Abstract
We report on improvement of sensitivity for molecular detection utilizing terahertz time domain spectroscopy. Based on confining and enhancing electromagnetic field with metallic nanoslot antennas, we additionally employ monolayer graphene sheet whose edge and hydrophobic surface nature lead to increase detecting performance. Terahertz transmittance in monolayer graphene/metallic nanoslot structure exhibits more unambiguous change after lactose molecules are attached, compared to that in metallic nanoslot structure without monolayer graphene. We attribute the prominent change to that more lactose molecules are guided inside/near the metal gap region due to edge and hydrophobic surface nature of monolayer graphene. This monolayer graphene/metallic nanoslot structure can be expanded in other organic or bio-molecular detection.
Highlights
We report on improvement of sensitivity for molecular detection utilizing terahertz time domain spectroscopy
Monolayer graphene (MLG) can promote molecular adsorption at its defective site which is relevant for functionalization with various materials from gases to bio-molecules[7,8,9,10,11,12,13,14,15,16,17]
We attribute the result to the fact that the total number of lactose molecules increases near the gap due to edge structure and hydrophobic surface nature of monolayer graphene (MLG)
Summary
Terahertz time-domain spectroscopy is a useful tool for detecting bio-molecules which have resonant absorption in the terahertz frequency regime. It can be estimated that total number of molecules inside the gap for MLG-covered nanoslot antennas is around two times larger than that for bare nanoslot antennas We attribute this improved sensitivity to more contribution of molecules caused by MLG which has properties (defective site at edge and hydrophobicity), while higher sensitivity of molecular detection had been achieved by stronger field enhancement and desirable metal structures in other previous works[1,2,3]. Larger contact angle represents smaller area and higher solution droplet, increasing the possibility of molecular adsorption near and inside the slot antenna We note that our sensing approach can be improved by additional chemical treatment such as fluorine which has larger contact angle[29]
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