A room temperature ammonia gas sensor based on cellulose/TiO2/PANI composite nanofibers

• We report a facile approach to prepare cellulose/TiO2/PANI composite nanofibers that involves P–N heterojunctions.
• The response values and sensitivity of cellulose/TiO2/PANI were much higher than those of cellulose/PANI composite nanofibers.
• Enhanced sensing was obtained due to the P–N heterojunctions whose depletion layer would be widened when the sensor was exposed to ammonia.

We report a facile approach to prepare cellulose/titanium dioxide/polyaniline (cellulose/TiO2/PANI) composite nanofibers that involves P–N heterojunctions at the interface of p-type PANI and n-type TiO2. This work found that the P–N heterojunctions could improve ammonia sensing properties of the prepared nanofibers. Electrospun cellulose acetate nanofibers were deacetylated to prepare regenerated cellulose nanofibers, and then the obtained cellulose nanofibers were immersed into TiO2 sol to adsorb TiO2 nanoparticles onto the surface of them to fabricate cellulose/TiO2 composite nanofibers. In-situ polymerization of aniline was utilized to deposit PANI on the surface of cellulose/TiO2 composite nanofibers. The gas sensing properties of the prepared nanofibers were evaluated by a home-made test system. The cellulose/TiO2/PANI and cellulose/PANI composite nanofibers were exposed to 10, 30, 50, 100, 150, 200 and 250 ppm ammonia vapor at room temperature, respectively. It was found that the response values and sensitivity of cellulose/TiO2/PANI were much higher than those of cellulose/PANI composite nanofibers. Enhanced sensing was obtained by cellulose/TiO2/PANI due to the P–N heterojunctions whose depletion layer would be widened when the composite nanofibers were exposed to ammonia, resulting in their resistance increased dramatically.

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