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981.
A V-shaped spacroscopic cell(V-cell) was constructed using two CaF2 optical plates for FTIR light transparent measurements in the range of 4000-1000 cm-1.The spectrum of ethanol was characterized with the standard spectra,excellent fitting was achieved with a bottom-width correction method.The principle of the V-cell was discussed,giving equations for the data interpretation.It shows that the V-cell is an auto-focus type spectroscopic cell,which can effectively avoid absorption saturation with amplifications for weak absorption bands.The V-cell design is simple and effective,easy to operate,suitable for applications in liquid samples with high absorption bands,willing to have broad application prospects. 相似文献
982.
983.
Pedram Fatehi Robin Singh Zainab Ziaee Huining Xiao Yonghao Ni 《European Polymer Journal》2011,(5):997-1004
The cationization of polymers has been regarded as an effective method to improve their performance for various applications. In this work, the cationization of poly vinyl alcohol (PVA) was investigated under different conditions, i.e., various glycidyl-trimethylammonium chloride (GTMAC) to PVA ratios, reaction temperatures, times, PVA and NaOH concentrations and solvent compositions. The results showed that the overall efficiency of the cationic modification was rather low, which was due to the hydrolysis of both GTMAC and cationic-modified PVA (CPVA) under the strong alkaline conditions employed. The results also showed that the optimum GTMAC/PVA ratio depended on the solvent composition. The cationization was confirmed by means of 1H NMR and FTIR analyses. The maximum efficiency in water was obtained under the conditions of 95 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration, while that in the ethanol/DMSO mixture (1.25 v/v) was obtained under the conditions of 70 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration. Additionally, the interaction of CPVAs with a silicon wafer (as a substrate) was determined by employing an atomic force microscope (AFM) in water and air. 相似文献
984.
A dynamic surface tension detector (DSTD) has been equipped with an additional pressure sensor for simultaneous viscosity measurements, as a detector for flow injection analysis. The viscosity measurement is based on a single capillary viscometer (SCV) placed in parallel configuration with the DSTD. The viscometer in the optimized conditions consists of a PEEK capillary (i.d. = 0.25 mm, L = 75 cm) kept at constant temperature using a thermostatic bath, which leads on the two sides to the two arms of a differential piezoelectric pressure transducer with a range of 0-35 psi. The DSTD, described previously, measures the changing pressure across the liquid/air interface of 2 μL drops repeatedly forming at the end of a capillary.SCV performance has been evaluated by measuring dynamic viscosity of water/glycerol mixtures analysed in flow injection and comparing the results with the values reported in the literature. The detection limits of SCV and DSTD, calculated as 3σ of the blank, were 0.012 cP and 0.6 dyn cm−1, respectively.The FI-SCV-DSTD system has been applied to the study of temperature-induced denaturation/aggregation process in bovine serum albumin (BSA).The results have been supported and discussed with respect to BSA conformational analysis performed using Fourier Transform infrared spectroscopy. 相似文献
985.
This work describes the use of layered double hydroxides (LDHs) for the immobilisation of acetylcholinesterase (AChE) on insulator/semiconductor solid supports. Different LDHs have been synthesised by a co-precipitation method. Afterwards, biohybrid materials based on AChE-LDH mixtures have been produced using wild and recombinant enzymes. Spectroscopic techniques have confirmed the LDH phase identity and the links created between the LDH and AChE. Spectrophotometric assays have demonstrated that most of the biohybrid materials are functional and stable. Several configurations have been used for AChE immobilisation. The highest catalytic responses have been observed when using wild enzyme and immobilising AChE-LDH mixtures on LDHs previously deposited on the solid supports. LDHs have been demonstrated to be suitable host matrices for AChE immobilisation on electrodes for the subsequent development of electrochemical biosensors. 相似文献
986.
987.
An important characteristic of n-alkanes and fatty acids is the great diversity of solid-state structures, which we can hardly imagine from their simple molecular structures. The variety of crystalline states can be categorized with two concepts: polymorphism and polytypism. Polytypism refers to higher-order structural variation caused solely by the stacking mode of molecular layers. Two basic polytypic structures, single-layer and double-layer, were confirmed in several modifications of n-alkanes and fatty acids having an O⊥ subcell. During the last decade, the two basic polytypes of n-alkanes have been intensively studied mainly by vibrational spectroscopy, with a focus on their formation conditions, thermodynamic stability, and molecular motions. This review summarizes new progress in the context of research on the polytypism of long-chain compounds. 相似文献
988.
Arjunan V Isaac AS Rani T Mythili CV Mohan S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(5):1625-1632
The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-6-methoxypyridine have been recorded in the range 3700-400 and 3700-100 cm(-1), respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound was carried out using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound. The geometry and normal modes of vibration obtained from the DFT methods are in good agreement with the experimental data. The normal co-ordinate analysis was also carried out using DFT force fields utilising Wilson's FG matrix method. The influence of the substituents bulky chlorine atom and the methoxy group on the spectral characteristics of the compound has been discussed. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum. 相似文献
989.
Arjunan V Mythili CV Mageswari K Mohan S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):245-253
The FT-IR (4000-400 cm(-1)) and FT-Raman (4000-100 cm(-1)) spectral measurements of benzamide oxime and complete assignments of the observed spectra have been proposed. Ab initio and DFT calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, IR intensities, Raman activities and atomic displacements. Furthermore, force field calculations have been performed by normal coordinate analysis. Force field calculations showed that several normal modes are mixed in terms of the internal coordinates. A complete assignment of the observed spectra, based on spectral correlations, electronic structure calculations and normal coordinate analysis, has been provided. 相似文献
990.
Karthikeyan B Pandiyarajan T Mangaiyarkarasi K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,82(1):97-101
Optical properties of Ca doped ZnO nanoparticles prepared at room temperature through wet chemical method have been investigated. X-ray diffraction studies show that particles are crystalline in nature and doping did not induce impurity phases. Optical absorption measurements show an absorption peak at ∼372 nm which is due to excitonic absorption of the ZnO. Photoluminescence studies reveal a broad emission at an excitation wavelength of 335 nm and the bands are attributed to near band edge emission, oxygen vacancies, surface dangling bonds and zinc interstitials. Incorporating Ca2+ induces reduction in near band edge emission and there is an enhancement in the oxygen vacancy peaks which are attributed to the shape changes in the nanoparticles. 相似文献