Layerwise decomposition of water dynamics in reverse micelles: A simulation study of two-dimensional infrared spectrum

We present computer simulation study of two-dimensional infrared spectroscopy (2D-IR) of water confined in reverse micelles (RMs) of various sizes. The present study is motivated by the need to understand the altered dynamics of confined water by performing layerwise decomposition of water, with an aim to quantify the relative contributions of different layers water molecules to the calculated 2D-IR spectrum. The 0-1 transition spectra clearly show substantial elongation, due to in-homogeneous broadening and incomplete spectral diffusion, along the diagonal in the surface water layer of different sized RMs. Fitting of the frequency fluctuation correlation functions reveal that the motion of the surface water molecules is sub-diffusive and indicate the constrained nature of their dynamics. This is further supported by two peak nature of the angular analogue of van Hove correlation function. With increasing system size, the water molecules become more diffusive in nature and spectral diffusion almost completes in the central layer of the larger size RMs. Comparisons between experiments and simulations establish the correspondence between the spectral decomposition available in experiments with the spatial decomposition available in simulations. Simulations also allow a quantitative exploration of the relative role of water, sodium ions, and sulfonate head groups in vibrational dephasing. Interestingly, the negative cross correlation between force on oxygen and hydrogen of O-H bond in bulk water significantly decreases in the surface layer of each RM. This negative cross correlation gradually increases in the central water pool with increasing RMs size and this is found to be partly responsible for the faster relaxation rate of water in the central pool. (C) 2013 AIP Publishing LLC.

Vibrational spectroscopic studies of the ferroelectric LiRbSO4

Lithium rubidium sulphate, LiRbSO4 (LRS), undergoes a sequence of four phase transitions at 166, 185, 202 and 204°C. The phase between 202 and 204°C is incommensurate. Polarized phonon Raman spectra in the frequency region of 50-1200 cm-1 are presented to identify the external and internal vibrational modes at room temperature. The internal mode frequencies of the sulphate ions are presented in the temperature region from -150 to 230°C covering all the phase transitions. The total integrated areas of the 1, 2 and 4 modes show an anomalous increase across the phase transitions. The frequencies of the symmetric stretching (1) and symmetric bending (2) modes do not show any changes at the phase transitions, but the width of the 2 mode shows changes across the phase transitions. A small increase in the linewidth of the 2 mode observed in the incommensurate phase is attributed to the influence of the incommensurate modulation wave. A DSC thermogram showed endothermic peaks during heating at all the phase transitions. The IR spectrum recorded at room temperature showed the expected Au and Bu internal modes.

Homoagmatine from Lathyrus sativus seedlings

A new guanidino amine has been isolated from Lathyrus sativus seedlings and chararterized as homoagmatine on the basis of various physico-chemical criteria including IR spectrum and comparison with that chemically synthesized. Homoagmatine is accumulated in the embryos axis while its precursor, homoarginine, is lost from the cotyledons. However, there was a progressive increase in homoarginine content of the embryo axis during development. Since the amine content of the whole seedlings corresponded to nearly 20–25 % of net decrease in homoarginine levels, it is concluded that the catabolism of homoarginine through homoagmatine represents a major pathway of metabolism of the arnino acid.

Infrared Spectroscopic Studies to Understand the Effect of Drugs at Molecular Level

In the recent past, there have been enormous efforts to understand effect of drugs on human body. Prior to understand the effect of drugs on human body most of the experiments are carried out on cells or model organisms. Here we present our study on the effect of chemotherapeutic drugs on cancer cells and the acetaminophen (APAP) induced hepatotoxicity in mouse model. Histone deacetylase inhibitors (HDIs) have attracted attention as potential drug molecules for the treatment of cancer. These are the chemotherapeutic drugs which have indirect mechanistic action against cancer cells via acting against histone deacetylases (HDAC). It has been known that different HDAC enzymes are over-expressed in various types of cancers for example; HDAC1 is over expressed in prostate, gastric and breast carcinomas. Therefore, in order to optimise chemotherapy, it is important to determine the efficacy of various classes of HDAC inhibitor drugs against variety of over-expressed HDAC enzymes. In the present study, FTIR microspectroscopy has been employed to predict the acetylation and propionylation brought in by HDIs. The liver plays an important role in cellular metabolism and is highly susceptible to drug toxicity. APAP which is an analgesic and antipyretic drug is extensively used for therapeutic purposes and has become the most common cause of acute liver failure (ALF). In the current study, we have focused to understand APAP induced hepatotoxicity using FTIR microspectroscopy. In the IR spectrum the bands corresponding to glycogen, ester group and were found to be suitable markers to predict liver injury at early time point (0.5hr) due to APAP both in tissue and serum in comparison to standard biochemical assays. Our studies show the potential of FTIR spectroscopy as a rapid, sensitive and non invasive detection technique for future clinical diagnosis.

Reduced graphene oxide-supported nickel oxide catalyst with improved CO tolerance for formic acid electrooxidation

The superior catalytic activity along with improved CO tolerance for formic acid electro-oxidation has been demonstrated on a NiO-decorated reduced graphene oxide (rGO) catalyst. The cyclic voltammetry response of rGO-NiO/Pt catalyst elucidates improved CO tolerance and follows direct oxidation pathway. It is probably due to the beneficial effect of residual oxygen groups on rGO support which is supported by FT-IR spectrum. A strong interaction of rGO support with NiO nanoparticles facilitates the removal of CO from the catalyst surface. The chronoamperometric response indicates a higher catalytic activity and stability of rGO-NiO/Pt catalyst than the NiO/Pt and unmodified Pt electrode catalyst for a prolonged time of continuous oxidation of formic acid. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

On the conformation of cyclohexane-1,4-dione and its derivatives—I : Infrared and raman spectra of cyclohexane 1,4-dione and infrared spectrum of its octadeutero analogue

Raman spectra of cyclohexane 1,4-dione (I), in chloroform, benzene and water solutions have been recorded. Temperature effect on the spectrum has been studied. The IR spectra of I and its octadeutero analogue in the solid state have also been studied. The spectra have been found on the basis of selection rules applicable for Raman and IR spectra, to be consistent with a single conformer of C2 symmetry. Plausible causes of conformational preference have been discussed.

Infrared spectrum of formamide in the solid phase

Infrared spectra of solid formamide are reported as a function of temperature. Solid formamide samples were prepared at 30 K and then annealed to higher temperatures (300 K) with infrared transmission spectra being recorded over the entire temperature range. The NH2 vibrations of the formamide molecule were found to be particularly very sensitive to temperature change. The IR spectra revealed a phase change occurring in solid formamide between 155 and 165 K. Spectral changes observed above and below the phase transition may be attributed to a rearrangement between formamide dimers and the formation of polymers is proposed at higher temperatures.

Spectroscopic investigations of manganese ions in microwave-prepared NaPO3-PbO glasses

The EPR spectra of microwave-prepared 70NaPO(3):30PbO glasses containing different weight percentages of manganese ions have been studied. The EPR spectra exhibit a well-resolved hyperfine pattern at g(eff) approximate to 2.0. Optical absorption, fluorescent emission and excitation spectra of the glasses have been examined. The absorption spectrum exhibits a peak near 500 nm and this has been attributed to the spin-allowed E-5(g) --> T-5(2g) transition of Mn3+ ions. The emission spectrum shows a band at 595 nm which has been assigned to the T-4(1g)(G) --> (6)A(1g)(S) spin-forbidden transition of Mn2+ ions in octahedral coordination. Concentration quenching of fluorescence was found to occur above 0.75 wt% of Mn2+ ions. The excitation spectra exhibit four bands characteristic of Mn2+ ions in octahedral coordination. From the observed band positions of the excitation spectra, the crystal field parameter D-q and the Racah interelectronic repulsion parameters, B and C have been calculated. A structural model is proposed based on the IR, Raman and MASNMR studies according to which Mn2+ ions are likely to occupy sites similar to Na+ ions in these glasses.

Oxovanadium(IV)-based near-IR PDT agents: design to biological evaluation

An oxovanadium(IV) complex of dipyridophenazine, as a potent metal-based PDT agent, shows efficient DNA photocleavage activity at near-IR region and high photocytotoxicity in both UV-A and visible light in HeLa cells.

Raman Spectrum of Cyclopropane

The Raman spectrum of cyclopropane is of great interest in view of the fact that it is the simplest of the cyclic hydrocarbons, and also from the point of view of the structure of the cyclopropane molecule. I have investigated this substance both in the liquid and vapour states and have obtained the following results :

Simultaneous display of spectrum and image in a single plane, and the realization of a lensless coherent optical processor

A novel method, designated the holographic spectrum reconstruction (HSR) method, is proposed for achieving simultaneous display of the spectrum and image of an object in a single plane. A study of the scaling behaviour of both the spectrum and the image has been carried out and based on this study, it is demonstrated that a lensless coherent optical processor can be realized.

Renormalization of the phonon spectrum in semiconducting single-walled carbon nanotubes studied by Raman spectroscopy

In situ Raman experiments together with transport measurements have been carried out in single-walled carbon nanotubes as a function of electrochemical top gate voltage (Vg). We have used the green laser (EL=2.41 eV), where the semiconducting nanotubes of diameter ~1.4 nm are in resonance condition. In semiconducting nanotubes, the G−- and G+-mode frequencies increase by ~10 cm−1 for hole doping, the frequency shift of the G− mode is larger compared to the G+ mode at the same gate voltage. However, for electron doping the shifts are much smaller: G− upshifts by only ~2 cm−1 whereas the G+ does not shift. The transport measurements are used to quantify the Fermi-energy shift (EF) as a function of the gate voltage. The electron-hole asymmetry in G− and G+ modes is quantitatively explained using nonadiabatic effects together with lattice relaxation contribution. The electron-phonon coupling matrix elements of transverse-optic (G−) and longitudinal-optic (G+) modes explain why the G− mode is more blueshifted compared to the G+ mode at the same Vg. The D and 2D bands have different doping dependence compared to the G+ and G− bands. There is a large downshift in the frequency of the 2D band (~18 cm−1) and D (~10 cm−1) band for electron doping, whereas the 2D band remains constant for the hole doping but D upshifts by ~8 cm−1. The doping dependence of the overtone of the G bands (2G bands) shows behavior similar to the dependence of the G+ and G− bands.

The rα structure, chemical shift anisotropy, and the abnormal orientation of methyldichlorophosphine from the NMR spectrum

NMR studies of methyldichlorophosphine have been undertaken in the nematic phase of mixed liquid crystals of opposite diamagnetic anisotropies. The rα structure is derived. The proton chemical-shift anisotropy has been determined from the studies without the use of a reference compound and without a change of experimental conditions. It is shown that the molecule orients in the liquid crystal with positive diamagnetic anisotropy in such a way that the C3 symmetry axis of the CH3P moiety is preferentially aligned perpendicular to the direction of the magnetic field, unlike other similar systems. This is interpreted in terms of the formation of a weak solvent-solute molecular complex. The heteronuclear indirect spin-spin coupling constants are determined. The sign of the two-bond JPH is found to be positive.

NMR spectrum of pyridine-N-oxide in a thermotropic nematic phase

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Nuclear magnetic resonance spectra of oriented bicyclic systems containing heteroatom(s):the spectrum of 2-thiocoumarin

From the proton nmr studies of 2-thiocoumarin and coumarin, it is concluded that the relative interproton distances in the two oxygen heteroatom bicyclic systems are similar. The values for the phenyl ring protons do not deviate significantly from the regular hexagonal geometry, unlike bicyclic systems with nitrogens as the heteroatoms, such as diazanaphthalenes. Larger values of the indirect spin-spin couplings within the protons of the ring containing the oxygen heteroatom, compared to the values between the ortho protons in the phenyl rings in coumarin and 2-thiocoumarin, correspond to the olefinic nature of these protons. This is in contrast to results for the nitrogen heterocycles where both the rings are aromatic.