Controllable Synthesis of Titania Nanocrystals with Different Morphologies and Application to the Degradation of Phenol

Titania nanocrystals with different morphologies were prepared using the hydrothermal method via controlling the pH values of solution, the ratio of reactants, temperature, and time of the hydrothermal reaction. The experimental results showed that uniform rod-like titania particles with an average aspect ratio of 6：1 could be obtained under the conditions of pH=11, n（TBOT）：n（TEA）=1：2, hydrothermal treatment at 150 °C for 24 h. When pH〈10, spherical titania nanocrystals could be obtained; with increasing the pH value, the diameter became smaller. Finally, the smallest size of the particles could reach 7 nm. Nanocrystals with uniformly well-dispersed and perfect crystallographic form were obtained via the above method. Phenol was used as the degradation model for testing the photocatalytical activity of the titania nanocrystals with different morphologies.     

SnO2纳米粒子的制备与表征

The SnO2 nano-particles with rutile structure were prepared by a Water/Oil (W/O) microemulsion system, composed of Triton X-100 1-hexanol/Cyclohexane/Water. The particles were also compared with that synthesized by citric acid method. The powders were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and infrared spectroscopy (IR). The result showed that the SnO2 particles prepared by microemulsion had fine shape and narrow range of particle size distribution. The crystallite size calcined at 600℃ was 11.49 nm,while the crystallite size prepared by citric acid method was about 17.4 nm.     

Forming and Gathering of SnO2 Nanoparticles on External Surface of High Silica TON, MFI and FAU Type Zeolites

Tin dioxide （SnO2） nano-particles were prepared on high silica TON, MFI and FAU type zeolites by impregnation of SnC12 solution and subsequent calcination at 873 K. XRD and SAED were used to characterize the crystalline phase, and TEM was used to characterize the morphology, the particle size and the agglomerative state of the formed nano-materials. The nano-particles, which possess 8 nm, 10-80 nm and 6 nm in size, were found to form on the outer surface of TON, MFI and FAU zeolites, respectively. SnO2 microcapsules and SnOz netlike nanostructure were obtained by decomposition of SnO2-TON and SnO2-MFI in 40% hydrofluoric acid at room temperature. Compared with the nano-particles formed on NaY zeolite, the special morphology and the agglomerative state of SnO2 nanostructures on TON and MFI type zeolites with one and two dimension channel system indicate that the heterogeneous framework, surface structure and property perform important function for forming and growing SnO2 nanostructure on the outer surface of the zeolites.     

纳米CuO的形貌控制合成及其性能研究

The CuO nanocrystals were prepared by quick-precipitation and hydrolysis method respectively, using Cu(Ac)₂ and NaOH as starting materials. The as-prepared CuO nanocrystals were characterized by XRD, TEM, XPS, UV-Visible absorption spectroscopy and BET. The catalysis of CuO nanocrystals of different morphologies on ammonium perchlorate decomposition was investigated by thermal analysis. Results indicated the variation in temperature for NaOH addition played an important role in the shape of the CuO nanocrystals in precipitation method. Well-dispersed spherical CuO nanocrystals with an average size of 6 nm could be obtained when NaOH was added at 100 ℃ and spindle-shaped CuO nanocrystals exceeding 100 nm in diameter were obtained when NaOH was added at room temperature. Needle-shaped CuO nanocrystals could be prepared by the hydrolysis method, and the presence of small amounts of cetyltrimethylammonium bromide (CTAB) could make needle-shaped CuO well dispersed. The catalytic activity of CuO nanocrystals of different morphologies on ammonium perchlorate decomposition was high. The 2% of spherical CuO nanocrystals could make higher decomposition temperature of ammonium perchlorate decreased to 102 ℃. The exothermic quantity of decomposition was from 590 J·g^-1 up to 1 420 J·g^-1.     

Effect of Particle Size and Capping on Photoluminescence Quantum Efficiency of 1,3,5-Triphenyl-2-pyrazoline Nanocrystals

Organic nanocrystals of 1,3,5-triphenyl-2-pyrazoline(TPP) with a series of sizes were synthesized by reprecipitation method.The luminescence quantum efficiency of TPP nanocrystals increases from 24.2% for the nanocrystals with an average size of 300nm to 34.6% for those with an average size of 20nm.Surface capping by polyvinyl pyrrolidone(PVP) will improve the quantum efficiency of TPP nanocrystals.The size-dependence and capping-induced variation of the luminescence quantum efficiency was elucidated in viewpoint of aggregation quenching and the equilibrium between the TPP monomers and the aggregates in TPP nanocrystals.     

Synthesis of nanosize europium oxide particles by using W/O microemulsion

Europium hydroxide particles with an average diameter of 10 run and a BET surface area of 127 m2 /g have been prepared by controlled precipitation in the polyoxyethylene octylphenol (Triton X-100) (hex-anol)/cyclohexane/water microemulsion system. After calcination in air at 750℃, the obtained europium hydroxide particles were readily converted to the nanosize Eu2O3 particles with an average size of 30 nm and a high BET surface area of 36.5 m2/g.     

Synthesis and Characterization of CdSe Nanocrystals Capped by CdS

CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2-mercaptoethanol as the stabilizer. The CdS capping with a higher band-gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band-edge photoluminescence. X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.     

A novel rose flower-like SnO hierarchical structure synthesized by a hydrothermal method in an ethanol/water system

Rose flower-like SnO hierarchical 3D architectures consisting of well-ordered microsheets were synthesized by a template-free and surfactant-free hydrothermal method based on the reaction between SnCl2 and NaOH in ethanol/water. The ethanol amount is a crucial factor in controlling the size and morphology of the microsheets. Ethanol can accelerate the delamination of the SnO blocks to the microsheets, and the microsheets changed from a quasi square to an octodecahedral shape with the increase of the ethanol ratio. When the volume ratio of ethanol/water is 2：1, the microstructure of SnO presents a rose flower-like hierarchical architecture with a diameter of about 40 μm, which is regularly composed of numerous well-ordered thin microsheets with octodecahedral shape, and the microsheets were formed by countless nanoparticles. A possible growth mechanism of the architectures was proposed. Moreover, SnO2 nanospheres were synthesized by a similar experiment only without NaOH, which showed that NaOH was crucial to the formation of SnOx.     

球形Gd2O3∶Eu纳米发光材料的制备

Spherical nanometer Gd₂O₃∶Eu luminescent materials were prepared by homogeneous precipitation method, and the properties were studied also. TG, FTIR and XRD analysis showed that the precursor was carbonate, the cubic Gd₂O₃was obtained after calcination. TEM photographs indicated that the samples were spherical and well dispersed with nanometer and submicrometer size of 200～300 nm which is the nanoparticles’ aggregate. The mechanics of agglomerating growth is also discussed. ED photograph showed that the particle was crystalline. The PL analysis exhibited that CTB band of nanometer Gd₂O₃∶Eu was of 17 nm red shift to bulk materials, and the emission peak was broadened due to the surface and interface effect of nanocrystals.     

水热法制备高纯超细CeO2-ZrO2复合氧化物

Superfine composite powders of CeO₂-ZrO₂ (CZ) and CeO₂-ZrO₂-La₂O₃ (CZL) were prepared by hydrothermal method. The effects of pH、temperature and time for hydrothermal process on the performance of the resulting powders were studied. The optimized reaction parameters were on follows: the precursor′s pH≈9.0, hydrothermal temperature of 200 ℃ holding for 2 h. Thermal stable powders with average particle size smaller than 10 nm and specific surface area of 171 m²·g^-1 were obtained. A BET specific surface area was still at 44 m²·g^-1 after calcination at 1 000 ℃ for 6 hours.     

立方形貌ITO粉体的水热法制备及光电性能

以金属In和SnCl_4·5H_2O为原料,采用水热法在120~140℃得到In(OH)_3前驱体,该前驱体在550℃下煅烧得到立方体形貌的氧化铟锡粉体.研究了水热反应温度和反应时间对粉体形貌和晶型的影响.通过热分析仪(TG-DSC)、X射线衍射仪(XRD)、拉曼光谱仪(Raman)、透射电子显微镜(TEM)、四探针电阻仪、X射线光电子能谱仪(XPS)、紫外-可见-近红外分光光度计以及荧光光谱仪对粉体进行了表征,并对水热反应条件为140℃及12 h下制备的c-ITO的光电性能进行了分析.结果表明,随着水热反应温度的升高,ITO粉体形貌由立方体向不规则形貌转变,粉体晶型出现少量的六方相.在水热反应条件为140℃,12 h,铟离子与尿素的摩尔比为1∶5时,得到平均粒径为230 nm的立方体ITO粉体,其电阻率为1.247Ω·cm,光学能带间隙为3.685 e V,与c-In2O3相比其能带间隙更高,室温下260 nm激发波长下粉体出现光致发光,发射峰位于蓝光区域.     

Preparation of band gap tunable SnO2 nanotubes and their ethanol sensing properties

SnO(2) nanotubes have been prepared via a facile hydrothermal method at low temperatures using polycarbonate (PC) membrane as a hard template. The walls of as-prepared SnO(2) nanotubes are composed of fine nanocrysalline particles and the size of SnO(2) nanocrystals could be modified by changing reaction temperature. Formation mechanism of SnO(2) nanotubes is also discussed according to the experimental results. Cathodoluminescence properties of the SnO(2) product indicated that the band gap of the nanostructures increase from 3.75 eV with a particle size 5.6 nm to 3.99 eV with a particle size 3.3 nm. The as-prepared SnO(2) nanotubes were found to show enhanced gas-sensing activity and may be used as a candidate for the fabrication of gas sensors.     

SnO2/GDE阴极的制备及电催化还原CO2产甲酸性能

采用低温水热合成法制备了碳纸基底的SnO₂气体扩散电极(SnO₂/GDE), 并对其物化特性与催化还原CO₂产甲酸性能进行了研究. 扫描电子显微镜、 X射线衍射及X射线光电子能谱表征结果表明, 在60, 75, 100 ℃下制备的催化剂均为分散性良好的纳米SnO₂粉体, 其粒径分别为7.9, 11.8和12.9 nm. 循环伏安、 线性扫描伏安和电化学交流阻抗测试结果显示电极均具有优异的电催化活性, 其电化学活性表面积分别为150, 470, 240 cm ², 通过等效电路拟合后电阻分别为8.5, 3.9, 6.6 Ω·cm ². 在-1.8 V(vs. SCE)电位下电解, 通入电量500 C时, 电极都具有较高电催化还原CO₂产甲酸性能, 而75 ℃下制备的电极性能最佳, 产甲酸电流密度为22.8 mA/cm ² , 产甲酸法拉第效率高达93.5%; 该电极经过20 h长时间电解后, 产甲酸电流密度可维持在12.8 mA/cm ² , 产甲酸法拉第效率稳定在约65%.     

纳米SnO2的制备

ＳｎＯ２在陶瓷、气敏半导体材料及催化剂等方面被广泛应用［１］．纳米级的ＳｎＯ２因具有明显的表面效应而受到关注，其制备方法也受到重视［２］．纳米ＳｎＯ２的制备方法较多，有沉淀法［２］、水热法［３，４］、溶胶－凝胶法［５］、火焰合成法［６］等．然而要制备...     

阴离子表面活性剂辅助模板途径合成介孔结构氧化锆纳米晶

利用阴离子表面活性剂十二烷基磺酸钠(SDS)为辅助模板剂, 成功地合成了高稳定性的介孔氧化锆纳米晶, 采用DSC-TG, FT-IR, XRD, TEM, UV-Vis以及N₂吸附-脱附等方法对样品进行了表征. 研究表明, 以阴离子型十二烷基磺酸钠合成的氧化锆经600 ℃煅烧后仍为纯四方相, 氧化锆晶粒平均尺寸约为6.5 nm. 阴离子型表面活性剂与有机锆源形成自组装协同作用, 合成的氧化锆具有蠕虫状介孔结构, 经过500 ℃煅烧后介孔结构仍然保持, 且由于表面活性剂的去除, 比表面积显著提高, 显示了良好的热稳定性. 本实验制备的氧化锆纳米晶较一般方法制备的市售纳米氧化锆有明显紫外吸收边蓝移现象.     

铁改性水滑石基Pt/BaO/MgFeO催化剂焙烧温度对催化剂结构及NO_x吸附-还原性能的影响

采用共沉淀法和浸渍法制备了贵金属负载均匀的镁铁水滑石基稀燃氮氧化物捕集(LNT)催化剂,并采用多种表征手段研究了焙烧温度对催化剂结构及NO_x吸附-还原反应的影响。结果表明,500-700℃焙烧后催化剂晶相结构稳定,800℃焙烧后催化剂表面出现烧结,Pt颗粒发生团聚;随焙烧温度升高,催化剂的NO_x脱附峰面积先减小后增大,但峰值温度变化不大;与500℃焙烧催化剂相比,800℃焙烧后催化剂表面NO_x吸附物种及吸附路径发生改变,而还原反应产物中氨气/氮气体积比下降,NO_x转化效率由91.7%降为85.2%。     

纳米二氧化钛的制备及其光催化性能

分别采用水热法和溶胶-凝胶法制备了TiO2纳米粉体;利用X射线衍射仪和扫描电镜分析了两种方法制备的TiO2粉体的形貌和晶体结构,并测定了纳米TiO2粉体对罗丹明B的光催化降解活性.结果表明:采用水热法制备的TiO2纳米粉体含有锐钛矿相和金红石相,粒径较小,大约为50nm,而且分散均匀,光催化性能良好;采用溶胶-凝胶法制备的TiO2粉体经过550℃煅烧后仍然为锐钛矿相,而且粒径较大,大约为80nm.     

模板水热法纳米TiO2制备及光催化性能研究

以聚乙烯吡咯烷酮(PVP)为模板剂,钛酸四正丁酯(TBOT)为钛源,水热法制备纳米TiO2。采用XRD,SEM、TEM和UV-Vis DRS等测试手段对其形貌和结构进行表征。通过对甲基橙的光催化降解实验,探讨了焙烧温度、催化剂用量和溶液pH值对光催化性能的影响。结果表明,TiO2具有锐钛矿相,平均晶粒尺寸约为23.2 nm,TiO2颗粒呈片层状或由片层状堆积的疏松圆球形,经超声后即分散为八面体晶粒。550℃焙烧的样品,紫外光照3 h后,对甲基橙的降解率可达84.2%。相比普通水热法,采用模板剂法制得的TiO2吸收带发生红移,因而也具有较好的可见光催化活性。     

GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质

采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。