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Conducting polypyrrole nanotubes are synthesized by an oxidation polymerization technique using an Anodisc alumina membrane as a template. The morphology is varied from solid rod-like structures to hollow tubes by changing the concentration of the ammonium persulphate (used as the oxidant) solution. The current distribution over the selected area of the membrane and the current–voltage (I–V) characteristics of a single nanotube have been investigated by atomic force microscopy. From the current distribution, the lowest wall thickness has been estimated to be and from the I–V characteristics it is seen that the intrinsic conductivity of the tube changes with the wall thickness. The conductivity for tubes with a wall thickness of has been calculated as .

In this study, pH sensors were successfully fabricated on a fluorine-doped tin oxide substrate and grown via hydrothermal methods for 8 h for pH sensing characteristics. The morphology was obtained by high-resolution scanning electron microscopy and showed randomly oriented flower-like nanostructures. The TiO2 nanoflower pH sensors were measured over a pH range of 2–12. Results showed a high sensitivity of the TiO2 nano-flowers pH sensor, 2.7 (μA)1/2/pH, and a linear relationship between IDS and pH (regression of 0.9991). The relationship between voltage reference and pH displayed a sensitivity of a 46 mV/pH and a linear regression of 0.9989. The experimental result indicated that a flower-like TiO2 nanostructure extended gate field effect transistor (EGFET) pH sensor effectively detected the pH value.

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