Dithiocarbonate-Protected Au25 Nanorods of a Chiral D5 Configuration and NIR-II Phosphorescence

Unprecedented stacking-dependent piezoluminescence enhancement in atomically precise superatomic gold nanoclusters

Deciphering the structure-property relationship between cluster stacking and high-efficiency luminescence of metal nanoclusters is crucial for designing and synthesizing high-performance light-emitting materials and devices. Here, we successfully synthesized two polymorphic gold nanoclusters (Au8-C and Au8-P) and investigated their stacking-dependent piezoluminescence based on hydrostatic pressure. Under compression, Au8-C exhibits notable piezoluminescence enhancement. However, Au8-P presents monotonic piezoluminescence quenching. High-pressure structural characterizations confirm the existence of stacking-dependent anisotropic compression in Au8-C and Au8-P. Under high pressure, the columnar-stacked Au8-C shrinks faster along the a axis, increasing the aspect ratio (AR) of the fusiform Au8 core. However, the layered Au8-P is compressed faster along the c axis, reducing the AR and leading to a flatter Au8 core. High-pressure femtosecond transient absorption, time-resolved photoluminescence, and Raman spectra collaboratively confirm that differentiated anisotropic compression notably suppresses nonradiative loss caused by low-frequency vibrations of the Au8 core, which is responsible for the piezoluminescence enhancement in Au8-C.

Anti-Heavy-Atom Effect Observed in Near-Infrared Emissive Bimetallic Nanoclusters Au28Cu12X4Cl4 (X = Cl, Br, and I)

Metal nanoclusters with high photoluminescence quantum yield (PLQY) in the near-infrared region (NIR) have attracted considerable interest, and the elucidation of their structure-property relationships and luminescence mechanisms facilitates rational synthesis and practical applications. The direct reduction of alkynyl-gold precursors and copper salts leads to the formation of a series of face-centered cubic bimetallic nanoclusters Au28Cu12X4Cl4 (X = Cl, Br, and I), which exhibits strong NIR emission (∼850 nm) with PLQY being 14, 10, and 8% in the solution at room temperature, respectively. In contrast to the well-known heavy-atom effect, when the four chlorides in the Au24Cu4 core are replaced with bromides or iodides, the luminescence of Au28Cu12X4Cl4 is not enhanced but diminished instead. Excited-state dynamics studies reveal that heavier halogen atoms have a negligible effect on the intersystem crossing rate. Instead, their larger atomic sizes lead to an expansion of the cluster cores, which increases nonradiative transition rates and reduces PLQY. This is the first observation of an anti-heavy-atom effect in luminescent nanoclusters.

All-Alkynyl Protected Rod-Shaped Au9(AgCu)126 Nanocluster with Remarkable Photothermal Conversion

High-nuclearity intermetallic nanoclusters are important for investigating the evolution of alloy materials from atoms to plasmonic alloy nanoparticles. However, the synthesis of large-size alloy nanoclusters (∼2 nm) is still challenging. In this work, an all-alkynyl protected trimetallic nanocluster of unprecedented size, Au9Ag126- xCux(PhCC)68(BF4)5 (x = 0-20) (1) (PhCC = phenylacetylene), has been synthesized and its total structure determined by single crystal X-ray diffraction (SCXRD). The metal core of 1 is rod-like in structure, with a length of 1.92 nm and a width of 1.45 nm. Cluster 1 contains a concentric metal kernel in the manner of shell-by-shell arrangements of Au3Ag34@Au6Ag64@(AgCu)28 protected by 68 PhCC ligands with 15 distinct alkynyl-metal binding configurations. Theoretic calculation reveals that 1 features a HOMO-LUMO energy gap of 0.29 eV. This suggests that 1 is situated at the boundary of the transition from a molecular to a metallic state. Remarkably, compared to other reported Au/Ag/Cu/Pd based nanoclusters, 1 exhibits significantly enhanced photothermal conversion capability. A substantial temperature rise of ∼51.5 °C within 5 min (λex = 660 nm, 0.5 W cm-2) and a record high photothermal conversion efficiency of 84.7% at 12 µM in N,N-dimethylformamide (DMF) were observed. Time-resolved transient absorption (TA) spectroscopy reveals that the electron-phonon coupling (τe-ph) of excited 1 occurs on the femtosecond timescale, resulting in an ultrafast electronic relaxation process and excellent photothermal performance. Cluster 1, when employed as a photothermal material, shows promise in biothermal therapy, photothermal catalysis, and photothermal imaging.

Synthesis of [Ni23Se12X3(PEt3)10] (X = Br, I) via Post-synthetic Modification

Treatment of [Ni23Se12Cl3(PEt3)10] (1-Cl) with excess Me3SiX (X = Br, I) results in formation of [Ni23Se12X3(PEt3)10] (X = Br, 1-Br; X = I, 1-I) in good yields. 1-Br and 1-I are exceptionally rare examples of atomically precise nickel nanoclusters (APNCs). Both 1-Br and 1-I were characterized by X-ray crystallography, NMR spectroscopy, and ESI-mass spectrometry. Both clusters feature a compact [Ni13]7+ kernel capped by a [Ni10(μ-Se)9X3]- shell. Cluster 1-Br could also be isolated cleanly using a bottom-up synthetic approach, via reaction of [Ni(1,5-cod)2] and PEt3 with SePEt3 and [NiBr2(PEt3)2]. Under these conditions, it could be isolated in 43% yield. In contrast, reaction of [Ni(1,5-cod)2] and PEt3 with SePEt3 and [NiI2(PEt3)2] results in formation of [Ni3(μ3-Se)2I2(PEt3)4] (2-I) as the only isolable product. These results highlight the challenges inherent in the bottom-up synthesis of Ni nanoclusters, and demonstrate the value of postsynthetic modification in the synthesis of 3d metal APNCs.

A Portable Electrochemical Biosensor Based on an Amino-Modified Ionic Metal-Organic Framework for the One-Site Detection of Multiple Organophosphorus Pesticides

Constructing stable, portable sensors and revealing their mechanisms is challenging. Ion metal-organic frameworks (IMOFs) are poised to serve as highly effective electrochemical sensors for detecting organophosphorus pesticides (OPs), leveraging their unique charge properties. In this work, an amino-modified IMOF was constructed and combined with near-field communication (NFC) technology to develop a portable, touchless, and battery-free electrochemical biosensor NH2-IMOF@CS@AChE. -NH2 in NH2-IMOF gives the framework a higher electropositivity compared to IMOF, enhancing the electrostatic attraction with acetylcholinesterase (AChE), which is beneficial for immobilizing AChE. Furthermore, the uncoordinated O atoms and the (CH3)2NH2+ groups in NH2-IMOF help to form stronger bonds with AChE through hydrogen bonds. The results showed a wide linear response range of 1 × 10-15 to 1 × 10-9 M and a low detection limit of 1.24 × 10-13 M for glyphosate (Gly) in the practical detection of OPs. Additionally, electrochemical biosensor arrays were constructed to effectively identify and distinguish multiple OPs on the basis of their unique differential pulse voltammetry (DPV) electrochemical signals. This work provides a simple and effective solution for on-site OP analysis and can be widely applied in food safety and water quality monitoring.

Size disproportionation among nanocluster transformations

Controllable transformation is a prerequisite to the in-depth understanding of structure evolution mechanisms and structure-property correlations at the atomic level. Most transformation cases direct the directional evolution of nanocluster sizes, i.e., size-maintained, size-increased, or size-reduced transformation, while size disproportionation was rarely reported. Here, we report the Au-doping-induced size disproportionation of nanocluster transformation. Slight Au-doping on the bimetallic (AgCu)43 nanocluster produced its trimetallic derivative, (AuAgCu)43, following a size-maintained transformation. By comparison, the (AgCu)43 nanocluster underwent a size-disproportionation transformation under heavy Au alloying, leading to the formation of size-reduced (AuAgCu)33 and size-increased (AuAgCu)56 nanoclusters simultaneously. Such a size disproportionation among the nanocluster transformations was verified by the thin-layer chromatography analysis. This work presented a novel nanocluster transformation case with a size disproportionation characteristic, expected to provide guidance for the understanding of cluster size evolutions.