Near-Field Optical Characterization of Sub-Micrometer Particle Arrays of Organic Pigment

ABSTRACT

Sub-micrometer sized particles of organic dye, formed as precipitates on a glass surface when the organic solvent evaporated from a thin film of specimen solution at a precisely controlled evaporation rate, showed a typical one- or two-dimensional registration. We performed a near-field optical study of a single (or a few) particle(s) within these self-assembled particle arrays. Suppressing the background fluorescence that originated from the stray light in the clad region of probe fiber at the coupling point of the incident laser, we could manage to observe the near-field fluorescence from the separated particle. Further to overcome the near-field fluorescence decay in a minute or so, which was presumably due to photobleaching of surface-rich dye particles, we prepared them embedded in a transparent polymer film which is expected to protect the dye from oxygen.

Keywords:

• near-field
• organic dye
• self-assembled

Acknowledgments

This work was supported partly by the Academic Frontier Promotion Project of the Ministry of Education, Culture, Sports, Science and Technology and partly by the Science Research Promotion Fund of Japan Private School Promotion Foundation. We express thanks to Prof. Karthaus concerning the dewetting procedure.