Dr. Bikram Keshari Das

RESEARCH INTERESTS

Synthesis and development of Nano materials and its different applications.

Scopus Publications

Nanomaterials for sustainable water splitting towards green hydrogen production
Krushna Chandra Mandal, Tanushree Das, and Bikram Keshari Das
Informa UK Limited



Impact of strontium doping on the structural and NTCR properties of ZnO ceramics
Tanushree Das and Bikram Keshari Das
Springer Science and Business Media LLC



Impedance spectroscopy and conduction mechanism of Zn<inf>1-x</inf>Mg<inf>x</inf>O NTCR ceramics
Tanushree Das, Dipteerekha Das, and Bikram Keshari Das
Elsevier BV



Negative temperature co-efficient of resistance behaviour of Cr doped ZnO nanoceramics
Bikram Keshari Das, Tanushree Das, Dipteerekha Das, Kajal Parashar, S.K.S. Parashar, Rajeev Kumar, A.V. Anupama, and Balaram Sahoo
Elsevier BV



Influence of Mg doping on structural, dielectric properties and Urbach energy in ZnO ceramics
Tanushree Das, Dipteerekha Das, Kajal Parashar, S. K. S. Parashar, A. V. Anupama, Balaram Sahoo, and Bikram Keshari Das
Springer Science and Business Media LLC



Complex modulus spectroscopy of Zn1-xSr<inf>x</inf>O nanoceramics
Tanushree Das, Dipteerekha Das, Kajal Parashar, S. K. S. Parashar, and Bikram Keshari Das
AIP Publishing



Structural and electrical properties of mechanically alloyed ZnO nanoceramic for NTC thermistor application
Bikram Keshari Das, Tanushree Das, and Dipteerekha Das
Springer Science and Business Media LLC



Structural, optical and NTCR properties of Ca doped ZnO ceramics
Tanushree Das, Bikram Keshari Das, Dipteerekha Das, Kajal Parashar, S. K. S. Parashar, A. V. Anupama, and Balaram Sahoo
Springer Science and Business Media LLC



Effect of Cr Doping on Structural, Optical and Dielectric Properties of ZnO Nanoceramics Synthesized by Mechanical Alloying
Bikram Keshari Das, Tanushree Das, Kajal Parashar, S. K. S. Parashar, Rajeev Kumar, A. V. Anupama, and Balaram Sahoo
Springer Science and Business Media LLC
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Altered electrical properties with controlled copper doping in ZnO nanoparticles infers their cytotoxicity in macrophages by ROS induction and apoptosis
Bikram Keshari Das, Suresh K. Verma, Tanushree Das, Pritam Kumar Panda, Kajal Parashar, Mrutyunjay Suar, and S.K.S. Parashar
Elsevier BV
The present study reports the regulation of cytotoxicity of Cu doped ZnO nanoparticles in macrophages (RAW 264.7) due to altered physiochemical properties changes like electrical properties by controlled doping of Cu in ZnO. Cu-doped ZnO nanoparticles were prepared by High Energy Ball Milling technique (HEBM) and formed single phase Zn1-xCuxO (x = 0.0, 0.01, 0.02, 0.03) were called as pure ZnO, Cu1%, 2%, 3% respectively. Hexagonal wurtzite structure with size range of 22-26 nm was verified. FE-SEM with EDX analysis indicated the Cu doping effect on the surface morphology of ZnO. Zeta potential of Zn1-xCuxO was found to be elevated with increase in doping percentage of Cu (-36.6 mV to +18.2 mV). Dielectric constant was found to be decreased with increasing doping percentage. Increase in doping percentage enhanced cytotoxicity of Zn1-xCuxO in macrophages with LC50 of 62 μg/ml, 51 μg/ml, 40 μg/ml, 32 μg/ml. Granularity change of macrophages suggested doping influenced cellular uptake as consequence of zeta potential and dielectric properties changes. 3% Cu doped ZnO shown a higher ROS signal and apoptosis than 2% and 1% Cu doping with exhibition of ROS scavenging nature leading to apoptosis of prepared Cu doped ZnO nanoparticles. Our findings revealed mechanism of cytotoxicity of Zn1-xCuxO as a consequence of alteration in electric properties eliciting ROS scavenging leading to higher apoptosis with increasing doping percentage of Cu in ZnO.


Investigation of structural, morphological and NTCR behaviour of Cu-doped ZnO nanoceramics synthesized by high energy ball milling
Bikram Keshari Das, Tanushree Das, Kajal Parashar, S.K.S. Parashar, Rajeev Kumar, Harish K. Choudhary, Vijay B. Khopkar, A.V. Anupama, and Balaram Sahoo
Elsevier BV
Abstract Nanocrystalline Cu doped ZnO (Zn1-xCuxO, x = 0, 0.01, 0.02, 0.03 and 0.04) samples were synthesized by high energy ball milling technique (HEBM). The strain developed during ball milling and incorporation of Cu into the Zn-site in ZnO lattice is depicted as broadening of the full width at half maximum (FWHM) of the XRD. The X-ray diffraction peak-widths (FWHM) increases with increase in Cu-concentration. Furthermore, the mechanical impact and the heat produced during ball milling helps in the formation of aggregates. The size of these aggregates was observed to increase with Cu-concentration. Upon calcination, these aggregated structures form particle, resulting in bigger particles for higher concentration of Cu. The XRD results confirm that up to ∼3 at% of Cu can be doped in ZnO lattice, beyond which CuO precipitates. The impedance spectroscopy and the ac-conductivity results confirm the improvement in dielectric properties of ZnO by Cu doping. The decrease in magnitude of Z′ on increase in temperature confirms the negative temperature coefficient of resistance (NTCR) behaviour of the samples. The ac conductivity of ZnO decreases with Cu doping and follows the correlated barrier hopping (CBH) model in the investigated temperature and frequency range.


Structural, bandgap tuning and electrical properties of Cu doped ZnO nanoparticles synthesized by mechanical alloying
Bikram Keshari Das, Tanushree Das, Kajal Parashar, Arun Thirumurugan, and S. K. S. Parashar
Springer Science and Business Media LLC
Cu doped ZnO nanoparticles abbreviated as Zn1−xCuxO (x = 0, 0.01 and 0.03) were synthesized by mechanical alloying. The change in structure, morphology, band gap and dielectric properties of the synthesized nanoparticles were investigated by XRD, FE-SEM, FTIR, UV–Vis and impedance analyzer respectively. The incorporation of the dopant Cu into ZnO hexagonal wurtzite structure has been verified by X-ray diffraction (XRD) and the Cu doping on the structural bonding of ZnO has been verified by fourier transformation infrared spectra (FTIR).The XRD spectra shows that all the synthesized nanoparticles are single phase, hexagonal wurtzite structure and belong to the space group of P63mc.Crystallite size of Cu doped ZnO (15 nm) nanoparticles is smaller than pure ZnO (18 nm) and peak broadening exists in the system. FE-SEM analysis indicates that Cu doping affects the surface morphology of ZnO. The band gap (Eg) of ZnO decreases with Cu doping which can be attributed to sp-d exchange interaction between the ZnO band electrons and localized d electrons of Cu2+ ions. The dielectric constant of ZnO decreases with Cu doping.


Effect of Sr-doping on sinterability, morphology, structure, photocatalytic activity and AC conductivity of ZnO ceramics
T. Das, B. K. Das, K. Parashar, R. Kumar, H. K. Choudhary, A. V. Anupama, B. Sahoo, P. K. Sahoo, and S. K. S. Parashar
Springer Science and Business Media LLC
The change in morphology, structure, catalytic activity and ac electrical conductivity of the Sr-doped ZnO (Zn1−xSrxO, x = 0, 0.01, 0.02 and 0.03) ceramic powders was investigated after sintering. The sintering of the Sr-doped samples results in faster growth in particle-size and the shape becomes spherical by dissolution of the sharp edges in order to reduce the strain produced by Sr-doping and to reduce the surface energy. The growth in particle-size reduces the photocatalytic activity. Sr-doping reduces the band gap of ZnO by a small value (~0.1 eV). The ac conductivity values decrease with increase in Sr-concentration, but increase with temperature and frequency. This behavior is due to the conduction by small polarons created by Sr-doping. Our results may facilitate a way for the easy fabrication of monolithic ZnO based devices with improved dielectric and semiconducting properties of ZnO ceramics by doping a small amount of Sr.


Impact of divalent dopant Ca²⁺ on the electrical properties of ZnO by impedance spectroscopy
TANUSHREE DAS, BIKRAM KESHARI DAS, S K S PARASHAR, and KAJAL PARASHAR
Springer Science and Business Media LLC
The electrical properties of Zn1−xCaxO (x = 0, 0.01, 0.02 and 0.03) nanoceramics synthesized by solid-state reaction method were investigated by complex impedance spectroscopy (CIS) from room temperature to 500∘C. Structural analysis of the synthesized material using the X-ray diffraction technique suggests that they exhibit a single phase with hexagonal wurtzite structure. Experimental results indicate that the synthesized material shows temperature-dependent relaxation phenomena. The variation of frequency exponent (s) with temperature shows the presence of thermally activated polarization mechanism in the synthesized sample. Dielectric constant was found to decrease with increase in frequency and temperature for Ca-doped samples. Ca-doped ZnO sample shows dielectric loss at lower temperature than that of pure ZnO.


Structural, optical and dielectric study of Cu doped ZnO nanoparticles synthesised by high energy ball milling
Bikram Keshari Das, Tanushree Das, Kajal Parashar, and S.K.S. Parashar
Inderscience Publishers



Temperature and frequency dependence electrical properties of Zn<inf>1-x</inf>Ca<inf>x</inf>O nanoceramic
T. Das, B.K. Das, K. Parashar, and S.K.S. Parashar
Institute of Physics, Polish Academy of Sciences
This work reports the temperature and frequency dependence electrical properties of Ca doped ZnO (Zn1−xCaxO, x = 0.01) nanoceramic synthesized by solid state reaction method. The X-ray spectra show that the synthesized powder has hexagonal wurtzite structure with space group P63mc. The average crystallite size decreases with Ca doping. The increase in oxygen positional parameter (u) indicates lattice distortion in the crystal structure. Doping with Ca caused a slight shift in the (101) plane peak towards lower diffraction angle. The formation of pores in field emission scanning electron microscopy micrograph may be due to the defect created by Ca substitution. The electrical property was investigated by impedance spectroscopy in the temperature range 300–500 ◦C. The synthesized sample shows temperature dependence relaxation phenomena and negative temperature coefficient of resistance effects. Electrical conductivity (σac) increases with increase in temperature as well as with frequency due to the drift mobility of electrons and hole by hopping conduction. Dielectric constant was found to decrease with increase in frequency and temperature. This decreases drastically in the magnitude of approximately <10 times than the corresponding undoped one.


Structural, electrical and FT-IR studies of nano Zn<inf>1-x</inf> Ca<inf>x</inf> O by solid state reaction method
Tanushree Das, Bikram Keshari Das, Kajal Parashar, S.K.S. Parashar, and Rao Alluri Nagamalleswara
Trans Tech Publications, Ltd.
Single phase polycrystalline with = 0, 0.01 and 0.02 were synthesized by conventional solid state reaction method. The X-ray diffraction shows that the ceramic samples has hexagonal Wurtzite structure with a space group of p63mc and average crystallite size in the range 52 - 88 nm. The dielectric and electrical properties were studied within the temperature range 30 °C to 500 °C under air atmosphere as function of frequency (10 kHz). The electrical properties of grain interior and grain boundary have been studied by using the impedance spectroscopy and follow the non-Debye relaxation process. It was observed that the AC conductivity of ceramic samples following the Universal power law within the frequency range 1kHz to 1 MHz. The activation energy of Pure is 0.29 eV was calculated by using the Arrhenius-relation with in temperature range 300 - 500 °C, which is increased to (0.40 eV ) when = 0.02 of at 10 kHz . The peaks attributed at 1415 cm-1 () and 1413 cm-1 () in FT-IR measurement of are due to Ca-O stretching from the calcite phase of CaCO3, which is not observed in Pure ZnO confirms the presence of Ca in ZnO lattice. Keywords: , FT-IR, Impedance spectroscopy, ac conductivity, Dielectric constant.