共查询到20条相似文献,搜索用时 15 毫秒
1.
Tae-Hyun Kim 《Materials Research Bulletin》2008,43(5):1126-1134
Au-silica heterogeneous nanocomposite particles were prepared by novel preparation strategy involving alcohol-reduction method using 3-aminopropyltrimethoxysilane (APTMS) as a binder between silica surface and Au nanoparticles, and using PVP as a stabilizer for Au nanoparticles. The evolution of morphology of composite particles was investigated with increasing reaction time at different Au precursor concentrations of 100 ppm and 250 ppm using UV-vis spectrophotometer and TEM. It is shown that the size of immobilized Au particles on silica surface can be controlled with the variation of reaction rate via adjusting Au precursor concentration and reaction time, but the high concentration of Au precursor hinders the immobilization of well-defined Au nanoparticles due to the slow reduction rate of Au precursor. On the basis of experimental results, the role of APTMS and PVP on the formation of composite particles and the effect of Au precursor concentration on the morphological evolution of composite particles are briefly discussed. 相似文献
2.
Mesoporous TiO2/polypyrrole (PPy)-based nanocomposite for electrorheological fluid was synthesized through one-pot method. By exploiting the combination conductivity of PPy and high dielectric constant of TiO2, the ER fluid exhibited an enhanced effect. The shear stress was 3.3 times as high as that of mesoporous TiO2. Powder X-ray diffraction (XRD), TEM and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize the as-made samples. Using a modified rotational viscometer, the electrorheological effect was measured. Dielectric spectra were also given to explain the mechanism. 相似文献
3.
The fabrication and photocatalytic application of zinc ferrite nanocrystals were reported. Quasi-cube ZnFe2O4 nanocrystals with typical small sizes of 5-15 nm were successfully synthesized by a facile hydrothermal approach. ZnFe2O4/P25 nanocomposite was prepared by physically grinding the ZnFe2O4 nanocrystals with TiO2 (commercial Degussa P25) at ambient temperature, and it exhibited excellent photocatalytic activity for the mineralization of Rhodamine B. UV-vis measurement and photocatalytic test results showed that ZnFe2O4 nanocrystals exhibited effective band-gap coupling to P25 nanopowders by simply physical grinding without any surface modification or high-energy balling, which is usually adopted in conventional mixture process. This phenomenon can be attributed to the high surface activities of the as-obtained tiny ZnFe2O4 nanocrystals and commercial P25 nanoparticles. It may imply that the mixing process of composite materials would be simplified by further lowering the grain sizes of their component particles. 相似文献
4.
The flower-shaped barium vanadate has been obtained by the composite hydroxide mediated (CHM) method from V2O5 and BaCl2 at 200 °C for 13 h. XRD and XPS spectrum of the as-synthesized sample indicate it is hexagonal Ba3V2O8 with small amount of Ba3VO4.8 coexistence. Scan electron microscope and transmission electron microscope display that the flower-shaped crystals are composed of nanosheets with thickness of ∼20 nm. The UV-visible spectrum shows that the barium vanadate sample has two optical gaps (3.85 eV and 3.12 eV). Photoluminescence spectrum of the barium vanadate flowers exhibits a visible light emission centered at 492 and 525 nm which might be attributed to VO4 tetrahedron with Td symmetry in Ba3V2O8. The ferromagnetic behavior of the barium vanadate nanoflowers has been found with saturation magnetization of about 83.50 × 10−3 emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 × 10−3 emu/g, which is mainly due to the presence of a non-orthovanadate phase with spin S = 1/2. 相似文献
5.
José R. Correa Eduardo Bordallo Vivian León Carlos Negro Regino Sáez-Puche 《Materials Research Bulletin》2010,45(8):946-634
Superparamagnetic magnetite nanoparticles were obtained starting from a mixture of iron(II) and iron(III) solutions in a preset total iron concentration from 0.04 to 0.8 mol l−1 with ammonia at 25 and 70 °C. The regeneration of cellulose from viscose produces micrometrical spherical cellulose beads in which synthetic magnetite were embedded. The characterization of cellulose-magnetite beads by X-ray diffraction, Scanning and Transmission Electron Microscopy and magnetic measurement is reported. X-ray diffraction patterns indicate that the higher is the total iron concentration and temperature the higher is the crystal size of the magnetite obtained. Transmission Electron Microscopy studies of cellulose-magnetite beads revealed the distribution of magnetite nanoparticles inside pores of hundred nanometers. Magnetite as well as the cellulose-magnetite composites exhibit superparamagnetic characteristics. Field cooling and zero field cooling magnetic susceptibility measurements confirm the superparamagnetic behaviour and the blocking temperature for the magnetite with a mean size of 12.5 nm, which is 200 K. 相似文献
6.
Jianfeng Shen Min Shi Hongwei Ma Bo Yan Na Li Mingxin Ye 《Materials Research Bulletin》2011,46(11):2077-2083
We demonstrated an environmental friendly and efficient route for preparation of magnetic reduced graphene oxide composite (MN-CCG). Glucose was used as the reducing agent in this one-step hydrothermal method. The reducing process was accompanied by generation of magnetic nanoparticles. The structure and composition of the nanocomposite was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, thermal gravimetric analysis, atomic force microscopy and transmission electron microscopy. It was found that the prepared MN-CCG is highly water suspendable and sensitive to magnetic field. 相似文献
7.
《Materials Research Bulletin》2013,48(11):4896-4900
The europium(III)-doped yttrium oxysulfate (Y2O2SO4:Eu3+) nanopieces have been prepared via electrospinning followed by calcination at 1000 °C in mixed gas of sulfur dioxide and air. Based on the experimental results, a possible formation mechanism for the nanopieces is that the nanopieces are determined by the directing template of electrospun nanoribbons and the multilayer crystal structure of Y2O2SO4. Besides, the nanopieces show excellent luminescent properties with emissions at 581, 589, 597, 653, 619, and 697 nm resulting from the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transition of Eu3+. The peaks of charge transfer and 5D0 → 7F2 transition of Eu3+ obviously have red shifts comparing to those of both Y2O3:Eu3+ nanoribbons and commercial Y2O3:Eu3+. Moreover, the nanopieces exhibit stronger intensities than the Y2O3:Eu3+ in excitation and emission spectra. Concentration quenching in the nanopieces occurs when Eu3+ concentration is 11 mol%, indicating that the nanopieces have an optimum luminescent intensity under this doping concentration. 相似文献
8.
Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO4·7H2O and NaBH4. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process. 相似文献
9.
A novel synthetic process has been developed to fabricate the magnetic alloy/spinel ferrite composite nanofibers. By employing the electrospinning technique and subsequent partial reduction, Fe-Ni alloy/nickel ferrite composite nanofibers with an average diameter of around 170 nm were successfully prepared. The synthesized composite nanofibers consist of the face centered cubic and body centered cubic phases of Fe-Ni alloy and the spinel phase of nickel ferrite, and have novel magnetic properties with much enhanced coercivity and saturation magnetization as compared with the pristine nickel ferrite nanofibers. 相似文献
10.
《Materials Research Bulletin》2013,48(11):4601-4605
Bi@Bi2O3@carboxylate-rich carbon core-shell nanosturctures (Bi@Bi2O3@CRCSs) have been synthesized via a one-step method. The core–shell nanosturctures of the as-prepared samples were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Raman spectroscopy. The formation of Bi@Bi2O3@CRCSs core–shell nanosturctures should attribute to the synergetic roles of different functional groups of sodium gluconate. Bi@Bi2O3@CRCSs exhibits significant enhanced photocatalytic activity under visible light irradiation (λ > 420 nm) and shows an O2-dependent feature. According to trapping experiments of radicals and holes, hydroxyl radicals were not the main active oxidative species in the photocatalytic degradation of MB, but O2− are the main active oxidative species. 相似文献
11.
《Materials Research Bulletin》2013,48(11):4693-4698
A facile one-pot method has been developed to prepare poly(amino acid) functionalized, water-stable, biocompatible, and superparamagnetic iron oxide nanoparticles (NPs) with small diameters of ∼10 nm. The obtained biocompatible magnetic nanoparticles capped with polyaspartic acid (PASP) exhibit a relatively high saturation magnetization (57.1 emu/g) and a much strong magnetic resonance (MR) T2 relaxation effect with the transverse relaxivity coefficient (r2) as high as 302.6 s−1 mM−1. Interestingly, the as-prepared Fe3O4@PASP NPs are highly stable in aqueous solution and demonstrate the property of magnetic nanofluids. The high T2 effect, good water-stability, superparamagnetization, biocompatibility and bioconjugatability render the as-synthesized Fe3O4@PASP NPs great desirable for bioapplications such as magnetic resonance imaging (MRI), bioseparation, targeted drug delivery, and so on. 相似文献
12.
In this paper, we report on the synthesis of size-dependent blue luminescent CdS nanocrystals by using a new nonhydrolytic single-source molecular method. The size of the synthesized CdS nanocrystals could be easily controlled by adjusting the ratio of reaction sources under inert atmosphere. The studies on the optical properties reveal an obvious size-dependent photoluminescence characteristic of the synthesized nanocrystals. 相似文献
13.
Salophen Al complex functionalized graphene (SCFG) nanocomposite was synthesized by simple coordination of phenol functionalized graphene (PFG) and as-prepared salophen Al complex. This process is facile, convenient and high efficient. We also investigated the structure, optical properties and electrochemical properties of the obtained SCFG composites. The results showed that salophen Al conjugated and incorporated onto the graphene sheet surface and the composites maintained the micro-structure of graphene sheets without agglomeration. The photoluminescence of salophen Al was completely quenched by graphene, due to the charge transfer between the salophen Al and the graphene nanosheets. Moreover, a significant electrochemical signal emerged on the SCFG modified electrodes compared with those of the graphene sheets or salophen Al complex. Owing to preliminary results of the excellent electrochemical property, SCFG nanocomposite is a promising electrochemical redox probe material. 相似文献
14.
A novel method is reported here for the synthesis of optically clear and stable colloidal solutions of silver nanoparticles. According to size they show different colours depending upon their plasmonic absorption frequencies. The materials have been synthesized at room temperature by chemical reduction of silver ions (silver nitrate) coordinated with dendrigraft polymer, polyethyleneimine (PEI) using formaldehyde in aqueous medium. UV-vis absorption and transmission electron microscopy (TEM) studies show single-band absorption with peak maximum at 354 nm for ∼3 nm sized particles, whereas a side band at ∼400 nm was observed when the particle size increased to ∼20 nm. Highly narrow particle size distribution was observed in case of samples having ∼3 nm size silver particles and also the process of reduction could be completed within minutes. More interestingly, the 3-nm sized particles showed strong blue (474 nm) fluorescence under UV excitation. Thin films of all synthesized samples were prepared on silica substrate by fine spray coating technique. 相似文献
15.
Core-shell Ni-Fe@ferrite nanoparticles with an average diameter of 14 nm and shell thickness of 3 nm were synthesized through a redox-transmetalation process. The alloy core and spinel oxide shell were verified by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. The hydrophobic oleylamine molecules on the surface were replaced by hydrophilic meso-2,3-Dimercaptosuccinic acid to make the nanoparticles to be water-soluble. X-ray diffraction study of the as-prepared core-shell nanoparticles indicates that they remained face centered cubic alloy core and spinel shell form in air. Magnetic measurements indicate that the core-shell nanoparticles exhibit superparamagnetic and exchange bias characteristics at 300 K and 5 K, respectively. 相似文献
16.
Jiazheng Wang 《Materials Research Bulletin》2011,46(12):2378-2384
A layer-by-layer approach has been developed to synthesize ZnO/SnO2 composite nanowire arrays on copper substrate. ZnO nanowire arrays have been first prepared on copper substrate through seed-assisted method, and then, the surface of ZnO nanowires have been modified by the polyelectrolyte. After oxidation-reduction reaction, SnO2 layer has been deposited onto the surface of ZnO nanowires. The as-synthesized ZnO/SnO2 composite nanowire arrays have been applied as anode for lithium-ion batteries, which show high reversible capacity and good cycling stability compared to pure ZnO nanowire arrays and SnO2 nanoparticles. It is believed that the improved performance may be attributed to the high capacity of SnO2 and the good cycling stability of the array structure on current collector. 相似文献
17.
Nickel ferrite (NiFe2O4) nanoparticles are prepared by a polyvinyl alcohol (PVA) assisted sol-gel auto-combustion method. The structure, composition, morphology and magnetic properties of the gel precursor are characterized by powder XRD, FT-IR, TGA, HR-SEM, TEM, HR-TEM and VSM. XRD confirms the formation of single-phase nickel ferrite with space group of Fd3m and inverse spinel structure. The vibration properties of nanoparticles are analysed by FT-IR spectrum. The thermal decomposition of the gel precursors is investigated by TGA. HR-SEM and TEM images show that the particles have spherical shape with particle size in the range of ∼30 nm and consistent with XRD result. The magnetic properties of these nanoparticles are studied for confirming the ferromagnetic behaviour at room temperature. 相似文献
18.
Synthesis and characterization of Co-Sn substituted barium ferrite particles by a reverse microemulsion technique 总被引:1,自引:0,他引:1
A series of Co-Sn substituted barium ferrite particles have been successfully synthesized by a reverse microemulsion technique. The effects of heteroatom contents and precipitating agents were investigated, respectively. It was found that the presence of heteroatoms could enhance lattice parameters, affect morphology evolution and modulate magnetic properties. Particularly, an unusual saturation magnetization (>70.0 emu/g) could be achieved under low heteroatoms concentration due to preferential occupation in specific sites. Precipitating agents played a critical role in forming barium ferrite phase, only sufficient precipitating agents could produce high-purity phase. Besides, this method is not limited in the synthesis of Co-Sn substituted barium ferrite, it can be extended to other heteroatoms, such as Ni-Zr and La, and resultant products also show well crystalline phase and unique magnetic properties. 相似文献
19.
A novel type of Ni-Cr nanocomposite that had a nanocrystalline Ni matrix dispersing Cr nanoparticles was developed by electrodeposition. During plasma nitriding at 560 °C for 10 h, the nanocomposite formed a surface hard coating in which the Cr nanoparticles were internally converted into CrN. The coating decreased in thickness but increased in hardness with the increase in the Cr content from 10.8 to 30 (by wt.%). Moreover, the Cr content increase caused a shift of the hardest area of the nitrided coating from the innermost to the topmost surface, as a result of the change in the nitridation mechanism of the composite from the internal to external. 相似文献
20.
Zhaoyuan He Yong Su Yiqing Chen Dong Cai Jing Jiang Lin Chen 《Materials Research Bulletin》2005,40(8):1308-1313
Mass production of uniform wurtzite ZnS nanostructures has been achieved by a H2-assisted thermal evaporation technique. X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) observations show that the ZnS nanostructures consist of nanobelts, nanosheets with a hexagonal wurtzite structure. The as-synthesized nanobelts have a length of several tens of micrometers and a width of several hundreds of nanometers. Self-catalytic vapor-liquid-solid (VLS) growth and vapor-solid (VS) growth are proposed for the formation of the ZnS nanostructures because neither a metal catalyst nor a template was introduced in the synthesis process. Room-temperature photoluminescence measurement indicates that the synthesized ZnS nanostructures have a strong emission band at a wavelength of 443 nm, which may be attributed to the presence of various surface states. 相似文献