Recent Developments in Fourier Transform Infrared (FTIR) Microspectroscopic Methods for Biomedical Analyses: From Single-Point Detection to Two-Dimensional Imaging
Since both biological structures and systems of interest within the materials research community are chemically heterogeneous at the microscopic level, the spatial distribution of the underlying chemical species defining the molecular complex often determines the function and properties of the macroscopic assembly. As a corollary, changes in the microscopic molecular heterogeneity may alter significantly the chemical and physical attributes of a substance. While optical microscopy techniques may be employed to survey molecular heterogeneity, they provide little information on, for example, the chemical composition, molecular structure, or local packing characteristics. In contrast, microspectroscopic techniques,
such as those involving vibrational spectroscopy, afford potentially powerful complementary approaches for addressing these questions. Thus, a combination of microscopy methodologies and infrared spectroscopy, in particular, retains the spectroscopic advantages of experimental versatility and the availability of extensive databases, while introducing the spatial selectivity inherent in microscopic techniques. In particular, the mid-infrared spectral region (4000 to 400 cm
), which has been the focus of microspectroscopic examinations for many decades, has proved to be an invaluable source of compositional and structural information for a wide variety of materials. In this brief survey, we first review the instrumentation required for conducting mid-infrared microspectroscopy and then describe several examples illustrating recent developments in this area.