Accessibility study of porous materials at the single-particle level as evaluated within a microfluidic chip with fluorescence microscopy

Understanding the mass-transfer phenomena taking place in solid catalysts, batteries, fuel cells, and adsorbents is essential to improve their performances. Uptake experiments of ultraviolet-active or fluorescent probes represent a direct way to provide an accessibility measure of porous particles. We propose a new method to evaluate the accessibility of functional porous materials at the single-particle level. A multiplexed microfluidic device and a fluorescence microscope are employed to assess the uptake of fluorescent molecules in porous particles over time. The device allows for performing multiple uptake experiments in parallel, enabling the comparison of different particles under the same conditions. We showcase the method by studying the diffusion and adsorption properties of a dye in different silica model particles. The approach allows for probing interparticle heterogeneity in accessibility and accessible surface area as well as the dependence of these parameters on electrostatic interactions between the particle and the probe molecules.