Infrared spectroscopy is used to obtain information about the different bonds between the atoms in a material. Interpretation of the position and width of the different IR-peaks can lead to important structural information.
Two types of FT-IR set-ups are generally used:
(i) TRANSMISSION FT-IR: The infrared spectrum of a sample is collected by passing a beam of infrared light through the sample. Examination of the transmitted light reveals how much energy was absorbed at each wavelength. The obtained spectrum has accurate peak positions and a high resolution.
(ii) DRIFT: In this set-up, the diffuse reflected light is collected instead of the transmitted radiation. This technique allows conversion to kubelka-munk absorbance, resulting in semi-quantitative analysis.
In-situ IR techniques are used to study the formation and/or structural changes of material in real time, often to understand the reaction mechanism better.
FT-IR spectra are measured on a Nicolet 6700 FT-IR (fig. 1) or on a Nicolet Nexus FT-IR spectrometer (fig. 2). They both use a mid-IR source (400-4000 cm-1), a KBr-beamsplitter, a He/Ne laser and a Michelson interferometer, and are purged with a dry air flow. Both spectrometers have a MCT-B and a DTGS detector. It is also possible to measure a near-IR spectrum by using the CaF2 beamsplitter (of the FT-Raman bench) in the Nicolet Nexus FT-IR spectrometer.
1. Drift cell
2. Transmission cell
3. In-situ drift cell
4. Home build in-situ transmission cell