Highly sensitive, selective and rapid in-vitro electrochemical sensing of dopamine achieved on oxygen deficient nickel oxide/partially reduced graphene oxide (NiOx/p-rGO) nanocomposite platform

In this work, efforts have been given to address the challenge of rapid detection of the neurotransmitter dopamine in ppb or nanomolar (nM) order without compromising with sensitivity and selectivity. Here, oxygen deficient nickel oxide (NiO_x) has been chosen to make composite with partially reduced graphene oxide i.e., p-rGO, which being another multifunctional material bears its own significance for this purpose. An in-situ electrochemical technique was adopted to deposit thin films of NiO_x/p-rGO nanocomposite on fluorine doped tin oxide coated glass substrates. The deposited films were thoroughly characterized for structural, phase purity, compositional and morphological aspects. Detailed electrochemical properties and sensing attributes of the fabricated electrodes were established through cyclic voltammetry, differential pulse voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The sensing platform delivered a markedly high value of sensitivity of 24.76 µAµM^-1cm⁻² towards in-vitro sensing of dopamine taken in ppb order; associated with a very low limit of detection of 22.0 nM, i.e., 4.17 ppb and a very fast response time of 30 ms. The developed sensing platform was found to be robust enough from the point of view of both structural properties and sensing performance. Detailed studies on the effect of temperature, pH and scan rate were also carried out. Analysis of real sample was also executed taking adult human male urine that yielded a promisingly good recovery factor (98 – 100 %) and fairly low relative standard deviation (0.15 – 0.53), making the sensing platform suitable for real life applications.