Facile, Low‐Cost and Flexible Ammonia Sensor Arrays Based on Metallic Ion Charge Carriers and Polymer Matrices

Abstract With the development of industrial and medical technology, chemical sensors based on electron charge carriers are difficult to meet the upping requirements on excellent sensitivity, good selectivity, and portability. Herein, a new type of sensing material is developed via facile preparation method. Metal ions, instead of electrons, are used as charge carriers and distributed in the polymer matrix. As a representative, the ionic conductive gas sensor based on polyacrylic acid and copper ions (PAA‐Cu(II)) is fabricated. The PAA‐Cu(II) sensor exhibits excellent linear response to ammonia (NH₃), together with high sensitivity (50.3% for 50 ppm NH₃), good selectivity, and fast response/recovery time (10/10.5 s). The sensor also displays high transparency, long‐term air stability, and excellent flexibility. In addition, sensor arrays based on various metal ions (Cu²⁺, Co²⁺, Ni²⁺, Ag⁺, Fe³⁺, Mg²⁺) and polymers (polyacrylic acid, polyvinyl alcohol, polyethyleneimine) are also developed, and the sensing properties are investigated. The results suggest that metal ions‐based capacitive flexible sensors have great potential for low‐cost chemical sensors and provide a promising strategy for developing new sensing materials.