Micro rings self-assembled from organic NPB and their polarized optical properties

► Micro rings of organic NPB have been prepared by evaporating chloroform solution on a silicon surface. ► The polarized fluorescence microscope images of rings show pronounced polarization related to their central angle Φ. ► The NPB molecules within a ring are highly ordered. ► Systematic investigation discloses that the water droplets condensed on silicon are essential for the ring formation.