Preparation and characterization of low dispersity anionic multiresponsive core-shell polymer nanoparticles

We prepared anionic multistimuli responsive core-shell polymer nanoparticles with very low size dispersity. By using either acrylic acid (AA) or methacrylic acid (MA) as a comonomer in the poly(N-isopropyl acrylamide) (PNIPAM) shell, we are able to change the distribution of negative charges in the nanoparticle shell. The particle size, volume phase transition temperature, and aggregation state can be modulated using temperature, pH, or ionic strength, providing a very versatile platform for applications in sensors, medical diagnostics, environmental remediation, etc. The nanoparticles have a glassy poly(methyl methacrylate) (PMMA) core of ca. 40 nm radius and a cross-linked PNIPAM anionic shell with either AA or MA comonomers. The particles, p(N-AA) and p(MA-N), respectively, have the same total charge but different charge distributions. While the p(MA-N) particles have the negative charges preferentially distributed toward the inner shell, in the case of the p(N-AA) particles the charge extends more to the particle outer shell. The volume phase transition temperature (T(VPT)) of the particles is affected by the charge distribution and can be fine-tuned by controlling the electrostatic repulsion on the particle shell (using pH and ionic strength). By suppressing the particle charge we can also induce temperature-driven particle aggregation.     

SiO2@Fe2O3核-壳结构催化剂的制备及表征

采用优化的Stöber法制备了平均粒径为230 nm的单分散球形SiO₂颗粒,并以此为内核,通过水解沉积法制备了不同壳层厚度的核-壳结构SiO₂@Fe₂O₃催化剂。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂物理吸附和X射线衍射分析(XRD)等手段对催化剂进行表征,探讨了不同制备条件对SiO₂@Fe₂O₃催化剂形貌的影响。结果表明,通过水解沉积法制备的SiO₂@Fe₂O₃催化剂具有明显的核-壳结构,并且保持了原始SiO₂核的球形形貌,Fe₂O₃纳米粒子通过-OH的氢键作用连接在SiO₂表面,形成了2~10 nm厚的Fe₂O₃均匀连续包覆层。     

Decreasing the shell ratio of core-shell type nanoparticles with a ceria core and polymer shell by acid treatment

Core-shell type nanoparticles with a ceria core and polymer shell have good dispersibility. Some applications, such as fillers for increasing the refractive index and/or protecting resin films from ultraviolet (UV) light, i.e., UV cutting, require a smaller shell. Previous studies have decreased the shell weight by heat treatment in gas; however, the dispersibility of the treated nanoparticles was poor in water or alcohol. In this study, we investigated the efficacy of acid treatment for decreasing the shell weight and also evaluated the dispersibility of acid-treated nanoparticles. The thus-formed nanoparticles treated by acetic acid and formic acid show not only good dispersibility but also a well decreased shell thickness. The structure of the shell after acetic acid treatment was found to be the same as that of the untreated core-shell nanoparticles; moreover, acetic acid was present in the shell. Furthermore, by using the acetic-acid-treated nanoparticles, a transparent resin film without nanoparticle aggregation could be obtained.     

Preparation and characterization of polymer composite multilayers on SiO2

Poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) have been consecutively adsorbed onto 1.5-microm charged silica (SiO2) particles. Time-dependent adsorption studies indicate that, due to the strong ionic charge of the dissociated polycation in water, adsorption is complete in less than 30 min. Indications of the maximum adsorption density, changes in surface charge, and stability of the layered particles are demonstrated through adsorption isotherms and electrophoretic mobility (EPM) measurements. Further stability of the PDADMAC layer is demonstrated through multiwashing with ultra pure deionized water. Preliminary desorption studies of the PSS layer also illustrate a stabilized two-layer system. Due to the nature of the electrostatic charges on the surface of the SiO2 core particles and both polyelectrolytes in aqueous media, the use of polyelectrolytes as layering elements serves as a model for the assembly of time-released drug delivery particle systems.     

Preparation and characterization of cross-linked β-cyclodextrin polymer/Fe_3O_4 composite nanoparticles with core-shell structures

Cross-linkedβ-cyclodextrin polymer/Fe₃O₄ composite nanoparticles with core-shell structures were prepared via cross linking reaction on the surface of carboxymethylβ-cyclodextrin（CM-β-CD） modified Fe₃O₄ nanoparticles inβ-cyclodextrin alkaline solution by using epichlorohydrin as crosslinking agent.The morphology,structure and magnetic properties of the prepared composite nanoparticles were investigated by transmission electron microscopy（TEM）,Fourier transform infrared（FTIR） spectrometry,X-ray diffraction（XRD） measurement,thermogravimetric analysis（TGA） and Vibrating sample magnetometry （VSM）,respectively.     

Preparation and characterization of core-shell nanoparticles hardened by gamma-ray

Core-shell nanoparticles have been prepared by irradiation of gamma-ray on block copolymer micelles consisting of hydrophilic polyacrylic acid and hydrophobic polyisoprene with each 40 monomer units. The structure was determined by means of dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The size distribution of the core-shell nanoparticles determined by DLS and AFM was very narrow. The average diameter of the particles decreased from 48 nm for the original micelles to 26 nm by the irradiation of 30 kGy. The core size determined by SAXS combined with DLS was roughly constant of 10 nm, irrespective of irradiation dose, whereas the shell thickness of the micelles was twice as large as the core size, and decreased with increasing irradiation dose.     

Noncovalent imprinting in the shell of core-shell nanoparticles

Propranolol was imprinted using noncovalent interactions in the shell of core-shell nanoparticles prepared by aqueous emulsion polymerization in the presence and absence of toluene. The imprinted particles were characterized, and their capacity to rebind propranolol from both organic and aqueous media was analyzed. Results showed that the amount of template incorporated into the polymer and the presence of toluene as a "porogenic" agent influenced the ability of the nanoparticles obtained to rebind propranolol. The presence of toluene during imprinting increased rebinding by about 2-fold in buffer and by 3-fold in toluene, compared with similar materials made in the absence of toluene during imprinting. It also influenced the final surface area of the particles. Binding site affinity, assessed by radioligand displacement, was measured as IC50 values of about 1-10 microM. This compares with about 3 microM for bulk polymer made with a similar composition. Finally, to demonstrate the advantages of structured particles for analytical applications a new property, fluorescence, was incorporated into the core of the particles without interfering with the imprinted shell and its ability to rebind propranolol.     

XPS characterization of Au (Core)/SiO2 (shell) nanoparticles

Core-shell nanoparticles with ca. 15-nm gold core and 6-nm silica shell were prepared and characterized by XPS. The Au/Si atomic ratio determined by XPS is independent of the electron takeoff angle because of the concentric spherical shape of the nanoparticles. The formula given by Wertheim and DiCenzo (Phys. Rev. B 1988, 37, 844) for spherical nanoparticles and the modified one by Yang et. al. (J. Appl. Phys. 2005, 97, 024303) for core-shell nanoparticles are used to correlate the XPS-derived composition with the geometry of the nanoparticles only after significantly modifying either the bulk density of the silica shell or the attenuation length of the photoelectrons.     

Synthesis and characterization of iron oxide/polymer composite nanoparticles with pendent functional groups

We describe in this paper an approach to synthesize superparamagnetic iron oxide nanoparticles in the presence of polymerized lactic acid. The resulted particles consisted of clusters of iron oxide monocrystals, embedded inside the polymer chains. The composite particles synthesized in situ were highly dispersible in aqueous solution with good stability. X-ray diffraction and magnetometer data all confirmed the crystalline structure and super-paramagnetic property of the particles. They exhibited narrow size distribution with hydrodynamic diameters close to 80 nm. In addition, the particles were shown to have abundant surface carboxyl groups, which can be used to conjugate various biomolecules. Such a preparation would be especially useful for developing target specific MRI contrast agents or drug delivery vehicles.     

Preparation and Z-Scan nonlinear optical characterization of Au/SiO2- and Ag/SiO2-supported nanoparticles dispersed in silica sonogel films

Au/SiO₂ and Ag/SiO₂ supported metal-nanoparticles (MNPs) were implemented to fabricate SiO₂-based inorganic?Cinorganic hybrid sonogel films. Prepared Au/SiO₂- and Ag/SiO₂-MNPs exhibited low 2D-HCP crystallinity with particle diameters below 10?nm and homogeneous size distribution. The catalyst-free (CF) sonogel route was successfully implemented to produce these optically active nanocomposite films by doping the liquid sol-phase with these MNP systems and its subsequent deposition onto glass substrates via standard spin-coating procedures. The easy MNP-loading within the mesoporous dielectric sonogel network evidenced a huge chemical affinity between the silica sonogel hosting system and the guest SiO₂-supported MNPs. This fact allowed us to fabricate high quality hybrid films suitable for cubic nonlinear optical (NLO) characterizations via the Z-Scan technique. Indeed, the hosting sonogel network provided adequate thermal and mechanical stability protecting the active MNPs from environment conditions and diminished their tendency to aggregate; thus, preserving their pristine optical properties and morphology, giving rise to stable sol?Cgel hybrid films appropriate for photonic applications. Comprehensive morphological, structural, spectroscopic and nonlinear photophysical characterizations were optimally performed to the developed hybrid films. Our results have shown that the crystalline nature of the implemented MNPs, their small sizes and appropriate guest?Chost stabilizing interactions play a crucial role in the observation of improved cubic NLO-properties of these MNP structures embedded within the highly pure CF-sonogel confinement.     

Preparation of micron-size monodisperse polymer microspheres having cationic groups

Micron-size monodisperse crosslinked polymer microspheres having chloromethyl groups were prepared by seeded copolymerization of styrene, divinylbenzene, and chloromethylstyrene in the presence of 2.1- monodisperse polystyrene seed particles produced by dispersion polymerization. The modification reaction of chloromethyl groups on the surfaces with polyamines such as triethylenetetramine and ethylenediamine was carried out. From the measurements of potential and the amount of chloride ion released, the introduction of a large number of cationic groups at the surfaces was confirmed.Part CXXXI of the series Studies on suspension and Emulsion.     

一种具有核-壳结构的聚合物纳米胶粒的制备及其药物运载性能

以丙烯酸异丁酯(IBA)、甲基丙烯酸二甲氨乙酯(DMAEMA)、丙烯酸羟乙酯(HEA)作为聚合单体,利用种子微乳液聚合制备了一种具有核-壳结构的聚合物纳米胶粒P(DMAEMA-co-IBA)/P(IBA-co-HEA);采用红外光谱仪、动态激光光散射仪、透射电镜分析了所得胶粒的结构和形貌;将叶酸成功嵌入聚合物胶粒,得到直径约293nm的球形载药胶粒,利用药物体外释放测定了药物运载性能.结果表明,所制备的共聚物纳米胶粒呈球形,直径约275nm,粒径分布较窄,并具有核-壳结构;其对药物具有缓释性和pH响应性.     

Preparation and characterization of epoxy/SiO2 nanocomposites by cationic photopolymerization and sol–gel process

Epoxy/SiO₂ nanocomposite materials were prepared by cationic photopolymerization and sol–gel process using a novel epoxy oligomer (EP‐Si(OC₂H₅)₃) prepared by 3‐isocyanatopropyltriethoxysilane (IPTS)‐grafted bisphenol A epoxy resin and tetraethyl orthosilicate as inorganic precursor. The chemical structures of EP‐Si(OC₂H₅)₃ were characterized by Fourier transformed infrared spectroscopy. Transmission electron microscopy showed that the in situ generated nano‐SiO₂ dispersed uniformly in the EP matrix, and its average diameter is around 40 nm. The relationship between nanocomposite materials' thermal/mechanical properties and nano‐SiO₂ introduced were studied by thermogravimetric analysis, dynamic mechanical analysis, and impact strength test. The results showed that the nanocomposite materials' thermal and mechanical properties improved a lot with increase of the SiO₂ content. Copyright © 2013 John Wiley & Sons, Ltd.     

Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively.     

Preparation and characterization of CuO/SiO2 and NiO/SiO2 with bimodal pore structure by sol-gel method

CuO/SiO₂ and NiO/SiO₂ with bimodal pore structure were prepared by sol-gel reactions of Tetra-methoxysilane (TMOS) and the respective metal nitrate in the presence of poly (ethylene oxide) (PEO) with an average molecular weight of 10 000 and the catalyst of acetic acid. In this process, the interconnected macroporous morphology was formed when transitional structures of spinodal decomposition were frozen by the sol-gel transition of silica. The addition of copper and nickel into the silica-PEO system had a negligible effect on the morphology formation. In gel formation, it was found that NiO crystalline sizes in the samples increased with decreasing Si/Ni molar ratio. It was considered that PEO interacted with both silica and nickel cations. In the CuO/SiO₂ with the presence of PEO_, CuO crystalline sizes were larger than those of NiO/SiO_2. It was considered that there was no obvious interaction between the Cu cation and PEO, most of the copper ions in wet silica gel were present in the outer solution. They easily aggregated as copper salts in the drying process of wet gel and decomposed into CuO particles in heating. While in the CuO/SiO₂ with the absence of PEO, the Cu was selectively entrapped as small particles in the gel skeleton due to the interaction between Cu aqua complex and silica gel network.     

Synthesis and characterization of SiO2/Gd2O3:Eu core-shell luminescent materials

Europium-doped Gd2O3 with an average size of approximately 15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.     

魔芋葡甘聚糖／SiO2纳米复合物的制备与表征

用纳米SiO2为原料,以魔芋葡甘聚糖(KGM)为基体,采用共混法制得KGM/SiO2纳米复合物。通过傅立叶红外光谱(FTIR)、热重分析(TG)、透射电镜(TEM)等手段对该体系进行了表征。结果表明:由于纳米SiO2粒子的引入,KGM分子FTIR的某些特征峰的波数发生明显变化;纳米SiO2在复合物中的分散性较好;复合材料的热稳定性高于KGM薄膜;此外,复合材料的力学性能有所提高。     

Deposition of cationic polymer micelles on planar SiO2 surfaces

The deposition of PS-PVPH+ polymer micelles from a pH 1 aqueous solution onto Si wafers has been studied using a simple dip-coating technique. It has been found that the rate of evaporation of the solvent and the rate of withdrawal have a considerable influence on the density and ordering of the adsorbed micelles. The highest density and degree of ordering (as judged by the 2D pair correlation function) is achieved when solvent evaporation dominates the deposition process, but a fairly homogeneous distribution of polymer micelles can be achieved over a distance of at least 3-4 mm by controlling the solvent evaporation rate and the rate of substrate withdrawal. We did not observe any significant effect of added KCl (up to 0.1 M) during the deposition process or soaking in 1 M KCl after deposition. The attachment of these micelles is quite robust, as they cannot be washed off in pH 1 water (with or without KCl) without significant mechanical assistance. However, we did find that the micelles are rather easily caused to dewet and partially aggregate under the influence of 65 degrees C water vapor.     

Preparation and characterization of the antibacterial Cu nanoparticle formed on the surface of SiO2 nanoparticles

Cu deposition on the surface of spherical SiO2 nanoparticles was studied to achieve the hybrid structure of Cu-SiO2 nanocomposite. SiO2 nanoparticles served as seeds for continuous Cu metal deposition. The chemical structure and morphology were studied with X-ray photoelectron spectroscopy (XPS), scanning electron microscope energy dispersive X-ray (SEM-EDX), and a transmission electron microscope (TEM). The antibacterial properties of the Cu-SiO2 nanocomposite were examined with disk diffusion assays. The homogeneously formed Cu nanoparticles on the surface of SiO2 nanoparticles without aggregation of Cu nanoparticles showed excellent antibacterial ability.     

Preparation and characterization of multiresponsive polymer composite microspheres with core–shell structure

Fe₃O₄/SiO₂/poly (N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMA)] multiresponsive composite microspheres with core–shell structure were synthesized by template precipitation polymerization. First, the magnetite nanoparticles were coated with silica and then modified with 3-(trimethoxysilyl)-propyl methacrylate (MPS). Subsequently, the Fe₃O₄/SiO₂ particles grafted with MPS were used to seed the precipitation copolymerization of NIPAM and DMA. The composite microspheres with core–shell structure were superparamagnetic, pH-sensitive, and thermoresponsive. The swelling ratio (D_{25 °C, pH = 3}/D_{50 °C, pH = 9})³ coupling of pH and temperature increased up to 21.2, which was much higher than that without comonomer DMA.