Abstract
NH 3 is a hazardous atmospheric pollutant in excessive concentrations and an important biomedical marker, requiring sensitive, low-power, and real-time monitoring for environmental safety. Chemiresistive gas sensors are attractive for NH 3 detection due to their simple design, high signal efficiency, and compatibility with flexible electronics. Most of these sensors based on pristine metal oxide semiconductors, which operates at high temperatures, leading to high power consumption and limiting wearable applications, while conducting polymer based sensors suffer from long term stability and humidity. Compared to these materials, carbon nanomaterials have emerged as promising room-temperature sensing materials due to their high surface area, excellent conductivity, and enviromental friendliness·NH 3 sensing in various type of carbon materials is governed by physisorption and chemisorption, enabling fast and reversible sensing performance. However, pristine carbon often shows limited selectivity toward certain gas molecules and poor cyclablity. In this review, we comprehensively analyze recent advances in binary and ternary carbon-based composites for chemiresistive NH 3 sensors, focusing on synergistic effects such as heterojunction formation and surface functionalization. Furthermore, investigate various morphologies and structures, alongside key challenges and future directions, and examine their relationships to gas-sensing performance, demonstrating their promise for robust, flexible, and wearable NH 3 sensor applications.