Novel Graphene Paper Sensors: Detection and Sensitivity Parameters

To improve human health, we need to engineer sensitive, reliable, and rapid point-of-care devices that are clinically available for a quicker diagnosis.  We chose to work with carbon, a common element used in sensing devices.  Graphene has a planar sp² carbon lattice with similar properties as carbon nanotubes, but with easier production.  In particular, we work with graphene paper, a graphene-cellulose blend, to create a unique sensor for protein detection.  To the best of our knowledge, graphene paper has not previously been used as the detection element in a sensor.  We have discovered that the surface electrical resistivity (SR) of the paper increases as the concentration of bovine serum albumin (BSA) increases.  After exploring graphene papers with different graphene/cellulose ratios, we determined that 50 wt% graphene is the most sensitive to pH changes.  The 50 wt% graphene paper has a decrease in the equilibrium dissociation constant of BSA binding as pH is increased.  We have explored the effects of conductivity on these devices, and the conductivity must be less than 10 mS/cm in order to calculate a reliable SR.  We aim to determine the range of conditions under which graphene paper can serve as a detection element in a sensor.