Multi-modal biosensing enabled by on-chip nano-corrugated graphene

We present nano-corrugated graphene (NCGr)-based devices, which can support diverse detection strategies. A single NCGr device exhibits three different modes of biomolecular sensing: electrolyte-gated field-effect transistor (FET), electrochemical, and surface-enhanced Raman spectroscopy (SERS)-based sensing. The highest sensitivity obtained for DNA detection was ∼1 aM. The charge-transfer effect is dominant in all NCGr-integrated devices. Electrochemical complex capacitance and impedance spectroscopy results indicate the presence of coupled quantum-classical effects (from the band-gap opening) in the FET. Those effects govern its atto-molar DNA concentration detection and a nonclassical electrical double layer that reduces the ionic screening. In the electrochemical mode, the NCGr surface behaves catalytically, facilitating long-range electron transfer through hybridized DNA. NCGr enhances the optical sensing capability for SERS and activates plasmonic behavior. Computational simulations reveal that the chemical mechanism dominates in the enhancement of SERS and plasmonic devices, indicating that the charge transfer between molecules improves the optical response.