Annual Report 1999-2000

Autonomous Institutions

Indian Association for the Cultivation of Science, Calcutta

The Indian Association for the Cultivation of Science, established in 1876, has been continuing its efforts for excellence in scientific research. The various scientific activities and achievements during the year are summarised below:

Materials Science

A series of Lead based alloys (Sn, Sb,), ball milled ceramic V2O5 and Ni3Al alloys, ferroelectric Ammonium Sulphate have been studied by XRD, TEM and etch technique respectively. Martinsitic alloys Fe23Ni3.8,3.6, 3.3 have been studied by Rietveld's X-ray profile analysis method. Structural studies of 1-(Ethoxy methyl) -6-(phenyl Selenyl)-5-ethyl uracil and 9-®-[6-® Hydroxymethyl-1-oxa-4-thia-yello-hexam-2-yl] hypooxanthine have been performed. Nonlinear crystals LAHCl and LAHBr have been grown and their microhardness and Youngs modulus have been studied. Some La based oxides with double perovskite have been prepared by Sol gel method, which show metal-insulator transition below 100K and large magnetoresistance under magnetic field 1 tesla. The electrical conductivity of HCl doped (PANI) in PVA have been investigated in the range 300 to 80 K and in the frequency range 1KHz to1 MHz. Magnetic, optical and magneto-optical studies of PrX, NdX (X= P, As, Sb, Bi) have been studied from the first principle. Thin films of CuInS2, GaN, BN, Al/C-BNSi, Au/C-BN/InP, Cu(In, Ga)Se2 and Cu(In,S)Se2 have been successfully prepared by various methods and characterised. Preparation and characterisation of Diamond and diamond like films have been performed. Growth of nanostructured ZnSxSe1-x layers on GaAs has also been studied. The result shows that the theory leads to a universal time arrow at the quantum level. Multiphoton dissociation and population transfer in simple molecules in laser field has been studied theoretically.

Solid State Physics

Nature of magnetism and anisotropic exchange effects in Cu-Mn linear chain system was investigated by EPR experiments. Computer simulation of EPR spectra of Cu(II) Mn(II) ions in gel matrices was initiated. CsCdCl3 doped with trivalent rare earth ions as well as transition metal ions Co2+ and Cr3+ were prepared for spectroscopical and Zeeman studies. Effect of different hosts on the electronic and nuclear levels of RE ions were studied. New insight on the genesis of ores of minerals was found from Mössbauer and magnetic studies. Giant magnetoresistance in rare-earth manganates and high Tc superconductivity in non-conventional multicomponent oxide glass-ceramics were observed. A new kind of rare-earth doped transparent oxide glass suitable for making optical fibres was prepared and new results were obtained from the dielectric relaxation studies of some nanoparticle dispersed transition metal oxide glasses. Macromolecular Direct method was applied for improving the quality of electron density map by density modification technique to a protein, pseudoazurin having –6000 non-II in the unit cell. Crystal structures of two heterocyclic organic compounds with biological importance have been established. Study of ultrasonic velocity and attenuation in Bi-phosphate glasses of different compositions followed by theoretical analysis of the data considering the combined effect of relaxation, anharmonicity and frozen-in fluctuation has been completed. A scaling formalism for the conductivity spectra of glasses was developed which gives a new insight into the relaxation dynamics of charge carriers in glasses. From the study of the transient responses of light-emitting devices based on different organic semiconductors, different parameters for barrier modification and relaxation of accumulated charge carriers in the devices have been found.

Spectroscopy

Studies of the atoms, ions, small molecules of astrophysical, chemical and spectroscopic interest, spectroscopy of foreign atoms under liquid Helium temperature and effect of correlation in many electron systems, and of highly stripped ions with special emphasis on high temperature plasma diagnostics and quantum mechanical study of photo-biological systems have been made. Theoretical prediction of lasing without population inversion has been made. A model of non-local quantum electrodynamics has been developed and laser assisted multiphoton processes in gases have been studied. For studying the charge transfer in Nitrogen and other noble gas ion – atom systems the methodology of Translational Energy Spectroscopy has been improved. Monte – Carlo simulation studies of organic light emitting diodes and studies on ultra structures, optical properties and non-linear optics by Surface Plasmmon techniques and normal coordinate analysis of few substituted pyridine molecules have been carried out. Surface Enhanced Raman spectroscopic studies of different hetero-aromatic molecules in silver sol, and an analytical study of REPs of different modes of vibrations, mainly, in double molecules have been made for getting some information regarding excited state molecular configuration. Excited state photodynamics and various aspects of ESPT of some organic molecular systems on the basis of experiments and QM calculations, synthesis and photophysical/ photoconductive studies of some novel organic electron donor and acceptor systems and some bichromophoric systems having their donor and acceptor linked by polymethylene type of spacers of different length and numbers, have been studied, both, by steady state and time resolved spectroscopy. Energy transfer between molecules and other spectroscopic features of molecules organised in Langmuir Blodgett films and in miscelles, studies on molecular electronics have been made. Further, fish freshness biosensor has been developed in the department. An experimental investigation of different physical properties of liquid crystals and spectroscopic, as well as, photoconductive properties of organic/organometallic materials have been carried out during the period under consideration.

Theoretical Physics

Atomic and Molecular Collision processes have been impressively enriched for works on single (double) ionization processes in ion atom collisions and also Positronium formation in Positron-atom scattering using elaborate methods. Availability of Antihydrogen at CERN and Fermilab provides impetus to theoreticians to investigate the properties of antimatter. Impressive works have been carried out in various branches of Condensed Mater Physics e.g. in the theory of phase transitions, in the field of turbulence and pattern formation on inhomogeneous substrates. Heavy hadrons have been studied. Flavour changing radiative beta decays have also been investigated. In quantum chromodynamics, effect of gluon condensation has been incorporated. Investigation has been carried out on AGN neutrino fluxes and muon energy spectrum. Environmental Science and Biodiversity have been studied. Investigations have also been carried out in Bioinformatics and in protein folding.

Energy Research Unit

The activities concentrated on materials and fabrication technology for silicon based thin film solar cells. In the area of multijunction a-Si solar cell the development of technology has reached the level of commercialisation. Due to this reason, MNES and DST have jointly sponsored a major project for the setting up of a prototype plant for production of this type of solar cell. Microcrystalline Si:H based materials have been developed for improvement in conversion efficiency. Progress has been made towards development of materials for polycrystalline silicon solar cells by using RFPECVD method. Computer modelling has been done to investigate the effects of using microcrystalline p-layer as the windoe layer of a-Si solar cells. Under a project funded by DST, a plasma diagnostic facility has been set-up. Work has been initiated on silane plasma, which is relevant to a-Si solar cell fabrication. A new Indo-French (IFCPAR) project has been sanctioned for the fabrication of stable solar cells based on new PECVD process.

MLS Processor’s Unit

Work on the synthesis of nanocomposites has been pursued. Metals as well as oxides in nanocrystalline form have been grown within an amorphous medium using a soft chemical route. The interface of the nanoparticles of Cu2O shows an enhanced electrical conductivity as compared to that of the bulk gel containing variable valence ions. AC conductivity of iron – silica and copper – silica nanocomposites exhibit a variable range hopping and a quantum mechanical tunneling mechanism respectively. Core-shell structure of nanometre-sized Fe-Fe3O4 particles has been studied by detailed magnetization measurements.

Biological Chemistry

Inhibitor of specific antigen-antibody reactions, ligand for immunoadsorbents, starting material for artificial antigens, several di- and trisaccharide derivatives related to bacterial antigens of Shigella dysenteriae types 3 and 4 and S. boydii type 5 have been synthesised. Epidemiological study on the prevalence of ascariasis in rural population has been made to test the diagnostic potentiality of anti-ascaris IgG4 assay. Purification and molecular characterization of two blood group nonspecific lectins from plant and vertebrate origins have been initiated with a view to studying immunomodulatory role of lectins. Chitosan beads prepared from shellfish have successfully been employed as chelating agent to remove heavy metals e.g., Cr6+, Cu2+, Ni2+ from waste water. Glyceraldehyde-3-phosphate dehydrogenase from EAC cells has been purified and characterized. An essential lysine residue has been identified at the active site of the enzyme. Nonprotein amino acids (e.g. a -amino isobutyric acid and a -aminoacids) have been utilized in the design of new peptide structures. Synthesis of judicially chosen amino acid sequences that will fold into compact secondary and super-secondary structures has been done.

Inorganic Chemistry

Significant contributions include sugar vanadates, mixed valence vanadium species, stabilized azo anion radical systems, novel cadmium clusters, multinuclear heterometallic species with macrocyclic and acyclic ligand systems, double stranded helicates with square planar metal coordination, novel Cu(I) species exhibiting delayed fluorescence; metal promoted ligand oxidation, aromatic ring amination, oxidative dimerisation of primary amine and some other unusual organic reactions; activation of C-N single bond, thermally induced nitro-nitrito linkage isomerisation; kinetic and NMR studies on ring opening, substitution and isomerisation reactions of coordinated Pt(II) and Pd(II) systems.

Organic Chemistry

The continuing research efforts have unfolded novel methods of carbon-carbon bond formations mediated by transition metal induced radical reactions, metal mediated selective bond formations, microwave assisted processes and ring fragmentation technologies. These have been successfully applied for the total synthesis of some bioactive sesquiterpenes and related compounds containing unusual carbo- and heterocyclic structures. A number of nitrogen and sulfur heterocyclic systems have been synthesised employing transition metal induced cyclisations and these will be of use for studying structure-activity relationships.

Physical Chemistry

Solvation dynamics of DCM dye and isomerisation of merocyanin in microemulsion and electron transfer in micelles have been studied using picosecond emission spectroscopy. Excited state proton transfer dynamics has been analysed in two new O-hydrogen Schiff bases by nanosecond spectroscopy. Kramer’s theory for activated process has been generalised for non-equilibrium open systems. A size consistent coupled cluster theory valid over a wide range of molecular geometry has been formulated and applied to di and tri atomic molecules. The theory uses a reference function that spans the complete active space.

Polymer Science

Studies on the morphology of the interpenetrating composite of polypyrrole (Ppy) and poly(vinyl)acetate (PVA) using SEM on cryofracture surface reveal the formation of Ppy particles inside swollen PVA films. Work has been initiated to develop a suitable procedure for the atom transfer radical polymerisation for water-soluble monomers. Studies are being carried out to understand further polymer crystallisation and polymer gelation phenomena. A number of new thermoreversible conducting gels of polyaniline and polythiophene have been obtained.