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991.
992.
荧光光谱法研究头孢孟多脂与牛血清白蛋白的相互作用 总被引:1,自引:0,他引:1
模拟生理条件下,用荧光光谱法和紫外-可见吸收光谱法研究头孢孟多酯和牛血清白蛋白(BSA)结合反应的特征。研究表明:头孢孟多酯与BSA形成复合物,从而猝灭BSA的内源性荧光,该过程为静态猝灭过程。根据SternVolmer方程得出不同温度下结合位点数n和结合常数Ka;结合位点位于BSA的亚结构IIA中。通过计算相应的热力学参数,确定头孢孟多酯与BSA之间的作用力主要为静电作用力。利用同步荧光光谱探讨了头孢孟多酯与BSA作用前后白蛋白的构型变化。Hill系数nH1,表明头孢孟多酯有弱的负协同作用。此研究不仅对于揭示体内药物动力学问题和指导临床合理用药具有一定意义,而且对药物分子设计及新药开发等也具有重要指导意义。 相似文献
993.
M Waqas Iqbal M Zahir Iqbal M Farooq Khan Xiaozhan Jin Chanyong Hwang 《Science and Technology of Advanced Materials》2014,15(5)
The properties of graphene are strongly affected by metal adsorbates and clusters on graphene. Here, we study the effect of a thin layer of platinum (Pt) metal on exfoliated single, bi- and trilayer graphene and on chemical vapor deposition-grown single-layer graphene by using Raman spectroscopy and transport measurements. The Raman spectra and transport measurements show that Pt affects the structure as well as the electronic properties of graphene. The shift of peak frequencies, intensities and widths of the Raman bands were analyzed after the deposition of Pt with different thicknesses (1, 3, 5 nm) on the graphene. The shifts in the G and 2D peak positions of the Raman spectra indicate the n-type doping effect by the Pt metal. The doping effect was also confirmed by gate-voltage dependent resistivity measurements. The doping effect by the Pt metal is stable under ambient conditions, and the doping intensity increases with the increasing Pt deposition without inducing a severe degradation of the charge carrier mobility. 相似文献
994.
Dmitry A. Nedosekin Ekaterina I. Galanzha Enkeleda Dervishi Alexandru S. Biris Vladimir P. Zharov 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(1):135-142
Super‐resolution fluorescence microscopy enables imaging of fluorescent structures beyond the diffraction limit. However, this technique cannot be applied to weakly fluorescent cellular components or labels. As an alternative, photothermal microscopy based on nonradiative transformation of absorbed energy into heat has demonstrated imaging of nonfluorescent structures including single molecules and ~1‐nm gold nanoparticles. However, previously photothermal imaging has been performed with a diffraction‐limited resolution only. Herein, super‐resolution, far‐field photothermal microscopy based on nonlinear signal dependence on the laser energy is introduced. Among various nonlinear phenomena, including absorption saturation, multiphoton absorption, and signal temperature dependence, signal amplification by laser‐induced nanobubbles around overheated nano‐objects is explored. A Gaussian laser beam profile is used to demonstrate the image spatial sharpening for calibrated 260‐nm metal strips, resolving of a plasmonic nanoassembly, visualization of 10‐nm gold nanoparticles in graphene, and hemoglobin nanoclusters in live erythrocytes with resolution down to 50 nm. These nonlinear phenomena can be used for 3D imaging with improved lateral and axial resolution in most photothermal methods, including photoacoustic microscopy. 相似文献
995.
996.
Sanjay Kumar 《材料科学与工程:中英文B版...》2014,(12):358-365
In the present work, an array of novel substituted 2H-chromen-2-one (coumarin derivatives abbreviated as C-337, C-480, C-540A) has been subjected to photophysical analysis. Although the influence of the electron donating groups such as amino, substituted amino, hydroxyl, alkoxy groups at position 7 of the coumarin ring system has been extensively studied, However, coumarin moieties with substituent at position 3 have not been explored much. Attempt is made to explain the effect of electron donating and electron accepting substituent on excited state and ground state dipole moment. The ground state (μ) and excited state (μ*) dipole moment of C-337, C-480, C-540A coumarins are estimated from solvatochromic shift of absorption and fluorescence spectra as a function of the dielectric constant and refractive index using Bakhshiev and Kwaski-Chamma Vialletequ. μ* and μ for all the reported coumarin are also calculated using Reichardt correlation method. The small angle is also reported between the ground and excited state dipole moment suggesting that they are almost parallel to each other. Excited state dipole moment is observed larger than ground state dipole moment for all the coumarins studied indicating substantial n-electron density redistribution. 相似文献
997.
Peiyuan Wang Haiping Xia Jiangtao Peng Haoyang Hu Lei Tang Yuepin Zhang Baojiu Chen Haochuan Jiang 《Materials Chemistry and Physics》2014
High quality Er3+/Nd3+:LiYF4 single crystals were grown by a Bridgman method. Their spectroscopic properties were studied to understand the Nd3+ concentration effect upon excitation of an 800 nm laser diode. The intensest 2.7 μm emission was observed in the LiYF4 crystal codoped with 0.99 mol% Er3+ and 0.62 mol% Nd3+. Meanwhile, the emission intensity for the green up-conversion and 1.5 μm downconversion of Er3+ decreased with increasing of the Nd3+ concentration. The modified Inokuti–Hirayama model was used to analyze the decay curves of the 1.06 (Nd3+) and 1.5 (Er3+) μm emissions. The results indicated that the energy transfer process (Er3+:4I13/2 + Nd3+:4I9/2 → Er3+:4I15/2 + Nd3+:4I15/2) is mainly due to the electric dipole–dipole interaction. The energy transfer efficiencies between Nd3+ and Er3+ ions were calculated. All results suggested that the Er3+/Nd3+:LiYF4 single crystals may have potential applications in mid-infrared lasers. 相似文献
998.
Alessandro Di Mauro Emanuele Smecca Alessandro D'Urso Guglielmo G. Condorelli Maria Elena Fragalà 《Materials Chemistry and Physics》2014
A stepwise surface functionalization procedure, based on hybrid covalent and non-covalent approach is herein proposed to anchor tetra-anionic meso-tetrakis(4-sulfonatophenyl)porphyrin on ZnO nanorods. Carboxyalkylphosphonic acids have been proven effective to form stable self-assembled monolayers through the surface grafting of –PO3H2 headgroups. The exposed carboxylic functionalities are suitable for the successful grafting of cationic poly-l-lysine that drives, in water, the non-covalent anchoring of the anionic porphyrin. A stepwise surface characterization, provided by X-ray photoelectron spectroscopy, elucidates the multilayers deposition and surface composition after each process step, thus, giving interesting insights on the chemical speciation of the exposed functionalities. UV–vis spectroscopy confirms the role of ZnO morphology to increase the porphyrin loading onto the investigated surfaces. The proposed approach is effective to achieve deposition of anionic porphyrins on ZnO nanostructures and combines the robustness of covalent functionalization with the versatility and full reversibility of the non-covalent strategies. 相似文献
999.
Anatase TiO2 nanocrystals (NCs) were deposited onto patterned carbon nanotube (CNT) bundle arrays to form a TiO2/CNT composite using metal organic chemical vapor deposition (MOCVD) using titanium-tetraisopropoxide (Ti(OC3H7)4) as a source reagent. The N-doped TiO2/CNT composite was then fabricated using nitrogen plasma treatment. The structural and spectroscopic properties of TiO2/CNT composites were characterized by field-emission scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The combined geometrical structure and low electron affinity effects of N-doped TiO2 led to a low turn-on field of 1.0 V μm−1 at a current density of 10 μA cm−2, a low threshold field of 1.9 V μm−1 at a current density of 1 mA cm−2, a high field enhancement factor of 3.0 × 103, and long-term stability for the N-doped TiO2/CNT composite. The results revealed that the N-doped TiO2/CNT composite can be a potential candidate for field emission devices. 相似文献
1000.
Coal fly ash is a waste by-product of the coal fire industry, which generates many environmental problems. Alternative uses of this material would provide efficient solutions for this by-product. In this work, nitric acid-etched coal fly ash labelled with 2-mercaptoethanol or thioglycolic acid was assessed for retention of Al(III), As(III), Cu(II), Cd(II), Fe(III), Mn(II), Hg(II), Ni(II), Pb(II) and Zn(II) ions. The bonding characteristics between the organic compounds with the solid support, as well as with the metal ions, were evaluated using various surface analytical techniques. Visualization of the organically-functionalized coal fly ash particle was possible using scanning electron microscopy (SEM), while the elemental composition of the functionalized material, before and after retention of the metal ions, was obtained by energy dispersive (ED)-X ray spectrometry (XRS) and electrothermal atomic absorption spectrometry (ETAAS). Fourier transform infrared (FT-IR) spectrometry and Raman spectrometry were used to obtain information about the functional groups. It was found that some metal(oid) ions (As, Ni, Pb, Zn) were coordinated through the mercaptan group, while other metal(oid)s (Al, Cd, Cu, Fe, Hg, Mn) were apparently bonded to oxygen atoms. A low-cost and effective solid phase retention system for extraction of heavy metals from aqueous solutions was thus developed. 相似文献