Single-Molecule Stoichiometry of Supramolecular Complexes

Abstract

The use of single-molecule microscopy is introduced as a method to quantify the photophysical properties of supramolecular complexes rapidly at ultra low concentrations (<1 nM), previously inaccessible. Using a model supramolecular system based on the host–guest complexation of cucurbit­[n]­uril (CB­[n]) macrocycles together with a fluorescent guest (Ant910Me), we probe fluorescent CB­[n] host–guest complexes in the single molecule regime. We show quantification and differentiation of host–guest photophysics and stoichiometries, both in aqueous media and noninvasively in hydrogel, by thresholding detected photons. This methodology has wide reaching implications in aiding the design of next-generation materials with programmed and controlled properties.