Browsing by Author "Kekuda, D."

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Boronic Acid-Based n-Type Semiconductor for Electronic Device Application
(Springer, 2022) Kagatikar, S.; Dhanya, D.; Kekuda, D.; Satyanarayana, M.N.; Kulkarni, S.D.; Karkera, C.
Electron transporting, or n-type, semiconductors can serve as charge-transport materials, and are ideal for use in organic electronic devices. Boron-based small organic molecules have garnered immense research attention as the heteroatom can effectively alter the electronic structures leading to excellent photophysical and electrochemical properties. A luminescent Schiff base (E)-(4-((2-(2-hydroxybenzoyl)hydrazono)methyl)phenyl)boronic acid (SHB) was prepared by a one-pot condensation reaction between salicyloyl hydrazide and formylphenylboronic acid. The synthesized molecule was chemically characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry. The blue-emitting boronic acid-derived molecule displayed intramolecular charge transfer, high carrier concentration, good thermal stability, a reversible reduction tendency and formation of uniform amorphous thin films. A diode was successfully fabricated via a solution processing technique with an ideality factor of 7.76. Further, AC conductivity, dielectric constant, dielectric loss, and capacitance values in a frequency range of 10–1000 Hz were extracted from dielectric studies. The dielectric constant of SHB was found to be 9.71 with an AC conductivity of 6.34 × 10−9 Ω−1 cm−1 at 1000 Hz. Graphical Abstract: [Figure not available: see fulltext.] © 2022, The Author(s).
Highly fluorescent materials derived from ortho-vanillin: Structural, photophysical electrochemical and theoretical studies
(2019) Poojary, S.; Acharya, M.; Abdul, Salam, A.A.; Kekuda, D.; Nayek, U.; Madan, Kumar, S.; Adhikari, A.V.; Sunil, D.
Small-molecule organic fluorophores are highly in demand attributed to their extensive prospective in material and biomedical applications. Particularly, luminescent ?-conjugated organic molecules that possess an efficient solid-state emission are excellent candidates for optoelectronic devices. Focusing on high demand of organic fluorophores, we herein report the synthesis of three organic fluorescent materials derived from o?vanillin, viz. an ester (F1), an azine (F2) and an azo dye (F3). Interestingly, F2 exhibited very intense luminescence in its aggregate phase due to the restriction in intra-molecular rotation (RIR), as demonstrated by solution thickening studies. Further, its Single Crystal X-ray Crystallography (SCXRD) study suggested the existence of various intra and inter molecular interactions and gave evidences for locked intra-molecular rotations of the benzene rings in the rigid conformation of the molecule. The bathochromic shift in fluorescence from solution to solid phase was confirmed by its thin-film emission spectrum, which evidences the formation of J-aggregates. The observed RIR, development of J-aggregates and high conjugation in F2 impart an excellent fluorescence in its aggregated state. Thin films of both F2 and F3 on ITO plates exhibited a bathochromic shift with a deep orange to red photoluminescence on UV excitation. Furthermore, the morphological characterization revealed the presence of clear dense grains in case of F2 and F3, while the DSC analysis indicated phase transitions of all the derivatives. As seen from dielectric measurement studies, the azo dye F3 exhibited the highest dielectric constant among the three derivatives. The electronic and photophysical data based on Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) calculations are in agreement with the experimental results. All the above data clearly advocate that, the synthesized fluorophoric o?vanillin derivatives are excellent candidates for electro-optical devices. 2018 Elsevier B.V.
Highly fluorescent materials derived from ortho-vanillin: Structural, photophysical electrochemical and theoretical studies
(Elsevier B.V., 2019) Poojary, S.; Acharya, M.; Abdul Salam, A.A.; Kekuda, D.; Nayek, U.; Madan Kumar, S.; Vasudeva Adhikari, A.V.; Dhanya, D.
Small-molecule organic fluorophores are highly in demand attributed to their extensive prospective in material and biomedical applications. Particularly, luminescent ?-conjugated organic molecules that possess an efficient solid-state emission are excellent candidates for optoelectronic devices. Focusing on high demand of organic fluorophores, we herein report the synthesis of three organic fluorescent materials derived from o?vanillin, viz. an ester (F1), an azine (F2) and an azo dye (F3). Interestingly, F2 exhibited very intense luminescence in its aggregate phase due to the restriction in intra-molecular rotation (RIR), as demonstrated by solution thickening studies. Further, its Single Crystal X-ray Crystallography (SCXRD) study suggested the existence of various intra and inter molecular interactions and gave evidences for locked intra-molecular rotations of the benzene rings in the rigid conformation of the molecule. The bathochromic shift in fluorescence from solution to solid phase was confirmed by its thin-film emission spectrum, which evidences the formation of J-aggregates. The observed RIR, development of J-aggregates and high conjugation in F2 impart an excellent fluorescence in its aggregated state. Thin films of both F2 and F3 on ITO plates exhibited a bathochromic shift with a deep orange to red photoluminescence on UV excitation. Furthermore, the morphological characterization revealed the presence of clear dense grains in case of F2 and F3, while the DSC analysis indicated phase transitions of all the derivatives. As seen from dielectric measurement studies, the azo dye F3 exhibited the highest dielectric constant among the three derivatives. The electronic and photophysical data based on Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) calculations are in agreement with the experimental results. All the above data clearly advocate that, the synthesized fluorophoric o?vanillin derivatives are excellent candidates for electro-optical devices. © 2018 Elsevier B.V.
Orthovanillin azine ester as a potential functional material for organic electronic devices
(Elsevier B.V., 2023) Kagatikar, S.; Acharya, S.; Mp, Y.; Dhanya, D.; Kekuda, D.; Abdul Salam, A.A.; Sudhakar, S.N.; Mn, S.; De, S.
The present study reports the synthesis of OVAE, an ester of ortho-vanillin azine, and its structural characterization using spectral and single crystal-XRD studies. Intermolecular interactions of OVAE are investigated using the Hirshfield surface analysis, 3D Hirshfield surface maps, 2D fingerprint plots, and electrostatic energy frameworks. Good thermal stability in thermogravimetric analysis, irreversible redox peaks in electrochemical studies, high carrier concentration and dielectric constant in electrical measurements, uniform films observed upon surface morphology examination, fabrication of a diode, the obtained current-voltage characteristics, dielectric constant and frequency-dependent AC conductivities directed towards the use of OVAE as a potential semiconducting functional material in suitable electronic devices. Based on cyclic voltammetry and AC impedance response, the performance of OVAE as an electrode material is explored by constructing a supercapacitor, which exhibited a specific capacitance of 56 Fg−1 at 10 mV s−1. © 2023 Elsevier B.V.
Pyrene-based chalcones as functional materials for organic electronics application
(Elsevier Ltd, 2023) Kagatikar, S.; Dhanya, D.; Kekuda, D.; Satyanarayana, M.N.; Kulkarni, S.D.; Sudhakar, Y.N.; Vatti, A.K.; Sadhanala, A.
Though new generation organic electronic devices have evolved from mere scientific perceptions to real-life marketed applications, considerably less research attention has been focused on n-type or electron transporting small molecule semiconductors. The present study is focused on the exploration of structural, thermal, electrochemical, electrical, and optical properties of two pyrene-based chalcones: PC1 and PC2, synthesized through Claisen Schmidt condensation reaction. The chalcones displayed good thermal stability and wide bandgap n-type semiconducting behaviour with high charge carrier concentration and dielectric constant. The experimental evidences including fluorescence measurements, nanoaggregate size, and morphology analysis, supported by DFT calculations and molecular dynamic simulations advocated the intramolecular charge transfer and aggregation-induced enhanced emission features of the molecules. Successful fabrication of a diode in combination with the current-voltage characteristics established the candidature of PC1 and PC2 for electro-optical devices. The dielectric studies were performed to measure dielectric constant and AC conductivity at different frequency ranges. The cyclic voltammetry and AC impedance response of PC2 differed from PC1 due to the inclusion of a fluorine atom in the molecular scaffold. Further, the functional implication of PC2 as an electrode material was explored by constructing a supercapacitor, which offered a specific capacitance of 220 Fg-1 at a scan rate of 10 mV s−1. Moreover, these chalcone-based organic semiconductors displayed high thermal and charge carrier concentration as well as compatibility with other layers in an OLED device. Hence PC1/PC2 can be further investigated as dopants along with other emissive layers as host materials in OLEDs. © 2022 Elsevier B.V.
Third-order nonlinear optical properties of Mn doped ZnO thin films under cw laser illumination
(2013) Nagaraja, K.K.; Pramodini, S.; Santhosh, Kumar, A.; Nagaraja, H.S.; Poornesh, P.; Kekuda, D.
We report the measurements of third-order nonlinear optical properties of undoped zinc oxide and manganese doped zinc oxide thin films with different doping concentrations investigated using z-scan technique. Thin films were prepared by radio frequency magnetron sputtering using a compound target on glass substrate at room temperature. The structural properties of the deposited films were analysed by X-ray diffraction studies. The atomic force microscope analysis of the deposited films reveals that the grain size and roughness of the films depend on the Mn concentration. The direct energy band gap of the deposited film increases with the increase in Mn concentration in the films. The nonlinear optical measurements were carried out using a cw He-Ne laser at 633 nm wavelength. The z-scan results reveal that the films exhibit self-defocusing nonlinearity. The third-order nonlinear optical susceptibility ?(3) is found to be of the order of 10-3 esu. The films investigated here exhibit good optical power limiting at the experimental wavelength. 2012 Elsevier B.V. All rights reserved.
Third-order nonlinear optical properties of Mn doped ZnO thin films under cw laser illumination
(Elsevier B.V., 2013) Nagaraja, K.K.; Pramodini, S.; Santhosh Kumar, A.; Nagaraja, H.S.; Poornesh, P.; Kekuda, D.
We report the measurements of third-order nonlinear optical properties of undoped zinc oxide and manganese doped zinc oxide thin films with different doping concentrations investigated using z-scan technique. Thin films were prepared by radio frequency magnetron sputtering using a compound target on glass substrate at room temperature. The structural properties of the deposited films were analysed by X-ray diffraction studies. The atomic force microscope analysis of the deposited films reveals that the grain size and roughness of the films depend on the Mn concentration. The direct energy band gap of the deposited film increases with the increase in Mn concentration in the films. The nonlinear optical measurements were carried out using a cw He-Ne laser at 633 nm wavelength. The z-scan results reveal that the films exhibit self-defocusing nonlinearity. The third-order nonlinear optical susceptibility ?(3) is found to be of the order of 10-3 esu. The films investigated here exhibit good optical power limiting at the experimental wavelength. © 2012 Elsevier B.V. All rights reserved.