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COMPUTATIONAL STUDY OF MECHANISM AND ENERGETICS OF CHEMICAL PROCESSES INVOLVED IN MATERIAL INDUSTRY
Full text linkThe thesis provides insight into electronic structure, complex
reaction mechanism, kinetics, and thermochemistry of molecules and processes having industrial interest employing high-level theoretical methods.An introduction to the thesis, containing five chapters, is given in the first chapter to provide an idea about the industrial chemistry. The second chapter briefly describes the computational chemistry and provides a review of theoretical methods. The remaining chapters of the thesis are
based on the research papers published in reputed international journals. The original papers have been properly formatted to match the style of the thesis. Each chapter reviews the material
presented in two papers.The research was conducted under the supervision of Prof. Abhijit Kumar Das of the Spectroscopy division under SPS [School of Physical Sciences]The research was carried out under CSIR fellowship and research gran
Study of photophysical properties of doped/undoped semiconductor and metal nanoparticles and their heterostructures
Full text linkColloidal nanocrystals have been the centre of attraction of materials science research due to the ability of tailoring their properties with size, shape or composition of the same, in comparison to their bulk counterparts. Among these, mostly studied are binary and alloyed
binary nanocrystals comprising of group II-VI and III-V materials. CdSe has been the work horse in this area with the emission covering the entire visible region. But the intrinsic toxicity along with the problem of re-absorption and self quenching in many of these binary
materials limit their applications in several fields. To overcome these issues, insertion of intra-band gap states has been proved to be the most efficient way. The frontiers in this field are
doped semiconductors where an external impurity atom is introduced which creates a trap state that takes part in the radiative recombination process and the ternary nanocrystals, where substituitional defect takes part in the radiative recombination process. These
semiconductor nanocrystals have been applied to many different technological areas including biological labelling and diagnostics, light-emitting diodes, electroluminescent devices, photovoltaic devices, lasers and single-electron transistors. Apart from changing the size and composition of the nanocrystals, creation of novel nanostructures and the mechanism of crystal growth have been investigated driven both by
the excitement of understanding new science and also their potential applications in specific
cases of device based technologies and catalysis etc. With the proper manipulation of reaction parameters, e.g., precursors, temperature and stabilizing agents, many structurally
unprecedented motifs have been discovered including polyhedrons, rods and wires, plates and prisms, and other advanced shapes such as branched rods, stars and multipods etc. Another important research direction in nanomaterials synthesis has been the expansion from single-component nanoparticles to hybrid nanostructures with discrete domains of different materials arranged in a controlled fashion, be it a semiconductor-semiconductor, metal-metal or semiconductor-metal.35-36 The attraction of multicomponent nanostructures is
that multiple functions can be integrated into one system for specific applications. Moreover, the interactions between nanoscale-spaced components can greatly improve the overall application performance of the system and even generate new synergetic properties. For
example, Au epitaxially connected with the semiconductors show improved charge
separation and enhanced light absorption of the semiconductor part, as well as can alter the luminescence behavior of semiconductors. Both of these increase the photocatalytic and light-harvesting efficiencies of semiconductors. Several semiconductor-semiconductor
heterostructures have also been reported.The research was carried out under the supervision of Prof. Narayan Pradhan of the Materials Science division under SMS [School of Materials Sciences]The research was conducted under IACS fellowship and DST research garn
Structure, microstructure and physical properties of ZnO based nanocomposites
Full text linkthesis entitled “Structure, microstructure and physical properties of ZnO
based nanocomposites” deals mainly with the structural, photoluminescence and
photoconductivity properties of different ZnO-based nanocomposite materials in various
forms. These properties have been discussed by analyzing the role of defect states and band
alignment of the composite materials in controlling the optical and opto electrical properties of the materials. Among all the wide band gap semiconductors, nanostructured ZnO (Eg ̴ 3.37 eV) has been paid a great attention by the scientific world due to its high exciton binding energy (60 meV) which is much higher as compared to GaN and ZnSe having the same semiconductor properties of ZnO and also because its ability to grow in different forms of nanostructures by cheaper synthesis methods. In this work, the nanocomposite structures have been grown by using different chemical synthesis processes and the properties of the composite nanostructures have been compared to the as-grown ZnO nanostructures synthesized by aqueous chemical growth (ACG) and sol-gel techniques. The characterizations of the as-grown and nanocomposite samples have been done using the techniques such as xray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), photoconductivity
measurements etc. The entire thesis consists of ten (10) chapters. It starts with a general introduction and ends with a summary of the results. A brief review on the past and recent works on ZnO based nanocomposites reported in the literature has been presented before the respective chapters. Experimental techniques used for characterizations of the samples have also been described in detail.The research was carried out under the supervision of Prof. Durga Basak of the Solid State Physics division under SPS [School of Physical Sciences]The research was being conducted under CSIR fellowship and research gran
Locked Nucleic Acid (LNA): An Improved Alternative to DNA for Nanoscale ‘On-Surface’ Nucleic Acid Detection
Full text linkThe research work embodied in the present thesis entitled “Locked Nucleic Acid (LNA): An Improved Alternative to DNA for Nanoscale ‘On-Surface’ Nucleic Acid Detection” deals with the effectiveness of the locked nucleic acid (LNA) probe, which is conformationally more rigid than DNA, is
nuclease resistant, and is less susceptible to molecule-surface non-specific interactions, as a better alternative to DNA probe towards development of sensitive, target-specific and robust nucleic acid sensorResearch was carried out under the supervision of Prof. Rupa Mukhopadhyay of Biological Chemistry division under SBS [School of Biological Sciences]Research was conducted under CSIR grant & fellowshi
Synthesis and tailoring of physical properties of different nanostructured Oxide-semiconductors
Full text linkThe research embodied in the present thesis entitled “Synthesis and tailoring of physical properties of different nanostructured Oxide-semiconductors” deals with the synthesis and unique physical properties of oxides based wide band gap semiconductor in nano scale. Nanostructured materials are currently very important and attractive for fascinating physical properties. Quantum size, surface effects and breaking of symmetry at nanoscale significantly modify the bulk properties. Physical properties can be tuned by varying size and shape of nanomaterials. Metal oxides exhibit a rich variety of electronic and optical properties. The main objective of this thesis work is to investigate and tune the structural, optical, catalytic, electrical and plasmonic properties of nanosized metal oxides by controlling the size, shape, surface chemistry and doping. In addition, search for highly transparent conducting oxide and non-toxic white light illuminating nanocrystals is also addressed. A brief review of all the chapters of the thesis is presented here. Past and present works, the plan and procedure of this work, the results from the systems and control experiments, and discussion on the results have been put forward in eight chapters of this thesis.Research was carried out under supervision of Prof. S K De of Materials Science division under SPS [School of Physical Sciences]Research was conducted under CSIR fellowship
Studies In Extra Dimensional Theories
Full text linkStandard Model (SM) of particle physics is one of the beautiful creation of human being which can
explain the world of subatomic particles with great accuracy. But this beautiful theory is not entirely
flawless and therefore unable to answer some natural phenomena. It has been shown that due to the large
radiative correction the Higgs mass diverges quadratically and cannot be confined within TeV scale unless
some unnatural fine tuning is performed, this is known as the hierarchy problem and SM is not
capable of controlling this huge divergence. In order to resolve the hierarchy problem one can choose
many proposed theories of beyond SM. In this thesis we consider the theory with extra spatial dimensions
which is a very promising candidate in the search for the beyond SM signatures in the Large Hadron
Collider experiment. Among all the extra dimensional theories Randall-Sundrum (RS) model has some
distinctive features. It assumes a five dimensional space-time with a warped small extra dimension and
the warping parameter depends on the extra dimensional coordinate. The warp factor plays a crucial role
in generating the mass hierarchy from Planck to TeV scale without further introducing any intermediate
energy scale in the theory. Therefore this unique geometrical structure of space-time in RS model can
solve the gauge hierarchy problem. In the context of the RS model, the Kaluza-Klein (KK) mass modes
of different fields exhibits interesting features which makes RS scenario phenomenologically lucrative.
It predicts the presence of a negative tension visible brane in the AdS bulk which is an undesirable situation
in terms of the stability of the brane. It was shown in a work by Sengupta, Das and Maity that
five dimensional RS model can be generalized by including a non-zero cosmological constant induced
on the 3-branes while the bulk geometry is anti de-Sitter and with this consideration both the dS and
AdS brane configuration can be achieved. This modified background provides a solution to the gauge
hierarchy problem and a positive tension visible brane can be obtained while the background geometry
of the brane is AdS space-time. RS model further has been generalized by Chowdhury and Sengupta to
six dimensions with flat 3-branes. This model has many phenomenological implications. Subsequently
six dimensional generalization has been extended with the effect of the induced cosmological constant on the 3-branes in order to find a correlation between the observed value of cosmological constant, nonhierarchical moduli of extra dimensions and the solution of the gauge hierarchy problem. In one of our work we assumes a generalization mechanism of RS model where the effect of the back reaction of the bulk stabilizing scalar field on the background space-time has taken into account.
All these generalized RS scenarios are extremely interesting in the context of the particle and gravitational
phenomenology. In this thesis we study different theoretical and phenomenological consequences
of RS/Generalized RS scenarios and try to generate an insight that whether these all warped geometry models are consistent with the ongoing high energy experiments.Research was carried out under the supervision of Prof. S. Sengupta of the Theoretical Physics division under SPS [School of Physical Sciences]Research was conducted under DST gran
Studies on some optical and electrical properties of some nanocomposites
Full text linkThe thesis comprises of nine chapters and concluding remarks (Appendix-I) along with a list of publications (Appendix-II) at the end. The chapter -1 contains a general introduction on semiconductor
nanoparticles/quantum dots, metal nanoparticles, and nanoparticles of organic materials. The chapter -2
describes several common phenomenon related to UV-vis spectroscopy, steady-state photoluminescence (PL)
spectroscopy, IR spectroscopy and electrical (dark and photo) conductivity in doped and undoped polymeric
thin films, semiconductor thin films. Details about the experimental techniques, set-up, procedures, samples and
chemicals used in the present study are described in chapter -3. Work on the surface electrical properties of
PMMA thin films (without dispersed nanoparticles) under different experimental conditions are discussed in
chapter -4. Studies on charge storage in poly(methyl methacrylate) thin films are explored in chapter -5. The
results of similar studies in case of other solvents having different boiling point are presented in chapter -6.
Electrical (dark and photo) conductivity of thiol capped CdS quantum dots embedded in PMMA thin films as a function of sample cell temperature, scan speed of bias voltage, intensity and different size of CdS quantum dots etc. are presented in chapter -7. The spectacular oscillations in current (dark and photocurrent) in thiol capped CdS quantum dots at different concentration embedded in PMMA matrix are presented in chapter -8. Finally, Studies on the electrical conductivity of poly (methyl methacrylate) thin films dispersed with carbon nanotubes (CNTs) using sandwich type cell configurations are explored in chapter -9. To make the chapters self content repetition of some scientific statements, references and relevant experimental procedures could not be avoidedThe research was conducted under the supervision of Prof. Biswanath Mallick of Spectroscopic division under SPS [School of Physical Sciences]The research was carried out under CSIR fellowship and gran
Theoretical Investigation of Reaction Mechanisms of Chemical Reactions Related to Renewable Energy
Full text linkThis thesis titled "Theoretical Investigation of Reaction Mechanisms of Chemical Reactions Related to Renewable Energy" is mainly based on the exploration of the mechanistic pathways of reactions related to alternative energy, which is an important topic of research both academically and in practice. This thesis combines two relevant topics in research and through computational aid we have tried to design strategies or propose mechanisms of plausible reactions that are associated with i) the hydrogen storage problem and ii) metal-free reduction of CO2. It is believed that the results could give quick explanations to the chemistry lying beneath these intriguing problems which are also practically relevant. The organization of the thesis is as follows.Research was conducted under the supervision of Prof. Ankan Paul of RCAMOS under SCS [School of Chemical Sciences]Under CSIR research project gran
Design and Syntheses of Metal Ion Templated Self-Assemblies and Anion Recognition through Second Sphere Coordination
No full textSelf-assembly is used to describe the process in which a disordered system
of pre-existing components forms an organized structure or pattern as a
consequence of non-covalent interactions among the components
themselves, without external direction. Self-assembly suggests the
distinction between ‘‘self’’ and ‘‘non-self,’’ with recognition and selection
between the two during assembly. According to Lehn, supramolecular
chemistry can be described as an information science in which molecular
components that contain the necessary information, self-assemble into
large specific structures.Consequently, self-assembly has been
recognized as a powerful tool for the construction of supramolecular
scaffolds, as established by several excellent contributions.To achieve self-assembled systematized architecture, the necessary
instructions must be incorporated into the structures of the building blocks
by chemical synthesis. Thus, molecules can be made to self-assemble
spontaneously into multi-component complex structures when they are
instructed to do so. The instructions exist in the form of the molecule’s
shape, its chemical properties, and how well it fit into the space where the
assembly takes place etc. Each step in the assembly process is reversible
and dynamic, that means the complex product is constantly forming,
dissipating and proceeds via an error correcting method. Over the last two decades, the field of metallo-supramolecular selfassembly
has emerged as a promising area of research for the development
of specific, three-dimensional structures of increasing complexity and
functionality.The beginning of this area of research has been
benefited from design principles that consist of the ligand geometry and
metal coordination geometry, thus opening up routes towards rationally designed classical supramolecular architectures. The success of this melal
assisted self-assembled supramolecular architectures lies in its wide range
of applications. Metal ion mediated self-assembled helical compounds are
one of the most important and remains a crucial area for research over the
last two decades.The research was carried out under the supervision of Prof. Pradyut Ghosh, Inorganic Chemistry division under the SCS [School of Chemical Sciences]The research was conducted under CSIR fellowship and projec
Application of Fluorescence Correlation Spectroscopy and Femtosecond Upconversion to Study Biological Assemblies
Full text linkThis thesis is based on mainly two techniques- FCS (fluorescence correlation
spectroscopy)6 and femtosecond up-conversion. Primarily, we have focused on
dynamics of protein and then extended our work to explore the dynamics at differentregions of a live eukaryotic cell. We explored the differences between a normal cell
and a cancer cell.
We have applied FCS to study size and conformational dynamics of a protein
(cytochrome C) in its native, molten globule and unfolded state with and without a room temperature ionic liquid (RTIL). FCS gives overall size of a protein molecule. But the distance between two residues or two domains of a multi-domain protein cannot be obtained from FCS. Hence, we have chosen human serum albumin (HSA) as a multi-domain protein and
applied FRET to study inter-domain distance of this protein. In order to observe the micro-environment around a particular residue we have studied solvation dynamics of HSA covalently labeled by a solvation probe. After protein, we have moved on to study eukaryotic cell. Cytoplasmic lipid
droplet (CLD) has attracted vigorous recent attention because of its involvement in many metabolic diseases including cancer.10 We have studied the number, polarity, diffusion and solvation dynamics inside the CLD of a lung cancer cell and compared
the results with that of a normal lung cell. Finally, we have investigated excited state proton transfer (ESPT) inside the cytosol of a Chinese hamster ovary (CHO) cell. We extended this work to study ESPT in the most acidic organelle of a cell, i.e. lysosome. The difference between a cancer cell and a normal cell has also been discussed in this regard.The research was carried out under the supervision of Prof. Kankan Bhattacharya of the Physical Chemistry division under SCS [School of Chemical Sciences]The research was done under CSIR fellowship and DST research gran