共查询到20条相似文献,搜索用时 31 毫秒
1.
A. V. Nomoev 《Technical Physics Letters》2012,38(5):466-469
Hollow nanoparticles of silicon dioxide (SiO2) have been obtained using Cu/SiO2 core-shell nanoparticles as precursors. An original technique based on heating the precursor nanoparticles to T = 400°C followed by a nanochemical reaction of copper oxide separation from hollow silica particles has been proposed and implemented for the first time. The obtained hollow SiO2 nanoparticles have been studied by transmission electron microscopy. Mechanisms involved in the formation of hollow silica nanoparticles are discussed. 相似文献
2.
A new kind of superparamagnetic luminescent nanocomposite particles has been synthesized using a modified Stöber method combined with an electrostatic assembly process. Fe3O4 superparamagnetic nanoparticles were coated with uniform silica shell, and then 3-aminopropyltrimethoxysilane was used to terminate the silica surface with amino groups. Finally, negatively charged CdSe quantum dots (QDs) were assembled onto the surface of the amino-terminated SiO2/Fe3O4 nanoparticles through electrostatic interactions. X-ray diffraction (XRD), transmission electron microscopy (TEM), microelectrophoresis, UV-vis absorption and emission spectroscopy and magnetometry were applied to characterize the nanocomposite particles. Dense CdSe QDs were immobilized on the silica surface. The thickness of silica shell was about 35 nm and the particle size of the final products was about 100 nm. The particles exhibited favorable superparamagnetic and photoluminescent properties. 相似文献
3.
Hossein Rezvani Nikabadi Nasser Shahtahmasebi Mahmood Rezaee Rokn-Abadi Masoud Karimipour M M Bagheri Mohagheghi 《Bulletin of Materials Science》2014,37(3):527-532
In this paper, SiO2–Au–Cu2O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu2O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method Then, they were clung to the surface of Au seeds. The morphology of the resultant particles was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Transmission electron microscopy images demonstrate growth of monodispersed gold seeds and Cu2O nanoparticles in narrow size up to 10 nm and 5 nm, respectively. The presence of gold and Cu2O coating was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Absorption spectroscopy shows considerably 40 nm blue shift in absorption edge for SiO2–Au–Cu2O nanostructure rather than SiO2–Au core/shell nanoparticles. 相似文献
4.
Organic dye namely Coumarin 7 has been entrapped in silica particles using a single silica precursor viz. tetraethylorthosilicate. Both bare Coumarin 7 dye and dye incorporated core-shell particles were studied. Investigations of these core-shell composites were carried out using different characterization techniques such as energy dispersive X-ray analysis, X-ray photoelectron spectroscopy and transmission electron microscopy. It has been shown that the photostability of dye molecules is improved along with an increase in photoluminescence. 相似文献
5.
Vaidya S Thaplyal P Ramanujachary KV Lofland SE Ganguli AK 《Journal of nanoscience and nanotechnology》2011,11(4):3405-3413
Synthesis of uniform silica shell over Co3O4 nanoparticles was carried out using the colloidal solutions of Tergitol and cyclohexane. The shell could be controlled to a thickness of up to 20 nm by varying different parameters such as the amount of tetraethylorthosilicate, concentration of Co3O4 nanoparticles, reaction time and the presence of water and 1-octanol. Control of the amount of water (required for hydrolysis) appears to be the key factor for controlling the shell thickness. The methodology used is suitable to form shell over nanoparticles (present in powder form; synthesized at high temperature) which have high degree of agglomeration. Hollow shells of silica were obtained by the dissolution of the oxide core of Co3O4@SiO2 core-shell nanostructures. The composition of these core-shell nanostructures was confirmed by high-resolution transmission electron microscopy and elemental mapping by energy dispersive X-ray analysis. The hollow shells were characterized by using TEM, EDX and IR. Electron paramagnetic resonance studies of the core-shell nanostructures indicate the presence of free radicals on silica shell due to the presence of dangling bonds in the silica. Increase in the magnetic susceptibility was observed for these core-shell nanostructures. 相似文献
6.
Yumei Tian 《Materials Letters》2007,61(2):506-510
Spherical SiO2 particles have been successfully coated with zinc borate layers through a self-assembly process. The resulted SiO2-Zn5B4O11 core-shell nanospheres were characterized by X-ray diffraction (XRD), infrared spectra (IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The obtained SiO2-Zn5B4O11 core-shell nanospheres have perfect spherical shape with narrow size distribution (average diameters 50 nm), i.e., the cores with mean diameters of 40 nm and the shells with an average thickness of 5 nm, monodisperse and smooth surface. Moreover, the friction coefficient of the base oil was decreased by the addition of SiO2-Zn5B4O11 core-shell nanospheres. 相似文献
7.
We report on the synthesis, morphology and magnetic properties of a novel NiO/SiO2 nanostructure. The NiO/SiO2 nanostructure was synthesized by a method based on the contribution of sol-gel and combustion processes. X-ray powder diffraction (XRPD) showed the formation of the nanocrystalline NiO phase. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) revealed perfectly spherical NiO nanoparticles with diameter of about 5 nm. Amorphous silica shell around the NiO nanoparticles was also observed by HRTEM showing NiO/SiO2 core-shell nanostructure. Magnetic measurements show hysteretic behavior at 2 K with coercivity HC = 700 Oe, remanent magnetization Mr = 3.9 emu/g, saturation magnetization MS = 28.2 emu/g and huge magnetic moment mp ≈ 1300 μB of the nanoparticles. 相似文献
8.
《材料与设计》2015
In the study, SiO2/Ag composite particles with silver coating onto the surface of silica have been successfully prepared via a novel and facile approach (Oxidation–Reduction Method). In this approach, the SiO2 particles were first modified with 3-ammoniatriethoxysilane (APTES) and glyoxalic acid (GA) through two-step reaction, the aldehyde group (CHO) were anchored onto the surfaces of silica spheres via electrostatic attraction, these [Ag(TEA)2]+ ions in the solution were then reduced by the CHO and coated onto the surface of silica to obtain SiO2/Ag composite particles. The effects of the reaction conditions on silver content and synthetic mechanism had also been discussed. The structure, morphology and optical properties of the SiO2/Ag composite particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis spectroscopy. The results showed the surface of SiO2 was surrounded by pure silver nanoparticles, and the silver nanoparticles had face-centered-cubic structure, the SiO2/Ag composite particles with core–shell morphology and special optical properties. And the small content SiO2/Ag composite particles applied in electrically conductive adhesives (ECAs) improved the electrical bulk resistivity and tensile shear strength. 相似文献
9.
Deping Wang Xiang Duan Jiying Zhang Aihua Yao Liyun Zhou Wenhai Huang 《Journal of Materials Science》2009,44(15):4020-4025
Hydroxyapatite (HA) with highly ordered three-dimensional pores, whose size is about 300 nm, was prepared by colloidal template
method. The effect of the surface modification of silica spheres on the order degree of porous structure was investigated
by field emission scanning electron microscopy (FESEM). Then, superparamagnetic Fe3O4 nanoparticles were fabricated via redox reaction, followed by coating with silica via a sol–gel process, in which a certain
amount of TEOS was used in order to control the thickness of the silica shell. X-ray diffraction (XRD), transmission electron
microscopy (TEM), and magnetometry were applied to characterize the properties. Finally, Fe3O4 magnetic nanoparticles coated with silica were adsorbed in the mesopores of HA with highly ordered three-dimensional pores
by capillarity. The influence of dispersing agent on the adsorption results has been studied. Magnetometry was applied to
characterize the magnetic properties of superparamagnetic HA. The quantities of adsorbed SiO2/Fe3O4 nanoparticles with core–shell have been compared by variation of saturation magnetization before and after adsorption. 相似文献
10.
Nano sized Pt particles were successfully immobilized onto SiO2 and polystyrene-encapsulated silica core shell (SiO2@PS). To make the immobilization of Pt onto both silica and polystyrene-encapsulated silica core shell, SiO2 was first functionalized with -NH2 using 3-amino propyl trimethoxysilane (APTMS) while for core shell, the negatively charged surface of polystyrene (PS) was changed with positive charge by cationic surfactant such as cetyltrimethylammonium chloride (CTACl) to make the formation of SiO2 shell on preformed PS sphere. Transmission electron micrograph (TEM) images shows that Pt nanoparticles immobilized onto SiO2 and SiO2@PS were to be 3-4 nm without agglomeraiton. The energy dispersive spectroscope (EDS) shows that Pt contents on both SiO2 and SiO2@PS were to be 21.45% and 20.28%, respectively. In case of Pt-SiO2@PS, it is believed that Pt should have been immobilized onto PS surface and pore within SiO2 shell as well as SiO2 surface. The MEA fabricated with Pt-SiO2@PS shows better cell performance than of Pt-SiO2. 相似文献
11.
Cubic-type hollow silica particles were prepared from Fe2O3-SiO2 core-shell composite particles by selectively leaching the iron oxide core materials using acidic solution. The cubic Fe2O3 core particles were obtained by the hydrolysis reaction of iron salts. The Fe2O3-SiO2 core-shell type particles were prepared by the deposition of a SiO2 layer onto the surface of Fe2O3 particles using a two-step coating process. The first step involved primary coating with sodium silicate solution followed by subsequent coating by controlled hydrolysis of tetraethoxysilicate (TEOS). The core Fe2O3 was removed by dissolution in an acidic solution which gave rise to the hollow type silica particles. Scanning electron microscopic observation clearly revealed that the morphology is closely related to those of core the Fe2O3 particles. The cross sectional view determined by transmission electron microscopy revealed a silica shell with a thickness of about 50 nm. The porous texture of the hollow type silica particles is further characterized by nitrogen adsorption-desorption isotherm measurements. 相似文献
12.
Sn doped Fe3O4/SiO2 core-shell structures with the magnetic and photocatalytic properties have been successfully synthesized using Fe3O4 microspheres as the precursor. The morphology, phase and structure of the bifunctional products were investigated by X-ray powder diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy. The effects of the amount and hydrolysis rate of tetraethyl orthosilicate on the preparation of the Fe3O4/SiO2 core-shell structures were investigated. Low concentration and slow hydrolysis rate of tetraethyl orthosilicate were useful to obtain the uniform silica coated Fe3O4. The magnetic measurements indicated that the Sn doped Fe3O4/SiO2 core-shell structures showed ferromagnetic property and the magnetic saturation value slightly decreased after coated the silica layer. The magnetic Sn doped Fe3O4/SiO2 core-shell structures exhibited good photocatalytic activity in the degradation of methyl orange and could be separated by applying an appropriate magnetic field. 相似文献
13.
Paola Fabbri Francesco Pilati Roya Aghababazadeh Ghasem Kavei 《Materials Letters》2010,64(20):2265-2268
In this work a new approach has been developed for the synthesis of SiO2@Y2O3 particles with core-shell structure. The method is based on the synthesis of a covalently bonded sacrificial polymer shell grown onto silica particles. It is suitable to promote and stabilize the adsorption of different ions, namely Yttrium from its nitrate solution. After calcination and consequent elimination of the sacrificial polymer shell, the SiO2@Y2O3 core-shell particles are obtained. Results reveal that the shell thickness of these core-shell particles is higher and more uniform than that of particles prepared without sacrificial polymer shell. 相似文献
14.
Sofia Dembski Sabine RuppMoritz Milde Carsten GellermannMarcel Dyrba Stefan SchweizerMiroslaw Batentschuk Andres OsvetAlbrecht Winnacker 《Optical Materials》2011,33(7):1106-1110
Monodisperse, luminescent core-shell structured inorganic nanoparticles were synthesized by sol-gel technology. They exhibit an amorphous SiO2 core and a crystalline luminescent shell. Zn2SiO4:Mn2+ and Ca10(PO4)6OH:Eu3+ shell materials are investigated. The influence of the doping concentration on optical and structural properties was studied. The resulting nanoparticles were characterized by X-ray diffraction analysis, transmission electron microscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. 相似文献
15.
Au-Pt core-shell nanoparticles were prepared on glass surface by a seed growth method. Gold nanoparticles were used as seeds and ascorbic acid-H2PtCl6 solutions as growth solutions to deposit Pt shell on the surface of gold nanoparticles. These core-shell nanoparticles and their growth process were examined by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and field-emission environmental scanning electron microscopy and the results indicated that the deposition speed was fast and nanoparticles with obvious core-shell structure could be obtained after 2 min. Moreover, this seed growth method for preparation of the core-shell nanoparticles is simple and convenient compared with other seed growth methods with NH4OH as a mild reductant. In addition, electrochemical experiments indicated that these Au-Pt core-shell nanoparticles had similar electrochemical properties to those of the bulk Pt electrode. 相似文献
16.
Monodisperse core–shell structured SiO2@SiO2:Eu3+ microspheres were synthesized in a seeded growth way. In that way, a thin shell of Eu3+-doped silica was grown on the prepared monodisperse silica colloids. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermal analysis (TGA-DSC) and photoluminescence (PL) spectroscopy. The results reveal that the SiO2 spheres have been successfully coated by SiO2:Eu3+ phosphors and the obtained SiO2@SiO2:Eu3+ particles have perfect spherical shape with narrow size distribution. Additionally, the monodisperse SiO2@SiO2:Eu3+ microspheres exhibit considerably strong photoluminescence (PL) of Eu3+ under the excitation of 393 nm compared with the SiO2:Eu3+ samples with polydispersed or irregular shapes and sizes obtained by base-catalyzed Stöber method. Furthermore, the PL intensity increases with the increasing of Eu3+ concentration in SiO2 microspheres shell, and concentration quenching occurs when Eu3+ concentration exceeds 5.0 mol%. 相似文献
17.
Y.C. Li 《Materials Letters》2009,63(20):1659-1661
Core-shell composite materials have been widely used in many fields. In this paper, the core (Ag)-shell (PSt) composite nanoparticles have been successfully fabricated in microemulsions at ambient pressure. Firstly, Ag nanoparticles with about 60-100 nm in diameters were synthesized by reducing silver nitrate by ascorbic acid, and then, styrene polymerized at the surface of Ag nanoparticles by K2S2O4 initiator in microemulsion solutions. The Ag/PSt core-shell composite nanoparticles were identified by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and infrared spectra (IR). Results show that Ag-core nanoparticles were coated with ultra thin PSt shell with thickness of about 3-6 nm. 相似文献
18.
Wuyou Fu Haibin Yang Hari-Bala Shikai Liu Minghui Li Guangtian Zou 《Materials Chemistry and Physics》2006,100(2-3):246-250
The silica nanolayer with different thickness was coated on the spherical cobalt nanoparticles (an average diameter of 67 nm) to form core–shell structure by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). This coating process was based on the use of silane coupling agent 3-mercaptopropyltrimethoxysilane (HS-(CH2)3Si(OCH3)3, MPTS) as a primer to render the cobalt surface vitreophilic, thus rendering cobalt surface compatible with silica. The control over the silica coating layer thickness can be achieved by varying the reaction time. The cobalt nanoparticles and the cobalt coated with silica shell were confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. Result of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicate that the thermal stability of cobalt/silica is better than that of pure cobalt nanoparticles. Magnetic properties of these powders have been evaluated. These cobalt/silica core–shell nanoparticles can be utilized as precursors for making property-tunable magnetic nanoparticles, thin films, and multilayered core–shell structure nanocomposites. 相似文献
19.
Linbo Han Ying Zhou Ting He Guosheng Song Fan Wu Feiran Jiang Junqing Hu 《Journal of Materials Science》2013,48(17):5718-5726
A simple synthetic method has been developed for synthesis of mesoporous silica nanoparticles with versatile morphologies by adopting CTAB and C12–OH as dual soft templates. In such a simple method, only by regulating the dose of C12–OH and temperature, we can well-realize the silica nanoparticle morphological transformation from sphere to shell-like, rugby-like, peanut-like, hollow, and complex yolk–shell structures. These as-fabricated silica nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET), and small-angle powder X-ray diffraction. The as-prepared mesoporous silica nanoparticles with versatile morphologies possessing varying BET surface areas, pore diameter, and pore distributions have some potential applications in separation, sensing, and heterogeneous catalysis. 相似文献
20.
In this paper, we prepared the ZnO nanoparticles by a simple hydrothermal method and fabricated the ZnO/SiO2 core/shell nanostructures through a sol-gel chemistry process successfully. The hollow SiO2 nanostructures were obtained by selective removal of the ZnO cores. The structure, morphology and composition of the products were determined by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicated that the ZnO nanoparticles were sphere-like shape with the average size of 60 nm and belonged to hexagonal wurtzite crystal structure. With the coating of SiO2, the vibration modes of Si-O-Si and Si-OH were found. Furthermore, the measurement results of optical properties showed that spectra of bare ZnO nanoparticles and ZnO/SiO2 core/shell nanocomposites exhibited similar emission features, including a blue emission peak and an orange emission band. 相似文献