<Emphasis Type="Italic">In situ</Emphasis> synthesis and modification of calcium carbonate nanoparticles via a bobbling method

Modified calcium carbonate (CaCO₃) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO₃ modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO₃ modified in the presence of sodium stearate, ODP and OA. When modified CaCO₃ was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO₃ nanoparticles and the organic matrixes were greatly improved. Supported by the National Natural Science Foundation of China (Grant No. 50372025)     

共沸蒸馏法制备表面化学改性氢氧化镁纳米颗粒

首次将表面改性剂如硬脂酸、硬脂酸锌或稀土偶联剂加入到传统的共沸蒸馏体系中,使Mg(OH)2纳米颗粒的表面改性和干燥过程同时完成。 通过 XRD、TEM、FT-IR、TG和CAM（接触角测试）等技术手段对样品的结构、形貌和性质进行了表征。 结果表明,表面改性剂不但能够和Mg(OH)2纳米颗粒的表面的OH-离子发生化学反应形成表面修饰层, 减少硬团聚现象,而且还使纳米颗粒表面由亲水性变为疏水性。 另外,对共沸蒸馏法制备表面改性纳米颗粒的机理进行了讨论,为纳米颗粒表面改性提供了一种新思路。     

Understanding the role of clay silicate nanoparticles with organic modifiers in thermal curing of cyanate ester resin

The catalytic effect of montmorillonite clay nanoparticles containing organic modifiers such as quaternary phosphonium salts on cure mechanism of cyanate ester resin (RS-9D) was studied by differential scanning calorimetry (DSC) measurements, FT-IR and NMR spectroscopy as well as mass-spectrometry. The results show that the net catalytic effect arises from the presence of moisture associated with nanoclay particles where organic modifiers act as moisture transport agents. Possible mechanisms for cure pathways are discussed.     

Encapsulation of silica nanoparticles by miniemulsion polymerization

Hybrid silica/polystyrene nanoparticles were synthesized by miniemulsion polymerization. With the objective to prepare core‐shell hybrid nanoparticles having narrow particle size distributions (PSDs) as well as a high degree of silica encapsulation, the effect of adding surface modifiers, the size of silica nanoparticles, the ratio styrene/silica, the surfactant concentration, and the presence of ethanol in the reaction mixture were studied. A synergistic effect was observed using oleic acid (OA) together with 3‐(trimethoxysilyl)propyl methacrylate (TPM) in the compatibilization step between the organic phase (monomer) and inorganic nanoparticles (silica). Mono and multinuclear eccentric core‐shell hybrid nanoparticles were obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 935–948, 2009     

碳酸钙的原位合成及表面改性

利用碳化法, 选用几种常见的改性剂(硬脂酸钠、十八碳醇磷酸酯和油酸)对碳酸钙进行了原位合成及表面改性. 通过活化度、白度、接触角的测定, 对比了其改性效果, 同时通过傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)等测试手段对产品进行表征. FT-IR结果表明, 改性剂与碳酸钙表面是以化学键合和物理吸附方式相结合. 碳酸钙改性后, 其红外υ3特征吸收峰出现约44 cm-1的蓝移现象. 对反应机理进行了初步探讨. 实验结果表明, 当十八碳醇磷酸酯用量达到2%(以碳酸钙的质量分数计)时, 产品活化度达到99.9%, 白度值达到97.3%, 接触角达到了122.25°, 从而为新型无机填料的制备提供了理论依据和合成手段.     

Colloidal stability and photophysical characteristics of luminesent silica nanoparticles modified with various nitrogen/oxygen-containing trialkoxysilanes

Surface modification of the luminescent silica nanoparticles doped with Tb(III)–p-sulfonatothiacalix[ 4]arene complex was carried out using a series of nitrogen/oxygen-containing trialkoxysilanes. It was found that groups capable of nonspecific interactions on the surface of the nanoparticles cause a significant decrease in their colloidal stability. The chromophore moieties in the modifiers were found to quench the luminescence of the nanoparticles. The surface modification of the nanoparticles is responsible for the change in the mechanism of luminescence quenching in the presence of copper(II) ions due to decreased accessibility of luminophores to the quencher.     

Surfactant-free miniemulsion polymerization as a simple synthetic route to a successful encapsulation of magnetite nanoparticles

Due to the existing interest in new hybrid particles in the colloidal range based on both magnetic and polymeric materials for applications in biotechnological fields, this work is focused on the preparation of magnetic polymer nanoparticles (MPNPs) by a single-step miniemulsion process developed to achieve better control of the morphology of the magnetic nanocomposite particles. MPNPs are prepared by surfactant-free miniemulsion polymerization using styrene (St) as a monomer, hexadecane (HD) as a hydrophobe, and potassium persulfate (KPS) as an initiator in the presence of oleic acid (OA)-modified magnetite nanoparticles. The effect of the type of cross-linker used [divinylbenzene (DVB) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP)] together with the effect of the amount of an aid stabilizer (dextran) on size, particle size distribution (PSD), and morphology of the hybrid nanoparticles synthesized is analyzed in detail. The mixture of different surface modifiers produces hybrid nanocolloids with various morphologies: from a typical core-shell composed by a magnetite core surrounded by a polymer shell to a homogeneously distributed morphology where the magnetite is uniformly distributed throughout the entire nanocomposite.     

The Inherent Electrochemistry of Nickel/Nickel‐Oxide Nanoparticles

The direct detection of nanoparticles is at the forefront of research owing to their environmental and toxicological applications. Herein, we studied the inherent electrochemistry of Ni and NiO nanoparticles and proposed a simple and direct electrochemical method for the determination of the concentrations of both nickel (Ni) and nickel oxide (NiO) nanoparticles in alkaline solution. A highly sensitive voltammetry technique was used to measure the oxidative signal of Ni(OH)₂ that formed spontaneously on the surface of Ni and NiO nanoparticles in alkaline media. Detection limits of 220 μg mL^?1 for Ni and 13 μg mL^?1 for NiO nanoparticles were obtained. Ni and NiO nanoparticles are used as electrode modifiers or as electrochemical signal labels in various biosensing applications. Therefore, methods to rapidly quantify the amount of Ni and NiO nanoparticles are of widespread potential use.     

Silicone‐based impact modifiers for poly(vinyl chloride), engineering resins,and blends

Silicone‐based impact modifiers were prepared in a previous study. The modifiers were composed of silicone/acrylic rubber cores and grafted acrylic shells. They improved the toughness of poly(vinyl chloride) (PVC) and poly(methyl methacrylate). The silicone emulsion that was used to produce the silicone‐based impact modifiers was prepared via two routes: emulsion polymerization and bulk polymerization of octamethyltetracyclosiloxane. Many silicone‐based impact modifiers were produced that had different silicone/acrylic rubber characteristics. Through a toughness examination of modified PVC, the best composition of the silicone‐based impact modifiers was obtained, and the silicone content in the rubber composition was 25 wt %. The morphology of the silicone‐based impact modifiers, determined by transmission electron microscopy, was as follows: core and second shell polymers were mainly poly(butyl acrylate), and the first shell polymer was silicone. The silicone‐based impact modifiers were blended with engineering resins such as PVC, polycarbonate (PC), poly(butylene terephthalate) (PBT), and PC/PBT mixtures. The impact strength under standard conditions and after weathering test conditions for blends of the silicone‐based impact modifiers were investigated with respect to two commercially available acrylic and methyl methacrylate/butadiene/styrene impact modifiers. The results showed good weatherability and good toughness under low‐temperature conditions for the silicone‐based impact modifiers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1112–1119, 2004     

Immobilization of lipases on hydrophobilized zirconia nanoparticles: highly enantioselective and reusable biocatalysts

Our study has demonstrated for the first time that zirconia nanoparticles modified by a simple carboxylic surfactant of a very long alkyl chain can significantly enhance the activity of the immobilized lipases for asymmetric synthesis in organic media. Zirconia nanoparticles of ca. 20 nm diameter were grafted with carboxylic surfactant modifiers from Tween 85 and erucic acid. The surface of nanoparticles was successfully changed from hydrophilic to hydrophobic. Lipases from Candida rugosa and Pseudomonas cepacia were immobilized on the modified zirconia nanoparticles by adsorption in aqueous solution. The immobilized lipases were used for the resolution of ( R, S)-ibuprofen and ( R, S)-1-phenylethanol through esterification and acylation, respectively, in isooctane organic solvent. When immobilized on erucic acid-modified zirconia, both lipases gave significantly higher activity and enantioselectivity compared with those from their corresponding crude lipase powders. The nanohybrid biocatalysts are stable and can be reused for eight cycles without loss in activity and selectivity. The interaction between the hydrophobic surface of zirconia support and lipases probably induces the conformational rearrangement of lipases into an active, stable form.     

Facile preparation of efficient oil-soluble MoS_2 hydrogenation nanocatalysts

Oil-soluble MoS2 nanoparticles with narrow size distribution have been synthesized by a facile composite-surfactants-aided-solvothermal process.The as-prepared nanoparticles can be directly used as hydrogenation nanocatalysts or as precursors to achieve efficient supported nanocatalysts.The surfaces of these nanoparticles are proposed to be encapsulated within a layer of organic modifiers,which are responsible for the enhancement of their solubility in organic solvents.The activated-carbon supported MoS2 nanocatalysts exhibit higher activity than the unsupported ones towards hydrogenation reactions of naphthalene,owing to the synergistic effects between nanoparticles and supports.The advantages of the present nanocatalysts,such as removal of conventional presulfiding requirements and reduction of nanoparticle aggregations,make them become promising applications in related petroleum chemical industry.     

Electrochemical deposition of gold at liquid–liquid interfaces studied by thin organic film-modified electrodes

The unique physico-chemical properties of gold nanoparticles portrayed in their chemical stability, the size-dependent electrochemistry, and the unusual optical properties make them suitable modifiers of various surfaces used in the fields of optical devices, electronics, and biosensors. In this work we present two different methods to obtain metallic gold nanoparticles at a liquid–liquid interface, and to control their growth by adjusting the experimental conditions. Decamethylferrocene (DMFC), used as an oxidizable compound dissolved in an organic solvent that is spread as a thin film on the surface of graphite electrode, serves as a redox partner to exchange electrons across the liquid–liquid interface with the other redox counter-partner [AuCl₄]^? present in the conjoined water phase. The interfacial electron transfer between the DMFC and the [AuCl₄]^? ions leads to deposition of metallic gold nanoparticles at the liquid–liquid interface. The structure and features of the deposited Au nanoparticles were studied by means of microscopic and voltammetric techniques. The morphology of the Au deposit depends on the concentration ratio of redox partners and both electrode and liquid–liquid interfacial potential differences. Depending on whether the Au deposit was obtained by ex situ (at open circuit potential) or by “in situ” (by cycling of the electrode potential) approach, we observed quite different effects to the ion transfer reactions probed by the thin-film electrode set-up. The possible reasons for the different behavior of the Au nanoparticles are discussed in terms of the structure and the properties of the obtained Au deposit. In separate experiments, we have demonstrated catalytic effects of the Au nanoparticles towards enhancing the electron transfer between DMFC and two aqueous redox substrates, hexacyanoferrate and hydrogen peroxide.     

Hyperbranched polyesterpolyols as components of amperometric monoamine oxidase biosensors based on electrodes modified with nanomaterials for determination of antidepressants

The use of hyperbranched polyesterpolyols of different generations favors firmer fixation of carbon nanotubes and silver nanoparticles as components of composite materials on the electrode surface (0.028 mg cm^–2), which improves the operation characteristics of monoamine oxidase biosensors. The size of silver nanoparticles (18–52 nm) depends on the conditions for preparing hyperbranched polyesterpolyols, and their use as electrode modifiers influences the analytical possibilities of amperometric biosensors. Silver nanoparticles (18 nm, data of atomic force microscopy) in polyesterpolyols of third generation (pH 10.0) as components of the developed biosensors extend the interval of determinable concentrations to 1 × 10^–4–1 × 10^–8 M and decrease the lower limit of determination to 3 × 10^–9 M, compared to the unmodified sensors, owing to enhancement of the analytical signal. The developed biosensors were tested in monitoring of drugs (antidepressants) in Coaxil and Auroriks drug forms with the relative standard deviation on the level of 0.052.     

Influence of Polar Modifiers on Microstructure of Polybutadiene Obtained by Anionic Polymerization. Part 1: Lewis Base (σ) Amine-Type Polar Modifiers

In order to understand the influence of various types of polar modifiers on the microstructure of polybutadiene obtained by anionic polymerization, four types of polar modifiers were selected for detailed studies: Lewis bases (σ complex), Lewis acids (μ complex), a mixture of Lewis bases and Lewis acids (σ + μ complex), and acid-base polar modifiers (σ-μ complex) where one molecule combined acid and base character. The influence of five different tertiary amines (Lewis base polar modifiers) was studied. Analysis of FT-IR-ATR, ¹H, and ¹³C NMR data for polybutadienes obtained in the presence of these complexing agents showed that all tested tertiary amines enhanced 1,2 addition of 1,3-butadiene and preferred trans-1,4 addition.     

Electrochemical Morphine Sensor Based on Gold Nanoparticles Metalphthalocyanine Modified Carbon Paste Electrode

Composites of gold nanoparticles (Au) electrochemically deposited and different metal phthalocyanines (Co, Ni, Cu, and Fe) were chemically prepared. The composites were used as modifiers for carbon paste electrodes and were used for the determination of morphine in presence of ascorbic acid and uric acid. Central metal atoms of phthalocyanine moiety affected the rate of electron transfer. Thus, the electroactivity of different modifiers were evaluated towards morphine oxidation. Au‐CoPcM‐CPE possessed the highest rate for charge transfer rate in all studied pH electrolytes. Limit of detection was 5.48×10^?9 mol L^?1 in the range of 4.0×10^?7 to 9.0×10^?4 mol L^?1.     

Whisker nanohydroxyapatite synsthesis in casein medium and the effect of protein solution concentration on the morphology and structure of nanohydroxyapatite

The means of hydroxyapatite nanoparticles (n-HAP) preparation in biopolymer modifiers solutions under ultrasonic activation have been investigated. The use of casein as a modificator was suggested. It was shown that a protein solution with a concentration of 0.2% provides whisker n-HAP with a diameter of 2 nm and a length of 10 nm. This size of n-HAP is correlated to colloidal calcium phosphate in milk casein micelles. Synthesized nanoparticles can be used for the intensification of technologies processes in the dairy industry and for the fortification of food with calcium in the natural form.     

“非保护型”金属胶体纳米簇形成机理研究

碱-乙二醇法制备的"非保护型"金属及合金纳米簇由表面吸附的溶剂分子和简单离子实现稳定化,它们被广泛用于制备高性能复相催化剂和研究复相催化剂中的尺寸、组成、载体表面基团以及修饰剂对催化性能的影响。关于此类非保护金属纳米簇的形成过程及机理的认识尚有待进一步深化。本文采用原位快速扫描X射线吸收精细结构谱(QXAFS)、原位紫外-可见(UV-Vis)吸收光谱、透射电子显微镜和动态光散射技术研究了碱-乙二醇法合成中非保护型金属胶体纳米簇的形成过程与机理。结果表明,在碱-乙二醇法合成非保护型Pt金属纳米簇的过程中,室温下即有部分Pt(IV)被还原至Pt(II)。随着反应温度的升高,OH-逐渐取代与Pt离子配位的Cl-,在Pt―Pt键形成之前,反应体系的UV-Vis吸收光谱中可观察到明显的纳米粒子的散射信号,原位QXAFS分析表明Pt纳米簇是由Pt氧化物纳米粒子还原所形成的;在Ru金属纳米簇的形成过程中,OH-首先取代了Ru Cl_3中的Cl~-,形成羟基配合物Ru(OH) _6~(3-),后者进一步缩合形成氧化钌纳米粒子,最终Ru金属纳米簇由乙二醇还原氧化钌纳米粒子形成。由于先形成了氧化物纳米粒子,后续的还原反应被限制在氧化物纳米粒子内,使最终得到的非保护型金属纳米簇具有尺寸小、分布窄的特点。本工作所获得的知识对发展高性能能源转化催化剂、精细化学合成催化剂、传感器等功能体系具有重要意义。     

Specifics of the preparation of anisotropically shaped gold nanoparticles in triton X-100 reverse micelles

The influence of the form of micelles and reactant concentrations on the formation and growth of gold nanoparticles in reverse micelles based on Triton X-100 (polyoxyethylene octyl phenyl ether) was studied. It was shown that spherical nanoparticles of 3–4 nm in size are formed in the presence of sodium sulfite and ascorbic acid and particles of an extended shape are formed in the presence of ascorbic acid alone. It was found that the ultimate shape and size of the nanoparticles depend not only upon the form of micelles but also on the acid concentration, since the products of its oxidation can be selectively sorbed on the surface of the particles and act as additional shape modifiers.     

Evaluation of different permanent modifiers for the determination of arsenic in environmental samples by electrothermal atomic absorption spectrometry

Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W-Rh, W-Ru, W-Ir) permanent modifiers thermally deposited on the integrated platform of transversally heated graphite atomizer were employed for the determination of arsenic in sludges, soils, sediments, coals, ashes and waters by electrothermal atomic absorption spectrometry. Microwave digests of solid samples and water samples were employed for obtaining the analytical characteristics of the methods with different permanent modifiers. The performance of the modifiers for arsenic determination in the real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for the analyte determinations in simpler matrices such as waters (recoveries of certified values 95-105%), but the analyte recoveries of certified values in sludges, soils, sediments, coals, and ashes were always lower than 90%. On the other hand, for the determination of arsenic, using W-Rh, W-Ru, and W-Ir permanent modifiers presented recoveries of certified values within 95-105% for all the samples. Long-term stability curves obtained for the determination of arsenic in environmental samples with different permanent modifiers (Rh, Ir, Ru, W-Rh, W-Ir, W-Ru) showed that the improvement in the tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 35% longer when compared with single permanent modifier. The results for the determination of As employing different permanent modifiers in the samples were in agreement with the certified reference materials, since no statistical differences were found after applying the paired t-test at the 95% confidence level.     

Effects of organic modifiers on solute retention and electrokinetic migrations in micellar electrokinetic capillary chromatography.

Influences of seven organic modifiers, including urea, methanol (MeOH), dioxane (DIO), tetrahydrofuran (THF), acetonitrile (ACN), 1-propanol (1-PrOH) and 2-propanol (2-PrOH), on the solute retention and the electrokinetic migrations in micellar electrokinetic capillary chromatography (MEKC) are investigated with sodium dodecyl sulfate (SDS) micelle as pseudostationary phase. It is observed that in the limited concentration ranges used in the MEKC systems the effect of organic modifier concentration on the retention can be described by the equation logk1=logk1w-SC for most binary aqueous-organic buffer, but deviations from this retention equation are observed at ACN and particularly THF as organic modifiers. With parameter S as a measure of the elutropic strength, the elutropic strength of the organic modifiers is found to follow a general order urea 相似文献