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排序方式: 共有5658条查询结果,搜索用时 203 毫秒
941.
942.
Xiaohang Zhang Christopher A. Paddon Yohan Chan Philip C. Bulman‐Page Paul S. Fordred Steven D. Bull Ho‐Chol Chang Nadeem Rizvi Frank Marken 《Electroanalysis》2009,21(12):1341-1347
Mineral oil microdroplets containing the model antioxidant N,N‐didodecyl‐N′,N′‐diethyl‐phenylene‐diamine (DDPD) are immobilized into a 100×100 pore‐array (ca. 10 μm individual pore diameter, 100 μm pitch) in a boron‐doped diamond electrode surface. The robust diamond surface allows pore filling, cleaning, and reuse without damage to the electrode surface. The electrode is immersed into aqueous electrolyte media, and voltammetric responses for the oxidation of DDPD are obtained. In order to further improve the current responses, 20 wt% of carbon nanofibers are co‐deposited with the oil into the pore array. Voltammetric signals are consistent with the oxidation of DDPD and the associated transfer of perchlorate anions (in aqueous 0.1 M NaClO4) or the transfer of protons (in aqueous 0.1 M HClO4). From the magnitude of the current response, the DDPD content in the mineral oil can be determined down to less than 1 wt% levels. Perhaps surprisingly, the reversible (or midpoint) potential for the DDPD oxidation in mineral oil (when immersed in 0.1 NaClO4) is shown to be concentration‐dependent and to shift to more positive potential values for more dilute DDPD in mineral oil solutions. An extraction mechanism and the formation of a separate organic product phase are proposed to explain this behavior. 相似文献
943.
Lingchao Jiang Huizi Gu Xingzhong Xu Xinhuan Yan 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):144-149
Carbon nanotubes (CNTs), γ-alumina (γ-Al2O3) and silica (SiO2) supported Pt and Pd catalysts were produced by laser vaporization deposition of respective bulk metals. The catalysts were characterized by inductive coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic properties of the catalysts were investigated in the liquid phase hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) under 333 K and 1.0 MPa hydrogen pressure. The results show that the catalytic properties are greatly affected by the supports. Pt/CNTs catalyst exhibits the best catalytic performance among the Pt-based catalysts, producing o-CAN with 99.6% selectivity at complete conversion. Pd/CNTs catalyst exhibits the best catalytic performance among the Pd-based catalysts, giving o-CAN with 95.2% selectivity at complete conversion. For Pt-based catalysts, geometric effect and the textures and properties of the supports play important roles on catalytic properties. On the other hand, geometric effect, electronic effect and the textures and properties of the supports simultaneously influence the catalytic properties of the Pd-based catalysts. In addition, hydrogenolysis of the C–Cl bond can be well inhibited over all catalysts prepared by laser vaporization deposition. 相似文献
944.
ukasz Chacaga Evan B. Jochnowitz Zohra Guennoun Hongbin Ding John P. Maier 《International journal of mass spectrometry》2009,280(1-3):174
The gas-phase electronic spectrum of cyclic-B3 (D3h) radical has been remeasured in a supersonic molecular beam using a mass-selective resonant 2-color 2-photon technique, leading to a revision of previously reported spectroscopic constants. The species was prepared by ablation of a boron nitride rod in the presence of helium. Ab intio calculations on the geometries and vertical electronic excitation energies, as well as mass identification, indicate that the detected band, centered at 21848.77(2) cm−1, is the origin of the cyclic-11B3 system. A spectral fit yields the rotational constants as B″ = 1.2246(45) and C″ = 0.62131(72) cm−1 in the ground state, and B′ = 1.1914(44) and C′ = 0.61173(69) cm−1 in the excited 2 2E′ state. 相似文献
945.
Alvarado Tarun Norihiko Hayazawa Satoshi Kawata 《Analytical and bioanalytical chemistry》2009,394(7):1775-1785
Tip-enhanced Raman spectroscopy (TERS), which utilizes the strong localized optical field generated at the apex of a metallic
tip when illuminated, has been shown to successfully probe the vibrational spectrum of today’s and tomorrow’s state-of-the-art
silicon and next-generation semiconductor devices, such as quantum dots. Collecting and analyzing the vibrational spectrum
not only aids in material identification but also provides insight into strain distributions in semiconductors. Here, the
potential of TERS for nanoscale characterization of strain in silicon devices is reviewed. Emphasis will be placed on the
key challenges of obtaining spectroscopic images of strain in actual strained silicon devices.
Figure Figure Concept of Tip Enhanced Raman Spectroscopy (TERS), which utilizes the strong localized optical field generated at the
apex of a metallic tip when illuminated. TERS has been demonstrated to successfully probe the vibrational spectrum of today’s
and tomorrow’s state-of-the-art silicon and next generation semiconductor devices 相似文献
946.
The discovery and use of fluorescent proteins has revolutionized cellular biology. Despite the widespread use of visible fluorescent
proteins as reporters and sensors in cellular environments the versatile photophysics of fluorescent proteins is still subject
to intense research. Understanding the details of the photophysics of these reporters is essential for accurate interpretation
of the biological and biochemical processes illuminated by fluorescent proteins. Some aspects of the complex photophysics
of fluorescent proteins can only be observed and understood at the single-molecule level, which removes averaging inherent
to ensemble studies. In this paper we review how single-molecule emission detection has helped understanding of the complex
photophysics of fluorescent proteins.
相似文献
Vinod SubramaniamEmail: |
947.
We report on the characterization of structural modifications created by micro-explosions at the beam waist of a tightly focused femtosecond laser pulse inside of GeO2 glass. Micro-Raman scattering revealed the presence of structurally strongly modified regions at and around the irradiated sites. For separations of 5 μm between adjacent irradiated sites structural modifications due to a pressure increase are observed, whereas smaller spacings of 2 μm lead to thermal effects and crystallization. The mechanisms and the interplay of pressure and temperature effects are discussed. 相似文献
948.
Laser induced breakdown spectroscopy (LIBS) was applied for the elemental analysis of Arabian crude oil residue samples. The spectra due to trace elements such as Ca, Fe, Mg, Cu, Zn, Na, Ni, K and Mo were recorded using this technique. The dependence of time delay and laser beam energy on the elemental spectra was also investigated. Prior to quantitative analysis, the LIBS system was calibrated using standard samples containing these trace elements. The results achieved through this method were compared with conventional technique like inductively coupled plasma. 相似文献
949.
The novel approach using a slope of correlation line (laser-enhanced ionization of lithium versus laser-induced plasma emission of aluminum) as analytical signal was proposed for reduction of matrix interferences in laser-enhanced ionization spectrometric determination of Li with laser sampling. 相似文献
950.
Jadranka Blazevska-Gilev Jan Šubrt Anna Galíková 《Polymer Degradation and Stability》2006,91(9):2241-2248
Pulsed IR laser-induced decomposition of poly(vinyl acetate) (PVAC) loaded with nanometer-sized Cu and micrometer-sized Fe particles results in the formation of gaseous products and deposition of polar crosslinked polymer films which contain metal (Cu and Fe) particles. The main volatile products are hydrocarbons, carbon oxides (CO and CO2), molecular hydrogen and acetic acid. The deposited polymer films were characterized by FTIR, UV and XP spectra and by electron microscopy and thermogravimetry. They contain reactive conjugated CC bonds and ca. 50% of the initially present acetate groups. Residual reactivity of the CC bonds results in polymer crosslinking and decrease in solubility. The deposited, crosslinked PVAC-based films containing metal particles are less thermally stable than similar films not containing these particles. The reported process reveals feasible ablation of metal particles when embedded in a polymer and makes it possible to fabricate films of metal/polymer composites in which metal particles are completely protected by the polymer. 相似文献