We report on the electrolytic gating of α-sexithiophene thin film transistors, in which the organic semiconductor is in direct contact with an electrolyte. Due to the large capacitance of the electrical double layer at the electrolyte/semiconductor interface, modulation of the channel conductivity via an electrical field effect is achieved at low voltages. The transistors are stable for several hours and are sensitive to variations in the pH resulting from a pH-dependent surface charge, which modulates the threshold voltage. The response to different ion concentrations is described by the influence of the ions on the mobility and an electrostatic screening effect.

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Summary Emeraldine salt of polyaniline‐coated copper substrate was used as a cathode to study hydrogen evolution reaction in 1M H2SO4. Hydrogen evolution reaction in acidic medium followed Grotthus mechanism, where proton hops randomly on the surface of polyaniline. With Randles‐Sevcik equation, the average value of diffusion coefficient for H+ on polyaniline was calculated to be 2.66 times higher than that in the literature data. This higher value explicitly supported the rapid diffusion of H+ on polyaniline surface from the bulk electrolyte solution. With the help of a phenomenological thermodynamic approach demonstrated elsewhere, the solvent‐modified work function of polyaniline‐coated copper in acidic medium was calculated. The plot of exchange current density versus solvent‐modified work function of different metals and polyaniline‐coated copper indicated that at lower work function polyaniline‐coated copper showed higher exchange current density and the rate of hydrogen evolution was much higher on polyaniline‐coated copper than on copper. This was further confirmed by gas chromatography, and 13C and 1H nuclear magnetic resonance studies supported the mechanism proposed. From linear sweep voltammetry analysis, it was observed that the total capacity of hydrogen stored on polyaniline‐coated copper was approximately 1.85 times higher than that on copper.

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Abstract-The paper presents the electromagnetic (EM) wave propagation in cylindrical optical fibers with helical windings under slow-and fast-wave considerations. Field components are deduced for both the cases, and also, the dispersion relations are obtained by applying the boundary conditions, as modified by the presence of conducting helical windings. Two special cases are considered corresponding to the values of the helical pitch angle as 0 • and 90 • . A comparison of the dispersion relations is presented.

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