聚合物-二氧化硅复合基材中CdS纳米晶的合成

本文报道在Sol-gel基材中制备由聚合物稳定的CdS纳米晶的新方法， 即通过甲基丙烯酸镉与甲基丙烯酸羟乙酯共聚合合成了含有Cd 2+的聚合物微凝胶, 在聚合物微凝胶网络中原位聚合正硅酸乙酯形成聚合物互穿的Sol-gel复合基材. 再向该聚合物/二氧化硅复合基材中通入H2S气体得到CdS纳米晶. 在聚合物网络中原位聚合正硅酸乙酯可以降低纯二氧化硅材料的脆性; 另一方面, 二氧化硅可以作为增强剂增加聚合物材料的强度. 因此, 在我们合成的聚合物/二氧化硅复合基材中制备的CdS纳米晶将具有很好的应用前景.     

Synthesis and crystal structure of a novel germanate: (NH4)4[(GeO2)3(GeO1.5F3)2].0.67H2O

The novel microporous germanate (NH4)4[(GeO2)3(GeO1.5F3)2].0.67H2O was prepared from an aqueous solution containing germanium dioxide, pyridine, hydrofluoric acid, and 2,6-diaminopyridine as a template. The solution was kept at 165 degrees C in a Teflon-lined autoclave for 4 days. Large crystals were produced and studied by X-ray powder diffraction, FTIR, thermal analysis, and elemental analysis. The structure was determined by single-crystal X-ray diffraction. The crystal is orthorhombic, space group Pbcn, with a = 7.0065(4) A, b = 11.7976(6) A, c = 19.5200(14) A, and Z = 4. The structure is a layered framework built up from GeO4 tetrahedral and GeO3F3 octahedral units. The polyhedral units are connected in such a way that they form a zeolite-like porous structure with three- and nine-membered rings. Half of the ammonium ions are located inside the nine-membered rings. The other half are above and below the three-membered rings. The connectivity of the germanium polyhedral units is interrupted along the c axis by ammonium ions and water molecules inserted between the layers.     

In-situ heating study on the structural change of surfactant-templated germanium oxide mesostructure

Mesostructured germanium oxide has been well-synthesized by using a surfactant-templated approach under basic hydrothermal conditions. The cationic surfactant cetyltrimethylammonium bromide (CTAB) has formed nanotubes with uniform diameter of about 3.2 nm. Blanket-like morphology of the as-prepared sample has been observed with transmission electron microscopy (TEM). High-resolution TEM image reveals that the nanotubes are connected with inorganic germanium oxide and have self-assembled into periodic mesostructure. In-situ heating X-ray diffraction (XRD) patterns confirm that the germanium oxide is in amorphous phase in the temperature range from room temperature (RT) to 700 degrees C. In-situ heating small-angle X-ray scattering (SAXS) presents the mesostructural change with temperature. The local atomic structures around germanium atom have been obtained with in-situ heating X-ray adsorption fine structure (XAFS) techniques. The stability of this mesostructure has been determined to be correlated with the cationic surfactant CTAB. The structural evolution from the GeO 2/NaOH aqueous solution, the as-prepared sample to the sample heated at 700 degrees C, has been described, and the formation mechanism of mesostructured germanium oxide has been discussed.     

Versatile biomimetic dendrimer templates used in the formation of TiO2 and GeO2

Biomimetic synthesis is emerging as an advantageous alternative to the harsh synthetic conditions traditionally used in metal oxide syntheses techniques. Silaffins, proteins from the C. fusiformis diatom, form silica in an aqueous environment under benign conditions. Amine terminated PAMAM and PPI dendrimers are effective mimics of silaffins and other silica precipitating polyamines. We have expanded the scope of dendrimer mediated metal oxide formation to include titanium dioxide, a photocatalyst, and germanium dioxide, a blue photoluminescent material. The nanoparticles were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (IR), and X-ray diffraction patterns (XRD). A variable temperature XRD analysis of TiO(2) nanoparticles was conducted to study the transition from anatase to rutile. TiO(2) nanoparticles synthesized in phosphate buffer showed a 200 degrees C decrease in the anatase to rutile transition temperature relative to TiO(2) templated in water. XRD analysis of GeO(2) nanoparticles in either water or phosphate buffer reveal crystalline alpha-phase germanium oxide. To our knowledge, this is the first report of the synthesis of crystalline GeO(2) under ambient conditions.     

Controllable growth of well-defined regular multiporphyrin array nanocrystals at the water-chloroform interface

On the basis of the coordination geometry of metal ions, regular cubic, clubbed, and wirelike nanocrystals of Cd(2+)-/PtCl(6)(2-)-mediated, and Hg(2+)-/Ag(+)-/PtCl(4)(2-)-mediated multiporphyrin arrays have been grown at the water-chloroform interface. The nanocrystal growth process was monitored by the transmission electron microscopy (TEM), which revealed (1) an intrinsic rule for coordination polymers, that is, the geometries of metal ions (as connects for the coordination polymers) dominate the frameworks of the related polymeric nanocrystals, and (2) one kind of intuitive nanocrystal growth processes at the interfaces. Both electron diffraction and X-ray diffraction patterns indicated the formation of well-defined nanocrystals. It was found that single-/microcrystals were formed at first, and then they grew into polycrystals. The nanocrystal layer was transferred onto Si and quartz substrate surfaces by the Langmuir-Blodgett method, with its composition analyzed by X-ray photoelectron spectroscopy as well as the arrangement of porphyrin macrocycles in the nanocrystals by UV-vis absorption spectroscopy.     

Self-assembled CuO nanoarchitectures and their catalytic activity in the thermal decomposition of ammonium perchlorate

CuO shuttle-like and flower-like nanocrystals were synthesized through a one-step, low-temperature solution-phase method in the presence of a cation surfactant, hexadecyl trimethyl ammonium bromide. These nanocrystals were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP). With the addition of CuO shuttle-like and flower-like nanocrystals, the thermal decomposition temperature of AP decreased. The structure, particle size, and morphology of resulting CuO powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis technique was applied to investigate the thermal decomposition of mixtures of AP and as-prepared CuO nanocrystals.     

Nanostructured polyamic acid membranes as novel electrode materials

This paper describes a new approach for the preparation of polyamic acid (PAA) composites containing Ag and Au nanoparticles. The composite film of PAA and metal particles were obtained upon electrodeposition of a PAA solution containing gold or silver salts with subsequent thermal treatment, while imidization to polyimide is prevented. The structural characterization of the films is provided by 1H NMR and Fourier transform infrared spectroscopy (FTIR), while the presence of metallic nanoparticles within the polymeric matrix was confirmed by scanning electron microscopy (SEM), cyclic voltammetry (CV), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This approach utilizes the unique reactivity of PAA by preventing the cyclization of the reactive soluble intermediate into polyimides at low temperature to design polymer-assisted nanostructured materials. The ability to prevent the cyclization process should enable the design of a new class of electrode materials by use of thermal reduction and/or electrodeposition.     

Selective decoration of nickel and nickel oxide nanocrystals on multiwalled carbon nanotubes

A simple route to selective decoration of nickel and nickel oxide nanocrystals on multiwalled carbon nanotubes (MWCNTs) using nickel acetylacetonate (NAA) was successfully achieved for the first time. The homogeneously decorated nanocrystals on MWCNTs were investigated for their structure and morphology by various techniques, such as powder X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, field emission scanning electron microscopy and thermogravimetric analysis. It was found that the size distributions of the nanocrystals on MWCNTs ranged from 8 to 15 nm and they were well resolved. The precursor, NAA, was effectively employed to impregnate the MWCNTs, which on calcination at suitable temperatures and in the presence of hydrogen and nitrogen atmosphere gave rise to nickel and nickel oxide nanocrystals, respectively.     

Preparation and characterization of palladium/polypyrrole-reduced graphene oxide/foamed nickel composite electrode and its electrochemical dechlorination of triclosan

In this study, a new composite electrode of palladium (Pd) nanoparticles dispersed on polypyrrole-reduced graphene oxide (PPy-rGO) loaded on foam-nickel was achieved by galvanostatic method. Characterization of structures, morphology and crystallinity of the synthesized materials were investigated by scanning electron microscopes (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results of XPS and XRD demonstrated Pd showed primarily as Pd0. From SEM and TEM results, we had seen that Pd nanoparticles were dispersible well on the composite electrode. Raman spectroscopy was used to show the state of graphene oxide and further demonstrated that PPy and rGO had existed of on the foam Ni matrix. The data of EIS also suggested the charge transfer of the new composite electrode decreased compared to Pd/PPy/foam-Ni and PPy/foam-Ni composite electrodes. The effect of the electropolymerization potential on Pd/PPy-rGO/foam-Ni electrode for removing triclosan (TCS) was examined. It was found that the removal efficiency of TCS on the composite electrode could reach 100% at electropolymerization potential of 0.7 V and reaction time of 100 min.     

Synthesis and characterization of core-shell selenium/carbon colloids and hollow carbon capsules

A novel Se/C nanocomposite with core-shell structures has been prepared through a facile one-pot microwave-induced hydrothermal process. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS).     

GeO2 fibers: preparation, morphology and photoluminescence property

Nanomicron to submicron fibers of GeO(2) have been prepared using poly(vinyl acetate) and germanium dioxide sol by electrospinning followed by high temperature calcination. The morphology of the fibers have been studied by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. X-ray diffraction indicates that the fibers are single crystal with hexagonal alpha-phase quartz-like structure. At room temperature, the fibers show photoluminescence under excitation at 325 nm. The fibers may have potential applications in one-dimensional optoelectronic nanodevices.     

Chelating ligand-mediated synthesis of hollow ZnS microspheres and its optical properties

Monodispersed hollow ZnS microspheres have been successfully synthesized by a facile ethylenediamine tetraacetic acid (EDTA) mediated hydrothermal route. The sizes of the hollow spheres vary from 1.5 to 3.5 microm when the reaction temperature varied from 130 to 230 degrees C. The formation of these hollow spheres is attributed to the oriented aggregation of ZnS nanocrystals around the gas-liquid interface between H(2)S and water. EDTA plays important role as chelating ligand and capping reagent, which regulates the release of Zn(2+) ions for the formation of ZnS hollow spheres. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy, photoluminescence, and Raman spectroscopy. The obtained ZnS hollow spheres show a sharp and photostable UV emission approximately 370 nm, which is attributed to the recombination process associated with interstitial sulfur vacancy.     

Sol–gel synthesis and crystallization behaviour of β-spodumene

Lithium aluminum silicate powders in the form of β-spodumene were synthesized through sol–gel technique by mixing boehmite sol, silica sol and lithium salt. The gel and oxide powders were characterized by thermogravimetry, differential thermal analysis (DTA), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy. DTA, XRD and FTIR results confirmed that crystallization of β-spodumene took place at about 800 °C. The tiny crystallites with average size less than 1 μm appeared when the gel powders were sintered at 800 °C. A substantial increase of the crystal grain size was observed with increasing sintering temperatures.     

Structure and properties of regenerated cellulose/tourmaline nanocrystal composite films

Nanocomposite films were successfully prepared from cellulose and tourmaline nanocrystals with mean diameters of 70 nm in a 1.5 M NaOH/0.65 M thiourea aqueous solution by coagulation with 5 wt % CaCl₂ and then a 3 wt % HCl aqueous solution for 2 min. The structure and properties of the composite films were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile testing. The results indicated that the tourmaline nanocrystals were dispersed in a cellulose matrix, maintaining the original structure of the nanocrystals in the composite films. The loss peaks (tan δ) in the DMA spectra and the decomposition temperatures in the DSC curves of the composite films were significantly shifted toward low temperatures, suggesting that the nanocrystals broke the partial intermolecular hydrogen bonds of cellulose, and this led to a reduction in the thermal stability. However, the nanocomposite films exhibited a homogeneous structure and dispersion of the nanocrystals. When the tourmaline content was in the range of 4–8 wt %, the composite films possessed good tensile strength (92–107 MPa) and exhibited obvious antibacterial action against Staphylococcus aureus. This work provides a potential way of preparing functional composite films or fibers from cellulose and nanoinorganic particles with NaOH/thiourea aqueous solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 367–373, 2004     

溶剂热法合成锐钛矿型二氧化钛纳米晶的形状演化规律

以钛酸四丁酯为前驱体,乙醇为溶剂,月桂酸和十二胺为共同稳定剂,采用溶剂热法制备了不同形状的锐钛矿型二氧化钛纳米晶。利用透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和热失重-差热分析(TG-DTA)等技术对纳米晶的结构、尺寸、形貌及形状进行了系统的表征,并探讨了月桂酸与十二胺不同配比时纳米晶的形状演化规律。结果表明:用溶剂热法在不同配比情况下获得的二氧化钛均为锐钛矿相;在月桂酸与十二胺总摩尔量不变的情况下,随着十二胺含量的增加,二氧化钛纳米晶的形状由球形逐渐演化为棒状,且结晶化程度在两者摩尔比为1:1时最好;月桂酸与十二胺稳定剂与纳米晶内核之间以桥接配位体的形式结合,且稳定剂在样品中的含量约为5%。     

SiO_2基底中MnFe_2O_4纳米晶的制备与表征

在N,N-二甲基甲酰胺(DMF)存在下,以溶胶-凝胶技术成功地制备了无定形二氧化硅基底中均匀分布的MnFe_2O_4纳米晶.由粉末X射线衍射和电子衍射确证了MnFe_2O_4纯相的生成. 由粉末X射线衍射和红外吸收光谱研究了MnFe_2O_4纳米晶形成过程.尖晶石结构的MnFe_2O_4在800℃时开始形成,900℃时基本完成.磁性质测量表明在烧结到900℃的样品中,MnFe_2O_4纳米晶室温具有超顺磁性,78K时为软磁性.1000℃ 和1100℃下得到的样品室温和78K时都具有软磁性.     

反应条件对ZnWO4纳米棒的形貌和光致发光性能的影响

采用水热法合成了ZnWO4纳米棒, 并用扫描电镜(SEM)、透射电镜(TEM)和粉末X射线衍射(XRD)等技术对产物进行了表征. 实验结果表明, 反应溶液的pH值和反应时间是影响ZnWO4纳米棒形成的重要因素. 研究了不同反应条件下制备的ZnWO4纳米晶的光致发光性能.     

Preparation of Cd-doped SnO<Subscript>2</Subscript> nanoparticles by sol–gel route and their optical properties

Nanocrystalline cadmium doped tin oxide (SnO₂) powders of about 2.5–4.5 nm in size have been synthesized by using different solvents via sol–gel method. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), Transmission electron spectroscopy (TEM), UV-Vis absorption and Photoluminescence (PL) spectroscopy. The PL emission spectra revealed that the band centered at 452 nm might be related with oxygen vacancies. A spherical, small rod and slice like morphologies of the prepared Cd-SnO₂ nanoparticles were observed in the SEM and TEM studies. The presence of Cd modifies the structural, morphological and optical properties of the tin oxide nanoparticles.     

The thermostability and reactivity of GaP nanocrystals in oxygen: from GaP nanocrystals to Ga2O3 nanocrystals

The thermostability and reactivity of GaP nanocrystals in O(2) were investigated using the thermogravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis techniques. alpha-Ga(2)O(3) nanoparticles, nano-hollow-particles, or nanorods and nanotubes can be separately obtained from the oxidation of nanocrystalline GaP at 400 degrees C for 30 min in dry O(2) atmosphere via manipulating different heating rates. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) analysis showed that the products were all alpha-Ga(2)O(3) but with different morphologies when different heating rates were applied. The formation mechanisms of the different morphological alpha-Ga(2)O(3) nanocrystals were discussed.     

Optical and Structural Studies of Chemically Synthesized ZnO Nanocrystals

ZnO nanocrystals were synthesized by adopting quenching method with Poly-vinyl alcohol as the matrix. X-ray diffraction, UV-vis spectroscopy, Photoluminescence, scanning electron microscopy, energy dispersive x-ray spectroscopy and transmission electron microscopy has been used to study the prepared samples. The size of the nanocrystals is in the range of 6.9 nm to 12.5 nm. We have successfully varied the size of the nanocrystals by varying the weight ratio of poly-vinyl alcohol and ZnO. The conductivity of the samples has been tested in atmospheric pressure as well as in vacuum.