Degradation of nickel (86 MeV) ion irradiated polystyrene

Samples of polystyrene films were irradiated under vacuum at room temperature with ⁵⁸Ni⁷⁺ (86 MeV) ion with fluences ranging from 1 × 10¹¹ to 1 × 10¹³ ions cm⁻². Ion induced structural modifications were studied by means of atomic force microscopy atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visible absorption spectroscopy (UV-Vis) and Fourier transform infrared spectroscopy (FTIR) techniques. Atomic force microscopy shows that the root mean square (RMS) roughness of the irradiated polystyrene surface increases with the increment of ion fluence. XRD analysis reveals that in addition to the increase of amorphization of polymer with the increase of ion fluence there is also an increase of ordering (to a small extent) in some of the micro-domains. These results have further been supported by the study of optical and chemical analysis. The analysis of present study shows that the increase of full width at half maximum (FWHM) of first peak of XRD spectra, decrease of optical band gap and the formation of new alkyne group may be attributed to the increase of amorphization of polystyrene. Similarly, sharpening of second X-ray diffraction peak, decrease of Urbach’s energy and increase in the absorbance ratio of I₁₂₂₂/I₁₁₈₃ may be owed to the increase of ordering in some domains.     

Effect of rubbing load on nanoscale charging characteristics of human hair characterized by AFM based Kelvin probe

The manageability and feel of human hair is significantly affected by its surface charge. Understanding and developing ways to control charge build up is hence highly beneficial. Previous studies have looked at static charging characteristics of hair on a macroscale. In this study, static charging characteristics of hair are studied on the nanoscale with an AFM. Hair is charged by rubbing a control area on its surface with an AFM tip, to which a small voltage bias is applied. The resulting charge distribution is characterized by measuring the surface potential of the control area in situ with AFM based Kelvin probe microscopy. The rubbing load is progressively increased, and the effect of this increase on the charge build up is assessed. Virgin, damaged and conditioner treated hair samples are studied for a better understanding of charge build up and dissipation. Relevant mechanisms are discussed.     

Properties of phenoxyl radical of dehydrozingerone, a probable antioxidant

Free radical reactions of dehydrozingerone (DZ), a methoxy phenol, were studied at dfferent pHs with a variety of oxidants using nanosecond pulse radiolysis technique. Hydroxyl radical (OH) reaction with the phenolic form at pH 6 led mainly to the formation of an OH-adduct absorbing at 460 nm in addition to a minor oxidation product. On the other hand, at pH 10 with the deprotonated phenoxide ion, the only reaction observable was oxidation generating a phenoxyl radical absorbing at 360 nm. HPLC analysis indicated formation of two different products at pH 6 from addition and oxidation reactions, whereas at pH 10, only the oxidation product was detectable. Reactions of more specific secondary oxidizing radicals, N3√, Br√, Br⁻₂√ and Tl(II) with DZ gave rise to the phenoxyl radical over the entire pH range. DZ in the phenoxide ion form reacted with nitrogen dioxide and trichloromethyl peroxyl radicals with rate constants 6×10⁸ and 8.8×10⁸ dm³ mol⁻¹ s⁻¹ respectively leading to the phenoxyl radicals. The DZ phenoxyl radical reacted with trolox C (an analogue of -tocopherol) with a rate constant of 8.3×10⁷ dm³ mol⁻¹ s⁻¹. One electron reduction potential of the DZ phenoxyl radical at pH 6 was determined to be +1.1 V vs NHE using N3√/N⁻₃ as the standard couple.     

Effect of Molecular Interactions on Electron‐Transfer and Antioxidant Activity of Bis(alkanol)selenides: A Radiation Chemical Study

Understanding electron‐transfer processes is crucial for developing organoselenium compounds as antioxidants and anti‐inflammatory agents. To find new redox‐active selenium antioxidants, we have investigated one‐electron‐transfer reactions between hydroxyl (^.OH) radical and three bis(alkanol)selenides (SeROH) of varying alkyl chain length, using nanosecond pulse radiolysis. ^.OH radical reacts with SeROH to form radical adduct, which is converted primarily into a dimer radical cation (>Se∴Se<)⁺ and α‐{bis(hydroxyl alkyl)}‐selenomethine radical along with a minor quantity of an intramolecularly stabilized radical cation. Some of these radicals have been subsequently converted to their corresponding selenoxide, and formaldehyde. Estimated yield of these products showed alkyl chain length dependency and correlated well with their antioxidant ability. Quantum chemical calculations suggested that compounds that formed more stable (>Se∴Se<)⁺, produced higher selenoxide and lower formaldehyde. Comparing these results with those for sulfur analogues confirmed for the first time the distinctive role of selenium in making such compounds better antioxidants.     

Fluorescence spectroscopic studies on binding of a flavonoid antioxidant quercetin to serum albumins

Binding of quercetin to human serum albumin (HSA) was studied and the binding constant measured by following the red-shifted absorption spectrum of quercetin in the presence of HSA and the quenching of the intrinsic protein fluorescence in the presence of different concentrations of quercetin. Fluorescence lifetime measurements of HSA showed decrease in the average lifetimes indicating binding at a location, near the tryptophan moiety, and the possibility of fluorescence energy transfer between excited tryptophan and quercetin. Critical transfer distance (R _o ) was determined, from which the mean distance between tryptophan-214 in HSA and quercetin was calculated. The above studies were also carried out with bovine serum albumin (BSA).     

C-6 regioselective bromination of methyl indolyl-3-acetate

An efficient route to natural occurring methyl 6-bromoindolyl-3-acetate 1c from methyl indolyl-3-acetate 3 was achieved in 3 steps and 68% overall yield. Thus, in order to regioselectively brominate 3 at the C6-position, introduction of electron withdrawing substituents at N1 and C8 was affected to give intermediate 4 in 82% yield. Bromination of 4 with 8 equiv of bromine in CCl4 and washings with aqueous Na2SO3 gave 5 in 86% yield, which was N- and C-decarbomethoxylated by treatment with NaCN in DMSO, affording 1c in 97% yield. The regioselectivity of bromination was evidenced by NMR spectroscopy and X- ray diffraction analysis.     

Chromatographic and Spectrophotometric Studies in Selected Acacia Species

JPC – Journal of Planar Chromatography – Modern TLC - Phytochemical studies were carried out in different parts of three Acacia species viz. A. catechu, A. nilotica and A. leucophloea,...     

Approximate controllability of a non-autonomous differential equation

In this paper, we establish the approximate controllability results for a non-autonomous functional differential equation using the theory of linear evolution system, Schauder fixed point theorem, and by making use of resolvent operators. The results obtained in this paper, improve the existing ones in this direction, to a considerable extent. An example is also given to illustrate the abstract results.     

A new class of mixed ligand complexes bearing bisphenol and 1,10-Phenanthroline for antimicrobial and antioxidant activities: synthesis,spectral and electrochemical studies

Research on Chemical Intermediates - A new class of mixed ligand complexes, [M(L)(phen)2], using a bidentate bischlorophenol ligand H2L (2,2′-methylenebis(4-chlorophenol)) and phenanthroline...