Color Control in π-Conjugated Organic Polymers for Use in Electrochromic Devices

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

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Gas Sensors Based on Conducting Polymers

Polymers in sensor applications

Conducting polymers in chemical sensors and arrays

Electrochromics for smart windows: Oxide-based thin films and devices

Polyaniline (PANI) shows electrical as well as optical property changes when it is in contact with oxidant/reductor gas. In this work, the optical transmittance changes in PANI coatings originated by their exposure to the ammonia gas were detected by a nulling optical transmittance bridge. The adsorption and desorption curves were carefully analysed using Langmuir kinetic theory for the adsorption of ammonia gas on PANI single and PANI–PMMA composite coatings. Because of the inhomogeneous nature of the PANI film surface adsorption isotherms were the best described by Freundlich model. From the numerical fitting equations it is suggested that there may be two energetically different adsorption sites on the PANI surface for NH 3 molecules, which corroborates with the no-uniform positive charge distribution on the nitrogen atoms of the PANI backbone chains. The activation energy of adsorption and the heat of adsorption were estimated to be about 0.3–0.5 eV at a NH 3 gas concentration of 10–1000 ppm.

Adsorption kinetics of optochemical NH3 gas sensing with semiconductor polyaniline films

Synthesis of derivatives of polythiophene and their application in an electrochromic device

Polyaniline (PANI) is a π-conjugated polymer that shows electric and optical property changes, when it is in contact with oxidant/reductor chemicals. In particular, the interaction between the conductive form of PANI, the emeraldine salt (ES), and the NH 3 gas results in a decrease of the polaron densities inside the band gap of the organic material. In this work, the optical-transmittance changes detected in PANI coatings as a function of the sensing ammonia gas concentrations are studied by using a nulling optical-transmittance bridge with a 632 nm laser (He–Ne) source, which allows a sensitive monitoring of optical property changes. It is observed that the conductive PANI–polymethyl methacrylate (PMMA) composite coatings are sensitive for very low concentrations of HN 3 (from ∼10 to 4000 ppm, depending on the PANI films’ electrical conductivity), and their optical response is reversible as the reduction gas is removed by N 2 .

Hailin Zhao Hu

Papers

Adsorption kinetics of optochemical NH3 gas sensing with semiconductor polyaniline films

Synthesis of derivatives of polythiophene and their application in an electrochromic device

Polyaniline composite coatings interrogated by a nulling optical-transmittance bridge for sensing low concentrations of ammonia gas

Fourier transform infrared spectroscopy studies of the reaction between polyacrylic acid and metal oxides

Fourier transform infrared spectroscopy studies of polypyrrole composite coatings