This is further aggravated by aqueous

immiscibility of pyrrole monomer which inhibits wetting of ZnO rods which might inhibit formation of uniform polypyrrole sheath. In the present case, the use of SDS anionic surfactant mitigates this by transporting pyrrole monomer to the surface of ZnO nanorods. A possible model of electropolymerization growth of PPy sheath over ZnO nanorods in the presence of SDS surfactant is shown schematically in Figure 5B. The SDS ionizes into Na + cation and CH3(CH2)11OSO3 – anion in aqueous medium. The SDS concentration used in this study is less than the critical value 8 mM for the first micelles concentration Ceritinib cell line HM781-36B clinical trial (CMC-1) hence the SDS molecular chain containing 12 carbon alkyls with sulfate group at the end are in the extended state in the aqueous medium [54, 55]. The dodecyl alkyl molecular chain being hydrophobic

orients away from water and this easily attaches on to the ZnO nanorod surface while the hydrophilic OSO3 – group project outward into aqueous environment. The pyrrole monomers are hydrophobic in character and sparingly soluble in water. A large number of pyrrole monomers are able to preferentially disperse within the hydrophobic region created by attached dodecyl alkyl molecular chain over ZnO nanorod surface [50]. This ensures uninhibited supply of the pyrrole monomer and dopant ClO4 – anions not across the exterior of ZnO nanorods [55] and consequently forming PPy layer over ZnO rods comprising of short-chain doped PPy oligomers by electronation-protonation-conjugation reaction

described in Figure 5B. Spatially distributed deposition of PPy oligomers as clusters is evident in the nodule like the microstructure study shown in Figure 2A. The pyrrole monomer availability during current pulsed off time is no longer diffusion-rate limited and efficient incursion of pyrrole results in the increased electropolymerization rates. In the subsequent pulse cycles, the electropolymerization is reinitiated over new ZnO surface sites or over PPy coated surface as shown schematically in Figure 5C resulting in homogenous formation of the PPy sheath over ZnO nanorods after a certain number of current pulsed polymerization cycles. Cyclic voltammetry study Figure 6A, B shows a set of CV plots recorded at slow scan rates of 5 and 10 mV.s-1 comparing the electrochemical performance of the ZnO nanorod core-PPy sheath electrode with the PPy nanotube structured electrodes obtained by etching ZnO nanorods for 2 and 4 h, respectively. All CV plots are nearly rectangular in shape, symmetrical across the zero current axis, and do not show any oxidation-reduction peaks demonstrating highly capacitive behavior.