Organic thin films for optical gas sensing of nitrogen dioxide: comparisonof sol-gel and LB layers

4-Alkoxy-4'-(phenylazophenethyl) alcohol derivatives respond rapidly and re versibly at room temperature when exposed as thin films to nitrogen dioxide and interrogated by change of absorbance at 475 nm. The temperature depend ence of sensitivity is described by an Arrhenius activation energy. Values of activation energy obtained from a polymeric derivative deposited as a La ngmuir-Blodgett (LB) film and from a low molar-mass derivative trapped in a sol-gel matrix are all close to 0.6 eV, indicating that aggregation effect s are negligible, and that this figure represents a sterically-unhindered i nteraction between nitrogen dioxide and the azo chromophore. (C) 2000 Elsev ier Science S.A. All rights reserved.