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991.
In this study, poly(?-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8 wt% PCL-PU solutions containing different amounts of AgNO3 in a mixed solvent consisting of DMF/THF (7/3 w/w). The average diameter of the pure PCL-PU nanofibers was 560 nm and decreased with increasing concentration of AgNO3. The PCL-PU nanofiber mats electrospun with AgNO3 exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag+ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100 °C for 24 h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well. 相似文献
992.
Hyun Lee Dong Hun Lee Takeshi Kanashima Masanori Okuyama 《Applied Surface Science》2008,254(21):6932-6936
Chemical reactivity of fluorine molecule (F2)-germanium (Ge) surface and dissociation of fluorine (F)-Ge bonding have been simulated by semi-empirical molecular orbital method theoretically, which shows that F on Ge surface is more stable compared to hydrogen. Ge MIS (metal insulator semiconductor) capacitor has been fabricated by using F2-treated Ge(1 0 0) substrate and HfO2 film deposited by photo-assisted MOCVD. Interface state density observed as a hump in the C-V curve of HfO2/Ge gate stack and its C-V hysteresis were decreased by F2-treatment of Ge surface. XPS (X-ray photoelectron spectroscopy) depth profiling reveals that interfacial layer between HfO2 and Ge is sub-oxide layer (GeOx or HfGeOx), which is believed to be origin of interface state density.F was incorporated into interfacial layer easily by using F2-treated Ge substrate. These results suggest that interface defect of HfO2/Ge gate stack structure could be passivated by F effectively. 相似文献
993.
Electron injection behavior of lithium quinolate (Liq)/Ca/Al cathode was investigated by using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy (UPS). Interfacial energy barrier lowering of Liq/Ca/Al cathode was dependent on Ca thickness and maximum energy level shift was observed at a Ca thickness of 1 nm. Maximum current density could be obtained in Liq/Ca/Al device at a Ca thickness of 1 nm and it was well correlated with energy level shift from UPS measurement. Power efficiency of Liq/Al device could be improved by more than 70% by inserting Ca layer between Liq and Al. 相似文献
994.
Hyun Cheol Koo Jae Hyun Kwon Jonghwa Eom Joonyeon Chang Suk-Hee Han 《Journal of magnetism and magnetic materials》2008
The spin transport signals from NiFe and Co into two-dimensional electron gas layers are measured for various thicknesses of transmission barriers. A stable and reproducible electrical detection of spin transport was obtained only when the barrier thickness is less than 10 nm. The typical interface resistance to observe spin signals in this experiment is about 0.5–250 Ω, which is a neither transparent nor a severe tunneling limit. The optimal interface resistance depends on the ferromagnetic materials, but severe tunneling barrier is not proper for fully electrical spin transport. Device size is also a critical factor to decide the proper range of interface resistance. 相似文献
995.
Gjergj Dodbiba Hyun Seo ParkKatsunori Okaya Toyohisa Fujita 《Journal of magnetism and magnetic materials》2008
In this work, properties of a magnetorheological (MR) fluid, prepared by dispersing a mixture of two types of carbonyl iron powders (CIPs) of different sizes, in an ionic liquid (N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate) that is stable from 9 °C to ca. 300 °C, have been investigated. At first, the random packing density of the mixture was computed as function of mixing ratio of CIP, in order to find out the tendency of the variation. Next, several mixtures, all having the same weight, were prepared at various mixing ratios and dispersed in the ionic liquid, in order to experimentally find the most suitable mixing ratio of CIP. Then, the magnetic clusters of the synthesized MR fluids were observed by using a digital microscope equipped with two permanent magnets, whereas the MR properties were investigated by using a rotation viscometer equipped with a solenoid coil. The experimental results pointed out that the MR fluid with 60 wt% fraction of large particles exhibited the highest MR response. 相似文献
996.
Manoj K. Singh Hyun M. Jang H. C. Gupta Ram S. Katiyar 《Journal of Raman spectroscopy : JRS》2008,39(7):842-848
The first‐ and second‐order Raman‐active phonons in the orthorhombic Pbnm NdFeO3 single crystals were studied by means of polarized Raman scattering and lattice dynamics computations (LDC). The zone‐center phonons of Ag symmetry were distinguished from the B1g eigenmodes by performing polarized Raman scattering experiments using two parallel polarization configurations, X′(ZZ)X′ and Z(X′X′)Z. With the help of LDC, we were able to assign most of the observed Raman‐active modes, including phonons of B2g and B3g symmetry. The LDC results indicated that among the 16 force constants employed, the one corresponding to the stretching vibration between the central Fe cation and the axial oxygen atom in a FeO6 octahedron unit had the largest value. This suggests that the B‐site Fe cation is more tightly bound to the axial O1 ion than the other two equatorial O2 ions. It was further shown that at higher wavenumbers, the displacement of oxygen atoms contributed dominantly to the zone‐center vibrations. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
997.
We report on free excitons coexisting with exciton magnetic polarons (EMPs) in bulk semimagnetic semiconductors of Cd1−xMnxTe for 0.04?x?0.36 at 2 K under nonresonant two-photon excitation. This two-photon excitation not only generates free excitons but also more efficiently creates EMPs compared with ordinary one-photon excitation. Stimulated emission from free excitons is demonstrated under strong two-photon excitation. 相似文献
998.
The utilization of silver salts of aromatic thiols as core materials of SERS‐based molecular sensors
Kwan Kim Yoon Mi Lee Hyun Sook Lee Kuan Soo Shin 《Journal of Raman spectroscopy : JRS》2008,39(12):1840-1847
Silver salts of aromatic thiols are one class of organic–inorganic heterostructured materials, showing peculiar photoreaction characteristics. When an argon ion laser is exposed to silver benzenethiolate (AgBT), for instance, its Raman spectrum changes over time, eventually becoming the same as the surface‐enhanced Raman scattering (SERS) spectrum of benzenethiol on a roughened Ag substrate. AgBT and its analogs can thus be used as a core material of molecular sensors operating via SERS; we demonstrate this specifically, by monitoring the SERS peaks of BT, in which biotinylated AgBT selectively recognizes streptavidin molecules down to concentrations of 10−11 g ml−1 (i.e. ∼0.2 pM ). Since numerous silver thiolates can be used as the core material, multiple bioassays are readily accomplished using the present methodology. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
Noury F Mispelter J Szeremeta F Même S Doan BT Beloeil JC 《Magnetic resonance imaging》2008,26(10):1421-1432
Intervertebral disc (IVD) degeneration is a complex process characterized by biochemical and structural changes in both the nucleus pulposus and the anulus fibrosus. In this study, we were able to obtain in vivo magnetic resonance (MR) images of the rabbit spine, with several MR imaging (MRI) contrasts (ρ, T1 and T2). We quantified several parameters (T2, apparent diffusion coefficient, disc height and area) to differentiate between healthy and degenerative IVDs and to characterize the degeneration process. To our knowledge, there has not been any previous in vivo study of rabbit IVDs at high-field MRI (9.4 T).A custom radio frequency (RF) coil for 9.4 T was designed to match rabbit IVD morphology, to study the degeneration in vivo on a model of human lumbar disease. Our new probe, a custom half-birdcage-type coil, obtains the necessary exploration depth while meeting the requirements for signal homogeneity and sensitivity of the study. This design addresses some of the difficulties with constructing RF coils at high field strengths. 相似文献
1000.