One step synthesis of silica-coated nanoparticles at room temperature and their luminescence properties

A novel one-step preparation method for core-shell CdS/SiO₂ nanoparticles was proposed using 3-mercaptopropyl-trimethoxysilane (MPS) as stabilizing agent in MeOH, in which CdCl₂·2.5H₂O and Na₂S·9H₂O were used as the source of Cd and S, respectively. And the photostability of the nanoparticles was further investigated. The morphology and structure of products was characterized by scanning probe microscope and FT-IR spectra, respectively. Furthermore, the influences of Zn and Cu doped in the products, individually, on the fluorescence property were discussed. The results showed that the products were ball-shaped and silica-coated with a uniform size, the spectra of Zn-doped was blue shifted, however, the spectra of Cu-doped was red shifted, the core-shell CdS/SiO₂ nanoparticles was more steady compared with thioglycolic acid-capped CdS nanoparticles.     

纳米金红石TiO2粉体的低温制备

介绍了用加添加剂水解的办法制备纳米金红石TiO2,并用TEM、BET、XRD等仪器测试了样品的大小、晶型、形貌和比表面积。在室温经真空干燥,即得到金红石型TiO2,将样品从室温加热到600℃,可得到10－30nm大小、比表面积为160－50m^2／g的纳米金红石TiO2。     

纳米TiO2粉体的低温制备

采用液相沉积法制备锐钛矿型TiO2纳米光催化粉体,研究了沉积温度、反应物的摩尔比、沉积时间、[TiF6]^2-水溶液的浓度等对TiO2粉体性能的影响。用甲基橙的光催化降解表征了所制备的TiO2粉体的光催化活性。结果表明光催化活性最佳的实验参数为：温度为90℃,(NH4)2TiF6与H3BO3的摩尔比为1：2。5,沉积时间为1h,加水量为320ml。     

Synthesis and investigations of rutile phase nanoparticles of TiO2

TiO₂ nanoparticles have been synthesized at room temperature using a simple chemical precipitation route. Particles were further coated with polymer. Detailed structural analysis of the particles has been carried out. Wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) confirm that as-synthesized particles as well as annealed particles are nanoparticles having pure rutile phase. Thermal annealing at 1000 °C of 4.2 nm particles led to an increased size 20 nm in the same phase. The purity and composition of the particles were determined using energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS), respectively.     

Study on photocatalysis of TiO 2 nanotubes prepared by methanol-thermal synthesis at low temperature

TiO₂ nanotubes were synthesized by the solvothermal process at low temperature in a highly alkaline water–methanol mixed solution. Their characteristics were identified by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), specific surface area (BET), Fourier transform infrared spectroscopy (FTIR) and UV–Vis absorption spectroscopy. The as-prepared samples were tested by the photodegradation reaction of methylene blue (MB) dye under visible-light irradiation. The ratios of methanol and water, as well as calcination temperature, affected the morphology, nanostructure and photocatalytic performance. The methanol solvent plays an important role in improving crystallization of the anatase phase, which affects the photocatalytic reaction. Titanate nanotubes were synthesized in methanol–water volume ratios of 10:90, 20:80 and 30:70 which still had high absorbability. Titania nanotubes formed at a calcination temperature of 300 °C using methanol–water volume ratio of 30:70 showed highest photocatalytic performance, much higher than that using water solvent and TiO₂–P25 powder.     

纳米TiO2薄膜的低温制备与光谱特性研究

以钛酸丁酯为原料,采用改进溶胶-凝胶法,通过浸渍-提拉工艺在低温条件下制备了锐钛矿纳米TiO2薄膜。利用X射线衍射、紫外-可见光吸收光谱、傅里叶变换红外光谱对所制备的TiO2薄膜的晶型结构和光谱特性进行了分析,并利用紫外光照降解亚甲基蓝溶液来评价所制备薄膜的光催化活性。结果表明:经过陈化和水浴处理后,钛酸丁酯完全水解,所得TiO2薄膜为锐钛矿结构,对紫外光表现出较强的吸收特性。低温水浴处理有利于提高薄膜的光催化活性。     

酸在制备金红石型纳米TiO2中的作用

以成本低廉的偏钛酸和浓硫酸为起始反应物,采用水热合成法进行了纳米金红石型TiO2的合成研究.研究了制备过程中浓硫酸对偏钛酸的溶解情况,以及水热反应的pH值对TiO2晶型转变的影响.结果表明:只有当偏钛酸完全溶解,并且水热反应时的pH小于等于0.4时,才能制得纯相的金红石型TiO2.     

低温制备混晶TiO2纳米粒子及其光催化性能研究

通过低温液相合成混合晶型纳米TiO2颗粒,研究纳米TiO2颗粒的光催化活性与颗粒晶相组成之间关系.用XRD对其进行表征,并在紫外光下,以甲基橙光催化降解为模型反应,研究了不同晶相样品的光催化活性.结果表明:混合晶相中锐钛矿质量分数占69.8%、金红石质量分数占30.2%,TiO2光催化效用最好可达95.7%.     

Room temperature synthesis of rutile TiO2 hierarchical nanoneedle flower morphology for dye sensitized solar cell

Rutile TiO2 nanoneedle flowers (representing concurrent nano-micro hierarchical morphology) with high shape anisotropy ratio are synthesized at room temperature by using a simple and efficient one step electrochemical process of anodic dissolution. This process employs highly acidic bath of perchloric acid (pH <2) and a large current density on the surface of Titanium foil to form nanostructures. The diameter and length of rutile TiO2 nanoneedle is approximately 8 nm and 100 nm respectively (aspect ratio >10). Dye sensitized solar cell (DSSC) configured using such rutile TiO2 flowers is shown to exhibit IPCE of 30% and power conversion efficiency of approximately 3.6%.     

纳米金红石型二氧化钛的低温制备及表征

采用不同高浓度的硝酸对由TiSO4生成的Ti(OH)4进行处理,发现浓硝酸在低温下可以促使纳米金红石型二氧化钛的生成,用XRD及高分辨率透射电镜(HRTEM)对生成的晶粒晶型及形貌进行了分析,发现纳米晶的稳定性差,晶体界面有较多的缺陷和非晶,并有孪晶出现。     

The synthesis of a porous-type of TiO2 with rutile structure

The synthesis of a porous-type of TiO₂ with rutile structure was studied. The focuses were on the thermal treatment temperature and time. AEROXIDE® TiO₂ P 25, as a fumed TiO₂, was thermally treated in a vertical-type tubular furnace by the natural dropping method. Even though the thermal treatment time was less than 1?s, a drastic increase of polymorphism from anatase structure to rutile structure was observed. The relationships between the rutile structure transformation ratio and surface area of obtained porous type of TiO₂ were investigated depending on the thermal treatment temperature. The porous-type of fumed TiO₂ showed high dispersibility in the sedimentation test although is showed large particle size.     

An organometallic synthesis of TiO2 nanoparticles

We report the synthesis of TiO2 nanoparticles that uses the low-temperature reaction of low-valent organometallic precursors. Bis(cyclooctatetraene)titanium reacts with dimethyl sulfoxide in organic solution at temperatures as low as room temperature to produce TiO2. In the absence of any supporting ligand, the reaction gives precipitation of amorphous TiO2 powder; however, in the presence of basic ligands such as tributylphosphine, tributylphosphine oxide and trioctylphosphine oxide, the precipitation is arrested, and chemically distinct, isolated, internally crystalline TiO2 nanoparticles are formed.     

Chemical synthesis of Cu2Se nanoparticles at room temperature

A simple and rapid method has been developed to synthesize cuprous selenide (Cu₂Se) nanoparticles by the reaction of selenium nanoparticles sol with copper sulfate solution containing ascorbic acid at room temperature. Cu₂Se nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). The results indicated that Cu₂Se nanoparticles were cubic crystal structure and spherical with the diameter about 75 nm. The ultraviolet–visible absorption spectrum (UV–vis) and cyclic voltammetry of Cu₂Se nanoparticles were also investigated. The optical band gap energy of Cu₂Se nanoparticles was 1.94 eV. On the basis of a series of experiments and characterizations, the formation mechanism of Cu₂Se nanoparticles was discussed.     

Phase-pure TiO(2) nanoparticles: anatase, brookite and rutile

We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite structures, using amorphous titania as a common starting material. Phase formation was achieved by hydrothermal treatment at elevated temperatures with the appropriate reactants. Anatase nanoparticles were obtained using acetic acid, while phase-pure rutile and brookite nanoparticles were obtained with hydrochloric acid at a different concentration. The nanomaterials were characterized using x-ray diffraction, UV-visible reflectance spectroscopy, dynamic light scattering, and transmission electron microscopy. We propose that anatase formation is dominated by surface energy effects, and that rutile and brookite formation follows a dissolution-precipitation mechanism, where chains of sixfold-coordinated titanium complexes arrange into different crystal structures depending on the reactant chemistry. The particle growth kinetics under hydrothermal conditions are determined by coarsening and aggregation-recrystallization processes, allowing control over the average nanoparticle size.     

Fabrication and characterization of nano TiO2 thin films at low temperature

Anatase TiO₂ thin films were successfully prepared on glass slide substrates via a sol–gel method from refluxed sol (RS) containing anatase TiO₂ crystals at low temperature of 100 °C. The influences of various refluxing time on crystallinity, morphology and size of the RS sol and dried TiO₂ films particles were discussed. These samples were characterized by infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activities of the TiO₂ thin films were assessed by the degradation of methyl orange in aqueous solution. The results indicated that titania films thus obtained were transparent and their maximal light transmittance exceeded 80% under visible light region. The TiO₂ thin films prepared from RS-6 sol showed the highest photocatalytic activity, when the calcination temperature is higher than 300 °C. The degradation of methyl orange of RS-6 thin films reached 99% after irradiated for 120 min, the results suggested that the TiO₂ thin films prepared from RS sol exhibited high photoactivities.     

Oxidation behavior of copper nanoparticles at low temperature

A mass gain for copper nanoparticles with a mean diameter of 20 nm in a 20% oxygen-nitrogen atmosphere was measured at 150-300 °C using thermogravimetry (TG). The mass gain equilibrium of the copper particles differed at each temperature, and a threshold temperature was recorded. Oxide products, consisting mainly of Cu₂O, formed on the copper nanoparticles below the threshold temperature. Above the threshold temperature, there was an initial, and drastic, formation of Cu₂O, which then changed to CuO. The activation energy for the oxidation of the copper nanoparticles that could be calculated from the rate of the mass gain was an indication of the nano-effect of the copper nanoparticles.     

One pot synthesis and characterization of ultra fine CeO2 and Cu/CeO2 nanoparticles. Application for low temperature CO oxidation

Ultra fine cerium oxide and copper doped cerium oxide nanoparticles are prepared in a one-step reaction by thermal decomposition of Ce acetate in commercial oleylamine. The products are highly crystalline and were characterized by XRD, Raman spectroscopy, XPS, TEM and BET. The TEM images show that the CeO2 particles prepared are uniformly nanosized. The size of the nanoparticles can be controlled in the sub-10 nm range by the presence of other capping agent in the reaction mixture such as tri-octylphosphine oxide and oleic acid. The copper doped cerium oxide nanoparticles show high specific surface area (up to 299 m2/gr) and high catalytic activity for the low temperature CO oxidation even at low copper loading such as 9 at.%.     

Sputtered rutile stoichiometric TiO2 nanocrystalline films

Titanium dioxide (TiO₂) films were prepared at room temperature on silicon and glass substrates using DC reactive magnetron sputtering at the rate of 0.1 nms⁻¹ from a pure metal Ti target. X-ray diffraction (XRD) studies on freshly prepared samples showed a purely rutile phase. It is found from AFM that annealing of fresh TiO₂ films at 550°C for 30 min produced an increase in grain size by a factor of at least 1.5. X-ray photoelectron spectroscopies (XPS) gives correct ratio for purely TiO₂ stoichiometry. Optical band gap was estimated to be 3.2 eV from UV–vis transmission spectra.