Impact of Annealing on Soil Moisture Sensing Properties of Graphene Oxide

Abstract

Soil moisture is one of the important parameters for precise irrigation models. In this work, we have fabricated the graphene oxide (GO) based soil moisture sensor and considered the effect of the annealing on the soil moisture sensing properties. For this purpose, first, we have prepared the sensor where we have taken three derivatives of the GO viz. GO prepared at room temperature (25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> C), GO annealed at 50 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C, and 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C. Further, these three forms of GO are drop casted on the IDEs fabricated on the silicon substrates and explored the sensor’s transfer function characteristics. Lab measurements results indicate that the fabricated sensors offer a response of about $\approx$384 %, $\approx$306 %, and$\approx$224 %, when the gravimetric water content (GWC) is varied from 1.5 % GWC to 23 % GWC for the GO prepared at 25 0C, 50 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C and 90 0C, respectively. Likewise, we also observed that GO prepared at 25 0C is highly selective to the GWC when compared with the GO prepared at 50 0C and 90 oC. Based on these experimental investigations we analyzed that the sensor response drops as the annealing temperature is increased. This is attributed to the diminishing oxygen functional groups when the temperature increases.