Green Synthesis and Sensing Assessment of HfO2 Nanoparticles for Detecting Liquid NH3 Using Electrochemical Impedance Spectroscopy

Now-a-days, green synthesis is gaining popularity over conventional synthesis methods as it is environment-friendly, cost-effective, and less toxic. Here, we synthesized hafnium oxide (HfO
₂
) nanoparticles using orange peel extracts (OPEs, 1, 2, and 4 wt%) for the first time. HfO
₂
synthesized with 4 wt% OPE and calcined at 900 °C for 1 h (HO-4-OPE) showed well dispersed nanoparticles with maximum yield. The average crystallite size of HO-4-OPE was found to be 34 nm. A sensing framework to detect liquid NH
₃
was developed using HfO
₂
nanoparticle coated electrode and electrochemical impedance spectroscopy. An exponential relation between charge transfer resistance and NH
₃
concentration with high
R
²
(0.99) was found. A prediction model based on charge transfer resistance showed an
R
²
value of 0.95 to predict liquid NH
₃
. This initial assessment of the NH
₃
sensor shows promises for such sensors.