微乳法制备纳米羟基磷灰石

本文以阳离子表面活性剂CTAB（十六烷基三甲基溴化胺）为模板剂,在反微乳体系中制备出了羟基磷灰石纳米晶粒,并通过红外光谱对其进行了结构表征。另外,通过改变水与表面活性剂的浓度比值,发现对产物羟基磷灰石纳米晶粒的粒度控制有着重要的影响。     

Surfactant-assisted hydrothermal synthesis of Fluoridated Hydroxyapatite nanorods

Fluoridated Hydroxyapatite (FHA) nanorods were synthesized using Apricot Tree Gum (ATG) as a novel surfactant and then compared with Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Sodium Dodecyl Sulfate (SDS) as conventional surfactant agents under hydrothermal condition (70 °C and 1 atm). The effects of pH values and various types of surfactants on the formation of the FHA nanorods, crystalline phase, and chemical compositions were investigated using Field Emission Scanning Electron Microscopy (FESEM) equipped by Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The findings indicated application of the presented ATG as surfactant is able to produce the hexagonal nanorods of FHA along their c-axis direction. Moreover, it is illustrated that diameter and length of nanorods which is obtained by ATG surfactant are bigger than EDTA and SDS. In addition, it is demonstrated that pH values can play a major role on formation of hexagonal FHA nanorods. The increase of pH transformed the shape of synthesized FHA from particles to rods. Ultimately, based on the similarity of synthesized FHA nanorods to the shape, structure, and composition of enamel; it is suggested for its potential to be used for dental applications.     

羟基磷灰石生物陶瓷及固定化载酶初探

本文以为Ca（OH）2,（NH4）2HPO4为原料,利用酵母细胞作为模板合成羟基磷灰石粉体,并以羧甲基纤维素为粘结剂来制备羟基磷灰石陶瓷,利用X射线衍射（XRD）测试手段对样品化学组成进行表征,并用其固定α-淀粉酶,来初步测定羟基磷灰石陶瓷载体的固定化性能。     

沉淀法制备羟基磷灰石粉料

本文研究了用沉淀法制备羟基磷灰石粉料的过程。对反应物的配比、反应温度、PH值、反应时间四因素进行了对比研究。结果表明沉淀法合成羟基磷灰石的含量和纯度均比较高。     

Synthesis,Stabilization and Activation of Pt Nanoparticles for PEMFC Applications

Amongst the main challenges of catalyst materials for Proton Exchange Membrane Fuel Cells (PEMFCs) are activity and durability. Here we report on the synthesis of monodisperse nanoparticles and stabilization with traces of the surfactant, here Na‐AOT (bis‐(2‐ethylhexyl) sulfosuccinate sodium salt), used in the synthesis procedure. The surfactants prevent agglomeration and reduce Ostwald ripening. We compare the performance of Pt catalyst nanoparticles synthesized in dense microemulsions, Na‐AOT/heptane/water and Triton X‐100/toluene/water, with a commercial state‐of‐the‐art catalyst for the Oxygen Reduction Reaction (ORR). The produced catalyst nanoparticles were extracted onto a carbon support, Vulcan XC‐72R, washed and activated by heat‐treatment, which led to heavy agglomeration, or by electrochemical treatment, which led to an enhanced activity for ORR. Additionally, in comparison to the other two catalysts an increased durability of the platinum nanoparticles synthesized in the microemulsion of Na‐AOT/heptane/water was observed.     

Synthesis of spherical zirconia by reverse emulsion precipitation

Spherical ZrO₂ microparticles were prepared in a three-phase reactor by mixing two water-in-oil emulsions with normal heptane as oil phase and aqueous solutions of zirconium oxyacetate and ammonia as water phases, respectively. The principal factors that influenced the stability of emulsion were investigated, including the surfactant type, the volume of w/o, and the concentration of zirconium ion. In this work, four anion surfactants were tested, including Span 85, Arlacel 83, Span 80 and Span 40. The most stable reverse emulsions were obtained with the surfactant Span 40. When w/o volume ratio was kept 1/100 using Span 40 or Span 80 as a surfactant, the ZrO₂ microparticles with spherical morphology were successfully prepared in the reverse emulsions at various Zr⁴⁺ concentrations (from 0.5 M to 3 M). The particle sizes of ZrO₂ are smaller for Span 40 as compared with Span 80 on the same Zr⁴⁺ concentrations. The crystalline phase of the ZrO₂ powders after calcination at 750 °C for 2 h was tetragonal.     

微乳液法合成棒状纳米Ni

在25℃时,作出SDS/正丁醇/正庚烷/水体系中SDS和正丁醇质量比为1∶1时的拟三元相图,用电导率曲线讨论了该体系由W/O型→双连续型→棒状液晶→层状液晶→双连续型→O/W型的微观结构转变。并在70℃时,以棒状液晶结构的微乳液为反应模板,用水合肼为还原剂还原NiCl2,合成出棒状纳米Ni。TEM研究表明,棒的直径处于20~30 nm,长度为150~250 nm,长径比为7~10。合成结果表明,通过控制反应模板的结构,可以有效地合成特定形状的纳米粒子。     

Comparative hydrothermal synthesis of hydroxyapatite by using cetyltrimethylammonium bromide and hexamethylenetetramine as additives

Comparative synthesis ways for preparing HA (Ca₁₀(PO₄)₆(OH)₂) nanoparticles in presence of hexamethylenetetramine (HMTA) and cetyltrimethylammonium bromide (CTAB) were carried out. The reactions were performed in a Teflon-lined stainless-steel reactor at 120 °C during 12 h. The effects of the additive concentration and the cooling mode (fast and slow) were analyzed. The obtained powders were characterized by X-ray Diffraction (XRD), Raman Spectroscopy, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The two hydrothermal ways carried out for preparing HA nano powders produced a pure crystalline phase of HA. When the fast cooling mode was used, the obtained particles exhibited smaller mean particle sizes. The highest concentrations of used additives (HTMA or CTAB) resulted in opposite effect on the obtained mean particle size of HA particles. These observations were associated to the different behavior of these additives in the HA formation processes.     

悬浮聚合用HAP／SDBS无机分散体系的作用机理

研究了ＨＡＰ粉末的沉降特性与生成过程，考察了ＨＡＰ粉末和不同表面活性剂配合在苯乙烯单体分散液中的吸附特性，同时研究了ＨＡＰ粉末复合不同表面活性剂的无机分散体系用于苯乙烯单体悬浮聚合时的聚合稳定性。对ＨＡＰ／ＳＤＢＳ无机分散体系用于悬浮聚合时的分散作用机理进行了探讨。简化了用于苯乙烯悬浮聚合用ＨＡＰ的制备方法：取消缓冲体系，缩短陈化时间，室温制备。且制备的分散剂用于聚合时为常量的１／５。     

纳米羟基磷灰石的制备及表征

采用化学沉淀法制备了羟基磷灰石纳米粒子,并且通过扫描电子显微镜(SEM)、X射线衍射(XRD)、红外光谱(IR)等测试手段,对其进行了表征。实验结果表明:以Ca(OH)2和H3PO4为原料所制备出的纳米羟基磷灰石纳米粒子多呈针状或短棒状,平均粒径20~25 nm,长75~80 nm,且大小均匀,分散性好。尺寸和形状更接近人体骨磷灰石结构,并能与骨形成牢固的化学结合,是一种很有应用前景的人工骨和人工口腔材料。     

Effect of PEO-PPO-PEO structure on the compressed ethylene-induced reverse micelle formation and water solubilization

Some of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymers aggregate in p-xylene upon addition of ethylene and form reverse micelles at higher temperature at which the reverse micelles cannot be formed without addition of compressed ethylene. An abrupt increase of water solubilization is observed at a certain ethylene pressure. The effects of surfactant structure, such as the ratio of EO (EO weight percent) and the molecular mass, on the copolymer micellization and the solubilization of water in such systems are studied. For the copolymers with the same length of PO block, higher EO ratios facilitate the reverse micelle formation. However, as the EO ratio reaches 70%, it cannot form reverse micelles because the hydrophilicity is too high. For the copolymers with same composition, higher molecular weight is favorable to forming the reverse micelle due to the hydrophilic and folding effects, respectively. The reverse micelle solution can solubilize water with W₀ (molar ratio of water to EO segment) up to 4.1.     

Preparation and characterization of monoclinic sulfur nanoparticles by water-in-oil microemulsions technique

Nanosized monoclinic sulfur particles have been successfully prepared via the chemical reaction between sodium polysulfide and hydrochloric acid in a reverse microemulsions system, with theolin, butanol, and a mixture of Span80 and Tween80 (weight ratio 8 : 1) as the oil phase, co-surfactant and surfactant, respectively. Transparent microemulsions were obtained by mixing the oil phase, surfactant, co-surfactant, and the aqueous phase in appropriate proportion using an emulsification machine at the room temperature. The resulting sulfur nanoparticles were characterized by dynamic light scattering (DLS), X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM).     

Conducting polymeric nanoparticles synthesized in reverse micelles and their gas sensitivity based on quartz crystal microbalance

Conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles were prepared by reverse micelle method, which could be well dispersed in water or alcoholic solvent with ultrasonic treatment. The formation and doped state of PEDOT nanoparticles were confirmed by UV-vis-near IR absorption spectrum, X-ray photoelectron spectroscopy (XPS) and FT-IR spectrum. The nanoparticles with the size of ca. 20-40 nm were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compare to electrical conductivity of conventional PEDOT particles (ca. 0.5 S/cm), the as-prepared palletized nanoparticles have higher conductivity (ca. 10.2 S/cm) and the conductivity varies with the doped and de-doped states of PEDOT. As for sensing property, it has been found that QCM device coated with nanoparticles shows faster response and recovery to 20 ppm ammonia gas (ca. 50 s) than that of conventional PEDOT particles. The PEDOT nanoparticle covered device exhibits almost linear relation to lower NH₃ gas concentration and shows a saturate tendency of gas sensitivity with the increase of gas concentration over 500 ppm. The mechanisms of electrical conductivity and gas sensitivity of PEDOT nanoparticles were also discussed.     

Synthesis and characterization of Nb2O5@C core-shell nanorods and Nb2O5 nanorods by reacting Nb(OEt)5 via RAPET (reaction under autogenic pressure at elevated temperatures) technique

The reaction of pentaethoxy niobate, Nb(OEt)₅, at elevated temperature (800 °C) under autogenic pressure provides a chemical route to niobium oxide nanorods coated with amorphous carbon. This synthetic approach yielded nanocrystalline particles of Nb₂O₅@C. As prepared Nb₂O₅@C core-shell nanorods is annealed under air at 500 °C for 3 h (removing the carbon coating) results in neat Nb₂O₅ nanorods. According to the TEM measurements, the Nb₂O₅ crystals exhibit particle sizes between 25 nm and 100 nm, and the Nb₂O₅ crystals display rod-like shapes without any indication of an amorphous character. The optical band gap of the Nb₂O₅ nanorods was determined by diffuse reflectance spectroscopy (DRS) and was found to be 3.8 eV.     

Aspect ratio controlled synthesis of gold nanorods

Au nanorods were synthesized by using seed-mediated methods. The aspect ratio of the Au nanorods was controlled by temperature and the amount of surfactant used and the rods were characterized by TEM, HRTEM and UV-VIS spectrophotometer. Au nanorods with high aspect ratio could be prepared by decreasing the temperature used and controlling the surfactant concentration. The UV-VIS absorption spectra of the nanorods also showed variations in the aspect ratio. These results suggest that Au nanorods form, via an anisotropic growth mechanism, and that the surfactant plays a role in this process.     

An investigation of NO/CO reaction over perovskite-type oxide La0.8Ce0.2B0.4Mn0.6O3 (B = Cu or Ag) catalysts synthesized by reverse microemulsion

The perovskite-type oxides La_0.8Ce_0.2Cu_0.4Mn_0.6O₃ and La_0.8Ce_0.2Ag_0.4Mn_0.6O₃ prepared by reverse microemulsion and sol–gel methods (denoted as R and S, respectively), have been investigated on their catalytic performance for the (NO + CO) reaction, and characterized by means of temperature-programmed desorption (TPD), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). XRD measurements proved the presence of the perovskite phase with a considerable amount of CeO₂ phase and the formation of CeO₂ phase was restrained with the reverse microemulsion method. TEM investigations revealed that the La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-R nanoparticles were uniform spheres in shape with diameters ranging from 40 to 50 nm, whereas an aggregation of particles was found for the La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-S catalyst. The activity of NO reduction with CO decreased in the order of La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-R > La_0.8Ce_0.2Cu_0.4Mn_0.6O₃-S > La_0.8Ce_0.2Ag_0.4Mn_0.6O₃-R > La_0.8Ce_0.2Ag_0.4Mn_0.6O₃-S. In NO-TPD experiments, the principal desorbed species detected in the effluent was NO with a trace amount of O₂ and N₂O, suggesting that the non-dissociated adsorption of NO on the surface of the perovskite-type oxides was dominant. The XPS results revealed that Ce⁴⁺ and Cu⁺ was the predominant oxidation state for Ce and Cu components in La_0.8Ce_0.2Cu_0.4Mn_0.6O₃ and La_0.8Ce_0.2Ag_0.4Mn_0.6O₃ catalysts. The existence of Cu⁺ ions and its redox reaction (Cu⁺ ↔ Cu²⁺) would benefit the NO adsorption and reduction by CO.     

柴油微乳液研制及影响因素的考察

利用非离子型表面活性剂复配制备W/O柴油微乳液,并以油、水、表面活性剂 助表面活性剂为三组分做出相图。通过微乳液相区面积考察不同因素对制备柴油微乳液的影响。因素包括不同表面活性剂的复配,不同的助表面活性剂及助表面活性剂与表面活性剂的比(m(C)∶m(T))。并用不同浓度的碱液代替水相,考察碱液对柴油微乳液形成的影响。结果表明最佳实验条件为:表面活性剂复配比为0.667,m(C)∶m(T)=0.3,助剂为正丁醇,碱液质量分数为0.1%。利用HLB值理论和界面膜理论对实验结果进行了分析。     

Rod-like micelle templated synthesis of porous hydroxyapatite

Use of macromolecular templates for controlling nanostructures of inorganic materials is an active area of research. In particular, oriented growth of hydroxyapatite in organic matrix is of great relevance to understand biomineralisation of bone and its potential biomedical applications. Natural bone being a composite of hydroxyapatite and collagen fibers, crystallization of hydroxyapatite in fibrous assemblies could mimic such biomineralisation. This motivated us to investigate the role of long rod-like micelles in modulating the structure of hydroxyapatite particles. In this article, we report the preparation of porous hydroxyapatite nanorods using rod-like micelles made up of a cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic hydrotrope sodium salicylate (SS) as a templating agent. The successful formation of hydroxyapatite crystals is evident from XRD, FTIR, TGA, SEM and TEM analyses. It has been observed that large hydroxyapatite nanorods of diameter ～50 nm are formed in surfactant mediated synthesis, whereas irregular shaped nanoaggregates of hydroxyapatite are obtained in the absence of surfactant. A comparative study on the porosity of hydroxyapatite clearly shows that monomodal distribution of mesopores with a peak at ～30 nm in the absence of surfactant while bimodal distribution of mesopores having maxima at ～4 nm and ～45 nm appear in hydroxyapatite prepared in the presence of surfactant template.