Browsing by Author "Mahapatra,S.K."

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Effect of plasma power on reduction of printable graphene oxide thin films on flexible substrates
(IOPscience, 2018) Banerjee, Indrani; Mahapatra,S.K.; Pal, Chandana; Sharma, Ashwani K; Ray, Asim
Room temperature hydrogen plasma treatment on solution processed 300 nm graphene oxide (GO) films on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates has been performed by varying the plasma power between 20 W and 60 W at a constant exposure time of 30 min with a view to examining the effect of plasma power on reduction of GO. X-ray powder diffraction (XRD) and Raman spectroscopic studies show that high energy hydrogen species generated in the plasma assist fast exfoliation of the oxygenated functional groups present in the GO samples. Significant decrease in the optical band gap is observed from 4.1 eV for untreated samples to 0.5 eV for 60 W plasma treated samples. The conductivity of the films treated with 60 W plasma power is estimated to be six orders of magnitude greater than untreated GO films and this enhancement of conductivity on plasma reduction has been interpreted in terms of UV-visible absorption spectra and density functional based first principle computational calculations. Plasma reduction of GO/ITO/PET structures can be used for efficiently tuning the electrical and optical properties of reduced graphene oxide (rGO) for flexible electronics applications.
Synthesis and dielectric characterisation of triiodide perovskite methylammonium lead iodide for energy applications
(Springer, 2018) Mahapatra,S.K.; Saykar, N.; Banerjee, Indrani; Hobson, P.R.; Sharma, A.K.; Ray, A.K.
Impedance spectroscopic measurements on spin coated 550 nm thick perovskite films sandwiched between titanium oxide (TiO2) deposited on fluorine doped tin oxide (FTO) glass substrates and with a platinum (Pt) counter electrode have been performed to determine the influence of the percentage of PbI2 in methylammonium lead iodide (CH3NH3PbI3) compounds. These compounds with perovskite structure have been synthesized by weaving methylammonium iodide (CH3NH3I) and lead iodide (PbI2) in two different weight ratios of 1:4 and 3:7. The surface grains are found from the scanning electron microscoping images to have become relatively larger with increasing PbI2 content in spincoated perovskite film. Nearly 2% increase in optical band gap has been observed with increasing weight ratio of PbI2 content from 1:4 to 3:7.
Synthesis of NiO-Co3O4 nanosheet and its temperature-dependent supercapacitive behavior
(IOPscience, 2018) Saykar, Nilesh G; Pilania, Ritu Kumari; Banerjee, Indrani; Mahapatra,S.K.
A nanosheet of nickel and cobalt double hydroxides (NC RT) has been synthesized by the facile hydrothermal method. It has been treated at temperatures of 300 °C, 400 °C and 500 °C, namely NC 300, NC 400 and NC 500, respectively, to obtain a nanosheet of NiO °Co3O4. Samples have been investigated using XRD, Raman spectroscopy, FESEM and TEM. It can be observed that nickel hydroxide is converted to NiO at 300 °C, whereas cobalt hydroxide is converted to Co3O4 at 400 °C. The double hydroxide nanosheet leads to porous oxide nanosheet at an elevated temperature. The formation of porous structure could be attributed to the rapid release of water molecules during thermal treatment. Four symmetric supercapacitors are prepared with NC RT, NC 300, NC 400 and NC 500 as electrode materials, keeping 3 M KOH as an electrolyte and Whatman filter paper as a separator for all the symmetric supercapacitors. It can be seen that the specific capacitances of the NC RT, NC 300, NC 400 and NC 500 symmetric supercapacitors are decreased with increasing temperature in the range of 25 °C °80 °C and scan rate in the range of 10 °500 mV s−1. It can be seen that the NC 300 has excellent supercapacitive behavior. The specific capacitance of NC RT decreased from 20 to 6 F g−1, NC 300 decreased from 324 to 57 F g−1, NC 400 decreased from 132 to 61 F g−1 and NC 500 decreased from 81 to 48 F g−1 with the variation of scan rate from 10 °500 mV −1. The decrement in the specific capacitance may be attributed to the increased bulk and charge transfer resistance at elevated temperature.