Browsing by Author "Singh, Bachcha"

Now showing 1 - 5 of 5
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    Design and development of a multiwalled carbon nanotubes-based copper (II) Schiff base complex for the facile non-enzymatic electrochemical sensing of glucose
    (Springer, 2023) Gupta, Rashmi; Yadav, Mamta; Singh, Smita; Ganesan, Vellaichamy; Singh, Bachcha
    A new bifunctional nanomaterial, [SBCu(II)Hyd]-MWCNTs, exhibiting exotic electrical and magnetic properties has been synthesized via chemical modification of MWCNT-COOH. Double probe DC electrical conductivity, CV and EIS studies show better conductivity of the material than that of MWCNT-COOH. With higher saturation and remanent magnetization, as well as coercivity, [SBCu(II)Hyd]-MWCNTs showed better ferromagnetic characteristics. Mott�Schottky electrochemical analysis was carried out to explore capacitive and dielectric properties. The enhancement in electrical conductivity of [SBCu(II)Hyd]-MWCNTs is also confirmed by optical and electrochemical band gaps studies. Subsequently, this material has been utilized to fabricate an electrochemical sensor by coating it over glassy carbon electrode for the determination of glucose. The corresponding sensitivity and limit of detection values are calculated to be 1.1 �A �M?1�cm?2 and 0.09��M, respectively. Graphical Abstract: [Figure not available: see fulltext.] � 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Influence of bipyridine isomers and some structurally related compounds on nematic liquid crystal orientation at the aqueous interface
    (Elsevier B.V., 2023) Mishra, Kirtika; Singh, Bachcha
    In this paper, orientational anchoring transition of nematic liquid crystal (LC) 4-cyano-4?-pentylbiphenyl (5CB) at the LC-aqueous interface in the presence of bipyridine isomers (2,2?-bipyridine (BPY22) and 4,4?-bipyridine (BPY44)) and some structurally related compounds (1,10-phenanthroline (PANTH110) and aldrithiol-4 (ALD4)) in the aqueous phase is presented. The addition of BPY22, BPY44 and PANTH110 into the aqueous phase causes 5CB to undergo concentration dependent planar-to-homeotropic transition at the LC-aqueous interface. In contrast, ALD4 on addition into the aqueous phase depending on its concentration diminishes the interface between 5CB and the aqueous phase. Furthermore, the LC ordering transitions are related to pH of the solutions containing BPY22 or BPY44 or PANTH110 as revealed by the cross-polarized optical images and the changes in the tilt angle. Density functional theory (DFT) has been used to evaluate stabilization energy and hydrogen bonding strength for understanding the mechanism of LC ordering at the aqueous interface. Our findings provide a new set of compounds that cause homeotropic alignment of 5CB at the LC-aqueous interface, which is a prerequisite for the development LC based biosensors. � 2023 Elsevier B.V.
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    Investigation of mesomorphic, photophysical and gelation behavior in aroylhydrazone based liquid crystals: Observation of mesophase crossover phenomena
    (Elsevier B.V., 2022) Kanth, Priyanka; Shankar Rao, D.S.; Krishna Prasad, S.; Singh, Bachcha
    Five series of substituted aroylhydrazones having two alkoxy chains at 3- and 5- positions at amide end of the molecule have been synthesized; wherein each series differ from each other in terms of number and position of alkoxy chains at imine end. The compounds of first series with the single alkoxy chain at 4-position at imine end self-assembled into columnar hexagonal mesophase. The lower homologues of the series with alkoxy chains at 3- and 5- positions at imine end showed a transition from columnar hexagonal to columnar rectangular mesophase in cooling cycle while the higher homologues exhibited columnar hexagonal mesophase. The series with alkoxy chains at 3- and 4- positions exhibited columnar rectangular mesophase. All the homologues of series with alkoxy chains at 2-, 3- and 4- positions showed a transition from columnar rectangular to columnar oblique mesophase in cooling cycle. The series with alkoxy chains at 3-, 4- and 5- positions exhibited transition in columnar hexagonal mesophase. The mesophase crossover from one columnar mesophase to the other was found to be dependent on the chain length as well as on the temperature during the self-assembly process in these molecules. The temperature dependent columnar mesophase crossover has been observed for the first time in these systems. The substitution pattern showed an influence on the photophysical properties. The number and position of alkoxy chains played a critical role in the formation of gel in these molecules. These liquid crystalline gelators have application potential in organic optoelectronic functional materials and devices. � 2021 Elsevier B.V.
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    Liquid crystal-based optical sensor for the detection of cysteine through competitive host-guest inclusion
    (Taylor and Francis Ltd., 2021) Mishra, Kirtika; Singh, Bachcha
    A ?-cyclodextrin (?-CD) inclusion complex containing L-cysteine (CYS) as a guest was prepared by freeze drying method. Formation of the inclusion complex was confirmed by powder X-ray diffraction pattern, Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The interaction between CYS and ?-CD was also analysed by conductivity measurement in aqueous solution. Thereafter, we developed a liquid crystal (LC)-based sensor system to detect CYS in aqueous solution following the principle of competitive host�guest inclusion. Here the guests sodium dodecyl sulphate (SDS) and CYS compete for the same hydrophobic cavity of host ?-CD. The dark optical image observed by polarising optical microscope confirms that CYS forms inclusion complex with ?-CD leaving SDS free which aligns LCs homeotropically. The constructed LC-based sensor could detect CYS up to 30��M in aqueous solution. Moreover the practical approach of this system was validated by sensing CYS in human serum. � 2020 Informa UK Limited, trading as Taylor & Francis Group.
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    Role of tannic acid in desiging of electrically active and magnetic gold nanoparticles and enhanced photovoltaic performance of gold@titania photoanode in DSSC
    (Elsevier Ltd, 2022) Gupta, Rashmi; Singh, Shalini; Srivastava, Pankaj; Singh, Bachcha
    We describe here in significance of tannic acid in obtaining size dependent electrochemically active and magnetic gold nanoparticles (GNPs). In this account, two types of GNPs (SCGNPs and SC-TAGNPs) were synthesized by using sodium citrate and sodium citrate-tannic acid as reducing agents, respectively. Highly monodispersed, uniformly distributed and small size GNPs were produced when tannic acid was used together with sodium citrate. SC-TAGNPs exhibited room temperature ferromagnetism while SCGNPs revealed diamagnetism. With higher anodic peak current and lower charge transfer resistance, the SC-TAGNPs exhibited better conductivity and electron transfer ability than SCGNPs. Mott-Schottky analysis revealed n-type semiconducting behavior of GC/SCGNPs & GC/SC-TAGNPs and showed positive shift in flat-band potential of GC/SC-TAGNPs compared to GC/SCGNPs suggesting better conductivity of SC-TAGNPs. Subsequently, SCGNPs and SC-TAGNPs were added to TiO2 nanoparticles to fabricate modified titania photoanodes (SCGNPs@TiO2 and SC-TAGNPs@TiO2) for dye-sensitized solar cells (DSSCs) application. With the use of TiO2, SCGNPs@TiO2 and SC-TAGNPs@TiO2 photoanodes, the short-circuit current density (JSC) was observed to be 2.18, 4.50 and 6.68 mA/cm2, while energy conversion efficiency (?) was found to be 0.75, 1.74 and 2.50%, respectively. The TiO2 photoanode employing SC-TAGNPs exhibited remarkably increased JSC and ? by ?48 and ?44%, respectively, then SCGNPs modified photoanode. � 2021 Elsevier B.V.