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High concentration ozone can damage greatly to the respiratory, cardiovascular systems, and fertility of people, and catalytic decomposition is an important strategy to reduce its harm. However, it remains a challenge to develop efficient ozone decomposition catalysts with high efficiency. In this study, p- and n-type silicon nanowires (Si NWs) are fabricated by wet chemical etching method and are firstly applied to catalytic decompose ozone at room temperature. The p-type Si NWs exhibit 90% ozone (20 ppm O3/air) decomposition efficiency with great stability, which is much better than that of n-type Si NWs (50%) with same crystal orientation, similar diameter and specific surface area. The catalytic property difference is mainly attributed to the more delocalization holes in the p-type Si NWs, which can accelerate the desorption of ozone decomposition intermediates (i.e., adsorbed oxygen species).

The leaching recovery of gold is low caused by the arsenic inclusion and gold encapsulation in the two-stage roasting pyrite cinder. It is necessary to pretreat the cinder to improve the recovery of gold. In this study, sulfuric acid was employed to remove arsenic and iron from the cinder, and then the arsenic was transferred to precipitates from the leaching solution by ferric ion precipitation for harmless disposal. The vast majority of the arsenic and iron were leached into the solution at 80 °C under atmospheric pressure. The recovery rate of gold in residue after non-cyanide extraction was greatly improved, and the gold content in residue decreased from 11.2 g/t to 3.8 g/t. The leached iron was partly precipitated by controlling the additive amount of hydrogen peroxide and pH value to precipitate the arsenic. The arsenic concentration in the solution was reduced to about 5 mg/L after 1 h of precipitation. The size of the precipitates was increased to >100 μm when the pH value was >5.69. In addition, the precipitates had a strong adsorption capacity to absorb many other impurity ions such as ammonium. This study indicates that the removal of arsenic and iron from cinder is beneficial to increase the recovery of gold, and it is effective to remove the arsenic from the leaching solution through co-precipitation with ferric ion.

Porous fibrous mullite ceramic membranes with different content of fibers were successfully fabricated by molding method for dust removal. The properties of the samples, such as microstructure, porosity, bulk density and mechanical behavior were analyzed. Owing to the highly porous three-dimensional structure of ceramic membranes, all the samples exhibited low density (lower than 0.64 g/cm3), high porosity (higher than 73%), low linear shrinkage (lower than 1.0%) and low thermal conductivity (lower than 0.165 W/mK). Significantly, the as-prepared porous ceramic membrane possessed of enhanced dust removal efficiency with almost 100% for 3–10 µm, 97% for 1.0 µm, 87% for 0.5 µm and 82% for 0.3 µm dust particles in diameter from dust-laden air passed through the test module. Moreover, the pressure drop was lower than 80 Pa when the airflow linear velocity reached 1.25 m min−1. The results indicated that the ceramic membranes prepared in this work were promising high efficiency dedusting materials for the application in gas filtration field.

Because of the inevitable Fermi level pinning on surface/interface states of nanowires, achieving high-performance nanowire devices with controllable nanoscale contacts is always challenging but im...

Nanostructure-derived interfacial effect plays a great role in enhancing catalytic activities. Herein, a MnO 2 nanowires@NiO nanosheets core-shell hybrid nanostructure was successfully prepared by uniformly decorating NiO nanosheets on the one-dimensional MnO 2 nanowires. The physi-chemical properties of the MnO 2 and MnO 2 @NiO were characterized by using XRD, BET, SEM, H 2 -TPR and XPS techniques. Compared to the single MnO 2 nanowires, the MnO 2 @NiO nanocomposite with better low-temperature reducibility and more active surface oxygen species exhibited much better performance in complete oxidation of benzene, giving the temperatures for 100% benzene conversion of 320 °C under the conditions of 1000 ppm benzene in air and space velocity of 120,000 mL g −1 h −1 while the value over pure MnO 2 was 380 °C. The novel hetero-interface constructed between MnO 2 and NiO core-shell nanostructures might make a great contribution on this significantly promoting effect.

Nowadays, xylene is not only one major air pollutant which threats human health even if its concentration is lower than the human olfactory threshold of 470 ppb, but also one of the typical gases exhaled by the lung cancer patients with a criterion of 10–20 ppb. However, in situ detection of the ppb-level xylene for air quality monitoring and breath analysis remains challenging using the easily fabricated and low cost metal oxide semiconductor gas sensors. Herein, a synergetic p+n field effect transistor (FET) amplification circuit is designed to detect the ppb level xylene. By optimizing the load resistor ( $R_{L}$ ) and the p- and n-FET coupling effect, a magnification factor (~7.5) is obtained. This amplification circuit decreases the detection limit of TGS2602 sensor to ~10 ppb xylene with apparent response of about 2.3 and voltage change of >0.5 V, promising for air quality monitoring (the highest permissive limit of 42 ppb) and breath disease analysis (threshold of lung cancer 10–20 ppb). The mechanism is that the matched couple of p + n FETs work synchronically when their ( $R_{\mathrm {L}} + R_{\mathrm {FET}}) - I$ curves nearly coincide with each other. All those results show the prospect of ppb level gas detection with MOX sensors using the synergetic p+n FET amplification circuit.

The synthesis of effective and recyclable Fenton-like catalyst is still a key factor for advanced oxidation processes. Herein, magnetic porous Fe3O4/carbon octahedra were constructed by a two-step controlled calcination of iron-based metal organic framework. The porous octahedra were assembled by interpenetrated Fe3O4 nanoparticles coated with graphitic carbon layer, offering abundant mesoporous channels for the solid-liquid contact. Moreover, the oxygen-containing functional groups on the surface of graphitic carbon endow the catalysts with hydrophilic nature and well-dispersion into water. The porous Fe3O4/carbon octahedra show efficiently heterogeneous Fenton-like reactions for decomposing the organic dye methylene blue (MB) with the help of H2O2, and nearly 100% removal efficiency within 60 min. Furthermore, the magnetic catalyst retains the activity after ten cycles and can be easily separated by external magnetic field, indicating the long-term catalytic durability and recyclability. The good Fenton-like catalytic performance of the as-synthesized Fe3O4/carbon octahedra is ascribed to the unique mesoporous structure derived from MOF-framework, as well as the sacrificial role and stabilizing effect of graphitic carbon layer. This work provides a facile strategy for the controllable synthesis of integrated porous octahedral structure with graphitic carbon layer, and thereby the catalyst holds significant potential for wastewater treatment.

Mercaptans are highly volatile compounds responsible for disagreeable odors and very low olfactory threshold, especially for CH3SH (0.4 ppvb). To the best knowledge of us, approach for controlling low-concentrated odors (i.e. 1-10 ppm) is scarcely reported. In this research, Cu-doped mesoporous silica was synthesized for removal of low-concentrated CH3SH. The as-prepared samples show considerably thermal and mechanical stability and could be thermal-regenerated. Copper loading ratio and humidity have significant impacts on eliminating odors. According to XRD, TEM, BET, NMR and EPR, we deduce that surface groups on CuO nanoparticles and the SiOCu group are highly possibly transformed into a hydrated complex which is much more effective in capturing CH3SH with its empty Cu-3d orbit. Although CH3SH has to compete with water for absorption sites, it is always the "winner" owing to the strong chelating ability between SH group and Cu (Ⅱ).

To enhance the electrical and mechanical properties of silicone rubber (SIR) in the field of high-voltage insulation, conventional fillers such as aluminum hydroxide (ATH), fumed silica and precipitated silica have been used for many years. In this work, SIR composites filled with ATH, irregular SiO 2 (IS) and sphere SiO 2 (SS) were prepared by mechanical blending, and the effects of filler type and filler shape on mechanical, electrical and thermal properties of SIR composites were systematically investigated. Compared with ATH-SIR composites, SS-SIR composite exhibited better electrical and mechanical properties. It showed that the tensile strength of SS-SIR composites was up to 6.6 MPa, which was nearly 2-folded compared to ATH-SIR composite. According to the loss tangent results in combination with tensile fracture surface observation, the interfacial interaction between SiO 2 fillers and SIR is stronger than that between ATH and SIR, and the dispersion is better in SiO 2 fillers filled SIR composites than that in ATH filled composite. The breakdown strength of ATH-SIR composite is only 18.9 kV mm −1 , while those of IS-SIR and SS-SIR composites are 24.9 and 24.8 kV mm −1 , respectively. Among the three SIR composites, SS-SIR composite has lowest dielectric permittivity and dielectric loss. Compared with ATH-SIR composite, the SiO 2 fillers filled SIR composites have the lower thermal conductivity ranging from 30 °C to 150 °C, but they exhibit the better arc aging resistance due to the good thermal stability and thermal conducting property at high temperature. Moreover, the SS-SIR composite exhibits the better arc aging resistance than IS-SIR composite.

High performance methane gas sensors have become more and more essential in different fields such as coal mining, kitchens and industrial production, which necessitates the design and synthesis of highly sensitive materials. Herein, mesoporous SnO2 hollow spheres with high surface area (>90 m2 g−1) are prepared by a progressive inward crystallization routine, showing a high response of 1.31 to 250 ppm CH4 at a working temperature of 400 °C. Furthermore, loading noble metal Pd onto the surface of SnO2 hollow spheres by an adsorption–calcination process improves the response to 4.88 (250 ppm CH4) at the optimal dosage of 1 wt% Pd. Meanwhile, the working temperature decreases to 300 °C, showing the prominent spillover effect of catalytic Pd and PdO–SnO2 heterostructure sensitization as evidenced by the binding energy shift in the X-ray photoelectron spectroscopy (XPS) analysis. The response/recovery time is as short as 3/7 s and the sensitivity is stable for a test period as long as 15 weeks. All these performances show the promise of the highly porous Pd-loaded SnO2 hollow spheres for high performance methane sensors.

Various Cu-based composites for catalytic ozone decomposition have been synthesized by the reduction of Cu2+ using NH2OH·HCl in an aqueous solution without the addition of any extra etching agent. A Cu2O–CuO heterogeneous composite with many nanometer-sized CuO nanoplates distributed on the Cu2O surface as well as Cu(OH)2 nanowires was fabricated, and the structural evolution process was explored. The mechanism for the structure's formation can be attributed to the synergistic reaction of oxidation etching and acidic etching. It was found that the surface morphology and chemical composition of the nanostructures play important roles in catalyzing ozone decomposition. The Cu2O–CuO–Cu(OH)2 hierarchical nanostructure exhibits a 100% ozone (20 ppm O3 per air) decomposition efficiency at room temperature after 30 h of continuous operation, showing high stability. In addition, the hierarchical nanostructure also shows high moisture resistance, and the ozone conversion can still be above 80% at high relative humidity levels (ca. 90%) after a 16 h test. The excellent performance can be attributed to the delocalized holes speculated by EPR spectroscopy, which may facilitate the necessary electron transfer between intermediate oxygen anions and the catalytic surface.

Advanced integrated nanoarray (NA) catalysts have been designed by growing metal-doped Co3O4 arrays on nickel foam with robust adhesion. Ternary MCo2O4 NA catalysts were prepared by doping urchin-like Co3O4 with different transition metals (Cu2+, Mn2+, Fe2+, Ni2+, Zn2+, Fe3+ and Al3+). These catalysts exhibited novel morphologies and can be directly applied as monolithic materials for CO oxidation. Among the MCo2O4 NA catalysts, CuCo2O4 nanoneedles manifested the highest catalytic activity in dry air, achieving an efficient 100% CO oxidation conversion of 20 000 h−1 at 146 °C, due to its reducibility at lower temperature, lattice distortion of the spinel structure, and abundant surface-adsorbed oxygen (Oads). The doped catalytic systems were further optimized by controlling the volume ratio of reactive components in the mixed solvent, the Cu or Mn contents to determine excellent catalysts for direct application to CO oxidation at 1.0 vol% moisture. Penthorum chinense-like MnCo2O4 NAs showed optimal catalytic performance at 1 vol% moisture (T100 = 175 °C), with activity higher than that of the CuCo2O4 NA catalyst, indicating that the synergistic effect between MnOx and Co3O4 improved the moisture resistance and stability. It was concluded that the moisture resistance provided by introducing active sites on Co-based catalysts decreased as follows: Mn sites > Co sites > Cu sites > Ni sites. MCo2O4 NAs, with predominantly exposed {110} surfaces, showed higher catalytic activity than catalysts with exposed {111} surfaces. This study suggests that the as-prepared MnCo2O4 NAs anchored on 3D Ni foam with remarkable moisture resistance have potential applications in CO oxidation.

Malodorous aldehyde gases, such as n-butyraldehyde, are not only problematic volatile organic compound pollutants but also have offensive odors with a very low olfactory threshold (ppb), which can reduce the quality of daily life even at a very low concentration (0.1–10 ppm). Materials such as activated carbon (AC), metal–organic frameworks (MOFs), and mesoporous silica nanoparticles (MSNs) represent prime candidates for air quality remediation owing to their overall high surface area and accessibility of surface functionalization. Flammability and Chinese government policies on the use of AC and the high cost of MOFs discourage their development and application. MSNs have been the focus of substantial research recently owing to their high specific surface area and pore volume, and surface-modifiable chemical properties because of Si–OH groups. However, pore clogging, due to the high load of functional groups, limits improvement of the MSNs’ adsorption performance. Also, the processes of functionalization are complex and time-consuming. Here, we used a new strategy to synthesize ordered mesoporous silica with a high specific area (1000 m2 g−1) and adsorption capability (62.92 mg n-C4H8O per g of adsorbent), as well as high loading of amino groups, without pore filling from a one-step sol–gel process at room temperature. The high adsorption capacity on the amine surface in this study reveals the potential utility of MSNs as malodorous aldehyde gas abatement materials.

A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co3O4 nanoarray (NA) precursors on Ni substrates, forming a series of Co3O4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co3O4 nanostructures which depends upon the reaction time, with and without CTAB or NH4F is investigated in detail, which is used to further demonstrate the growth mechanism of Co3O4 nanoarrays with different morphologies. CO is chosen as a probe molecule to evaluate the catalytic performance over the synthesized Co-based oxide catalysts, and the effect of morphological transformation on the catalytic activity is further confirmed via using TEM, H2-TPR, XPS, Raman spectroscopy and in situ Raman spectroscopy. As a proof of concept application, core-shell Co3O4 NAs-8 presenting hierarchical nanosheets@nanoneedle arrays with a low density of nanoneedles exhibits the highest catalytic activity and long-term stability due to its low-temperature reducibility, the lattice distortion of the spinel structure and the abundance of surface-adsorbed oxygen (Oads). It is confirmed that CO oxidation on the surface of Co3O4 can proceed through the Langmuir-Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co3O4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis.

A HKUST-1 metal–organic framework membrane was constructed on porous Al2O3 granules for the first time for the removal of low concentration CH3SH. The granules exhibited higher sulfur capacity than the pure HKUST-1 powders owing to the excellent dispersion of the MOF membrane on the Al2O3 substrate. The granules also showed good water resistibility.

The rational design and controllable synthesis of novel nanostructured metal oxide/graphene hybrid materials have attracted extensive attention for next-generation lithium ion batteries (LIBs). In this work, three dimensional (3D) graphene framework bonding ultrafine NiO nanocrystals are fabricated in situ through hydrothermal treatment and a subsequent thermal annealing strategy. During the material design process, the 2D bark-like Ni precursor which duplicated the morphology of GO was formed firstly by adjusting the amount of the structure-directing agent. Meanwhile, the 3D interconnected framework of graphene can be obtained via π–π interaction. Subsequently, thermal treatment was performed to transform the Ni precursors into NiO nanocrystals with an average particle size of 6.38 nm. The chemical bonding between the NiO nanocrystals and the graphene framework was confirmed by Raman and XPS analysis. Benefiting from the unique architecture, the hybrid anode material exhibits an ultrahigh reversible capacity of 1104 mA h g−1 at a rate of 0.2C after 250 successive cycles, and an outstanding rate capability (440 mA h g−1 at 3.0C). Moreover, superior capacity retention is also demonstrated.

Vgmax Hot-Carrier-Injection (HCI) degradation in Multi-finger p-Laterally-Diffused Metal-Oxide-Semiconductor Field-Effect-Transistors (LDMOSFET) had been investigated by Multi-Region Direct-Current-Current-Voltage (MR-DCIV) characterization method-probing the interface state distribution along the channel, accumulation and (Shallow Trench Isolation) STI-drift region. The method feasibility was verified by device simulation and stress experiment. The enhanced interface state generation in the channel and accumulation region was clearly revealed in multi-finger layout device. This layout dependent degradation was associated with self-heating effect and temperature accelerated Vgmax HCI stress.

The hollow ZnO/ZnFe2O4 microspheres with heterogeneous structure are synthesized by direct pyrolysis of metal-organic frameworks. The as-prepared ZnO/ZnFe2O4 microspheres have well-defined spherical morphology with ∼1.5 μm in diameter and multiple porous shells constructed by interpenetrated ZnO and ZnFe2O4 heterogeneous nanoparticles. Interestingly, the hollow ZnO/ZnFe2O4 microspheres based gas sensors show interestingly temperature-dependent n-p-n type conductivity transition in detecting low-concentration VOC gases including ethanol, acetone, toluene and benzene. This interestingly n-p-n transition phenomenon is mainly ascribed to the trade-off of highly separated electron-hole pairs originated from the staggered type-II band alignment of in-shell ZnO-ZnFe2O4 hetero-interfaces, which is modulated by thermally-dependent ionization reaction of surface-absorbed oxygen molecules and extra electron injection due to surface reaction of reductive VOCs during gas-sensing process. This work presents a facile route to construct hollow nanostructures with heterogeneous feature and provides a new insight into sensing mechanism, exhibiting the potential application of ZnO/ZnFe2O4 microspheres in developing highly sensitive and selective gas-sensing materials in detecting low-concentration VOCs.

A facile template-free synthesis strategy is demonstrated to fabricate nanostructured NiO/N-doped graphene hybrid, in which NiO hollow nanospheres with hierarchically mesoporous structure are tightly anchored on N-doped graphene matrix. The mesoporous shell of NiO can not only provide sufficient electrode/electrolyte contact areas to accelerate ion diffusion and electron exchange, but also efficiently mitigate the volume change that occurs during long-time reactions. Simultaneously, the reduced graphene oxide with doping nitrogen atoms are employed as effectively conductive backbone, further enhancing the electrochemical performances. When used as anodic material for lithium ion batteries, the synergistic system delivers a reversible capacity up to 1104.6 mAh g−1 after 150 cycles at a current density of 0.08 A g−1 and 422.3 mAh g−1 at a high charging rate of 4 A g−1, which is better than those of the bare counterparts and most other NiO-based materials reported in the previous literatures. The hierarchically hollow NiO nanostructure combined with N-doped graphene matrix provides a promising candidate applied in advanced anode materials for lithium ion batteries.

Fabrication of heterojunctioned gas sensing materials is regarded as one of the most efficient ways to improve sensor performance. Herein, finely dispersed NiO/NiGa2O4 heterojunction-based material is synthesized successfully by calcining the atomically mixed Ni-Ga precursors of layered double hydroxides (LDH). The optimized atomic ratio of Ni/Ga is 2.5 and the annealing temperature in H2 is 300 °C, and the obtained material shows a high response of 10.54 to 5 ppm toluene working at a low temperature of 200 °C. As a comparison, the co-precipitation method prepared analogue shows relatively lower response with the value of 8.5 at a higher working temperature of 250 °C, showing the advantage of this LDH prepared material. Moreover, it shows also high selectivity over other interfering gases such as chlorobenzene, acetone, humidity, NH3 and SO2, and long stability over one month measurements. X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy show the efficient NiO/NiGa2O4 heterojunctions fabricated from LDH precursors, which are further enhanced in H2 to induce oxygen vacancy and Schottky barrier of Ni-NiO/NiGa2O4, promising for high performance gas sensors.

Ceria zirconia solid solution with high oxygen storage capacity (OSC) and thermal stability under 1000 ​°C is quite important for support materials in three-way catalysts (TWCs). In this work, Ce1-xZrxO2 with different Zr dopants (x ​= ​0, 0.125, 0.250 and 0.375) have been prepared by flame spray pyrolysis (FSP) with carboxylic acid or ethanol and carboxylic acid (v:v 1:4) solvents. The influences of Zr content and the addition of ethanol into carboxylic acid on the OSC performance and thermal stability have been systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Raman analysis, field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), hydrogen-temperature programmed reduction (H2-TPR), and pulse thermal analysis using H2 as reducing agent. The presence of cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can enhance the formation of oxygen vacancies and the mobility of lattice oxygen in ceria-zirconia solutions, which results in the largest OSC (349 ​μmol ​g−1) among the fresh samples. The cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can also promote the thermal stability under 1000 ​°C to preserve better OSC (202 ​μmol ​g−1) than other aged samples. Furthermore, after adding with ethanol into carboxylic acid solvent, the OSC of the sample further increases to 371 ​μmol ​g−1 for the increment of oxygen vacancy concentration. It is worthy to note that the introduction of ethanol can suppress Zr migration from the lattice to the surface of CeO2 at high temperature, further enhancing OSC (240 ​μmol ​g−1) and thermal stability.

Introduction: Pyrite cinder is one of the important secondary resources, but typically contains a certain amount of arsenic, which is harmful to metallurgical process. It usually hopes to remove the arsenic prior to recycle the valuable element in the pyrite cinders. Methods & Materials: In this study, the arsenic in the cinders was selectively removed using the alkalic leaching method so as to reduce the loss of ferric and other valuable elements. Results & Discussion: The content of arsenic in pyrite cinders was reduced to 0.08% through the investigation of the factors, including particle size, alkaline concentration, temperature, solid-liquid ratio (S/L) and leaching time. Then, the ferric precipitation method was used to remove the arsenic in the leaching solution. More than 99% of the arsenic can be removed by controlling the pH and the ratio of ferric and arsenic (Fe/As) in ambient temperature, and the arsenic concentration in the solution was reduced to less than 0.5mg/L. Conclusion: It was found that the precipitated arsenic was mainly amorphous based on the analysis of sediment.

The chlorination−volatilization process has been adopted to make full use of gold-bearing and iron-rich pyrite cinder. However, problems of low recovery rate, pulverization of pellets, and ring formation have been encountered during the industrialization of this process. The effects of various parameters on the volatilization rates of valuable metals and on the compressive strength of roasted pellets were investigated in this paper. The parameters include the CaCl2 dosage, heating temperature, and holding time. The results show that heating temperature is the most important parameter for the recovery of target metals. More CaCl2 was needed for the recovery of zinc than for the recovery of gold, silver, and lead. CaCl2 started to react with sulfides/SO2/SiO2 at temperatures below the melting point of CaCl2 to generate Cl2/HCl. Gaseous CaCl2 was formed at higher temperatures and could react with any of the components. The compressive strength of roasted CaCl2-bearing pellets first decreased slowly with increasing temperature at temperatures lower than 873 K, which could result in the pulverization of pellets during heating. Their compressive strength increased dramatically with increasing temperature at temperatures greater than 1273 K. Certain quantities of CaCl2 and Fe(II) could improve the compressive strength of the roasted pellets; however, the addition of excessive CaCl2 decreased the compressive strength of pellets.

Chaneya ningmingensis sp. nov. is described from the Oligocene Ningming Formation in Guangxi Zhuang Autonomous Region, South China. Fruits of the new species are characterized by bearing five persistent, free, large petals, each containing five craspedodromous, longitudinally subparallel primary veins, and their thickened central disk bearing one whorl of five free, orbicular ovaries. The discovery of C. ningmingensis provides the evidence of the occurrence of Chaneya Wang et Manchester in Oligocene sediments of South China. This is the first Oligocene record of Chaneya from East Asia. Considering the continuous occurrence of Chaneya in the Cenozoic deposits from the early Eocene to the Miocene, East Asia may be a center of diversification and differentiation for the genus Chaneya.

An inorganic-organic hybrid flocculant Al(OH)3-polyacrylamide (Al-PAM) with narrow molecular weight distribution was synthesized using inverse microemulsion polymerization. The hybrid polymer Al-PAM was characterized by Infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and scanning electron microscopy, and it was found that it had a ‘star-like’ structure in which Al(OH)3 colloidal particles acted as cores linking PAM chains. The properties of Al-PAM were investigated in flocculating 10 wt% cyanide tailing suspensions. It was found that as the amount of Al-PAMM1 with high molecular weight and aluminum content increased, the initial settling rate of particles accelerated, achieving the maximum 6.6 m/h, 17.3 times the rate of the control without flocculants. The turbidity of the supernatant decreased to 35 ± 2 NTU accordingly, compared to 353 ± 2 NTU of that in the control, which meant that 90.0% of turbidity was removed from the cyanide tailing suspensions. The flocculation mechanism was further explored by floccule size and ζ potential measurements. The superior performance of cationic Al-PAM in flocculating negatively charged particles compared to commercial non-ionic GG indicated that electrostatic repulsion between tailing particles was a crucial factor in deciding the flocculation performance of the polymer. The study demonstrated that both charge neutralization and bridge adsorption were conductive to the particle flocculation.

A series of silica supported Mn–Ce composite oxides with different Mn/Ce molar ratios were obtained by a simple and environment-friendly oxalate route. The physical and chemical properties were characterized by TG, BET, SEM, TEM, XPS and TPR analysis. All catalysts showed excellent activity towards deep oxidation of benzene. The effects of Mn/Ce ratio, calcination temperature on the structure and catalytic activity of catalysts were investigated. Catalyst from nitrate precursor was also characterized to compare the influence of different precursors. The 6Mn4Ce sample from oxalate route sintered at 400 °C showed the maximum reaction rate of 0.50 mmol gcat−1h−1; T90 of the catalyst is 216 °C. The catalytic activity is related to surface area, pore size distribution, surface elemental species, particle size distribution and low temperature reducibility which may derived from synergistic effect between manganese and cerium oxide. Compared with nitrate precursors, catalyst from oxalate route can be more finely dispersed on the pores of silica without damaging the pore structure of support. The role of silica is not only a support, but also an in situ reaction site for precursor’s decomposition, which ensure the finely distribution of active components. In addition, the best catalyst showed good stability with prolonged time on stream.

Nowadays, highly sensitive metal oxide semiconductor gas sensors are exerting a growing important influence on the detection of target gases. It is still challenging to get both high sensitivity and selectivity to effectively distinguish gas mixtures. In this study, Mn doped ZnO (MZO) is prepared by a facile co-precipitation method and then further modified by CdO addition. The results show that 2.2 mol% MZO has high responses to both acetone and ethanol, while 10 mol% CdO activated 1 mol% MZO exhibits excellent sensitivity to ethanol and neglectable response to acetone. This is explained by the enhanced alkalinity of ZnO by the CdO addition expelling acetone from adsorption onto the sensor surface, which is verified by temperature–programmed CO2 desorption. Moreover, the CdO-MZO gas sensor has an optimized working temperature of 240 °C, far lower than 340 °C of MZO, due to the higher oxidativity as proved by the temperature-programmed H2 reduction. The MZO and CdO-MZO gas sensors are then used as a sensor array to distinguish the ethanol and acetone concentrations in mixtures with varied ratios, showing the promise of the gas sensor property tailoring approach for future high performance gas sensors. Keywords: Mn doped ZnO, CdO modification, Operating temperature, Sensitivity, Selectivity

Nowadays, detection of trace concentration gases is still challenging for portable sensors, especially for the low-cost and easily operated metal–oxide–semiconductor (MOX) gas sensors. In this paper, a widely applicable amplification circuit is designed and fabricated to evidently enhance the signal of the MOX sensors by adding a field effect transistor (FET) into the conventional circuits. By optimizing the FET parameters and the loading resistance, this amplification circuit enables the commercial Figaro TGS2602 toluene sensors response effectively to the highest permissive limit (0.26 ppm) of toluene in indoor air of cars, with the detection limit of ~0.1 ppm. Furthermore, this circuit can also make the commercial Hanwei MP502 acetone sensors and MQ3 ethanol sensors response to the 1–2-ppm acetone in breath of diabetes and 2-ppm ethanol for fast and effectively drinker driver screening. The mechanism is investigated to be the gate voltage induced resistance change of the FET, with the highest theoretically estimated and experimentally measured magnification factor of 5–6. This FET amplifier can effectively enable the ppm level commercial MOX sensors response to sub-ppm level gases, promising for MOX gas sensor integration and also for other kind of resistive sensors.

Mn 3 O 4 /N-doped graphene (Mn 3 O 4 /NG) hybrids were synthesized by a simple one-pot hydrothermal process. The scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray powder diffraction (XRD), Thermogravimetric analysis (TG), Raman Spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the microstructure, crystallinity and compositions. It is demonstrated that Mn 3 O 4 nanoparticles are high-dispersely anchored onto the individual graphene nanosheets, and also found that, in contrast with pure Mn 3 O 4 obtained without graphene added, the introduction of graphene effectively restricts the growth of Mn 3 O 4 nanoparticles. Simultaneously, the anchored well-dispersed Mn 3 O 4 nanoparticles also play a role as spacers in preventing the restacking of graphene sheets and producing abundant nanoscale porous channels. Hence, it is well anticipated that the accessibility and reactivity of electrolyte molecules with Mn 3 O 4 /NG electrode are highly improved during the electrochemical process. As the anode material for lithium ion batteries, the Mn 3 O 4 /NG hybrid electrode displays an outstanding reversible capacity of 1208.4 mAh g −1 after 150 cycles at a current density of 88 mA g −1 , even still retained 284 mAh g −1 at a high current density of 4400 mA g −1 after 10 cycles, indicating the superior capacity retention, which is better than those of bare Mn 3 O 4 , and most other Mn 3 O 4 /C hybrids in reported literatures. Finally, the superior performance can be ascribed to the uniformly distribution of ultrafine Mn 3 O 4 nanoparticles, successful nitrogen doping of graphene and favorable structures of the composites.

Lithium iron phosphate (LiFePO4)/lithium manganese phosphate (LiMnPO4)-positive material was successfully prepared through ball milling and high-temperature sintering using manganese acetate, lithium hydroxide, ammonium dihydrogen phosphate, and ferrous oxalate as raw materials. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, a constant current charge–discharge test, cyclic voltammetry, and electrochemical impedance spectroscopy. The effects of lithium iron phosphate coating were also discussed. Because of its special core–shell structure, the as-prepared LiMn0.7Fe0.3PO4–LiFePO4–C exhibits excellent electrochemical performance. The discharge capacity reached 136.6 mAh/g and the specific discharge energy reached 506.9 Wh/kg at a rate of 0.1 C.

In this work, ruthenium-based bimetallic catalysts of the formula Ru–5M/TiO2 (M = Mn, Co, Ce, Cu, Fe) were prepared and evaluated in benzene oxidation, and Ru–5Co/TiO2 exhibited the lowest complete oxidation temperature (220 °C), demonstrating Co3O4 as the best dopant. The influence of the Ru and Co contents on the catalytic activity was also studied, and 1 wt% Ru and 5 wt% Co3O4 were confirmed. Water vapor showed an inhibition effect on benzene oxidation at 210 °C, whereas the catalytic efficiency was barely influenced at a higher temperature (230 °C). STEM analyses revealed that Ru–Co bimetallic species showed similar distributions on the catalytic surface. Based on the correlation of the catalytic results with various characterization techniques, the synergistic effect between Ru and Co was well demonstrated, and a four-step transformation in the oxidation process was concluded. Besides, systematic in situ FTIR studies for benzene oxidation over Ru/TiO2, Co/TiO2, and Ru–5Co/TiO2 were conducted and compared, and many organic intermediates were observed in the in situ FTIR spectra. Accordingly, the reaction mechanism for benzene oxidation over the Ru–Co bimetallic catalyst was proposed.

High responses and good selectivity are key sensing properties of metal oxide (MOX) gas sensors. However, it is still a major challenge for a single MOX gas sensor to achieve both of them. Specially, the research in the field of high performance gas sensors has been hindered by negative effects of the typical interference, relative humidity (RH). In this paper, we report the successful preparation of gold–tin co-sensitized ZnO layered porous nanocrystals (Au–5Sn–ZLPCs) via a sequential solvothermal reaction and deposition-reduction method. Based on Sn dopants sensitized ZLPCs, the introduction of Au decoration can act as a secondary sensitized element on the crystal surfaces of ZnO. The special synergy between noble metals and oxides can introduce additional catalytic effects to further improve sensing properties. As a result of Au–Sn co-sensitization, sensing properties of sensors towards reducing VOC gas were significantly enhanced, while those towards oxidizing ozone gas were different to each other. Besides the typical sensing properties including responses, operating temperature, response & recovery properties, etc., Au–Sn co-sensitized samples significantly reduced negative effects of RH on responses to both reducing and oxidizing gases (good anti-humidity).

ZnO/ZnFe2O4 hollow cube composites with heterogeneous structure are synthesized by a facile strategy through simple and direct pyrolysis of FeIII-modified Zn-based metal–organic frameworks. The as-synthesized ZnO/ZnFe2O4 hollow cubes have well-defined cube morphology with an ∼2 μm and multiple porous shell constructed from interpenetrated ZnO and ZnFe2O4 heterogeneous nanoparticles, providing structurally combined mesoporous channels for facilitating the diffusion and surface reaction of gas molecules. In addition, a comparative sensing performance investigation between ZnO/ZnFe2O4 hollow cubes and singular ZnO demonstrates that, in contrast with ZnO, the ZnO/ZnFe2O4 hollow cubes show significantly enhanced chemical sensing sensitivity towards low-concentration acetone. Furthermore, the ZnO/ZnFe2O4 hollow cubes exhibit good reproducibility and selectivity towards gaseous acetone. The enhanced sensing performance of the MOF-derived ZnO/ZnFe2O4 hollow cubes is ascribed to the unique hierarchical structure with high specific surface area, abundant exposed active sites with surface-adsorbed oxygen species and heterojunctions formed at the interfaces between ZnO and ZnFe2O4.

In recent years, ozone remains to be one of the most common air pollutants generated by ultraviolet irradiation and/or emitted from daily machines. Since ozone is harmful to both humans and the environment even in trace concentrations, it is challenging to catalytically decompose ozone with high efficiency and low cost. In this study, surface exposure and particle size-controlled cuprous oxide (Cu2O) is synthesized in ambient conditions through a simple reductive solution chemistry route. Ozone decomposition test shows that 40 nm cubic Cu2O has 100% degradation efficiency at 25 °C, with high resistance to water vapor. Moreover, the high catalytic activity can also be maintained for >6 h at 0 °C. The related mechanism is found to be a facile desorption of the weakly adsorbed O22− intermediate on {100} plane of cubic Cu2O in the ozone decomposition process. This is proven by oxygen temperature programmed desorption, X-ray photoelectron spectroscopy and atomic model establishments. The results provide promising evidence of the facilely synthesized Cu2O catalyst in a highly active ozone degradation process, for the benefit of human health and environment sustainability.

Particulate matter (PM) from cooking has caused seriously indoor air pollutant and aroused risk to human health. It is urged to get deep knowledge of their spatial-temporal distribution of source emission characteristics, especially ultrafine particles (UFP

A novel Pd-Ni/SBA-15 catalyst synthesized by co-impregnation of Pd and Ni precursors onto porous SBA-15 silica support was used for catalytic removal of gaseous benzene. Compared to original Pd/SBA-15 catalyst, the addition of Ni significantly promoted the catalytic performance. Moreover, with introducing acid treatment, the new Pd-Ni/SBA-15 catalyst showed much better catalytic activity than both Pd/SBA-15 catalyst and original Pd-Ni/SBA-15 catalyst, and the benzene could be completely oxidized into CO 2 and H 2 O at 260 °C over the new catalyst at a high space velocity of 12,0000 mL/(g h).

Noble metal@metal oxides have attracted extensive attention as gas-sensing materials due to the formation of Schottky junction, modulating surface physicochemical properties of oxide nanomaterials. Herein, a facile way was developed to construct core-shell Au@ZnO nanoparticles through direct pyrolysis of Au@Zn-based metal-organic framework (MOF). The obtained Au@ZnO nanoparticles have ~ 50 nm Au nanoparticles as cores and interpenetrated ZnO nanoparticles (~ 20 nm) as porous shells. When applied as gas-sensing materials, the unique core-shell Au@ZnO nanoparticles exhibited significantly enhanced gas-sensing response and selectivity towards sub-ppm level acetone at 300 °C. The response value of Au@ZnO nanoparticles was 11 times higher than that of singular ZnO nanoparticles towards 1 ppm of acetone. The enhanced gas-sensing properties are ascribed to the electronic and chemical sensitization of Au nanoparticles, due to the formation of Schottky junction within Au-ZnO hetero-interface of core-shell nanoparticles.

In this work, we report the synthesis of reduced graphene oxide (rGO) modified platinum (Pt) catalysts for decreasing the temperature of the complete conversion of benzene. The X-ray photoelectron spectroscopy (XPS) analysis reveals the presence of electron transfer between rGO and Pt, which has a significant effect on the catalytic activity. The electron transfer is also proved by Raman spectra in term of the shifting of G-band belonging to the rGO. H 2 -temperature programmed reduction (H 2 -TPR) results indicate that the rGO facilitates the reduction of surface oxygen over the catalyst. Moreover, increasing the concentration of rGO within a certain range has a positive influence on the catalytic activity.

Heterogeneous interface in materials has recently attracted much attention because of its crucial role in catalytic reaction. Herein, we report the preparation of high-quality Co 3 O 4 -decorated one dimensional (1D) MnO 2 hybrids and their application in catalytic degradation of carcinogenic benzene. Three kinds of 1D MnO 2 including α-MnO 2 nanowires, α-MnO 2 nanorods and β-MnO 2 microrods were firstly synthesized by different hydrothermal method, followed by a controlled Co 3 O 4 functionalized process. The homogeneous coating of the Co 3 O 4 nanoparticles on the surface of the MnO 2 created large amounts of remarkable MnO 2 -Co 3 O 4 heterogeneous interface which was characterized by SEM and TEM techniques. XPS and H 2 -TPR studies revealed the decorated hybrids had better low-temperature reducibility and more active surface adsorbed oxygen species. Compared with the bare MnO 2 , these hybrid MnO 2 @Co 3 O 4 nanaostructures showed improved catalytic reactivity toward gaseous benzene oxidation, and the enhancement had different dependence upon the various MnO 2 . Under high space velocity of 120,000 mL g −1 h −1 , the best-performed α-MnO 2 nanowires@Co 3 O 4 can decrease the T 90 (temperature of 90% benzene conversion) to 247 °C which was almost 100 °C lower than the pure α-MnO 2 nanowires. Their significantly promoted catalytic activity should be attributed to the strong synergistic effect due to the existence of remarkable MnO 2 -Co 3 O 4 hetero-interface.

Three-dimensional cubic ordered mesoporous carbon with chitosan (Ia3d-CS), which was synthesized via exothermic reaction between liquid potassium and carbon monoxide gas, was coated on the active carbon (AC) electrode as a capacitive deionization (CDI) disinfection electrode. The results showed that Ia3d-CS-2 as CDI electrode exhibited the quick ion diffusion and strong charge transfer performance, due to the three-dimensional pore structure and specific surface area. The electrode of Ia3d-CS-2 displayed a specific capacity of 191.22 F/g at a scan rate of 100 mV·s−1 in 0.5 M NaCl aqueous solution. In a CDI recycling system, Ia3d-CS-x electrode showed good cyclic stability, and the electrosorption capacity of Ia3d-CS-2 electrode can achieve 1.31 mg/g at 1.2 V in 100 mg/l NaCl aqueous solutions. Subsequently, Ia3d-CS-2 electrode had an excellent disinfection efficiency of killing about 99.99% Escherichia coli within 30 min during the CDI process at applied 1.2 V. Considering those excellent properties of the fabricated Ia3d-CS-x electrode, which should be a better candidate for high-performance deionization application.

Nowadays, it is still technologically challenging to prepare highly sensitive sensing films using microelectrical mechanical system (MEMS) compatible methods for miniaturized sensors with low power consumption and high yield. Here, sensitive cross-linked SnO2:NiO networks were successfully fabricated by sputtering SnO2:NiO target onto the etched self-assembled triangle polystyrene (PS) microsphere arrays and then ultrasonically removing the PS microsphere templates in acetone. The optimum line width (~ 600 nm) and film thickness (~ 50 nm) of SnO2:NiO networks were obtained by varying the plasma etching time and the sputtering time. Then, thermal annealing at 500 °C in H2 was implemented to activate and reorganize the as-deposited amorphous SnO2:NiO thin films. Compared with continuous SnO2:NiO thin film counterparts, these cross-linked films show the highest response of ~ 9 to 50 ppm ethanol, low detection limits (

Nowadays, it is necessary and challenging to prepare Cu

Two-dimensional materials have been extensively investigated in the fields of electrochemical sensors, field-effect transistors, and other electronic devices due to their large surface areas, high compatibility with device integration, and so on. Conventional electrodes, such as precious metal layers that are deposited on polymer or silicon wafers, have gradually revealed increasing difficulties in adapting to various device structures, especially for two-dimensional materials, which prefer high exposure of surface atoms. Here, we demonstrate a tailorable metal-ceramic (Cu-TiC

Rational design LDHs (layered double hydroxides) with 3D hierarchical hollow structures have generated widespread interest for catalytic oxidation due to the high complexity in shell architecture and composition. Herein, we reported a handy two-step method to construct a 3D hierarchical NiCo2O4/NiO nanocage. This synthetic strategy contains a partial in situ transformation of ZIF-67 (zeolitic imidazolate framework-67) into Co-NiLDH yolk-shelled structures following ethanol etching, and a structure-preserved transformation from Co-NiLDH@ZIF-67 to a biphase nanocage following calcination. CoNi-yh-T (varied reaction time and calcination temperature) nanocages were investigated systematically by Brunauer&ndash, Emmett&ndash, Teller (BET), X-ray photoelectron spectroscopy (XPS), H2- temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and studied for toluene oxidation. The CoNi-6h-350 sample showed much higher activity with 90% toluene conversion (T90) at 229 &deg, C at a high space velocity (SV = 60,000 mL g&minus, 1 h&minus, 1) than other catalysts (T90 &gt, 240 &deg, C). Abundant surface high valence Co ions caused by the novel hierarchical nanostructures, together with adsorbed oxygen species and abundant medium-strength surface acid sites, played a key role for catalytic activities.

Although significant developments have been made in the low-concentration formaldehyde monitoring in indoor air by using gas sensors, they still suffer from insufficient performance for achieving ppb-level detection. In this work, oriented Si nanowires (SiNWs) with high specific surface area were prepared via metal-assisted chemical etching method (MACE), and then were uniformly coated with graphene oxide (GO) followed by the subsequent reductive process in H2/Ar atmosphere at 800 °C to obtain reduced graphene oxide (RGO). The RGO coating (RGO@n-SiNWs) obviously enhances SiNWs sensitivity to low-concentration formaldehyde, benefiting from the increased specific surface area, the sensitization effect of RGO, and the formation of p-n junction between SiNWs and RGO. Specifically, RGO@n-SiNWs exhibits a high response of 6.4 to 10 ppm formaldehyde at 300 °C, which is about 2.6 times higher than that of pristine SiNWs (~ 2.5). Furthermore, the RGO@n-SiNWs show a high response of 2.4 to 0.1 ppm formaldehyde which is the largest permissive concentration in indoor air, a low detection limit of 35 ppb obtained by non-linear fitting, and fast response/recovery times of 30 and 10 s. In the meanwhile, the sensor also shows high selectivity over other typical interfering gases such as ethanol, acetone, ammonia, methanol, xylene, and toluene, and shows a high stability over a measurement period of 6 days. These results enable the highly sensitive, selective, and stable detection of low-concentration formaldehyde to guarantee safety of indoor environment. Electronic supplementary material The online version of this article (10.1186/s11671-019-2921-2) contains supplementary material, which is available to authorized users.

CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption at &minus, 196 &deg, C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 &deg, C at space velocity (60,000 mL &times, g&minus, 1 &times, h&minus, 1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.

The catalytic activities of CeO2-MnOx composite oxides synthesized through oxalate method were researched. The results exhibited that the catalytic properties of CeO2-MnOx composite oxides were higher than pure CeO2 or MnOx. When the Ceat/Mnat ratio was 3:7, the catalytic activity reached the best. In addition, the activities of CeO2-MnOx synthesized through different routes over benzene oxidation were also comparative researched. The result indicated that the catalytic property of sample prepared by oxalate method was better than others, which maybe closely related with their meso-structures. Meanwhile, the effects of synergistic interaction and oxygen species in the samples on the catalytic ability can&rsquo, t be ignored.