Direct Imaging Single Molecule Diffusion in a Solid Polymer Host

The time evolution of the microscopic lateral diffusion and dynamic reorientation of individual dye molecules dispersed in a thin polymer film is probed by means of scanning near-field optical microscopy at room temperature and ambient conditions. On a sub-micrometer scale we identify regions where the diffusion is drastically non-random, while the statistical average of the trajectories of 97 molecules in a 4 μm × 4 μm section displays random-walk behavior.