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Synthetic Amino Acids and Peptides Based Gels
Get PDFThe research embodied in the present thesis entitled “SYNTHETIC AMINO ACID
AND PEPTIDE BASED GELS” deals with the synthesis, characterization and gelation
study of several synthetic self-assembling amino acid and short-peptide derivative and their various applications. Chapter 1 is the general introduction which provides the comprehensive literature survey
on low molecular weight supramolecular gels. This chapter highlights structural and
morphological features of amino acid and peptide based supramolecular hydrogels and
organogels and their different applications. Gel based various nanohybrid systems
incorporating different nanomaterials including nanoparticles, CNT, graphene have also been
discussed in this chapter.
Chapter 2 describes the reagents used and experimental procedures, carried out to
perform the entire work embodied in this thesis.
Chapter 3 describes the synthesis of N-terminally Fmoc protected -alanine containing
dipeptide hydrogelators and their hydrogel formation at physiological pH and temperature.
This chapter also describes characterization of these dipeptide based hydrogels by using FTIR
spectroscopy, field-emission scanning electron microscopic (FE-SEM), atomic force
microscopic (AFM) and rheological studies. This chapter also demonstrates that these
hydrogels can be potentially utilized for the encapsulation and sustained release of vitamins at
physiological pH and temperature and the proteolytic stability of the hydrogelator towards
proteolytic enzymes including protenase K and protease p-5380.
Chapter 4 describes the synthesis and gelation study of pyrene conjugated single amino
acid (phenylalanine) based self-supported, thixotropic, superhydrogel in the pH range 7.46-
14. Characterization of this amino acid based hydrogel by field emission scanning electron
microscopy (FE-SEM), fluorescence microscopy, differential scanning calorimetry (DSC),
circular dichroism (CD), X-ray powder diffraction (XRPD) and rheological studies is reported
in this chapter. This chapter also describes the distinct morphological change of the gel
nanofibers from helical to tape-like morphology using FE-SEM with an increase in pH and
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this observation has been supported by the different spectroscopic studies (FT-IR, CD and
XRPD). The pH dependent thixotropic property of hydrogels are also discussed here.
Encapsulation of vitamin B12 and an anticancer drug doxorubicin in the hydrogel matrix
utilizing thixotropic property of the hydrogel without any heating-cooling cycle and sustained
release of these bioactive molecules at physiological temperature (37 °C) and pH (7.46) over
a period of about 3 days are also described.
Chapter 5 demonstrates the hydrogelation of an N-terminally Boc-protected tripeptide.
This chapter describes characterization of the hydrogel by using dynamic scanning
calorimetry (DSC), FT-IR spectroscopic, X-ray powder diffraction (XRD), field-emission
scanning electron microscopic (FE-SEM), transmission electron microscopic (TEM),
fluorescence microscopic, polarized microscopic and rheological studies. This chapter also
demonstrates the synthesis of cystein and cystein containing dipeptide capped silver
nanoparticles and preparation of hybrid hydrogels by the incorporation of different ligand
capped silver nanoparticles into the hydrogel matrix. Lastly, the effect of incorporation of
these different ligands capped silver nanoparticles on the stiffness of hybrid hydrogels are
studied and compared with that of the native hydrogel.
Chapter 6 describes the synthesis and gelation of the N-terminally pyrene conjugated
tripeptide based fluorescent organogel in different aliphatic and aromatic solvents. Organogel
in o-dichlorobenzene (ODCB) has been thoroughly studied using various techniques
including transmission electron microscopic (TEM), field-emission scanning electron
microscopic (FE-SEM), atomic force microscopic (AFM), Fourier-transform infrared (FT-IR)
spectroscopy, fluorescence spectroscopic and rheological studies in this chapter.
Unfunctionalized and non-oxidized graphene has been successfully incorporated into this
fluorescent organogel in o-dichlorobenzene (ODCB) to form a stable hybrid organogel. This
graphene containing hybrid organogel has also been characterized using TEM, AFM, FT-IR,
PL, and rheological studies. The rheological investigation indicates that the flow of the hybrid
organogel has become more resistant towards the applied angular frequency upon the
incorporation of graphene into the organogel.
Chapter 7 presents the summary of all the investigations described in this thesis. The
significance of the results obtained from those investigations has also been discussed in this chapter. Each chapter (chapter 3 to 6) begins with a short ‘Introduction’ followed by ‘Experimental’, ‘Results and discussion’ and ‘Conclusion’.Research was done under the supervision of Prof. Arindam Banerjee of the Biological Chemistry division under SBS [School of Biological Sciences]Research was carried out under CSIR fellowshi
Luminescent Metal Nanoclusters: Synthesis and Sensing Applications
Get PDFIn recent years, synthesis of metal nanoclusters and deep understanding of many fundamental properties of the nanoclusters have drawn considerable attention owing to their multimodal application in light harvesting, hydrogen production, optical sensor, drug delivery and cancer therapy. Intriguing molecular-like properties, such as HOMO–LUMO, d-sp or sp-sp transitions, quantized charging and strong luminescence are often observed in metal nanoclusters. The optical properties of metal nanoclusters can be tuned by changing the number of metal atoms, surface functionality and heteroatom doping. However, the fundamental studies on tuning of these parameters and their effect on the photophysical properties of the metal nanoclusters are
still in the embryonic stage. In this context, current thesis describes the development of synthesis
methods for highly luminescent metal nanoclusters and metal nanoclusters based functional
materials, which can fabricate efficient nanomaterials to find out potential applications in optical sensing, light harvesting systems and other photo driven devices.Research was conducted under the supervision of Prof. Amitava Patra of the Materials Science division under SPS [School of Physical Sciences]Research was carried out under CSIR fellowshi
Synthesis and Functionalization of Carbon Based Nanomaterials for Biomedical and Environmental Application
Get PDFThe thesis focuses on the fabrication of various carbon based nanomaterials and their functionalization for promising application in biomedical and environmental science. Carbon based nanomaterials have been considered as green nanomaterials and promising alternatives tom that of emissive semiconductor quantum dots (QD) which are composed of toxic metal Cadmium (Cd) and non-metal like Selenium (Se), tellurium (Te), other green nanomaterials such as doped semiconductors nanocrystals, gold nanoparticles, fluorescent gold clusters, and silicon nanoparticles are under development and need further studyResearch was conducted under the supervision of Prof. N R Jana of CAM under SPS [School of Physical Sciences]Research was carried out under CSIR fellowshi
Phenomenological Study of the Physics Beyond the Standard Model at the Large Hadron Collider
Get PDFAfter the discovery of W and Z bosons at the CERN, probing the electroweak symmetry breaking
mechanism became a dominant theme of elementary particle physics since it is the primary mechanism
for generating the masses of the SM fermions and gauge bosons by incorporating a massive fundamental
scalar particle, the Higgs boson. Both the ATLAS and CMS collaborations of the Large Hadron
Collider (LHC) experiment discovered a SM Higgs like particle with a mass around 125 GeV. This observation
has also been supported by complementary evidence from the CDF and D0 collaborations of
the Tevatron experiment at the Fermilab. With this discovery, all the particles predicted by the SM are
now experimentally observed and most of the experimental results are in excellent agreement with the
theoretical expectations. Despite all the successes of the SM, there are certain issues, like the issue of
unnatural fine-tuning in the SM Higgs sector, observation of tiny mass of neutrinos, existance of dark
matter in the universe, observation of matter-antimatter asymmetry in the universe etc., all indicate that
the SM can’t be a complete theory of nature, rather it is an effective theory derivable from some more fundamental theory which remains valid at some scale much higher than the electroweak scale. Several new scenarios beyond the SM have been proposed to cure the shortcomings of the SM. Among them, Supersymmetry (SUSY) has been one of the most popular choices for formulating physics beyond the SM (BSM). In this thesis, we study some signatures of the BSM physics mainly in the context of supersymmetric theories at the LHC using the jet substructure technique. Now-a-days, the jet substructure technique has
become one of the most efficient and attractive discovery tool in the search of new physics signatures at the LHC. We apply the jet substructure technique to study the discovery potential of relatively light Higgs bosons ( 10 - 100 GeV) at the LHC. We find that clearly identifiable resonances corresponding to the light Higgs bosons appear in the invariant mass distribution of all jets which pass through the boosted Higgs tagging algorithm. We then study the sensitivity of the LHC to discover or exclude the inclusive LEP-LHC Higgs scenario, where one can simultaneously explain the observed mild excess (approx. 2.3s) around a 98 GeV Higgs mass at the LEP as well as the recently observed signal of a 125 GeV SM Higgs like particle at the LHC.We find that LHC may not be able to exclude such a possibility at the 14 TeV run, however, the proposed e+e International Linear Collider (ILC) will easily probe such a scenario and can discover the 98 GeV Higgs within first few years of run. Furthermore, we also study the signatures of light third generation of squarks, namely stop and sbottom, using the jet substructure technique at the 14 TeV run of LHC. We also investigate the discovery reach of the gluino and lighter top squark in the context of R-parity violating MSSM at the 14 TeV run of LHC.Research was carried out under the supervision of Prof. Dilip Kr. Ghosh of the Theoretical Physics division under SPS [School of Physical Sciences]Research was conducted under IACS research gran
Synthesis of Carbohydrate Functionalized Nanomaterials for Biomedical Application
Get PDFCarbohydrate functionalized nanomaterials have emergent application potential in the
field of biological science. Carbohydrates are the most abundant biomolecules in the
living body and are present in the form of glycoprotein, glycolipid and various other
complex structures. They play an important role in cell–cell communication, cell
signaling and metastasis of cancer cell. Some carbohydrate receptors are over expressed
in certain cancer cells. These receptors can be used for selective cancer targeting and
therapy by using carbohydrate functionalized nanomaterials. Carbohydrate functionalized
nanomaterials are used in protein detection, pathogen detection, sensing of biomolecule,
specific and non specific cellular labeling, targeted drug delivery, therapy and diagnosis
and in the study of various biological events in vitro and in vivo.
Preparation of good quality carbohydrate functionalized nanomaterials is very
challenging for the scientific community. Most of the carbohydrate functionalized
nanomaterials, reported in the literature, were prepared using thiol based ligand exchange
of thiolated carbohydrates. This approach is most popular as it produces monodispersed
particles of small hydrodynamic diameter. But this approach needs the synthesis of
thiolated carbohydrates and stabilization of carbohydrate functionalized nanoparticles in
physiological conditions, particularly in the presence of other thiol based biomolecules, is
a critical issue. Other approaches of preparation of carbohydrate functionalized are less
popular due to multiple steps, complexity associated with conjugation chemistry, poor conjugation efficiency, destruction of the carbohydrate structure during conjugation with nanomaterials, large hydrodynamic diameter of the resultant particle and limited colloidal stability of the final products. Therefore appropriate conjugation methods are highly desirable that can be used for preparation of different high quality carbohydrates functionalized nanomaterials useful for different biomedical application.Research was conducted under the supervision of Prof. N R Jana of CAM under SPS [School of Physical Sciences]Research was carried out under CSIR fellowship and gran
Structural and Magnetic Properties of Novel Oxides
Get PDFTransition-metal and rare earth based oxides belong to an attractive and
challenging field of research in condensed matter physics. This class of oxide possesses a
wide range of intriguing properties and reveals novel phenomena from insulator to
superconductor and ferroelectricity to ferromagnetism. The competition and coexistence
of different types of ground states gives rise to complex electronic and magnetic phases.
This thesis entitled “Structural and Magnetic Properties of Novel Oxides”
mainly concentrates on investigation of structural, optical, dielectric, electric and magnetic properties of some novel oxides such as BaTiO3, NiFe2O4, SrRuO3 and LaCrO3. Lattice distortion, defects and chemical composition are the key parameters to modify basic interactions to induce new behavior in oxides. Reduction of size to fundamental length scale i.e. coherence and cooperative length also significantly influences long range order in ferroelectric and ferromagnetic oxides.Research was conducted under the supervision of Prof. S K De of the Materials Science division under SPS [School of Physical Sciences]Research was carried out under CSIR fellowship and also CSIR & DST travel gran
Implications of Supersymmetry on dark matter, precision tests and collider experiments
Get PDFIn spite of the fact that the signature of supersymmetry (SUSY) is yet to be found, SUSY remains as a very strong candidate for a Beyond the Standard Model (BSM) physics. Apart from many
fundamental and phenomenological reasons, special relevance comes from the observation of the Higgs boson with a mass of 125 GeV at the Large hadron Collider (LHC). The mass is well within the upper limit of 135 GeV predicted by the Minimal Supersymmetric Standard Model (MSSM) for its lighter CP-even Higgs boson (h). In contrast, we know that the unitarity requirement within the Standard Model (SM) sets the Higgs mass upper bound to be about 800 GeV. Coming to SUSY Higgs, we note that in order to accommodate mh ' 125 GeV one must have large radiative
corrections to the tree level mass of h that can be given by a large trilinear (top) coupling parameter At. In general, a higher value of mh as observed in the LHC has made typical SUSY models less
natural or more fine-tuned. Apart from this, the lower limits from the LHC on the scalar and gaugino masses have also been increasing. Besides the collider limits, the WMAP/PLANCK experiments for dark matter relic density put severe constraints on SUSY models where the lightest neutralino, the lightest SUSY particle (LSP) may become a candidate for dark matter. Constraints from flavor
physics, particularly those from the B-physics observables also take away a lot of parameter space of a given SUSY model. Finally, there are stringent constraints from precision tests like muon
g −2 that deviates from the SM prediction significantly. In the post Higgs@125 GeV era, the work described here involves studying the low energy signatures of SUSY models and constraining the models through collider studies, precision measurements of relevant observables and dark matter
(DM) analyses via computation of relic density and relevant detection cross-sections.Research was conducted under the supervision of Prof. Utpal Chattopadhyay of Theoretical Physics division under SPS [School of Physical Sciences]Research was carried out under CSIR & DST gran
Transport properties of spin-orbit coupled electronic system
Get PDFThis thesis is a theoretical study of the e ect of spin-charge coupled dynamics on the
transport properties of two dimensional electron systems (2DES) with spin-orbit interaction.
It includes a prediction of a new phenomenon which is named as spin-spin Hall effect
and studies on anomalous Hall and spin Hall e ect when the applied electric field is inhomogeneous.
The calculations are mainly based on the Kubo formalism of the linear
response theory. The plan of the thesis is as follows –
Chapter 1: This chapter is an introduction to the thesis. The two main directions
of spintronics research is briefly pointed out. The spin orbit coupling is discussed in the context of controlling the electronic spin in semiconductor structures. The term that plays the key role behind all the phenomena addressed in this thesis is the Rashba spin orbit coupling term. This term originates from the lack of structural inversion symmetry in semiconductor heterostructures. The origin of such an asymmetry and the occurrence of
the Rashba term is presented including an outline of its derivation.
Chapter 2: It demonstrates how the presence of the Rashba coupling can be explored to explain as well as to predict some novel e ects in 2DES. Some essential general properties of the Rashba Hamiltonian that cause the spin-charge coupled transport in these systems are discussed. The proposal of SFET is presented followed by an overview of the three spin-dependent Hall e ects, namely, anomalous Hall e ect, spin Hall e ect and spin-spin Hall e ect. The corresponding conductivities are related to the current-current correlation functions. The problem of conservation of spin current and its possible way-out to perform linear response theory is reviewed.
Chapter 3: This chapter is devoted to Anomalous Hall E ect (AHE), which is an
intensively studied problem, yet awaits a clear physical understanding of its origin. AHE is studied in a disordered two dimensional electron system with Rashba spin-orbit coupling and ferromagnetic exchange interaction. It is known that when the Fermi level goes well above the band gap created by the exchange interaction, the anomalous Hall conductivity(AHC) vanishes in the metallic weak scattering regime due to disorder correction. It is shown that AHC may re-occur if the applied electric field is inhomogeneous, specifically, if it varies periodically in its own direction. The system parameters are related to the wavelength of this variation which may be properly tuned to maximize the magnitude of AHC.
Chapter 4: It contains a study on spin-Hall e ect; a phenomenon originally predicted
long back in 1971 and gained renewed interest in the spintronics perspective. In a two
dimensional pure Rashba system, the spin Hall conductivity (SHC) takes a universal value
which is exactly canceled by -function disorders irrespective of their concentration. In this
chapter, SHC as a function of frequency and finite wave-vector (perpendicular to the electric
field) is derived including disorder vertex correction. In the zero-frequency limit, dc-
SHC resonates when the periodicity of the electric field matches with the spin-precession length scale. The physical mechanism responsible for this extraordinary e ect is also described. Further, it is numerically shown that this result also holds (in fact with enhanced magnitude of SHC) when the modified definition for conserved spin-current is considered.
Chapter 5: This chapter predicts the existence of a novel phenomenon which may be called as spin-spin Hall effect. When the full charge-spin Hall conductivity matrix is calculated for a Rashba 2DES, it is found that there is another non-zero term apart from SHC.
VIII This term originates from the correlation of in-plane currents. A current of x-spin-polarized electrons in x-direction induces a current of y-spin-polarized electrons in y-direction. The effect of Dresselhaus spin orbit interaction on this phenomenon is also discussed.The research was carried out under the supervision of Prof. S S Mondal of the Theoretical Physics division under the SPS [School of Physical Sciences
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Where we stand? A scientometric mapping of Indian Science & Technology research in some major research areas
Get PDFContribution of research output in the field of Science & Technology by Indian researchers covered in Web of Science database is compared with other most productive countries for different research areas. This paper analyses the research activity of Indian scientists in terms of total number of publication, global share, share of international collaborative publications and visibility & citation impact for the period 2009-2014. The trend of research output in key research areas clearly indicates that all productive countries have their own strength and weaknesses in different research areas. India is steadily emerging as a potential contender in science & technology research in major research areas. Also South Korea, Taiwan and Iran from Asia subcontinent are progressing and they are among twelve most productive countries in some of the key research areas considered in this paper