A dual-functional sensor based on PEDOT:PSS for sensing temperature and ammonia fabricated by electrohydrodynamic printing

Sensing temperature and ammonia is of importance for human production and quality of life. Here, we reported an integrated bimodal sensor with monitoring capability for temperature and ammonia based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). The sensing for temperature was achieved by utilizing the thermoelectric property of PEDOT:PSS and, an ordinal 1 M H₂SO₄ and then 1 M NaOH solution treatment method to improve the Seebeck coefficient, which is an important indicator for measuring temperature response performance. It was found that the acid treatment process effectively removed the PSS groups, while the base treatment deprotonated PEDOT, enhancing charge carrier mobility and thereby improving the Seebeck coefficient from 13.65 to 31.97 μV/K. Simultaneously, the resistance change was employed for ammonia sensing. Results showed that the FeCl₃ solution treatment method can increase the roughness of PEDOT:PSS films, enhance binding sites with ammonia, and improve sensitivity. Basing on these advancements, a bimodal sensor combining the temperature sensing module with the gas sensor was fabricated by electrohydrodynamic printing and spin-coating. The integrated sensor exhibits a really good sensing performance (generating a voltage of 13.88 mV under 115 K temperature difference and showing a response of 11.0% to 50 ppm ammonia) as well as good recoverability and repeatability. This work may provide a new route for fabricating multifunctional sensors for temperature and ammonia monitoring.