Multifunctional and Tunable Surfaces Based on Pyrene Functionalized Nanoparticles

Abstract

Abstract The tuning of the optical properties of pyrene, immobilized on alumina nanoparticle surfaces, is demonstrated. To this end, phosphonic acid functionalized pyrene derivatives are shown to self‐assemble into stoichiometrically mixed monolayers featuring hydrophilic, hydrophobic, or fluorophilic phosphonic acid ligands and to form defined core–shell hybrids depending on the molecular mixing ratio and the nature of the ligand monomer, excimer, or mutual emission of both evolved. The spectroscopic observations are explained by the respective mobility of the dye molecules with respect to their fixed, specific anchor points and the resulting probability to form excimers and are supported by molecular dynamic simulations, X‐ray reflectivity measurements, and temperature‐dependent steady‐state fluorescence assays. In terms of an additional tuning of the emission color change and/or the on‐off switching of the fluorescence, the formation of core–shell–shell system is carried out by applying amphiphiles. The general concept is fully transferable to demobilized films of nanoparticles, thereby enabling a switchable solid‐state surface.