Mercury (II) Ion Detection Using AgNWs-MoS<sub>2</sub> Nanocomposite on GaN HEMT for IoT-Enabled Smart Water Quality Analysis
Nipun Sharma, Adarsh Nigam, Д. Н. Лобанов, Ankur Gupta, А. В. Новиков, Mahesh Kumar
Abstract
We have demonstrated a highly sensitive novel platform for real-time detection of mercury (Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ) ions after successfully making silver nanowires (AgNWs)-MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanocomposite and functionalizing it over ungated AlGaN/GaN high-electron-mobility transistor (HEMT). The AlGaN/GaN HEMT structures were grown over the sapphire substrate using molecular beam epitaxy. AgNWs-MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanocomposites were optimized for the device functionalization and 1:4 ratio was found highly sensitive for Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions. The sensor exhibits high sensitivity toward Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions of 1.604 mA/ppb and calculated its Limit of Detection (LoD) up to the range of 20 parts per trillion. The observed sensitivity is highest among previously reported AlGaN/GaN fabricated HEMT-based sensors for mercury (Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ) ions detection and is well below the standard permissible limits as set by World Health Organization (WHO) and Environmental Protection Agency (EPA). The enhancement in sensitivity is due to the enhanced surface to volume ratio of AgNW-MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanocomposite and the highly conductive nature of AgNWs incorporated in MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Moreover, we also performed sensing on real water samples of tap water and lake water. Furthermore, we showed the smart sensing capability of our developed sensor by illustrating the Internet of Things (IoT)-enabled system for next-generation heavy metal ion sensing.