Template-free synthesis of a wafer-sized polyaniline nanoscale film with high electrical conductivity for trace ammonia gas sensing

Abstract

Ammonia gas, as an air pollutant, chemical raw material, marker of kidney disease and explosive, widely exists in our daily life. It is a key challenge and of great significance to develop sensors for the detection of ammonia gas with a wide detection range and low detection limit down to the ppb level. With a template-free gas diffusion method at the air–water interface, we presented the synthesis of nanoscale thin films of highly ordered polyaniline with a lateral size of ∼60 cm² and electrical conductivity of ∼250 S cm⁻¹. The film could be transferred onto arbitrary substrates. Onto a flexile interdigital electrode, flexible sensors for the detection of ammonia gas were created. The detection range is between 2 ppb and 100 ppm, and the response to 100 ppm of ammonia gas at room temperature is 19.46 with a response time of only 26 seconds. A color change test paper for the detection of ammonia gas was developed and applied to monitor the freshness of shrimp. This study will inspire the creation of highly ordered nanoscale thin films of organic polymers, and promote their applications as sensors.