Fast transfer process of pyrene between oil-in-water miniemulsion droplets

Recently phase formation mechanisms have been estimated by using various fluorescent probes. In this report, the mixing process between internal phases of oil-in-water miniemulsions is discussed for two-dimensional color graphics data (two-dimensional fluorescence images) based on the excimer formation of pyrene as a hydrophobic fluorescent probe. Just after miniemulsion solution B (water, oil, and nonionic surfactant) was gradually added to miniemulsion A (water, oil, surfactant, and trace amount of pyrene) with gentle and careful stirring, the fluorescence spectra and the two-dimensional image of pyrene were measured. The decreasing of the excimer peak of pyrene was observed as soon as miniemulsion solution B was added. The result showed that pyrene initially located in miniemulsion droplets was smoothly diluted by the addition of miniemulsion droplets which contain only oil in the internal phase. The internal phases of miniemulsion droplets are miscible without changing the droplet diameter, and it is declared that pyrene transfers smoothly to the interface between droplets stabilized by the nonionic surfactant because the droplet diameter showed no significant difference throughout this mixing process. Received: 7 December 1999 Accepted: 11 April 2000