Real time detection of Hg²⁺ ions using MoS₂ functionalized AlGaN/GaN HEMT for water quality monitoring

The Molybdenum disulfide (MoS₂), a two-dimensional transition metal dichalcogenide (TMDC) material received considerable attention due to their semiconducting electronic properties and ultrahigh surface to volume ratio. Moreover, the detection of mercury ions in water can also be realized using the strong binding affinity of MoS₂ towards Hg²⁺ ions. In this work, we report, the application of MoS₂ as a functionalized material on the gate region of AlGaN/GaN high electron mobility transistors (HEMT). The MoS₂ was prepared by simple hydrothermal approach. The structural and morphological analysis was carried using scanning electron microscopy, X-ray diffraction, and Raman characterization. The AlGaN/GaN HEMT are normally on device due to availability of two-dimensional electron gas (2DEG) at the heterointerface AlGaN/GaN. This 2DEG can be modulated by change in electronic properties of MoS₂ during exposure of Hg²⁺ ions. By exposing MoS₂ functionalized AlGaN/GaN HEMT in Hg²⁺ ion solution, the gate potential varied due to formation of Hg-S complexion and electrostatic interaction which in turn change the drain to source current (IDS). Here the concentration of Hg²⁺ ions was varied from 1 ppt to 10 ppm and corresponding change in IDS was observed. The sensor shown good selectivity towards Hg²⁺ ions and limit of detection was observed 11.52 ppt which is well below than world health organization guidelines. Thus, the trace level detection of toxic Hg²⁺ ions can be realized using MoS₂ functionalized AlGaN/GaN HEMT. (author)