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Studies on the photoluminescence, photoconductivity and photocatalytic properties of undoped and doped ZnO nanostructures
Full text linkThe thesis deals with an indepth understanding of the photoluminescence and photoconductivity properties of both undoped and doped hydrothermal and aqueous chemically grown ZnO nanostructures followed by the photocatalytic properties of Zn)-rGO binary and ZnO -Ag-rGo ternary hybridsResearch was conducted under the supervision of Prof. Durga Basak of the Solid State Physics division under SPS [School of Physical Sciences]Research was carried out under CSIR fellowship and gran
The Study Of The Physics Beyond The SM At The LHC In The Light Of Dark Matter Searches
Full text linkThe SM model of particle physics reigned for almost four decades showing excellent consistency of the Higgs Boson at the LHC bestow the last missing piece of the model. Noetheless, the SM is incomplete as a description of nature for it suffers from some serious drawbacks such as it cannot provide a valid dark matter candidate, it has no piece of neutrino mass. In this thesis, we consider some simple BSM extensions that can alleviate these problemsResearch was carried out under the supervision of Prof. Dilip Kumar Ghosh of the Theoretical Physics division under SPS [School of Physical Sciences
Some aspects of the phenomenology of supersymmetric theories and the Large Hadron Collider
Full text linkIn spite of its enormous success, the Standard Model (SM) of particle physics suffers
from a few drawbacks. For example, the SM cannot account for the observations of
neutrino mass and mixing and the existence of dark matter (DM). Supersymmetry
(SUSY) is capable of addressing these issues in an elegant manner. Nevertheless, the
non-observations of the superpartners to date has put stringent constraints on their
masses. In the light of this, in this thesis, we consider a U(1)R symmetric model where
the R-charges are identified with lepton numbers in such a way that one of the leftchiral
sneutrinos can acquire a large vacuum expectation value (vev) and can play the
role of a down type Higgs field. Models with U(1)R symmetry and Dirac gauginos are
well motivated since they can address the issues relating to the Higgs boson mass, DM and neutrino mass generation. Most importantly, the presence of Dirac gluinos can relax the bound on superpartner masses. We augment the model with a right handed neutrino superfield to have a small Dirac neutrino mass at the tree level with an order one neutrino Yukawa coupling f. We observe, that the Higgs boson mass receives an additional contribution at the tree level, proportional to f, which can ameliorate the Higgs naturalness problem when f ∼ O(1). In the context of a locally supersymmetric theory, R-symmetry is mildly broken by a non-zero gravitino mass. In such a scenario, neutrino Majorana masses can be
generated at the tree level as well as at the one loop level. In addition, for an order one f, we also obtain a very light bino-like neutralino with mass around a few hundred MeV. Such a light neutralino has important implications at the LHC as well as in the
cosmological sector. On the other hand, the small f(∼ 10−4) case is also interesting as we obtain a sterile neutrino with mass around a few keV which can be an excellent warm dark matter candidate. The model also fares very well when studied in conjunction with the latest LHC results pertaining to different decay modes of the Higgs boson.
Finally, an added advantage of this model is that it can conceive light top squarks. We also study some interesting and distinct signatures of these top squarks at the LHC.The research was conducted under the supervision of Prof. Sourov Ray of Theoretical Physics division under the SPS [School of Physical Sciences]The research was carried out under CSIR fellowshi
Study of magnetic and dielectric properties of 3d transition metal oxides
Full text linkTransition metal compounds present a unique class of solids with complex and diverse thermodynamic properties. 3d transition metal oxides exist with a great variety of crystal structures, which are reflected in the richness of their physical properties. The orbital states of 3d electrons are to a large extent responsible for the complex relationship between the electronic properties and crystal structure. This complexity and diversity are the indication of strong interplay between electronic, lattice, orbital and spin degrees of freedom. The magnetic ground states of these oxides depend strongly on the environment surrounding the transition metal and also on the exchange interaction pathways between two magnetic ions, which is often mediated through the 2p levels of oxygen. The thesis entitled “Study of magnetic and dielectric properties of 3d transition metal oxides” is devoted to the experimental investigations focusing the magnetic and electric properties of some exotic transition metal oxides with fascinating crystal structures. Where necessary, the X-ray photo-electron spectroscopy, temperature dependent XRD have also been studied to have a comprehensive understanding of the systems. In many cases experimental results are fitted to the existing theoretical models to clarify the analysis. All the results and analyses based on the investigations performed during this tenure have been included in this thesis along with the theoretical background and experimental methodologies.The research was carried out under the supervision of Prof. Subham Majumdar of Solid State Physics division under SPS [School of Physical Sciences]The research was conducted under IACS fellowshi
Electronic Structure and Magnetic Behaviour of Ultrathin Epitaxial Films and Nanostructures on Surfaces
Full text linkControlled fabrication of nanostructures and thin films on well defined substrate surfaces, their stability and exploration of new physical phenomena are important aspects not only for the development of future nanoscale devices but also for the advancement of basic physics research. Self-organized growth at surfaces is one of the most efficient and versatile methods for producing these structures as it offers control over size, shape and organization on the nanometer length scale. Atomic-scale thin films and nanostructures of materials show interesting and unusual behaviour in various physical properties. Molecular beam epitaxy (MBE) is the one of the most sophisticated single crystal thin film growth techniques. MBE provides contamination-free epitaxial nanostructure growth on substrate surfaces with extreme control under ultrahigh vacuum (UHV) environment. This thesis deals with epitaxial growth of nanostructures, mainly by molecular beam epitaxy (MBE), and associated diffusion phenomena, electronic structure, electronic transport and magnetic behaviour. Keeping the potential applications in mind and possible integration with silicon technology, all our investigations involve growth of nanostructures on silicon substrates. Various aspects of MBE-grown Ag and Co thin films and nanostructures on atomically clean silicon substrates have been investigated in the present thesis using in-situ surface science techniques involving microscopy and spectroscopy. This thesis also includes investigation of the diffusion phenomena in parallel nanostripes in n-type Si substrates which have been fabricated by implanting energetic ions from a focused ion beam (FIB) source.Research was carried out under the supervision of Prof. B N Dev of the Materials Science division under SMS [School of Materials Science]Research was conducted under DST grant and IACS fellowshi
Theoretical Study of Structure, Interaction and Dissociation of Van Der Waals Complexes
Full text linkThe present dissertation entitled “Theoretical study of structure, interaction and
dissociation of van der Waals complexes” is submitted to fulfill the requirements for the degree
of Doctor of Philosophy (Science) of Jadavpur University. The study has been done for the
investigation of spectroscopy, molecular properties, interaction, stability, potential energy
surface, and dissociation of weakly bound molecules and complexes having astrophysical,
atmospherical and biological interest using high-level theoretical methods. All the studies have
been done under the supervision of Professor Abhijit Kumar Das in the Department of
Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032,
India.
This thesis contains six chapters. Chapter I contains a brief review of the van der Waals
complexes appeared in astrophysical, atmospherical, interstellar media and biological systems.
The second chapter contains the role of computational science explaining the fundamental
review of the basic theoretical methods. Chapter III, IV & V deal with the rare-gas and halogen
gas containing weakly bound molecules and van der Waals complexes. The last Chapter,
Chapter VI contains the detailed theoretical analysis of the light cation dihydrogen and carbonyl
sulfide and acetylene containing van der Waals complexes using dispersion corrected
functionals. Most of the results incorporated in this thesis have been published in reputed
international journals, a list of which is given in the next section.The research was carried out under the supervision of Prof. A K Das of the Spectroscopy division under SPS [School of Physical Sciences]The research was carried out under IACS research grant and fellowshi
Relaxation dynamics in some composite polymer electrolytes
Full text linkThis thesis is devoted to study the relaxation dynamics in some composite polymer
electrolytes. The organization of the thesis is as follows
Chapter 1 of this thesis describes the literature review in the field of polymer
electrolytes and their composites. A brief introduction to polymer electrolytes and their
composites is presented and their exotic features are discussed. The thermodynamics
behind the dissolution of the salts in polymers, phase diagram and ionic species of
polymer electrolyte have been outlined briefly. Several theoretical models and concepts
used to explain and understand the ion dynamics are pointed out. It also includes
different models of ac and dc conduction in ion conducting polymer electrolytes and
their composites. Finally, it presents precise objectives of the present work.
In chapter 2 a brief description of the preparation technique and various experimental
methods used to characterize the polymer electrolytes and their composites
are presented. In the initial part of the chapter the structural characterization such as
x-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron
microscopy (TEM), field emission scanning electron microscopy (FESEM) and Fourier
transform infrared (FTIR) spectroscopy techniques are discussed. In the later part,
electrical characterization techniques used to study the ion dynamics are presented.
Chapter 3 deals with a comparative study of PEO based polymer electrolytes containing
different lithium salts. The structural investigations have been carried out using
XRD, DSC and FESEM. The dynamics of Li+ ions in these electrolytes has been investigated
using ac impedance spectroscopy. The conductivity and dielectric relaxation in
these electrolytes are studied, using the existing theories of the conductivity, modulus
and dielectric formalism.
In chapter 4 the effect of CdO nanoparticle on the structure and relaxation mechanism
of PEO-LiI nanocomposite electrolytes has been investigated. XRD, DSC and
FESEM techniques have been used to explore the structural properties. The size distribution
of the nanoparticles has been investigated using TEM. The temperature
dependence of the dc conductivity of the CdO doped nanocomposite electrolytes has
been explained by the VTF relation. The relaxation dynamics have been studied in the framework of power law and electric modulus formalisms and are correlated to the structural changes.
In chapter 5 composite polymer electrolytes based on PEO, lithium bis (trifluoromethylsulfonyl)
imide (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl)
imide (BMPTFSI) ionic liquid have been investigated. The effect of BMPTFSI ionic liquid on crystallinity of PEO chain has been studied using XRD.
DSC technique has been employed to note the changes of the thermal parameters. Also the variation of the dc conductivity with temperature and BMPTFSI concentration
have been investigated. The VTF equation can adequately explain the temperature
dependence of the conductivity. To understand the ion dynamics and relaxation mechanism the ac conductivity and electric modulus spectra have been analysed using the existing theoretical models. The variation of the electrical results have been correlated with the structural changes.
Another ionic liquid based composite polymer electrolyte comprising of PEO,
lithium trifluoromethanesulfonate (LiTf) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf) as ionic liquid have been studied in chapter 6. XRD, DSC and FTIR studies have been performed in order to examine the structural changes in these composites. The nature and relative amounts of ionic species present in these
composites have been determined using FTIR spectroscopy. The temperature dependence
of the dc conductivity has been explained using Arrhenius and VTF equations.
The increase of dc conductivity with EMITf concentration has been correlated with
structural changes. The relaxation dynamics in these composites has been studied in the framework of the conductivity formalism. HN function have been used to study the electric modulus spectra and the results obtained are outlined here.
In Chapter 7 the summary of the thesis is presented. The possible future research in
continuation of this work is also highlighted.The research was carried out under the supervision of Prof. Aswini Ghosh of the Solid State Physics division under SPS [School of Physical Sciences]The research was conducted under Partial financial support from Council of Scientific and Industrial Research (CSIR), India & Department of Science and
Technology, Government of India (Nanoscience Initiative Program
Structure and Ion Dynamics of Some Glasses and Glass-Nanocomposites
Full text linkThe work of this thesis is mainly based on the study of structure and ion dynamics of
several new ion conducting glasses and glass-nanocomposites and to correlate the
macroscopic ion transport properties to the microscopic structure of the glasses and
glass-nanocomposites. The organization of the thesis is as follows
Chapter 1 of this thesis is mainly based on the literature review in the field of
glasses and glass-nanocomposites. A brief introduction to glasses and glassnanocomposites
is presented and their exotic features are discussed. The network
structures of different type of glasses are briefly discussed. The phenomenon of
crystallization kinetics in glasses is briefly discussed. Several theoretical models and
concepts used to explain and understand the ion dynamics are pointed out. Finally the
scope of the thesis is presented.
In chapter 2 a brief description of the preparation technique and various
experimental methods used to characterize the glasses and glass-nanocomposites are
presented. In the initial part of the chapter the structural characterization such as
density, x-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy techniques are discussed. In the later part, electrical characterization techniques used to study the ion dynamics are presented. Chapter 3 deals with the structural and electrical study of AgI doped silver selenite glasses and glass-nanocomposites. The structural investigations of silver selenite
glasses and glass-nanocomposites have been carried out using XRD, FESEM and TEM.
The dynamics of Ag+ ions in the glasses has been investigated in a broad frequency
range from 10Hz - 3GHz. The conductivity and dielectric relaxation study in these
glasses using the existing theory of conductivity, modulus and dielectric formalism are
presented. In Chapter 4 the study of structure and ion dynamics of several Ag2S doped silver molybdate glass-nanocomposites are presented. The microstructural characterizations of the glass-nanocomposites have been performed using XRD, FESEM and TEM study. The modification of the glass network structure has been analyzed
using FTIR spectroscopy. The study of relaxation dynamics in these glassii
nanocomposites has been accomplished in the framework of the conductivity and the
electric modulus formalism and correlated to the microstructure.
In chapter 5 the study of structure and ion dynamics of silver ion conducting
molybdophosphate mixed network former glasses are presented. The glass formation
has been confirmed using XRD. The glass network structures and structural modification
depending on composition has been investigated using FTIR spectroscopy. The ion
dynamics in these mixed former glasses has been studied using the conductivity
formalism as a function of frequency and temperature. The correlation of macroscopic
ion transport properties to the microscopic parameters and the glass network structure has been established.
Chapter 6 deals with the study of structure and ion dynamics of Ag+ ion
conducting silver selenomolybdate mixed former glasses. The structure of these glasses has been investigated using XRD, FTIR and DSC. The relaxation dynamics in these glasses has been studied in the framework of the conductivity formalism. It is revealed that the modification of the glass network structure influences the ion transport properties and there exists a correlation of the mixed glass former effects to the microscopic structural details. Chapter 7 deals with the study of crystallization kinetics of silver
selenomolybdate glasses with varying modifier oxide (Ag2O) content. Both isothermal and non-isothermal DSC techniques have been employed to study the nature of crystal nucleation and growth. Different theoretical models have been examined to find out the appropriate kinetic model. In Chapter 8 the summary of the thesis is presented. The possible future research in continuation of this work is also highlighted.The research was carried out under the supervision of Prof. Aswini Ghosh of the Solid State Physics division under SPS [School of Physical Sciences]The research was conducted under CSIR research fellowship and gran
Functional Noble Metal Nanoparticle for Biomedical Application
No full textThe work presented in this thesis entitled “Functional Noble Metal Nanoparticle for Biomedical Application” was initiated by the author in January, 2011 in Centre for «Seenced Materials, Indian Association for the Cultivation of Science, Kolkata, under ee sepervision of Dr. Nikhil Ranjan Jana.
Noble metal nanoparticles have versatile application potential in biomedical field == they are highly biocompatible, posses plasmon-based strong optical properties suitable Se detection/imaging and their synthetic method and surface chemistry are well eS-enced. Thus they have been successfully applied in cell labeling/subcellular targeting, eme-specific drug/gene delivery, photothermal therapy, selective and sensitive detection sf Geomolecules and extended to in vivo clinical studies. In recent years, fluorescent gold qumoctesters have gained increased research focus particularly in biolabeling and sensing ggpiacation duc to their low cytotoxicity, small hydrodynamic diameter and superior Siomestability. These attracted features make them promising cellular imaging probes and
cepiecement of toxic semiconductor nanocrystals. Currently researchers are concentrating on nanotechnology based solution of geumodicgenerative disease. Nanoparticles have the potential to influence the amyloid Sieiliatiom process and they could possibly cross blood-brain barrier to reach the amyloid Giees plague. Thus many efforts have been made on the development of nanoparticle Sesed anti-amyloid therapeutic probes for prevention and treatment of neurological Gender As for example, gold nanoparticle based functional probes are used for effective
execmme of amyloid aggregation and photothermal dissolution of preformed amyloid 7 vilro.
Although extensive amount of researches have been performed in developing high guiiity fanctional fluorescent gold clusters, their synthesis and surface functionalization oe stil challenging to the scientific community. Major problems involve poor synthetic the formation of larger proportion of nanoparticle side product that lowers Gee senthetic yield as well as fluorescence quantum yield of clusters.The research was conducted under the supervision of Prof. N R Jana under SMS [School of Materials Science]The research was carried out under CSIR fellowship
Chiral Synthons from Carbohydrates towards the Synthesis of Bioactive Natural Products
Full text linkConstruction of diverse molecular architecture containing carbocyclic frameworks, conceived and created by nature, continues to be the most exhilarating and challenging task
to the practitioners of organic synthesis. A large number of natural products which are isolated from natural resources possess carbocyclic skeletons as the primary structural unit and show a wide range of biological activities. Among the natural products, terpenoid class
of natural products are well suited for developing, testing and implementing new synthetic strategies towards the construction of carbocyclic frameworks. Thus, a combination of potential applications and the intellectual challenges associated with their synthesis have brought natural products into the center stage of contemporary organic chemistry-research. Investigation embodied in this dissertation entitled “Chiral Synthons from Carbohydrates towards the Synthesis of Bioactive Natural Products” directed towards the development
of synthetic methodologies for fused and bridged tricycle present in natural productThe research was conducted under the supervision of Prof. Subrata Ghosh of the Organic Chemistry division under the SCS [School of Chemical Sciences]The research was conducted under CSIR project and fellowshi