Synthesis of polypyrrole-coated core/shell nanoparticles

The synthesis, physical characterization and scale-up of conductive, re-dispersible core/shell nanoparticles containing polypyrrole (PPy) in the shell are described. The compressed powders/films show a DC conductivity which is considerably higher than that of commercial standard products based on PEDOT/PSS ('AL 4083' from H.C. Starck). The particles have excellent film-forming properties since thin films (50-100 nm) made by spin-coating from aqueous dispersions of the particles have an AFM film roughness of <15 nm even before annealing. The materials were tested as hole injection/smoothening layers in fluorescent OLED devices, and are in a comparable range to PEDOT/PSS-based materials in respect to performance (film forming, luminance, efficiency, and lifetime).     

一种核/壳型纳米粒子的制备与表征

以PCL(聚己内酯)和PEG(聚乙二醇)为初始原料合成了PECL(PEG-PCL-PEG)两亲性三嵌段共聚物,并通过PECL的端羟基与丙烯酰氯的缩合反应向PECL中引入了双键。研究结果表明:该两亲性PECL在水相环境中可自组装形成表面带有大量双键的纳米粒子;PECL与丙烯酰氯缩合反应后,可将C=C双键成功引入至三嵌段共聚物中;PECL纳米粒子为核/壳状球形结构。     

Novel method for synthesis of Fe core and C shell magnetic nanoparticles

Using a newly developed method, carbon-encapsulated iron (Fe) nanoparticles were synthesized by plasma due to ultrasonication in toluene. Fe core with carbon shell nanoparticles were characterized using Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM). Fe nanoparticles of diameter 7–115 nm are encapsulated by 7–8 nm thick carbon layers. There was no iron carbide formation observed between the Fe core and the carbon shell. The Fe nanoparticles have body centered cubic (bcc) crystal structure. Synthesized nanoparticles showed a saturation magnetization of 9 A m²/kg at room temperature. After thermal treatment crystalline order of the nanoparticles improved and saturation magnetization increased to 24 A m²/kg. We foresee that the carbon-encapsulated Fe nanoparticles are biologically friendly and could have potential applications in Magnetic Resonance Imaging (MRI) and photothermal cancer therapy.     

核壳聚合物微球的制备方法及应用

综述了近年来核壳结构聚合物微球制备方面的研究进展,介绍了乳液法、自组装法、模板法、沉积法等主要制备方法,阐述了各种方法所涉及的机理.介绍了目前核壳聚合物微球的应用现状,如制备中空微球、用磁性核壳微球提高医学诊断的准确率及作为填料改性聚合物等,表明核壳微球有着广阔而重要的应用前景.     

核／壳型可遮盖聚合物乳液的研制

采用了种子乳液聚合法,以可被碱溶胀的丙烯酸类聚合物为核,交联型的丙烯酸类高聚物为壳,合成了新型的可以代替部分钛白粉等颜料的可遮盖聚合物。讨论了乳化剂、单体、核壳比等对聚合物性能的影响,其中核壳比在1:15-1:25时,聚合物具有较好的遮盖效果。     

Factorial experimental design on synthesis of functional core/shell polymeric nanoparticles via differential microemulsion polymerization

Functionalized core/shell nanoparticles of the co‐polymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) could be polymerized by differential microemulsion polymerization, using a small amount of surfactant (the weight ratio of sodium dodecyl sulfate (SDS)/monomer is 1 : 24). The core/shell nanoparticles have a high conversion, high molecular weight, and small particle size (25–30 nm). The statistical analysis indicated that SDS, water, and the interactionbetween SDS and water have a significant positive interaction between the MMA conversion to form the core nanoparticles. For the core‐shell polymer, [GMA], [GMA]*[SDS], and [GMA]* [water] have significant negative effects on conversion; whereas [SDS] and [water], [SDS]*[water] and [GMA]*[SDS]*[water] have positive effects on the conversion to form core/shell nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of polystyrene/polythiophene core/shell nanoparticles by dual initiation

Polystyrene/polythiophene (PSt/PTh) core/shell nanoparticles were successfully synthesized via a one-pot Fe³⁺-catalyzed oxidative and soap-free emulsion polymerization process. A small amount of sodium styrene sulfonate (NaSS) was used to maintain the colloidal stability of the PSt/PTh nanoparticles. Hydrogen peroxide (H₂O₂) and a trace of iron chloride (FeCl₃) were used to carry out the free-radical polymerization of styrene and the oxidative polymerization of thiophene. The dual initiation characteristics of H₂O₂/FeCl₃ in the PSt/PTh core/shell nanoparticle formation were investigated by observing the time-evolution of the particle morphology. In addition, photoluminescent property, particle size distribution, core/shell morphology and the formation mechanism of the PSt/PTh nanoparticles were studied by spectrofluorophotometery, dynamic light scattering (DLS), in-situ IR, zeta-potential, and time-evolution field-emission scanning electron microscope (FE-SEM) analyses.     

Fabrication of polymer/ZnS nanoparticle composites by matrix-mediated synthesis

Zinc sulfide nanoparticles are obtained as primary particles in a polymer matrix by a matrix-mediated synthesis. Two types of matrix polymer are synthesized via the copolymerization of hydrophobic, cation-exchange, and cross-linking monomers. The ZnS nanoparticles are affected by the composition of the matrix polymer, and especially by its hydrophobicity. In a low-hydrophobicity copolymer matrix, aggregates of ZnS nanoparticles are observed in the matrix using transmission electron microscopy (TEM) and X-ray diffraction (XRD). In a high-hydrophobicity cation-exchange copolymer matrix, primary particles of ZnS with 2–5 nm diameters are observed in the matrix by TEM. However, the ZnS pattern is not distinguishable in XRD measurements because the particle sizes are too small to diffract X-rays.     

Multicolor core/shell silica nanoparticles for in vivo and ex vivo imaging

Biocompatible highly bright silica nanoparticles were designed, prepared and tested in small living organisms for both in vivo and ex vivo imaging. The results that we report here demonstrate that they are suitable for optical imaging applications as a possible alternative to commercially available fluorescent materials including quantum dots. Moreover, the tunability of their photophysical properties, which was enhanced by the use of different dyes as doping agents, constitutes a very important added value in the field of medical diagnostics.     

Cation-exchange membrane as nanoreactor: Intermatrix synthesis of platinum–copper core–shell nanoparticles

The physical and chemical properties of metal nanoparticles (MNPs) are distinct from those of both bulk metal and isolated atoms. The main drawback of MNP is their instability and high trend for aggregation. Without stabilization they fuse together, losing their special shape and properties. The development of polymer-stabilized MNPs (PSMNPs) is one of the most promising solutions to MNP stability problem. In this paper we report in situ synthesis and characterization of PSMNPs, using the ion-exchange membranes as a nanoreactor. The membranes were prepared by using sulfonated poly(etherether ketone) of desired sulfonation degree (SD). The optimal SD provided a sufficiently high ion-exchange capacity and insolubility of the polymer in water and solubility in organic solvents (DMF). The membrane was loaded with metal ions (e.g., Cu²⁺) or complexes (e.g., [Pt(NH₃)₄]²⁺) followed by metal reduction inside the polymer matrix resulting in formation of either monometallic or bimetallic PSMNPs with core–shell structure. The MNP-containing membranes were characterized by electron microscopy to evaluate the morphological changes of the membranes and to estimate the MNPs size. The same membranes were also deposited on the surface of graphite–epoxy composite electrodes to study the electrochemical properties of polymer-PSMNP composites and to estimate their applicability in sensor designs. The presence of both Cu- and Pt/Cu-PSMNPs inside the membrane not only substantially improves the electric conductivity of the polymer, but also testifies to the clearly pronounced strong electrocatalytic activity of PSMNPs towards analyte under study (H₂O₂).     

Hybrid light-emitting diodes from anthracene-contained polymer and CdSe/ZnS core/shell quantum dots

In this paper, we added CdSe/ZnS core/shell quantum dots (QDs) into anthracene-contained polymer. The photoluminescent (PL) characteristic of polymer/QD composite film could identify the energy transitions of anthracene-contained polymer and QDs. Furthermore, the electroluminescent (EL) characteristic of hybrid LED also identifies emission peaks of blue polymer and QDs. The maximum luminescence of the device is 970 cd/m² with 9.1 wt.% QD hybrid emitter. The maximum luminous efficiency is 2.08 cd/A for the same device.     

Nanoscale semiconductor-insulator-metal core/shell heterostructures: facile synthesis and light emission

Controllably constructing hierarchical nanostructures with distinct components and designed architectures is an important theme of research in nanoscience, entailing novel but reliable approaches of bottom-up synthesis. Here, we report a facile method to reproducibly create semiconductor-insulator-metal core/shell nanostructures, which involves first coating uniform MgO shells onto metal oxide nanostructures in solution and then decorating them with Au nanoparticles. The semiconductor nanowire core can be almost any material and, herein, ZnO, SnO(2) and In(2)O(3) are used as examples. We also show that linear chains of short ZnO nanorods embedded in MgO nanotubes and porous MgO nanotubes can be obtained by taking advantage of the reduced thermal stability of the ZnO core. Furthermore, after MgO shell-coating and the appropriate annealing treatment, the intensity of the ZnO near-band-edge UV emission becomes much stronger, showing a 25-fold enhancement. The intensity ratio of the UV/visible emission can be increased further by decorating the surface of the ZnO/MgO nanowires with high-density plasmonic Au nanoparticles. These heterostructured semiconductor-insulator-metal nanowires with tailored morphologies and enhanced functionalities have great potential for use as nanoscale building blocks in photonic and electronic applications.     

A simple one‐step chemical route to gold/polymer core/shell composites and polymer hollow spheres

Au/poly(o‐toluidine) (POT) core/shell composite spheres have been successfully fabricated by chemical polymerization route in aqueous solution without the aid of surfactant or functional acids using HAuCl₄ as the oxidant. By altering the concentration of oxidant, the amount of Au nanoparticles inside each POT sphere can be tuned from tens to one. Moreover, uniform POT hollow spheres with one opening in each polymer surface can be obtained under extremely low concentration of oxidant. The chemical structures of Au/POT composites were confirmed by Fourier transform infrared (FTIR), UV‐vis, and X‐ray diffraction (XRD) spectroscopies. Moreover, the formation mechanisms of Au/POT core/shell composites and POT hollow spheres were also discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Combined plasma gas-phase synthesis and colloidal processing of InP/ZnS core/shell nanocrystals

Indium phosphide nanocrystals (InP NCs) with diameters ranging from 2 to 5 nm were synthesized with a scalable, flow-through, nonthermal plasma process at a rate ranging from 10 to 40 mg/h. The NC size is controlled through the plasma operating parameters, with the residence time of the gas in the plasma region strongly influencing the NC size. The NC size distribution is narrow with the standard deviation being less than 20% of the mean NC size. Zinc sulfide (ZnS) shells were grown around the plasma-synthesized InP NCs in a liquid phase reaction. Photoluminescence with quantum yields as high as 15% were observed for the InP/ZnS core-shell NCs.     

Microwave-assisted synthesis of water-dispersed CdTe/CdSe core/shell type II quantum dots

A facile synthesis of mercaptanacid-capped CdTe/CdSe (core/shell) type II quantum dots in aqueous solution by means of a microwave-assisted approach is reported. The results of X-ray diffraction and high-resolution transmission electron microscopy revealed that the as-prepared CdTe/CdSe quantum dots had a core/shell structure with high crystallinity. The core/shell quantum dots exhibit tunable fluorescence emissions by controlling the thickness of the CdSe shell. The photoluminescent properties were dramatically improved through UV-illuminated treatment, and the time-resolved fluorescence spectra showed that there is a gradual increase of decay lifetime with the thickness of CdSe shell.     

聚合物/SiO2核壳结构单分散微球的制备

聚合物/SiO2核壳结构单分散微球比聚合物微球具有更好的稳定性,有望在较高的温度和有机溶剂中得到使用.为了制备出这种微球,作为模板的聚合物微球首先进行表面胺化处理,然后正硅酸乙酯被诱导在其表层水解缩合从而形成SiO2壳层;采用扫描电子显微镜(SEM)、傅里叶红外光谱仪(FTIR)、激光粒度仪,烧蚀质量损失等手段分析表征...     

Morphological prediction and its application to the synthesis of polyacrylate/polysiloxane core/shell latex particles

A theoretical analysis and a morphological prediction of polyacrylate (PA)/polysiloxane (PSi) latex particles with core/shell morphologies were first conducted based on interfacial tensions and relative volumes of the two polymers in the latex system. The results indicated that the normal core/shell morphology particles (PSi/PA), with hydrophobic polysiloxane as the core and with hydrophilic polyacrylate as the shell, can be easily formed. Although the inverted core/shell morphology particles (PA/PSi) with polyacrylate as the core could not be formed in most cases, even if the fraction volume of polysiloxane was larger than 0.872, which is the smallest value of forming a PA/PSi particle, the PSi/PA particles were unavoidably formed simultaneously with PA/PSi particle formation. The synthesis of PA/PSi particles containing equal amounts of polyacrylate and polysiloxane was then carried out using seeded emulsion polymerization. Before the cyclosiloxane cationic polymerization, 3‐methacryloyloxypropyl trimethoxysilane (MATS) was introduced into the polyacrylate seed latex to form an intermediate layer and chemical bonds between the core and the shell polymers. The characterization by transmission electron microscopy (TEM) demonstrated that the perfect PA/PSi core/shell particle is successfully synthesized when both the core and the shell polymers are crosslinked. The experiments showed that both the hardness and water adsorption ratio characteristics of latex films of the PA/PSi particles are in good agreement with those of the polysiloxane film. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2251–2258, 2001     

核壳PBA/PMMA乳液粒径分布规律与壳层聚合研究

通过半连续饥饿态法合成了核壳型PBA/PMMA乳液,并利用激光粒度仪时实监控壳层聚合阶段粒子粒径变化,结合理论数学计算模型,研究了壳层单体加料速度与补加乳化剂的量对平均数均粒径及其分布与总粒子数的影响.理论计算乳液中的总粒子数的变化规律和对比反应前后粒径大小,并通过傅立叶红外光谱证实了核壳结构的存在.核壳聚合中壳层聚合机理为单体在加入种子核乳液过程中大部分先在水相中均相成核形成PMMA低聚物,随后由于表面吸附作用而迁移到PBA核表面成为活性中心继续聚合成为壳层.     

Preparation and characterization of titanium dioxide core/polymer shell hybrid composite particles prepared by emulsion polymerization

Titanium dioxide inorganic core and polymer shell composite poly(methyl methacrylate‐co‐butylacrylate‐co‐methacrylic acid) [P(MMA‐co‐BA)‐MAA] particles were prepared by emulsion copolymerization. Fourier transform IR (FTIR) spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering (DLS) characterized the composite particle size and size distribution. The field emission SEM (FE‐SEM) results of the composite particles showed regular spherical shape and no bare TiO₂ was detected on the whole surface of the samples. The composite particles were produced, showing good spectral reflectance compared with bare TiO₂. TGA results indicated the encapsulation efficiency and estimated density of composite particles. Encapsulation efficiency was up to 78.9% and the density ranged from 1.76 to 1.94 g/cm³. Estimated density of the composite particles is suitable to 1.73 g/cm³, due to density matching with suspending media. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2970–2975, 2004