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Studies of Protein Confirmation in Water and Air/Water Interface by Langmuir Blodgett Technique
No full textExtensive studies on the protein structure and conformation is needed due to variety
of reasons. Proteins are suitable for preparing bioactive thin film. The formation of
protein monomolecular thin film with lesser aggregation is a current scientific interest
for its biological activity for the application of biomedical device fabrication. Apart
from these, it is important for biosensor, preparation of biocompatible substrate,
preparation of protein based monolayer/multilayer template for the growth of
inorganic crystal (biomineralization) etc. The protein aggregation/dissociation has
enormous relevance in the study of protein based molecular diseases such Thalasamia,
Alzheimer disease, etc. Moreover, the fundamental studies of protein
folding/unfolding in biophysics or biochemistry has also relevance in the work. The
study of protein aggregation could be studied in Langmuir-Blodgett (LB) trough at the
molecular level.
This dissertation entitled as “Studies on Protein Conformation in Water and
Air/Water Interface by Langmuir Blodgett (LB) Technique” deals with some
multi disciplinary work involving the combination of different techniques on the basic
study of development and characterization of protein and protein based bioactive thin film at air/water interface and subsequent transfer onto solid substrate. To understand the basic principles behind the these thin film formation, influence of surface treatment, the role of net charge of the system, the study of different aspects of protein-based film on air/water interface and subsequent transfer on a solid substrate is essential. Thus the protein conformation in water and air/water interface as well as in LB films are the focal theme of the proposed research that aims towards the understanding the science behind the various interactions involved in protein conformation. This dissertation comprises of nine chapters and two appendices.The research was carried out under the supervision of Prof. G B Talapatra of the Spectroscopy division under SPS [School of Physical Sciences]The research was conducted under the CSIR grant and CSIR -NET fellowshi
Hybrid Structure: Use of Semiconducting Nanoparticles in Donor/Acceptor Type Organic Solar Cells
Full text linkOrganic solar cells are not intended to compare with silicon solar cells but they
have several advantages regarding some specific applications, such as packaging flexible
screens and recharging cell phones and laptops. Unlike crystalline silicon, organic solar
cells could be manufactured at a lower cost.
In organic or polymer solar cells, device operation involves (1) excitons
generation, (2) charge separation and (3) carrier transport to the opposite electrodes.
Since the three steps occur in sequence, efforts have been made to enhance efficiency or output of each of the steps. Generation of excitons expectedly depends on matching of electronic absorption spectrum of the active materials with that of the solar illumination. Hence active materials are chosen accordingly. Exciton dissociation or charge separation, which occurs at the interface between a donor and an acceptor layer, takes place due to the internal field that develops owing to the difference of energy levels at the interfaces. Carrier transport, the third step, is directed by the internal field generated by the difference in work functions of the two electrodes. Apart from the electric field, mobility of charge carriers plays a major role in determining short-circuits current of photovoltaic devices. Organic photovoltaic cells have a limitation considering poor charge carrier
mobility and stability of the active materials. An effort has been made to fabricate solar cells based on organic and inorganic hybrid materials. In hybrid solar cells, inorganic nanocrystals are generally mixed in a host conjugated polymer to form a photoactive layer. Inorganic nanocrystals have several advantages in this direction.
These nanoparticles have a better charge carrier mobility than organic thin films
due to crystalline nature of the quantum dots. They are also very stable. The size control of II these nanoparticles allow for tuning of optoelectronic properties. Nanoparticles also have a large aspect ratio (surface area to volume ratio) which present more interface area with the host polymer matrix. These nanoparticles have however a limitation due to their insulating capping agent. An effort has been made to remove these capping agents by pyridine or by small chain amines (butyl amine, octaylamine, etc) which have a low vaporization point and could be removed through annealing after film formation.
Besides using nanoparticles as photoactive materials, they could be used as charge
transporting materials due to their superior charge carrier mobility. As a result, these nanoparticles have been used as channels for carrier transport in one or both photoactive layers of a photovoltaic cell. Carbon nanotubes (CNT) could also be used in this direction. Hybrid solar cells are a step forward for organic photovoltaic devices where we could tune the device performance to a large extent. We have carried the work of this thesis in this direction.The research was conducted under the supervision of Prof. A. J Pal of the Solid State Physics division under SPS [School of Physical Sciences]The research was carried out under CSIR & DST research gran
Synthesis, Characterization And Potential Applications Of Organosilicon Based And Related Mesoporous Molecular Sieves
Full text linkMesoporous materials having high surface area with tunable pore size distribution in nano scale dimensions have attracted widespread interest in recent times. These special properties make mesoporous materials focus of great research interests in catalysis, adsorption, sensing, separation, drug delivery and controlled release of bioactive pharmaceuticals. During the past two decades a prevalent interest and incredible resonance as a fundamental and technological challenge to chemists, physicists and engineers has been gained by organic-inorganic hybrid materials and macromolecular building blocks of nanoscale dimensions. Hybrid mesoporous materials are unique and molecular control of their intrinsic topological and chemical characteristics can be explained through self-assembly and nanochemistry techniques. Post synthesis and in-situ synthesis both the techniques have been adopted to develop the organic-inorganic hybrid mesoporous materials. Furfural imine functionalized mesoporous silica has been synthesized by using CTAB as structure directing agent by applying in-situ grafting technique. This furfural imine functionalized mesoporous SBA-15 has been also developed by employing post-grafting approach. Then these two different mesoporous materials have been subjected to react with Cu(OAc)2 to deliver Cu-grafted mesoporous organosilica. After Cu grafting different crystalline phases have been generated for the two different mesoporous silica materials. Also In another case –NH2 functionalized mesoporous organoslica has been developed by applying in-situ grafting technique. Surface of mesoporous SBA-15 has been functionalized by reaction with 3-aminopropyltriethoxy silane. Then –CO2H functionalized mesoporous SBA-15 has been synthesized by applying Schiff-base condensation reaction. Fe3O4 nanoparticle has been grafted into the mesopore channel of cysteine functionalized mesoporous SBA-15 material. Thiol-ene click chemistry has been adopted to prepare cysteine functionalized mesoporous SBA-15 material.The research was carried out under the supervision of Prof. Asim Bhaumik of the Material Science division under SMS [School of Materials Science]The research was carried out under CSIR fellowship and research gran
Environment Induced Protein-Surfactant/Lipid Bioconjugate formation in Aqueous Medium and Air Water Interface
Full text linkThe interaction with proteins with surfactants have great impact due to not only fundamental interest but also enormous biological importance. In the field of application, surfactant-protein system has been playing a significant role in developing biosensors, drug delivery protocols and various biomolecular devices. The protein entrapment into vesicle membrane and immobilization of this system without de-neutralization of solid substrate is extremely valuable in wide variety of industrial, biological , pharmaceutical and cosmetic applicationsThe research was conducted under the supervision of Prof. G B Talapatra of the Spectroscopy division under SPS [School of Physical Sciences]The research was carried out under DST research grant and fellowshi
Optical Modulation, Assembly And Advanced Applications Of Ultra Narrow Nanomaterials And Heterojunctions
Full text linkThis thesis aims at achieving superior control over the material synthesis of different dimensional nanostructure and their heterostructures to achieve the modulation of the optical properties. The proposed route of synthesis of semiconductor nanocrystals are particularly significant for optical applications due to superior transport and optical properties, and find application in diode lasers, amplifiers, and biomedical applications.The research was conducted under the supervision of Prof. Somobrata Acharya of CAM under SMS [School of Materials Sciences]The research was carried out under DST gran
DIELECTRIC RELAXATION SPECTROSCOPY AND ELECTRO-OPTICAL STUDIES OF ANTIFERROELECTRIC AND FERROELECTRIC LIQUID CRYSTALS AND LIQUID CRYSTAL NANO-COMPOSITES
No full textBlending nanomaterials with liquid crystal (LC) is considered to be a prospective method to
enhance the electro-optical properties of the host. Threshold voltage, driving voltage, residual
dc, response time and rotational viscosity etc. are found to decrease in nano doped LC system
and in turn the anisotropic order of the liquid crystalline host imparts order in the nano-sized
guest particles. Proper selection of size, shape and crystallographic phase of nanomaterial is
important to achieve desired improvements of the host. This dissertation presents results of
doping different type of nanomaterials in nematic, ferro- and antiferroelectric liquid crystal
medium. Conducting polymer nanotubes in nematic LC exhibits remarkable reduction in the
threshold and driving voltage which is good from application point of view. The residual dc
is also reduced significantly in the doped cell and the reduction is even more than that
observed in the carbon nanotube doped same LC system. The influence of multiferroic
bismuth ferrite nanoparticles on the electro-optical and dielectric properties of an
antiferroelectric LC mixture is investigated in planar cells. It is shown that dispersion of
nanoparticles lead to modifications of response time, spontaneous polarization, rotational
viscosity and voltage required for switching the molecules between two ferroelectric states in
the antiferroelectric phase. The large electric field exerted by the nanoparticles on LC
molecules and probable charge transfer among them, causes weakening of the interlayer and intermolecular interactions of LC molecules in the antiferroelectric and ferroelectric phases, respectively. In a ferroelectric LC/ conducting polymer nanotubes composite system electrooptic study reveals a lower electrical response time, rotational viscosity and spontaneous
polarization. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both pure and nanocomposite system have been obtained. The orientation of the four
dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound. Another aspect of this dissertation is to study a newly synthesized orthoconic antiferroelectric liquid crystal which provides an excellent dark state because of its high tilt. A detailed investigation of the dielectric, electro-optical properties and X-ray studies of the partially fluorinated high-tilt antiferroelectric LC material revealed that the SmA* phase of this material is of de Vries type. Double-peak polarization current response and tristable-optical-switching studies have revealed an antiferroelectric molecular ordering in the de Vries SmA* phase of this material. Two distinct dielectric relaxation peaks in the SmA* phase also complement the antiferroelectric-like ordering of the molecule in the SmA* phase.The research was conducted under the supervision of Prof. Subir Kumar Roy of the Spectroscopy division under SPS [School of Physical Sciences]The research was carried out under IACS fellowship and DST research gran
Pyrazole‐Derived Ligands In Palladium‐ Catalyzed Reactions
Full text linkIn chapter 1, the General background, we have briefly discussed
about pyrazole tethered ligands, Palladium as catalyst and pyrazole ligands in
palladium catalysis.
In chapter 2, a pyrazole tethered pyridine ligand assisted Pdcatalyzed
addition reaction of arylboronic acids to aryl aldehydes has been
described and it has also been demonstrated that the reaction medium plays
a decisive role in determining product formation.
In chapter 3, synthesis of some pyrazole tethered pyridine ligands
and their utility in Pd and Cu‐catalyzed addition reaction of arylboronic acids
to nitriles and palladium catalyzed addition of free (N‐H) indoles to nitriles
has been presented.
In chapter 4, use of pyrazole tethered imino phenolate ligand in
palladium catalyzed Suzuki‐Miyaura cross‐coupling reaction of bromo and
chloroarenes and oxidative Heck reaction has been presented.
In chapter 5, a new camphor based, pyrazole‐tethered chiral P, N
ligand assisted Palladium catalyzed asymmetric alkylation, amination and
asymmetric Suzuki‐Miyaura cross‐coupling reaction has been performed.
In keeping with the general practice of reporting scientific
observations, due acknowledgements have been made to the findings of
other investigators. The responsibility of any unintentional oversight is solely
mine.The research was conducted under the supervision of Prof. Amitava Sarkar, Organic Chemistry division under SCS [school of Chemical Sc]The research was conducted under CSIR fellowshi
Study Of Dissipative Quantum Dynamics In Some Model Systems
Full text linkIn majority of the treatments dealing with quantum dissipative systems as mentioned
above, the environment or reservoir is considered as a bosonic heat bath [2, 4, 14] which is
dominated by delocalized modes [3–5]. However, there arise situations, particularly, at low
temperatures where one has to take care of localized modes characterized by spin bath, e.g.,
magnetic relaxation of molecular crystals [17], decoherence of spin-1/2 electron interacting
with nuclear spins [18]. It need not be over-emphasized that a spin bath is a generically
distinct quantum object compared to a bosonic bath and the mapping between a bosonic
heat bath and a spin bath is extremely difficult due to the distinct university class of the
quantum environment [19]. Based on a genuine probability distribution function rather
than quasi-probability distribution to describe the reservoir, we in the present formulation
intend to derive a general framework of quantum dissipation which can deal with both
weak and strong damping and memory effects. Special emphasis is given to the problem
of dissipative two-state system in a spin bath which is the simplest nonlinear system to
study the interplay between quantum coherence, thermal fluctuations and dissipation.
Another important issue is the metastability of quantum state in the context of reaction
rate theory. We have confined ourselves mostly to the models that are simple enough to
be largely tractable by means of analytical methods. However, interesting situations have
been considered where numerical computations have given clues to the analytical solution
of a problem. Finally, one particular grafting feature of the present thesis is that it reveals a
close connection between many seemingly unrelated topics such as dissipative fermionic
oscillator, population trapping, quantum control and amplification, resonance fluorescence
and temperature assisted coherence in spin bath.
Our work is outlined as follows:
1. We begin with a proposal of a system-reservoir Hamiltonian which can serve as a
universal paradigm for the description of interaction between a quantum particle and
its environment in the form of a generalized bath. Making use of Holstein-Primakoff
transformation which sets up a mapping between boson and spin operators, we
show that the spin bath and the harmonic bath can be realized as two special limits
of this generalized bath. Making use of spin coherent state representation for the
description of the reservoir we have presented a canonical formulation of c-number
quantum noise and dissipation to explore the quantum Langevin equation and the
associated properties of the spin and harmonic baths to describe quantum dissipation
1.2 scope and summary of the thesis 4
of the system. The statistical character of the bath is characterized by the canonical
thermal distributions of the c-numbers for bosons and fermions. For spin bath this
distribution is a fermionic counterpart of Wigner thermal distribution wellknown for
bosonic bath and is a new and key content of our present formulation [21].
2. The quantum dissipation of a two-state fermionic oscillator in an environment of
fermionic oscillators is then considered. Since fermions anti-commute their eigenvalues
are anti-commuting numbers. Based on an expansion of the reduced density
operator in terms of fermionic coherent states which make use of these anticommuting
numbers or Grassmann variables, a Fokker-Planck equation for the
associated quasiprobability distribution function characteristic of fermionic oscillator
heat bath or two-state spin bath is derived. The density operator approach
to fermionic fields as introduced by Cahill and Glauber [22] is then extended to
non-equilibrium domain [23].
An offshoot of this study in the context of density operator expansion is a simple
model of parametric coupling between two fermionic oscillators. The statistical properties,
in particular, the mean and variance of quanta for a single mode are described
by means of the time-dependent reduced density operator for the system and the
associated P-function. Thus the density operator for fermionic fields can be shown
to provide a quantum mechanical description of the fields closely resembling their
bosonic counterpart. In doing so, special emphasis is given to population trapping
and quantum control over the states of the system [24].
3. We then proceed to derive the Bloch equations for a two-level system coupled to a
spin bath of infinitely many two-level atoms to examine phase and energy relaxation
of an optically excited system. Since two-level bath is a nonlinear system in contrast
to a harmonic oscillator bath, spin-spin and spin-lattice relaxation terms behave
differently from their bosonic counterpart. We show that increasing temperature
in spin bath assists coherence. This is reflected in a number of anomalous features
of relaxation of the system, e.g., decrease of integrated absorption coefficient with
temperature, nonlinear variation of linewidth with incident power. We also predict
that thermally induced coherence may result in anomalous narrowing of linewidth,
reminiscent (but distinct) of ‘motional narrowing’ of spectral line. Our theoretical
findings are discussed in the light of absorption-emission experiments on single
quantum dots [25].
4. Our treatment is then extended to explore the role of dissipation in the scattered
intensity and the spectrum of resonance fluorescence from an excited two-level system
in a spin bath. It has been shown that depending on the field strength a cross-over
temperature sets up a boundary between coherent and incoherent intensity regime
and at low field the scattered intensity may be coherent even at high temperature.
This temperature assisted coherence is a consequence of the nature of spin bath of
1.3 plan of the thesis 5
two-level atoms due to effective reduction of the system-bath coupling. Our findings
corroborate the experimental observation of universal dynamical decoupling of a single
solid-state spin from a spin bath [26]. We have also demonstrated how Mollow triplet
in resonance fluorescence can be realized as a thermally-induced process in the low
field regime, rather than as a field-induced effect as observed in traditional quantum
optics [27].
5. Finally the momentum dissipation of a system in a generalized spin bath is considered
and the associated pseudo-Langevin equation is derived. We then calculate the decay
rate from a metastable state which is a product of two types of terms, thermodynamic
and dynamic. While the thermodynamic factor characterizes the nature of the bath,
the dynamical factor originates from the system-reservoir coupling. It has been shown
that at 0K momentum coupling results in exponential enhancement of dissipative
tunneling in sharp contrast to exponential suppression of tunneling in the case of
spatial coupling. At finite temperatures the tunneling increases with increase in
temperature for both spin and harmonic bath. Because of thermal saturation of
the spin bath the thermal activation factor at high temperature contains an explicit quantum contribution and does not reduce to the standard Arrhenius factorResearch was conducted under supervision of Prof. D S Ray, Physical Chemistry division under SCS [School of Chemical Sciences]Under CSIR fellowshi
Hybrids of Supramolecular Gels and Covalent Polymers
Full text linkThe thesis comprises of nine chapters. Chapter 1 deals with a succinct
introduction of supramolecular chemistry along with the evolution of
supramolecular gels as a product of supramolecular chemistry. A brisk review on different classes of gelators, hybrids gels, and conducting gels is included.
Chapter 2 describes the experimental procedures taken up to complete the work.
Chapter 3 introduces a supramolecular gel based on folic acid and its hybrid with
a biopolymer, Chitosan, with improved mechanical and photophysical properties.
Chapter 4 depicts the hydrogel of Fluorenylmethoxycarbonyl-L-tryptophan, and
its hybrid with Polyethylene glycol, causing a mechanical reinforcement of the
native hydrogel. Also, the thixotropic and drug release properties of the native
gels are tuned by polymer incorporation. Chapter 5 depicts the nanoengineering
of a supramolecular gel of folic acid by addition of a co-polymer. The hybrids
exhibit an enhancement in fluorescence property, mechanical property, and
gelation rate compared to that of the native gel. Chapter 6 deals with the
preparation and characterization of a hybrid gel of folic acid and polyaniline, with improved mechanical and electronic properties. A hybrid conducting hydrogel of N-fluorenylmethoxycarbonyl Phenylalanine and polyaniline, and detailed studies on its mechanical and electronic properties, are portrayed in chapter 7. Chapter 8 deciphers the drastic difference in electronic properties of the gels and xerogels derived from co-assembly of a naphthalenetetracarboxilic dianhydride derivative and polyaniline. A summary of the research work along with the future prospects
obtained from this thesis are presented in Chapter 9.Research was conducted under the supervision of Prof. A K Nandi, Polymer Science Division under the SCS [School of Chemical Sciences]Research was carried out under CSIR fellowship and DST research gran
Studies on Metal-Organic Frameworks and Metallogels of Pyrazole based ligands and their Amide Derivatives
Full text linkMetal-organic frameworks (MOFs) or coordination polymers are one, two or three dimensional coordination networks, usually porous, comprising of metal ions linked together with one or more organic ligand or linker molecules having varied applications in the field of gas storage and separation, magnetism, catalysis etc. However there is a subtle difference in the definition of the term coordination polymers and metal organic frameworks. The former merely signifies an extended network formed due to coordination bond between metal and ligand(s) monomers and says nothing about the final structure or morphology. Metal-organic frameworks, on the other hand, should possess a geometrically well-defined structure made through strong covalent or coordinate bonding between the metal and ligand and comprising of units available for post-synthetic modifications. Metal-organic gels (MOGs) or metallogels are special class of supramolecular gels where metal plays an important role in gel formation either through covalent interactions with the ligand giving rise to 3D gel network or forming discrete metallogelators which then self-assemble to form gel via non-covalent interactions immobilising large quantity of solvents with the network. In both cases, the gels formed show metal specific properties such as spectroscopic, catalytic, redox and magnetic properties.Research was carried over under the supervision of Dr. Raju Mondal of Inorganic Chemistry division under SCS [School of Chemical Sciences]Research was conducted under DST grant and CSIR fellowshi