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1.
The method of obtaining nanoclusters α-Fe2O3 in the pores of monodisperse spherical particles of mesoporous silica (mSiO2) by a single impregnation of the pores with a melt of crystalline hydrate of ferric nitrate and its subsequent thermal destruction has been proposed. Fe3O4 nanoclusters are synthesized from α-Fe2O3 in the pores by reducing in thermodynamically equilibrium conditions. Then particles containing Fe3O4 were annealed in oxygen for the conversion of Fe3O4 back to α-Fe2O3. In the result, the particles with the structure of the core-shell mSiO2/Fe3O4@mSiO2/α-Fe2O3 are obtained. The composition and structure of synthesized materials as well as the field dependence of the magnetic moment on the magnetic field strength have been investigated. 相似文献
2.
The silica nanoparticles (SiO 2 NPs), silver (Ag) NPs and gold (Au) NPs coated with SiO 2 NPs (core-shell) were prepared. The sizes and morphology of the particles were indicated. The three prepared NPs were used for photocatalytic degradation of methyl orange (MO) dye by xenon lamp. Rate of photocatalytic degradation reaction constant and lifetime were calculated for each catalyst. Moreover, the mechanism of the photocatalytic reaction was studied. 相似文献
3.
Surface modified cobalt ferrite (CoFe 2O 4) nanoparticles containing Ni–NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe 2O 4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe 2O 4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe 2O 4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO 2–CoFe 2O 4) was modified by amine (NH 2) groups in order to add further functional groups on the silica shell. Then, carboxyl (–COOH) functional groups were added to the SiO 2–CoFe 2O 4 magnetic nanoparticles through the NH 2 groups. After that Nα,Nα–Bis(carboxymethyl)-l-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO 2–CoFe 2O 4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3. 相似文献
4.
Mesoporous silica materials have already proved to be non-toxic and biocompatible, and also to have large pore volume and very high specific surface area suitable for loading of small molecules. Having this in mind and the fact that silicon dioxide (SiO 2) powders can be so designed to obtain particle structures organized at multi levels, SiO 2 was chosen as a potential carrier for metronidazole, an antibiotic drug. SiO 2 powder was synthesized in two stages: first silica sol was prepared by hydrothermal synthesis and second the sol was converted into powder by dry spraying with simultaneous incorporation of the antibiotic into its structure. Scanning and transmission electron microscopy study revealed very complex structure and sub-structure of SiO 2 particles. Cell viability tests were used for estimation of cytotoxicity of so synthesized SiO 2. The drug release data showed that the system can provide drug release for a long time. Also, the device behavior is fully predictable, according to our theoretical model of multilevel structure design, and gives many opportunities for model investigations of drug release and its kinetics. The pore sizes and their distribution were observed as a limiting factor of drug release kinetics. Therefore, as the pore sizes are given as a set of discrete values, the kinetics of drug release might also be given as a set of corresponding discrete values. 相似文献
5.
Core/shell nanoparticles consisting of a magnetic core of zinc-substituted manganese ferrite (Mn 0.4Zn 0.6Fe 2O 4) and a shell of silica (SiO 2) are prepared by a sol-gel method using tetraethyl orthosilicate (TEOS) as a precursor material for silica and salts of iron, manganese and zinc as the precursor of the ferrite. Three weight percentages of the shell materials of SiO 2 are used to prepare the coated nanoparticles. The X-ray diffractograms (XRD) of the coated and uncoated magnetic nanoparticles confirmed that the magnetic nanoparticles are in their mixed spinel phase in an amorphous matrix of silica. Particles sizes of the samples annealed at different temperatures are estimated from the width of the (3 1 1) line of the XRD pattern using the Debye-Sherrer equation. The information regarding the crystallographic structure together with the particles sizes extracted from the high-resolution transmission electron microscopy (HRTEM) of a few selected samples are in agreement with those obtained from the XRD. HRTEM observations revealed that particles are coated with silica. The calculated thickness is in agreement with that obtained from the HRTEM pictures. Hysteresis loops observed in the temperature range 300 down to 5 K and Mössbauer spectra at room temperature indicate superparamagnetic relaxation of the nanoparticles. 相似文献
6.
Magnetic core/shell (CS) nanocomposites (MNCs) are synthesized using a simple method, in which a magnesium ferrite nanoparticle (MgFe 2O 4) is a core, and an amorphous silicon dioxide (silica SiO 2) layer is a shell. The composition, morphology, and structure of synthesized particles are studied using X-ray diffraction, field emission electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), scattering electrophoretic photometer, thermogravimetric analysis (TGA), and Mössbauer spectroscopy. It is found that the MgFe 2O 4/SiO 2 MNC has the core/shell structure formed by the Fe?O–Si chemical bond. After coating with silica, the MgFe 2O 4/SiO 2 MNC saturation magnetization significantly decreases in comparison with MgFe 2O 4 particles without a SiO 2 shell. Spherical particles agglomerated from MgFe 2O 4 nanocrystallites ~9.6 and ~11.5 nm in size function as cores coated with SiO 2 shells ~30 and ~50 nm thick, respectively. The total size of obtained CS MNCs is ~200 and 300 nm, respectively. Synthesized CS MgFe 2O 4/SiO 2 MNCs are very promising for biomedical applications, due to the biological compatibility of silicon dioxide, its sizes, and the fact that the Curie temperature is in the region required for hyperthermal therapy, 320 K. 相似文献
7.
In this study we investigated the release of titanium dioxide (TiO 2), silver (Ag) and silica (SiO 2) engineered nanoparticles (ENPs) from three different paints by using standardized water immersion test for coatings. Fibre-cement panels were coated with paints containing ENPs and then exposed to UV light and abraded to simulate weathering. After the static water immersion test, we observed a very low release of Ti (4–8 μg/l), while the Ag measured in leachates was under detection limit (0.1 μg/l). A small release of Si was measured in leachates, with 73 mg/l of Si released from paints containing SiO 2 ENPs after 120 h of water immersion. The cumulative loss of Si was about 1.8 % with respect to initial amount of Si in paint. Microscopic results highlighted that SiO 2 ENPs are mainly released in form of agglomerates with other particles, and only very few single SiO 2 ENPs were found in leachates. The results confirmed that Si migration is related to immersion cycles (wetting and drying cycles) of tested paints. 相似文献
8.
A new type of multicoated silica/zirconia/silver (SiO 2/ZrO 2/Ag) core-shell composite microspheres is synthesized in this paper. In the process, ZrO 2-decorated silica (SiO 2/ZrO 2) core-shell composites were firstly fabricated by the modification of zirconia on silica microspheres through the hydrolysis of zirconium precursor. Subsequently, on SiO 2/ZrO 2 composite cores, silver nanoparticles were introduced via ultrasonic irradiation and acted as “Ag seeds” for the formation of integrate silver shell by further reduction of silver ions using formaldehyde as reducer. The resulting samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared, energy-dispersive X-ray, and UV-vis spectroscopy, indicating that zirconia and silver layers were successfully coated on the surfaces of silica microspheres. 相似文献
9.
In this paper, a facile co-precipitation process for preparing mono-dispersed core–shell structure nanoparticles is reported.
The 110 nm SiO 2 cores coated with an yttrium aluminum garnet (Y 3Al 5O 12) layer doped with Er 3+ were synthesized and the influence of the concentration ratio of [urea]/[metal ions] on the final product was investigated.
The structure and morphology of samples were characterized by the X-ray powder diffraction, Fourier transform IR spectroscopy
and transmission electron microscopy, respectively. The results indicate that a layer of well-crystallized garnet Y 3Al 5O 12:Er 3+ were successfully coated on the silica particles with the thickness of 20 nm. The near infrared and upconversion luminescent
spectra of the SiO 2@Y 3Al 5O 12:Er 3+ powders further confirm that a Y 3Al 5O 12:Er 3+ coating layer has formed on the surface of silica spherical particles. 相似文献
10.
In this paper, an Au/Ag bimetallic hollow nanostructure was obtained by using SiO 2 nanospheres as sacrificial templates. The nanostructure was fabricated via a three steps method. SiO 2@Au nanospheres were first synthesized by the layer-by-layer technique, and then they were coated with a layer of Ag particles, finally, the Au/Ag bimetallic hollow nanospheres were obtained by dissolution of the SiO 2 core by exposure in HF solution. Several characterizations, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV visible absorption spectroscopy were used to investigate the prepared nanostructures. The effectiveness of these Au/Ag bimetallic hollow nanospheres as substrates toward surface-enhanced Raman scattering (SERS) detection was evaluated by using rhodamine 6G (R6G) as a probe molecule. We show that such Au/Ag bimetallic hollow nanospheres structure films which consisting of larger interconnected aggregates are highly desirable as SERS substrates in terms of high Raman intensity enhancement. The Au/Ag bimetallic hollow nanostructured aggregate, interconnected nanostructured aggregate and nanoscale roughness are important factors responsible for this large SERS enhancement ability. 相似文献
11.
SiO 2@CdSe core-shell particles were fabricated by controllable deposition CdSe nanoparticles on silica colloidal spheres. Step-wise coating process was tracked by the TEM and XRD measurements. In addition, SiO 2@CdSe/polypyrrole(PPy) multi-composite particles were synthesized based on the as-prepared SiO 2@CdSe particles by cationic polymerization. The direct electrochemistry of myoglobin (Mb) could be performed by immobilizing Mb on the surface of SiO 2@CdSe particles. Immobilized with Mb, SiO 2@CdSe/PPy-Mb also displayed good bioelectrochemical activity. It confirmed the good biocompatible property of the materials with protein. CdSe hollow capsules were further obtained as the removal of the cores of SiO 2@CdSe spheres. Hollow and porous character of CdSe sub-meter size capsules made them becoming hopeful candidates as drug carriers. Doxorubicin, a typical an antineoplastic drug, was introduced into the capsules. A good sustained drug release behavior of the loading capsules was discovered via performing a release test in the PBS buffer (pH 7.4) solution at 310 k. Furthermore, SiO 2@CdSe/PPy could be converted to various smart hollow capsules via selectively removal of their relevant components. 相似文献
12.
Currently available methods to prepare conducting polymers‐coated colloidal substrates for biomedical applications need to be improved because they involve the use of toxic reagents and tend to result in aggregated products with diminished conductivity. The work herein describes for the first time a facile strategy for preparing highly water‐dispersible, highly conductive, and biocompatible polypyrrole‐coated silica core–shell (SiO 2@PPy) particles using only chondroitin sulfate (CS), a biologically derived polymer, as the stabilizer and dopant. The CS preadsorbed onto silica surface serves as a template to control the confined growth of the PPy shell and doping of in situ polymerized PPy shell. The thickness of the PPy shell can be tuned from 8 to 17 nm by varying the CS preadsorbed amount. Increasing the thickness of the adsorbed CS layer can control the deposition of thinner PPy shells on an SiO 2 core surface to provide highly water‐dispersible SiO 2@PPy particles. Moreover, CS‐doped SiO 2@PPy particles exhibit conductivities as high as 5.3 S cm ?1. The conductivity of the particles depends on the PPy mass loading and the doping level of the PPy shell. Furthermore, the SiO 2@PPy particles exhibit good biocompatibility and therefore have potential applications in biomedicine. 相似文献
13.
Submicron core-shell structure particles SiO 2@Y 3Al 5O 12:Er 3+, which silica spherical particles was coated with an yttrium aluminum garnet (Y 3Al 5O 12) layer doped with Er 3+, were prepared by the modified Pechini-Type sol-gel method for the first time. The structure and morphology of samples were
detected by the X-ray powder diffraction (XRD) measurement, field emission scanning electron microscopy (FESEM) and transmission
electron microscopy (TEM), respectively. The results indicate that well-crystallized garnet nanocrystallines were formed on
the surface of the silica particles. The luminescent spectra in near infrared and visible region of the core-shell structured
SiO 2@Y 3Al 5O 12:Er 3+ powders were also investigated and compared with those of the pure Y 3Al 5O 12:Er 3+ and the Er 3+ doped silicate glass. The results show that mono-dispersed SiO 2@Y 3Al 5O 12:Er 3+ core-shell spherical particles with the near infrared, red and green luminescent emissions under the excitation of 980 nm
laser diode have been successfully synthesized. 相似文献
14.
La 0.45Ce 0.45F 3:Tb (10 mol% Tb) nanoparticles was synthesized via sonochemical method and then coated with silica (SiO 2) shells through a microemulsion process, resulting in the formation of core/shell structured LaCeF 3:Tb/SiO 2 nanoparticles. The obtained core/shell LaCeF 3:Tb/SiO 2 nanoparticles are spherical and uniform in size (average size about 60 nm), strongly fluorescent, and long fluorescence lifetime
(1.87 ms). This kind of nanoparticles was water-soluble, which could be applied in biological labeling and other fields. 相似文献
15.
A new type of magnetic fluid was prepared by dispersing monodispersed iron–silica (Fe–SiO 2) composite particles in polyethylene glycol (PEG) 400. The composite particles Fe–SiO 2 were synthesized by hydrogen reduction from α-Fe 2O 3–SiO 2 spheres. Their microstructures were observed by a high-resolution transmission electron microscope (HRTEM) and the magnetism was characterized with a superconducting quantum interference device (SQUID) magnetometer. Both steady-state and dynamic rheological properties of the magnetic fluid under different magnetic fields were studied by using a rheometer. Experimental results show that this magnetic fluid has a relatively high magnetoviscous effect at low shear rates. The yield stress of this material shows an increasing trend with a magnetic flux density. Also, viscoealstic properties of such materials are different from conventional ones. 相似文献
16.
Nano-magnetic Fe 3O 4 particles coated with silica are synthesized. The study of structural and magnetic properties was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer (VSM) techniques. The VSM results show that these kinds of composite particles exhibit superparamagnetic behavior with zero coercivity and remanence. The magnetic spheroid alumina carriers containing these magnetic composite particles were prepared by an internal gelation process. The SiO 2 coatings prevent the reaction between Fe 3O 4 and Al 2O 3 during the sintering process and maintain the superparamagnetic behavior of the catalyst carriers. 相似文献
17.
Bactericidal activity of high concentration Ag nanoparticles immobilized on surface of an aqueous sol–gel silica thin film was investigated against Escherichia coli and Staphylococcus aureus bacteria. Size of the surface nanoparticles was estimated in the range of 35–80 nm by using atomic force microscopy. Due to accumulation of the silver nanoparticles at near the surface (at depth of 6 nm and about 40 times greater than the silver concentration in the sol), the synthesized Ag–SiO 2 thin film (with area of 10 mm 2) presented strong antibacterial activities against E. coli and S. aureus bacteria with relative rate of reduction of the viable bacteria of 1.05 and 0.73 h −1 for initial concentration of about 10 5 cfu/ml, respectively. In addition, the dominant mechanism of silver release in long times was determined based on water diffusion in surface pores of the silica film, unlike the usual diffusion of water on the surface of silver-based bulk materials. Therefore, the Ag nanoparticles embedded near the surface of the SiO 2 thin film can be utilized in various antibacterial applications with a strong and long life activity. 相似文献
18.
Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO 2 particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO 2) were obtained. The composites C(NR/nSiO 2) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO 2) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO 2 in NR were investigated. The results obtained were compared with the NR/SiO 2 composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent (Si69) in C(NR/nSiO 2), the vulcanizate had better mechanical properties, higher wet resistance, and lower rolling resistance than those without Si69. In the composites C(NR/nSiO 2) and their vulcanizates, the SiO 2 particles’ average grain diameter was 60 nm, and the good-dispersion of the in-situ generated SiO 2 in the rubber matrix were a significant contribution to the satisfactory properties of C(NR/nSiO 2) composites and their vulcanizates. 相似文献
19.
An investigation was reported on the interfacial rheology of nano-SiO 2 dispersions in the presence of cetyltrimethyl ammonium bromide (CTAB). The interfacial dilational viscoelasticity had been measured as a function of the nano-particle concentration. The properties of the interface were affected by different processes such as the surfactants adsorption at the liquid or at the particle interfaces. It was found that the influence of nano-SiO 2 particles on the interfacial properties was evident and complex. The property of SiO 2 particles would change from hydrophilic to hydrophobic when CTAB molecules absorbed at their surface. The reorganization of surfactants and the participation of hydrophobic SiO 2 at the surface were offered to explain the process. In particular, the interaction between surfactants and particles, and the transfer of particles from bulk to the surface played an important role in changing the properties of the interface. 相似文献
20.
Submicron spherical SiO 2 particles have been coated with AgEu(MoO 4) 2 phosphor layers by a sol-gel process, followed by surface reaction at high temperature, to get core/shell structured SiO 2@AgEu(MoO 4) 2 particles. X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the resulted core-shell phosphors. The luminescent properties of the core-shell structured phosphors have also been measured at room temperature, and their photoluminescence (PL) spectra are similar to the pure AgEu(MoO 4) 2 phosphor prepared by the same sol-gel method exhibiting red emission. 相似文献
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