Exposure to poisonous and hazardous gases such as NH₃, NO₂, and CO poses significant health risks. High-performance flexible gas sensors are essential for wearable real-time hazardous gas monitoring. Polyaniline (PANI) materials for gas sensing have advantages over conventional sensing materials like low working temperature, simple manufacturing, low cost, and high flexibility, which is particularly well suited for integrating into the developing Internet of Things to achieve real-time health monitoring or human–computer interaction. However, the PANI gas sensors still need to be improved with respect to their sensitivity, gas selectivity, or other aspects for practical applications. This article reviews three aspects including the PANI gas sensing mechanism, the nanostructure of PANI materials, and mixtures of PANI with other materials as flexible sensors. Nanostructures and nanomorphologies improved the sensor response due to the higher surface-to-volume ratio and abundant adsorption sites. Many innovative approaches to manufacturing composites allow the formation of heterojunctions at the interface to achieve better performance than chemiresistive PANI gas sensors. The synthesis protocols, structure engineering, underlying mechanisms, challenges, and future prospects of PANI sensors are also comprehensively reviewed.

Zn(CF₃COO)₂ promotes the dual reduction of anions to fluoride and sulfide, forming an amorphous hybrid solid electrolyte interface (SEI). This SEI significantly benefits the plating/stripping of Zn anode and thereby improves the battery performance.

Large-scale industrialization of flexible printed electronics will thrive on advanced functional conductive pastes with excellent properties such as high electrical conductivity and mechanical stability. Herein, we develop an effective method to simultaneously decrease the electrical resistivity and improve the mechanical stability of silver-resin-based conductors by adding a small amount of nanostructured polyaniline (PANI). PANI nanomaterials for improving the properties of conductive composites were synthesized by a facile and repeatable chemical oxidative polymerization method and characterized. Significant improvements in electrical performance were observed. For example, for the 60 wt% silver-filled flexible conductors, the addition of 0.5 wt% PANIs reduces their electrical resistivity to one-thirtieth (from 1253.1 × 10⁻⁵ Ω cm to 37.1 × 10⁻⁵ Ω cm). After adding 0.5 wt% PANIs, the bending stability (ΔR/R₀) was also greatly improved from 92% to 2.3% (about 1/40th). Meanwhile, elastic conductors showed a much better performance in resistance stability and fatigue life (5 times longer than before) during stretching cycles after the addition of PANIs. A bendable printed circuit and a printed tensile resistive sensor were fabricated using the above PANIs to enhance conductive composites, which proved their potential applications in flexible printed circuits, stretchable pressure sensors, and e-skin or other fields.