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排序方式: 共有245条查询结果,搜索用时 15 毫秒
81.
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83.
Colloidal Au and poly(vinylpyrrolidone) (PVP) composite thin films are fabricated by spin-coating method. Linear optical absorption measurements of the Au/PVP composite films indicate an absorption peak around 530 nm due to the surface plasmon resonance of gold nanoparticles. Nonlinear optical properties are studied using standard Z-scan technique, and experimental results show large optical nonlinearities of the Au/PVP composite films. A large value of χ^(3)/α up to 0.56× 10-^10esu·cm is obtained, which is comparable to the best values reported in metal/oxlde composite films. 相似文献
84.
85.
《Composite Interfaces》2013,20(2):75-84
ZnS:Cd nanoparticles were synthesized in a reverse micelle system by controlling reaction factors with mercaptoacetic acid (MPA) as a surfactant and N,N-dimethylformamide as an oil phase. X-ray diffraction pattern shows that the ZnS:Cd nanoparticles exhibit a cubic structure and its mean size is calculated around 4 nm. With different molar ratios of Zn2+/S2?, the relative intensity of the emission peaks at 400 and 556 nm changes dramatically due to the more sulfur vacancies which resulted from the imbalance of Zn2+ and S2+ ions. Furthermore, hydrophobic phase-transferred ZnS:Cd nanoparticles were obtained using octylamine, and a highly luminescent phase-transferred ZnS:Cd/polyvinylpyrrolidone (PVP) nanocomposite was prepared by blending the phase-transferred ZnS:Cd with PVP. Infrared absorption suggests that octylamine has been successfully connected with the MPA-coated ZnS:Cd nanoparticles. Unlike the MPA-coated ZnS:Cd which has a very strong emission at 556 nm, the phase-transferred ZnS:Cd has a strong emission at 435 nm, which is ascribed to surface passivation and electron redistribution. In addition, luminescent intensity enhancement was observed for the phase-transferred ZnS:Cd/PVP nanocomposites with various Cd2+ doping concentrations. 相似文献
86.
《Journal of Polymer Science.Polymer Physics》2018,56(3):248-254
This paper outlines the shrinkage of electrospun polyvinylpyrrolidone (PVP) fiber mats during thermal treatment. The thermal behavior and phase changes within the fibers were investigated by DSC and TGA/DTA. Five precursors with different PVP loading in ethanol were electrospun. The mats shrinkage as function of temperature was measured in the RT–200 °C range. Shrinkage rate drastically increased above the polymer glass transition point, Tg (150–180 °C), due to increase in polymer chain mobility. Mats shrinkage at 200 °C as function of PVP concentration showed a minimum at ∼10%wt. Below 10% PVP the mats morphology is non‐uniform, consisting of beads and fibers. Above 10% PVP, only flat and uniform fibers were observed. This paper outlines the dominant mechanism governing the mats shrinkage during heating. In addition, the effect of PVP concentration on the expansion of fibers diameter was investigated and found to be consistent with the linear shrinkage observing a minimum at ∼10% PVP. The effect of applied voltage on mat shrinkage was investigated, and showed a minimum at 12 kV. Understanding the interplay between fibers morphology and thermal shrinkage allows precursor composition and system optimization needed for minimizing shrinkage negative effects on the structure and properties of electrospun fiber mats. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 248–254 相似文献
87.
Jinghong Ma Hongfang Ma Dahai Pan Ruifeng Li Kechang Xie 《Reaction Kinetics and Catalysis Letters》2005,86(2):225-232
Summary Ruthenium nanoparticles supported on zeolite Beta catalysts were prepared by alcohol reduction of RuCl3solution in the presence of PVP. Highly dispersed Ru nanoparticles with mono-size formed on the zeolite surface and their
size can be controlled by changing the amount of PVP at same ruthenium loading. In the water/benzene system, Ru-PVP/Beta catalyst
for benzene hydrogenation showed high activity, selectivity and good stability. 相似文献
88.
Graphene-reinforced polymer nanocomposites are under intense investigation in recent years. In this work, graphene nanosheets have been prepared using chemical reduction method of graphene oxide. Graphene-reinforced epoxy nanocomposites show an enhancement in mechanical and thermal properties at 0.05 wt.% of graphene in epoxy matrix. Modification of graphene with polyvinylpyrrolidone (PVP) shows the significant enhancement in mechanical and thermal properties of epoxy nanocomposites. PVP-modified graphene nanosheets reduces the gap of enthalpic and entropic penalties and facilitates improved dispersion of graphene in epoxy matrix. In addition, enhanced dispersion of PVP-modified graphene in epoxy matrix results in better load transfer across graphene–epoxy interface. Glass transition temperature (Tg) of PVP-modified graphene epoxy nanocomposites increases as compared to pure epoxy because there exist an interaction between epoxy and PVP. Fractography study reveals the localized ductile fracture. 相似文献
89.
Al13 polycations containing alumina sols, prepared by a modified Yoldas procedure were mixed with polyvinylpyrrolidone (PVP).
Although Al speciation in freshly prepared sols was not affected by PVP addition the decay rate of Al13 polycations was slightly decreased in PVP-containing sols. PVP does not show any influence on particle size and particle
growth. The influence of PVP addition on viscosity and flow behavior of modified Yoldas sols depends on their solids content
and molar ratio. 相似文献
90.
We report a low cost selective analytical method based on inner filter effect (IFE) for citrate-silver nanoparticle (cit-AgNP) detection, in which fluorescent amine-derivatized carbon dots (a-CDs) act as the donor and aggregated cit-AgNPs as the energy receptor. Carbon dots (CDs) were chemically modified with ethylenediamine (EDA) moieties via amidic linkage displaying an emission band at 440 nm. The presence of cit-AgNPs produces a remarkably quenching of a-CD fluorescence via IFE, since the free amine groups at CD surface induce the aggregation of cit-AgNPs accompany by a red-shifting of their characteristic plasmon absorption wavelength, which resulted in “turn-on” of the IFE-decreased in CD fluorescence. The proposed method, which involves the use of chelating agents for removal of metal ions interferences, exhibits a good linear correlation for detection of cit-AgNPs from 1.23 × 10−5 to 6.19 × 10−5 mol L−1, with limits of detection (LOD) and quantification (LOQ) of 5.17 × 10−6 and 1.72 × 10−5 mol L−1, respectively. This method demonstrates to be efficient and selective for the determination of cit-AgNPs in complex matrices such as cosmetic creams and reveals many advantages such as low cost, reusability, high sensitivity and non time-consuming compared with other traditional methods. 相似文献