超顺磁性高分子微球的制备与表征

用化学共沉淀方法制备了Fe3O4纳米微粒,并用油酸(十八烯酸)和十二烷基苯磺酸钠为双层表面活性剂进行表面修饰,制备了稳定的水分散性纳米Fe3O4可聚合磁流体.在Fe3O4磁流体存在下,将苯乙烯与甲基丙烯酸通过乳液聚合方法制备了磁性高分子微球.透射电镜研究表明,Fe3O4微粒的平均粒径在10nm左右,乳液聚合形成的磁性高分子微球的粒径平均约为130nm;用超导量子干涉仪对微粒及高分子微球进行了磁性表征,结果表明,合成的Fe3O4纳米微粒以及磁性高分子微球均具有超顺磁性.同时,还用红外光谱及X射线衍射表征了磁性高分子微球的化学成分和晶体结构.用热失重方法测得磁性高分子微球中磁性物质的含量为23.6%.     

羧甲基淀粉微球的制备及其对阿司匹林的控制释放

以马铃薯淀粉为原材料,水-乙醇为溶剂制备了羧甲基淀粉(CMS)。通过反相微乳液法包埋阿司匹林制备了载药羧甲基淀粉微球。通过热重、X-衍射以及扫描电镜对羧甲基淀粉进行了表征。结果显示,淀粉经过羧甲基改性后结晶度降低,聚集形态变得更加不规则,说明淀粉羧甲基后在水相中溶解度增大,有利于制备淀粉微球。将羧甲基淀粉与阿司匹林溶于水中,配成浓度为8%的水相溶液。以环己烷与氯仿的混合溶剂(V_(环己烷):V_(氯仿)=3:1)作为油相体系,经过反相乳化成球,实现了对阿司匹林的包埋。羧甲基淀粉微球经载药后呈圆形,表面光滑,粒径为200~800nm,且实现了在不同p H值溶液中对小分子药物的控制释放。有望用于口服药的载体,实现在体内的控制释放,从而增加药物利用率以及降低药物的副作用。     

自组装光致形变功能偶氮分子玻璃微球

通过逐滴滴加去离子水的方法, 探究了具有快速光响应的偶氮分子玻璃(IAC-4)在初始浓度范围为1.0~5.0 mg/mL条件下的自组装, 制备了形貌规整、 尺寸均一的胶体球, 并利用动态光散射技术(DLS)测定了IAC-4胶体球的流体力学半径. 通过测定一系列初始浓度的IAC-4溶液的临界水含量, 探究了IAC-4在自组装过程中析出、 聚集成核和核生长的规律. 研究发现, 临界水含量与IAC-4初始浓度的关系符合二元混合溶剂中固体溶质的溶解度变化规律. 通过调节去离子水的滴加量, 研究了自组装过程中, IAC-4聚集体流体力学半径呈现先增大后减小的趋势. IAC-4胶体球的水分散液, 通过室温干燥得到的固态IAC-4微球在线性偏振激光(488 nm, 100 mW/cm²)垂直辐照下表现出快速的光响应特性. 当辐照时间为1 min时, IAC-4微球快速地拉伸形变, 形成平均长径比为1.44的椭圆形粒子. 随着光辐照时间延长, 平均长径比持续增大. 当辐照时间为7 min时, IAC-4微球被拉伸为棒状粒子, 其平均长径比可高达3.32.     

羧甲基葡聚糖磁性纳米微球的制备及表征

采用超声预处理技术,在羧甲基葡聚糖-水分散体系中,通过化学共沉淀法制备羧甲基葡聚糖磁性复合微球．采用IR,TEM,AFM,XRD和振动样品磁强计方法对产物进行了表征．实验结果表明：超声预处理方法能明显提高复合微球的分散性．制得的复合微球呈球形,分散均匀,平均粒径为100nm．它们具有超顺磁性,室温下磁性饱和磁化强度为35emu·g^-1．     

烷基壳聚糖纳米微球的制备及其紫杉醇负载研究

在碱性条件下通过卤代烃的N-烷基取代反应制备得到烷基壳聚糖衍生物。X射线光电子能谱计算结果表明烷基取代反应主要发生在壳聚糖的氨基上。动态光散射研究表明，该衍生物在水中可自动形成粒径在10—200nm范围的纳米微粒，负载紫杉醇后微球的粒径增大，在磷酸缓冲液（pH=7．4）中体外释放研究表明，随着烷基链长的增加，紫杉醇在磷酸缓冲液中达到平衡时的浓度降低。     

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响.     

一种可精确控制粒径的SiO2微球合成方法

用改进的种子法合成SiO2微球. 微球生长过程中连续缓慢添加正硅酸乙酯,使用动态光散射法实时监控微球粒径的增长过程,调节正硅酸乙酯的添加,实现对粒径的精确控制. 为制备禁带位置位于1000 nm 的光子晶体,合成粒径为446 nm的SiO2微球,微球粒径在4 h内从193 nm 增长到446 nm,远远快于传统种子法,微球粒径与目标粒径偏差为±5 nm. 制得的SiO2微球被组装为光子晶体,其禁带位置恰好位于1000 nm.     

凝胶-微乳液化学剪裁制备明胶复合Ni-Fe纳米微粒

用凝胶 微乳液化学剪裁技术制备了明胶包裹的复合纳米级铁 镍超细微粒。XRD、TEM、EDS测试表明 :微粒为明胶包裹球形超细微粒。微球的平均粒径为 5 3nm ,单个微粒的粒径为 2 5nm。每个复合微球中约有2 1个铁镍粒子 ,该复合微粒的比饱和磁化强度σs=33 76 (× 10 3 / 4πAm 2 ·g 1) ,矫顽力Hc =13381Am 1,剩磁σr=6 86 (× 10 3 / 4πAm 2 ·g 1) ,具有硬磁体的性质。X 射线衍射和X 射线能谱分析表明有Ni Fe合金相形成。     

微乳液成核-离子交联制备阿司匹林/壳聚糖纳米微球及其体外释放行为

以自制阿司匹林为药物模型,壳聚糖(CS)为载体源,采用微乳液成核-离子交联法制备了阿司匹林/壳聚糖纳米缓释微球.分别用傅里叶变换红外(FTIR)光谱、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、动态激光光散射(DLLS)、X射线粉末衍射(XRD)等表征了纳米微粒的化学组成、外观形貌、平均粒径和粒径分布、微球中壳聚糖的晶体结构以及阿司匹林的分布形态.结果表明,利用微乳液成核-离子交联法制备的阿司匹林/壳聚糖微球平均粒径约为88nm且粒径分布均匀,成核后壳聚糖结晶形态基本未变,阿司匹林以分子形态分布于微粒中,分子间未形成堆砌,为无定形态.采用UV-Vis分光光度计考察了微球的药物包封率、载药量,并对微球在生理盐水和葡萄糖溶液中的释药行为进行跟踪.结果表明,微球的载药量可达55%,药物包封率可达42%,实验条件下具有较好的药物缓释作用.     

反相微乳液化学剪裁制备明胶-γ-Fe2O3纳米复合微粒

用反相微乳液化学剪裁技术制备了明胶包裹的复合 γ-Fe2 O3纳米量级超细微粒 .XRD、TEM、EDS、SEM和 IR测试表明 ,微粒为明胶包裹球形超细微粒 .微球的粒径为 1 .2～ 3 .2 μm,平均粒径约 2 .6μm,而微粒的粒径为 1 5 nm.每个复合微球中约有 80～ 2 1 3个氧化铁粒子 .该复合微粒的比饱和磁化强度 3 0 .3 44π ×1 0 3A/ m,矫顽力 Hc=62 0 7A/ m,剩磁 Br=2 .944π × 1 0 3A/ m.具有硬磁体的性质     

Synthesis of colloidal dispersions of rhodium nanoparticles under high temperatures and high pressures

Colloidal dispersions of rhodium (Rh) nanoparticles have been synthesized by the reduction of Rh ions (III) in high-temperature and high-pressure water, ethanol, or water-ethanol mixture under the existence of the protective polymer of poly(N-vinyl-2-pyrrolidone). The possibility of the regulation of the particle size and size distribution has been tested under several solvents at various temperatures and pressures. At 473 K and 25 MPa, particularly, concentrated colloidal dispersions of Rh particles of 2.5+/-0.5 nm were synthesized from the ionic solution of ethanol ([Rh]=15 mM) within a few seconds. Dilute colloidal dispersions of Rh particles were also synthesized from the dilute ionic solution ([Rh]=1.5 mM) with a diameter of 2.0+/-0.4 nm. From the water solution, Rh particles tended to form aggregates, especially for the lower concentration solution. In the case of solutions in water and ethanol mixture, the average diameter of Rh particles tended to be larger than in ethanol solution, and their distribution became broad.     

Size-dependent catalytic behavior of platinum nanoparticles on the hexacyanoferrate(III)/thiosulfate redox reaction

Platinum nanoparticles prepared in reverse micelles have been used as catalysts for the electron transfer reaction between hexacyanoferrate(III) and thiosulfate ions. Nanoparticles of average diameter ranging between 10 and 80 nm have been used as catalysts. The kinetic study of the catalytic reaction showed that for a fixed mass of catalyst the catalytic rate did not increase proportionately to the decrease in particle size over the whole range from 10 to 80 nm. The maximum reaction rate has been observed for average particle diameter of about 38 nm. Particles below diameter 38 nm exhibit a trend of decreasing reaction rate with the decrease in particle size, while those above diameter 38 nm show a steady decline of reaction rate with increasing size. It has been postulated that in the case of particles of average size less than 38 nm diameter, a downward shift of Fermi level with a consequent increase of band gap energy takes place. As a result, the particles require more energy to pump electrons to the adsorbed ions for the electron transfer reaction. This leads to a reduced reaction rate catalyzed by smaller particles. On the other hand, for nanoparticles above diameter 38 nm, the change of Fermi level is not appreciable. These particles exhibit less surface area for adsorption as the particle size is increased. As a result, the catalytic efficiency of the particles is also decreased with increased particle size. The activation energies for the reaction catalyzed by platinum nanoparticles of diameters 12 and 30 nm are about 18 and 4.8 kJ/mol, respectively, indicating that the catalytic efficiency of 12-nm-diameter platinum particles is less than that of particles of diameter 30 nm. Extremely slow reaction rate of uncatalyzed reaction has been manifested through a larger activation energy of about 40 kJ/mol for the reaction.     

Influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles

The experimental results on the influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles were reported. The spherical silica nanoparticles have been synthesized using polyethylene glycol (PEG) as the surfactant and oil shale ash (OSA) as a new silica source. In order to identify the optimal condition for producing the best quality silica nanoparticles with the good dispersion and uniformity, the effects of surfactant surface coverage and aging time were investigated. It was found that the particle size and distribution of silica nanoparticles depend on the concentration of PEG in dispersion. At relatively low concentration, 0–2 wt.%, the existing PEG is not sufficient to prevent further growth of the initially formed silica nanoparticles, leading to large aggregates of silica particles. When the PEG concentration increases to 3 wt.%, self-assembled PEG layer on the surface stabilizes the initially formed silica nanoparticles and the silica particles with average diameter of 10 nm are uniformly distributed. With further increasing the concentration of PEG, the number of PEG aggregates increases and silica nanoparticles are mainly formed inside the entangled PEG chains, resulting in an observation of clusters of silica nanoparticles. Moreover, it was found that as the aging time increased, the shape of silica nanoparticles becomes regular and the particle size distribution becomes narrow.     

Colloid stability of thymine-functionalized gold nanoparticles

Gold nanoparticles surface-coated with thyminethiol derivatives containing long hydrocarbon chains have been prepared. The diameter of the particles is 2.2 and 7.0 nm, respectively, with a relatively narrow size distribution. Thyminethiol derivatives are attached to the gold particle surfaces with thymine moieties as the end groups. The colloid stability of the gold nanoparticles as a function of the type and concentration of monovalent salt, pH, and particle size was investigated in alkaline, aqueous solutions. The gold particles are stable in concentrated NaCl and KCl solutions, but are unstable in concentrated LiCl and CsCl solutions. The larger gold particles are more sensitive to salt concentration and aggregate at lower salt concentrations. The reversible aggregation and dispersion of the gold particles can be controlled by changing the solution pH. The larger gold particles can be dispersed at higher pH and aggregate faster than the smaller particles, due to stronger van der Waals forces between the larger particles. Hydration forces play an important role in stabilizing the particles under conditions where electrostatic forces are negligible. The coagulation of the gold nanoparticles is attributed to van der Waals attraction and reduced hydration repulsion in the presence of LiCl and CsCl.     

Synthesis of iron oxide nanoparticles using chitosan and starch templates

Natural polymers like chitosan and starch have been employed as templates for the preparation of iron oxide nanoparticles. The templates offer selective binding sites for Fe(II) under aqueous conditions. Controlled drying and subsequent removal of the template backbone enables the synthesis of spatially separated iron oxide nanoparticles. The crystalline character of the iron oxide and near narrow particle size distribution pattern have been confirmed through powder XRD, Photon Correlation Spectroscopy, and TEM measurements. The crystallite sizes of the particles were found to be 26–35 nm irrespective of the nature of the template.     

Surface modified ormosil nanoparticles

Organically modified silanes (ORMOSIL) such as vinyl triethoxysilane readily aggregate in the aqueous cores of reverse micelles where the triethoxysilane moieties are hydrolyzed to form a hydrated silica network and the vinyl groups protruded out from the surface of the nanoparticles toward the hydrophobic side of the micellar interface. These particles are spherical and the size distribution of the particles is relatively narrow, with an average diameter of 87 nm. Surface vinyl silica nanoparticles so formed have been oxidized to surface carboxylic silica nanoparticles, followed by chemical conjugation with polyethyleneglycol amine (PEG amine) through the ethyl-3-(3-dimethylaminopropyl) (EDCI) carbodiimide reaction. The characteristic surface groups have been identified by Fourier transform infrared spectroscopy, while the size and the morphology of the particles have been studied by dynamic light scattering and transmission electron microscopy. It has been found that about 80-85% of the carboxylic groups are PEGylated during the EDCI reaction.     

Polymerized rodlike nanoparticles with controlled surface charge density

Stable rodlike nanoparticles with highly controlled surface charge density have been developed by the free radical polymerization of the mixture of polymerizable cationic surfactant, cetyltrimethylammonium 4-vinylbenzoate (CTVB), and hydrotropic salt sodium 4-styrenesulfonate (NaSS) in aqueous solution. The surface charge of the polymerized CTVB/NaSS rodlike nanoparticles was controlled by varying the NaSS concentration during the polymerization process, and the charge variation was interpreted in terms of the overcharging effect in colloidal systems. The SANS measurements show that the diameter of the polymerized CTVB/NaSS rodlike nanoparticles is constant at 4 nm and the particle length ranges from 24 to 85 nm, depending on the NaSS concentration. The polymerized particles are longest when the NaSS concentration is 5 mol % which corresponds to the charge inversion or neutral point. The SANS and zeta potential measurements show that the Coulomb interactions between the particles are strongly dependent on the NaSS concentration and the zeta potential of the polymerized CTVB/NaSS nanoparticles changes from positive to negative (+12.8 approximately -44.2 mV) as the concentration of NaSS increases from 0 to 40 mol %. As the NaSS concentration is further increased, the zeta potential is saturated at approximately -50 mV.     

Cross-linked polyvinylpyrrolidone nanoparticles: a potential carrier for hydrophilic drugs

Injectable hydrogel polymeric nanoparticles of polyvinylpyrrolidone cross-linked with N,N'-methylene bis-acrylamide and encapsulating water-soluble macromolecules such as FITC-dextran (FITC-Dx) have been prepared in the aqueous cores of reverse micellar droplets. These particles are 100 nm and below in diameter with a narrow size distribution. When dispersed in aqueous buffer these particles appear to be transparent and give an optically clear solution. Lyophilized powder of these nanoparticles is redispersable in aqueous buffer without any change in the size and morphology of the particles. The efficiency of FITC-Dx entrapment by these nanoparticles is high (>70%) and depends on the amount of cross-linking agent present in the polymeric material. The release of the entrapped molecules from these nanoparticles depends on the degree of cross-linking of the polymer, particle size, pH of the medium, and extent of loading, as well as temperature.     

Solvent-stabilized oxovanadium phthalocyanine nanoparticles and their application in xerographic photoreceptors

A stable organic sol of solvent-stabilized oxovanadium phthalocynine (VOPc) nanoparticles with excellent photoconductivity was successfully prepared by ultrasonificating a prepared nanoscopic VOPc powder in1,2-dichloroethane (C(2)H(4)Cl(2)) without any additive. These solvent-stabilized VOPc nanoparticles have a size distribution from 2 to 20 nm with an average diameter of 4.6 nm. The VOPc concentration of these organic sols could be as high as 100 g/L. The nanoscopic VOPc particles were well-dispersed in an insulating polycarbonate (PC) resin, resulting in single-layered photoreceptors with high surface charge durability in the dark and excellent photoconductivity. Based on the light-assisted scanning tunneling microscopy (STM) measurements, the charge transport mechanism of these photoreceptors was ascribed to light-induced enhancement of electron tunneling through the VOPc-nanoparticle/insulator junctions.     

Nanosilica-supported polyethoxyamines as low-cost, reversible carbon dioxide sorbents

Nanoparticles capped with amine ligands with different steric properties, dodecylamine and oleylamine, respectively, are investigated in the solid state as well as in solution. A combined X-ray diffraction, small angle X-ray scattering and electron microscopy investigation showed that the nanoparticles exhibit the sphalerite modification of ZnS as crystal phase with a diameter of 3-5 nm. A close packing of the monocrystalline nanoparticles in the solid state is observed. However, in the dodecylamine sample, besides spherical particles, a fraction of the nanoparticles is elongated. The nanoparticles are readily resoluble in apolar solvents like hexane. Dynamic light scattering (DLS) and SAXS investigations of the solutions reveal that the nanoparticles are dissolved as singular particles. In the case of oleylamine-capped ZnS, a defined core-shell structure with a ZnS core with a diameter of 4 nm and an organic shell with a thickness of approximately 2 nm have been found. Dodecylamine-capped nanoparticles slightly tend to form agglomerates with a diameter of approximately 40 nm.