Real Time Sensing of Soil Potassium Levels Using Zinc Oxide-Multiwall Carbon Nanotube-Based Sensors

There is a significant interest in the detection and monitoring of nutrient levels in agriculture farms. In this article, we report the fabrication of Zinc oxide (ZnO) modified multi-walled Carbon nanotube (F-MWCNT) sensor specifically developed for soil nutrient sensing. A thin layer of Valinomycin membrane was grown on the top of the F-MWCNT/ZnO nanocomposite active layer. The resulting composite structure Al/F-MWCNT/ZnO/Valinomycin was found to have a proportional impedance change with soil Potassium (K
⁺
) levels. The performance of the sensor was investigated in the 1- 5 kHz range. The impedance magnitude was found to linearly decrease from 2.5± 0.23 to
$0.63\pm 0.12~\text{M}\Omega $
range for K
⁺
concentrations from 5 to 25 mM displaying a sensitivity of
$\sim 3~\text{M}\Omega $
/mM with a correlation coefficient (R
²
) of 0.95744.