Krishanu Chatterjee

Reduced graphene oxide-polyaniline composites—synthesis, characterization and optimization for thermoelectric applications

Reduced graphene oxide (rGO) can improve the thermoelectric properties of polyaniline (PANI) by varying its concentration in composites of rGO nanosheets and PANI. The figure of merit (ZT) of rGO–PANI composites is increased with an increasing percentage of rGO (up to 50%), which is 7.5 times higher as compared to pure PANI. High resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analyses show a uniform growth of PANI over the surface of rGO as a template, leading to a more ordered structure with high crystallinity during polymerization. Compared to pure PANI, both the electrical conductivity and thermoelectric power of the rGO–PANI composite is higher due to the increased carrier mobility as confirmed by a Hall effect measurement. Fourier transform infrared spectroscopy (FTIR), ultra-violet visible range spectroscopy (UV-Vis) and Raman spectroscopy analyses reveal that strong π–π interactions assisted the uniform distribution of PANI on the rGO nanosheets. Other strong interactions include electrostatic forces and hydrogen bonding between rGO and PANI, which provide a route for constructing highly ordered chain structures with improved thermoelectric performance of PANI. There is no significant change in the thermal conductivity of the rGO–PANI composite as compared to pure PANI, which improves the thermoelectric performance of composite.

Synthesis, characterization and enhanced thermoelectric performance of structurally ordered cable-like novel polyaniline–bismuth telluride nanocomposite

Bismuth telluride (Bi₂Te₃) nanorods and polyaniline (PANI) nanoparticles have been synthesized by employing solvothermal and chemical oxidative processes, respectively. Nanocomposites, comprising structurally ordered PANI preferentially grown along the surface of a Bi₂Te₃ nanorods template, are synthesized using in situ polymerization. X-ray powder diffraction, UV-vis and Raman spectral analysis confirm the highly ordered chain structure of PANI on Bi₂Te₃ nanorods, leading to a higher extent of doping, higher chain mobility and enhancement of the thermoelectric performance. Above 380 K, the PANI-Bi₂Te₃ nanocomposite with a core-shell/cable-like structure exhibits a higher thermoelectric power factor than either pure PANI or Bi₂Te₃. At room temperature the thermal conductivity of the composite is lower than that of its pure constituents, due to selective phonon scattering by the nanointerfaces designed in the PANI-Bi₂Te₃ nanocable structures. The figure of merit of the nanocomposite at room temperature is comparable to the values reported in the literature for bulk polymer-based composite thermoelectric materials.