Sandeep Kumar

Raman Research Institute, Bengalūru, Karnātaka, India

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Publications (7)14.02 Total impact

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    ABSTRACT: The effect of cadmium selenide quantum dots (CdSe QDs) on the dielectric relaxation and material constants of a ferroelectric liquid crystal (FLC) has been investigated. Along with the characteristic Goldstone mode, a new relaxation mode has been induced in the FLC material due to the presence of CdSe QDs. This new relaxation mode is strongly dependent on the concentration of CdSe QDs but is found to be independent of the external bias voltage and temperature. The material constants have also been modified remarkably due to the presence of CdSe QDs. The appearance of this new relaxation phenomenon has been attributed to the concentration dependent interaction between CdSe QDs and FLC molecules.
    Journal of Applied Physics 07/2014; · 2.21 Impact Factor
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    ABSTRACT: Octadecylamine capped cadmium selenide quantum dots (CdSe QDs) were dispersed in the ferroelectric liquid crystal (FLC) FELIX 16/100. The QD dispersed FLC system was investigated on the planar anchored cell. Addition of specific concentration of the QDs in the pure FLC induces a new relaxation mode along with the Goldstone relaxation mode. QDs assisted quantum fluctuations are probably responsible for the existence of this new relaxation mode in the QDs dispersed FLC system. The ionic contaminations associated with the FLC materials were trapped on the surface of QDs due to the ion-trapping character of QDs. The trapping of ionic contaminations was confirmed by the a.c. conductivity measurement. The physical properties of the pure and dispersed FLC were carried out as a function of doping concentration of QDs, temperature and frequency.
    Liquid Crystals 04/2014; · 2.35 Impact Factor
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    ABSTRACT: 2013): High-temperature chiral nematic phase in naphthalene and cholesterol derivative liquid crystal: characterisation and dielectric relaxation study, Physics and Chemistry of Liquids: An International Journal, This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings,
    Physics and Chemistry of Liquids 04/2013; · 0.52 Impact Factor
  • Sandeep Kumar
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    ABSTRACT: The columnar phases of discotic liquid crystals (DLCs) have been well recognized as one-dimensional organic semiconductors due to their unique self-organising supramolecular architecture. Though more than 3,000 DLCs from about 60 different cores have been synthesized, only a few DLCs derived from discotic cores such as, triphenylene, hexaazatriphenylene, pyrene, perylene, tricycloquinazoline, porphyrin, phthalocyanine and hexabenzocoronene are experimentally studied for their electrical and photoconducting properties. This chapter presents the synthesis of these DLCs and related materials.
    Liquid Crystalline Semiconductors, Springer Series in Materials Science, Volume 169. ISBN 978-90-481-2872-3. Springer Science+Business Media Dordrecht, 2013, p. 97. 01/2013;
  • Sandeep Kumar
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    ABSTRACT: This review article provides a bird’s-eye view on discotic liquid crystals and their potential applications. Design principles, synthesis, modification of physical properties and potential applications of some common discotic liquid crystals have been briefly summarized.
    Israel Journal of Chemistry (Online) 10/2012; 52(10). · 2.56 Impact Factor
  • Sandeep Kumar, Laxmi Kishore Sagar
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    ABSTRACT: Cadmium selenide quantum dots (QDs) have been dispersed in a discotic liquid crystal columnar matrix. Thermophysical properties of these liquid crystal nanocomposites were investigated by UV-Vis spectroscopy, photoluminescence spectroscopy, differential scanning calorimetry, polarizing optical microscopy, DC conductivity and small angle X-ray diffraction.
    Chemical Communications 11/2011; 47(44):12182-4. · 6.38 Impact Factor