Faculty Publications
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Item An investigation on photophysical and third–order nonlinear optical properties of novel thermally–stable thiophene–imidazo [2,1-b][1,3,4] thiadiazole based azomethines(Elsevier Ltd, 2019) Kakekochi, V.; Udayakumar, U.; Nikhil, N.P.; Chandrasekharan, K.The use of ?–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. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1–TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1–TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z–scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (?eff) of the order of 10?10 m W?1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the ?–conjugation, providing an improved ?eff (0.81 × 10?10 m W?1) to TI1 compared to that of TI2 (0.55 × 10?10 m W?1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices. © 2019 Elsevier LtdItem Impact of donor–acceptor alternation on optical power limiting behavior of H–Shaped thiophene–imidazo[2,1-b] [1,3,4]thiadiazole flanked conjugated oligomers(Elsevier Ltd, 2020) Kakekochi, V.; Nikhil, P.; Chandrasekharan, K.; Udayakumar, U.A new series of four D–A–D configured conjugated oligomers with H–type structure, possessing two thiophene–imidazo [2,1-b][1,3,4]thiadiazole branches and thiophene (TIT), thiophene–1,3,4-oxadiazole–thiophene (TITO), thiazolo [5,4-d]thiazole (TITz), phenyl–thiazolo [5,4-d]thiazole–phenyl (TIPTz) units as central core moieties were efficiently synthesized. These core moieties were specifically selected to increase the planarity, rigidity, stability, extend the ?–conjugation and to understand the influence of central core on nonlinear absorption coefficient (?eff) and optical limiting behavior of the synthesized oligomers. The structure-property relationships of these oligomers were established by the optical absorption (UV–Vis), electrochemical (CV) and theoretical (DFT) studies. The “effective two–photon absorption” of oligomers was confirmed by single–beam Z–scan analysis. The exceptional increase in nonlinear response was achieved with the oligomers TITO and TIPTz with nonlinear absorption coefficient (?eff) of 1.62 and 2.71 × 10?10 m W?1, and limiting thresholds of 6.02 and 3.14 J cm?2, respectively, which suggest that these oligomers could be potent materials for practical applications in laser photonics. © 2020 Elsevier Ltd