Surface-Enhanced Infrared Absorption and Amplified Spectra on Planar Silver Halide Fiber

Abstract

We have discovered surface-enhanced infrared absorption (SEIRA) on a planar silver halide surface, the first time this effect has been observed on a non metallic substrate. The enhancement is not due to the presence of metallic silver on the surface as ruled out by X-ray photoelectron spectroscopy (XPS). In addition, the fibers show 10-fold spectral amplification due to the increased coupling of evanescent waves through an increased number of internal reflections to the samples on the surface of the thin planar element. A special cell for the fiber permits deposition of small quantities of solution followed by slow evaporation of the solvent with dry nitrogen and allows measurements to be made on much less than a monolayer of sample. The combination of easy access to the sample and high sensitivity promises many useful applications to biological, chemical, and physical problems in the mesoscopic and nanoscopic domains.

Determination of Chlorinated Hydrocarbons in Water Using Highly Sensitive Mid-Infrared Sensor Technology

“…Typically, crystalline ATR elements are used, which may be divided into three main categories according to the material properties: glass-like fibers (e.g., chalcogenides and heavy metal fluorides), polycrystalline (e.g., silver halides) or crystalline fibers (e.g., sapphire), and hollow waveguides (e.g., hollow silica or sapphire tubes)11. Among these, silver halide (AgCl x Br 1−x ) fibers are considered the most practical ATR waveguide material11, which provides access to the entire mid-infrared (MIR) spectral range of interests (3–18 μm)12, and allows flexible tuning of its geometry13. AgCl x Br 1−x fibers have been demonstrated to offer direct and accurate detection of crude oil in a deionized water matrix14, and of water in hexane at ppm levels15.…”

“…In this context, decreasing the fiber diameter or tapering a section of the fiber are both effective strategies to improves the analytical sensitivity18. Especially, the geometry of a planar sensing region with fiberoptic couplers at both ends has been reported to substantially increase the number of internal reflections, thereby leading to enhanced signals - up to one order of magnitude - compared to conventional cylindrical fibers13. In addition, to further amplify the detection signal and reduce the noise, a polymer membrane was coated onto the sensor surface.…”

Surface‐Enhanced Infrared Spectroscopy

“…Ag and Au island films are the most commonly used SEIRA substrates, but in electrochemical experiments the platinum group metals are preferred. Enhanced absorption of the vibrational spectrum in the infrared region has also been reported on planar Ag halide fibers, showing 10-fold spectral amplification that could be due to the increased coupling of evanescent waves through an increased number of internal reflections [92,93]. The investigation and explanation through adequate SEIRA models of the abnormal infrared effects (AIREs) observed in the bands of the SEIRA spectra of molecules adsorbed on these metals and on Fe [34,91] are ongoing.…”

Investigation on the Second Part of the Electromagnetic SERS Enhancement and Resulting Fabrication Strategies of Anisotropic Plasmonic Arrays

“…Thus, the strong electromagnetic field enhancement is employed for the effective enhancement of fluorescence (surface-enhanced fluorescence, SEF), [1] of the Raman cross-sections (surface-enhanced Raman spectroscopy, SERS) [2] or of IR absorption (surface-enhanced infrared absorption, SEIRA). [3] In particular, SERS has prooven to be an extremely powerful tool in bioanalytical science because it comprises high sensitivity with molecular fingerprint specificity. [2,[4][5][6][7] Recent developments in the broad field of SERS analytics are demostrated by combining SERS with microfluidic devices to develop novel lab-on-a-chip devices.…”