Mercury Sorption and Desorption on Gold: A Comparative Analysis of Surface Acoustic Wave and Quartz Crystal Microbalance-Based Sensors

详细信息    查看全文

• 作者：K. M. Mohibul Kabir ; Ylias M. Sabri ; Ahmad Esmaielzadeh Kandjani ; Glenn I. Matthews ; Matthew Field ; Lathe A. Jones ; Ayman Nafady ; Samuel J. Ippolito ; Suresh K Bhargava
• 刊名：Langmuir
• 出版年：2015
• 出版时间：August 4, 2015
• 年：2015
• 卷：31
• 期：30
• 页码：8519-8529
• 全文大小：842K
• ISSN：1520-5827

文摘

Microelectromechanical sensors based on surface acoustic wave (SAW) and quartz crystal microbalance (QCM) transducers possess substantial potential as online elemental mercury (Hg⁰) 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 Hg⁰ vapor (ranging from 24 to 365 ppb_v). 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 Hg⁰ vapor exposure at various operating temperatures ranging from 35 to 75 掳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 鈭?11 and 鈭?9 times higher response magnitudes than did the QCM-based sensor at 35 and 55 掳C, respectively, when exposed to Hg⁰ vapor concentrations ranging from 24 to 365 ppb_v. The Hg⁰ sorption and desorption calibration curves of both sensors were found to fit well with the Langmuir extension isotherm at different operating temperatures. Furthermore, the Hg⁰ 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 Hg⁰ 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 Hg⁰ vapor. Furthermore, comparative analysis of the developed sensors鈥?selectivity showed that the SAW-based sensor had a higher overall selectivity (90%) than did the QCM counterpart (84%) while Hg⁰ vapor was measured in the presence of ammonia (NH₃), humidity, and a number of volatile organic compounds at the chosen operating temperature of 55 掳C.