1. Ph.D Theses
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Item Design, synthesis and investigation on optoelectronic properties of thiophene based heterocycles(National Institute of Technology Karnataka, Surathkal, 2020) K, Viprabha.; Dalimba, Udaya Kumar.The use of π–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto– electronic properties. Most of the applications such as flexible displays and solid-state lighting sources based on organic light-emitting diodes (OLEDs) and nonlinear optical (NLO) devices are still in the developing stage due to the lack of ideal materials that exhibit the processability and an ability to interface with other materials. The research is continuing as ever to develop and characterize materials with large and fast optical responses which can satisfy different technological necessities. Furthermore, a definite correlation between the linear/nonlinear optical mechanism and the contribution of structure and nature of some thiophene based heterocycle is yet to be clearly interpreted. In this context, the present research work is focused on the design and synthesis of new class of thiophene based donor–acceptor (D–A) heterocycles for optoelectronic applications. A total of eighteen D–A type organic compounds were designed with various design strategies. They were successfully synthesized following appropriate synthetic protocols and characterized using different spectral analyses. The structureproperty relationships of the synthesized compounds were established by the optical absorption (UV–Vis), electrochemical (CV) and theoretical (DFT) studies. The third order NLO property i.e., the “effective two–photon absorption” of the compounds was confirmed by single–beam Z–scan analysis. The compounds VK3, VK8, VK10, VK12, VK13, VK14, VK15 and VK17 exhibit high nonlinear absorption coefficient (βeff) and a strong optical limiting behaviour. The preliminary studies on the electroluminescent properties of VK15 show that the molecule VK15 emits green light with low threshold voltage.Item Synthesis Characterization and Third-Order Nonlinear Optical Study of Some Transition Metal and Boron Complexes(National Institute of Technology Karnataka, Surathkal, 2013) B.J., Rudresha; Bhat, B. RamachandraThis research thesis entitled “Synthesis, Characterization and Third-order Nonlinear Optical Study of Some Transition metal and Boron Complexes” deals with the detailed information on synthesis of five different series of transition metal and boron coordination complexes for third-order nonlinear optical (NLO) study. Third-order NLO properties of all the synthesized complexes were measured using the open aperture Z-scan technique. The thesis divided into seven chapters viz Chapter 1 gives an overview of the introduction and historical background of nonlinear optics, theoretical aspects of light-mater interaction in nonlinear regime and different NLO processes and NLO materials. Chapter 2 deals with the literature review on NLO study of transition metals and boron coordination complexes and also the scope and objectives of the present work. Chapter 3 describes the synthesis, characterization and third-order NLO studies of diimine (1,10-phenonthroline and 2,2‟-bypyridine) based Zn(II), Cd(II) and Hg(II) complexes with 1D dipolar NLOphores. Chapter 4 explains the ultrafast and nonresonant NLO characteristics of two metal complexes (N-(2-pyridyl)-N'-(salicylidene) hydrazine triphenylphosphine Co(II) ([CoLPPh3]), N-(2-pyridyl)-N'-(salicylidene)hydrazine triphenylphosphine Pd(I) ([PdLPPh3])), incorporated into PMMA film was studied using time-resolved differential optical Kerr gate (DOKG) and Z-scan experiments. The synthesis, characterization and the third-order NLO properties of three new Cu(I) complexes with two electron withdrawing ligands has been discussed in chapter 5. Chapter 6 describes, the formation of “push-pull” boron fluoride complexes derived from chalcones. The NLO results show that these complexes exhibiting „„effective‟‟ 2PA property. Chapter 7 deals synthesis and NLO property of substituted N,N'-pphenylenebis(salicylideneimine) ligands as well as their coordinatively saturated boron fluoride complexes. Chapter 8 provides the summary of the work presented in this thesis along with the conclusions.