Sarada P. Mishra

A supercapacitor based on longitudinal unzipping of multi-walled carbon nanotubes for high temperature application

Multi-walled carbon nanotubes (MWCNTs) were partially unzipped longitudinally by a chemical method. Unzipped multi-walled carbon nanotubes (UZ-MWCNTs) were characterized by transmission electron microscopic analysis, X-ray diffraction and Raman spectroscopic analyses. UZ-MWCNTs were utilized for electrode preparation and the electrodes were used in the fabrication of a supercapacitor. At room temperature, the UZ-MWCNTs based supercapacitor showed a specific capacitance of ∼41 F g−1, while pristine MWCNTs based supercapacitor exhibited 22 F g−1 at the scan rate of 25 mV s−1. The increase in specific capacitance was attributed to an increase in effective specific surface area of UZ-MWCNTs due to partial unzipping. UZ-MWCNTs based supercapacitor exhibited an increase in specific capacitance with increase in temperature. It showed a specific capacitance of ∼74 F g−1 at 100 °C at the scan rate of 25 mV s−1, while the pristine MWCNTs based supercapacitor did not show any appreciable change in specific capacitance as a function of temperature. UZ-MWCNTs exhibited three-fold increase in specific capacitance as compared to pristine MWCNTs at 100 °C. Impedance spectroscopic analysis of the supercapacitors revealed that the UZ-MWCNTs based supercapacitor exhibited higher internal resistance and lower leakage resistance than pristine MWCNTs based supercapacitor. Continuous ‘charge–discharge’ cycling behaviour indicated that the UZ-MWCNTs based supercapacitor exhibited less stability during initial cycles even though it depicted higher specific capacitance as compared to the pristine MWCNTs based supercapacitor.

Synthesis and crystal structure of 2,3,12,13-tetraalkoxy-21, 23-dithiaporphyrinsElectronic supplementary information (ESI) available: 1H-NMR, LD-MS spectra and X-ray crystal structure data. See http://www.rsc.org/suppdata/cc/b2/b208017f/

21,23-Dithiaporphyrins with methoxy, butoxy, octyloxy and dodecyloxy substituents at beta-thiophene carbons were synthesised for the first time and the crystal structure of the butoxy derivative indicated that the substituents at the beta-thiophene carbons induce more planarity in the porphyrin ring.

Main chain photoresponsive liquid crystalline polymer synthesized through hydrosilylation

Liquid crystalline siloxane azo polymers were synthesized through hydrosilylation reaction between diallyl azo monomer and siloxane dihydride. The molecular weights of the polymers ranged from 3000–4000 g mol−1. The polymers were found to be soluble in chloroform, THF, DMF, DMSO, and DCM respectively. The photoresponsive behavior was studied during exposure of the polymers to UV radiation. The trans–cis photoisomerisation rate constants were also determined. The thermotropic behavior of the polymers was studied by using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The polymers exhibited liquid crystalline texture of nematic droplets in POM images existing at room temperature and extending over broad temperature range up to 155 °C. The DSC thermogram also supported the characteristic liquid crystalline transitions.