Near-field photothermal Fourier transform infrared spectroscopy using synchrotron radiation

Synchrotron radiation has been used to perform near-field photothermal Fourier transform infrared (IR) spectroscopy, in a brief exploratory investigation. An optical microscope is used to focus the IR beam onto a thermal probe, in contact with the surface of a sample, mounted in a specially designed atomic force microscope head. The stable and highly collimated synchrotron radiation beam gives a very small effective source size with low thermal noise. We used a miniature batch-manufactured micromachined type of thermal probe as the temperature sensor. The results of a three-day trial showed that the spectral contrast observed is much improved in comparison with that seen in spectra obtained using a thermal source. Measurements on a polypropylene/polycaprolactone interface confirmed that line-map measurements should be practicable. One potential advantage of the technique is that it uses the same sensor, the thermal probe, as a number of complementary analytical methods.