Aligned Silver Nanorod Arrays as Substrates for Surface-Enhanced Infrared Absorption Spectroscopy

Abstract

Preferentially aligned silver nanorod arrays prepared by oblique angle vapor deposition were evaluated as substrates for surface-enhanced infrared absorption (SEIRA) spectroscopy. These nanorod arrays have an irregular surface lattice and are composed of tilted, cylindrically shaped nanorods that have an average length of 868 nm +/- 95 nm and an average diameter of 99 nm +/- 29 nm. The overall enhancement factor for chemisorbed organic films of para-nitrobenzoic acid (PNBA) deposited onto the Ag nanorod arrays analyzed by external reflection SEIRA was calculated to be 31 +/- 9 compared to infrared reflection-absorption spectroscopy (IRRAS) obtained from a 500 nm Ag film substrate. This enhancement is attributed to the unique optical properties of the nanorod arrays as well as the increased surface area provided by the nanorod substrate. SEIRA reflection-absorbance intensity was observed with both p- and s-polarized incident radiation with angles of incidence ranging from 25 degrees to 80 degrees . The largest intensity was achieved with p-polarization and incident angles larger than 75 degrees . Polarization-dependent ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra of the nanorod arrays demonstrate that the red-shifted surface plasmon peaks of the elongated nanorods may be partially responsible for the observed SEIRA response. The SEIRA detection limit for the Ag nanorod arrays was estimated to be 0.08 ng/cm(2). Surface-enhanced Raman scattering (SERS) and SEIRA analysis of chemisorbed PNBA utilizing the same nanorod substrate is demonstrated.

Self‐Assembled Au Nanoparticles as Substrates for Surface‐Enhanced Vibrational Spectroscopy: Optimization and Electrochemical Stability

“…[4] Substrate development is also a highly active area in SEIRS research. The substrates developed specifically for SEIRS include vacuum-deposited metal islands, [6] nanorod arrays, [20] subwavelength holes, [21] and nanoparticles (NPs). [6,7,[22][23][24][25][26][27] Recently, a SEIRS enhancement factor of 2000 was achieved by "in situ" tailoring of the size of the metallic nanofeatures.…”

p‐Nitrobenzoic Acid Adsorption on Nanostructured Gold Surfaces Investigated by Combined Experimental and Computational Approaches

“…, which are assigned [3,39] to the symmetric COO À stretching mode. This indicates that the p-NBA molecule deprotonates and chemisorbs on the surface of the Au metal through the carboxylate group.…”

Polarization effect in tip-enhanced infrared nanospectroscopy studies of the selective Y5 receptor antagonist Lu AA33810

“…The observed differentiation is a likely consequence of the irregular substrate, forming large aggregates containing bifurcations and protrusions. This anisotropy may induce a cross-polarization effect, affecting the variations in the spectral signals [52].…”