Review—Nanowire Sensors Using Electrical Resonance

Modulation of surface state population in a wide band gap semiconductor nanowire changes its electrical properties. Monitoring electrical resonance of the semiconductor nanowire offers a simple and elegant new platform for chemical sensing. The electrical resonance frequency changes sensitively when adsorbed molecules are resonantly modulated by optical excitation. Using this technique, we have detected 2,4,6-trinitrotoluene (TNT) molecules physically adsorbed on the metal oxide semiconductor BiFeO₃ (BFO) nanowire. The electrical impedance parameters of the nanowire resonator (NWR) at resonance change upon the TNT adsorption due to mass loading. Furthermore, mid-infrared (IR) spectroscopy coupled with the electrical resonance of nanowire resonator complements high selectivity by generating IR photothermal spectrum of adsorbed TNT molecules. This photothermal electrical resonance spectroscopy (PERS) technique can be used to quantitatively detect adsorbed vapors with femtogram (fg) mass resolution by high selectivity.