Toward Graphene-Enhanced Spectroelectrochemical Sensors

Spectroelectrochemical sensors (SPECSs) sensitive to the least amount of sample are crucial for widespread applications, including early-stage detection of fatal diseases and other biomedical applications. However, despite the major disadvantage of biomolecule instability on noble metal nanoparticle-assisted surface-enhanced SPECSs, designing a suitable alternative remains a great challenge. The authors report a proof-of-concept graphene-enhanced spectroelectrochemical sensors (GE-SPECSs) employing graphene-enhanced Raman spectroscopy (GERS). Pristine (p-) and hydrogenated (h-) single-layer graphene (SLG) are utilized to study the oxidized and reduced states of a probe molecule, methylene blue (MB). The hole-doped h-SLG possesses efficient GERS signals compared with p-SLG, resulting in a limit of detection (LOD) < 10(-7) m. By taking advantage of the tunable work function of graphene, the authors demonstrate that the GERS signal from the probe molecule can be varied and different oxidation states of the molecule can be studied by applying suitable external potentials. The LOD obtained in an aqueous system (approximate to 10(-7) m) is comparable with standard surface-enhanced SPECSs. The authors' design thus creates a novel pathway for developing highly efficient, biofriendly, and cost-effective SPECSs.