Fluorescence methods to probe mass transport and sensing in solid-state nanoporous membranes

Abstract

Single- and multi-nanoporous (1–100 nm pore size) solid-state membranes (SSNMs) receive significant attention in various fields, spanning from biosensing to water purification. Their finely tunable nanopore geometry and chemistry, combined with the large selection of materials that they can be made of, such as polymers, inorganic materials (e.g., silicon, silica, and alumina), and hydrogels, provide an excellent platform to control their mass transport and sensing capabilities for different cargoes from Å scale ions up to macromolecular biomaterials. The critical requirement to merge these nanoporous membranes’ advanced structural and chemical features with their applications is to find the most suitable analytical techniques that permit macro- and micro-scale and real-time probing of different nanopore activities. Luminescence-based detection of various physico-chemical processes in nanoporous membranes has recently received great attention: it permits rapid, non-invasive, and dynamic probing of nanoporous materials, yielding information on mass transport and sensing both (i) macroscopically, such as from an array of nanopores, and (ii) micro-nanoscopically, with ultra-high (e.g., single molecule) sensitivity and high resolution in time and space. Quantitative information arising from luminescence experiments on membrane-analyte interactions has uncovered the effects of nanoconfinement, membrane stability, and performance. This review article aims to provide the reader with a handbook of fluorescent methods–from the simplest to implement to the most advanced–helpful in studying different kinds of SSNMs for a specific application or function. To this end, we include examples from the literature published in the last ten years. At the end of our article, we also discuss limitations of the current state of fluorescence probing techniques and their future prospects.