凯发

Owing to its high carrier mobility, large surface-to-volume ratio, and chemical stability, graphene has drawn considerable attention as the building block for next generation label-free electrical biochemical sensors. However, under physiological conditions, graphene sensors typically cannot detect a biological stimuli occurring at a distance larger than a nanometer from its surface (the so called 'Debye screening length') due to the presence of movable ions. At high frequencies the ions in the electrolyte start to lag behind the alternating current electric field due to the viscosity of the solution. As a result, the electrolyte behaves as a pure dielectric at radiofrequency/microwave frequencies. And one can now probe the biomolecules deeply into the electrolyte solutions beyond the Debye screening length. Indeed, with the prospects of on-chip integration of sensor arrays and low-cost mass production, the expected results on graphene radiofrequency devices represent a novel approach for a new generation of portable, point-of-care, label-free biochemical sensors.