An Ab-initio Perspective on Simultaneous Detection of Uric Acid and Ascorbic Acid Using Graphene Oxide*

Simultaneous detection of uric acid and ascorbic acid from different biofluids is an open research problem as both of them have similar oxidation potential. Incorporating graphene oxide as the sensing substrate will significantly enhance the system's selectivity towards uric acid and ascorbic acid detection. The percentage of sp² carbon atoms inside graphene oxide structure is the most important parameter to delineate the degree of oxidation or reduction in graphene oxide. Thus, an extensive first principle analysis has been carried out to select a suitable percentage of sp² carbon atoms in graphene oxide structure which can simultaneously detect uric acid and ascorbic acid. The structural stability and integrity of the selected adsorbed geometries are validated through phonon dispersion calculations. The obtained electronic band gap, along with projected density of states analysis, confirms that after uric acid and ascorbic acid adsorption, the conductivity of the system alters significantly, and thus a change in band gap is visible. Furthermore, the charge redistribution upon adsorption of two different analytes over graphene oxide substrate is validated by Löwdin population analysis. The charge difference density plot also confirms the electrostatic nature of substrate and analyte interaction.