Background-suppressed surface-enhanced molecular detection by metamaterial infrared absorber

Atsushi Ishikawa; Takuo Tanaka

doi:10.1117/12.2061505

Abstract

A background-suppressed surface-enhanced molecular detection technique is experimentally demonstrated by utilizing the resonant coupling of plasmonic modes of a metamaterial absorber and Infrared (IR) vibrational modes of molecules. The fabricated metamaterial consisted of one-dimensional (1D) array of Au micro-ribbons on a thick Au film separated by an MgF2 gap layer. The surface structures were designed to exhibit an anomalous IR absorption at ~ 3000 cm^-1, which spectrally overlapped with C-H stretching vibrational modes. 16-Mercaptohexadecanoic acid (16-MHDA) was used as a test molecule, which formed a 2-nm thick self-assembled monolayer (SAM) with their thiol head-group chemisorbed on the Au surface. In the FTIR measurements, the symmetric and asymmetric C-H stretching modes of the 16-MHDA were clearly observed as Fano-like anti-resonance peaks within a broad plasmonic absorption of the metamaterial. The lowbackground detection scheme with tailored plasmonic enhancement by the metamaterial absorber dramatically improved the sensitivity down to ~ 1.8 attomoles within the diffraction-limited IR beam spot. Our metamaterial approach thus may open up new avenues for realizing ultrasensitive IR inspection technologies.

Citation Download Citation

Atsushi Ishikawa, Atsushi Ishikawa, Takuo Tanaka, Takuo Tanaka, "Background-suppressed surface-enhanced molecular detection by metamaterial infrared absorber", Proc. SPIE 9163, Plasmonics: Metallic Nanostructures and Their Optical Properties XII, 91632Q (17 August 2014); doi: 10.1117/12.2061505; https://doi.org/10.1117/12.2061505

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