Fluorescence Microspectroscopic Analysis of Surfactant Transfer in the Single Octadecylsilyl Silica Gel Microparticle/Water System

Mass Transfer in Mesoporous Microparticles Studied by Confocal Fluorescence Recovery after Photobleaching

“…As reported previously, in release-rate measurements for C102 from single ODS silica gel microparticles into water, the release rate of C102 was limited by the external diffusion, given by 3Dw/(rp 2 R), as the rate constant, where Dw is the diffusion coefficient of C102 in bulk water phase and R is the distribution coefficient of C102 between the ODS silica gel and water phases, and the intraparticle diffusion was very rapid. 23,24 That conclusion is consistent with the results of the present study.…”

“…21,22 In the ODS silica-gel system, on the other hand, the rate-determining step of the mass transfer processes of coumarin 102 (C102) was the diffusion between the microparticle surface and the bulk solution phase (external diffusion). 23,24 However, the intraparticle diffusion of C102 in ODS silica gel was rapid, and could not be fully analyzed using the given technique. The application range of each method is limited; thus, further kinetic analysis methods will be necessary for a greater understanding of intraparticle mass transfer.…”

Analysis of Distribution and Intraparticle Diffusion of a Fluorescent Dye in Mesoporous Silica Gel by Confocal Fluorescence Microspectroscopy

“…Recently, we have developed the confocal fluorescence microspectroscopy method combined with the single microparticle injection technique. 16,17 Using the technique, time dependence of coumarin 102 distribution as a depth profile of the fluorescence intensity in a single ODS-silica gel microparticle in an aqueous solution could be directly observed at the time greater than ~1 min. In the system, the concentration gradient of coumarin 102 between the particle surface and the particle interior was not observed, so the intraparticle diffusion of the dye was expected to be very fast.…”