Ricerc@Sapienza

FTIR-microscopy is an advanced technique that couples the capability of FTIR to provide a chemical analysis of samples, with the magnification power of an IR microscope. This combination allows to add a remarkable spatial resolution (e.g. <10 or <4 microns in reflection/transmission or ATR using Ge crystals) to the infrared spectroscopic analysis of materials, thus opening the door to spatial chemical discrimination of domains in inorganic or hybrid composites as well as in bio-materials. Besides a micro-spectrophotometric IR analysis, FTIR microscopy discloses the a posteriori reconstruction of chemical images. A chemical image is the superimposition over a direct visible microscopy of a pixel-by-pixel resolved array of FTIR spectra obtained by sampling materials across XY bidimensional spatial intervals, up to a remarkable millimeter linear extent. Overall a chemical image is 4D data matrix where each pixel of the XY spatial range of a micrography corresponds to a full FTIR spectrum. FTIR microscopy platforms are commonly constituted by the integration of an FTIR spectrophotometer and an infrared (IR) microscope, built on Cassegrain optics, both driven remotely by software routines running on designed computers. Stand-alone FTIR microscopy systems run by computers are also available on the market. Nowadays FTIR microscopy systems: a. operate in transmission, reflection and attenuated total reflectance (ATR) modes; b. implement automatic XYZ stages to sample the material and focus the infrared beam; c. implement punctual, linear or bidimensional array detectors operating at room temperature or refrigerated by Peltier or liquid nitrogen; d. exploit the computational power of designed software to analyze a posteriori the 4D data matrix that constitute chemical images, through the use of advanced chemiometric routines. Thanks to the high numerical apertures (i.e. 0.4-0.8) of the commercially available IR objectives, FTIR microscopes can reach a lateral spectroscopic resolution of 5-10 microns in transmission/reflection modes, improved to 1-4 microns in ATR mode using germanium crystals.