Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
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224 <strong>Biennial</strong> <strong>Report</strong> <strong>2005</strong>-076.1.8 Conducting Polymer/Nanocomposite6.1.8.1 PEDOT-DBSA-Fe 3 O 4 Conducting Nanocomposite: Preparation and Characterizationand Magnetic PropertiesSynthesis and characterization <strong>of</strong> a new nanocomposite involving PEDOT (Poly 3,4-ethylenedioxythiophene)and Fe 3 O 4 nanoparticles are described. The aim is to obtain a nanocomposite wherethe conducting properties <strong>of</strong> PEDOT can be combined with the magnetic properties <strong>of</strong> ferros<strong>of</strong>erricoxide (Fe 3 O 4 ). Fe 3 O 4 nanoparticles were synthesized by alkaline hydrolysis <strong>of</strong> a mixture <strong>of</strong> ferrousand ferric salts. Nanocomposite samples <strong>of</strong> varying proportions <strong>of</strong> inorganic and organic componentswere synthesized by adding EDOT monomer stabilized in miceller solution <strong>of</strong> sodium salt<strong>of</strong> DBSA (dodecylbenzene sulphonic acid) to aqueous colloidal dispersion <strong>of</strong> Fe 3 O 4 nanoparticlesfollowed by oxidative polymerization using APS. Dark blue colored nanocomposite remained in thedispersed phase. Nanocomposite samples were isolated in the solid state by adding ethanol. Roomtemperature DC conductivity <strong>of</strong> the samples are <strong>of</strong> the order <strong>of</strong> ∼ 10 −3 S/cm. TEM photographs<strong>of</strong> Fe 3 O 4 showed presence <strong>of</strong> distinct spherical naonparticles in the diameter range 20-40 nm andthose <strong>of</strong> nanocomposite samples show that oxide particles are incorporated in the polymer chain.Electrical, thermal and crystalline properties <strong>of</strong> the pure PEDOT have improved after compositeformation. Electrical transport and magnetic properties <strong>of</strong> the materials were studied.Amitabha De, Pintu Sen, A Das, A PoddarCSD6.1.8.2 Smooth crossover from variable-range hopping with Coulomb gap to nearestneighborinterchain hopping in conducting polymersThe temperature dependence <strong>of</strong> the conductivity <strong>of</strong> a set <strong>of</strong> poly-3,4 ethylenedioxythiophene samplessynthesized by varying the oxidizing agent and its molar ratio with the monomer is in excellentagreement with that in the model prescribed by Aharony et al. Phys. Rev. Lett. 68, 39001992, which predicts a smooth crossover from the Coulomb-gap dominated variable-range hoppingVRH at low temperatures to the Mott three-dimensional-VRH at high-enough temperatures. Inthe temperature regime <strong>of</strong> such crossover, it takes the form log T- 1/3 , which is attributed to thenearest-neighbor interchain hopping characteristic <strong>of</strong> short average conjugation length.Sanjib Maji, Soumik Mukhopadhyay, R Gangopadhyay, Amitabha DeCSD6.1.8.3 Synthesis and Electronic properties <strong>of</strong> Disordered NanowiresNanowire fabrication by template based synthesis technique has been demonstrated. Conductingpolymer nanowires were synthesized using both chemical and electrochemical method. Electronictransport properties <strong>of</strong> these nanowires were demonstrated which strongly depends on the synthesiscondition. Electro-chemically synthesized sample shows higher conductivity. The current-voltagecharacteristics shows a power-law behavior at low temperature. Differential conductance showsincrease in zero bias conductance with increasing diameter and also with increasing temperature.These results indicate significance <strong>of</strong> electron-electron and electron-phonon interaction in determin-
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