Thermal stability and structural deformation of rutile SnO2 nanoparticles

Nanoparticles of rutile SnO₂ were synthesized by precipitation at room temperature. Samples were characterized with X-ray diffraction, transmission electron microscopy, thermoanalysis and nitrogen physisorption by BET method. The rutile crystalline structure was refined by Rietveld method. Crystallites had spherical morphology with crystallite sizes growing with the annealing temperature. The spherical crystallites aggregate to form grains composed of a number of crystallites defining the specific surface area and porosity. The crystallites contained hydroxyls in their structure and on their surface generating considerable amount of tin vacancy sites in the structure. These hydroxyls modify the Sn-O bonds, increase the lattice parameters and produce asymmetry in the representative rutile tin-oxygen octahedron. As the dehydroxylation was done with the annealing temperature, the atomic bond length between the oxygen atoms shared by adjacent octahedra decreased, contracting the lattice and increasing the symmetry.     

Synthesis of mesoporous silica materials with ascorbic acid as template via sol-gel process

Mesoporous silica materials with pore diameters of 2-5 nm have been prepared using ascorbic acid as a nonsurfactant template or pore-forming agent in HCl-catalyzed sol-gel reactions of tetraethylorthosilicate,followed by removing the ascorbic acid compound by extraction with ethanol.Characterization results from nitrogen sorption isotherm,powder X-ray diffraction and transmission electron microscopy indicate that the materials have large specific surface areas (e.g.1000 m2/g) and pore volumes (e.g.0.8 cm3/g).The rnesoporosity is arisen from interconnecting disordered wormlike channels and pores with relatively broad size distributions.As the ascorbic acid concentration is increased,the pore diameters and pore volumes of the materials increase.     

Facile assembly of mesoporous silica nanoparticles with hierarchical pore structure for CO2 capture

A facile one-pot hydrothermal approach has been developed for the preparation of mesoporous silica nanoparticles (MSNs) with hierarchical pore structure. The PEI-modified MSNs exhibit an improved adsorption capacity for CO₂ capture.     

Sensing mechanism of Pd-doped SnO2 sensor for LPG detection

In the present work, studies have been made to analyze the sensitivity, response, recovery time and sensing mechanism of Pd-doped thick film SnO₂ sensor for detection of LPG. To achieve this, thick film Pd-doped (0.25 and 1% by weight in available Indium doped SnO₂ thick film paste supplied by ESL, USA) along with an undoped (Indium doped) SnO₂ sensors were fabricated on a 1″ × 1″ alumina substrate. It consists of a gas sensitive layer (doped SnO₂), a pair of electrodes underneath the gas sensing layer serving as a contact pad for sensor. Also, a heater element on the backside of the substrate was printed for generating appropriate operating temperature at the substrate necessary for acquiring gas sensing properties. The sensor doped with 1% palladium showed the maximum sensitivity of 72% at 350 °C for 0.5% concentration of LPG. Possible detailed sensing mechanism of Pd-doped SnO₂ sensor for LPG detection has been proposed.     

Hierarchically porous Co3O4 film with mesoporous walls prepared via liquid crystalline template for supercapacitor application

Hierarchically porous Co₃O₄ film is prepared by a cathodic electrodeposition via liquid crystalline template. The as-prepared Co₃O₄ film has a net-like structure of interconnected nanoflakes with a thickness of 15–20 nm. Interestingly, the Co₃O₄ nanoflakes possess mesoporous walls ranging from 2 to 3 nm. As cathode material for supercapacitors, the hierarchically porous Co₃O₄ film exhibits superior supercapacitor performances with high specific capacitances (443 F g^{− 1} at 2 A g^{− 1} and 334 F g^{− 1} at 40 A g^{− 1}) as well as excellent cycle life, making it suitable for high-performance supercapacitor application. The improved supercapacitor performances are due to its unique hierarchically porous morphological characteristics, which provide fast ion and electron transfer, large reaction surface area, resulting in fast reaction kinetics.     

Structural and electrochemical properties of SnO2/nanocarbon families as lithium-ion battery anodes

Hybrid SnO₂/nanocarbon families (graphene nanosheets (GNSs), single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs) and carbon nanospheres (CNSs)) have been synthesized by a similar wet chemical method. SnO₂ nanoparticles are uniformly loaded on the surface of the nanocarbon families. As lithium battery anodes, their electrochemical properties of the reaction of lithium are investigated under the same conditions. To compare between them, SnO₂/GNSs have the largest capacity; SnO₂/GNSs and SnO₂/SWCNTs have high cyclability; and SnO₂/MWCNTs can maintain the capacity at high current density. Such behaviors are ascribed to their surface-to-volume ratio, structure flexibility, ion mobility and electron conductivity. The present results are the bases for their practical applications in lithium-ion battery anodes.     

Synthesis of morphology-controllable mesoporous Co3O4 and CeO2

Recently, extensive works have been devoted to the morphology control of mesoporous materials with respect to their use in various applications. In this paper, we used two kinds of mesoporous silica, SBA-15 rods and spheres as hard templates to synthesize morphology-controllable mesoporous metal oxides. By carefully controlling the loading of metal precursors in the mesopores of the hard template, mesoporous Co₃O₄ and CeO₂ with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were conveniently obtained. The structural properties of these materials were characterized by XRD, BET, SEM and TEM. In addition, it is found that the differences observed in the textural properties of the two mesoporous metal oxides nanocasted from the same template can be attributed to the properties of metal precursors and the interaction between metal oxide and SiO₂. Thus-obtained mesoporous metal oxides with such special morphologies may have a potential application in the field of environmental catalytic oxidation.     

One-pot synthesis of superacid catalytic material SO4/ZrO2-SiO2 with thermostable well-ordered mesoporous structure

A superacid mesostructured catalyst was directly synthesized by adding sulfuric acid to mesoporous zirconia-silica synthesis mixtures, and was characterized by HRTEM, XRD, UV-Vis, nitrogen sorption, NH₃-TPD, and Pyridine-FTIR. The XRD patterns and electron diffraction micrographs of the calcined samples showed the ordered mesoporous structure and tetragonal crystalline in frameworks. The ammonia TPD, pyridine in situ FTIR, and paraffin isomerization illustrated a new acidic property of the samples. The synthesis of the mesoporous materials, which have stable crystalline frameworks, high surface area, and strong acidity, is very likely to have important technological implications for catalytic reactions of large molecules.     

Preparation and photocatalytic activity of ZnO/TiO2/SnO2 mixture

ZnO/TiO₂/SnO₂ mixture was prepared by mixing its component solid oxides ZnO, TiO₂ and SnO₂ in the molar ratio of 4?1?1, followed by calcining the solid mixture at 200-1300 °C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO₂ and SnO₂ powders on the calcinations up to 600 °C. However, formation of the inverse spinel Zn₂TiO₄ and Zn₂SnO₄ was detected at 700-900 and 1100-1200 °C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn₂Ti_0.5Sn_0.5O₄ with an inverse spinel structure in the space group of . The ZnO/TiO₂/SnO₂ mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO₂, 2.0 times that of TiO₂, and 0.92 times that of ZnO after calcination at 500 °C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700 °C because of the formation of the photoinactive Zn₂TiO₄, Zn₂SnO₄ and Zn₂Ti_0.5Sn_0.5O₄. The sample became completely inert for the photocatalysis after prolonged calcination at 1300 °C (42 h), since all of the active component oxides were reacted to form the solid solution Zn₂Ti_0.5Sn_0.5O₄ with no photocatalytic activity.     

Synthesis of Au/SnO2 core-shell structure nanoparticles by a microwave-assisted method and their optical properties

Au/SnO₂ core-shell structure nanoparticles were synthesized using the microwave hydrothermal method. The optical and morphological properties of these particles were examined and compared with those obtained by the conventional hydrothermal method. In microwave preparation, the peak position of the UV-visible plasmon absorption band of Au nanoparticles was red-shifted from 520 to 543 nm, due to the formation of an SnO₂ shell. An SnO₂ shell formation was complete within 5 min. The thickness of the SnO₂ shell was 10-12 nm, and the primary particle size of SnO₂ crystallites was 3-5 nm. For the core-shell particles prepared by a conventional hydrothermal method, the shell formed over the entire synthesis period and was not as crystalline as those produced, using the microwave method. The relationship between the morphological and spectroscopic properties and the crystallinity of the SnO₂ shell are discussed.     

NO donors cis-[Ru(bpy)2(L)NO] and [Fe(CN)4(L)NO] complexes immobilized on modified mesoporous silica spheres

The reaction of [Ru(bpy)₂Cl₂] and Na₂[Fe(CN)₄(dmso)₂] complexes with isonicotinic acid immobilized on silica spheres (Si-ATPS-ISN) followed by a NO bubbling produced Si-ATPS-ISN-[Ru(bpy)₂(NO)] (system I) and Si-ATPS-ISN-[Fe(CN)₄(NO)] (system II). The characterization of these systems was carried out by UV–Vis, FTIR spectroscopy and electrochemical techniques. As judged by the FTIR data, the nitric oxide ligand has an NO⁺ character in both systems (ν(NO⁺): 1938 cm⁻¹). The NO release, which was monitored by means of FTIR, electrochemistry, and NO sensor electrode, was observed for both systems upon white light irradiation and chemical reduction by cysteine. These results indicated that the system (II) presents a higher potential for controlled NO release. The characterization (FTIR and UV–Vis) of the systems after the NO release suggested the formation of the aqua systems ATPS-ISN-[Ru(bpy)₂(OH₂)] and ATPS-ISN-[Ru(bpy)₂(OH₂)].     

High-temperature synthesis of highly hydrothermal stable mesoporous silica and Fe-SiO2 using ionic liquid as a template

Mesoporous silicas and Fe-SiO₂ with worm-like structures have been synthesized using a room temperature ionic liquid, 1-hexadecane-3-methylimidazolium bromide, as a template at a high aging temperature (150-190 °C) with the assistance of NaF. The hydrothermal stability of mesoporous silica was effectively improved by increasing the aging temperature and adding NaF to the synthesis gel. High hydrothermally stable mesoporous silica was obtained after being aged at 190 °C in the presence of NaF, which endured the hydrothermal treatment in boiling water at least for 10 d or steam treatment at 600 °C for 6 h. The ultra hydrothermal stability could be attributed to its high degree of polymerization of silicate. Furthermore, highly hydrothermal stable mesoporous Fe-SiO₂ has been synthesized, which still remained its mesostructure after being hydrothermally treated at 100 °C for 12 d or steam-treated at 600 °C for 6 h.     

Preparation and application of Ce-doped mesoporous TiO2oxide

Summary Mesoporous TiO₂-CeO₂mixed oxides (m-TiO₂-CeO₂) were synthesized under easy-operating neutral conditions. The structure was characterized by means of FT-IR, XRD, and N₂adsorption methods. For methanol decomposition to CO and H₂, the catalytic activity of the Ru/ m-TiO₂-CeO₂ catalyst was higher than that of the Ru/ m-TiO₂.</o:p>     

硬模板法制备固体氧化物燃料电池Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x包覆管状SDC立体阳极

为在固体氧化物燃料电池中有效利用干甲烷为燃料,需制作多孔立体阳极。采用硬模板法和浸渍法制备Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x包覆管状SDC阳极材料(Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x/SDC),为作对比,用溶胶凝胶法制备粉末状Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x,机械混合SDC粉末制备Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x-SDC。将这两种阳极材料分别制作电解质支撑的单电池Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x/SDC|YSZ|LSMYSZ与Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x-SDC|YSZ|LSM-YSZ,并进行发电性能测试以及长期稳定性实验。结果表明,800℃下,干甲烷环境中,Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x-SDC为阳极的单电池最大功率密度为324.99 m W/cm2,运行10 h后,电压下降5.60%;而以Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x/SDC为阳极的单电池最大功率密度达到384.54 m W/cm2,运行100 h后,电压未严重衰减。实验后阳极的SEM照片表明,Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x-SDC阳极内孔隙狭小,易被积炭堵塞;而Ni_(0.5)Cu_(0.5)Ba_(0.05)O_x/SDC阳极呈立体多孔结构,有利于燃料气体与反应后气体的扩散。催化剂颗粒均匀地包覆在SDC纤维管表面,有利于增加三相界面,提高电池的稳定性。     

Na2SO4辅助水热合成SnO2纳米晶

系统地研究了以SnCl₄·5H₂O为原料，以Na₂SO₄为矿化剂，采用水热法在较低温度下和较短的反应时间内制备结晶良好并均匀分散的SnO₂纳米晶。采用X射线衍射(XRD)、透射电子显微镜(TEM)、红外光谱(IR)等技术对水热反应的晶化过程进行了分析。结果表明：在Na₂SO₄存在的情况下，在120 ℃反应4 h 即可制备得到晶粒细小，分散性能良好的SnO₂纳米晶。XRD衍射峰峰宽随水热温度的升高或反应时间的延长而变窄，结晶性提高。TEM结果表明产物颗粒小、分散性能良好。水热反应温度和反应时间对产物结晶度和粒径有明显的影响。对Na₂SO₄在反应过程中的作用机理进行了分析。     

A one-pot synthetic approach to prepare palladium nanoparticles embedded hierarchically porous TiO2 hollow spheres for hydrogen peroxide sensing

A simple one-step method to fabricate hierarchically porous TiO₂/Pd composite hollow spheres without any template was developed by using solvothermal treatment. Pd nanoparticles (2-5 nm) were well dispersed in the mesopores of the TiO₂ hollow spheres via in-situ reduction. In our experiment, polyvinylpyrrolidone played an important role in the synthetic process as the reducing agent and the connective material between TiO₂ and Pd nanoparticles. HF species generated from solvothermal reaction leaded to the formation of TiO₂ hollow spheres and Ostwald ripening was another main factor that affected the size and structure of the hollow spheres. The as-prepared TiO₂/Pd composite hollow spheres exhibited high electrocatalytic activity towards the reduction of H₂O₂. The sensitivity was about 226.72 μA mM⁻¹ cm⁻² with a detection limit of 3.81 μM at a signal-to-noise ratio of 3. These results made the hierarchically porous TiO₂/Pd composite a promising platform for fabricating new nonenzymic biosensors.     

SnO2纳米带的水辅助生长与表征

以高纯Sn粉为原料，采用水辅助生长法在850 ℃下合成了SnO₂纳米带，用SEM、TEM、XRD、EDX、 HRTEM和SAED对其形貌、结构和成份进行了表征，对SnO₂纳米带的光致发光和红外谱图进行了分析，探讨了水辅助生长SnO₂ 纳米带的化学原理和生长机制。结果表明：用水辅助生长法制备的SnO₂纳米带产量高、结构均匀，XRD衍射图与SnO₂的标准图完全一致，纳米带的宽度为70～100 nm，厚度为5～8 nm,长度可达数十微米；SnO₂纳米带光致发光在617 nm和651 nm处有2个强峰，在446 nm处有一个弱峰，这些都是由氧空位引起的；SnO₂纳米带的红外谱图中560.6 cm^-1处的峰属于表面振动模式；水辅助生长SnO₂纳米带的可能机制是VS生长机制。     

Electrorheological behavior of urea-doped mesoporous TiO2 suspensions

A type of anhydrous electrorheological (ER) material of urea-doped mesoporous TiO₂ is synthesized by in micelle-assisted incorporation urea molecules during mesoporous TiO₂ synthesis. TEM, XRD demonstrate that the material had mesoporous structure, while the FT-IR spectra and the nitrogen adsorption–desorption isotherms show urea molecules have been fixed in the channel of the mesoporous TiO₂. The ER behavior of the suspensions of urea-doped mesoporous TiO₂ in silicone oil with the different volume fractions was investigated under an applied electric field. It is found that the suspensions show visible electrorheological behavior which are compared with that of pure TiO₂. The dopants of urea molecules change the conductivity of the particles, and produce a proper conductivity of 10⁻⁷ S m⁻¹ with the molar ratio of urea/Ti = 0.2. Dielectric spectra of the ER fluid was measured to examine the peak of ″ should appear in the frequency range of 10²–10⁵ Hz and have a large Δ′ in this frequency range. The interfacial particle polarization model can exactly explain the ER behavior of this material.     

Acidity enhancement of SBA mesoporous molecular sieve by modification with SO4/ZrO2

The SO₄²⁻/ZrO₂ modified SBA mesoporous molecular sieves were prepared and characterized by XRD, N₂ adsorption, TG/DTG/DTA and IR pyridine chemisorption. The acidity of the molecular sieve was greatly enhanced after modification, and IR pyridine chemisorption results revealed that Lewis acidity was dominant in these samples. The catalytic activities of the modified molecular sieves towards strong and medium strong acid catalyzed reactions were lower than those of bulk SO₄²⁻/ZrO₂, but higher than those of Al-containing SBA molecular sieve from direct synthesis, whereas the activities of all these catalysts for weak acid catalyzed reaction were close to each other.     

Preparation of few-layer reduced graphene oxide-wrapped mesoporous Li4Ti5O12 spheres and its application as an anode material for lithium-ion batteries

A three-dimensional few-layer reduced graphene oxide-wrapped mesoporous Li₄Ti₅O₁₂ (m-LTO@FLRGO) electrode is produced using a simple solution fabrication process. When tested as an anode for Liion batteries, the m-LTO@FL-RGO composite exhibits excellent rate capability and superior cycle life. The capacity of m-LTO@FL-RGO reaches 165.4 mA h g^-1 after 100 cycles between 1 and 2.5 V at a rate of 1 C. Even at a rate of 30 C, a high discharge capacity of 115.1 mA h g^-1 is still obtained, which is three times higher than the pristine mesoporous Li₄Ti₅O₁₂ (m-LTO). The graphene nanosheets are incorporated into the m-LTO microspheres homogenously, which provide a high conductive network for electron transportation.