2, KTH Royal Institute of Technology, Kista, , Sweden
We introduce experimental and theoretical investigation of a new structure using graphene based schottky diode (graphene-metal-semiconductor junction) in non-enzymatic glucose sensing applications by oxidation and reduction of glucose molecules on the surface of Pt-thin film and enhancement of current in presence of graphene layers on the surface of Pt. It was noticed by increasing Pt-thickness, the higher graphene growth, the higher the output current values (15µA for 50nmPt at 10mM glucose). In addition, sensitivity of the structure was tested by varying glucose concentrations between 2-15mM. Furthermore, Electrochemical measurements demonstrated glucose molecules adsorption and desorption on the surface of the structure when prepared in phosphate buffer saline (pH=7.4). Besides, selectivity test has shown the selectivity of the structure toward glucose molecules in presence of other solutions i.e. NaCl, KCl, sucrose, Na2SO4, urea and H2O2. Theoretical modeling by using tight binding and first principles confirmed glucose molecules adsorption and diffusion through the surface of graphene and charge density due to glucose oxidation and formation of gluco-lactone molecules as noticed from density functional theory, the binding energy is -0.27 eV. Moreover, charge distribution is noticed at the interface between glucose and Pt-Graphene layers. The physisorption interaction between graphene and Pt results in shifting fermi-level position and p-doping graphene so, oxidation of glucose molecules on the surface of the structure will change the local electric field distribution and the variation in schottky barrier height (SBH) in Pt/n-Si will result in detectable current changes due to molecules adsorption. This structure can be useful in future sensing applications i.e. gas sensors and electro-chemical sensors.