Atomically Precise Noble Metal Cluster-Assembled Superstructures in Water: Luminescence Enhancement and Sensing

Abstract

We present an example of host–guest complexes of atomically precise noble metal nanoparticles with cucurbit[7]­uril (CB) in water, specifically concentrating on Ag29(LA)12 (where LA is α-lipoic acid), a well-known red luminescent silver cluster. Such host–guest interactions resulted in enhanced luminescence of about 1.25 times for the modified system, compared to the parent cluster. We extended our study to cyclodextrins (CDs), where about 1.5 times enhanced luminescence was estimated compared to the parent cluster. The formation of supramolecular complexes was confirmed using high-resolution electrospray ionization mass spectrometry (HRESI MS) and nuclear magnetic resonance spectroscopy. Molecular docking and density functional theory calculations supported our experimental results and showed that while CB formed inclusion complexes by encapsulation of one of the LA ligands of the cluster, CD formed supramolecular adducts by interaction with the cavity built by the ligands on the cluster surface. The complexation was favored by geometrical compatibility. Consequently, these superstructures are labeled as Ag29LA12∩CB n and Ag29LA12@CD n (n = 1–3), where ∩ and @ indicate the inclusion complex and supramolecular adduct, respectively. Solution-phase Ag29LA12@CD n complexes were employed to detect dopamine (10 nM). Luminescent Ag29LA12@CD n and Ag29LA12∩CB n complexes in water could be potential candidates for organic pollutant sensing and biomedical applications.

An atomically precise silver nanocluster for artificial light-harvesting system through supramolecular functionalization

“…[35][36][37][38] Progressing research activities suggest that imposing bulkiness on the surface protecting groups can restrict the intramolecular motion of the NC in solution that can directly decrease the nonradiative relaxation pathway and enhance the emission properties. [39][40][41][42][43][44][45][46][47][48] Therefore, it will be very interesting to encapsulate the ligand-protected Ag NC with a bulky host to build the hostguest adduct at the recognition site of the NC to improve the emission properties by introducing surface rigidity through bulkiness to counteract the thermally activated non-radiative relaxation which will be benecial for the articial LHS fabrication.…”

Highly Fluorescent Gold Cluster Assembly

“…Various approaches have been tried to improve the PL efficiency of metal NCs by tailoring their size, structure, composition, and surface chemistry. − The exchange of capping ligand with a high electron donation capability has been found to boost the ligand to metal or ligand to metal–metal charge transfer. − Furthermore, a rigidified environment around the surface of NCs is shown to reduce the nonradiative relaxations of NCs with minimal structural changes. The protection by protein or polymer, − ion-pairing, , and aggregation/assembly of NCs − can also minimize the undesired energy dissipation of NCs.…”

Driving Forces and Routes for Aggregation-Induced Emission-Based Highly Luminescent Metal Nanocluster Assembly

“…; and x represents the unit number), are arguably some of the best-known examples in this context. − They have a unique core-in-cage-like structure with a typical diameter of less than 3 nm. The past decade has witnessed several significant research advances in this field, such as the development of synthesis methodology for truly monodispersed MNCs, breakthroughs in their crystal structures, and rational understanding in their structure–property relationships, to name just a few. − Remarkably, introducing the AIE phenomenon for the design and development of highly luminescent MNCs (termed AIE-type MNCs, henceforth) has been extremely significant. − The development of AIE-type MNCs was sought after for overcoming the poor PL efficiency of conventional MNCs. , The strategy has successfully made several highly luminescent MNCs; however, limited understanding of their structures and their relationship with the PL properties leaves much to be desired.…”