An AuNPs-functionalized AlGaN/GaN high electron mobility transistor sensor for ultrasensitive detection of TNT

Herein, an ultrasensitive sensor based on a AlGaN/GaN high electron mobility transistor (HEMT) was developed for the detection of 2,4,6-trinitrotoluene (TNT). The sensing surface of the AlGaN/GaN HEMT grid was covalently bonded with a layer of gold nanoparticles which were functionalized with cysteamine for specific electrostatic interaction with TNT. The binding of TNT to cysteamine through donor–acceptor interactions could affect the surface charge on the gate area of the AlGaN/GaN HEMT, resulting in a gate voltage change and density changes of the 2-dimensional electron gas (2EDG) at the interface of AlGaN/GaN. By the merit of the high electron mobility of the AlGaN/GaN transistor and robust binding between cysteamine and TNT, the sensor demonstrated a fast response and excellent performance with quantitative ranges at ppt levels (from 0.1 ppt to 10 ppb) with good selectivity towards TNT. This HEMT sensor showed attractive properties for TNT detection in terms of speed, sensitivity and miniaturization.