Functional Porous Nanocomposite: Synthesis and Application

Porous nanomaterials have received great attention in different research field of nanoscience and nanotechnology such as drug delivery, bio-imaging, detection, catalysis, optics energy and environmental application. This is due to their high surface area, tunable pore size and structure. Chemical stability and versatile chemistry for functionalization. Most widely used porous materials of pore size less than 2mm, mesoporous materials of pore size 2 to 50 mm and macroporous materials of pore size larger than 50 mm. Among these microporous materials have limited application due to small pore size but other two porous materials have wide range of applications. Recent sudy shows that nanoparticle incorporated porous materials can be used for multifunctional application. Various nanoparticles have their unique chemical and physical properties.Research was carried out under the supervision of Prof. N R Jana of SMS [School of Materials Science]Research was conducted under CSIR fellowshi

New Organic-Inorganic Hybrid Nanoporous Phosphates And Silicates: Synthesis, Characterization And Their Adsorption, Optical And Catalytic Applications

Microporous and mesoporous oxides, phosphates, borates, aluminates, silicates, organicinorganic hybrids, organic polymers etc. remain in the centre of research interest due to their versatile applications in many frontier areas of chemical and physical sciences like symmetric/asymmetric catalysis, gas storage and optoelectronics. Often the structure directing agents (SDA) used in the synthesis of non-silica based mesostructured materials keeping the mesoporous framework intact is a very challenging task. So my aim was to synthesis organicinorganic hybrid microporous and mesoporous phosphonates and silicates materials from the tailor made organic precursor molecules. These precursor molecules were designed in such a way that the final nanoporous materials had ion-exchange, adsorption, emission, sensing, or catalytic properties etc. Moreover, depending on the nature of the functional groups grafted at the surface of the designed microporous and self-assembled mesoporous organic-inorganic hybrid materials their applications in gas and metal-ion adsorption, optical and catalytic properties were explored. This thesis gives a comprehensive report on the results of the synthesis of porous hybrid tin phosphonates, sulphonated zinc phosphonate, self-assembled titanium phosphonate, iron phosphonate and phosphonic acid functionalized periodic mesoporous organosilica materials together with their catalytic and optoelectronics properties.The research was carried out under the supervision of Prof. Asim Bhaumik of the Materials Science division under the SMS [School of Materials Science]The research was conducted under CSIR fellowshi

Synthesis of Carbohydrate Functionalized Nanomaterials for Biomedical Application

The research was conducted under the supervision of Prof. N R Jana of SMS [School of Materials Sciences]The research was carried out under CSIR fellowshi

Shape Control Synthesis And Application Of Alloyed And Heterostructured Nanomaterials

This thesis aims at achieving superior control over the synthesis of different nanomaterials with size, shape, composition varaiation and their heterostructure to attain superior photophysical properties and investigation of their applicability in the field of catalysis, phosensing, photovoltaic and photoploraization depending upon suitable material propertiesResearch was conducted under the supervision of Prof. Somobrata Acharya of CAM under SPS [School of Physical Sciences]Research was carried out under the CSIR fellowship and gran

Design and Syntheses of Metal Ion Templated Self-Assemblies and Anion Recognition through Second Sphere Coordination

Self-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

Transport properties of spin-orbit coupled electronic system

This 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

Hybrid Core-Shell Nanoparticles: Fabrication and Characterization of Light-Emitting Diodes

Organic light-emitting diodes (LEDs) have limitations considering poor charge carrier mobility and stability of the active materials. An effort has been made to introduce inorganic quantum dots in LEDs. In LEDs based on the two types of semiconductors, both inorganic nanocrystals and organic materials are generally used as active materials. Inorganic nanocrystals have several advantages in this direction. Inorganic nanoparticles have higher charge carrier mobility than that in organic thin films due to the crystalline nature of the quantum dots. The nanocrystals are also very stable. By varying the diameter of the quantum dots, color tuning of the devices can also be achieved. These nanoparticles have however a limitation due to their insulating capping agent. An effort has been made to remove these insulating stabilizers and replace them with dithiols so that the interdot spacing will be improved and hence would render facile carrier conduction. The layers of a conventional light-emitting diode consists of (1) transparent bottom electrode (indium tin oxide, ITO), (2) hole-transporting layer, (3) light emitting layer, (4) electron-transporting layer, and (5) top electrode (Al, Ca, Mg). We planned to substitute the organic layers by air stable semiconducting nanoparticles. The devices have been characterized by measuring external quantum efficiency (EQE), electroluminescence (EL) spectra and switching speed (time taken to emit light). The active light emitting quantum dots (QDs) along with II organic or inorganic semiconductors as charge-transporting layers were used in these LEDs. It is common to use N,N' bis(3-methylphenyl)-N,N'-diphenyl-benzidine (TPD), nickel oxide (NiO), and graphene oxide (GO), as the hole-transporting layers; poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and molybdenum oxide (MoO3) are used as hole-injecting layers; zinc oxide (ZnO) is a common electron-transporting materials. An active layer of QDs as a emitting material is sandwiched between the carrier transporting layers. All the devices were fabricated on ITO coated glass substrates that were used as the bottom electrode. The hole-transporting, active QD, and electron-transporting layers were spun in succession followed by annealing in nitrogen environment. Finally aluminum was thermally evaporated under vacuum to deposit the top electrode. We have fabricated different light-emitting diodes based on hybrid materials or inorganic QDs and have characterized them. The past and recent works, work plan, experimental procedure, results of all scientific investigation, and discussion have been described in the first seven chapters of the thesis. The eighth chapter consists of concluding remarks about all the systems and the results that we have studied. A brief review of all the chapters is given below.Research was conducted under Prof. A J Pal of the Solid State Physics division under SPS [School of Physical Sciences]Research was carried out under CSIR and DST gran

Synthesis, Photo-physical Studies and Applications of Different Doped and Un-doped Semiconductor Nanocrystals

High quality semiconductor nanocrystals (quantum dots, QDs) are small crystal consisting of hundreds to a few thousand atoms each with typical dimension ranging from 1-100 nm which are great interest for fundamental studies and different technological applications such as light emitting devices, lasers, solar cells and biomedical labeing. The quantum mechanical coupling of over hundreds to thousands atoms develops the band structure in semiconductors. In this regime, the spatial confinement of the electronic charge carriers in the nanocrystal leads to a phenomenon known as Quantum Confinement Effect (QCE). Due to this effect, the size and shape of these “artificial atoms” can be used to widely tune the energy of discrete electronic energy states and optical transitions. For this the emission from these particles can be tuned throughout the ultraviolet, visible, near-infrared, and mid-infrared spectral ranges, making them useful for both biological imaging and many types of optoelectronic devices. State-of-the-art semiconductor nanocrystals have been designed to have a quantum efficiency of radiative recombination approaching unity at room temperature, far above what has been achieved from bulk materials. The reason of this high efficiency is also govern by the QCE as the strong overlap between the electron and hole wave functions in the confined structure increases the probability of radiative recombination whereas the exciton in bulk semiconductors is not confined in space and can rapidly dissociate, increasing the probability of non-radiative relaxation process associated with crystalline defects and charge carrier traps on crystal surfaces. Among semiconductor NCs CdSe as the work horse, have been widely studied for their fundamental properties and applications. Despite their so many advantages, the intrinsic toxicity of Cadmium has cast a doubtful commercial future for this promising field. Wide band gap semiconductor nanocrystals, such as zinc chalcogenide doped with transition metal ions, has overcome this concern and yet maintained the advantages of the nanocrystal emitters. Mn and Cu doped zinc chalcogenide semiconductor NCs can give bright yellow orange and tunable blue green emission respectively which has been found very stable and having high quantum yield making them useful for different practical application without having highly toxic Cd metal. Besides their low toxicity by replacing cadmium in CdSe quantum dots with zinc, these doped materials do not also reabsorb the photon which avoids self-quenching, a common phenomenon in quantum dots because of small stokes shift. In contrast, the emission color from a dopant, involving d–states of transition metal ions, to a large extent is fixed and independent of the size of the host. The only way to get substantially different dopant colours is to use different dopant ions. Unfortunately, doping such impurity ions into nanoparticle hosts has proven to be unexpectedly difficult, and different synthesis methods have to be followed to get different d–dots.Research was carried out under the supervision of Prof. Narayan Pradhan of Materials Science division under the SMS [School of Materials Science]Research was conducted under IACS fellowship and DST research gran

First Principles Study Of Emergent Phenomena In Strongly Correlated Systems

In the present thesis work, we have employed first principles as well as model Hamiltonian calculations to understand some of the emergent properties of 3d and 5d transition metal oxides (TMOs) belonging to the family of strongly correlated systems. We have studied nature of magnetism in Cu-based TMOs Na2BaCuV2O8 and PbCuTe2O6. The intriguing crystal geometry of these two cuprates give rise to diverse magnetism ranging from one-dimensional uniform S = 1/2 antiferromagnetic (AFM) chain as observed in Na2BaCuV2O8 to geometrically frustrated magnetism in PbCuTe2O6, where the arrangement of spins on a lattice precludes satisfying all interactions simultaneously leading to fascinating quantum spin liquid ground state. In addition, we have also studied copper based pyrovanadate Cu2V2O7 where an evolution of magnetic dimensionality is observed in its various polymorphs namely α, β and γ-Cu2V2O7. Unlike the other polymorphs, the α-phase is found to exhibit giant ferroelectric polarization (0.55 μC/cm2), largest among the Cu-based multiferroics, driven by symmetric exchange striction mechanism. We have also investigated pyroxenes, a family of potential magnetoelectric and multiferroic materials. Our calculations provide insights on the magnetism in the Cr-based pyroxene LiCrSi2O6 where spin-orbit coupling (SOC) is found to play an important role. We show exchange striction is the driving mechanism for the ferroelectric polarization present in this system.Research was conducted under the supervision of Prof. Indra Dasgupta of Solid State Physics division under SPS [School of Physical Sciences]Research was carried out under CSIR research gran

Pyrazole‐Derived Ligands In Palladium‐ Catalyzed Reactions

In 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