Selective and Trace Level Detection of Hydrazine Using Functionalized Single-Walled Carbon Nanotube-Based Microelectronic Devices

Microelectronic devices (MEDs) that utilize functionalized single-walled carbon nanotubes (SWCNTs) for hydrazine (HZ) sensing applications were developed and investigated, demonstrating their selective and sensitive detection of trace level HZ (0.01 ppm) in the presence of high-concentration interfering gases in ambient air at room temperature. These MEDs were fabricated with excellent reproducibility by the site-specific deposition of functionalized SWCNTs using a dielectrophoretic technique. Rigorous gas exposure testing conducted on these MEDs demonstrated a fast response with high sensitivity, selectivity, reproducibility, and reliability for detecting HZ. A dynamic response range was established from a linear relationship between the sensor response and the concentration of HZ (0.01 to 0.33 ppm). Additionally, these MEDs exhibited a linear trend relationship between device resistance and sensor response, which provided tunability in selecting and fabricating devices for improving sensing response. Field-emission scanning electron microscopy images showed the morphology of SWCNTs as a bundle on MEDs. Additional analytic gas exposure tests revealed negligible responses from these MEDs for high concentrations of interfering gases, such as 300 ± 17 ppm methanol (MeOH), 85 ± 6 ppm ethanol (EtOH), 145 ± 12 ppm formaldehyde (CH 2 O), and 500 ppm ammonia (NH 3 ), compared to that of HZ (≤0.33 ppm), with HZ to interfering gas concentration ratios of 1:900, 1:250, 1:440, and 1:1500, respectively, demonstrating high sensor selectivity for HZ.