Chemical imaging with variable angles of incidence using a diamond attenuated total reflection accessory

Area of Science:

• Spectroscopy
• Chemical Imaging
• Materials Science

Background:

• Fourier Transform Infrared (FT-IR) imaging is a powerful technique for chemical analysis.
• Traditional FT-IR imaging with attenuated total reflection (ATR) has limitations in probing subsurface layers.
• Developing methods to access deeper sample information without altering the imaging area is crucial.

Purpose of the Study:

• To introduce a novel FT-IR imaging method using a diamond ATR accessory with a variable angle of incidence.
• To demonstrate the capability of obtaining chemical images from subsurface layers of different thicknesses.
• To enable three-dimensional (3D) chemical information acquisition.

Main Methods:

• Utilized a diamond ATR imaging accessory with a modified optical design.
• Introduced a movable aperture to control the angle of incidence.
• Varied the angle of incidence and spectral bands (wavenumbers) to probe different depths.
• Analyzed two sample types for calibration and capability demonstration.

Main Results:

• Successfully obtained chemical images from subsurface layers by adjusting the angle of incidence.
• Demonstrated the ability to acquire information from different depths within the same sample area.
• Achieved high spatial resolution (12 µm features) without a microscope.
• Maintained consistent imaging and sampling areas during angle manipulation.

Conclusions:

• The novel FT-IR imaging approach with variable angle of incidence offers enhanced subsurface analysis capabilities.
• This method provides a new pathway for 3D chemical imaging with high spatial resolution.
• The technique is valuable for detailed characterization of sample heterogeneity at different depths.