PM-IRRAS - Langmuir Blodgett - Infra Red Reflection Absortion Spectroscopy


Product: PM-IRRAS


The KSV NIMA PM-IRRAS is the first infrared spectrometer made specifically for IR analysis of monolayers floating on an aqueous subphase or deposited on reflective substrates. It is a highly sensitive and very surface specific instrument enabling measurements in ambient conditions. The innovative goniometric configuration allows easy angle adjustment and fast setup time.


PM-IRRAS is a highly surface specific FT-IR method that is capable of detecting chemical compositions from interfacial films down to one molecule thick films.
The PM-IRRAS technique allows enhanced detection on substrates and measurements from the air-water interface.
Changes in the PM-IRRAS signal intensity and position can be used to infer molecular absorption/desorption behavior and kinetics, molecular packing, phase transitions, hydration, hydrogen bonding and different surface reactions in a thin film.
Additionally in PMIRRAS the properties of the polarized light can be used to determine the molecular orientation in a film.

The reported infrared absorption of the PM-IRRAS is in the range of 800 - 4000 cm-1 making it possible to detect the following:

- Chemical composition of thin films
- Chemical composition can be detected from thin films that are just one molecule thick.
- Adsorption / desorption and surface reactions in mono- and multilayers
- Studying interaction of biomolecules using cell membrane models can provide means to understand reactions related to drug delivery and the membrane behavior itself. These kinds of model systems are employed in several application areas, such as drug development, food technology, and biological and biochemical research.
- Phase transitions in thin films
- Monolayer phase transitions can be detected with PM-IRRAS. A typical example would be protein denaturation at the interface or deposited layer.
- Hydration / hydrogen bonding
- The PM-IRRAS peak position shifts dramatically when the hydration stage changes. This allows the observing of a films structural response due to changing external condition such as pH or temperature.
- Molecular-scale quantitative analysis of molecular orientation
- The orientation changes of molecules at the air-water interface or at reflective solids can be detected from the PM-IRRAS peak intensity. This enables, for example, observing the effect of Langmuir film packing density as well as Langmuir Blodgett coating orientation.

Working principle

The PM-IRRAS technology allows the measuring of surface specific FT-IR spectra of materials because of the differences in the reflection of p- and s-polarized light from interfaces. The polarization modulation method almost completely eliminates background signals coming from environmental factors such as water vapor and CO2 which removes the need for protective gasses as with other IR reflection instruments. By positioning the spectrometer and detector on a goniometer above the surface the experimental setup is greatly simplified and provides you with results within minutes instead of days. This open design also allows combined use of other complementary equipment like external UV light source and temperature heater.
The instrument can be positioned above a fully equipped analytical Langmuir Trough, facilitating accurate monolayer studies without restrictions.
PM-IRRAS contains a state-of-the-art compact Fourier Transform IR-spectrometer.
The spectrometer and polarization modulation unit is mounted on one arm of the goniometer with a highly sensitive MCT-detector on the other arm.
The spectrometer and PM-unit operate at different frequencies enabling separation of the two signals at the detector.
A resolution of 8 cm-1 makes it possible to observe the processes of interest in the monolayer.