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71.
S. Ramasamy D. J. Smith P. Thangadurai K. Ravichandran T. Prakash K. PAdmaprasad V. Sabarinathan 《Pramana》2005,65(5):881-891
The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from
DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline
materials such as PbF2, Mn2+-doped PbF2, Sn-doped In2O3 (ITO), ZnO, Al2O3, Ag2O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be
presented in this paper. In solid-state207Pb NMR on PbF2 a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during
the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease
in grain size. Presence of electronic centres in nanocrystalline PbF2 is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al2O3 was prepared and56Fe ions were implanted. After implantation segregation of56Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating
on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O2 atmosphere. The growth of ITO under O2 atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material
will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied 相似文献
72.
G. S. Lekshmi Tamilselvi Ramasamy Olha Bazaka Igor Levchenko Kateryna Bazaka Raji Govindan Mohandas Mandhakini 《Molecules (Basel, Switzerland)》2022,27(18)
Scaling up the production of functional reduced graphene oxide (rGO) and its composites requires the use of low-cost, simple, and sustainable synthesis methods, and renewable feedstocks. In this study, silver oxide-decorated rGO (AgxO−rGO) composites were prepared by open-air combustion of mustard oil, essential oil-containing cooking oil commercially produced from the seeds of Brassica juncea. Silver oxide (AgxO) nanoparticles (NPs) were synthesized using Coleus aromaticus leaf extract as a reducing agent. Formation of mustard seed rGO and AgxO NPs was confirmed by UV-visible characteristic peaks at 258 nm and 444 nm, respectively. rGO had a flake-like morphology and a crystalline structure, with Raman spectra showing clear D and G bands with an ID/IG ratio of 0.992, confirming the fewer defects in the as-prepared mustard oil-derived rGO (M−rGO). The rGO-AgxO composite showed a degradation efficiency of 81.9% with a rate constant k−1 of 0.9506 min−1 for the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid (known as the azo dye Congo Red) in an aqueous solution under visible light irradiation. The composite also showed some antimicrobial activity against Klebsilla pneomoniae, Escherichia coli, and Staphylococcus aureus bacterial cells, with inhibition zones of ~15, 18, and 14 mm, respectively, for a concentration of 300 µg/mL. At 600 µg/mL concentration, the composite also showed moderate scavenging activity for 2,2-diphenyl-1-picrylhydrazyl of ~30.6%, with significantly lower activities measured for AgxO (at ~18.1%) and rGO (~8%) when compared to control. 相似文献
73.
Ramasamy Ramaraj 《Journal of Chemical Sciences》2006,118(6):593-600
Nanotechnology has become one of the most exciting frontier fields in analytical chemistry. The huge interest in nanomaterials,
for example in chemical sensors and catalysis, is driven by their many desirable properties. Although metal is a poor catalyst
in bulk form, nanometre-sized particles can exhibit excellent catalytic activity due to their relative high surface area-to-volume
ratio and their interface-dominated properties, which significantly differ from those of the bulk material. The integration
of metal nanoparticles into thin film of permselective membrane is particularly important for various applications, for example
in biological sensing and in electrocatalysis. We have already established different techniques to design permselective membrane-coated
chemically modified electrodes with incorporated redox molecules for electrocatalytic, electrochromic and sensor applications.
Recently, we have prepared nanostructured platinum and copper (represented Mnano, M = Pt and Cu) modified GC/Nafion electrodes (GC/Nf/Mnano) and characterized by using AFM, XPS, XRD and electrochemical techniques. The nanostructured Mnano modified electrodes were utilized for efficient electrocatalytic selective oxidation of neurotransmitter molecules in the
presence of interfering species such as ascorbic acid (AA) and uric acid (UA). It has been also shown that the modified electrodes
could be used as sensors for the detection of submicromolar concentrations of biomolecules with practical applications to
real samples such as blood plasma and dopamine hydrochloride injection solution. The GC/Cunano electrode has been used for catalytic reduction of oxygen. 相似文献
74.
The infrared and Raman spectra of crystalline samples of NdP5O14, NaNdP4O12 and KNdP4O12 are recorded. The spectra are analysed on the basis of vibrations of P=O, P-O, PO2 and P-O-P groups. The P4O
12
4−
ion has cyclic structures both in NaNdP4O12 and KNdP4O12 crystals. It has been inferred that the P-O-P bridges are stronger in metaphosphates. 相似文献
75.
Mallayan Palaniandavar Marappan Velusamy Ramasamy Mayilmurugan 《Journal of Chemical Sciences》2006,118(6):601-610
Catechol 1,2-dioxygenase (CTD) and protocatechuate 3,4-dioxygenase (PCD) are bacterial non-heme iron enzymes, which catalyse
the oxidative cleavage of catechols tocis, cis-muconic acids with the incorporation of molecular oxygen via a mechanism involving a high-spin ferric centre. The iron(III)
complexes of tripodal phenolate ligands containing N3O and N2O2 donor sets represent the metal binding region of the iron proteins. In our laboratory iron(III) complexes of mono- and bisphenolate
ligands have been studied successfully as structural and functional models for the intradiol-cleaving catechol dioxygenase
enzymes. The single crystal X-ray crystal structures of four of the complexes have been determined. One of thebis-phenolato complexes contains a FeN2O2Cl chromophore with a novel trigonal bipyramidal coordination geometry. The Fe-O-C bond angle of 136.1‡ observed for one of
the iron(III) complex of a monophenolate ligand is very similar to that in the enzymes. The importance of the nearby sterically
demanding coordinated -NMe2 group has been established and implies similar stereochemical constraints from the other ligated amino acid moieties in the
3,4-PCD enzymes, the enzyme activity of which is traced to the difference in the equatorial and axial Fe-O(tyrosinate) bonds
(Fe-O-C, 133, 148‡). The nature of heterocyclic rings of the ligands and the methyl substituents on them regulate the electronic
spectral features, FeIII/FeII redox potentials and catechol cleavage activity of the complexes. Upon interacting with catecholate anions, two catecholate
to iron(III) charge transfer bands appear and the low energy band is similar to that of catechol dioxygenase-substrate complex.
Four of the complexes catalyze the oxidative cleavage of H2DBC by molecular oxygen to yield intradiol cleavage products. Remarkably, the more basic N-methylimidazole ring in one of
the complexes facilitates the rate-determining productreleasing phase of the catalytic reaction. The present study provides
support to the novel substrate activation mechanism proposed for the intradiol-cleavage enzymes. 相似文献
76.
Chellappan Shobana Basuvannan Rangasamy Subramani Surendran Ramakrishnan Kalai Selvan Mathan Ramesh 《Journal of Cluster Science》2018,29(2):267-279
Biosynthesis of silver nanoparticles has received considerable attention due to their cost-effective, eco-friendly and medicinal values. In this study, silver nanoparticles (Ag NPs) were synthesised using the aqueous leaf extracts of Piper nigrum. TEM images revealed that the particle is spherical with 20–50 nm in size. Furthermore, to evaluate the toxicity of synthesized Ag NPs, fish Labeo rohita were exposed to two different concentrations (2.5 µg/L as the treatment I and 5 µg/L as treatment II) for 35 days, and antioxidant parameters and histology of gill, liver and kidney were examined. A biphasic response in the activity of glutathione S-transferases (GST) was observed in gill and liver of fish. GST activity in the kidney of fish was significantly increased when compared to control group. Glutathione reductase (GR) activity in organs/tissue of fish were found to be increased while peroxidase (POD) activity was significantly decreased. Histopathological changes such as hyperplasia, proliferation of epithelial cells and fusion of lamellae were observed in both the concentrations. In liver, necrosis, nuclear degeneration and dilation of sinusoids were observed. Subsequently, the representative effects of POD activity were assessed based on the Box–Behnken Equation, 3-D contour plot and ANOVA analysis through response surface methodology analysis. 相似文献
77.
78.
Krishnakumar V Ramasamy R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3112-3116
The molecular structure and vibrational spectra of cyanuric chloride have been investigated by density functional theory (DFT) using standard B3LYP/6-31G* and B3LYP/6-311+G** method and basis set combinations. The DFT force field transformed to natural internal coordinates was corrected by a well-established set of scale factors that were found to be transferable to the title compound. Both the calculated structural parameters and vibrational frequencies are in good agreement with the available experimental data. 相似文献
79.
Raman Spectroscopy and Fluorescence Photon Migration for Breast Cancer Diagnosis and Imaging 总被引:3,自引:0,他引:3
Ramasamy Manoharan Karen Shafer Lev Perelman Jun Wu Kun Chen Geurt Deinum Maryann Fitzmaurice Jonathan Myles Joseph Crowe Ramachandra R. Dasarl Michael S. Feld 《Photochemistry and photobiology》1998,67(1):15-22
We are developing optical methods based on near infra-red Raman spectroscopy and fluorescence photon migration for diagnosis and localization of breast cancer. We demonstrate the ability of Raman spectroscopy to classify accurately normal, benign and malignant breast tissues, an important step in developing Raman spectroscopic needle probes as a tool for improving the accuracy of needle biopsy. We also show that photon migration imaging can be used to localize accurately small fluorescent objects imbedded in a thick turbid medium with realistic optical properties, thus demonstrating the potential of this technique for optical imaging. 相似文献
80.
Krishnakumar V Ramasamy R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(11-12):2526-2532
The solid phase FT-IR and FT-Raman spectra of 4,5-dichloro-3-hydroxypyridazine have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The spectra were interpreted with the aid of normal coordinate analysis following a full structure optimization and force field calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G* and B3LYP/6-311+G** method and basis set combinations. The DFT force field transformed to natural internal coordinates was corrected by a well-established set of scale factors that were found to be transferable to the title compound. The IR and Raman spectra were predicted theoretically and compared with the experimental spectra. 相似文献