Design and fabrication of a nanocrystalline graphite thin-film sensor for in situ ionic concentration monitoring

The sensing potential of a nanocrystalline graphite (NCG) film deposited using plasma enhanced chemical vapour deposition (PECVD) for detecting concentration changes of ammonium nitrate and ammonium sulphate in aqueous solutions was demonstrated using a two-terminal resistive sensing setup. The sensor shows high linearity in the reduction of resistance with increasing salt concentrations when tested with 0.01 to 2.0M aqueous solutions. This work shows promising outlook for the application of NCG based sensors for in situ agricultural soil monitoring with sufficiently fast response for continuous logging (<2 seconds).