http://localhost:8081/jspui/handle/123456789/24 2025-08-13T13:55:38Z 2025-08-13T13:55:38Z Malik, Jaideep http://localhost:8081/jspui/handle/123456789/18072 2025-08-11T06:38:45Z 2021-03-01T00:00:00Z

Title: NOVEL LAYERED TITANATES AND NIOBATES: APPLICATIONS IN PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS AND WATER SPLITTING Authors: Malik, Jaideep Abstract: Extensive industrialization and rapid population growth with decreasing groundwater at alarming rates make it challenging to access limited clean water resources. Due to incomplete treatment of industrial effluents, frequent use of antibiotics and personal care products, various organic pollutants have emerged to persist in the municipal wastewater that ultimately gets into the drinking water system untreated. On the other hand, the global energy demands are rising due to high growth rate of urbanization and industrial expansion, which are some of the greatest challenges of this century. As most of the global energy needs are fulfilled by fossil fuels, which is the main cause of global warming, energy generation from alternative renewable resources become indispensable. The solar energy reaching the Earth's atmosphere every hour is far beyond the annual energy demand of the whole world. It is abundant, free of cost and clean source of energy. After the discovery of water-photolysis on TiO2 semiconductor electrode by Fujishima-Honda in 1972, vast majority of research has been devoted on semiconductor photocatalysis that continues to grow even today, although the use of TiO2 and many other oxide semiconductors under solar irradiation is limited because of their UV active nature. Considering the abundance of ‘visible light’ amounting to ~ 43% of incoming solar energy, a lot of research efforts in the global arena have been devoted toward the development of visible-light-active photocatalysts for efficient utilization of solar energy. Semiconductor photocatalysis for degradation of harmful organic pollutants and hydrogen production from water renders a sustainable solution toward use and generation of renewable energy. Use of sunlight in semiconductor photocatalysis for pollutant degradation or wastewater treatment can avoid use of chemical reagents and electrical energy inputs. Ideally, an efficient sunlight-driven photocatalyst can find niche applications in some of the emergent areas of energy and environment.

2021-03-01T00:00:00Z Sharma, Anuj http://localhost:8081/jspui/handle/123456789/18033 2025-08-04T06:24:35Z 2021-02-01T00:00:00Z

Title: CARBAZOLE BASED ORGANIC MATERIALS FOR ELECTRONIC APPLICATION Authors: Sharma, Anuj Abstract: Carbazole and its derivatives have been the most effective heterocyclic building blocks for material scientists. Carbazole-based organic luminescent materials are extensively used in optoelectronic applications especially organic-light emitting diodes (OLEDs) as emissive as well as hole-transporting layer which enjoys its high charge mobility. The optical and electrical properties of these materials can be facilely tuned by multi-substitution of chromophores at C1, C2, C3, C6, C7, C8 and N9 positions of carbazole. Additionally, its sufficiently high triplet energy offers its utility as suitable host materials in electroluminescent devices. It’s self-emissive property, easy synthetic procedures, molecular rigidity and amorphous nature further proves its advantageous candidacy over other conventional fluorophores. In this thesis, we comprehensively examine the design, synthesis and optoelectronic properties of carbazole based functional materials. This thesis consists of seven chapters in total. The first chapter deals with the aim and scope of the work proposed on carbazole based organic materials for optoelectronic applications such as organic light-emitting diodes (OLEDs). The second chapter presented a detailed discussion on literature background based on synthesis and characterization of carbazole-containing organic fluorescent materials used for various applications such as fluorescent and phosphorescent OLEDs as well as molecular sensors. In chapter 3, a series of carbazole based derivatives (9-12) differing in the number of dicyanovinyl acceptors and donors (N-alkyl carbazole or N-phenyl carbazole) are designed, synthesized and characterized. The effect of donors on optical, electrochemical and thermal properties of carbazole-dicyanovinyl dyads is critically analysed. The dyes containing C3-linked carbazole donor showed red-shifted absorption and larger molar extinction coefficients when compared to the dyes containing N-phenylcarbazole attributable to the extended conjugation of C3-linked N-butylcarbazole. All the compounds showed positive solvatochromism in fluorescence attributable to intramolecular charge transfer in the excited state. The higher thermal stability of the dyes suggests the rigidity of the carbazole derivatives. Interestingly, all the dyes containing N-phenylcarbazole showed aggregation-induced emission properties in THF-H2O mixtures attributable to increased distortion in molecular configuration and restricted rotation in the solid-state. Furthermore, a green OLED device fabricated with the dye containing N-butyl carbazole donor as dopant emitter (3%) in CBP host achieved good performance with high external quantum efficiency (4.2%), current efficiency (13.1 cd A-1) and maximum brightness (Lmax) of 6180 cd/m2.

2021-02-01T00:00:00Z Singh, Anshu http://localhost:8081/jspui/handle/123456789/18025 2025-08-01T12:01:41Z 2021-07-01T00:00:00Z

Title: DESIGN AND SYNTHESIS OF BASE-METAL COORDINATION COMPLEXES AND THEIR APPLICATIONS AS CATALYSTS IN DIFFERENT ORGANIC TRANSFORMATIONS Authors: Singh, Anshu Abstract: The thesis entitled “Design and Synthesis of Base-metal Coordination Complexes and their Applications as Catalysts in Different Organic Transformations” is reported in seven chapters. In the present work is aimed to design and synthesis of unsymmetrical salen-type ligands, pentadentate ligands, pincer-ligands and azo-based non-innocent ligands. These ligands were characterized through different analytical techniques such as UV-visible, IR, NMR, ESIMS and NMR spectroscopy. These ligands were utilized for the synthesis of manganese, iron, cobalt, nickel and copper complexes. These synthesized complexes were characterized by UVvisible, IR, NMR, ESI-MS spectroscopy. Complexes were characterized by X-ray crystallography. These complexes were utilized as catalysts for different organic transformation involving C−C, C−N bonds formation using different reactions like synthesis of tetrazoles and propargylamines, reduction of nitroaromatics, N‐alkylation and α‐alkylation of ketones with alcohols and synthesis of quinolines, quinazoline and quinazoli-4(3H)-ones. We have done the selective dimerization of ethylene to 1-butene using diethyl aluminium chloride (DEAC) as a co-catalyst. The synthesized compounds were characterized through different analytical techniques such as NMR analysis. We have also done some biological activity such as superoxide dismutase activity.

2021-07-01T00:00:00Z Joshi, Ankita http://localhost:8081/jspui/handle/123456789/15789 2024-09-23T06:17:28Z 2019-08-01T00:00:00Z

Title: STRUCTURE AND PROPERTIES OF π-π INTERACTING COMPLEXES OF CARBON NANOTUBES Authors: Joshi, Ankita Abstract: Functionalization of carbon nanotubes (CNTs) has gained wide attention during the last two decades due to their applications in various optoelectronic devices. Such functionalization has been achieved by either covalently or non-covalently. The non-covalent functionalization is further classified into endohedral and exohedral. The endohedral functionalization involves the encapsulation of guest molecules inside the cavity of host CNT while in the exohedral one the molecules are adsorbed non-covalently on the surface of CNT. The non-covalently interacting endo- and exohedral complexes of CNTs are often stabilized by weak interactions such as π-π, C-H…π and N-H…π, depending on the functional groups present in the attached molecule. Among these, the π-π interactions are more common and exist between aromatic rings and CNT. Such interactions also exist between π-donor and π-acceptor molecules. In general, the various interactions such as dispersion, electrostatic and polarization stabilize the complex while the exchange interaction destabilizes it. Such complexes exhibit distinctive optoelectronic and charge transport properties which makes them suitable for their applications in organic electronic, organic light-emitting diode (OLED) and organic transistor devices. The donor-acceptor complexes of CNTs are particularly useful in OLEDs. The organic semiconducting complexes of CNTs with good carrier mobilities are potential candidates for organic transistors. They can be of p-type, n-type or ambipolar in nature depending on the magnitude of electron and hole mobility. Most of the studies on optoelectronic properties of the non-covalent complexes of CNTs have been done without an in-depth understanding of charge transfer at the molecular level. Besides, a molecular level understanding of the charge transport properties of such complexes are also lacking. In this regard, the computational investigation of the optoelectronic as well as the charge transport properties of non-bonded complexes of CNTs with donor or acceptor molecules is of utmost important. A new type of non-covalent functionalization of CNT is the mechanically interlocked nanotubes (MINTs). In MINTs, the movement of macrocycles on the surface of CNT is possible in presence of external stimuli such as light and can be used for various applications including molecular motors. In the present thesis, dispersion-corrected density functional theoretical methods are employed to study the interaction of carbon nanotubes (CNTs) with selected macrocyclic host molecules to explore their optoelectronic properties. ii The thesis is divided into seven chapters. In chapter 1, different types of functionalization of CNTs, mechanically interlocked nanotubes, their properties and applications are discussed. The earlier reported studies on the complexes of CNTs are also briefly reviewed. The important computational methodologies used in the present thesis are described in the second chapter. Beginning with Schrödinger equation, the quantum chemical methods such as Hartree-Fock and Post-Hartree-Fock methods are briefly discussed. Apart from these wavefunction-based methods, density functional methods used in the present work are also discussed. A brief outline of different types of functionals and basis sets is presented. This chapter also provides basic concepts of ground- and excited-state electron transfer processes for donoracceptor compounds. Various charge transport parameters such as reorganization energy, transfer integral and carrier mobility are explained. In chapter 3 of the thesis, stability, optoelectronic and charge transport properties of endo- and exohedral complexes of CNT with indigo are investigated using dispersion-corrected density functional B97-D in conjunction with 6-31G(d,p) basis set. The stabilization energy, ionization energy, electron affinity, the energy gap between the highest occupied and lowest unoccupied molecular orbitals (ΔEHOMO-LUMO), and absorption spectra of the complexes as well as their free components are determined. The ΔEHOMO-LUMO of about 1 eV is obtained for the complexes indicating them as organic semiconductors. The effect of number of indigo molecules on the above mentioned properties of their exohedral complexes with CNT is examined. The dependence of diameter of CNT on the stability and properties of its endohedral complexes with indigo is investigated. The effect of hybrid functional B3LYP-GD3 and long-range corrected hybrid functional ωB97X-D on the properties of most stable endohedral complex is examined. The photoinduced charge transfer for the exohedral complexes in which CNT behaves as a donor and indigo acts as an acceptor is observed. The optical absorption spectra of the complexes are simulated using the time-dependent density functional theoretical (TD-DFT) method. The complexes show charge transfer peaks in the visible and near-infrared regions of the electromagnetic spectrum. Based on the Marcus theory, the carrier mobility is calculated from the charge hopping rate. The carrier mobility calculations reveal that the exohedral complexes exhibit p-type character due to significantly higher hole mobility than electron mobility while the endohedral complexes possess nearly the same value of hole and electron mobilities. The results for the exohedral complexes of long and closed CNTs are similar to those obtained for the complexes of CNT of relatively small length as well as with open ends. Apart from this, the iii exohedral complex in which indigo is aligned parallel to the tube-axis exhibits almost similar value of hole and electron mobilities. The structure, optoelectronic and charge transport properties of the exohedral complex of (6,6)CNT with perylene bisimide (PBI) are investigated using different dispersion-corrected density functionals (B97-D, B3LYP-GD3 and ωB97X-D) in conjunction with 6-31G(d,p) basis set and the results are discussed in chapter 4. The electron density distribution in the frontier molecular orbitals of the complex indicates the possibility of photoinduced charge transfer from donor CNT to acceptor PBI constituting a donor-acceptor complex between them. Due to inappropriate size of the cavity of (6,6)CNT to host PBI, a relatively larger diameter (8,8)CNT is used for the encapsulation. The calculations of stabilization energy reveal that the endohedral complex PBI@(8,8)CNT is more stable than the exohedral complex PBI-(8,8)CNT. The energy decomposition analysis of the complexes suggests that the dispersion and the electrostatic interactions are predominant for endo- and exohedral complexes, respectively. In chapter 5 of the thesis, the structure and properties of endo- and exohedral complexes of (6,6)CNT with electron donor molecule quaterthiophene (4T) are investigated using various dispersion-corrected density functionals. A comparative study on the charge transport properties of both types of complexes is presented. The results indicate a n-type charge transfer characteristics owing to remarkably higher electron mobility than hole mobility, irrespective of the type of functionalization. The excited state calculations of the complexes carried out in the framework of TD-DFT indicate several charge transfer transitions from donor 4T to acceptor CNT in the visible region of the electromagnetic spectrum. The complexes also show very high light-harvesting efficiency implying their possible application in solar cells. The optoelectronic properties of the complexes of guest (6,6)CNT with macrocyclic hosts [10]cycloparaphenylene ([10]CPP) and its derivatives are studied using dispersion-corrected density functional method and are discussed in chapter 6. The various derivatives of [10]CPP are modelled by doping nitrogens as well as by substituting hydrogens with electron-donating amino/electron-accepting fluorine groups. The values of stabilization energy indicate that the complexes CNT@[10]CPP and CNT@nF-[10]CPP (n = 10, 20 and 40) are energetically stable. The frontier molecular orbital analysis predicted the occurrence of photoinduced charge transfer in the complex CNT@40F-[10]CPP. The optical absorption spectrum of the complex CPP-CNT indicates absorption in the near-ultraviolet and visible regions, whereas that of the complexes CNT@nF-[10]CPP show absorption in a wide range starting from near-ultraviolet to nearinfrared region of the electromagnetic spectrum. Among the complexes, high values of lightiv harvesting efficiency are obtained for CNT@nF-[10]CPP. The change in potential energy for the translational movement of CPP over CNT for both ground and excited states is examined. The results indicate an energy barrier for the piston type movement of CNT in the complexes for the ground state, but not for its excited states. The barrier for rotation of bare and fluorinated CPP over CNT suggests the application of these complexes as components in molecular wheels and shuttles. The summary and conclusions of the thesis are provided

2019-08-01T00:00:00Z