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Silica Shell (silica + shell)
Selected AbstractsA direct preparation of silica shell on polystyrene microspheres prepared by dispersion polymerization with polyvinylpyrrolidoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2008Jinho Hong PS/silica core/shell structured microspheres were easily prepared in a simple process. Because of the acid-base interaction between the TEOS and seed particles prepared by dispersion polymerization, uniform silica shell was formed on the PVP-stabilized PS particles without additional PVP-coating process. [source] Sonochemical Synthesis of Networked Silica Shell with Reduced Microporosity on Titania Nanocores for Photocatalytic Activity ReductionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Ahmed Mohamed El-Toni Silica shells with a high density of networks and reduced microporosity has been formed on titania nanocores via a sonochemical approach in the absence of ammonia as a hydrolyzing catalyst. The TiO2 -silica core-shell nanoparticles were characterized by transmission electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy (FTIR), and microporosity measurements. The photocatalytic activity of coated titania was also reported. FTIR measurements showed that the silica shell was formed with a high density of networks through the formation of asymmetric Si,O,Si vibration and asymmetric Si,O,Si stretching vibration bonds. Moreover, the thickness and microporosity of the silica shell could be altered by controlling the sonochemical power and time parameters. [source] Encapsulation and Ostwald Ripening of Au and Au,Cl Complex Nanostructures in Silica Shells,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2006W. Lou Abstract We report a general template strategy for rational fabrication of a new class of nanostructured materials consisting of multicore shell particles. Our approach is demonstrated by encapsulating Au or Pt nanoparticles in silica shells. Other superstructures of these hollow shells, like dimers, trimers, and tetramers can also be formed by nanoparticle-mediated self-assembly. We have also used the as-prepared multicore Au,silica hollow particles to perform the first studies of Ostwald ripening in confined microspace, in which chloride was found to be an efficient mediating ligand. After treatment with aqua regia, Au,Cl complex is formed inside the shell, and is found to be very active under in,situ transmission electron microscopy observations while confined in a microcell. This aspect of the work is expected to motivate further in,situ studies of confined crystal growth. [source] Sonochemical Synthesis of Networked Silica Shell with Reduced Microporosity on Titania Nanocores for Photocatalytic Activity ReductionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Ahmed Mohamed El-Toni Silica shells with a high density of networks and reduced microporosity has been formed on titania nanocores via a sonochemical approach in the absence of ammonia as a hydrolyzing catalyst. The TiO2 -silica core-shell nanoparticles were characterized by transmission electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy (FTIR), and microporosity measurements. The photocatalytic activity of coated titania was also reported. FTIR measurements showed that the silica shell was formed with a high density of networks through the formation of asymmetric Si,O,Si vibration and asymmetric Si,O,Si stretching vibration bonds. Moreover, the thickness and microporosity of the silica shell could be altered by controlling the sonochemical power and time parameters. [source] Synthesis of Au@SiO2 Core/Shell Nanoparticles and their Dispersion into an Acrylic Photocurable Formulation: Film Preparation and CharacterizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2008Marco Sangermano Abstract Au core/silica shell (Au@SiO2) nanoparticles were synthesized by coating gold NPs with sol/gel silica in alcoholic solution. The alcoholic dispersion was added, in the range of 1,5 wt.-%, to TPGDA and photocured by means of UV light. Transparent coatings were obtained and they can find suitable applications. It was shown that the NPs can restrict the segmental motion and decrease the free volume of the polymer network, with a consequent increase in glass transition temperature. TEM analysis put in evidence that the particles are well dispersed without any macroscopic agglomeration, and many particles are present as isolated particles. [source] Generation of Monodisperse Inorganic,Organic Janus Microspheres in a Microfluidic DeviceADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Naveen Prasad Abstract This study presents a simple synthetic approach for the in situ preparation of monodisperse hybrid Janus microspheres (HJM) having organic and inorganic parts in a PDMS-based microfluidic device. Based on the mechanism of shear-force-driven break-off, merged droplets of two photocurable oligomer solutions having distinctive properties are generated into an immiscible continuous phase. Functionalized perfluoropolyether (PFPE) as the organic phase and hydrolytic allylhydridopolycarbosilane (AHPCS) as the inorganic phase are used for the generation in aqueous medium of HJM with well-defined morphology and high monodispersity (average diameter of 162,µm and a 3.5% coefficient of variation). The size and shape of the HJM is controlled by varying the flow rate of the disperse and continuous phases. The HJM have two distinctive regions: a hydrophobic hemisphere (PFPE) having a smooth surface and a relatively hydrophilic region (AHPCS) with a rough, porous surface. In addition, pyrolysis and subsequent oxidation of these HJM convert them into SiC-based ceramic hemispheres through the removal of the organic portion and etching off the silica shell. The selective incorporation of magnetic nanoparticles into the inorganic part shows the feasibility of the forced assembly of HJM in an applied magnetic field. [source] Two-Dye Core/Shell Zeolite Nanoparticles: A New Tool for Ratiometric pH MeasurementsADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Tristan Doussineau Abstract The preparation of core/shell nanoparticles that enable ratiometric pH measurement is described. The core of the nanoparticles consists of a zeolite- , matrix that exhibits a 3-hydroxyflavone reference dye within the porous network. Coating an amorphous silica shell containing a fluorosensor around the zeolite through the Stöber process provides pH sensitivity to the nanoparticles. Morphological characterization (dynamic light scattering, transmission electronic microscopy) demonstrates the control of the sensing silica shell around the zeolite cores, leading to highly monodisperse spherical nanoparticles, while structural characterization (wide-angle X-ray diffraction, nitrogen adsorption) shows the amorphous character of the shell. Spectral characterization via UV/Vis absorption and steady-state fluorescence shows good pH sensitivity of the resulting nanosensors with a pKa suitable for bioanalytical applications. [source] Cover Picture: Composite Silica Spheres with Magnetic and Luminescent Functionalities (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2006Mater. Abstract Photographs of a colloidal dispersion of composite nanoparticles with magnetic and luminescent functionalities are shown (left, in column), which are schematically illustrated in the main image. As reported by Salgueirińo-Maceira and co-workers on p.,509, such functionalities are imparted by magnetic and semiconductor nanoparticles within a silica matrix. In the absence of a magnetic field the particles are uniformly dispersed, although they accumulate and can be dragged under the influence of a magnetic field. Their movement can be monitored by their photoluminescence. A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles in the submicrometer size range has been synthesized from a modified Stöber method combined with the layer-by-layer (LbL) assembly technique. Luminescent magnetic nanoparticles are prepared via two main steps. The first step involves controlled addition of tetraethoxysilane to a dispersion of Fe3O4/,-Fe2O3 nanoparticles, which are thereby homogeneously incorporated as cores into monodisperse silica spheres. The second step involves the LbL assembly of polyelectrolytes and luminescent CdTe quantum dots onto the surfaces of the silica-coated magnetite/maghemite particles, which are finally covered with an outer shell of silica. These spherical particles have a typical diameter of 220,±,10,nm and a saturation magnetization of 1.34,emu,g,1 at room temperature, and exhibit strong excitonic photoluminescence. Nanoparticles with such a core/shell architecture have the added benefit of providing a robust platform (the outer silica shell) for incorporating diverse functionalities into a single nanoparticle. [source] Synthesis and Assembly of Monodisperse High-Coercivity Silica-Capped FePt Nanomagnets of Tunable Size, Composition, and Thermal Stability from Microemulsions,ADVANCED MATERIALS, Issue 19 2006Q. Yan A microemulsion approach to obtain high - coercivity (850 mT) FePt nanomagnets capped with a nanoscopic silica shell is reported (see figure). This versatile method allows the easy tuning of particle size and composition. The silica shell inhibits agglomeration and preserves the chemical stability of the particles up to 650,°C, and facilitates surface functionalization and particle assembly. These attributes are attractive for harnessing the nanomagnets for realizing novel devices and composites. [source] Aligned Gold Nanorods in Silica Made by Ion Irradiation of Core,Shell Colloidal Particles,ADVANCED MATERIALS, Issue 3 2004S. Roorda Colloidal particles with a 14,nm diameter Au core surrounded by a 72,nm thick silica shell have been irradiated with 30,MeV heavy ions. The shell deforms into an oblate ellipsoid, while the core becomes rod-shaped (aspect ratio up to 9) with the major axis along the beam. Optical extinction measurements show evidence for split plasmon bands, characteristic for anisotropic metal nanoparticles. [source] The dynamic behavior of magnetic colloids in suspensionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Tina Autenrieth The dynamic behavior of magnetic colloidal particles in suspension is investigated. The particles of the core,shell colloid consist of a cobalt ferrite core embedded in a silica shell and are stabilized by surface charges. As the suspension is strongly opaque to visible light, it can not be probed by dynamic light scattering techniques as a result of strong multiple scattering as well as absorption effects. Therefore, the static and dynamic behavior is probed with small-angle X-ray scattering and X-ray photon correlation spectroscopy (XPCS), respectively. Using XPCS, we are able to study the diffusion coefficient of an opaque colloidal system as a function of the scattering vector. In this paper, we report on the behavior of the colloidal system in the absence of an external magnetic field, meaning that the magnetic moments of the particles are oriented randomly. We find no evidence for magnetic interactions in the static data, while the dynamic XPCS data deviate very significantly from the predictions of model calculations. [source] A direct preparation of silica shell on polystyrene microspheres prepared by dispersion polymerization with polyvinylpyrrolidoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2008Jinho Hong PS/silica core/shell structured microspheres were easily prepared in a simple process. Because of the acid-base interaction between the TEOS and seed particles prepared by dispersion polymerization, uniform silica shell was formed on the PVP-stabilized PS particles without additional PVP-coating process. [source] Sonochemical Synthesis of Networked Silica Shell with Reduced Microporosity on Titania Nanocores for Photocatalytic Activity ReductionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Ahmed Mohamed El-Toni Silica shells with a high density of networks and reduced microporosity has been formed on titania nanocores via a sonochemical approach in the absence of ammonia as a hydrolyzing catalyst. The TiO2 -silica core-shell nanoparticles were characterized by transmission electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy (FTIR), and microporosity measurements. The photocatalytic activity of coated titania was also reported. FTIR measurements showed that the silica shell was formed with a high density of networks through the formation of asymmetric Si,O,Si vibration and asymmetric Si,O,Si stretching vibration bonds. Moreover, the thickness and microporosity of the silica shell could be altered by controlling the sonochemical power and time parameters. [source] Multifunctional Magnetoplasmonic Nanoparticle Assemblies for Cancer Therapy and Diagnostics (Theranostics),MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2010Wei Chen Abstract In this work, we describe the preparation and biomedical functionalities of complex nanoparticle assemblies with magnetoplasmonic properties suitable for simultaneous cancer therapy and diagnostics (theranostics). Most commonly magnetoplasmonic nanostructures are made by careful adaptation of metal reduction protocols which is both tedious and restrictive. Here we apply the strategy of nanoscale assemblies to prepare such systems from individual building blocks. The prepared superstructures are based on magnetic Fe3O4 nanoparticles encapsulated in silica shell representing the magnetic module. The cores are surrounded in a corona-like fashion by gold nanoparticles representing the plasmonic module. As additional functionality they were also coated by poly(ethyleneglycol) chains as a cloaking agent to extend the blood circulation time. The preparation is exceptionally simple and allows one to vary the contribution of each function. Both modules can carry drugs and, in this study, they were loaded with the potential anticancer drug curcumin. A comprehensive set of microscopy, spectroscopy and biochemical methods were applied to characterize both imaging and therapeutic function of the nanoparticle assemblies against leukemia HL-60 cells. High contrast magnetic resonance images and high apoptosis rates demonstrate the success of assembly approach for the preparation of magnetoplasmonic nanoparticles. This technology allows one to easily "dial in" the functionalities in the clinical setting for personalized theranostic regiments. [source] Preparation of C60-functionalized magnetic silica microspheres for the enrichment of low-concentration peptides and proteins for MALDI-TOF MS analysisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2009Hemei Chen Abstract In this work, for the first time, a novel C60-functionalized magnetic silica microsphere (designated C60-f-MS) was synthesized by radical polymerization of C60 molecules on the surface of magnetic silica microspheres. The resulting C60-f-MS microsphere has magnetite core and thin C60 modified silica shell, which endow them with useful magnetic responsivity and surface affinity toward low-concentration peptides and proteins. As a result of their excellent magnetic property, the synthesized C60-f-MS microspheres can be easily separated from sample solution without ultracentrifuge. The C60-f-MS microspheres were successfully applied to the enrichment of low-concentration peptides in tryptic protein digest and human urine via a MALDI-TOF MS analysis. Moreover, they were demonstrated to have enrichment efficiency for low-concentration proteins. Due to the novel materials maintaining excellent magnetic properties and admirable adsorption, the process of enrichment and desalting is very fast (only 5,min), convenient and efficient. As it has been demonstrated in the study, newly developed fullerene-derivatized magnetic silica materials are superior to those already available in the market. The facile and low-cost synthesis as well as the convenient and efficient enrichment process of the novel C60-f-MS microspheres makes it a promising candidate for isolation of low-concentration peptides and proteins even in complex biological samples such as serum, plasma, and urine or cell lysate. [source] Photoluminescence Detection of Biomolecules by Antibody-Functionalized Diatom BiosilicaADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Debra K. Gale Abstract Diatoms are single-celled algae that make microscale silica shells called "frustules", which possess intricate nanoscale features imbedded within periodic two-dimensional pore arrays. In this study, antibody-functionalized diatom biosilica frustules serve as a microscale biosensor platform for selective and label-free photoluminescence (PL)-based detection of immunocomplex formation. The model antibody rabbit immunoglobulin G (IgG) is covalently attached to the frustule biosilica of the disk-shaped, 10-µm diatom Cyclotella sp. by silanol amination and crosslinking steps to a surface site density of 3948,±,499 IgG molecules µm,2. Functionalization of the diatom biosilica with the nucleophilic IgG antibody amplifies the intrinsic blue PL of diatom biosilica by a factor of six. Furthermore, immunocomplex formation with the complimentary antigen anti-rabbit IgG further increases the peak PL intensity by at least a factor of three, whereas a non-complimentary antigen (goat anti-human IgG) does not. The nucleophilic immunocomplex increases the PL intensity by donating electrons to non-radiative defect sites on the photoluminescent diatom biosilica, thereby decreasing non-radiative electron decay and increasing radiative emission. This unique enhancement in PL emission is correlated to the antigen (goat anti-rabbit IgG) concentration, where immunocomplex binding follows a Langmuir isotherm with binding constant of 2.8,±,0.7,×,10,7M. [source] Encapsulation and Ostwald Ripening of Au and Au,Cl Complex Nanostructures in Silica Shells,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2006W. Lou Abstract We report a general template strategy for rational fabrication of a new class of nanostructured materials consisting of multicore shell particles. Our approach is demonstrated by encapsulating Au or Pt nanoparticles in silica shells. Other superstructures of these hollow shells, like dimers, trimers, and tetramers can also be formed by nanoparticle-mediated self-assembly. We have also used the as-prepared multicore Au,silica hollow particles to perform the first studies of Ostwald ripening in confined microspace, in which chloride was found to be an efficient mediating ligand. After treatment with aqua regia, Au,Cl complex is formed inside the shell, and is found to be very active under in,situ transmission electron microscopy observations while confined in a microcell. This aspect of the work is expected to motivate further in,situ studies of confined crystal growth. [source] Diatomaceous Lessons in Nanotechnology and Advanced MaterialsADVANCED MATERIALS, Issue 29 2009Dusan Losic Abstract Silicon, in its various forms, finds widespread use in electronic, optical, and structural materials. Research on uses of silicon and silica has been intense for decades, raising the question of how much diversity is left for innovation with this element. Shape variation is particularly well examined. Here, we review the principles revealed by diatom frustules, the porous silica shells of diatoms, microscopic, unicellular algae. The frustules have nanometer-scale detail, and the almost 100,000 species with unique frustule morphologies suggest nuanced structural and optical functions well beyond the current ranges used in advanced materials. The unique frustule morphologies have arisen through tens of millions of years of evolutionary selection, and so are likely to reflect optimized design and function. Performing the structural and optical equivalent of data mining, and understanding and adopting these designs, affords a new paradigm in materials science, an alternative to combinatorial materials synthesis approaches in spurring the development of new material and more nuanced materials. [source] A novel and facile preparation method of hollow silica spheres containing small SiO2 coresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Xinjian Cheng Abstract This article presents a novel and facile preparation method of hollow silica spheres with loading small silica inside. In this approach, positively charged SiO2/polystyrene core-shell composite particles were synthesized first, when the silica shells from the sol-gel process of tetraethoxysilane were then coated on the surfaces of composite particles via electrostatic interaction, the polystyrene was dissolved subsequently even synchronously in the same medium to form hollow silica spheres with small silica cores. TEM, SEM, and FTIR measurements were used to characterize these composite spheres. Based on this study, some inorganic or organic compounds could be loaded into these hollow silica spheres. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3431,3439, 2007 [source] | |||||||||||||||||||||||||