonant frequency shift of QCMs due to the additional mass loading caused by adsorption of water. X-ray diffraction, nitrogen adsorption/desorption, transmission electron microscopy and field emission scanning electron microscopy were employed to characterize these sensing materials. The results showed that the sensors had high sensitivity, good stability, short response/recovery time, well reproducibility and narrow hysteresis. Herein, not only a novel and low-cost humidity sensor material was exploited, but also a new application area for mesoporous materials was opened up.

An ordered mesoporous carbon material functionalized with carboxylic acid groups was synthesized. It was characterized by powder X-ray diffraction, transmission electron microscopy, Fourier transform IR spectroscopy and N2 adsorption/desorption. Furthermore, this material was used to modify an electrode surface combined with a hydrophobic ionic liquid. The functionalized ordered mesoporous carbon/ionic liquid gel modified electrode shows excellent electrocatalytic performances for the oxidation of dopamine, uric acid and ascorbic acid. The presence of the ionic liquid promotes the electron transfer. Linear responses for dopamine and uric acid were obtained in the ranges of 0.1 to 500 μM and from 0.1 to 100 μM with detection limits of 4.1 and 2.5 nM (signal-to-noise ratio of 3), respectively, under optimum conditions. A quick and sensitive biosensor based on functionalized ordered mesoporous carbon and an ionic liquid has been developed for the first time for the detection of dopamine and uric acid in the presence of a large amount of ascorbic acid.

A novel photocatalysis and gas sensing material was synthesized by decorating Au nanoparticles on tungsten trioxide nanorods. Tungsten trioxide nanorods were prepared through the ion-exchange method combined with hydrothermal treatment and further modified with Au nanoparticles (Au NPs). After Au NPs decorated on the surface of WO3 nanorods (WO3 NRs), the reducing gas (hydrogen, methanol, ethanol, etc.) sensing properties and the photocatalytic performance of rhodamine B (RhB) were all greatly improved. Au NP modified WO3 nanorods (Au NP@WO3 NRs) exhibit not only larger response (H2 50 ppm, recovery time lower than 10 s) and better selectivity (Ra/Rg = 6.6) for H2 gas detection than pure WO3 NRs but also high photocatalytic properties for the absolute degradation of RhB under simulated sunlight irradiation for 120 min.

Single-crystalline ZnO nanowires were synthesized, and further modified with Pd nanoparticles through self-assemblies. The self-assembly strategy shows advantages of tailoring the surface modification of ZnO nanowires with monodispersed Pd nanoparticles and further tuning of the functionalities of nano-architectures. It was found that poly(vinylpyrrolidone) (PVP) plays a key role in loading Pd nanoparticles onto the surfaces of ZnO nanowires. Having been turned into chemical sensors, the nano-architectures constructed from ZnO nanowires and Pd nanoparticles exhibit a highly enhanced response to H2S gas, compared to the devices from pure ZnO nanowires.

The LiV3O8 samples with different morphologies have been successfully prepared by a mixed hydrothermal–sol–solid-state route via the reaction of vanadium pentoxide(V2O5) and lithium hydrate(LiOH) at 200 °C in basic medium and subsequent gelation at 100 °C and thermal treatment at 300–550 °C. The crystal structure and morphology of the samples were characterized by X-ray diffraction (XRD), specific surface area measurements and scanning electron microscopy (SEM). Their electrochemical properties were investigated by means of constant charge/discharge cycling measurement. The results indicated that the calcination temperature has a significant effect on the crystal structure, morphology, and specific surface area of the LiV3O8 samples, which consequently affects their electrochemical performance such as the initial capacity and the cycleability. The sample heat-treated at 300 °C shows the morphology of irregular blocks with low degree of crystallinity and high specific surface area, exhibiting high initial discharge capacity of 277.7 mAh g−1 but a fast capacity fade. In contrast, the samples annealed at higher temperature with perfectly uniform rod-like morphology show much better cycle performance.

In this paper, a controlled synthesis of rod and hollow sphere SnO2 nanostructures has been realized via a solvothermal reaction, without employing any other toxic organic solvents. The well-defined morphologies are obtained by simply adding sodium hydroxide to aqueous ethanol solution. The products are characterized by XRD, TEM and SEM. Growth mechanisms for these two nanostructures were proposed. Gas sensors were fabricated and an investigation into the structure-based gas-sensing properties has been conducted. Compared with SnO2 hollow spheres, the nanorods display much better gas sensing properties, which is mainly due to their facile electrons transportation and excellent thermal stability.

Brush-like hierarchical ZnO nanostructures assembled from initial 1D ZnO nanostructures were prepared from sequential nucleation and growth following a hydrothermal process. The morphology, structure, and optical property of hierarchical ZnO nanostructures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) studies. The FE-SEM images showed that the brush-like hierarchical ZnO nanostructures are composed of 6-fold nanorod-arrays grown on the side surface of core nanowires. Compared with ZnO nanowires, brush-like hierarchical ZnO nanostructures easily fabricated satisfactory ethanol sensors. The main advantages of these sensors are featured in excellent selectivity, fast response (less than 10 s), high response (sensitivity), and low detection limit (with detectable ethanol concentration in ppm).

Single-crystal, metastable, hexagonal In2O3(H-In2O3) nanorods were synthesized by annealing InOOH nanorods (prepared by solvothermal method) at 600 °C under ambient pressure. The samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and their gas sensitivities are detected. The gas sensitivity results show that hexagonal In2O3 nanorods are very sensitive to dilute ethanol vapor.

Uniform ZnO nanorods were synthesized in high-yield by using metal zinc powder as zinc source via a one-step facile hydrothermal process under mild conditions, in which cetyltrimethylammonium bromide (CTAB) with ordered chain structures acted as the conversion of Zn powder into ZnO nanorods. The characterization results show that the as-synthesized products were structurally uniform and have diameters of 40–80 nm. Gas sensing properties studies show that ZnO nanorods exhibit more excellent response and stability to ethanol than that of ZnO nanoparticles. After working continuously for 50 days, the sensitivity of ZnO nanorods still retained 7.3, whereas, the ZnO nanoparticles showed only 1.0. The facile preparation method and the improved properties derived from typical rods-like nanostructure are significant for the future applications of gas sensing material.

Nanosized ZnO powder was synthesized by using a chemical precipitation method, and loaded with different dopants through impregnation. The as-prepared ZnO powder was characterized by XRD and TEM. The characterization results show that the as-prepared sample is wurtzite polycrystalline ZnO, the mean grain size is 30–40 nm, and there are three types of adsorbed oxygen (O2−, O22−, and O2−) on the surface of the sample. The as-prepared ZnO powder shows excellent gas responses to alcohol and acetaldehyde, but no response to ethene. The sensing mechanism of ZnO was further studied with the help of gas chromatography (GC) associated with a fixed-bed reactor. The studies show that acetaldehyde, carbon dioxide and water are the only oxidation products of C2H5OH over ZnO. The gas response to C2H5OH is strongly dependent on the conversion ratio of C2H5OH to acetaldehyde. In addition, among all the dopants tested, Ru is the optimal dopant which can increase the response to C2H5OH, but cannot increase the conversion ratio of C2H5OH to acetaldehyde. Thus we suggest that the gas sensing mechanism of ZnO to C2H5OH is the mode controlled by chemisorption of negatively charged oxygen, and the sensitizing role of Ru in the ZnO sensor belongs to the electronic sensitization mechanism.

A liquefied petroleum gas (LPG) sensor with high selectivity, sensitivity and low power consumption has been developed based on indium oxide with very low resistance. Nanocrystalline In2O3 gas sensing materials were directly synthesized through a one-step controllable solvothermal process at 210°C for 24 h, using InCl3·4H2O as the starting material, cetyltrimethyl ammonium bromide (CTAB) as additive and ethanol as the solvent. The obtained samples were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that indium oxide takes on uniform cubic shape with range size of 10∼30 nm and fine dispersivity. Gas sensitivity was measured in a mixing static gas. The results indicated that 3.0 V is the best working voltage of the sensor to LPG. Sensitivity is 12.6. The response-time and recovery-time are 3 s and 10 s respectively. Power consumption is only around 200 mW.

A series of recent terrorist attacks makes it clear that developing chemical sensors for chemical warfare agents with rapid response, high sensitivity and stability is essential. Nerve agent sarin (2-(fluoro-methyl-phosphoryl)oxypropane) is a typical member of organophosphorus compounds, which are recognized as one of the most toxic warfare agents. Considering sarin’s high toxicity, DMMP (dimethyl methylphosphonate) is widely used as its simulant in the laboratory because of its similar chemical structure and much lower toxicity. This review serves to introduce the development of a variety of chemical sensors applied to the detection of DMMP in recent years, including mass-sensitive sensors, chemicapacitors, chemiresistors, as well as field-effect transistors. Meanwhile, the research and applications of mass-sensitive and resistance based DMMP sensors are highlighted. For sorption-based sensors, active materials play crucial roles in improving integral performances of sensors. The novel active materials pertaining hydrogen-bond acidic polymers, metal oxides, carbon nanotubes, porous materials and graphene is focused on in this review.

This work reports the synthesis, electrocatalytic performance and structure-dependent catalytic activity of Pt2Ni alloy@Pt core–shell nanoarchitectures (denoted as Pt2Ni alloy@Pt). The core–shell nanoarchitecture of Pt2Ni alloy@Pt catalyst is confirmed as consisting of a single concave-tetrahedral alloy nanocrystal core decorated with nanodendritic Pt particles. The oxygen reduction reaction (ORR) activity measurement indicates that the Pt2Ni alloy@Pt nanoarchitecture can enhance the ORR activity, accelerate the catalytic reaction and improve the durability of the catalyst during the electrocatalytic process. The atomic ratio between Pt and Ni is tuned to obtain various PtxNi1−x bimetallic nanostructures, and used for elucidation of structure dependence of catalytic activity. The resultant different PtxNi1−x catalysts exhibit considerable structure-dependent catalytic activity. The measurement results indicate that the order of ORR activity is as follows: cubic alloy nanocrystals (PtNi2) < cubic alloy crystal@Pt particles (PtNi2@Pt) < concave-tetrahedral alloy nanocrystals (Pt2Ni) < Pt2Ni alloy@Pt. Accordingly, the considerable ORR activity of Pt2Ni alloy@Pt catalyst is achieved by introducing an optimal amount of Ni atoms into PtxNi1−x catalyst and formulating the bimetallic crystal into a core–shell nanoarchitecture. In this integrated core–shell nanoarchitecture, the extended Pt nanoparticles shell provides high surface area, rich adsorption sites, and favorable surface permeability. Furthermore, the concave-tetrahedral alloy crystal core suppresses the activity loss derived from the agglomeration and/or corrosion of Pt active sites. Therefore, the two different components (alloy crystal core and extended Pt particles shell) contribute to different functions and further generate a synergistic effect towards ORR activity.

Two-dimensional (2D) nanomaterials show great potential for electrocatalysis or other applications that require large surface area. In this work, we developed porous zinc–cobalt layered double hydroxide (Zn–Co-LDH) nanosheets by using a one-step microwave-assisted approach, and examine their oxygen evolution reaction (OER) performance. The Zn–Co-LDH nanosheets with a high specific surface area of 116.4 m2 g−1 exhibit good OER activity, expressed as low onset overpotential, small Tafel slope and large exchange current density. At the overpotential of 0.54 V, the current density of Zn–Co-LDH nanosheets is about 15.06 mA cm−2, which is much higher than that of Zn–Co-LDH nanoparticles. The comparable electrocatalytic performance may be attributed to the porous 2D structure generating more active sites and higher electronic conductivity. Furthermore, the obtained Zn–Co-LDH nanosheets show good stability during long time running at 1.55 V vs. RHE. Accordingly, an effective OER catalyst is exploited by using a simple microwave-assisted synthesis. Such an effective method could be extended to large-scale synthesis of uniform and stable 2D LDH nanomaterials.

A two-dimensional porous framework SHU-1 could undergo solvent-induced structural transformations to SHU-1a in methanol and SHU-1b in water. SHU-1, SHU-1a and SHU-1b showed selective adsorption towards malachite green.

A Co3O4/reduced graphene oxide (rGO) composite was prepared by a convenient PVP (polyvinylpyrrolidone)-assisted method under reflux conditions. The prepared composite material consists of uniform Co3O4 nanoparticles (NPs about 100 nm), which are tightly enwrapped by rGO in the presence of PVP. This has been confirmed through observations by field emission scanning electron microscopy and transmission electron microscopy. The Co3O4/rGO composite exhibits superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, which is higher than that of the previously reported pure rGO and Co3O4 NPs. The anode was able to deliver a discharge capacity of 860 mA h g−1 during the 120th cycle at 40 mA g−1. The superior electrochemical performance of the Co3O4/rGO composite is attributed to its unique nanostructure, which closely combines the conductive graphene network with the uniformly dispersed Co3O4 NPs. X-ray absorption near-edge spectroscopy (XANES) was used to analyze the Co oxidation state of the Co3O4/rGO composite electrode.

Single-crystalline ZnO nanowires were synthesized, and further modified with Pd nanoparticles through self-assemblies. The self-assembly strategy shows advantages of tailoring the surface modification of ZnO nanowires with monodispersed Pd nanoparticles and further tuning of the functionalities of nano-architectures. It was found that poly(vinylpyrrolidone) (PVP) plays a key role in loading Pd nanoparticles onto the surfaces of ZnO nanowires. Having been turned into chemical sensors, the nano-architectures constructed from ZnO nanowires and Pd nanoparticles exhibit a highly enhanced response to H2S gas, compared to the devices from pure ZnO nanowires.

Two new mesoporous SBA-15/organic hybrids featuring fluoroalcohol and fluorinated-phenol derivatives were successfully synthesized via a co-condensation route. Hexafluorobisphenol and hexafluoroisopropanol were chosen to graft onto mesostructured silica, respectively. The as-synthesized hybrids preserve their mesoscopic structures with relative large surface areas and pore volume, as confirmed by SAXS, TEM and N2 adsorption–desorption porosimetry. Moreover, FT-IR and solid-state MAS NMR spectroscopy proved covalent anchoring of the organic functional groups onto the SBA-15. In order to confirm the potential application of the hybrids in gas sensing, investigations on the sensing properties toward the nerve agent simulant dimethyl methylphosphonate (DMMP) were carried out by QCM transducer. The QCM sensors based on hybrid materials exhibit excellent sensitivity toward trace DMMP vapour down to 26 ppb. In comparison with pristine SBA-15, the hybrids also show remarkably enhanced selectivity to DMMP due to suitable H-bonding interactions. Therefore, the well-defined mesoscopic porosity of the organic–inorganic hybrids together with the grafted fluoroalcohol and fluorinated-phenol derivatives lead to excellent sensing properties to DMMP vapour, and show great potential in the area of nerve agent detection.

Heterojunction structured MASnI3/TiO2 photocatalysts (MA represents CH3NH3+) are prepared via a facile wet-chemical method and characterized by various techniques. The characterization demonstrates the formation of a heterojunction structure and the good crystallinity of MASnI3/TiO2 (1:9) (mass ratio of MASnI3 and TiO2 is 1:9). Moreover, the results also display the improved visible light absorption of MASnI3/TiO2 (1:9) and low recombination of photoinduced carriers. As a result, MASnI3/TiO2 (1:9) could completely degrade rhodamine B (97%) in 40 min, which has higher photocatalytic ability than pure MASnI3 and pure TiO2. The improved photocatalytic activity could be ascribed to the improved light harvesting ability and easy transfer of photogenerated carriers of the materials generated by the formation of a heterojunction structure and the suitable energy band position between MASnI3 and TiO2. In particular, coupling of MASnI3 and TiO2 could also avoid oxidation and hydrolysis of MASnI3 so that the long-term stability of the composite could be efficiently maintained. It is the first report on MASnI3 and TiO2 composites being used as photocatalysts for dye degradation. A possible mechanism for the enhancement of photocatalytic activity under light irradiation is also proposed.