Patterned deposition of luminescent organic nanoparticles fabricated by visible laser processing

Abstract

Dye polymer solution was dispersed homogeneously in water as µm‐size tiny droplets, leading to turbid appearance due to light scattering. Upon irradiation of Nd/YAG SHG ns‐laser, the solvent rapidly evaporated from each droplet, and the insoluble polymer was exposed to and cooled by the surrounding water, precipitating as nanoparticles (NPs), still highly luminescent under fluorescent microscope observation. The NP size deduced from the dynamic light scattering was 100–250 nm for MEHPPV NPs, and 300–500 nm for polyfluorene NPs, after centrifugal removal of the aggregates. The NP suspension was then cast on the surface of TiO2 substrate with nanogrooves transcribed from a recorded DVD‐R disk. Both MEHPPV and polyfluorene NPs were successfully observed as separate luminescent spots deposited on the nanogrooves of the TiO2 substrate. The number density of deposited NPs would be increased if a condensed NP suspension was cast on the substrate, leading to the realization of an intentional geometric pattern for example “digital signage” device application, that displays a high‐resolution static image, at low cost without the need for expensive TFT circuitry.