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Dual-band in situ molecular spectroscopy using single-sized Al-disk perfect absorbers


We propose antenna-enhanced infrared vibrational spectroscopy by adopting single-sized Al disks on Al2O3-Al films fabricated by colloidal-mask lithography. The precisely designed plasmonic resonator with dual-band perfect absorption (DPA) shows strongly-enhanced nearfield intensity and polarization independence, at both resonances, providing a powerful antenna platform for the multi-band vibrational sensing. As a proof of concept, we experimentally apply the plasmonic DPAs in bond-selective dual-band infrared sensing of an ultrathin polydimethhylsiloxine (PDMS) film, simultaneously amplifying two representative vibrational bands (asymmetric C-H stretching of CH3 at 2962 cm-1 and CH3 deformation of Si-CH3 at 1263 cm-1) by surface-enhanced infrared absorption spectroscopy (SEIRA). The plasmonic DPA was successfully adopted for the in situ monitoring of reaction kinetics, by recording the spectral changes in C-H stretching and Si-CH3 deformation modes of a 10-nm PDMS elastomer, which are selectively enhanced by the two antenna resonances, during its gelation process. Our systematic study of the SEIRA spectra has demonstrated mode splitting and a clear avoided-crossing in the dispersion curve as a function of resonance frequency of DPA, manifesting itself as a promising basis for future polaritonic devices utilizing the hybridization between the molecular vibrational states and the enhanced light field.

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Publication details

The article was received on 28 Jan 2019, accepted on 11 Apr 2019 and first published on 11 Apr 2019

Article type: Paper
DOI: 10.1039/C9NR00904C
Citation: Nanoscale, 2019, Accepted Manuscript

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    Dual-band in situ molecular spectroscopy using single-sized Al-disk perfect absorbers

    T. D. Dao, K. Chen and T. NAGAO, Nanoscale, 2019, Accepted Manuscript , DOI: 10.1039/C9NR00904C

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