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Trieste, Italy

Anbarasan P.M.,Periyar University | Senthil Kumar P.,Periyar University | Vasudevan K.,Periyar University | Moorthy Babu S.,Anna University | Aroulmoji V.,Protos Research Institute
Acta Physica Polonica A | Year: 2011

The geometries, electronic structures, polarizabilities, and hyperpolarizabilities of organic dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile were studied based on density functional theory using the hybrid functional B3LYP. Ultraviolet-visible spectra were investigated by time dependent density functional theory. The features of electronic absorption spectra in the visible and near-UV regions were assigned based on time dependent density functional theory calculations. The absorption bands are assigned to π → π* transitions. Calculated results suggest that the three lowest energy excited states of 3,4-pyridinedicarbonitrile, 3- aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile are due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile is due to an electron injection process from excited dyes to the semiconductor's conduction band. The role of amide and methyl groups in phthalonitrile in geometries, electronic structures, and spectral properties were analyzed in a comparative study of 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile for the improvement of dye sensitized solar cells. Source

Chinna Babu P.,Annamalai University | Sundaraganesan N.,Annamalai University | Sudha S.,Annamalai University | Aroulmoji V.,Advanced Research Center for Health | Murano E.,Protos Research Institute
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

The solid phase FTIR and FT-Raman spectra of Irinotecan have been recorded in the regions 400-4000 and 50-4000 cm-1, respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d) as basis set. The vibrational frequencies were calculated for Irinotecan by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared spectrum was also simulated from the calculated intensities. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations. © 2012 Elsevier B.V. All rights reserved. Source

Anbarasan P.M.,Periyar University | Senthilkumar P.,Periyar University | Manimegalai S.,Periyar University | Geetha M.,Periyar University | And 5 more authors.
Silicon | Year: 2010

In this work, a series of nanocrystalline silicon films were studied with different microstructural tools to elucidate the film microstructure at different stages of growth. Thin Si films, with a series of multilayers, were deposited by radio frequency glow discharge using Plasma Enhanced Chemical Vapour Deposition (PECVD) in silane gas (SiH4) highly diluted by hydrogen. Different nanostructured films were prepared by systematically varying gas flow ratios (R = 1/1, 1/5, 1/7.5, 1/10, 1/15, 1/20) for films having different thicknesses. By changing the structure of the material, going from pure amorphous to nanocrystalline silicon, it is possible to obtain a variation in optical gap using the same material. In these structures, layers with different individual optical gaps are stacked together in order to cover as much of the solar spectrum as possible. The nanostructures of the silicon thin films were studied using FTIR, RS, PL, XRD, AFM, SEM, TEM and HRTEM. The results were correlated for conglomerate surface, grain surface. Some theoretical calculations were used for designing the overall stack geometry and for interpretation of characterization. These agree well with experimental observation. © Springer Science+Business Media B.V. 2010. Source

Grassi M.,University of Trieste | Cavallaro G.,University of Palermo | Scire S.,University of Palermo | Scaggiante B.,University of Trieste | And 7 more authors.
Current Signal Transduction Therapy | Year: 2010

The limited efficacy of current therapeutic approaches for a number of socially relevant human diseases has required the exploration of alternative and more effective therapeutic strategies. In the last three decades, nucleic acid based drugs (NABDs) have emerged as an attractive and novel alternative with great therapeutic potential. NABDs which include antisense oligonucleotides, decoys, aptamers, triple helix forming oligonucleotides, DNAzymes, Ribozymes and small interfering RNAs, have been shown to be able to efficiently counteract pathological gene expression in many different experimental systems. Despite their broad potential applicability, NABD use in the clinic is limited by the lack of optimal delivery systems. Due to their hydrophilic nature, NABDs cannot efficiently cross cellular membrane for which appropriate carriers are needed. Moreover, their instability in serum requires a proper protection to prevent a fast degradation which would invariably lead to the abrogation of any significant therapeutic effect. In this work we will review the strategies currently proposed to circumvent NABD delivery problems. Although the NABD delivery issue can and should be optimized to bring NABD closer to the clinic, the encouraging results displayed so far in experimental models fully justify further efforts both in terms of investments and scientific work. Source

Pescosolido L.,University of Rome La Sapienza | Pescosolido L.,University Utrecht | Feruglio L.,Protos Research Institute | Feruglio L.,University of Trieste | And 8 more authors.
Soft Matter | Year: 2012

The importance of Interpenetrating Polymer Networks (IPNs) in biomedical and pharmaceutical fields is continuously growing because of their mechanical and drug carrier tailoring opportunities. This paper deals with the physico-chemical characterization of an IPN hydrogel based on calcium-alginate and a dextran methacrylate derivative. The attention is focused on the determination of IPN mesh size distribution. For this purpose, two different approaches were applied, namely using a combination of rheological and low field NMR characterization, and cryoporosimetry. Appropriate mathematical models were developed for the interpretation of the experimental data. Both approaches led to a mono-modal mesh size distribution spanning the same size range but characterized by different mean values (25 nm, Rheo-NMR; 44 nm, cryoporosimetry). This is probably due to mesh widening upon water freezing. Moreover, release experiments of a model protein - myoglobin - from the IPN were performed and the obtained data were combined with the results of the two above mentioned approaches. Release tests yielded an estimation of the mean mesh size that is closer to that obtained according to the rheology-NMR approach than that resulting from cryoporosimetry measurements. © 2012 The Royal Society of Chemistry. Source

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