Tailoring the interaction between a gold nanocluster and a fluorescent dye by cluster size: creating a toolbox of range-adjustable pH sensors

Abstract

We present a novel strategy for tailoring the fluorescent azadioxatriangulenium (KU) dye-based pH sensor to the target pH range by regulating the pKa value of the gold nanoclusters. Based on...

Atomistic View of the Energy Transfer in a Fluorophore-Functionalized Gold Nanocluster

“…Atomistic simulation methods have provided valuable guidance in understanding different physicochemical properties of ligand-protected metal nanoclusters, such as their geometry, stability, surface charge, and solubility, and how they behave under specific environmental conditions. ,− Here, we explored the potential interaction modes between the KU dyes and Au 25 ( p -MBA) 18 nanocluster by modeling a dynamic formation of the Au 25 ( p -MBA) 18 +KU complex in aqueous solution using GROMACS software . We considered three different starting configurations for complex formation with a 1:2 ([mol Au25 ]/[mol KU ]) molar ratio (Figure S11) to represent the random positions of the dye molecules when approaching the Au 25 ( p -MBA) 18 nanocluster.…”

“…Au 25 ( p -MBA) 18 is known to possess a negative surface charge in basic conditions due to deprotonation of the carboxylic group of the p -MBA ligands, promoting the binding of the positively charged KU dyes to form a noncovalently bound complex (Au 25 ( p -MBA) 18 +KU). , (Figure a) The complexation can facilitate Förster-type energy transfer from the KU dye to the gold nanocluster, and as a result, the emission of the KU dye decreases rapidly upon the addition of Au 25 ( p -MBA) 18 in aqueous solution. Steady-state fluorescence spectra of a KU dye solution (pH 10; see Supporting Information for experimental details) upon addition of Au 25 ( p -MBA) 18 are presented in Figure b.…”

“…8−10 Furthermore, the size and the surface charge of the nanoclusters modulate the fluorescence in pH sensing applications by adjusting the pH response range of the fluorophore. 11,12 Despite these merits, a detailed understanding of the dynamics of the nanocluster−fluorophore energy transfer pair in solution is lacking. For example, it is known that different counterions, concentrations, and temperatures can change the behavior of small ligand-protected metal nanoclusters and fluorophores, such as the orientation and rigidity of the ligands or the degree of aggregation.…”

“…In several recent studies, thiolate ligand-protected metal nanoclusters were selected as the fluorophore-functionalized nanomaterials due to their low toxicity, facile surface functionalization, high photostability, and well-defined structure. − Moreover, their broad absorption range has made metal nanoclusters ideal materials for FRET-based systems. In these systems, the fluorescence efficiency of the metal nanocluster is enhanced by the energy transfer from the fluorophore, which enables utilization of the nanocluster in many optical applications, such as bioimaging and light-emitting diodes (LED). − Furthermore, the size and the surface charge of the nanoclusters modulate the fluorescence in pH sensing applications by adjusting the pH response range of the fluorophore. , …”

The Conformational Dynamics of the Ligands Determines the Electronic Circular Dichroism of the Chiral Au38(SC2H4Ph)24 Cluster

“…In recent years, the dynamic effects of RS-AuNCs have been investigated in several works of Bürgi and collaborators − combining vibrational spectroscopy and theoretical calculations (i.e., DFT and molecular dynamics (MD) simulations). Furthermore, in a recent work of Pyo et al the interplay between ligand orientations and p K a of Au 25 and Au 102 NCs has been assessed by combining MD simulations and ED analysis.…”