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43.
Hanmin Yang Rong Guo Hanqing Wang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2001,180(3):243-251
ZnS nanoparticles could be synthesized, when two kinds of Triton X-100/n-C10H21OH/H2O lamellar liquid crystal were mixed, in which Zn(CH3COO)2 and Na2S were dissolved in the solvent layer, respectively. The size of ZnS nanoparticles was about 10 nm and limited by the thickness of the solvent layer of the lamellar liquid crystal. The lubrication properties of the mixed system of Triton X-100/n-C10H21OH/H2O lamellar liquid crystal and ZnS nanoparticles were determined. The results showed that the presence of ZnS nanoparticles could improve the anti-wear ability of the Triton X-100/n-C10H21OH/H2O lamellar liquid crystal and decrease its friction coefficient. 相似文献
44.
加氢是现代化工产业中的一类主干反应,广泛应用于精细化学品、药物、食品、染料、功能聚合物及香料等制造产业中.高效催化剂的引入使得加氢反应能够在相对温和的条件下还原各类不饱和化合物.金属催化剂在加氢反应中活性高,所需的反应温度较低,适用性广,但是容易和S,N,As和P等元素结合而"中毒"失去反应活性.金属氧化物催化剂和金属硫化物催化剂具有一定的抗毒性,但活性相对较差,通常需要采用高温高压的反应条件,对催化剂本身和反应器的要求较为苛刻.传统催化剂在反应中具有一定的局限性,所以亟需开发新一代高效的加氢催化剂,在保证高活性和高选择性催化效果的同时,降低对能源的消耗和对环境的负面影响.金属有机骨架(MOFs)作为一种新型的多孔材料在过去二十年中受到相当大的关注,并在催化、气体存储和分离、传感器、发光材料和药物输送等众多领域的应用中表现出卓越的性能.利用MOF材料良好的相容性,将MOF和其它功能材料结合形成新的复合材料可以在更大程度上扩大MOF材料的应用领域.与传统的催化剂相比,MOF基材料具有优异的物理化学特性和结构可调性,通过合理的设计能够满足不同的催化加氢过程:(1)MOF基催化剂具有多样且特异性的活性位点.除了组成MOF材料的金属离子/簇和功能有机配体之外,MOF材料可通过封装其他活性物质或者被活性物质包裹等方式引入其他类型的催化位点,进一步扩大MOF基催化剂在不同催化加氢中的适应性.此外,不同的活性位点之间的协同作用又能特异性地促进反应的进行,对提高反应的选择性起到重要的作用.(2)活性位点的尺寸大小和空间分布可以被有效控制.这能影响到催化剂在催化反应过程中的活性和选择性,并且通过MOF材料的限域效应,同时能增强活性位点的稳定性和耐久性.(3)高比表面积能提高MOF基催化剂的催化活性.这种结构特性不仅可以增加MOF基催化剂的活性位点,而且能够吸附反应物和还原剂达到扩大其局部浓度的效果.(4)反应分子的扩散可通过调节MOF基催化剂的结构实现控制.通过调整MOF材料的孔窗口和通道的尺寸,能够改变反应物在催化剂内部的扩散途径,影响底物和活性位点的接触,能进一步影响反应的活性和选择性.本文总结了近几年来MOF基材料在不同的催化加氢反应中的应用,其中包括烯烃、炔烃、芳硝基化合物、肉桂醛、糠醛和苯等化合物的加氢反应.首先介绍了MOF基材料中不同类型的活性位点,除了MOF材料自身的金属离子/簇和功能有机配体外,MOF基复合材料中的金属纳米颗粒?金属硫化物?金属氧化物?均相催化剂等活性位点可以通过封装或包裹的方式引入.在不同加氢反应中,着重介绍了MOF基催化剂中不同类型活性位点的加氢过程中的催化方式、催化剂本身的结构优化及催化剂与反应底物之间的相互作用,以及这些因素之间的协同作用对反应活性和选择性的影响.最后,讨论了MOF基材料在加氢反应中应用存在的问题以及未来发展展望. 相似文献
45.
Yoann Lalatonne Farah Benyettou Nicole Lièvre Marc Lecouvey Laurence Motte 《Journal of magnetism and magnetic materials》2009,321(10):1653-1657
Magnetic nanoparticles differing by their size have been synthesized to use them for multiparametric testing, based on their differing magnetic properties. The nanoparticle has two essential roles: to act as a probe owing to its specific magnetic properties and to carry on its surface precursor groups for the covalent coupling of biological recognition molecules, such as antibodies, nucleic acids. A totally unique, newly patented, method has been used to characterize magnetic signatures using the MIAplex technology. The MIAplex reader, developed by Magnisense, measures the non-linear response of the magnetic labels when they are exposed to a multi-frequency alternating magnetic field. This specific signature based on d2B(H)/dH2 was correlated to other more conventional magnetic detection methods (superconducting quantum interference devices (SQUID) and Mössbauer). 相似文献
46.
In this paper,microphase behavior of an ABC triblock copolymer,polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide),namely PS-b-P2VP-b-PEO,was systematically studied during spin-coating and solvent vapor annealing based on various parameters,including the types of the solvent,spin speed and thickness.The morphological features and the microdomain location of the different blocks were characterized by atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM).With increasing thickness,the order-order transition from nanopores array to the pattern of nanostripes was observed due to microdomain coarsening.These processes of pattern transformation were based on the selectivity of toluene for different blocks and on the contact time between solvent molecules and the three blocks.This work provides different templates for preparation of gold nanoparticle array on silicon wafer,which can be adopted as an active surface-enhanced Raman scattering (SERS) substrate for poly(3-hexylthiophene) (P3HT). 相似文献
47.
Gh.R. Amiri M.H. YousefiS. Manouchehri M.H. KeshavarzS. Fatahian 《Journal of magnetism and magnetic materials》2011,323(6):730-734
In this work, Mn0.7Zn0.3Fe2O4 and Ni0.7Zn0.3Fe2O4 nanoparticles with super-paramagnetic properties and size distribution from 10 to 52 nm were investigated. These particles were produced by a low-temperature solid-state reaction method without the ball-milling process. The size and morphology of the nanocrystallites were determined by X-ray diffraction, transmission electron microscopy and scanning tunneling microscopy methods. Magnetic measurements such as alternating gradient field magnetometers were used to justify the super-paramagnetic properties of these nanoparticles. Their microwave absorption in the range of 8-18 GHz was studied by a vector network analyzer. Responses of the device under tests were studied. Also, the percentage of the resin, the size and thickness of the mount were determined. The band width of 2.3 GHz was obtained with reflection-loss/written-loss of −16 dB around 10.4 GHz. 相似文献
48.
Dong Xi XiaoPing Luo QiangHua Lu KaiLun Yao ZuLi Liu Qin Ning 《Journal of nanoparticle research》2008,10(3):393-400
Gold-coated iron oxide nanoparticle Hepatitis B virus (HBV) DNA probes were prepared, and their application for HBV DNA measurement
was studied. Gold-coated iron oxide nanoparticles were prepared by the citrate reduction of tetra-chloroauric acid in the
presence of iron oxide nanoparticles which were added as seeds. With a fluorescence-based method, the maximal surface coverage
of hexaethiol 30-mer oligonucleotides and the maximal percentage of hybridization strands on gold-coated iron oxide nanoparticles
were (120 ± 8) oligonucleotides per nanoparticle, and (14 ± 2%), respectively, which were comparable with those of (132 ± 10)
and (22 ± 3%) in Au nanoparticle groups. Large network aggregates were formed when gold-coated iron oxide nanoparticle HBV
DNA gene probe was applied to detect HBV DNA molecules as evidenced by transmission electron microscopy and the high specificity
was verified by blot hybridization. Our results further suggested that detecting DNA with iron oxide nanoparticles and magnetic
separator was feasible and might be an alternative effective method. 相似文献
49.
Niti Nipun Sharma 《Journal of nanoparticle research》2008,10(2):333-340
Emissive power per unit area of a blackbody has been modeled as a function of frequency using quantum electrodynamics, semi-classical
and classical approaches in the available literature. Present work extends the classical lumped-parameter systems model of
Brownian motion of nanoparticle to abstract an emissive power per unit area model for nanoparticle radiating at temperature
greater than absolute zero. The analytical model developed in present work has been based on synergism of local deformation
leading to local motion of nanoparticle due to photon impacts. The work suggests the hypothesis of a free parameter f′ characterizing the damping coefficient of resistive forces to local motion of nanoparticle and the manipulation of which
is possible to realize desired emissivity from nanoparticles. The model is validated with the well established Planck’s radiation
law. 相似文献
50.
The characters of self-assembly core/shell nanoparticles of amphiphilic hyperbranched polyethers (HP-g-PEO) as drug carriers
were investigated. The HP-g-PEO consisting of hydrophobic HP-g-PEO core and hydrophilic poly(ethylene glycol) arms was prepared
by the cation ring-opening polymerization. A series of HP-g-PEO samples with different degree of branching (DB) were synthesized
under various reaction temperatures. Nanoparticles (NP) were obtained by self-assembly of HP-g-PEO in aqueous media. The structure
of resulting HP-g-PEO was characterized by IR, 13CNMR and GPC. Dynamic light scattering and transmission electron microscopy were applied to characterize the sizes and size
distributions of NP. The results demonstrated that the mean diameters of NP were less than 100 nm, which exhibited uniform
spherical formations and narrow size distributions. Using hydrophobic drug Probucol (PRO) as model drug, the particle sizes
of drug loaded NP were larger than relative blank NP. The drug loading efficiency (LE) and incorporation efficiency (IE) of
these NP were achieved to 35 and 89%, respectively. The in vitro release of PRO from the NP exhibited a sustained release
and the cumulative drugs released for more than 600 h. The most important factor to affect drug release was the value of DB
of HP-g-PEO. With the DB of HP-g-PEO increasing, the size and size distribution of NP decreased as well as the release rate.
However, the small DB was beneficial to the LE of NP. Nanoparticle size and size distribution, LE, IE, and drug release rate
were slightly affected by the initial solution concentration of polyethers. The co-incorporated hydrophilic drug had influence
slightly on the release of drug from drug loaded NP. The results of in vitro drug release suggested that the core/shell NP
performed good controlled release behaviors with potential practice as novelty drug delivery vehicles. 相似文献