共查询到20条相似文献,搜索用时 78 毫秒
1.
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
2.
Harinarayan Das Nipa Debnath Atsuki Toda Takahiko Kawaguchi Naonori Sakamoto Sheikh Manjura Hoque Kazuo Shinozaki Hisao Suzuki Naoki Wakiya 《Advanced Powder Technology》2018,29(2):283-288
We present the results of controlled synthesis of spherical shape magnesium ferrite (MgFe2O4) dense nanoparticles by using ultrasonic spray pyrolysis (USP) method without any post-annealing processes. A new strategy was proposed to improve nano-crystallinity and observed morphology by ethanol (EtOH) addition in the initial precursor solution of MgFe2O4. Influence of EtOH, not only decrease the synthesized secondary particle size but also enhancing crystallization into MgFe2O4 single phase cubic structure. We observe that average nanosphere size decrease from 220 to 189?nm but increases of crystallite size from 9.6 to 19.2?nm with increasing the amount of EtOH from 0 to 20?vol%. Also, surface morphology revealed that nanospheres with some irregular shape and rough surface appear in case of EtOH additives. The magnetic properties are studied and different parameters viz. saturation magnetization, remanence, and coercivity have been correlated with crystallite size. 相似文献
3.
Homogeneous SiO2-coated cobalt nanospheres with tunable silica shell thickness from 21.7 nm to 4.5 nm were synthesized by using modified Stöber method. These nanocomposites were used as source materials to prepare SiO2 semi-hollow and hollow nanospheres by partially and completely etching cobalt cores, respectively. A proposed formation mechanism of these Co/SiO2 nanospheres with a core/shell structure was presented in this paper, which is also important for the rational design and synthesis of other monodisperse core/shell nanoarchitectures with uniform size and shape. Furthermore, these Co/SiO2 nanospheres were also used as a substrate for the deposition of CdS nanocrystals to prepare magnetic luminescent Co/SiO2/CdS nanocomposites. 相似文献
4.
5.
Mingwei Zhu Guodong Qian Zhiyu Wang Minquan Wang 《Materials Chemistry and Physics》2006,100(2-3):333-336
A two-step silica deposition process, including prefunctionalization with poly(vinylpyrrolidone) and the following silica deposition, has been used to fabricate silica layer on the surface of nanoscaled silver shell. The influencing parameters of silica coating process were optimized to prevent the precoated silver nanoparticles from desquamating from silica spheres, finally to obtain mono-dispersed silica spheres with silver and silica multilayer films. The resulted silica layer was dense and uniform, its thickness was controllable in the range of 20–50 nm. Such coated silica layer can provide improved thermal stability of the SiO2-Ag core-shell structural spheres. 相似文献
6.
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
7.
Komail Boustani Saber Farjami Shayesteh Mojtaba Salouti Atefeh Jafari Alireza Ahadpour Shal 《IET nanobiotechnology / IET》2018,12(1):78
Due to the strong effect of nanoparticles'' size and surface properties on cellular uptake and bio‐distribution, the selection of coating material for magnetic core–shell nanoparticles (CSNPs) is very important. In this study, the effects of four different biocompatible coating materials on the physical properties of Fe3 O4 (magnetite) nanoparticles (NPs) for different biomedical applications are investigated and compared. In this regard, magnetite NPs are prepared by a simple co‐precipitation method. Then, CSNPs including Fe3 O4 as a core and carbon, dextran, ZnO (zincite) and SiO2 (silica) as different shells are synthesised using simple one‐ or two‐step methods. A comprehensive study is carried out on the prepared samples using X‐ray diffraction, vibrating sample magnetometry, transmission electron microscopy and Fourier transform infrared spectroscopy analyses. According to the authors'' findings, it is suggested that carbon‐ and dextran‐coated magnetite NPs with high M s have great potential in the application of magnetic resonance imaging contrast agents. Moreover, silica‐coated magnetite NPs with high coercivity are potentially suitable candidates for hyperthermia and ZnO‐coated Fe3 O4 is potentially suitable for photothermal therapy.Inspec keywords: iron compounds, carbon, silicon compounds, zinc compounds, nanomedicine, biomedical materials, nanofabrication, nanoparticles, magnetic particles, coatings, X‐ray diffraction, magnetometry, transmission electron microscopy, Fourier transform spectra, infrared spectra, biomedical MRI, hyperthermia, radiation therapyOther keywords: biomedical applications, magnetic core‐shell nanoparticles, CSNP, cellular uptake, biodistribution, coating material, biocompatible coating materials, co‐precipitation, dextran, zincite, silica, X‐ray diffraction, vibrating sample magnetometry, transmission electron microscopy, Fourier transform infrared spectroscopy, magnetic resonance imaging contrast agents, hyperthermia, photothermal therapy, SiO2 ‐Fe3 O4 , ZnO‐Fe3 O4 相似文献
8.
《Journal of Experimental Nanoscience》2013,8(6):580-595
This article describes coating of magnetite nanoparticles (NPs) with amorphous silica shells. Controlled co-precipitation technique under N2 gas was used to prevent undesirable critical oxidation of Fe2+. The synthesised Fe3O4 NPs were first coated with trisodium citrate to achieve solution stability and then covered by SiO2 layer using Stober method. For uncoated Fe3O4 NPs, the results showed an octahedral geometry with saturation magnetisation range of 82–96?emu/g and coercivity of 85–120?Oe for particles between 35 and 96?nm, respectively. The best value of specific surface area (41?m2/g) for Fe3O4 alone was obtained at 0.9?M NaOH at 750?rpm and it increased to about 81?m2/g for Fe3O4/SiO2 combination. The total thickness and the structure of core–shell was measured and studied by transmission electron microscopy. The average particles size was about 50?nm, indicating the presence of about 15?nm SiO2 layer. Finally, the stable magnetic fluid contained well-dispersed magnetite-silica nanocomposites which showed monodispersity and fast magnetic response. 相似文献
9.
N. Selvi S. Sankar K. Dinakaran 《Journal of Materials Science: Materials in Electronics》2013,24(12):4873-4880
In this study, hybrid core–shell magnetic nanostructure comprising Fe3O4 core with multiple shells of zinc oxide and silica having well defined morphologies are produced by a simple synthetic approach based on an effective chemical precipitation technique. Semi-solid and hydrophilic poly ethylene glycol was used as the stabilizing agent to control the particle size of the magnetic nanostructures. 1-Hexadecyltrimethyl ammonium chloride was employed as the surfactant to achieve the core–shell nanostructure. The formation of the core–shell nanostructures were confirmed by X-ray diffraction, Fourier transform infra-red spectroscopy and high resolution transmission electron microscopy respectively. We also observed the pronounced ferromagnetic features of ZnO coated Fe3O4 core–shell nanostructure that substantiates the magnetization reversal mechanism of the spinel magnetite. The coating of dense SiO2 on Fe3O4@ZnO was found to shift the magnetic behaviour from ferromagnetic to super-paramagnetic even at room temperature. The optical features of the material are observed by UV–Vis Spectrometer and Photoluminescence spectrometer. 相似文献
10.
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
11.
AbstractNanocrystalline SrAl2Si2O8 :Eu2+ phosphor layers were coated on nonaggregated, monodisperse and spherical SiO2 particles using a hydrothermal homogeneous precipitation. After annealing at 1100 °C, core-shell SiO2@SrAl2Si2O8 :Eu2+ particles were obtained. They were characterized with x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. XRD analysis confirmed the formation of SiO2 @SrAl2Si2O8 :Eu2+ particles; it indicated that the SrAl2Si2O8 :Eu2+ shells on SiO2 particles consisted of hexagonal crystallites. The core-shell phosphors obtained are well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the coated layer is approximately 20–40 nm. Under ultraviolet excitation (361 nm), the particles emit blue light at about 440 nm due to the Eu2+ ions in their shells. 相似文献
12.
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
13.
Yidong Li Liyuan Xiao Yingliang Liu Pengfei Ai Xiaobo Chen 《Science and Technology of Advanced Materials》2010,11(4)
Nanocrystalline SrAl2Si2O8 :Eu2+ phosphor layers were coated on nonaggregated, monodisperse and spherical SiO2 particles using a hydrothermal homogeneous precipitation. After annealing at 1100 °C, core-shell SiO2@SrAl2Si2O8 :Eu2+ particles were obtained. They were characterized with x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. XRD analysis confirmed the formation of SiO2 @SrAl2Si2O8 :Eu2+ particles; it indicated that the SrAl2Si2O8 :Eu2+ shells on SiO2 particles consisted of hexagonal crystallites. The core-shell phosphors obtained are well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the coated layer is approximately 20–40 nm. Under ultraviolet excitation (361 nm), the particles emit blue light at about 440 nm due to the Eu2+ ions in their shells. 相似文献
14.
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
15.
V. G. P. Ribeiro A. C. H. Barreto J. C. Denardin Giuseppe Mele L. Carbone S. E. Mazzetto E. M. B. Sousa P. B. A. Fechine 《Journal of Materials Science》2013,48(22):7875-7882
Magnetic nanoparticles functionalized with biomolecules have received special attention due to their various biomedical applications, such as drug delivery and magnetic hyperthermia treatment for cancer. In this study, we present the synthesis and characterization of new nanoparticles coated with anacardic acid derived from cashew nut shell liquid. The results showed that Fe3O4 nanoparticles coated with anacardic acid (AA-MAG) have superparamagnetic behavior and the magnetization is almost equal when compared with the pure Fe3O4. This coating provides stability by preventing the aggregation nanoparticles without losing its magnetization potential. The AA-MAG demonstrates excellent and fast magneto-temperature response which can be used as high-performance hyperthermia agents. 相似文献
16.
Jen-Bin Shi Jhe-Wei Guo Chien Wu Chih-Jung Chen Ya-Ting Lin 《Materials Letters》2007,61(30):5268-5270
Elliptical-type α-Fe2O3 nanoparticles with/without silica shell have been prepared. The core particles were coated with uniform continuous layers of silica of two different thicknesses by hydrolysis of TEOS. The obtained HCP structure elliptical α-Fe2O3 nanoparticles with ∼ 240 nm length and 100 nm width is polycrystalline in nature. The thicknesses of SiO2 shell coated on α-Fe2O3 are about 55 and 30 nm, respectively. The optical and magnetic properties of these nanoparticles have been investigated. 相似文献
17.
F. Femila Komahal H. Nagabhushana R.B. Basavaraj G.P. Darshan B. Daruka Prasad S.C. Sharma D. Kavyashree 《Advanced Powder Technology》2018,29(9):1991-2002
Core–shell SiO2@ZnAl2O4:Eu3+ (5?mol%) nanophosphor (NP) with coatings up to the level IV has been prepared by a facile solvothermal route, followed by heat treatment. Scanning electron microscopy studies of fabricated core–shell particles displays good spherical shape and non-agglomeration with a narrow size distribution. The thickness of the shell increased with increase in coating cycles. Photoluminescence (PL) studies exhibited strong red emission peaks at 612?nm corresponding to the 5Do?→?7F2 transition of the Eu3+ ions. PL intensity increased with calcination temperature and coating cycles. The color coordinates of the coated NP were turned towards intense pure red emission with color purity ~95%. Powder dusting method was used to visualize latent fingerprints (LFPs) by staining uncoated and coated NP on various porous and non-porous surfaces under UV light. It was clear that core–shell NP display high sensitivity, reproducibility, selectivity, reliability, and can obtain the complete three levels of fingerprint ridge details. Judd–Ofelt (J-O) intensity parameters and radiative properties, namely transition probabilities, radiative lifetimes, branching ratios, and quantum efficiency were evaluated. The aforementioned results established that the SiO2@ZnAl2O4:Eu3+ (5?mol%) NP can be used as an ideal candidate for multifunctional applications such as WLEDs, LFPs, anticounterfeiting etc. 相似文献
18.
《Materials Letters》2006,60(21-22):2723-2727
A core-shell structure TiO2/BaFe12O19 composite nanoparticles that can photodegrade organic pollutants in the dispersion system effectively and can be recycled easily by a magnetic field is reported in this paper. The obtained samples were characterized by energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The TiO2/BaFe12O19 magnetic photocatalyst is composed of two parts: (1) TiO2 shell used for photocatalysis and (2) BaFe12O19 core for separation by the magnetic field. The photocatalytic activity of the as-prepared magnetic photocatalyst increased with increasing the thickness of TiO2 coating layer. On the other hand, the saturation magnetizations of titania-coated BaFe12O19 nanoparticles decreased with increasing thickness of the titania coating, while the coercivity does not show any change after coating. 相似文献
19.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
20.
Robert J. Wydra Anastasia M. Kruse Younsoo Bae Kimberly W. Anderson J. Zach Hilt 《Materials science & engineering. C, Materials for biological applications》2013,33(8):4660-4666
In this study, core-shell nanoparticles were developed to achieve thermal therapy that can ablate cancer cells in a remotely controlled manner. The core-shell nanoparticles were prepared using atomic transfer radical polymerization (ATRP) to coat iron oxide (Fe3O4) nanoparticles with a poly(ethylene glycol) (PEG) based polymer shell. The iron oxide core allows for the remote heating of the particles in an alternating magnetic field (AMF). The coating of iron oxide with PEG was verified through Fourier transform infrared spectroscopy and thermal gravimetric analysis. A thermoablation (55 °C) study was performed on A549 lung carcinoma cells exposed to nanoparticles and over a 10 min AMF exposure. The successful thermoablation of A549 demonstrates the potential use of polymer coated particles for thermal therapy. 相似文献