Sensing of NO$_{\mathrm{2}}$ with Zirconium Hydroxide via Electrical Impedance Spectroscopy*

Nitrogen Dioxide (NO$_{\mathrm{2}})$ is a brown gas mainly produced as a byproduct of burning fossil fuels, such as automobiles and power plants. Nitrogen oxides can form acid rain and smog by reacting with air, can form toxic organic nitrates by reacting with soil, and can react with oxygen in water, destroying marine life due to a lack of breathable oxygen. Any concentration beyond 53 ppb (air quality standard) can cause irritation to the lungs and respiratory infections, and higher dosages can be fatal. As such, research in NO$_{\mathrm{2}}$ detection is incredibly important to human welfare. Zirconium hydroxide (Zr(OH)$_{\mathrm{4}})$ has been investigated as a candidate NO$_{\mathrm{2}}$ dielectric sensor using impedance spectroscopy analysis. Impedance changes of several orders of magnitude are seen down to our dosage minimum of 50 ppm\textbullet hr. Changes in impedance correlate with nitrogen and oxygen atomic ratio increases observed via X-ray photoelectron spectroscopy (XPS). The results indicate that Zr(OH)$_{\mathrm{4}}$ may be a strong candidate for use in impedance-based NO2 detection devices.