Ligand‐dependent aggregation‐enhanced photoacoustic of atomically precise metal nanocluster

Abstract

Atomically precise metal nanoclusters (MNCs), as a potential type of photoacoustic (PA) contrast agent, are limited in application due to their low PA conversion efficiency (PACE). Here, with hydrophilic Au25SR18 (SR = thiolate) as model NCs, we present a result that weakly polar solvent induces aggregation, which effectively enhances PA intensity and PACE. The PA intensity and PACE are highly dependent on the degree of aggregation, while the aggregation‐enhanced PA intensity (AEPA) positively correlates to the protected ligands. Such an AEPA phenomenon indicates that aggregation actually accelerates the intramolecular motion of Au NCs, and enlarges the proportion of excited state energy dissipated through vibrational relaxation. This result conflicts with the restriction of intramolecular motion mechanism of aggregation‐induced emission. Further experiments show that the increased energy of AEPA originates from the aggregation inhibiting the intermolecular energy transfer from excited Au NCs to their surrounding medium molecules, including solvent molecule and dissolved oxygen, rather than restricting radiative relaxations. This study develops a new strategy for enhancing the PA intensity of Au NCs, and contributes to a deeper understanding of the origin of the PA signal and the excited state energy dissipation processes for MNCs.

Cysteine-Protected Antibacterial Spheroids of Atomically Precise Copper Clusters for Direct and Affordable Arsenic Detection from Drinking Water

“…Aggregation-induced emission (AIE) often observed in CuNCs enhances the emission brightness, structural stability, and sensitivity of CuNCs-assembled solids. 16,17 electrochemical 18,19 and luminescence 20,21 responses. A recent report from our group demonstrated that cobalt NCsassembled plates detect As 3+ in water electrochemically, with high sensitivity and selectivity.…”

“…Affordability in the field is an important criterion, especially in resource-limited situations. Aggregation-induced emission (AIE) often observed in CuNCs enhances the emission brightness, structural stability, and sensitivity of CuNCs-assembled solids. , Some reports on metal NCs based sensors for As detection are available, explicitly involving electrochemical , and luminescence , responses. A recent report from our group demonstrated that cobalt NCs-assembled plates detect As 3+ in water electrochemically, with high sensitivity and selectivity .…”

Fluorescent Enhancement of [AgS4] Microplates by Mechanical Force Induced Crystallinity Breaking

“…In recent decades, stimulus-responsive luminescent materials have received wide attention because of their “smart” characteristics, whereby the emitted intensity and color of light can be modified in response to the external stimuli, such as mechanical force, , light, − pH, , cations, , and solvents. − With the diversification of real-world usage scenarios, materials that exhibit fluorescence alteration induced by mechanical force (mechanofluorochromic or MFC materials) − play significant roles in various practical applications, including lighting devices, − mechano-sensors, − memory chips, − and security inks. − Up to now, a considerable number of MFC materials have been reported, including oligo-oxyethylene (OOE), , (E)-9-Octyl-3-(4-(phenylsulfonyl) styryl)-9 H -carbazole (DPS-OCZ), nanoclusters, − polydopamine, , and metal complexes. − The photoluminescent properties of these MFC materials are highly related to their corresponding surface morphologies, , inter- and intramolecular interactions, , molecular packing modes, , and molecular geometric configurations. − Upon analysis at the molecular level, similar structural features, such as lamellar layers and parallel layer structures, are observed. Consequently, when subjected to various types of mechanical force, such as grinding, crushing, stretching and so on, the molecular structures of these MFC materials easily undergo changes, leading to alterations in their emission maximum wavelength and quantum yield.…”