Self-organized arrays of rhodamine 6G (Rh6G, Fig.1(a)) dye aggregates were prepared by a wetting/dewetting process. Using lockin detection separate aggregate particles were discriminated in the near-field fluorescence image when photo-excited by a modulated CW Nd/YAG SHG laser. Some bumps in the surface topography corresponded to intense fluorescence but other regions didn't correspond, indicating that there were non-fluorescing particles. Majority of particles seemed to be in an inactive state when we observed the region of more than 100 sub-micrometer particles, although we scanned the area only once under photo-excitation to suppress the possible photobleaching of Rh6G dye molecule.
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