Two-photon near-field mapping of local molecular orientations in hexaphenyl nanofibers

Abstract

Two-photon excited near field images of hexaphenyl nanofibers are obtained using a scanning near field optical microscope in transmission configuration. From polarized measurements the orientations of the molecular basis units of the fibers are determined with a resolution of better than 400 nm. The molecular orientation angles obtained are comparable to results from two-photon scanning far-field microscopy, but the present measurements provide a better spatial resolution. From this near-field data it is concluded that the molecules can be oriented either very homogeneously or with some scatter in otherwise similar organic nanoaggregates.