Evaluation of Intraparticle Diffusion Behavior in Porous Particle by Confocal Fluorescence Microspectroscopy

Abstract

Confocal fluorescence microspectroscopy allows us to obtain the fluorescence depth profile of a sample. In this paper, we discuss distribution behavior of fluorescence dye into single porous silica particle using confocal fluorescence spectroscopy. A single silica particle was transferred to the solution including target dye using a micromanipulation/injection system. When the time-dependence of the fluorescence intensity profile of target along the particle central axis is measured, intraparticle diffusion behavior can be evaluated. The fluorescence intensity profile can be simulated using a diffusion coefficient and spherical diffusion model. Moreover, the rate-determining process of intraparticle diffusion on the distribution and release processes can be qualitatively determined as intraparticle and external diffusions from the fluorescence depth profile. The contribution of pore and surface diffusions to the intraparticle diffusion can be estimated using the pore and surface diffusion model. In this account, we introduce the intraparticle diffusion mechanisms of fluorescence dyes, protein (myoglobin), and nucleotides (DNA), mainly focusing on the results of our work.