Ultrasensitive amine gas sensor with ppb-level detection based on vernier effect.

The trace detection of amine gases (including ammonia and volatile organic amines) at ppb levels holds significant strategic importance in environmental monitoring, industrial safety, and public health. However, developing sensing systems that combine ultra-high sensitivity with stable performance remains a fundamental challenge. This study proposes a parallel-structured fiber F-P sensor based on the vernier effect for ultra-sensitive amine detection, achieving highly sensitive and reliable measurement even at extremely low concentrations. The 24-fold vernier structure enhanced sensitivity to pyrrolamine by 9.3-fold, reaching a detection limit of 0.159 ppb, while the 24-fold structure further improved sensitivity to 301.68 pm/ppb with a detection limit of 0.066 ppb. Similar substantial sensitivity enhancements were observed for putrescine, with the 24-fold structure achieving a sensitivity of 225.33 pm/ppb and a detection limit of 0.089 ppb. Response time from air to amine gas was 53 seconds, and recovery time from amine gas back to air was 45 seconds. The vernier structure effectively amplifies signals while maintaining excellent sensor selectivity, exhibiting response coefficients below 0.50 pm/ppb for interfering gases such as methanol, ethanol, and acetone, thereby resolving the inherent trade-off between ultra-sensitivity and reliability.