排序方式: 共有14条查询结果,搜索用时 0 毫秒
1.
Structural Chemistry - Under density functional theory (DFT), a first principle analysis is conducted to pure, boron (B)- and phosphorus (P)-doped silicon-germanium nanosheets. It has been revealed... 相似文献
2.
Cerium-doped Titanium dioxide (TiO(2)) nanoparticles are prepared by sol-gel method. Doping shifts the UV absorption edge of TiO(2) to the visible region, making it efficient for visible light photocatalysis. Incorporation of cerium decreases the effective band gap of TiO(2) and increases the Urbach energy levels. At the dopant concentrations of 0.015 and 0.025 mol the luminescence intensity increases compared to undoped TiO(2); however, the luminescence is quenched at 0.035 mol. Quenching of luminescence indicates efficient separation of charge carriers. Undoped TiO(2) is showing poor performance in the photocatalytic degradation of methyl orange under visible light. However, on cerium doping its photoactivity is increased, and is drastically enhanced at 0.035 mol of cerium. Further increase in Ce(3+) doping level to 0.045 mol results in the reduction of the photodegradation of the dye. On UV irradiation, entire samples show good photocatalytic activity up to 30 min, but their efficiency decreases when irradiation time is increased to 45 min. Irradiation for longer time results in negative charging of the TiO(2) surface with migrating electrons. The negatively charged surface repels the OH(-) ion and O(2) molecule from adsorbing on its surface thus decreasing the availability of hydroxyl and superoxide radical for dye degradation. 相似文献
3.
4.
The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors. 相似文献
5.
Nirmal Misra Mohendra Roy Dambarudhar Mohanta Kishor Kumar Baruah Amarjyoti Choudhury 《Central European Journal of Physics》2008,6(1):109-115
ZnO:Mn semiconductor quantum dots were prepared by solution casting led microemulsion route. Quantum dots of average size
∼2 nm were noticed in transmission electron micrographs. The present work highlights colour change phenomena (photochromic
effect) of quantum dots while subjected to photon illumination. The magneto-optic measurements e.g. magnetic field (H) vs angle of rotation (θ) show step like behavior and is ascribed to the quantum confinement effect of diluted magnetic ZnO:Mn nanostructures. Further,
underlying mechanism responsible for exhibiting photochromism and magneto-optic effects are also discussed.
相似文献
6.
7.
Mn doped TiO2 nanoparticles are synthesized by sol–gel method. Incorporation of Mn shifts the diffraction peak of TiO2 to lower angle. The position and width of the Raman peak and photoluminescence intensity of the doped nanoparticles varies with oxygen vacancy and Mn doping level. The electron spin resonance spectra of the Mn doped TiO2 show peaks at g = 1.99 and 4.39, characteristic of Mn2+ state. Reduction in the emission intensity, on Mn doping, is owing to the increase of nonradiative oxygen vacancy centers. Mn doped TiO2, with 2% Mn, shows ferromagnetic ordering at low applied field. Paramagnetic contribution increases as Mn loading increases to 4% and 6%. Temperature dependent magnetic measurement shows a small kink in the ZFC curve at about 40 K, characteristic of Mn3O4. The ferromagnetic ordering is possibly due to the interaction of the neighboring Mn2+ ions via oxygen vacancy (F+ center). Increase in Mn concentration increases the fraction of Mn3O4 phase and thereby increases the paramagnetic ordering. 相似文献
8.
TiO2 nanoparticles doped with two different concentrations of Cobalt, 0.02 and 0.04 mol, are prepared by sol–gel method. The crystalline phase of the doped and undoped nanoparticles and particle sizes are observed with X-ray diffraction and transmission electron microscope. FTIR confirms the bonding interaction of Co2+ in TiO2 lattice framework. The UV absorption spectra of the doped material shows two absorption peaks in the visible region related to d–d electronic transitions of Co2+ in TiO2 lattice. Compared to undoped TiO2 nanoparticles, the cobalt doped samples show a red shift in the band gap. Steady state photoluminescence spectra give emission peaks related to oxygen defects. The decrease in the intensity ratio of UV/visible emission peaks confirms distortion of structural regularity and formation of defects after doping. The intensity ratio of different visible emission peaks is nearly same for undoped and 0.02 Co2+. However, this ratio decreases profoundly at 0.04 Co2+, due to concentration quenching effect. Photoluminescence excitation spectra, recorded at 598 nm emission wavelength, give different excitation peaks associated with oxygen vacancies and Co2+. Time resolved photoluminescence spectra give longer decay time for doped samples, indicating longer relaxation of conduction band electrons on the defect and on dopant sites. 相似文献
9.
Ankur Gogoi Alak K. Buragohain Amarjyoti Choudhury Gazi A. Ahmed 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(14-16):1566-1578
Laser light scattering characteristics of tropical fresh water diatoms and their siliceous frustules have been measured as a function of scattering angle at 543, 594 and 632 nm wavelengths by using an indigenously designed and fabricated laboratory light scattering instrument in an attempt to carryout morphological characterization of the unique regular structures specific to these type of tropical fresh water diatoms. The instrument incorporates an array of 16 highly sensitive static Si detectors that measured scattered light signals from 10° to 170° in steps of 1°. A comparative analysis between the results obtained by using the three different incident wavelengths has shown that highest resolution is obtained at 543 nm incident wavelength. 相似文献
10.
Luminescence studies of fresh water diatom frustules 总被引:1,自引:0,他引:1
Nirmal Mazumder Ankur Gogoi Ranjan Dutta Kalita Gazi A. Ahmed Alak K. Buragohain Amarjyoti Choudhury 《Indian Journal of Physics》2010,84(6):665-669
Siliceous frustules were extracted from fresh water diatoms by treating with concentrated HCl. The diatom frustules consist
of nano-porous silica structures that exhibit unique optoelectronic and photonic properties. Photoluminescence (PL) properties
of diatom frustules at various excitation wavelengths were done. A visible PL band centered at 440 nm was observed when excited
at 300 nm, 370 nm and 380 nm wavelengths. The observed PL activity of the diatom frustules has the potential for use in optoelectronic
and photonic devices. 相似文献