Self-Organized Nanorod Arrays for Large-Area Surface-Enhanced Infrared Absorption

Abstract

Capabilities of highly sensitive surface-enhanced infrared absorption (SEIRA) spectroscopy are demonstrated by exploiting large-area templates (cm 2 ) based on selforganized (SO) nanorod antennas. We engineered highly dense arrays of gold nanorod antennas featuring polarization-sensitive localized plasmon resonances, tunable over a broadband near-and mid-infrared (IR) spectrum, in overlap with the so-called "functional group" window. We demonstrate polarization-sensitive SEIRA activity, homogeneous over macroscopic areas and stable in time, by exploiting prototype self-assembled monolayers of IR-active octadecanthiol (ODT) molecules. The strong coupling between the plasmonic excitation and molecular stretching modes gives rise to characteristic Fano resonances in SEIRA. The SO engineering of the active hotspots in the arrays allows us to achieve signal amplitude improved up to 5.7%. This figure is competitive to the response of lithographic nanoantennas and is stable when the optical excitation spot varies from the micro-to macroscale, thus enabling highly sensitive SEIRA spectroscopy with costeffective nanosensor devices.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

“…The detection limit of a SEIRA sensor based on a Au NR array has been shown to be as low as two proteins (Figure a) . In addition, polarization-sensitive SEIRA can be realized using Au-NR-based plasmonic structures based on their intrinsic anisotropy …”

Understanding adsorption geometry of organometallic molecules on graphite

“…The pristine graphene substrate exfoliated from HOPG showed no indication of CH 3 -related peaks. As the reaction time progressed, the bands at 2922 and 2870 cm −1 , assigned to the asymmetric and symmetric methyl (CH 3 ) stretching modes of the methyl groups in Cp * , respectively 30 , 31 , increased sequentially. These results show that the Cp * fragments originating from Cp * Ru + reacted to the graphene surface as the reaction time progressed.…”

Nanoplasmonic Nanorods/Nanowires from Single to Assembly: Syntheses, Physical Mechanisms and Applications

“…The highly repeatable and stable of the Fano lineshape in SEIRA highlights the great potential of these nanorod arrays in the fields of amplitude and deviation sensitive infrared spectroscopy and biosensors. [64] Compared with SERS, which is one of the surface enhanced optical effects, SEIRA has some differences in wavelength and enhancement mechanism. There are two mechanisms of SERS: physical enhancement and chemical enhancement, but the physical mechanism occupies the main position.…”

“…(b), (d) Vibrational signal from the ODT monolayer respectively extracted from the two spectra of (a), (b). [64] Reprinted with permission from Ref. [64].…”