Dual-analyte spectroscopic sensing in sol-gel derived polyelectrolyte-silica composite thin films

Ferrozine (3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-p,p'-disulfonic acid, monosodium salt hydrate), an iron indicator, and HTPS (8-hydroxyl-1,3,6-pyr enetrisulfonic acid, trisodium salt), a pH indicator, were immobilized in s ol-gel derived PDMDAAC-SiO2 (where PDMDAAC stands for poly(dimethyldiallyla mmonium chloride), composite thin films via ion-exchange. The two indicator s were immobilized in two adjacent sections of the same PDMDAAC-SiO2 film w hich was supported on a glass optical substrate. The spectroscopic response of the film to both Fe2+ and H+ in solutions was investigated by attenuate d total reflection (ATR) spectrometry at two well-separated wavelengths, 56 2 nm for Fe2+ and 460 nm for H+. The Ferrozine/HPTS immobilized PDMDAAC-SiO 2 films had the following characteristics: linear range, 2.5 x 10(-6)-5.0 x 10(-5) M for Fe2+, pH 4.1-6.8 for H+; sensitivity, 2.2 x 10(4) Delta A/M f or Fe2+, 0.583 Delta A/pH for H+. (C) 1998 Published by Elsevier Science B. V. All rights reserved.