Interfacial Clustering-Triggered Fluorescence–Phosphorescence Dual Solvoluminescence of Metal Nanoclusters

Abstract

The fluorescence-phosphorescence dual solvoluminescence (SL) of water-soluble metal nanoclusters (NCs) at room temperature was successfully achieved by a simple solvent-stimulated strategy. The strong interaction between carboxylate ligands and the metal core at the nanoscale interface not only induces rigid conformations of carbonyl groups but also affords a perfect carbonyl cluster that acts as an exact chromophore of metal NCs for aggregation-induced emission (AIE) mechanics. The clustering of carbonyl groups bearing on the polymer backbone chain is promoted by newly discovered n → π* noncovalent interactions. The efficient delocalization of electrons in overlapped C═O double bonds between neighboring carbonyl groups triggered by strong n → π* interactions in the polymer cluster accounts for its unique SL properties, especially the abnormal phosphorescence. This was further confirmed by controlled experiments for the presence of intersystem crossing (ISC) transitions. The results provide novel insights for understanding the complex SL process and open up a new way to study the inherent mechanism of SL by broadening the application of metal NCs.

P band intermediate state (PBIS) tailors photoluminescence emission at confined nanoscale interface

“…Among all of these, metal NCs with a precise number of metal atoms and ligands possess an exciting interface, which has the potential to elucidate fundamental electron exchange and energy transfer pathways driving nanoscale phenomena [5][6][7] . Even though the nanocluster-centered free-electron model based on quantum confinement mechanism have been studied for over a decade, the elucidation on the origin of the optoelectronic properties of metal NCs is diverse and contradictory, at every point inviting inquiry and debate 1,[8][9][10][11][12][13][14][15][16] . Previously, we provided key evidence for the first time that the self-assembling of surface protecting ligands on the metal core played a paramount role to tune the optoelectronic properties of noble metal NCs 12,13,17 .…”

Amphiphilicity Regulation of AgI Nanoclusters: Self‐Assembly and Its Application as a Luminescent Probe

“…The lifetime increases to 310 ns (54 ns (16.33 %), 360 ns (83.67 %)) at f =30 % and 370 ns (170 ns (16.31 %), 410 ns (83.69 %)) at f =60 %, which is about 100 times longer than that of a single molecule of Ag 6 @C 16 mim‐NC. The nanosecond‐scale lifetime illustrated that the luminescence of Ag 6 @C 16 mim‐NCs in DMSO involves only singlet excited states, whereas the microsecond‐scale long‐lived luminescence of Ag 6 @C 16 mim‐NCs observed in DMSO/water solvent mixtures was ascribed to ligand‐to‐metal charge transfer (LMCT) . It can be speculated that, with the formation of compact self‐assemblies, the intramolecular vibration of the capping ligands was restricted, which block the energy loss in nonradiative decay and greatly improve the radiative relaxation of excited states.…”

“…The nanosecond-scale lifetime illustrated that the luminescence of Ag 6 @C 16 mim-NCs in DMSO involves only singlete xcited states,w hereas the microsecond-scale long-lived luminescence of Ag 6 @C 16 mim-NCso bserved in DMSO/water solvent mixtures was ascribed to ligand-to-metal charget ransfer (LMCT). [39,40] It can be speculated that, with the formationo fc ompacts elf-assemblies, the intramolecular vibration of the capping ligands was restricted, which block the energy loss in nonradiatived ecay and greatly improvet he radiative relaxation of excited states. Thus, the luminescence of Ag 6 @C 16 mim-NCs enhanced sharply in DMSO/ water solventmixtures by an AIE strategy.…”

Origin of the Photoluminescence of Metal Nanoclusters: From Metal-Centered Emission to Ligand-Centered Emission

“…However, it is not the case. Very recently, we unexpectedly observed a strong solvent-induced enhancement effect of carboxyl-protected water-soluble AgNCs, indicating the invalidity of the well-accepted metal centered QCE model [88]. The emission QY of AgNCs could be largely improved from approximately 1% to 40% by a simple solvent-stimulated strategy ( Figure 13).…”

“…Schematic illustration of the solvent-induced clustering process of Ag NCs (top) depending on the unique molecular structure of the polymer used as a template for the synthesis of Ag NCs (bottom-right) and the energy-level structure of Ag NCs in water solution and DMSO solution (bottom-left). Reprinted with permission from Ref [88]…”