Application of an ATR Method in Raman Spectroscopy

Abstract

The attenuated total reflection (ATR) method in a prism/gap/metal configuration was used in Raman spectroscopy of molecules adsorbed on silver to improve the detection limit. The thickness of the air gap was controlled between ΛL/2 and 2ΛL (ΛL: wavelength of the incident light) with a biaxial suspension. All the scattered light within the SPP cone was collected with a Weierstrass prism and a 1:1 objective. The enhancement factor of the Raman scattering intensity for the use of in- and out-coupling of the SPP was found to be 134 and 70 for carbon and copper-phthalocyanine (CuPc), respectively. The scattered light inside the SPP cone is additionally enhanced by the interference in the air gap. This interference is also useful to enhance the Raman signals of the adsorbates. Nearly the same enhancement factor was observed for the different symmetry species of vibrations in CuPc, because CuPc is randomly oriented with respect to the silver surface normal.

Electronic effects in SERS by liquid water

“…In order to surmount these difficulties, the attenuated total reflection (ATR)-Raman method, which yields electromagnetic enhancement on smooth metal surfaces, was set up. 30 In this way the detection of Raman signals of adsorbates on both smooth and single-crystalline metal surfaces becomes possible.…”

“…Raman spectra were excited with 647.1 nm radiation (100 mW). A Weierstrass prism (WP) 30 made of ZnSe (radius r D 5 mm, refractive index n D 2.6 at 647.1 nm), which is longer by r/n than a hemispherical prism, is mounted in the bottom of the electrochemical cell (see Fig. 7).…”

“…In our present ATR-Raman study on a singlecrystalline Cu electrode, an EM enhancement of ca 70-fold is provided by the ATR-Raman configuration. 30,31 We also tried to change the distance between the Cu single-crystalline electrode and the ZnSe prism to adjust the SPP excitation on or off. When the distance is not optimized for SPP excitation, no SERS signal of water is observed in the whole potential region investigated.…”

Improved Surface Plasmonic Wave Propagation of a Prism Coupler through Optimal Grating Structure Design

“…Total internal reflection occurs in the prism-air interface and plasmonic wave excitation is generated in the air-metal interface. However, the air gap thickness between the prism and metal film is hard to be controlled in detail [3]. Kretschmann-Raether configuration [2,4], another prism coupling system, is three-layered system consisting of the thin metal film sandwiched between the prism and dielectric material commonly employed in the spectrophotometer devices.…”

Attenuated Total Internal Reflection (ATR) Raman Microspectroscopy

“…As such it would be desirable to increase the collection efficiency of the measured Raman signal if possible. Futamata et al has described the use of a solid immersion lens (SIL) in an ATR configuration for the macro Raman study of thin films enhanced by surface plasmon polaritons [1]. In an effort to further improve upon the volumetric resolution and the collection efficiency for conventional Raman microspectroscopy we have investigated attenuated total internal reflection (ATR) using a ZnSe immersion lens which is the focus of this brief.…”