IR super-resolution microspectroscopy and its application to single cells.

For many years, spatial resolution is the most critical problem in IR microspectroscopy. This is because the spatial resolution of a conventional infrared microscope is restricted by the diffraction limit, which is almost the same as the wavelength of IR light, ranging from 2.5 to 25 μm. In the recent years, we have developed two novel types of far-field IR super-resolution microscopes using 2-color laser spectroscopies, those are transient fluorescence detected IR (TFD-IR) spectroscopy and vibrational sum-frequency generation (VSFG) spectroscopy. In these ways, because both transient fluorescence and VSFG signal have a wavelength in the visible region, the image is observed at the resolution of visible light, which is about 10 times smaller than that of IR light (that is, IR super-resolution). By using these techniques, we can map the specific IR absorption band with sub-micrometer spatial resolution, visualization of the molecular structure and reaction dynamics in a non-uniform environment such as a cell becomes a possibility. In the present reviews, we introduce our novel IR super-resolution microspectroscopy and its application to single cells in detail.