New Opportunities in Micro- and Macro-Attenuated Total Reflection Infrared Spectroscopic Imaging: Spatial Resolution and Sampling Versatility

TLDR

New opportunities exist to obtain chemical images using attenuated total reflection infrared (ATR‑IR) spectroscopy. The study demonstrates the feasibility of acquiring FT‑IR images with 3–4 µm resolution using a Ge ATR objective integrated with an infrared microscope. High‑index Ge ATR crystals provide a high numerical aperture that improves spatial resolution, and the use of a diamond ATR accessory enables pressure‑controlled contact across the field of view. This work is the first to report FT‑IR imaging with a diamond ATR crystal, achieving spatial resolution up to 13 µm without infrared microscope objectives.

Abstract

New opportunities exist to obtain chemical images using attenuated total reflection infrared (ATR-IR) spectroscopy. This paper shows the feasibility of obtaining FT-IR images with a spatial resolution of at least 3–4 μm using a Ge ATR objective coupled with an infrared microscope. The improved spatial resolution compared to FT-IR images obtained by the transmission method is due to the high refractive index of the ATR crystal, which gives a high numerical aperture and hence, a higher spatial resolution. FT-IR imaging with a conventional diamond ATR accessory has been investigated. This is the first time that FT-IR imaging is reported using such a versatile accessory based on a diamond ATR crystal. These results showed that a spatial resolution up to 13 μm can be achieved without the use of infrared microscope objectives. One advantage of the diamond element is that it allows pressure to be applied and hence, good contact to be obtained over the whole field of view.