Rapid preparation of monodisperse biodegradable polymer nanospheres using a membrane emulsification technique under low gas pressure

Nanospheres of poly(lactide-co-glycolide) (PLGA), a biodegradable polymer, have been prepared using the conventional solvent diffusion method. In this study, a method combining the solvent diffusion method and a two-step (premix) membrane emulsification technique is proposed for the preparation of monodisperse PLGA nanospheres with a diameter of 200 nm. The monodispersity of the PLGA nanospheres was higher than that of nanospheres obtained by the conventional solvent diffusion method. Generally, preparation of small particles or droplets by the membrane emulsification technique requires a supply of high-pressure nitrogen gas to force the emulsion or dispersion solution through the small pores of the membrane. However, in the technique proposed here, low-pressure nitrogen gas (0.02–0.11 kgf/cm²) is sufficient. Thus, using this technique, one can obtain monodisperse PLGA nanospheres with a diameter of 200 nm in a relatively short period of time under low-pressure nitrogen gas.     

NiTiO3纳米棒的制备及表征

结合溶胶-凝胶法和微乳液化学剪裁技术,以钛酸丁酯和N iC l2制备凝胶,在SDS/正丁醇/正庚烷/水形成的微乳液体系中,对凝胶进行化学剪裁并与KBH4反应,经500℃煅烧30 m in,制备出直径40~100 nm,长度150~700 nm,长径比为4~7的N iTiO3纳米棒。用XRD、ED、EDS、IR、TEM、TGA和DSC等方法对产物的组成、结构及纳米棒的形成过程进行了研究。实验表明,凝胶的陈化时间、煅烧温度和煅烧时间对纳米N iTiO3的组成、粒径和形貌均有影响。研究认为,前驱物不均匀地吸附有机物,导致煅烧过程中,颗粒在不同方向上以不同的速度生长,是N iTiO3纳米棒形成的原因。     

Mesoporous ZnO nanoclusters as an ultra-active photocatalyst

Morphology modulation of nanostructured materials are highly crucial for various applications including photocatalysis, drug delivery, etc. In this study, mesoporous zinc oxide (ZnO) nanoclusters (MZN) were synthesized via a simple, cost-effective, low-temperature wet chemical route and further sucessfully utilized for photodegradation of Rhodamine B (RhB). Firstly, polystyrene (PS) nanospheres (~300 nm) were prepared by polymerization of styrene in aqueous solvent. Then the MZN were achieved by formation of ZnO nanoparticles-shell over the surface of PS nanospheres via esterification of zinc acetate dihydrate in isopropyl alcohol followed by toluene dissolution of PS core. The as-synthesized MZN were spherically-shaped, porous in nature with a diameter of ~ 400 nm and composed of well-arranged highly-crystalline ZnO nanoparticles (~ 5 nm). The MZN also exhibited a high surface area of 78.3±5.4 m² g⁻¹ and an average pore diameter of ~26 nm. Furthermore, this unique structure demonstrates an expeditious photodegradation of RhB under UV illumination, monitored by UV–visible spectroscopy at different time intervals until the dye was completely degraded to colorless end products. Fast RhB decomposition was observed with a degradation rate of ~98% within initial 40 min which can be attributed to the porous nature, large specific surface area and excellent electron accepting features of the engineered nanoclusters.     

不同硅源对水热合成Zn2SiO4:Mn荧光材料形貌及性能的影响

分别以晶态和非晶态SiO2为硅源,在高压釜中采用水热法合成Zn2SiO4:Mn荧光粉,并对其晶体结构、形貌、光吸收及光致发光性能进行表征. 结果表明,在220℃下反应6 d,以晶态SiO2合成的Zn2SiO4:Mn纳米颗粒呈六棱柱状,具有单晶结构,颗粒长约5~8 mm,平均直径约1 mm;以非晶SiO2合成的Zn2SiO4:Mn纳米颗粒呈多晶结构,平均长约500 nm,平均直径约100 nm. 2种硅源所制样品在250 nm以下的紫外光区具有强吸收,且非晶SiO2所制样品在250~350 nm具有良好的紫外光吸收能力. 以不同硅源低温制备的Zn2SiO4:Mn样品在波长215和250 nm的紫外光激发下均能产生520 nm的绿色荧光,且在相同反应时间下非晶硅源制备的样品发光较强.     

Catalytic synthesis of SiC nanowires in an open system

SiC nanowires (NWs) are usually synthesized in a closed vacuum reaction system which limits the yield of SiC NWs. In this work, SiC NWs and carbon nanotubes were synthesized in an open tube furnace at 1550°C with Si powder as silicon sources, ethanol as carbon sources and ferrocene as catalyst. The as-synthesized products were ultralong β-SiC NWs with the diameter about 80-100 nm and the length up to several tens micrometers. The diameter of the carbon nanotubes was about 20-30 nm. The carbon nanotube yarns about 20 cm in length were obtained at the end of the tube furnace. The growth mechanism of SiC NWs and carbon nanotubes were proposed. Compared with the traditional synthetic techniques in the high vacuum closed system, the novel synthesis method in the open system provided a new approach to the synthesis of SiC NWs.     

双壳结构绿色电泳粒子的制备及其应用

采用反相微乳液-表面溶剂聚合法制备了双壳结构的绿色电泳粒子(PIB/CT/S).采用SEM、TEM、XPS、FTIR和XRD对其进行了表征,以四氯乙烯为分散介质,PIB/CT/S为电泳粒子进行了电泳性能测试.结果表明,PIB/CT/S具有良好的球形结构,平均粒径为241.2 nm,是以二氧化硅球(S)为基体,以绿色钛酸钴(CT)为第一层包覆物,以离子液体聚合物〔聚(1-乙烯基-3-十二烷基)咪唑溴(PIB)〕为第二层包覆物,其密度为1.7905 g/cm3.可见光漫反射测试和电子墨水涂布平台测试表明,PIB/CT/S具有较好的光学性质.制备的简易电泳显示器(EPD)的响应时间为165 ms,明显优于商用EPD(响应时间为260～300 ms).     

反胶束微乳液法制备纳米ZnO

以CTAB/煤油/正辛醇/氨水反胶束微乳体系,采用双微乳液混合法制备了纳米ZnO,考察了CTAB和反应物浓度对ZnO粒径的影响,利用TEM、XRD等手段对产品进行了表征。结果表明,所得纳米ZnO为球形六方晶体,粒径为20~70 nm,且分散性较好。     

Synthesis of Platinum/Silica Nanocomposite Particles by Reverse Micelle and Sol–Gel Processing

Pt/SiO₂ nanosized particles have been synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. The size of the particles and the thickness of the coating can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the microemulsion. The average size of synthesized particles was in the size range of 21–42 nm. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.     

Synthesis of single-crystal HAP nanorods

Single-crystal hydroxyapatite (HAP) nanorods have been successfully synthesized by the reverse microemulsion method, and characterized by high-resolution transmission electron microscope (HRTEM), infrared spectra (IR), and powder X-ray diffraction (XRD). In this work, the feasibility of using quaternary reverse microemulsion (TX-100 + CTAB/n-butanol + n-hexanol/cyclohexane/water) to prepare hydroxyapatite nanorods with diameter 8–15 nm and length 25–50 nm, is described. The homogeneity in size and shape of hydroxyapatite nanoparticles observed by TEM is probably attributed to the different stabilization functions of different kinds of surfactant on the interfacial film.     

Facile synthesis of polypyrrole nanospheres and their carbonized products for potential application in high-performance supercapacitors

A facile method to prepare uniform polypyrrole (PPy) nanospheres is developed by using 3-chloroperbenzoic acid as oxidant, structure-induced reagent and dopant for polymerization of pyrrole without introducing extra acid, template and surfactant. The as-synthesized PPy nanospheres with an average diameter of 100–200 nm and conductivity about 10⁻² S cm⁻¹ are characterized by SEM, FTIR, UV–vis spectroscopy, XRD and elemental analysis in an effort to determine the identity of the nanospheres and the mechanism relevant to their formation and stabilization. Influences of experimental conditions on the morphology of the PPy nanospheres have been investigated. Via the high temperature pyrolyzation at 900 °C, the nitrogen-doped carbon nanospheres have been obtained from the PPy nanospheres precursors, which have a high conductivity of 10–100 S cm⁻¹, showing a good potential as the electrode materials for high-performance supercapacitors due to their excellent electrochemical performance.     

Effects of Rod‐like Particles on the Microstructure and Strength of Porous Silica Nanoparticle Composites

This study describes the results of an investigation into the effects of the addition of rod‐like silica nanoparticles on the properties of freeze‐cast and sintered bodies formed from silica nanospheres. Rod‐like silica particles with ～220 nm diameter and tunable aspect ratio from ～1 to ～12 (length/diameter) were prepared and added to aqueous suspensions containing 22 nm spherical silica particles. After freeze casting, porous composites were created with all suspensions, which is shown to be consistent with the results of a simple analysis in which the experimental freezing rate is compared with the critical rate at which the dispersed particles can no longer be expelled from the growing ice front. The composites have elongated spherical pores, and the pore size changes slightly with increasing aspect ratio of the nanorods. Finally, it was found that the rod‐like particles improve the flexural strength of the composites at both green and sintered states and this strengthening effect intensifies with increasing aspect ratio. This study provides a strategy for fabricating porous materials of improved properties and performance without compromising the porosity or changing the material composition.     

Shape-controlled synthesis of nanocarbons from resorcinol-formaldehyde nanopolymers using surfactant-templated vesicular assemblies

The NaOH-catalyzed polymerization of resorcinol (R) and formaldehyde (F) confined to the vesicular assemblies of cetyltrimethylammonium bromide as a core template mixed with 1,3,5-trimethylbenzene and tert-butanol (tBuOH) as cosurfactants yielded RF polymer/cetyltrimethylammonium composite nanowires and nanospheres depending on the amount of tBuOH. Carbonization of the resulting nanpolymers led to microporous carbon nanowires of 45-240 nm diameter and nanospheres of 260-650 nm diameter. Similar but a little modified reactions successfully resulted in monodispersed carbon nanospheres of ca. 280 nm diameter as well as monodispersed carbon nanowires of ca. 70 nm diameter with a high surface area of 1777 m²/g. The present approach could be further extended to the synthesis of a wide range of carbon nanomaterials by using various surfactants and cosurfactants.     

Synthesis of Pure and Manganese-, Nickel-, and Zinc-Doped Ferrite Particles in Water-in-Oil Microemulsions

In recent years, the materials research focuses toward synthesis of finer and finer microstructural features. The unique properties of nanosized particles outweigh their higher production costs. Precipitation in microemulsion is one technique, which promises to produce small particles of controlled size and morphology at reasonable cost. The present study demonstrates the synthesis of nanocrystalline α-Fe₂O₃(hematite), Mn_0.5Zn_0.5Fe₂O_4, and Ni_0.5Zn_0.5Fe₂O₄ particles in a reverse micellar microemulsion system [water–iso-octane–AOT (sodium di-2ethylhexylsulfosuccinate)]. The synthesis of α-Fe₂O₃ is performed to obtain baseline data for the synthesis of Mn_0.5Zn_0.5Fe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄ in the microemulsion system. Nanosized, spherical α-Fe₂O₃, Ni-Zn ferrite, and Mn-Zn ferrite particles (20–80 nm) with very narrow particle size distribution are synthesized. Crystallization of the particles is obtained at temperatures as low as 300°C.     

A facile method for synthesis of polyaniline nanospheres and effect of doping on their electrical conductivity

The synthesis of polyaniline (PANI) nanospheres by a simple template-free method has been described. The polymerization of aniline in aqueous medium was accomplished using ammonium persulfate without any protonic acid. The UV-vis spectrum of PANI nanospheres displayed the characteristic absorption peak of π-π* transition of the benzenoid ring at 355 nm. The oxidation state of PANI nanospheres was identified with FT-IR spectroscopy by comparing the two bands at 1582 (ring stretching in quinoid unit) and 1498 cm(-1) (ring stretching in bezenoid unit). The X-ray diffraction patterns demonstrated the low crystalline nature of PANI nanospheres. The morphology of PANI nanospheres was spherical and the mean diameter of nanospheres was found in the range of 3-12 nm. The thermal behavior of PANI nanospheres was studied by thermogravimetric analysis. The effect of doping of HCl and H(2)SO(4) on PANI nanospheres was studied by measuring the current as a function of time of exposure. The high electrical conductivity of 6×10(-2) S cm(-1) was obtained for PANI nanospheres at their optimum doping state by 100 ppm HCl.     

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。     

电导率法研究W/O微乳液中Pd纳米微粒的化学破乳负载

利用水-Tween-80-Span-80-环己烷微乳液合成了粒径为5~10 nm、高度分散的Pd纳米微粒. 结果表明,随着破乳剂用量的增大,含Pd微乳液与破乳剂的混合体系依次呈现微乳液、分层、胶体或微乳液体系. 破乳剂的亲水性与分子结构是影响破乳行为的主要参数. 利用混合物体系分层与再均相的临界区域,在微乳液浸渍a-Al2O3载体的同时,使其中的Pd纳米微粒破乳沉积,实现了Pd在载体表面的均匀负载. TEM及XPS分析表明,Pd的微粒粒径为10~20 nm, 以单质形态结合于载体表面.     

Preparation of isotropic submicron spherical boron nitride particles by restricted template method

Hexagonal boron nitride (h-BN) has received considerable attention, due to its high thermal conductivity and electrical insulation. However, the intrinsic platelike structure with the strong anisotropic property restricts its applications, and it is necessary to synthesize isotropic spherical h-BN particles (SP-BNs) with submicron size. Till now, methods to prepare (SP-BN) still exist problems, such as high oxygen impurities and pollution, generated by the ammonia and pyrolysis of precursors. Here, a relatively green reaction between the restricted template of carbon nanospheres and boron trioxide (B₂O₃) under elevated temperature is conducted, and the SP-BNs with an average diameter of 200–300 nm (named Nano-BN-s) have been successfully synthesized. Comprehensive scanning electron microscopy, transmission electron microscopy, and X-ray diffraction characterizations confirm the obtained products are spherical boron nitride. With the analysis of X-ray photoelectron spectroscopy and Fourier transform infrared, the reaction mechanism is briefly discussed. These results indicate the reaction occurs on the restricted template of carbon nanospheres, and the C atoms are substituted by B and N atoms as the reaction progress, forming the Nano-BN-s. What is more, the restricted template method plays a key role in the design and improves h-BN-based materials in the future and may also be extended to form other novel materials.     

Chemical reactions between calcium carbide and chlorohydrocarbon used for the synthesis of carbon spheres containing well-ordered graphite

Carbon spheres and carbon nanospheres were prepared through the chemical reactions between calcium carbide and chlorohydrocarbon without using any catalysts. The reactants were sealed in a pressure vessel and heated to temperatures of 210-250 °C. The final products were characterized using scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) attached to SEM, transmission electron microscopy (TEM), X-ray diffraction and Raman spectroscopy. SEM and TEM examinations show that some of the obtained products are bead-like or roe-like spheres with diameters of 100-2000 nm. The carbon nanospheres have high purity (>95%) and uniform size distribution (100-200 nm). The EDS analyses reveal that the carbon contents of the spheres are 86-94%. The results indicate that the size and the size distribution of the synthesized spheres change with the change of the reactants. The experimental yields of carbonaceous materials relative to the starting materials are about 8.0-14.4% (w/w). The yields of the spheres increase whereas their size distributions decrease with the increase of H atom and the decrease of Cl atom in chlorohydrocarbon. The average graphitization degree of sample 1 and sample 2 are 81.9% and 78.7%.     

微乳液法制备PbF_2准一维纳米材料

采用辛基酚聚氧乙烯（10）醚（OP-10）/正丁醇/正辛烷/水反相微乳液体系,制备了PbF2准一维纳米材料。研究了微乳液体系中水与表面活性剂的摩尔比对准一维PbF2尺寸和形貌的影响。用扫描电子显微镜、X射线衍射仪表征样品的形貌和结构。结果表明：所得PbF2直径约200～800nm、长约1～6μm。     

A Nonaqueous Approach to the Preparation of Iron Phosphide Nanowires

Previous preparation of iron phosphide nanowires usually employed toxic and unstable iron carbonyl compounds as precursor. In this study, we demonstrate that iron phosphide nanowires can be synthesized via a facile nonaqueous chemical route that utilizes a commonly available iron precursor, iron (III) acetylacetonate. In the synthesis, trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) have been used as surfactants, and oleylamine has been used as solvent. The crystalline structure and morphology of the as-synthesized products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The obtained iron phosphide nanowires have a typical width of ~16 nm and a length of several hundred nanometers. Structural and compositional characterization reveals a hexagonal Fe₂P crystalline phase. The morphology of as-synthesized products is greatly influenced by the ratio of TOP/TOPO. The presence of TOPO has been found to be essential for the growth of high-quality iron phosphide nanowires. Magnetic measurements reveal ferromagnetic characteristics, and hysteresis behaviors below the blocking temperature have been observed.