SINP Triennial Report - Saha Institute of Nuclear Physics

Biophysical Sciences Including Chemistry 9
these measurements will be improved from the present nanosecond to the picosecond level
to identify and characterize the photoinduced intermediates more precisely.
Transport and Electronic Properties of Conducting Polymers and Nanocomposites
A set of poly-3,4 ethylenedioxythiophene (PEDOT) samples were synthesized by varying
the oxidizing agent and its molar ratio with the monomer. The temperature dependence of
their conductivity is in excellent agreement with that in the model prescribed by Aharony
et al., which predicts a smooth crossover from the Coulomb-gap dominated variable-range
hopping (VRH) at low temperatures to Mott's 3d-VRH at high enough temperatures.
Electrical transport and magnetic properties of conducting polymer nanocomposites of
PEDOT and different ferrite (Fe 3 O 4 , NiFe 2 O 4 , CoFe 2 O 4 ) nanaoparticles were studied. The
samples were characterized by TEM, XRD and TGA. Electrical, thermal and crystalline
properties of the pure PEDOT were found to have improved after composite formation. In
the temperature range 77-300 K, dc resistivity data for pure PEDOT as well as all the
nancomposites fit well to the Mott VRH scaling relation, suggesting that the conduction
mechanism does not change on inclusion of nanoparticles. However, the hopping parameters
change in the nanocomposites. Magnetic study of ferrite nanoparticles and nanocomposites
show superparamagnetic blocking. A distribution of particle size and freezing of surface
spins are responsible for the difference of the temperature points TB (at the maximum of
MZFC) and TS (at the point of separation between MZFC and MFC).
Electrochemical properties of PEDOT based NiFe 2 O 4 conducting nanocomposites were
studied for their suitability as electrode materials for supercapacitor. Nanocrystalline nickel
ferrites (5-20 nm) have been synthesized by sol-gel method. Reverse micro emulsion
polymerization in n-hexane medium for PEDOT nanotube and aqueous miceller dispersion
polymerization for bulk PEDOT formation using different surfactants were adopted. Cyclic
voltammetry, galvanostatic charge-discharge and electrochemical impedance were used to
study charge transfer, ion diffusion and capacitance of the PEDOT composite samples in
an electrolyte containing 1M LiC l O 4 in acetonitrile. Highest specific capacitance for the
nanocomposites was found to be ~230 F/gm.
Nuclear and Radiochemistry:
The thrust of activity in this area has been in (i) accelerator based research and (ii) green
chemistry. A systematic study of production and separation of no-carrier-added radionuclides
by heavy ion activation has been carried out and alternative radionuclides with better
nuclear properties for clinical application have been proposed. Exotic projectiles like 9 Be
have been used to search for alternative production routes of longer-lived radionuclides
93,94,94m Tc and 219-211 At, which are termed 'ultimate radionuclides for targeted therapy'. The
cross-section data generated in these studies are regularly updated in the widely used IAEA
EXFOR database. Successful combination of green chemistry with radiochemical methods
of analysis has been achieved; preparation of radioactive gold and gold-palladium bimetallic
nanoparticles using minuscule amount of radioactivity and polyethylene glycol, an
environmentally benign chemical, has been reported for the first time. Contribution in
trans-disciplinary research areas has been made through development of a method of