Confocal Raman microscopy: Non-destructive materials analysis with micrometer resolution

Confocal Raman Microscopy combines the three-dimensional optical resolution of confocal microscopy and the sensitivity to molecular vibrations which characterizes Raman spectroscopy. Hence, the technique is capable of providing a three-dimensional image of the chemical composition with micrometer resolution. An image is obtained by raster-scanning the sample with respect to the laser focus and measuring the integrated intensity of characteristic Raman lines. We present three applications of this method to different classes of materials. In specimens of sintered ceramics, the composition is determined and the size and shape of grains are visualized. Spider silk fibers show Raman spectra which are characteristic of the spider species; in some cases the fibers have hollow cores. Polymer fibers produced by electrospinning from mixtures of polymer solutions feature homogeneous Raman spectra, even in cases of immiscible polymers. This demonstrates that the electrospinning technique produces materials which are largery homogeneous on the micrometer length scale. The compositions of the fibers agree for most samples, but not in all cases, with the compositions of the solutions.