A room temperature functioning ammonia sensor utilising a bis-phenylalanine naphthalene diimide

An organic semiconductor, coded as NDI-A, comprising a naphthalene diimide core functionalised axially with phenylalanine derivatives has been evaluated for ammonia gas sensing at room temperature. A significant change in the current intensity of NDI-A-based sensor has been recorded upon exposure to ammonia with different concentrations (50, 25, 12.5, 6 and 2 ppm). The NDI-A-based sensor showed high sensitivity (66 %) towards 50 ppm ammonia, quick response and recovery (15.3 s and 32 s), low limit of detection (2 ppm). Promising features of high selectivity, good recyclability and stability were also evaluated. Importantly, the sensor exhibited excellent sensing performance at high humid environments with a response of 55 % towards 50 ppm ammonia at 90 % relative humidity. The high sensing performance of NDI-A sensor can be attributed to a number of factors, including the favourable morphology of the active film, containing random pores and voids, and design principles through the presence of-COOH groups which can effectively interact with ammonia through acid-base interactions.