A new easy method for preparation of high sensitive nanopolypyrrole chemical sensor using ultrasonic spray technique

Author(s): Mohammad Zaki Nemeh, Khaled Masri

In this paper we describe an easy method to deposit thin films from soluble Polypyrrole (Ppy) synthesizedby chemical polymerization using SDBS as surfactant. Ultrasonic spray technique was adopted to deposit these films, using a commercial domestic humidifier, on alumina substratescoated with two interdigitated electrodes, to be used as chemiresistor sensor. The obtained films were characterized by FTIR, X-ray diffraction, scanning electron microscope (SEM), and four point probe techniques. We also investigatedthe effect of polymerization time,molar ratios of Pyrrolemonomer to the oxidant (FeCl3) [Mo] / [Ox] on sensing property. X-ray diffraction pattern of Ppy with SDBS showed a shift of diffraction peak angle of about (2è = 11.46), relatively to pure Ppy, indicating that SDBS acted as a spacer between the conducting polymer chains, and induced a very high d-spacing comparing to the pure one. This has a positive impact on sensor sensitivity, as it makes more easily for analyte molecules to penetrate inside the films. Small peaks shifts were also observed between Ppy prepared with different molar ratios [Mo] / [Ox], indicating that the higher the molar ratio, the higherthe space between chains is. Conductivity measurements were made for the selected molar ratios. The best conductivity was 0.62(S/cm) corresponding to amolar ratio of 3. Finally, sensors showed a good sensitivity towardsmethanol and ethanolwhich could be explained by the high specific surface area and porosity as demonstrated by SEM images.

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