Wang Weiqiang, Guo Yuanjun, Xiong Wenkai, Fu Yongqing, Elmarakbi Ahmed, Zu Xiaotao
School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China.
Faculty of Engineering & Environment, University of Northumbria, Newcastle upon Tyne, NE1 8ST, UK.
Sensors (Basel). 2022 Aug 24;22(17):6349. doi: 10.3390/s22176349.
In this study, polyacrylic acid (PAA) films were deposited onto a quartz surface acoustic wave (SAW) resonator using a spin-coating technique for ammonia sensing operated at room temperature, and the sensing mechanisms and performance were systematically studied. The oxygen-containing functional groups on the surfaces of the PAA film make it sensitive and selective to ammonia molecules, even when tested at room temperature. The ammonia molecules adsorbed by the oxygen-containing functional groups of PAA (e.g., hydroxyl and epoxy groups) increase the membrane's stiffness, which was identified as the primary mechanism leading to the positive frequency shifts. However, mass loading due to adsorption of ammonia molecules is not a major reason as it will result in a negative frequency shifts. When the PAA coated SAW sensor was exposed to ammonia with a low concentration of 500 ppb, it showed a positive frequency shift of 225 Hz, with both good repeatability and stability, as well as a good selectivity to ammonia compared with those to CHOH, H, HCl, HS, CO, NO, NO, and CHCOCH.
在本研究中，采用旋涂技术将聚丙烯酸（PAA）薄膜沉积在石英表面声波（SAW）谐振器上，用于室温下的氨传感，并对传感机制和性能进行了系统研究。即使在室温下测试，PAA薄膜表面的含氧官能团也使其对氨分子具有敏感性和选择性。被PAA的含氧官能团（如羟基和环氧基）吸附的氨分子增加了膜的刚度，这被确定为导致正频率偏移的主要机制。然而，由于氨分子吸附引起的质量负载不是主要原因，因为它会导致负频率偏移。当涂覆有PAA的SAW传感器暴露于浓度为500 ppb的低浓度氨时，它显示出225 Hz的正频率偏移，具有良好的重复性和稳定性，并且与对CHOH、H、HCl、HS、CO、NO、NO和CHCOCH的选择性相比，对氨具有良好的选择性。
