• KOMAL KHATI

      Articles written in Bulletin of Materials Science

    • Thermal and DC conducting behaviour of haemoglobin-doped polypyrrole

      SAMEENA MEHTAB M G H ZAIDI NIVEDITA RANA KOMAL KHATI SHUBHAM SHARMA

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      Doping of haemoglobin (Hb) into polypyrrole (PPy) has afforded polymer composites (PCs) with improved semiconducting behaviour with retained thermal stability. Process of doping was conducted through cationic surfactantassisteddilute polymerization of pyrrole (0.12 mol dl$^{-1}$) in the presence of ferric chloride oxidant (1.85${\times}$10$^{-2}$ mol dl$^{-1}$) supplemented with requisite weight fractions of Hb (10 and 20%; w/w). Physicochemical features of PCs were examined through diverse spectral, thermal and microscopic methods. Thermogravimetric analysis (TG) coupled with differential thermal analysis and differential thermogravimetry reveals two-step decomposition of PCs at common TG onset with Hb and PPy (200°C). Energy of activation and frequency of thermal degradation of Hb, PPy and related PCs have been evaluated and compared through Coats–Redfern (CR) and Horowitz–Metzger (HM) methods. CR method reveals substantial modification in free energy change of thermal degradation (${\Delta}$G, kJ mol$^{-1}$) of PCs (132.90) over PPy (13.09). Doping of Hb (20 wt%) has rendered shift in energy bandgap of PPy from 3.09 to 2.99 eV. Working electrodes (WEs) were derived from PCs in the presence of sulphonated polysulphone binder in graphite matrix and investigated for direct current conductivity (${\sigma}$DC) measurement under four-probe conditions at temperature range 313–373 K. Arrhenius plots reveal progressive trend in carrier activation energy (meV) of PCs ranging from 1.08 to 1.16 up to 20 wt% doping of Hb. The present study delivers a viable method of preparation of WE from Hb-doped PPy with sustained semiconducting behaviour up to 373 K.

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