共查询到20条相似文献,搜索用时 31 毫秒
1.
Keishiro Tomoda Natsumi Yabuki Hiroshi Terada Kimiko Makino 《Colloid and polymer science》2014,292(12):3195-3203
Indomethacin-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles with an average diameter of 100 nm were prepared by using a combination of an antisolvent diffusion method with preferential solvation (bare nanoparticles). Polyvinyl alcohol (PVA)-coated indomethacin-loaded PLGA nanoparticles with an average diameter of 100 nm were also prepared by emulsification and the solvent evaporation method (PVA-coated nanoparticles). Bare nanoparticles do not have a hydrophilic stabilizer on the surface; therefore, they have high hydrophobicity and negative charges. Electrophoretic mobility of bare nanoparticles at 5 mM NaCl solution was about 68 times higher than that of PVA-coated nanoparticles. Permeability of bare nanoparticles through rat skin was significantly higher than that of PVA-coated nanoparticles when iontophoresis was applied ex vivo. Indomethacin amount inside the skin after the permeation study by using bare nanoparticles was much higher than that by using PVA-coated nanoparticles. Indomethacin transition to circulation and accumulation in muscle by the transdermal delivery of indomethacin-loaded PLGA nanoparticles were significantly enhanced by using the combination of bare nanoparticles and iontophoresis in vivo. As for transdermal route of nanoparticles, both bare and PVA-coated nanoparticles were revealed to penetrate through the transfollicular pathway, and the migration of nanoparticles to follicles was enhanced by the application of iontophoresis. PLGA nanoparticles prepared by the antisolvent diffusion with preferential solvation are beneficial for iontophoretic transdermal delivery of therapeutic agents. 相似文献
2.
W. Simon A. J. Yencha M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,8(1):71-84
Using a beam apparatus, we have measured the HCl+ (A,v′→X,v″) fluorescence spectra of HCl+ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (23 S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s 3 P 2, 0) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl+ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (23 S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s 3 P 2, 0)+HCl, the HCl+ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl+ (A,v′) ions in collisions with HCl (rate constant around 5·10?9 cm3s?1). 相似文献
3.
Andreas Geissler Daniel Scheid Wei Li Markus Gallei Kai Zhang 《Cellulose (London, England)》2014,21(6):4181-4194
In comparison to stimuli-responsive, multi-functional nanoparticles (NPs) from synthetic polymers, such NPs based on sustainable, naturally occurring polysaccharides are still scarce. In the present study, stable stimuli-responsive, fluorescent and magnetic NPs were fabricated using cellulose stearoyl esters (CSEs) consisting of cellulose and stearoyl groups. The multifunctional NPs with the average diameters between 80 and 250 nm were obtained after facile nanoprecipitation using CSE solutions containing Fe3O4-NPs. Using the aqueous solution of fluorescent rhodamine B as precipitant, NPs with rhodamine B on NP surface were obtained. Rhodamine B could be released depending on the temperature. In comparison, stearoylaminoethyl rhodamine B can be encapsulated in CSE-NPs, which renders obtained NPs reversible fluorescence in response to UV illumination and heat treatment. 相似文献
4.
5.
Zhiyin Chao Linyong Song Yifeng Zhou Wangyan Nie Pengpeng Chen 《Colloid and polymer science》2014,292(11):2841-2848
To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO2) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO2/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO2 composite microspheres were used as templates to prepare PS/SiO2/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO2 templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO2 templates’ surface by chemical reduction. The morphology and structure of the PS/SiO2/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO2/Ag nanocomposite. Results indicated that the PS/SiO2/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates. 相似文献
6.
A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL?1 and a dynamic range as wide as from 0.001 to 100 ng mL?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.
The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. 相似文献
7.
Shu -Sing Chang 《Journal of Thermal Analysis and Calorimetry》1988,34(1):135-154
The heat of reaction and kinetics of curing of diglycidyl ether of bisphenol-A (DGEBA) type of epoxy resin with catalytic amounts of ethylmethylimidazole (EMI) have been studied by differential power-compensated calorimetry as a part of the program for the study of process monitoring for composite materials. The results were compared with those from 1∶1 and 1∶2 molar mixtures of DGEBA and EMI. A method of determination of heat of reaction from dynamic thermoanalytical instruments was given according to basic thermodynamic principles. The complicated mechanism, possibly involving initial ionic formation, has also been observed in other measurements, such as by time-domain dielectric spectroscopy. The behavior of commercially available DGEBA resin versus purified monomeric DGEBA were compared. The melting point of purified monomeric DGEBA crystals is 41.4 °C with a heat of fusion of 81 J/g. The melt of DGEBA is difficult to crystallize upon cooling. The glass transition of purified DGEBA monomer occurs around ?22 °C with aΔC p of 0.60 J/K/g. 相似文献
8.
Chen-xia Feng Ting Huang Hai-ming Chen Jing-hui Yang Nan Zhang Yong Wang Chao-liang Zhang Zuo-wan Zhou 《Colloid and polymer science》2014,292(12):3279-3290
Different contents of carbon nanotubes (CNTs) were introduced into a miscible poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend. The interfacial affinity between CNTs and components of the blend was evaluated by calculating the interfacial tension. The dispersion and microstructure of CNTs in the nanocomposites were investigated through scanning electron microscope and rheological measurement. The effect of CNTs on the crystallization of PVDF was comparatively investigated through nonisothermal and isothermal crystallization processes. The results showed that CNTs exhibited stronger interfacial affinity to PMMA. Homogeneous dispersion of CNTs in the nanocomposites was achieved. Largely enhanced crystallization temperature and increased crystallinity of PVDF were obtained by adding CNTs during the nonisothermal crystallization process. The results obtained from the isothermal crystallization process proved that CNTs induced the concentration fluctuation in the sample, which resulted in the formation of spherulites with different types, i.e., the banded spherulites and compact spherulites. Furthermore, both the crystallization temperature and the content of CNTs exhibited great influence on the crystalline morphology of PVDF. 相似文献
9.
High-density polyethylene (HDPE) containing various volume fractions (0–20 vol%) of aluminum nitride nanoparticles (n-AlN) is prepared by melt mixing. Structural and morphological characterizations of the prepared composites are carried out by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and atomic force microscopy (AFM). Thermal stability and degradation kinetics of HDPE/AlN (nano) composites are investigated by Thermogravimetric analysis (TG). HR-TEM micrographs confirm fairly uniform dispersion of AlN nanoparticles, as well as the existence of long interconnected chain-like aggregates. AFM images also confirm homogeneous dispersion of n-AlN in the polymer matrix. Roughness analysis from the AFM data indicates the presence of substantial undulation from the mean surface level. Thermogravimetric data indicate small improvement in the thermal stability of the composites. Kinetic parameters, viz., the activation energy (E a), frequency factor (A), and reaction order (n) are estimated using the isoconversional methods of Kissinger, Flynn–Wall–Ozawa (FWO), KAS, and Friedman. Activation energies (E a) calculated by the above four models display nearly similar features and are enhanced by the presence of AlN nanoparticles. Kinetics of degradation of HDPE-AlN (nano) composites follows a first-order reaction. 相似文献
10.
Yu. N. Sazanov E. P. Skvortsewich E. B. Milovskaya 《Journal of Thermal Analysis and Calorimetry》1974,6(1-2):53-58
TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer. 相似文献
11.
E. A. Walters J. R. Grover M. G. White 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1986,4(1):103-110
The dissociation energy of the C2H4 · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol?1 by a dissociative photoionization technique. C2H4 · HCl was produced by free expansion of a 1:4 mixture of C2H4 in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C2H4 · HCl)+ from C2H4 · HCl was determined between 600 and 1,300 Å and the onset for (C2H4 · HCl)+ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH f 0 (C2H4 · HCl) = ?10.7±0.7 kcal mol?1 and ΔH f 0 (C2H4·HCl+)=235.1±0.9 kcal mol?1. A complex ion dissociation energyD 0(C2H4 · HCl+) = ?0.3±0.9 kcal mol?1 was calculated from the results. The major features on the PIE curve for C2H4 · HCl+ can be analyzed in terms of the known energetic features of C2H 4 + and HCl. An extended energy diagram for the C2H4 + HCl system is presented. 相似文献
12.
A. J. Yencha J. Ganz M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,14(1):57-76
An electron spectrometric study has been performed on HCl using metastable helium and neon atoms as well as neon resonance photons. High resolution electron spectra were obtained with two different beam apparatuses for a mixed He(21 S, 23 S) beam, a pure He(23 S) beam, and, for the first time, state-selected pure Ne(3s 3 P 2) and pure Ne(3s 3 P 0) beams, and for NeI resonance photons. For the system He(23 S)+HCl the vibrational populationsP(υ′) of the formed HCl+ (X 2∏ i , υ′) and HCl+ (A 2Ω+, υ′) ions are found to differ from the Franck-Condon factors for unperturbed potentials, indicating slight bond stretching in HCl upon He(23 S) approach. For He(21 S)+HCl the vibrational peak shapes and vibrational populations are substantially different from the He(23 S) case, pointing to an additional, charge exchanged interaction (He++HCl?) in the entrance channel of the former system. For the first time, we have detected the electrons in both the He(21 S)+HCl and He(23 S)+HCl spectra associated with the major mechanism for the formation of Cl+ ions: energy transfer to repulsive HCl** Rydberg states, dissociating toH(1s) and autoionizing Cl**(1 D 2 nl) atoms. For both Ne(3 P 2)+HCl and Ne(3 P 0)+HCl, the populationsP(υ′) of both final molecular states HCl+ (X, A) agree closely with the Franck-Condon factors at the average relative collision energyē coll=55 meV and, for HCl+ (A 2Ω+), also atē coll=130 meV. 相似文献
13.
Effect of Cl substituent in the aromatic tetracycline ring on its reactivity with solvated electrons
J. O. Dzięgielewski P. Głowacki J. Gorący D. Orłowska-Dudek E. Słoma 《Journal of Radioanalytical and Nuclear Chemistry》1984,87(3):179-187
Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC?HCl/ in methanol solution saturated with Ar or N2O were determined. Rate constants of the reaction es with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$ On the basis of the diffence between decomposition yields: ΔG=G?TC.HCl?G?ClTC.HCl′ 7-C?Cl group decomposition yield and the rate constant $$k/e_s^ - + Cl - C - 7/ = 7 \cdot 94 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} $$ were determined. It was demonstrated by1H NMR that the radical formed by degradation of 7-C?Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride /TC.HCl/. 相似文献
14.
Stefan M. Daiser Holger Frenzel Johann L. Maul Christian Scholze 《Mikrochimica acta》1987,91(1-6):371-377
More than 13 years of SIMS application field experience of numerous users of the ATOMIKA Ionmicroprobes have been the basis for the new SIMS Data System SDS 800. The hardware and software concept of the SDS 800, therefore, pays special attention to the following requirements:
- Convenient set-up, modification and re-use of the measuring parameter sets for easy, time-saving operation.
- Individual parameter selection from the very broad range of SIMS measuring parameters for optimum SIMS data quality.
- Multitasking operation for simultaneous handling of SIMS measurement, data processing, data output and of auxiliary techniques.
- Simultaneous depth profile/ion image acquisition and processing to enhance data quality and to validate data interpretation.
- User-friendly data processing and output.
15.
Major processing factors in forming Fe2SiO4/SiO2 and Fe2O3/SiO2 powders via sol–gel synthesis followed by solid-state reactions are investigated. The results clearly indicate that the chemical compositions of the precursors, the ratio of the precursors, the nature of the catalyst used, and the gas atmosphere during solid-state reactions can all affect the outcome of the reaction product(s). The formation of Fe2SiO4/SiO2 is enhanced by using the precursor iron(III) acetylacetonate as the Fe source with the precursor ratio of iron(III) acetylacetonate to tetraethyl orthosilicate being 1:1 and the addition of formic acid. Otherwise, crystalline Fe and Fe3C are formed in place of Fe2SiO4. By altering the gas atmosphere during solid-state reactions from argon to oxygen, the reaction products change from Fe2SiO4/SiO2 to Fe2O3/SiO2. All of the observed phenomena can be rationalized via the degree of mixing of the Fe–O and Si–O domains at the molecular level in the gel network during sol–gel reactions and the presence of a reducing or oxidizing atmosphere during the solid-state reaction. 相似文献
16.
Binary polymer blends of hydrophobic poly(vinylidene fluoride) (PVDF) and hydrophilic poly(vinylpyrrolidone) (PVP) were prepared by melt blending. The crystallization behavior, mechanical properties and hydrophilicity of the binary blends were investigated using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffractometry (WAXD), differential scanning calorimeter (DSC) scanning, non-isothermal crystallization kinetics, successive self-nucleation and annealing (SSA) fractionation, tensile tests and contact angle tests. The analysis of FTIR, WAXD, DSC scanning, non-isothermal crystallization kinetics and SSA fractionation showed that the addition of PVP greatly influenced the crystallization behavior of the sample. As the PVP content increased, the crystallization temperature, crystallization rate, degree of crystallinity, and the amount of thick lamellaes decreased gradually. Meanwhile, PVP favored the formation of β-phase of PVDF. The results of tensile test revealed that the addition of PVP increased the elongation at break of the sample, and lowered the yield stress. Besides, the result of contact angle test indicated that the hydrophilicity of PVDF was remarkably improved in the presence PVP. The relationship between crystallization behavior and the tensile behavior, hydrophilicity were discussed. 相似文献
17.
Sushilkumar A. Jadhav Daniele Marchisio Alessandra Vitale Roberta Bongiovanni 《Colloid and polymer science》2014,292(11):3003-3011
Magnetite nanoparticles were synthesized and their post-synthesis surface modification was carried out with triethoxy terminated perfluoropolyether (PFPE) oligomers. The surface-treated nanoparticles were then dispersed in a UV-curable difunctional methacrylic PFPE oligomer. Thin films prepared from the resulting stable suspensions were photopolymerized. The obtained nanocomposites showed good distribution of the surface-treated magnetite nanoparticles in the polymer matrix. The surface treatment of magnetite nanoparticles with perfluoropolyether oligomers thus was found to be effective in preventing nanoparticle segregation and aggregation, ensuring therefore an increased compatibility with the PFPE matrix. 相似文献
18.
P. van der Straten R. Morgenstern A. Niehaus 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,8(1):35-45
We have reformulated the theory of post-collision interaction (PCI) for Auger-decay following inner-shell photoionisation in order to take the time into account with the Auger-electron need to overtake the slow electron. The energy-shift of the Auger-electron due to PCI is calculated by solving in a reasonable approximation the classical equation of motion for the Auger electron. In contrast to the theory of Russek and Mehlhorn we derive analytical expressions for the transition amplitude, the line shape and the line shift of the Auger-electrons. If in our model the Auger electron and the slow electron are treated uncorrelated in direction our analytical expressions agree well with the numerical results of Russek and Mehlhorn. However if we account for directional electron-electron correlations, we show that deviations from the theory of Russek and Mehlhorn are to be expected. The possibility of detecting these deviations is discussed. 相似文献
19.
Xiaolin Qiu Lixin Lu Zhixiong Zhang Guoyi Tang Guolin Song 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1441-1449
This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n-octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g?1) and crystallization (94.8 J g?1) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/n-octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n-octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential. 相似文献
20.
Mamoun A. Muhammed 《Journal of Radioanalytical and Nuclear Chemistry》1976,30(2):411-417
The extraction of hydrochloric acid by trilaurylamine (TLA) dissolved in benzene was studied in the presence and in absence of n-octanol. The extraction of HCl was found to be enhanced by the addition of octanoi to the organic phase. In order to explain this effect by means of the law of mass action, the systems TLA-HCL-benzene and n-octanol-HCl-benzene as well as TLA-octanol-benzene were also studied. It was found that TLA reacts with octanol to form a complex, TLAROH, while the octanol itself associates in benzene to form dimers and tetramers, although it does not extract HCl alone from the dilute solutions used in the present study. The enhancement of the extraction of HCl by TLA upon the addition of n-octanol could be described by the formation of the species TLA·ROH·HCl and its stability constant was determined. 相似文献