Abstract
A highly sensitive NH3 gas sensor based on micrometer-sized polyaniline (PANI) spheres was successfully fabricated. The PANI microspheres were prepared via a facile in situ chemical oxidation polymerization in a polystyrene microsphere dispersion solution, resulting in a core–shell structure. The sensor response increased as the diameter of the microspheres increased. The PSt@PANI(4.5) sensor, which had microspheres with a 4.5 μm average diameter, showed the largest response value of 77 for 100 ppm dry NH3 gas at 30 °C, which was 20 times that of the PANI-deposited film-based sensor. Even considering measurement error, the calculated detection limit was 46 ppb. A possible reason for why high sensitivity was achieved is simply the use of micrometer-sized PANI spherical particles. This research succeeded in providing a new and simple technology for developing a high-sensitivity NH3 gas sensor that operates at room temperature.
Highlights
Spherical Polyaniline Particles.Ammonia (NH3 ) gas is a common air pollutant but is expected to be an important energy source in the coming hydrogen society [1,2]
This research succeeded in providing a new and simple technology for developing a high-sensitivity NH3 gas sensor that operates at room temperature
We report the results of a further improvement in sensitivity by preparing micrometer-order PANI spherical particles and investigating the effect of particle size on the NH3 gas sensing response
Summary
The sensing characteristics of a sensor prepared by drop-coating an insoluble PANI dispersion solution on a sensor substrate were insufficient for practical use This is because the formed film had a granular structure consisting of aggregated polyaniline chains, resulting in a dense film with poor gas diffusivity. Many so-called core–shell types of conducting polymers have been reported to improve processability and to coat particles [29,30,31,32,33] Among these spherical particles, we have chosen PANI-coated PS microspheres because polystyrene microspheres can be prepared via a free-radical-initiated polymerization method such as dispersion polymerization. We report the results of a further improvement in sensitivity by preparing micrometer-order PANI spherical particles and investigating the effect of particle size on the NH3 gas sensing response
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