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991.
Jayabharathi J Thanikachalam V Jayamoorthy K Perumal MV 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):6-16
A group of novel Schiff base derivatives were synthesized and characterized by NMR spectra, X-ray, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy Schiff base (SB4) has been studied using emission spectroscopy and it was detected that the two distinct ground state isomers of I and II are responsible for the emission. The comparison of the emission wavelength in hydrocarbon solvent strongly supports that trans enol form predominates over the cis enol form for Schiff base (SB4). With increasing base concentration of the solutions of hydroxy substituted Schiff bases (SB4 and SB5), two isobestic points are found which confirm the equilibrium among the trans enol form, anion and the cis enol form. The fluorescence of (SB4) quenched markedly with the gradual addition of Cu(2+) but the fluorescence properties of (SB5) was influenced by other metal ions. Therefore Schiff base (SB5) can be used as a new fluorescence sensor to detect the quantity of Cu(2+) ion in any sample solution depending on the relative intensity change. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the Schiff base derivatives were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state. 相似文献
992.
Jayabharathi J Thanikachalam V Perumal MV Srinivasan N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):236-244
Novel donor imidazole derivative, 2-(1-phenyl-1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)-phenol (PIPP) was screened as highly sensitive chemisensor for transition metal ions and it can be used as a "multi-way" optically switchable material. Solvatochromic effects on the fluorescence behaviour of PIPP were studied in different solvents. The fluorescence of PIPP was highly sensitive to both the polarity as well as protic nature of the solvent. Fluorescence (Forster) resonance energy transfer (FRET) process from PIPP to a potent bioactive indoloquinolizine molecule was studied and it is argued that long-range dipole-dipole interaction is operating for the energy transfer mechanism. The energy transfer efficiency (E) and the distance between the acceptor and the donor (r(0)) have been determined. 相似文献
993.
基于辐射传输理论, 利用蒙特卡罗方法模拟了无限窄(冲击函数)准直光束入射到典型水云以及冰水双层云时的后向散射特性, 进而将得到的冲击响应与高斯光束卷积, 得到高斯光束在云层中传输的多次散射特性. 文中给出了两种波束入射时水云以及冰水双层云的反射函数随径向r和天顶角α的变化关系, 并给出了光强在云层内部的二维分布图. 计算结果表明, 高斯光束入射时, 云层反射函数的特点与无限窄准直光束入射时有较大区别. 因此在利用激光雷达进行云层探测时需要考虑激光的散斑, 文中的方法可以为此提供理论依据. 相似文献
994.
G. Venkatesh T. Sivasankar M. Karthick N. Rajendiran 《Journal of inclusion phenomena and macrocyclic chemistry》2013,77(1-4):309-318
PM3 theoretical methodology was used to access and compare the relative stability of inclusion complexes formed by sulphadiazene, sulphisomidine, sulphamethazine and sulphanilamide with β-cyclodextrin (β-CD). The study predicted that (i) the heterocyclic ring is encapsulated in the hydrophobic part and aniline ring is present in the hydrophilic part of the β-CD cavity and (ii) intermolecular hydrogen bonds were formed between host and guest molecules. The negative free energy and enthalpy changes indicated that all the four inclusion complexation processes were spontaneous and enthalpy driven process. HOMO and LUMO orbital investigation confirmed that the stability increased in the inclusion complexes and also proved no significant change in the electronic structure of the guest and host molecules after complexation. 相似文献
995.
采用浸渍法制备了SiO2, γ-Al2O3, CaO和TiO2负载的Ni催化剂, 以及不同MgO含量的MgO-7.5%Ni/γ-Al2O3催化剂,利用X射线衍射和N2吸附-脱附技术表征了催化剂的结构,在固定床反应器上评价了它们在稻草水蒸气催化重整制合成气反应中的催化性能,考察了反应条件对催化剂性能的影响.结果表明, 以γ-Al2O3为载体时Ni催化剂活性最高,其中7.5%Ni/γ-Al2O3催化剂的H2收率可达1071.3ml/g,H2:CO的体积比为1.4:1;同时,MgO的添加进一步提高了该催化剂的性能,当MgO含量为1.0%时,H2收率可达1194.6ml/g,H2:CO体积比可达3.9:1.可见MgO的加入促进了Ni基催化剂上稻草水蒸气催化重整制合成气反应的进行,同时使得合成气中CO发生水-汽转换反应,从而大大提高了合成气中H2含量. 相似文献
996.
Dr. Jing Liu Dr. Katla Sai Krishna Dr. Yaroslav B. Losovyj Dr. Soma Chattopadhyay Dr. Natalia Lozova Prof. Jeffrey T. Miller Prof. James J. Spivey Dr. Challa S. S. R. Kumar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10201-10208
We present results from our investigations into correlating the styrene‐oxidation catalysis of atomically precise mixed‐ligand biicosahedral‐structure [Au25(PPh3)10(SC12H25)5Cl2]2+ (Au25‐bi) and thiol‐stabilized icosahedral core–shell‐structure [Au25(SCH2CH2Ph)18]? (Au25‐i) clusters with their electronic and atomic structure by using a combination of synchrotron radiation‐based X‐ray absorption fine‐structure spectroscopy (XAFS) and ultraviolet photoemission spectroscopy (UPS). Compared to bulk Au, XAFS revealed low Au–Au coordination, Au? Au bond contraction and higher d‐band vacancies in both the ligand‐stabilized Au clusters. The ligands were found not only to act as colloidal stabilizers, but also as d‐band electron acceptor for Au atoms. Au25‐bi clusters have a higher first‐shell Au coordination number than Au25‐i, whereas Au25‐bi and Au25‐i clusters have the same number of Au atoms. The UPS revealed a trend of narrower d‐band width, with apparent d‐band spin–orbit splitting and higher binding energy of d‐band center position for Au25‐bi and Au25‐i. We propose that the differences in their d‐band unoccupied state population are likely to be responsible for differences in their catalytic activity and selectivity. The findings reported herein help to understand the catalysis of atomically precise ligand‐stabilized metal clusters by correlating their atomic or electronic properties with catalytic activity. 相似文献
997.
B. Y. Giri B. L. A. Prabhavathi Devi K. N. Gangadhar K. Narasimha Rao N. Lingaiah P. S. Sai Prasad 《合成通讯》2013,43(1):7-11
Monoammonium salt of 12‐tungstophosphoric acid [(NH4)H2PW12O40] was found to be a practical and useful heterogeneous catalyst for an efficient and selective esterification of aliphatic carboxylic acids with alcohols in the presence of aromatic carboxylic acids. The heteropoly acid–based heterogeneous catalyst has the advantages of a simple workup procedure, water insolubility, and good activity. 相似文献
998.
Prabhakar PK Raj S Anuradha PR Sawant SN Doble M 《Colloids and surfaces. B, Biointerfaces》2011,86(1):146-153
Biocompatibility of medical grade polyurethane coated with polyaniline (PANi) and polyaniline-silver nanoparticle composite (PANi-AgNp) is reported here. These modified films showed 23 and 18% of 3T3 L1 cell death when compared to 41% with virgin polyurethane (PU) after 48h of incubation, respectively. All the surfaces elucidated inflammatory response in the form of enhanced expressions of the proinflammatory cytokines genes, TNF-α and IL-6. But these values were less (by 20%) on modified films than on the bare PU. Attachment of Pseudomonas and Bacillus were markedly less on PANi-AgNp coated surface (by 90.6 and 50.5%, respectively) when compared to the uncoated PU. As the CFU counts decreases on the nanoparticle coated PU, the adsorbed carbohydrate as well as protein content on to the surface of polymer decreases accordingly, indicating less attachment. A 20% reduction in the thickness of biofilm was observed in PANi-AgNp coated PU surface. A very strong positive correlation is observed between the contact angles of the polymers and the various biological parameters (namely colony forming units, protein, carbohydrate, cell death and inflammatory response), indicating hydrophilic surfaces prevent bacterial biofilm as well as are compatible to cells when compared to hydrophobic surfaces. Coating PU with PANi and PANi+AgNp renders the surface conductive, suggesting potential application in electrochemical biosensors. In addition, these modifications make the surface more biocompatible than the original PU. 相似文献
999.
Benzamides with tethered acetal groups undergo reactions in CF3SO3H to give ring-fused isoindolinones by a cyclization cascade. The reaction initially forms an N-acyliminium ion which then gives the isoindolinone by the aza-Nazarov reaction. An unusual variant also cyclizes at the allylic position. 相似文献
1000.
Rubel Chakravarty Meera Venkatesh Ashutosh Dash 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):45-51
A novel electrochemical process to avail clinical grade 99mTc from (n,γ)99Mo has been demonstrated. The electrochemical parameters were optimized to maximize the 99mTc yield with minimal 99Mo contamination. 99Mo/99mTc generators containing up to 29.6 GBq (800 mCi) 99Mo were developed and their performance were extensively evaluated for 10 days without changing the operating conditions.
Very high radioactive concentration of 99mTcO4
− of acceptable quality, commensurate with hospital radiopharmacy requirements could be availed from the system with >90% yield.
The compatibility of the product for the formulation of 99mTc labeled radiopharmaceuticals such as 99mTc-DMSA and 99mTc-EC was found to be satisfactory in terms of high labeling yields. The proposed route represents an important step for enhancing
the scope of accessing clinical grade 99mTc from low specific activity (n, γ)99Mo. 相似文献