Colloidal quantum dot-based surface acoustic wave sensors for NO2-sensing behavior

• Published in: Sensors and actuators. B, Chemical Chemical, 2019-05, Vol.287, p.241-249
• Main Authors: Li, Min, Kan, Hao, Chen, Shutian, Feng, Xiaoying, Li, Hui, Li, Chong, Fu, Chen, Quan, Aojie, Sun, Huibin, Luo, Jingting, Liu, Xueli, Wang, Wen, Liu, Huan, Wei, Qiuping, Fu, Yongqing
• Format: Article
• Language: English
• Subjects: Colloidal quantum dots; Colloiding; Delay lines; Frequency shift; Gas sensor; Lead; Lead sulfide; Lead sulfides; Molecular structure; Nitrogen dioxide; Nitrogen oxide; Quantum dots; Quartz; Recovery; Selectivity; Sensors; Spin coating; Surface acoustic wave; Surface acoustic wave devices; Surface acoustic waves
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2019.02.042

•Small-size and high-crystallinity PbS CQDs were synthesized via a simple cation exchange method.•The PbS CQDs were successfully integrated into the SAW delay lines by spin-coating at room temperature.•The CQD-coated SAW sensor exhibited high sensor response to low-concentration of NO2 gas at room temperature. Surface acoustic wave (SAW) sensors have great advantages in real-time and in-situ gas detection due to their wireless and passive characteristics. Using nanostructured sensing materials to enhance the SAW sensor’s responses has become a research focus in recent years. In this paper, solution-processed PbS colloidal quantum dots (CQDs) were integrated into quartz SAW devices for enhancing the performance of NO2 detection operated at room temperature. The PbS CQDs were directly spin-coated onto ST-cut quartz SAW delay lines, followed by a ligand exchange treatment using Pb(NO3)2. Upon exposure to 10 ppm of NO2 gas, the sensor coated with untreated PbS CQDs showed response and recovery times of 487 s and 302 s, and a negative frequency shift of −2.2 kHz, mainly due to the mass loading effect caused by the absorption of NO2 gas on the surface of the dense CQD film. Whereas the Pb(NO3)2-treated sensor showed fast response and recovery times of 45 s and 58 s, and a large positive frequency shift of 9.8 kHz, which might be attributed to the trapping of NO2 molecules in the porous structure and thus making the film stiffer. Moreover, the Pb(NO3)2-treated sensor showed good stability and selectivity at room temperature.