Dual-band in situ molecular spectroscopy using single-sized Al-disk perfect absorbers. Issue 19 (3rd May 2019)

• Record Type: Journal Article
• Authors: Dao, Thang Duy; Chen, Kai; Nagao, Tadaaki
• Is Part Of: Nanoscale. Volume 11:Issue 19(2019)
• Page Start: 9508
• Page End: 9517
• Publication Date: 2019-05-03
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c9nr00904c
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : Plasmonic perfect absorbers with a single-sized resonator for simultaneous sensitive dual-band vibrational sensing and real-time observation of molecular reaction kinetics were proposed. Abstract : We propose antenna-enhanced infrared vibrational spectroscopy by adopting single-sized Al disks on Al2 O3 -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 polydimethylsiloxane (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.