Graphene assisted terahertz metamaterials for sensitive bio-sensing

•Highly sensitive monitoring of biomolecules in very low concentration using low energy photon is introduced.•Dramatically enhanced transmittance change by graphene hybridization with different types of ssDNA was detected.•Quantitative analysis of graphene conductivity under terahertz nearfield amplification was shown. We report that single-stranded deoxyribonucleic acids (ssDNAs) at very low concentrations can be detected using graphene-combined nano-slot-based terahertz (THz) resonance. A combination of the resonant structure and tuned electro-optical properties of graphene can provide unprecedentedly sensitive biomolecule sensing even using very low energy THz photons, overcoming the huge scale difference of 10,000:1 between the wavelength and the size of the ssDNAs. Ultrahigh sensitivity is obtained by the significant increase in the absorption cross-section of the graphene sheet with the targeted biomolecules, induced by strong THz field enhancement at the resonance frequency inside the slots. Clearly distinguishable THz optical signals were observed between different species of ssDNAs even at the nano-mole level and analyzed quantitatively in terms of the electro-optical properties of the suspended graphene layer modified by the attached ssDNAs without any molecular-specific labeling for the THz regime. Quantitative analysis of ssDNA molecule adsorption was carried based on the change in conductivity using a theoretical THz transmission model.