Surface specific adsorption of glucose to ZnO

ZnO is bio-safe and hence, may be a potential candidate for direct use as a glucose sensor. This requires an understanding of the interaction of glucose with four common surfaces, (101̄0), (112̄0), (0001) and (0001̄) of ZnO. We carry out molecular dynamics (MD) simulations enhanced by umbrella sampling of a glucose molecule in a solvent over a hydrated ZnO slab. The slab is obtained by quantum mechanical optimization. We observe that hydration layers formed above the surfaces affect the approach of glucose to the surfaces. Potential of mean force (PMF) calculations show that the (101̄0) surface shows the strongest adsorption of adsorption free energy -6.81 kJ mol^-1 towards glucose. Thus, we offer a theoretical understanding on the interactions at the nano-bio junction of glucose and ZnO surfaces. Our study suggests that the (101̄0) surface may be used to fabricate a direct glucose sensor.