Multifunctional and Tunable Surfaces Based on Pyrene Functionalized Nanoparticles

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.

Electronic Communication in Confined Space Coronas of Shell‐by‐Shell Structured Al2O3 Nanoparticle Hybrids Containing Two Layers of Functional Organic Ligands

“…Subsequently, the mono‐shell‐functionalized NPs were subjected to a second, in this case non‐covalent, functionalization by treatment with the amphiphiles A 1 , A 2 , or A 3 and simultaneous dispersion of the reaction products [Al 2 O 3 ‐(PAR 2–4 X % PAR 1 (100− X )% )]A 1–3 in water or hexafluorobenzene, respectively (Scheme and ). During this procedure a polarity umpolung induced by the second ligand shell takes place according to the new supramolecular construction concept that we have reported recently . As a result, a micellar arrangement formed involving lipophilic interactions between the nonpolar parts (R 1 –R 4 ) of the first layer and the lipophilic termini of A 1–3 .…”

“…In a recent project, we manufactured Al 2 O 3 NPs with mixed shells consisting of three phosphonic acid derivatives with different polarities in combination with a pyrene‐terminated phosphonic acid . For these systems, the optoelectronic properties of the pyrene core in a series of environments were investigated by fluorescence spectroscopy investigations.…”

“…In ar ecent project, we manufactured Al 2 O 3 NPs with mixed shells consisting of three phosphonic acid derivatives with different polarities in combination with ap yrene-terminated phosphonic acid. [5] For theses ystems, the optoelectronic properties of the pyrene core in as eries of environments were investigated by fluorescence spectroscopy investigations. Furthermore, we have attached different types of amphiphiles onto the corresponding first-shell systems, which caused the embedding of pyrene chromophores in ad efined environmen-tal corona around the NPs.…”

Mixed Organic Ligand Shells: Controlling the Nanoparticle Surface Morphology toward Tuning the Optoelectronic Properties

“…A totally different concept is to build up nanoparticles (NP) directly from PBIs as starting material, or to utilize them as additives throughout NP synthesis, resulting in composite particles of, for instance, silica (SiO 2 ) and PBIs . In contrast, our strategy is based on the postsynthetic functionalization of tailored metal‐oxide NPs . This allows for the variability of the NP materials, sizes, and compositions independent of the synthetic accessibility of the PBIs during the NP formation.…”

The Impact of Aggregation on the Photophysics of Spiro‐Bridged Heterotriangulenes

“…At proximity,t he molecular building blocks favor the formation of either excimers or exciplexes with emissive features significantly different from those of the individual components. [7,21,22] Strongly distance-dependent deactivation processes such as excited-state energy, [20][21][22][23][24] charge, [25] and electron transfer [23] are facilitated between molecules in confined space.T he lack of molecular rotations leads to aggregation-induced/ -enhanced emission, which strongly favors radiative deactivations. [24,[26][27][28][29] Herein, we present asystematic study of the properties of aseries of related heteroatom-containing polycyclic aromatic hydrocarbons-namely spirofluorene-bridged triarylamine, [30] -phosphine,and phosphine oxide [31] -in the transition from molecular species to large aggregates ( Figure 1).…”