核壳结构SiO_2/SnO_2纳米复合微粒的合成与表征

文章从TEOS出发,先水解制备了纳米二氧化硅微粒,再以五水四氯化锡为锡源,碳酸铵为沉淀剂,通过控制反应条件,用共沉淀法在二氧化硅表面包覆上一层锡化物层,经600℃煅烧2 h后形成了具有核壳结构的SiO2/SnO2纳米复合微粒,并用透射电镜、激光粒度仪、FTIR等手段对其形貌、结构、组成进行了表征。结果表明：形成的核壳结构SiO2/SnO2纳米复合微粒是以二氧化硅为核,氧化锡为壳,内核直径约为120 nm,壳层厚度为8～18 nm;氧化锡基本以成膜包覆为主,伴有部分氧化锡自身成核团聚。     

碳球@纳米片状钴镍金属氧化物核壳型复合材料的制备及其电化学性能

以葡萄糖为碳源,采用水热炭化法制备碳球,然后以氯化钴和氯化镍为钴源和镍源,六次甲基四胺为沉淀剂,采用水热法和高温处理合成一种核壳结构的碳球@钴镍金属氧化物纳米复合材料,并研究其作为超级电容器电极材料的储能性能。借助X射线衍射、扫描电镜和低温氮气吸附/脱附等对材料的形貌和结构进行表征。采用循环伏安、恒电流充放电及交流阻抗等对材料的电化学性能进行研究。结果表明：碳球的加入能有效改善钴镍金属氧化物的分散性,同时降低材料的电子转移阻力,进而提高其电化学性能。当电流密度为1A/g时,所得碳球@钴镍金属氧化物核壳型复合材料的比电容为984.8F/g;当电流密度增大10倍（10A/g）时,仍保留86.3%的初始比电容值。当电流密度为15A/g时,经过2000次恒电流充放电后复合材料的比电容量保持率为94.6%,体现出较好的循环稳定性能。     

A facile method to prepare SnO2 nanotubes for use in efficient SnO2-TiO2 core-shell dye-sensitized solar cells

A high-efficiency photoelectrode for dye-sensitized solar cells (DSSCs) should combine the advantageous features of fast electron transport, slow interfacial electron recombination and large specific surface area. However, these three requirements usually cannot be achieved simultaneously in the present state-of-the-art research. Here we report a simple procedure to combine the three conflicting requirements by using porous SnO(2) nanotube-TiO(2) (SnO(2) NT-TiO(2)) core-shell structured photoanodes for DSSCs. The SnO(2) nanotubes are prepared by electrospinning of polyvinyl pyrrolidone (PVP)/tin dichloride dihydrate (SnCl(2)·2H(2)O) solution followed by direct sintering of the as-spun nanofibers. A possible evolution mechanism is proposed. The power conversion efficiency (PCE) value of the SnO(2) NT-TiO(2) core-shell structured DSSCs (～5.11%) is above five times higher than that of SnO(2) nanotube (SnO(2) NT) DSSCs (～0.99%). This PCE value is also higher than that of TiO(2) nanoparticles (P25) DSSCs (～4.82%), even though the amount of dye molecules adsorbed to the SnO(2) NT-TiO(2) photoanode is less than half of that in the P25 film. This simple procedure provides a new approach to achieve the three conflicting requirements simultaneously, which has been demonstrated as a promising strategy to obtain high-efficiency DSSCs.     

Synthesis of Nanosize-Necked Structure α- and γ-Fe2O3 and its Photocatalytic Activity

Highly dispersed nanometer-sized α-Fe₂O₃ (hematite) and γ-Fe₂O₃ (maghemite) iron oxide particles were synthesized by the combustion method. Ferric nitrate was used as a precursor. X-ray diffractometer study revealed the phase purity of α- and γ-Fe₂O₃. Both the products were characterized using field emission scanning electron microscope and transmission electron microscope for particle size and morphology. Necked structure particle morphology was observed for the first time in both the iron oxides. The particle size was observed in the range of 25–55 nm. Photodecomposition of H₂S for hydrogen generation was performed using α- and γ-Fe₂O₃. Good photocatalytic activity was obtained using α- and γ-Fe₂O₃ as photocatalysts under visible light irradiation.     

Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries

The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO(2)), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO(2)), where lithium ions are inserted/deinserted into/out of the TiO(2) crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs.     

Direct observation of melting behaviors at the nanoscale under electron beam and heat to form hollow nanostructures

We report the melting behaviours of ZnO nanowire by heating ZnO-Al(2)O(3) core-shell heterostructures to form Al(2)O(3) nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al(2)O(3) core-shell nanowire heterostructures were annealed at 600 °C under electron irradiation, the amorphous Al(2)O(3) shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s(-1). The thickness of the Al(2)O(3) nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al(2)O(3) nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM).     

微纳结构二氧化锡光催化剂的研究进展

二氧化锡是一种重要的无机半导体光催化材料,特别是具有不同形貌的微纳结构SnO_2,由于其粒子尺寸小,比表面积大,成为被广泛研究的光催化材料之一。简要介绍了SnO_2的晶体结构和光催化机理,综述了近年来具有不同形貌的微纳结构SnO_2光催化剂以及金属和金属氧化物掺杂的微纳结构SnO_2光催化剂的研究进展,并进一步指出了微纳结构SnO_2光催化剂研究中存在的问题和未来的研究方向。     

Fabrication of a transparent ultraviolet detector by using n-type Ga(2)O(3) and p-type Ga-doped SnO(2) core-shell nanowires

This study investigates the feasibility of synthesizing high-density transparent Ga(2)O(3)/SnO(2):Ga core-shell nanowires on a sapphire substrate at 1000 °C by VLS. The doping Ga concentrations are 0.46, 1.07, 2.30 and 17.53 atomic%. The XRD spectrum and HR-TEM reveal Ga(2)O(3) and SnO(2) as having monoclinic and tetragonal rutile structures, respectively. Experimental results indicate that the XRD peak shift of SnO(2) to a larger angle increases with the increasing amount of Ga doping. According to the CL spectrum, SnO(2) and Ga(2)O(3) peak at approximately 528-568 nm and 422-424 nm, respectively. The maximum quantum efficiency of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 0.362%. The UV light on-off current contrast ratio of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 1066.7 at a bias of 5 V. Moreover, the dynamic response of Ga(2)O(3)/SnO(2):Ga core-shell nanowires has an on-off current contrast ratio of around 16. Furthermore, the Ga(2)O(3) region functions similar to a capacitor and continues to accumulate SnO(2):Ga excited electrons under UV light exposure.     

Vertically building Zn2SnO4 nanowire arrays on stainless steel mesh toward fabrication of large-area, flexible dye-sensitized solar cells

Zn(2)SnO(4) nanowire arrays were for the first time grown onto a stainless steel mesh (SSM) in a binary ethylenediamine (En)/water solvent system using a solvothermal route. The morphology evolution following this reaction was carefully followed to understand the formation mechanism. The SSM-supported Zn(2)SnO(4) nanowire was utilized as a photoanode for fabrication of large-area (10 cm × 5 cm size as a typical sample), flexible dye-sensitized solar cells (DSSCs). The synthesized Zn(2)SnO(4) nanowires exhibit great bendability and flexibility, proving potential advantage over other metal oxide nanowires such as TiO(2), ZnO, and SnO(2) for application in flexible solar cells. Relative to the analogous Zn(2)SnO(4) nanoparticle-based flexible DSSCs, the nanowire geometry proves to enhance solar energy conversion efficiency through enhancement of electron transport. The bendable nature of the DSSCs without obvious degradation of efficiency and facile scale up gives the as-made flexible solar cell device potential for practical application.     

碳包覆金属氧化物作为超级电容器电极材料的研究进展

综述了碳包覆金属氧化物作为超级电容器电极材料的最新研究进展。详细介绍了贵重金属氧化物（如RuO2）和廉价金属氧化物（如Fe3O4、SnO2、TiO2、MnO2等）在超级电容器电极材料领域内的应用现状和存在的问题,指出了碳包覆廉价金属氧化物所形成的核/壳结构很好地解决了金属氧化物易溶于电解液、充放电体积易膨胀等问题,展望了其作为超级电容器电极材料在消费电子、航空航天、国防科技等领域中的应用前景。     

SnO2/ZnO复合中空纤维材料的制备及其光催化性能

采用天然棉花为模板制备了具有高光催化活性的SnO2/ZnO复合中空纤维光催化材料;利用X-射线衍射(XRD)、扫描电子显微镜(SEM)技术对其相结构和形貌进行了表征;以亚甲基蓝(MB)的脱色降解为模型反应,考察了Sn4+和Zn2+物质的量比为0.1∶1时煅烧温度对其催化性能的影响。实验结果表明:制备的样品为复制了棉花纤维模板形貌、具有中空结构的SnO2和ZnO半导体复合材料(SnO2/ZnO);煅烧温度对材料SnO2/ZnO的结晶度、晶粒大小﹑表面微结构和催化性能等有显著影响;650℃左右所得样品在太阳光下的催化活性最好,1 h可使MB溶液的脱色降解率达100%;该材料易于离心分离,具有良好的催化活性和重复使用性能。     

Cyclic voltammetric study of zinc and zinc oxide electrodes in 5.3 M KOH

The behaviour of zinc and zinc oxide in 5.3 M KOH in the presence of alkaline earth oxides, SnO, Ni(OH)₂ and Co(OH)₂ was examined by cyclic voltammetry. The influence of the alkaline earth oxides was compared with additives of established effects (Bi₂O₃, LiOH, Na₂CO₃ and CdO). The alkaline earth oxide each exhibits a distinct behaviour towards zincate. Whereas, a single process of interaction with zincate was shown by CaO; two modes of reaction were obtained with SrO and BaO. Solid solution formation was noticed with BeO and MgO. The other additives forming solid solution with ZnO were CdO, SnO. The ionic sizes of Ni(OH)₂ and Co(OH)₂ allow solid solution formation with Zn(OH)₂. Both Bi₂O₃ and Na₂CO₃ enter into complexation with zincate. LiOH forms two distinct zincates, of which one is an oxo zincate leaching the `hydroxyl' functionality. Cyclic voltammetry revealed the deposition of the oxide/hydroxide additives as metal prior to the onset of zinc deposition and the potential range for this additive metal deposition is almost the same for different additives (SnO, CdO, Ni(OH)₂). The beneficial action of these additives to zinc alkaline cells is associated with a substrate effect. The implication of this electrocatalytic deposition of metals on a zinc oxide electrode is also discussed.     

Preparation and characterization of magnetic nanofibers with iron oxide nanoparticles and poly(ethylene terephthalate)

Iron oxide nanoparticle/Poly(ethylene terephthalate) (PET) nanowebs were obtained by electrospinning. To achieve superparamagnetic properties, iron oxide nanoparticles with diameters below 25 nm were used. Diameter distribution of iron oxide nanoparticles was measured by a particle size analyzer. Iron oxide nanoparticles were added into 16 wt % PET solution in the ratio of 5, 10, and 15 wt % to PET. The morphology of iron oxide nanoparticle/PET nanowebs was observed using field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The nanofiber diameter increased as increasing iron oxide nanoparticle concentration. The superparamagnetic behavior of iron oxide nanoparticle/PET nanofiber was confirmed using superconducting quantum interference device (SQUID). The degree of crystallinity of iron oxide nanoparticle/PET nanowebs was calculated from a differential scanning calorimeter (DSC) results. The change of flexural rigidity and tensile properties of electrospun iron oxide nanoparticle/PET nanowebs with the external magnetic field were examined ISO 9073-7 testing method, universal testing machine and an appropriate magnet. Also, the elastic modulus of iron oxide nanoparticle/PET nanofiber was measured using nanoindentation. With applying magnetic field, the improvement in mechanical properties of field-responsive magnetic nanofibers and nanowebs was confirmed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication and characterization of zinc oxide nanoparticle coated magnetic iron oxide: Effect of S-layers adsorption on surface of oxide

Mixed zinc oxide nanoparticle coated magnetic iron oxide has been prepared by a sol–gel and co-precipitation routes. Magnetic iron oxide nanoparticles were synthesized by co-precipitation of ferric and ferrous ions with ammonia, and then zinc oxide was coated onto the surface of magnetic iron oxide by hydrolysis of zinc precursors. As a result, zinc oxide coated magnetic iron oxide nanoparticles with an average size of 68 nm were obtained. The crystalline bacterial cell surface layer)S-layer (used in this study was isolated from Lactobacillus helveticus ATCC 12046. The S-layer was adsorbed onto the surface of zinc oxide nanoparticle coated magnetic iron oxide. The nanoparticles were analyzed by X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM) were used to characterize the structural and the chemical features of the nanocomposites. The infrared spectra indicate that the S-layer-nanoparticle interaction occurs. This novel nanoparticle showed admirable potential in adsorption of S-layers on the surface of oxides for drug delivery.     

Catalytic performance of various mesoporous silicas modified with copper or iron oxides introduced by different ways in the selective reduction of NO by ammonia

Mesoporous silicas (MCM-48, SBA-15, MCF), reflecting various porous structures, were modified with copper and iron oxides by two different methods. For a first series of the samples the molecular designed dispersion (MDD) method using acetylacetonate complexes of copper and iron was applied for the deposition of transition metal oxides on the silica supports. A second series of the catalysts was obtained by the incipient impregnation technique using aqueous solutions of the suitable metal nitrates. The modified materials were characterized with respect to the texture (BET), composition (electron microprobe analysis), coordination of the transition metals (UV–vis–DRS) and surface acidity (NH₃-TPD, FTIR). The mesoporous silica supports modified with transition metal oxides were tested as catalysts of the selective reduction of NO with ammonia. The catalytic performance of the studied samples depended on the method used for the deposition of transition metal oxide as well as the kind of mesoporous silica used as a catalytic support. In general, the Cu-containing mesoporous samples effectively operated at lower temperatures than silicas modified with iron. The samples obtained by the MDD method have been found to be more active and selective compared to the analogous samples prepared by the impregnation technique. An introduction of water vapor into the reaction mixture only slightly decreased the NO conversion and selectivity towards N₂ over the MCF mesoporous silica modified with copper or iron oxide.     

Composite magnetic particles: 2. Encapsulation of iron oxide by surfactant-free emulsion polymerization

This is a second paper in the series concerning the synthesis and characterization of composite polymeric particles with encapsulated magnetic iron oxide and bearing reactive β-diketone groups on the surface. Composite particles have been prepared by two-step method in which first step requires preparation of the iron oxide nano-particles and during second step iron oxide was encapsulated into formed poly(styrene/acetoacetoxyethyl methacrylate) (PS-AAEM) particles directly during polymerization process. It has been found that the modification of the iron oxide nano-particle surface with sodium oleate improves significantly the encapsulation during polymerization process. This procedure gives a possibility to obtain composite particles with raspberry morphology and both the particle size and iron oxide content can be varied. Change of monomer to iron oxide ratio gives a possibility to change effectively the morphology of hybrid particles, however, polydispersity of composite particles increases at higher content of magnetic particles in the system. Variation of AAEM concentration in reaction mixture at constant iron oxide particles concentration gives a possibility to control the particle size of formed hybrid microspheres. Composite particles were characterized by dynamic light scattering and electron microscopy (SEM) with respect to their particle size and morphology of the surface layer. X-ray diffraction (XRD) and magnetization measurements indicate presence of maghemite (γ-Fe₂O₃) in composite particles.     

I. Adsorption mechanism of chlorophenols on iron oxides, titanium oxide and aluminum oxide as detected by infrared spectroscopy

The adsorption of 2-chlorophenol, 2,3- and 2,4-dichlorophenols and 2,4,6-trichlorophenol in liquid and gas phase on iron, titanium and aluminum oxides seem to proceed in a similar way. Higher adsorption of chlorophenols either from gas phase or from aqueous solution was observed on -Fe₂O₃ than on -FeOOH. The low adsorption of chlorophenols from aqueous solution on oxide surfaces suggests that hydrophobic chlorophenols cannot effectively compete with water for the absorption on hydrophilic oxide surface sites. The adsorption of chlorophenols on iron, titanium and aluminum oxides was followed by the adsorption isotherm, HPLC and diffuse reflectance FT-IR (DRIFT) spectroscopy. The adsorption of the chlorophenols on the oxides under study is related to the amount of interfacial water content on the iron oxide. The alumina–chlorophenolate surface complex was found to be weak when compared with either the iron or titanium analogs as seen by the C---O stretching vibrations, leading to a lower adsorption on alumina than on iron and titanium oxides.     

One-step hydrothermal synthesis of hybrid core-shell Co3O4@SnO2–SnO for supercapacitor electrodes

We successfully synthesized a novel core-shell hybrid metal oxide via a simple one-step hydrothermal method without annealing. This composite of Co₃O₄ particles covered with SnO₂–SnO (Co₃O₄@SnO₂–SnO) predicted better performance compared to pure Co₃O₄, which strongly depends on the synthetic temperature. The Co₃O₄@SnO₂–SnO prepared at a temperature of 250 °C (labeled Co₃O₄@SnO₂–SnO-250) exhibited an outstanding specific capacitance of 325 F g⁻¹ under the current density of 1 A g⁻¹, which was much higher than those of Co₃O₄ (12.6 F g⁻¹) and other composites. Additionally, the sample also exhibited good cycle stability performance with a retention rate of 100% after 5000 cycles at a current density of 5 A g⁻¹. Through X-ray photoelectron spectroscopy analysis, the presumed mechanism was that Sn-O_x decreases the surface electron densities of Co₃O₄, which is beneficial to OH⁻ adsorption and specific capacitance improvement, and the synthetic temperature had a strong impact on the microstructure and thus on the surface electron densities. The most.obvious finding to emerge from this study is that the specific capacitance can be improved through adjusting the surface electron densities of transition metal oxides.     

稀土固体超强酸SO42-/SnO2-Al2O3-Sm2O3的制备及其催化性能

采用沉淀-浸渍法制备了新型稀土固体超强酸SO42-/SnO2-Al2O3-SmO3,通过IR、TG等手段对其进行了表征分析,应用于合成丁醛乙二醇缩醛,考察其催化性能,较系统地研究了稀土氧化物种类、用量、焙烧温度、焙烧时间、浸渍液浓度等因素对产品收率的影响.实验结果表明适宜的催化剂制备条件为:稀土氧化钐含量为3%,焙烧温...     

Mesoporous hard-templated Me–Co [Me = Cu,Fe] spinel oxides for water gas shift reaction

Copper–cobalt and iron–cobalt oxides, as well as a cobalt oxide sample, were synthesized through the hard template (HT) route by using SBA-15 silica as the HT. Copper- and iron-containing materials with a Me/(Co + Me) atomic ratio of 9 and 17 mol% were obtained and characterized as to their structure, morphology, texture and redox properties by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N₂-physisorption and H₂-temperature programmed reduction, respectively. All the oxides were tested in a fixed-bed reactor for the water gas shift reaction in the 200–350 °C temperature range. All the catalysts showed a spinel structure, with the copper ions occupying exclusively the tetrahedral positions in the Cu–Co spinels and the iron ions being present in both tetrahedral and octahedral positions in the Fe–Co spinels. Segregation (to a minor extent) of maghemite phase was detected only for the high-concentration iron–cobalt oxide. The materials were replicas of the topological structure of the template, the channels being void replicas of the former walls of the SBA-15 host and the oxide appearing as nanorods, arranged in a highly ordered way in the case of Cu–Co oxides. Compared to Co₃O₄, the copper-containing and the iron-containing spinels were easier and harder to reduce, respectively. While the catalytic activity of cobalt and iron–cobalt spinels was rather poor, a remarkable water gas shift activity, accompanied (to a minor extent) by methanation, was observed over Cu–Co spinels. The influence of the reduction features on the catalytic performance is discussed.