Fluorescence Resonance Energy Transfer in a Supramolecular Assembly of Luminescent Silver Nanoclusters and a Cucurbit[8]uril-Based Host-Guest System.

The understanding of interactions between organic chromophores and biocompatible luminescent noble metal nanoclusters (NCs) leading to an energy transfer process that has applications in light-harvesting materials is still in its nascent stage. This work describes a photoluminescent supramolecular assembly, made in two stages, employing an energy transfer process between silver (Ag) NCs as the donor and a host-guest system as the acceptor that can find potential applications in diverse fields. Initially, we explored the host-guest chemistry between a cationic guest ethidium bromide and cucurbit[8]uril host to modulate the fluorescence property of the acceptor. The host-guest interactions were characterized by using UV-vis absorption, steady-state and time-resolved spectroscopy, molecular docking, proton H nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and isothermal calorimetry studies. Next, we prepared a series of blue-emitting AgNCs using different templates such as proteins and peptides. We have found that these AgNCs can be employed as a donor in the energy transfer process upon mixing with the above acceptor for emission color tuning. Our in-depth studies also revealed that surface ligands could play a key role in modulating the energy transfer efficiency. Overall, by employing a noncovalent strategy, we have tried to develop Förster resonance energy transfer FRET) pairs using blue-emitting NCs and a host-guest complex that could find potential applications in constructing advanced sustainable light-harvesting, white light-emitting, and anti-counterfeiting materials.