Dhannia, T; Dr.Jayalekshmi, S(Cochin University of Science and Technology, January 30, 2012)
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Abstract:
This thesis Entitled INVESTIGATIONS ON THE STRUCTURAL, OPTICAL AND MAGNETIC PROPERTIES OF NANOSTRUCTURED CERIUM OXIDE IN PURE AND DOPED FORMS AND ITS POLYMER NANOCOMPOSITES.Synthesis and processing of nanomatelials and nanostmctures are the essential aspects of nanotechnology. Studies on new physical properties and
applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology,crystal structure and chemical composition.Recently, several methods have been developed to prepare pure and doped CeO2 powder, including wet chemical synthesis, thermal hydrolysis, flux method, hydrothermal synthesis, gas condensation method, microwave technique etc. In all these, some special reaction conditions, such as high temperature, high pressure, capping agents, expensive or toxic solvents etc. have been involved.Another hi gh-li ght of the present work is room temperature ferromagnetism in cerium oxdie thin films deposited by spray pyrolysis technique.The observation of self trapped exciton mediated PL in ceria nanocrystals is another important outcome of the present study. STE mediated mechanism has been proposed for CeO2 nanocrystals based on the dependence of PL intensity on the annealing temperature. It would be interesting to extent these investigations to the doped forms of cerium oxide and cerium oxide thin
films to get deeper Insight into STE mechanism.Due to time constraints detailed investigations could not be canied out on the preparation and properties of free standing films of polymer/ceria
nanocomposites. It has been observed that good quality free standing films of PVDF/ceria, PS/C61‘l8, PMMA/ceria can be obtained using solution casting technique. These polymer nanocomposite films show high dielectric constant around 20 and offer prospects of applications as gate electrodes in metal-oxide semiconductor devices.
Description:
Division for Research in Advanced Materials,
Department of Physics,
Cochin University of Science and Technology
Sajan, P; Dr. M. Junaid Bushiri(Cochin University of Science and Technology, June 5, 2016)
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Abstract:
The research on nanocrystalline materials have been of great interest for
more than 20 years due to its fundamental properties as well as development of
technology based on it. Non-toxic semiconducting nanocrystals are important
materials with wide range of applications in the areas of biotechnology, medicine,
bio-optics and for the fabrication light emitting and harvesting devices. Majority of
the II-VI semiconductors possess wide band gap along with high iconicity and are
important materials for optoelectronic devices operating under the UV excitation
sources. Among the II-VI semiconductors, ZnS is a material with good optical
transmission in the visible region with large exciton binding energy of about 40
meV. ZnS usually crystallizes in cubic form which is zinc blende or sphalerite and
its hexagonal form is in wurtzite phase. The cubic sphalerite phase of ZnS has a
band gap of 3.68 eV whereas the hexagonal (wurtzite) phase has a band gap of 3.77
eV. Moreover, ZnS is a good host lattice phosphor for photonic applications and
electroluminescent devices because of its wide band gap.
The present thesis deals with the synthesis and photoluminescence studies
of micro and nanostructured ZnS by hydrothermal and solvo-hydrothermal method.
Thesis is also focused on bioimaging application of these materials.