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排序方式: 共有390条查询结果,搜索用时 31 毫秒
361.
Alexios Papadimitratos Aram Amassian Aravind S. Killampalli Jared L. Mack George G. Malliaras James R. Engstrom 《Applied Physics A: Materials Science & Processing》2009,95(1):29-35
Top-contact organic thin-film transistors (OTFTs) of pentacene have been fabricated on bare SiO2 and SiO2 modified with hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS). The pentacene films were deposited from a supersonic
molecular beam source with kinetic energy of incident molecules ranging from 1.5 to 6.7 eV. The field-effect mobility of OTFTs
was found to increase systematically with increasing kinetic energy of the molecular beam. The improvements are more important
on HMDS- and OTS-treated surfaces than on bare SiO2. Tapping mode atomic force microscopy images reveal that pentacene thin films deposited at high kinetic energy form with
significantly larger grains—independent of surface treatment—than films deposited using low-energy beams. 相似文献
362.
Archana Aravind Maria Sebastian 《International journal of environmental analytical chemistry》2019,99(4):380-395
This article report microwave assisted green method for the synthesis of silver nanoparticle from Brassica oleracea var. Italica (BI) extract. The synthesized silver nanoparticle (AgNP-BI) was characterized by various analytical techniques. Here we are reporting three methods for the sensing of Ni (II) from the synthesized AgNP-BI. First one is the detection of Ni (II) ion based on changes in the absorbance resulting from the complex formation of the Ni (II) ion with AgNP-BI. The second one is the fluorescent sensing of Ni (II) ion using AgNP-BI by the changes in the fluorescence intensity. The third one is the electrochemical sensing of Ni (II) ion in which silver nanoparticle attached to the platinum electrode surface. The above-mentioned methods exhibit outstanding selectivity towards Ni (II) ion. The practical application of the AgNP-BI was also carried out for the trace determination of Ni (II) ions. The limit of detection was found to be 0.932 µM using differential pulse voltammetry (DPV). 相似文献
363.
A series of three bis-tridentate bridging ligands has been prepared in which two 1,10-phenanthroline units have been symmetrically appended to a central pyridazine, pyrimidine, or pyrazine ring. These ligands have been treated with [Ru(tpy-d(11))Cl(3)] to afford both mono- and bimetallic complexes that show very self-consistent NMR properties. [structure: see text] 相似文献
364.
Subhash Chander Seema Lakhanpal Anjali Krishnamurthy Bipin K. Srivastava V. K. Aswal 《Pramana》2004,63(2):345-350
Magnetization measurements are reported on a nano-particle sample of Znsubstituted spinel ferrite Fe2.8Zn0.2O4 in the temperature range 20–300 K. Analysis of small-angle neutron scattering data shows the sample to have a log-normal particle size distribution of median diameter 64.4 Å and standard deviation 0.38. Magnetization evolves over a long period of timet going nearly linearly with logt. Magnetic anisotropy, estimated by fitting M-logt curve, shows many fold increase over that of bulk particle sample. Major enhancement owes to disordered moments in surface layer. In the nano-particle state as well increasing amount of Zn causes anisotropy to decrease. 相似文献
365.
Polycrystalline samples of bismuth (Bi) doped lead lanthanum zirconate titanate (PLZT) with the general formula Pb0.9(La1−zBiz)0.1(Zr0.65Ti0.35)0.975O3, where [z=0.0, 0.3, 0.5, 0.7] near the morphotropic phase boundary (MPB) has been synthesized by a solid solution mixing technique. Some aspect of crystal structure of the compound at room temperature was studied using X-ray diffraction (XRD) technique. Detailed studies of dielectric constant (ε) and dielectric loss () obtained both as a function of frequency (100 Hz-100 kHz) at room temperature (RT) and temperature (RT-600 K) at 10 kHz suggest that compounds undergo ferroelectric-paraelectric phase transition of diffuse type. Both ac and dc conductivity have been studied over a wide range of temperature. The activation energy (Ea) of the samples was calculated from the plot of ac conductivity vs. inverse of absolute temperature. The temperature variation of resistivity shows that the compounds have negative temperature coefficient of resistance (NTCR). 相似文献
366.
A.K. Panda Seema KumariI. Chattoraj M. GhoshA. Mitra 《Journal of magnetism and magnetic materials》2007
The investigation addresses the electron transport properties of Co71−xFexCr7Si8B14 (x=0, 2, 3.2, 4, 6, 8 and 12 at%) amorphous alloys. The variation in electrical resistivity of as-cast amorphous materials with thermal scanning from room temperature to 1000 K was measured. The CoFe-based alloys revealed an initial decrease in temperature coefficient of resistivity (TCR), a characteristic of spin-wave phenomena in glassy metallic systems. This behaviour in the present alloys was in a sharp contrast to the Co-based amorphous materials that indicate the drop in resistivity much below room temperature. In the studied alloys, the variation in initial TCR values and the full-width at half-maxima determined from X-ray diffraction of as-quenched materials exhibited a similar trend with increasing Fe content, indicating the compositional effect of near neighbouring atoms. After the initial decrease in resistivity, all the alloys indicated a subsequent increase at Tmin. The Curie temperature (TC), which was measured from thermal variation of ac susceptibility showed non-monotonic change with Fe content. In the temperature range between Tmin and TC the relative scattering by electron-magnon and electron-phonon resulted in the non-monotonic change in Curie temperature. At crystallization onset (TX1) all the alloys except there with X=6, showed a sharp decrease in electrical resistivity which was attributed to ordering phenomena. In contrast to this resistivity decrease, X=6 alloy exhibited a drastic increase in resistivity around TX1 observed during amorphous to nanocrystalline transformation. Such nanocrystalline state was observed by Transmission electron microscopy. 相似文献
367.
We unfold a rapid synthetic protocol for the preparation of imidazo[1,2-a]pyridine in cyclohexane. This methodology includes several advantages like shorter reaction time, catalyst free, broader substrate scope, and good yields of the desired products. Late stage functionalization of imidazo[1,2-a]pyridine has also been performed through C–H bond activation and C–C cross-coupling reactions. 相似文献
368.
Reetu Yadav Mulayam Singh Gaur Seema Bhadauria Anna N. Berlina Boris B. Dzantiev 《International journal of environmental analytical chemistry》2018,98(6):570-581
This article deals with the detection of Co(II) in real water sample using aptamer – reactant platform combination with activated Ag–Au alloy nanoparticles (NPs) by chemiluminescence (CL) method. CL is attributed to a catalytically enhanced decomposition of H2O2 by aptamer conjugated Ag–Au alloy NPs to produce reactive oxygen species. The Ag–Au alloy NPs were prepared by chemical method using double reducing agent (i.e. trisodium citrate and polyethylenimine) and used for detection of Co(II) from water by CL method. CL experiments were carried out with the variation of different parameters such as pH, concentration of luminol, concentration of H2O2 and Ag–Au alloy NPs. We found that Ag–Au alloy NPs have very good efficiency towards Co(II) detection. Analytical parameters and kinetics were studied in detail to know the nature and mechanism of CL in presence of aptamer conjugated Ag–Au alloy NPs. The linear range of the CL sensor of Co(II) is covered concentration from 0.01 to 10 µg/L with detection limit of 0.001 µg/L. The relative standard deviation for determination of Co(II) was 6.65 in 10 replicated measurements. CL method is first time applied to detect the Co(II) in real water samples at very low level using aptamer conjugated Ag–Au NPs as a catalyst. 相似文献
369.
Muhammed Hamdan Dr. Aravind Kumar Chandiran 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16167-16172
Halide perovskites show incredible photovoltaic power conversion efficiency coupled with several hundreds of hours of device stability. However, their stability is poor in aqueous electrolyte media. Reported here is a vacancy ordered halide perovskite, Cs2PtI6, which shows extraordinary stability under ambient conditions (1 year), in aqueous media of extreme acidic (pH 1), basic (pH 13), and under electrochemical reduction conditions. It was employed as an electrocatalyst and photoanode for hydrogen production and water oxidation, respectively. The catalyst remains intact for at least 100 cycles of electrochemical cycling and six hours of hydrogen production at pH 1. Cs2PtI6 was employed as a photoanode for PEC water oxidation, and the material displayed a photocurrent of 0.8 mA cm−2 at 1.23 V (vs. RHE) under simulated AM1.5G sunlight. Using constant voltage measurement, Cs2PtI6 exhibited over 12 hours of PEC stability without loss of performance. 相似文献
370.
Despite much study, biomolecule folding cooperativity is not well understood. There are quantitative models for helix-coil transitions and for coil-to-globule transitions, but no accurate models yet treat both chain collapse and secondary structure formation together. We develop here a dynamic programming approach to statistical mechanical partition functions of foldamer chain molecules. We call it the ascending levels model. We apply it to helix-coil and helix-bundle folding and cooperativity. For 14- to 50-mer Baldwin peptides, the model gives good predictions for the heat capacity and helicity versus temperature and urea. The model also gives good fits for the denaturation of Oas's three-helix bundle B domain of protein A (F13W*) and synthetic protein alpha3C by temperature and guanidine. The model predicts the conformational distributions. It shows that these proteins fold with transitions that are two-state, although the transitions in the Baldwin helices are nearly higher order. The model shows that the recently developed three-helix bundle polypeptoids of Lee et al. fold anti-cooperatively, with a predicted value of DeltaHvH/DeltaHcal = 0.72. The model also predicts that two-helix bundles are unstable in proteins but stable in peptoids. Our dynamic programming approach provides a general way to explore cooperativity in complex foldable polymers. 相似文献