Real time detection of Hg²⁺ ions using MoS₂ functionalized AlGaN/GaN high electron mobility transistor for water quality monitoring

A sensor for highly sensitive, selective, and rapid determination of the trace amount of toxic Hg²⁺ ions is developed for the first-time using molybdenum disulfide (MoS₂) functionalized AlGaN/GaN high electron mobility transistor (HEMT). The vertically aligned, flower-like MoS₂ structures are synthesized through a simple hydrothermal route and applied on the gate region of AlGaN/GaN HEMT. The scanning electron microscopy, Raman spectroscopy, and X-ray diffraction are performed for structural characterization of MoS₂. Further, the sensing of Hg²⁺ ions is performed by electrical characterizations of MoS₂ functionalized AlGaN/GaN HEMT. The sensor showed an excellent sensitivity of 0.64 μA/ppb and detection limit of 0.01152 ppb with the rapid response time of 1.8 s. The sensor exhibits the linear range of detection from 0.1 ppb to 100 ppb and highly selective behavior towards Hg²⁺ ions. The results demonstrated that the MoS₂ possess excellent Hg²⁺ ions capture property, that could be attributed to the complexation of Hg²⁺ ions with sulfur and the electrostatic interaction between MoS₂ and Hg²⁺ ions alters the drain to source current (I_DS) of the HEMT at a constant drain to source voltage (V_DS). Therefore, the MoS₂ based AlGaN/ GaN HEMT devices have a huge potential for next-generation ion sensing applications.