Recognition of alcohol vapor molecules by simultaneous measurements of resistance changes on polypyrrole-based composite thin films and mass changes on a piezoelectric crystal

Abstract

A novel gas sensor is fabricated on the basis of simultaneous measurements of resistance changes on polypyrrole-based composite thin films and frequency changes on a piezoelectric crystal. Molecular species such as ethanol and methanol can be recognized by the (Δ R/Δ f) values, where Δ R and Δ f are the resistance and frequency change, respectively. The Δ R/Δ f value remaining constant at various concentrations of detected gases is a characteristic index of a given kind of vapor molecules. The Δ R/Δ f value can be modified by the introduction of inert materials, including poly(ethylene oxide) (PEO) and polyacrylonitrile (PAN), into the conducting polymer matrix. The higher the Δ R/Δ f value, the better is the recognition ability. The composite PPy/PEO (PEO=7 g/l) film exhibits the best recognition for alcohol vapor molecules among the investigated sensing films. Meanwhile, the quantitative analysis of the vapor molecules can be achieved by measuring the Δ R or Δ f values.