Kabir K M Mohibul, Sabri Ylias M, Esmaielzadeh Kandjani Ahmad, Matthews Glenn I, Field Matthew, Jones Lathe A, Nafady Ayman, Ippolito Samuel J, Bhargava Suresh K
∥Department of Chemistry, Faculty of Science, Sohag University, Sohag, Egypt.
⊥Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia.
Langmuir. 2015 Aug 4;31(30):8519-29. doi: 10.1021/acs.langmuir.5b01858. Epub 2015 Jul 23.
Microelectromechanical sensors based on surface acoustic wave (SAW) and quartz crystal microbalance (QCM) transducers possess substantial potential as online elemental mercury (Hg(0)) vapor detectors in industrial stack effluents. In this study, a comparison of SAW- and QCM-based sensors is performed for the detection of low concentrations of Hg(0) vapor (ranging from 24 to 365 ppbv). Experimental measurements and finite element method (FEM) simulations allow the comparison of these sensors with regard to their sensitivity, sorption and desorption characteristics, and response time following Hg(0) vapor exposure at various operating temperatures ranging from 35 to 75 °C. Both of the sensors were fabricated on quartz substrates (ST and AT cut quartz for SAW and QCM devices, respectively) and employed thin gold (Au) layers as the electrodes. The SAW-based sensor exhibited up to ∼111 and ∼39 times higher response magnitudes than did the QCM-based sensor at 35 and 55 °C, respectively, when exposed to Hg(0) vapor concentrations ranging from 24 to 365 ppbv. The Hg(0) sorption and desorption calibration curves of both sensors were found to fit well with the Langmuir extension isotherm at different operating temperatures. Furthermore, the Hg(0) sorption and desorption rate demonstrated by the SAW-based sensor was found to decrease as the operating temperature increased, while the opposite trend was observed for the QCM-based sensor. However, the SAW-based sensor reached the maximum Hg(0) sorption rate faster than the QCM-based sensor regardless of operating temperature, whereas both sensors showed similar response times (t90) at various temperatures. Additionally, the sorption rate data was utilized in this study in order to obtain a faster response time from the sensor upon exposure to Hg(0) vapor. Furthermore, comparative analysis of the developed sensors' selectivity showed that the SAW-based sensor had a higher overall selectivity (90%) than did the QCM counterpart (84%) while Hg(0) vapor was measured in the presence of ammonia (NH3), humidity, and a number of volatile organic compounds at the chosen operating temperature of 55 °C.
基于表面声波（SAW）和石英晶体微天平（QCM）传感器的微机电传感器，在工业烟囱废气中作为在线元素汞（Hg(0)）蒸汽探测器具有巨大潜力。在本研究中，对基于SAW和QCM的传感器进行了比较，以检测低浓度的Hg(0)蒸汽（范围为24至365 ppbv）。实验测量和有限元方法（FEM）模拟使得能够在35至75°C的各种操作温度下，就这些传感器的灵敏度、吸附和解吸特性以及Hg(0)蒸汽暴露后的响应时间进行比较。两种传感器均在石英基板上制造（SAW和QCM器件分别采用ST和AT切割石英），并使用薄金（Au）层作为电极。当暴露于浓度范围为24至365 ppbv的Hg(0)蒸汽时，基于SAW的传感器在35°C和55°C下的响应幅度分别比基于QCM的传感器高出约111倍和39倍。发现两种传感器的Hg(0)吸附和解吸校准曲线在不同操作温度下均与朗缪尔扩展等温线拟合良好。此外，发现基于SAW的传感器所表现出Hg(0)吸附和解吸速率随操作温度升高而降低，而基于QCM的传感器则呈现相反趋势。然而，无论操作温度如何，基于SAW的传感器比基于QCM的传感器更快达到最大Hg(0)吸附速率，而两种传感器在不同温度下显示出相似的响应时间（t90）。此外，本研究利用吸附速率数据以便传感器在暴露于Hg(0)蒸汽时获得更快的响应时间。此外，对所开发传感器选择性的比较分析表明，在55°C的选定操作温度下，当在氨（NH3）、湿度和多种挥发性有机化合物存在的情况下测量Hg(0)蒸汽时，基于SAW的传感器具有比基于QCM的传感器更高的总体选择性（90%）（84%）。
