Faculty Publications

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    Thiophene-Based Conjugated Polymers: Synthesis, Linear, and Third-Order Nonlinear Optical Properties
    (CRC Press, 2016) Murali, M.G.; Udayakumar, D.
    Extensive research work in the field of CPs has started in late 1970s with the discovery of electrical conductivity in oxidatively doped poly(acetylene) [1]. This important discovery led to the award of Nobel Prize in chemistry in the year 2000 to three scientists: Hideki Shirakawa, Alan G MacDiarmid, and Alan J. Heeger. This pioneering work motivated the researchers to synthesize and to study the properties of other new classes of Π-CPs based on aromatic precursors such as p-phenylenevinylene, thiophene, pyrrole, carbazole, fluorene, and their derivatives (Figure 16.2) [2-5]. Early work in this field held the hope that these types of polymer systems would serve as replacements for highly conductive metals, such as copper and aluminum for electrical transport or related applications. However, due to the instability of these systems when highly doped, other more practical uses have been realized such as polymer light-emitting diodes (PLEDs) [6-11]. Moreover, in order to tune the specific properties desired for end-user applications, a proper modification of the monomer structure is essential that manipulates both the electronic and optical properties of these polymer systems. © 2017 by Taylor and Francis Group, LLC.
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    Plant-Based Treatments for Asthma and Chronic Obstructive Pulmonary Disease (COPD)
    (Springer Science+Business Media, 2025) Naik, S.; Udayakumar, D.; Issah, H.N.
    Asthma and chronic obstructive pulmonary disease (COPD) are long-term respiratory disorders characterized by airway inflammation, blockage, and oxidative stress. These conditions compromise lung function and negatively impact overall quality of life. While conventional medications are effective, they can often lead to undesirable side effects, sparking interest in alternative therapeutic approaches. Plant-based therapies, leveraging bioactive compounds found in medicinal herbs, present promising complementary or alternative options. Natural compounds like flavonoids, terpenoids, alkaloids, and phenolic acids possess anti-inflammatory, antioxidant, and bronchodilatory effects, which can help alleviate symptoms of asthma and COPD. This chapter explores the therapeutic potential of plant-based treatments, examining species like Boswellia serrata, Glycyrrhiza glabra, and Curcuma longa, which have demonstrated positive outcomes in both preclinical and clinical research. Topics include the mechanisms by which these phytochemicals exert therapeutic effects, their health benefits, and the challenges in incorporating plant-based remedies into conventional care. Additionally, the chapter discusses current research gaps and future directions to improve the safety, efficacy, and availability of plant-derived treatments for respiratory diseases, aiming to reduce dependence on synthetic medications. © 2025 The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.
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    Synthesis and characterization of a new donor-acceptor conjugated polymer and polymer/Ag nanocomposites
    (2011) Murali, M.G.; Udayakumar, D.
    A 3,4-didodecyloxythiophene and (1,3,4-oxadiazolyl)benzene unit bearing a donor - acceptor (D-A) type conjugated polymer is synthesized using precursor polyhydrazide route. The optical energy band gap (Eg) of the polymer is calculated from the absorption edge in the film and is found to be 2.28 eV. To prepare polymer/Ag nanocomposites films, different wt% silver nanoparticles are used. The presence of silver nanoparticles in the nanocomposite is confirmed by field emission scanning electron microscopy (FESEM). The optical properties of the polymer and the nanocomposites are studied using UV-vis absorption spectroscopy and fluorescence emission spectroscopy. Cyclic voltammetry is used to study the electrochemical properties of the polymer. © 2011 American Institute of Physics.
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    Z-scan and degenerate four wave mixing studies on newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units
    (2006) Kiran, A.J.; Udayakumar, D.; Chandrasekharan, K.; Vasudeva Adhikari, A.V.; Shashikala, H.D.
    The third-order nonlinear optical properties of newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units have been studied in DMF solution at 532 nm by using single beam Z-scan and degenerate four wave mixing techniques with nanosecond laser pulses. The variation of nonlinear response among the copolymers clearly indicates the dependence of ?(3) on donor and acceptor type of units present in the copolymers. The nonlinear refractive index, n2, of the investigated copolymers is found to be negative and the magnitude is as high as 10-10 esu. All samples exhibit strong reverse saturation absorption at the wavelength used and show good optical limiting of nanosecond pulses. The concentration dependence of n2 and the two-photon absorption coefficient (?) has been studied. © 2006 IOP Publishing Ltd.
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    Synthesis and characterization of new light-emitting copolymers containing 3,4-dialkoxythiophenes
    (2006) Udayakumar, D.; Vasudeva Adhikari, A.V.
    We report the synthesis, optical and electrochemical properties of a new series of polyoxadiazoles (P1-P3) consisting of 3,4-dialkoxythiophene and 1,4-divinylbenzene units. The polymers are prepared using the precursor polyhydrazide route. The polymers have well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 330 °C. The optical and charge-transporting properties of the polymers are investigated by UV-vis spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The UV-vis absorption spectra of polymers in solution showed a maximum at around 380 nm. The polymers depicted bluish-green fluorescence in solutions and green fluorescence in thin films. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from 3.25 to 3.31 eV and HOMO energy levels ranging from 5.48 to 5.56 eV, which indicated that the polymers are expected to provide enhanced charge-transporting (electron transport/hole blocking) properties for the development of efficient polymer light-emitting diodes (PLEDs). © 2006 Elsevier B.V. All rights reserved.
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    Synthesis and characterization of fluorescent poly(oxadiazole)s containing 3,4-dialkoxythiophenes
    (Elsevier, 2007) Udayakumar, D.; Vasudeva Adhikari, A.V.
    We report the synthesis, optical and electrochemical details, and properties of three conjugated copolymers (P1-P3) consisting of alternate hole-transporting thiophene derivative and electron-transporting 1,3,4-oxadiazole units. The polymers are prepared using the precursor polyhydrazide route. The polymers have well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 °C. All the polymers are soluble in organic solvents such as DMF, DMSO, NMP and in strong organic acids like trifluoroacetic acid. The optical and charge-transporting properties of the polymers are investigated by UV-visible spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The UV-visible absorption spectra of polymers in solution showed a maximum at around 400 nm. The polymers depicted green fluorescence both in solution and as thin films. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from -3.28 to -3.36 eV and high-lying HOMO energy levels ranging from -5.5 to -5.56 eV, which indicated that they may be promising candidates for electron-transporting or hole-blocking materials in light-emitting diodes. © 2006 Elsevier B.V. All rights reserved.
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    Third-order nonlinear optical studies of newly synthesized polyoxadiazoles containing 3,4-dialkoxythiophenes
    (2006) Udayakumar, D.; John Kiran, A.; Vasudeva Adhikari, A.V.; Chandrasekharan, K.; Umesh, G.; Shashikala, H.D.
    The third-order nonlinear optical properties of newly synthesized soluble polyoxadiazoles containing 3,4-dialkoxythiophenes were investigated by using Z-scan and degenerate four-wave mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of ?(3) determined from both the experiments. Z-scan results indicate a negative nonlinear refractive index, n2, whose magnitude is of the order of 10-10 esu for all the copolymers. The variation of nonlinear response among the copolymers clearly indicates the dependence of ?(3) on donor and acceptor type of units present in these copolymers. The copolymers exhibit strong reverse saturable absorption and good optical limiting properties at 532 nm. © 2006 Elsevier B.V. All rights reserved.
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    Synthesis and characterization of novel conjugated copolymers containing 3,4-dialkoxythiophene and 1,3,4-oxadiazole units
    (2007) Udayakumar, D.; Vasudeva Adhikari, A.V.
    In this report we describe the synthesis, optical and electrochemical properties of new conjugated copolymers (P1-P4) based on 3,4-dialkoxythiophene and 1,3,4-oxadiazole units. The copolymers are prepared using the precursor polyhydrazide route. The chemical structures of the copolymers are confirmed using FTIR, NMR spectroscopy and CHNS analysis. The polymers exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 °C. The optical and charge-transporting properties of the copolymers are investigated by UV-visible absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The polymers depicted blue/green fluorescence under the irradiation of UV light. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from -3.28 to -3.32 eV and high-lying HOMO energy levels ranging from -5.26 to -5.62 eV, which indicated that they may be promising candidates for the fabrication of polymer light-emitting diodes. In addition, the copolymers showed good third-order non-linear optical properties. © 2007 Elsevier Ltd. All rights reserved.
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    Nonlinear optical studies of a newly synthesized copolymer containing oxadiazole and substituted thiophenes
    (2007) John Kiran, A.; Udayakumar, D.; Chandrasekharan, K.; Ahdikari, A.V.; Shashikala, H.D.; Philip, R.
    We investigated the third-order nonlinear optical properties of a newly synthesized soluble copolymer containing oxadiazole and thiophene units using Z-scan and Degenerate Four Wave Mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of ?(3) determined from both experiments. Z-scan results indicate a negative nonlinear refractive index, n2, whose magnitude is of the order of 10-10 esu. The copolymer exhibits strong nonlinear absorption and good optical limiting properties at 532 nm, and hence may be a potential material for optical limiting applications. © 2006 Elsevier B.V. All rights reserved.
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    Synthesis and nonlinear optical characterization of copolymers containing alternating 3,4-dialkoxythiophene and 1,3,4-oxadiazolydbenzene units
    (2007) Udayakumar, D.; Kiran, A.J.; Vasudeva Adhikari, A.V.; Chandrasekharan, K.; Shashikala, H.D.
    We report the synthesis and linear and third-order nonlinear optical (NLP) characterization of two novel copolymers containing alternating 3,4-dialkoxythiophene and 1,4-bis(1,3,4-oxadiazolyl)benzene units. The copolymers were synthesized with a precursor polyhydrazide route. Both copolymers exhibited fluorescence around 430 nm under the irradiation of UV light. The NLO measurements were made with the single-beam Z-scan technique with Nd:YAG nanosecond laser pulses at 532 nm. The nonlinear refractive index of the investigated copolymers was negative, and the magnitude was as high as 10 -10 esu. The samples exhibited strong reverse saturation absorption and very good optical limiting properties at the wavelength used. The concentration dependence of third-order NLO parameters was studied. ©2007 Wiley Periodicals, Inc.