Abstract
This review provides a critical overview of current developments on nanoelectronic biochemical sensors based on graphene. Composed of a single layer of conjugated carbon atoms, graphene has outstanding high carrier mobility and low intrinsic electrical noise, but a chemically inert surface. Surface functionalization is therefore crucial to unravel graphene sensitivity and selectivity for the detection of targeted analytes. To achieve optimal performance of graphene transistors for biochemical sensing, the tuning of the graphene surface properties via surface functionalization and passivation is highlighted, as well as the tuning of its electrical operation by utilizing multifrequency ambipolar configuration and a high frequency measurement scheme to overcome the Debye screening to achieve low noise and highly sensitive detection. Potential applications and prospectives of ultrasensitive graphene electronic biochemical sensors ranging from environmental monitoring and food safety, healthcare and medical diagnosis, to life science research, are presented as well.
Highlights
Graphene-based electronic devices with superior performances have been achieved, the reproducibility and reliability of graphene-based field-effect transistor (GFET) biosensors were not always studied or achieved, which represent a big challenge for the development of generation GFET sensor devices
chemical vapor deposition (CVD) graphene grown on Cu with meter-length crystals has been achieved in laboratory,[109] which opens the window toward industrial production of high-quality graphene with mobilities over 104 cm2 V−1 s−1
On-surface bottom-up approach is promising for achieving atomically defined graphene nanoribbons (GNRs), offering additional opportunity to control the microstructure of graphene.[240]
Summary
Graphene field-effect biosensors come from the big family of ion-sensitive FETs (ISFETs), which detect the conductance changes of the semiconducting channel upon binding of charged ions or biomolecules due to the field effect. To ensure a stable operation of the electronic sensor devices in electrolyte solutions, insulating layers such as SiO2 and Al2O3 have been routinely adopted to isolate and protect the chemically reactive semiconducting channel from directly contacting the ions and biomolecules. This relatively thick layer of insulating material reduces the interfacial capacitive coupling between the sensor channel and the electrolyte solution, limiting the device sensitivity. Practical sensor designs should take the possible changes of the interfacial capacitance upon biomolecule adsorption into account.[60]
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