Construction and evaluation of an optical pH sensor based on polyaniline-porous Vycor glass nanocomposite

This work describes the preparation of a polyaniline (Pani)-porous Vycor gl ass (PVG) nanocomposite and its use as sensing phase in an optical fibre pH sensor. Nanocomposites of Pani-PVG were prepared by in situ polymerisation of aniline absorbed inside the pores of a PVG (Corning 7930) with an avera ge porous size of 8 nm. The optical sensor was constructed by fixing a PVG slide onto a distal end of bifurcated optical fibre bundle, with a cyanoacr ylic resin. The sensor response was found to be reversible in the pH range from 5 to 12 and linear from pH 7.4 to 9.5. Response times of 4, 8 sand >16 min were obtained for slide thickness' of 0.5, 1 and 1.5 mm, respectively. Changes of temperature, ranging from 20 to 40 degreesC, showed minor effec t on the dynamic range. Similarly, the ionic strength (0.15, 0.30 and 0.50 mol 1(-1)) and the nature of the ions (NaCl, KCl and NaClO4) showed minor i nfluence on the sensor response. Leaching of Pani was not observed and the sensor lifetime was determined as being at least 5 months. These results in dicate that st Pani-PVG nanocomposite is suitable for the construction of o ptical pH sensors, with good analytical performance, since the glass slides can be prepared with good reproducibility and durability. (C) 2001 Elsevie r Science B.V. All rights reserved.