An ion-in-conjugation polymer enables the detection of NO2 with parts-per-trillion sensitivity and ultrahigh selectivity

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 8; no. 3; pp. 1052 - 1058
• Main Authors: Chuang, Yu, Hong-Zhen, Lin, Zhou, Jin, Xue-Feng, Cheng, Jing-Hui, He, Li, Hua, Qing-Feng, Xu, Na-Jun, Li, Dong-Yun, Chen, Jian-Mei, Lu
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2020
• Subjects: Chemical bonds; Conjugation; detection limit; Environmental monitoring; Gases; human health; hydrogen bonding; Infrared spectroscopy; Nitrogen dioxide; Organic chemistry; Polymers; Selectivity; Sensitivity; Spectrum analysis
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/c9ta11513g

The detection of nitric dioxide (NO2) at the parts-per-trillion (ppt) level is critical for both environmental monitoring and human health. However, none of the chemiresistors reported to date can detect NO2 at the parts-per-trillion (ppt) level due to the low sensitivity of the sensory materials. In this work, an ion-in-conjugation polymer para-polyphenylsquaraine (p-PPS) was designed and fabricated into an NO2 chemiresistor. The sensor had the highest sensitivity of 1450 ppm−1 (at 100 ppb) and the lowest detection limit of 40 ppt among all reported chemiresistors. In addition, p-PPS showed ultrahigh selectivity, where other interfering gases had less than 1/1887th of the signal of NO2 under the same concentration (10 ppm). Calculations, in situ infrared spectroscopy and sum frequency generation spectroscopy (SFG) revealed that the ion-in-conjugation-inspired H-bonding between p-PPS and NO2 led to such high sensitivity. Our results highlight the potential of the concept of ion-in-conjugation in the design of highly sensitive gas sensory materials.