Fabricating active materials into specific macrostructures is critical in the pursuit of high electro-catalytic activity. Herein we demonstrate that a three-dimensional (3D) architecture of NiFe layered double hydroxide (NiFe-LDH) significantly reduced the onset potential, yielded high current density at small overpotentials, and showed outstanding stability in electrochemical oxygen evolution reaction.

Monodisperse nanospheres and spherical structures derived from them, such as core-shell or hollow nanospheres, have become a new study focus because their potential applications in optics, electrics, catalysis, sensors, and so forth. [1][2][3][4] Many researchers are working on the preparation of new monodisperse nanospheres and their functional transformation. [5][6][7][8][9][10][11][12][13][14] The traditional monodisperse micro-or nanospheres are amorphous silica and polymer colloids which were prepared by controlled hydrolyzation of tetraethyl orthosilicate and emulsion polymerization. [5][6][7][8] Using these colloidal templates, the Caruso group has prepared many kinds of porous hollow spheres and core-shell nanospheres through the "layer-by-layer" method, such as coating the spheres with noble-metal nanoparticles, metal oxide nanoparticles, polyelectrolytes, or biomolecules with specific electronic, optical, catalytic, and biological applications. 2,10 In recent years, much progress has been made on the preparation of monodisperse inorganic nanospheres. [11][12][13] For example, the Xia group has developed the glycol refluxing method to synthesize monodisperse metal micro or nanospheres, such as Bi, Pb, Se, metal alloys, and their functional core-shell structures. 11 Our group has developed the hydrothermal or solvothermal method to synthesize monodisperse micro-and nanospheres, such as chalcogenide, carbon, single-crystalline magnetic ferrite, and so forth. [12][13][14] By the template of carbon colloids, many hollow spheres, such as Ga 2 O 3 , GaN, WO 3 , and so forth have been prepared with special optical or sensor properties. 14 From above, it is concluded that because the intrinsic properties of monodisperse nanospheres can be finely tuned by changing parameters such as diameter, chemical composition, bulk structure, and crystallinity, searching for novel methods and preparing more kinds of monodisperse nanospheres are still required for some special applications. 6 Cuprous oxide (Cu 2 O), a p-type semiconductor with unique optical and magnetic properties, has potential applications in solar energy conversion, electronics, magnetic storage, catalysis, and gas sensors. CuO is also a potential material with many applications in catalysis, gas sensing, and lithium-copper oxide electrochemical cells. [15][16][17][18] CuO was the first kind of humidity sensing material found by Braver et al. in 1931. It was reported that Cu 2 O films had gas sensing activity at ∼200 °C. 16 Considering the potential applications of copper-based materials, many kinds of morphologies have been reported, such as wires, monodisperse nanocubes, octahedral nanocages, hollow nanospheres, and so forth. 15,17,18 Typically, the Zeng group used a solvothermal method in N,N-dimethylformamide (DMF) at 150-180 °C for 20-40 h to get hollow Cu 2 O nanospheres. They found the formation process of Cu 2 O hollow spheres included formation of CuO nanocrystals, aggregation of primary CuO nanocrystals, and the reductive transformation to C...

Global atmospheric emissions of 16 polycyclic aromatic hydrocarbons (PAHs) from 69 major sources were estimated for a period from 1960 to 2030. Regression models and a technology split method were used to estimate country and time specific emission factors, resulting in a new estimate of PAH emission factor variation among different countries and over time. PAH emissions in 2007 were spatially resolved to 0.1°× 0.1° grids based on a newly developed global high-resolution fuel combustion inventory (PKU-FUEL-2007). The global total annual atmospheric emission of 16 PAHs in 2007 was 504 Gg (331-818 Gg, as interquartile range), with residential/commercial biomass burning (60.5%), open-field biomass burning (agricultural waste burning, deforestation, and wildfire, 13.6%), and petroleum consumption by on-road motor vehicles (12.8%) as the major sources. South (87 Gg), East (111 Gg), and Southeast Asia (52 Gg) were the regions with the highest PAH emission densities, contributing half of the global total PAH emissions. Among the global total PAH emissions, 6.19% of the emissions were in the form of high molecular weight carcinogenic compounds and the percentage of the carcinogenic PAHs was higher in developing countries (6.22%) than in developed countries (5.73%), due to the differences in energy structures and the disparities of technology. The potential health impact of the PAH emissions was greatest in the parts of the world with high anthropogenic PAH emissions, because of the overlap of the high emissions and high population densities. Global total PAH emissions peaked at 592 Gg in 1995 and declined gradually to 499 Gg in 2008. Total PAH emissions from developed countries peaked at 122 Gg in the early 1970s and decreased to 38 Gg in 2008. Simulation of PAH emissions from 2009 to 2030 revealed that PAH emissions in developed and developing countries would decrease by 46-71% and 48-64%, respectively, based on the six IPCC SRES scenarios.

The increasing concern over safety in homes and on industrial sites has generated great interest in reliable gas detection. In addition to nanoparticle and bulk sensor materials, one-dimensional (1D) nanostructure materials have been investigated to produce new semiconductor gas sensors since various kinds of 1D nanostructure metal oxides have been synthesized.[1±4] It has been reported that nanobelts of semiconducting oxides are very promising for sensors because the surface-to-volume ratio is very high, the oxide is single crystalline, and the size is likely to produce a complete depletion of carriers inside the belt. [5,6] Alcohol sensors with high selectivity and stability have always been in great demand in the biomedical, chemical, and food industries, especially in wine-quality monitoring and breath analysis. Conventional ethanol sensors, mostly based on SnO 2 , ZnO, TiO 2 , and Fe 2 O 3 , usually suffer from crosssensitivity to other gases, need a high working temperature, or have low long-term stability, although they have rather high sensitivity to ethanol. Furthermore, the kind of sensors used as a breath alcohol checker should have a high sensitivity to a lower-level ethanol vapor in human breath; common sensors are not good enough. [7] For these reasons, some new types of ethanol-sensing materials are still being studied and developed. One-dimensional vanadium oxides, commonly V 2 O 5 gels with fiber or ribbon morphologies, have been studied for many years, owing to their interesting properties and novel applications.[8±12] Nanowires of V 2 O 5 have been synthesized by polycondensation of vanadic acid, which involves ion exchange between Na + and H + ions in a resin from sodium metavanadate solutions. [13,14] However, since the synthesis process is very slow (several weeks), a rapid, mild, and high yield synthesis method would be desirable. Recently, Nesper and co-workers have developed a sol-gel method followed by hydrothermal treatment to prepare nanotubes of V 2 O 5 using suitable organic molecules as templates, which stimulated the interest of researchers. [15,16] V 2 O 5 nanorods have also been synthesized using a reverse-micelle technique.[17] Divanadium pentoxide belongs to the family of semiconducting oxides and has an interesting layered structure, which permits a wide variety of other molecules or cations to be embedded between the layers. This makes the 1D V 2 O 5 nanostructures likely to be good sensor materials.In this communication, we report the development of highly selective and stable ethanol sensors based on single-crystalline divanadium pentoxide nanobelts. The V 2 O 5 nanobelts were obtained by a simple mild hydrothermal method with high yield. During synthesis the morphology and flexibility could be modified by adding organic surfactants. Gas sensors have been fabricated using the divanadium pentoxide nanobelts and show great potential for the detection of ethanol molecules at a relatively low temperature. Figure 1A shows the typical X-ray diffraction (XRD) pattern for the divan...

[1] This study evaluates the sensitivity of long-range transport of black carbon (BC) from midlatitude and high-latitude source regions to the Arctic to aging, dry deposition, and wet removal processes using the Geophysical Fluid Dynamics Laboratory (GFDL) coupled chemistry and climate model (AM3). We derive a simple parameterization for BC aging (i.e., coating with soluble materials) which allows the rate of aging to vary diurnally and seasonally. Slow aging during winter permits BC to remain largely hydrophobic throughout transport from midlatitude source regions to the Arctic. In addition, we apply surface-dependent dry deposition velocities and reduce the wet removal efficiency of BC in ice clouds. The inclusion of the above parameterizations significantly improves simulated magnitude, seasonal cycle, and vertical profile of BC over the Arctic compared with those in the base model configuration. In particular, wintertime concentrations of BC in the Arctic are increased by a factor of 100 throughout the tropospheric column. On the basis of sensitivity tests involving each process, we find that the transport of BC to the Arctic is a synergistic process. A comprehensive understanding of microphysics and chemistry related to aging, dry and wet removal processes is thus essential to the simulation of BC concentrations over the Arctic.

A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.

Reduced graphene oxide (RGO) is an intriguing nanomaterial with tremendous potential for many applications. Although considerable efforts have been devoted to develop the reduction methods, it still needs further improvement, and how to choose an appropriate one for a specific application is a troublesome problem. In this study, RGOs were prepared by six typical reduction methods: N 2 H 4 3 H 2 O, NaOH, NaBH 4 , solvothermal, high-temperature, and two-step. The samples were systematic compared by four aspects: dispersibility, reduction degree, defect repair degree, and electrical conductivity. On the basis of the comparison, a simple evaluation criterion was proposed for qualitatively judging the quality of RGO. This evaluation criterion would be helpful to understand the mechanism of reduction and design more ideal reduction methods.

ZnxCo3‐xO4 nanoarrays are grown hydrothermally on Ti foils using appropriate ratios of Zn(NO3)2 and Co(NO3)2, NH4F and Co(NH2)2 in H2O together with the Ti substrate (autoclave, 120 °C, 10 h).