A chemiresistive room temperature ammonia gas sensor based on self-assembled PPy/Zntpp

There is an increasing demand for monitoring ammonia in livestock farming, which can prevent livestock products from being contaminated by bacteria and viruses. As a prospective material for resistive sensors, polypyrrole (PPy) still suffers from low sensitivity and poor selectivity. Herein, zinc-tetra(p-sulfonylphenyl) porphyrin (Zntpp) particles are anchored on the PPy network by a one-step mild electrodeposition route to form a resistive sensor with the wrinkle-like nanostructure. The optimal PPy/Zntpp (Pzt) sensor demonstrates an outstanding response value of 104.3 % toward ammonia with a response/recovery time of 42/223 s, compared with that of PPy (7.2 % in response and 47/230 s). The durability and stabilities have been explored, and the limit of detection for Pzt is calculated to be similar to 8.63 ppm, which enables trace ammonia in livestock farming. Additionally, the sensing mechanism can be attributed to the p-n heterojunction. Furthermore, a wireless sensor device that consists of a Pzt sensory unit, a microcomputer, and a Bluetooth module is assembled, and the concentration information can be read precisely in real-time by a smartphone, indicating the great application prospects in the field of livestock farming.