The explosion in the growth of technological applications incorporating new materials and covering a range of industries from nanotechnology to photovoltaics has created consequent growth in the need for FTIR analysis and testing for organic materials. Materials characterization measures the range of wavelengths absorbed by a material such as crystals, polymers, composites, liquids and liquid crystals.
Following are a few FTIR analysis methods used by university researchers, scientists and process engineers alike.
Attenuated Total Reflectance (ATR)
In Attenuated Total Reflectance (ATR) spectroscopy, all that is required for analysis is that the sample of interest be brought into contact with the ATR crystal. Minimal to no sample preparation is required for this technique; you can analyze a wide variety of solids and some liquids (dependent upon crystal material) using this technique.
Specular Reflectance (SR)
Specular Reflectance typically occurs from bulk samples with a glossy surface such as crystal faces, glasses, and monolithic polymers. Absorbance spectra may be obtained from specular reflection data using the Kramers-Kronig transform if the sample is homogeneous, optically thick, and if spectra are collected at a nearly normal incidence.
Reflection absorption occurs when thin films are present on a reflective substrate. Samples such as thin polymer films, residues and paints are suitable for reflection-absorption measurements, if they are present as an over layer on a reflective substrate.
Transmission spectroscopy involves passing infrared radiation completely through a sample and measuring the extent of absorption. Consequently, significant sample preparation may be required as concentration, thickness, homogeneity and particle size must all be considered. This technique is suitable for sampling gases, liquids, and solids (fibers, microtome cuts, thin films, pressed pellets, and mulls).
Photoacoustic spectroscopy (PAS) can be quite complex and difficult to perform. The photoacoustic signal is generated when the infrared radiation absorbed by a sample is converted to heat within the sample. This heat diffuses to the sample surface and into the adjacent gas atmosphere. The thermal expansion of this gas produces the photoacoustic signal.
Understanding a Material’s Structure
Different levels of sample preparation are required depending on the analysis, from minimal preparation for ATR to the most complex and difficult to perform, as with PA.
Understanding a material’s structure, how that structure determines its properties and how that material works in a technological application is essential for today’s engineers to be able to apply advanced surface and structural characterization techniques for quality assurance, contamination control and process improvement.
Learn more about FTIR analysis and how it can be used for early cancer detection in this blog.