Sensing of NO 2 with zirconium hydroxide via frequency-dependent electrical impedance spectroscopy


Zirconium hydroxide has been investigated as a candidate nitrogen dioxide dielectric sensor using impedance spectroscopy analysis. Significant changes in electronic and physical properties down to our dosage minimum of 2 ppm h have been observed. Using disc-shaped pressed pellets of $Zr(OH)_4$ in parallel plate geometry, we observe a maximum signal shift of 35% at 2 ppm h dosage, which increases six orders of magnitude as the dosage reaches 1000 ppm h. Changes in impedance correlate with nitrogen and oxygen atomic ratio increases observed via X-ray photoelectron spectroscopy (XPS) at higher ${NO}_2$ dosages. In contrast to the sharp frequency-dependent features and net impedance decreases during ${NO}_2$ exposures, $Zr(OH)_4$ exhibits a large and broad impedance increase after exposure to humid air (water vapor). The results indicate that $Zr(OH)_4$ could be used as a selective low-cost impedance-based ${NO}_2$ detector by applying frequency-dependent impedance fingerprinting.

In Dalton Transactions