Abstract
Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as the sensitive layer of conductimetric gas sensors because of their conducting properties. An important advantage of polymer-based gas sensors is their efficiency at room temperature. This characteristic is interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures (300–400 °C). Consequently, polymer-based gas sensors are playing a growing role in the improvement of public health and environment control because they can lead to gas sensors operating with rapid detection, high sensitivity, small size, and specificity in atmospheric conditions. In this review, the recent advances in electrodeposited polymer-based gas sensors are summarized and discussed. It is shown that the sensing characteristics of electrodeposited polymers can be improved by chemical functionalization, nanostructuration, or mixing with other functional materials to form composites or hybrid materials.
Highlights
Conducting polymers, such as polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), and their derivatives, have been used as the active layer of gas sensors since the early 1980s [1].Conducting polymers have many interesting characteristics for sensing including their high sensitivity and short response time; especially, these features are ensured at room temperature
The main parameter used to adjust the efficiency of these sensing materials is the nature of the dopant. Most of these works have been dedicated to the development of gas sensors based on polypyrrole or polyaniline films for the detection of ammonia or volatile organic compounds (VOCs) even if some other gases have been studied such as CO2 for example [27] (Table 1)
An attempt has been made to present an overview on the prospects of electrodeposited polymers in gas sensors, recently reported, and to outline some of their latest advances
Summary
Conducting polymers, such as polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), and their derivatives, have been used as the active layer of gas sensors since the early 1980s [1]. To extend the functions or to improve their performances, electrodeposited polymers are frequently mixed with other functional materials such as organic compounds [2], metal nanoparticles [3], metal oxide nanoparticles [4], or carbon nanotubes [5] to form composites with improved sensing properties Their molecular chain structure can be modified conveniently by copolymerization or structural derivations. An analyte recognition process takes place followed by the conversion of chemical information into an electrical signal For incorporation into these chemical sensors, an advantage of polymers is that sensory devices can be fabricated from these materials on electrodes by electrochemical polymerization from an electrolyte solution. Polymer-based gas sensors are interesting for environmental pollution monitoring because, upon exposure to vapor, the polymers show rapid conductivity changes, which are generally reversible, at room or atmospheric temperature These characteristics are interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures. Rather than giving a long list of references, it was decided to focus on some original and interesting examples for each type of sensing material in order to highlight the most promising strategies used to improve the sensing properties
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