The convergence of nano-optics with an aqueous environment is promising for future chemical or biological applications. While the rapid development in nanofabrication has led to the realization of sub-10 nm nanogaps of various structures, coupling water into high aspect ratio metallic nanogaps with a well-defined area is not yet demonstrated. Here, arrays of 10 nm wide metallic trenches are reported filled with dielectric, air, liquid water, and various molecules in optical hotspots. Due to the high height-to-width aspect ratio of 20:1 and strong gap plasmon coupling in the 10 nm width, the trenches show distinct spectral changes at terahertz frequencies under changing gap materials, from which the full etching and water filling of the 10 nm gap can be unambiguously confirmed. A 75% transmitted amplitude decrease is observed through 200 nm deep trenches upon water filling, which converts to an effective 1100-fold increase in the water absorption coefficient. The gap-filling scheme can be applied to distinguish different liquids with 400 attoliters of volume or to detect rhodamine 6G molecules inside the gap with surface-enhanced Raman scattering. Accordingly, the scheme can also be applied to a general class of polar organic molecules suitable for various biological or chemical applications.
|Original language||English (US)|
|Journal||Advanced Optical Materials|
|State||Published - Nov 5 2018|
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science, Information and Communication Technology: NRF-2015R1A3A2031768) (Ministry of Education: BK21 Plus Program-21A20131111123). The work was also supported (for K.S.L., H.-K.C., and Z.H.K.) by the BioNano Health-Guard Research Center funded by the Ministry of Science, Information and Communication Technology and Future Planning (MSIP) of Korea as Global Frontier Project (H-GUARD_2013 M3A6B2078947), and by the NRF Grant No. 2016R1A2B2011160 and NRF-2016M3A7B4909776, Nano R&D program. S.W.L. was supported by the “Human Resources Program in Energy Technology” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) with a grant of financial resources from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20164030201380).
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- sub-10 nm
- terahertz absorption
- terahertz nanoantennas