Phosphinothiolates as Ligands for Polyhydrido Copper Nanoclusters

The reaction of [CuI(HSC₆H₄PPh₂)]₂ with NaBH₄ in CH₂Cl₂/EtOH led to air‐ and moisture‐stable copper hydride nanoparticles (CuNPs) containing phosphinothiolates as new ligands, one of which was isolated by crystallization. The X‐ray crystal structure of [Cu₁₈H₇L₁₀I] (L=^?S(C₆H₄)PPh₂) shows unprecedented features in its 28‐atom framework (18 Cu and 10 S atoms). Seven hydrogen atoms, in hydride form, are needed for charge balance and were located by density functional theory methods. H₂ was released from the copper hydride nanoparticles by thermolysis and visible light irradiation.     

Novel high-sensitive fluorescent detection of deoxyribonuclease I based on DNA-templated gold/silver nanoclusters

Herein, fluorescent DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs) are presented as a novel probe for sensitive detection of deoxyribonuclease I (DNase I). The procedure is based on quenching fluorescence of DNA-Au/Ag NCs by DNase I digestion of the DNA (5′-CCCTTAATCCCC-3′) template. This decrease in fluorescence intensity permitted sensitive detection of DNase I in a linear range of 0.013–60 μg mL⁻¹, with a detection limit of 3 ng mL⁻¹ at a signal-to-noise ratio of 3. Furthermore, the practicality of this probe for detection of DNase I in human serum and saliva samples was validated, demonstrating its advantages of simplicity, selectivity, sensitivity and low cost. Importantly, satisfactory agreement between results obtained by the fluorescent method described here and high performance liquid chromatography (HPLC) further confirmed the reliability and accuracy of this approach.     

N-acetylcysteine induced quenching of red fluorescent oligonucleotide-stabilized silver nanoclusters and the application in pharmaceutical detection

In this work, we reported a new, simple and sensitive method for determination of N-acetylcysteine (NAC) based on quenching of the red fluorescence of oligonuleotide-protected silver nanoculsters (Ag NCs) with the quantum yield of 68.3 ± 0.3%. This method was successfully used for the assay of NAC granules presenting a linear range from 100 nM to 1200 nM (LOD of 50 nM) with minimal interferences from potential coexisting substances. It is for the first time that quenching performance of the thiol-containing compound was found to follow a non-linear Stern–Volmer profile, indicative of a complicated quenching mechanism with static quenching dominating, in which DNA-template of Ag NCs was partly replaced by NAC, as elucidated by spectral investigations. This study extended the analytical application of silver nanoclusters as well as provided a more insightful understanding of the quenching mechanism of thiol-compounds on the fluorescence of Ag NCs.     

Facile preparation of glutathione-stabilized gold nanoclusters for selective determination of chromium (III) and chromium (VI) in environmental water samples

A novel method for selective determination of Cr(III) and Cr(VI) in environmental water samples was developed based on target-induced fluorescence quenching of glutathione-stabilized gold nanoclusters (GSH-Au NCs). Fluorescent GSH-Au NCs were synthesized by a one-step approach employing GSH as reducing/protecting reagent. It was found that Cr(III) and Cr(VI) showed pH-dependent fluorescence quenching capabilities for GSH-Au NCs, and thus selective determination of Cr(III) and Cr(VI) could be achieved at different pHs. Addition of EDTA was able to effectively eliminate the interferences from other metal ions, leading to a good selectivity for this method. Under optimized conditions, Cr(III) showed a linear range of 25–3800 μg L⁻¹ and a limit of detection (LOD) of 2.5 μg L⁻¹. The Cr(VI) ion demonstrated a linear range of 5–500 μg L⁻¹ and LOD of 0.5 μg L⁻¹. The run-to-run relative standard deviations (n = 5) for Cr(III) and Cr(VI) were 3.9% and 2.8%, respectively. The recoveries of Cr(III) and Cr(VI) in environmental water samples were also satisfactory (76.3–116%). This method, with its simplicity, low cost, high selectivity and sensitivity, could be used as a promising tool for chromium analysis in environmental water samples.     

Fluorescence detection of glutathione reductase activity based on deoxyribonucleic acid-templated silver nanoclusters

Fluorescent silver nanoclusters stabilized by DNA (DNA-AgNCs) exhibit distinct response rates to thiol and disulfide. Glutathione reductase can catalyze the reduction of the oxidized glutathione (GSSG) quickly to reduced glutathione (GSH) in the presence of β-nicotinamide adenine dinucleotide 2′-phosphate reduced tetrasodium salt hydrate (NADPH). Consequently, DNA-AgNCs can serve as a new fluorescent platform for assaying the glutathione reductase (GR) activity. This newly proposed assay has a high sensitivity and a good selectivity toward GR. The GR activity can be detected in the range of 0.2–2.0 mU mL⁻¹ with a minimum detectable concentration of 0.2 mU mL⁻¹. Pepsin, lysozyme, trypsin, avidin, thrombin, myoglobin, and BSA have little effect on the fluorescence intensity of DNA-AgNCs. The GR activity assay is successfully used to monitor the inhibition of GR activity by a typical inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea.     

Nanosize Semiconductors for Photooxidation

Nanosized semiconductors (semiconductor clusters) have the potential to revolutionize the fields of photooxidation and photocatalysis through the combined effects of quantum confinement and their unique surface morphologies. Photocatalytic oxidation as applied to environmental remediation (i.e., detoxification of chemical wastes), green/sustainable chemistry, as well as alternative energy paths (i.e., splitting of H ₂ O to produce H ₂ ) has already experienced improvements in activity, efficiency, and stability through the use of semiconductor nanoclusters based on materials such as TiO ₂ , MoS ₂ , WS ₂ , MoSe ₂ , FeS ₂ , and SnO ₂ . Issues such as improved control of size and surface chemistry play an important role in the success of these semiconductor nanocatalysts. This review explores the effect of advances in the fields of nanoscience and photocatalysis for current and future applications.     

Fluorescent Gold Nanoclusters with Interlocked Staples and a Fully Thiolate‐Bound Kernel

The structural features that render gold nanoclusters intrinsically fluorescent are currently not well understood. To address this issue, highly fluorescent gold nanoclusters have to be synthesized, and their structures must be determined. We herein report the synthesis of three fluorescent Au₂₄(SR)₂₀ nanoclusters (R=C₂H₄Ph, CH₂Ph, or CH₂C₆H₄^tBu). According to UV/Vis/NIR, differential pulse voltammetry (DPV), and X‐ray absorption fine structure (XAFS) analysis, these three nanoclusters adopt similar structures that feature a bi‐tetrahedral Au₈ kernel protected by four tetrameric Au₄(SR)₅ motifs. At least two structural features are responsible for the unusual fluorescence of the Au₂₄(SR)₂₀ nanoclusters: Two pairs of interlocked Au₄(SR)₅ staples reduce the vibration loss, and the interactions between the kernel and the thiolate motifs enhance electron transfer from the ligand to the kernel moiety through the Au?S bonds, thereby enhancing the fluorescence. This work provides some clarification of the structure–fluorescence relationship of such clusters.     

Template‐Free Supracolloidal Self‐Assembly of Atomically Precise Gold Nanoclusters: From 2D Colloidal Crystals to Spherical Capsids

We report supracolloidal self‐assembly of atomically precise and strictly monodisperse gold nanoclusters involving p‐mercaptobenzoic acid ligands (Au₁₀₂‐pMBA₄₄) under aqueous conditions into hexagonally packed monolayer‐thick two‐dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template‐free manner by the spontaneous patchiness of the pMBA ligands around the Au₁₀₂‐pMBA₄₄ nanoclusters preferably towards equatorial plane, thus promoting inter‐nanocluster hydrogen bonds and high packing to planar sheets. More generally, the findings encourage to explore atomically precise nanoclusters towards highly controlled colloidal self‐assemblies.     

Site Preference in Multimetallic Nanoclusters: Incorporation of Alkali Metal Ions or Copper Atoms into the Alkynyl‐Protected Body‐Centered Cubic Cluster [Au7Ag8(C≡CtBu)12]+

The synthesis, structure, substitution chemistry, and optical properties of the gold‐centered cubic monocationic cluster [Au@Ag₈@Au₆(C≡C^tBu)₁₂]⁺ are reported. The metal framework of this cluster can be described as a fragment of a body‐centered cubic (bcc) lattice with the silver and gold atoms occupying the vertices and the body center of the cube, respectively. The incorporation of alkali metal atoms gave rise to [M_nAg_8?nAu₇(C≡C^tBu)₁₂]⁺ clusters (n=1 for M=Na, K, Rb, Cs and n=2 for M=K, Rb), with the alkali metal ion(s) presumably occupying the vertex site(s), whereas the incorporation of copper atoms produced [Cu_nAg₈Au_7?n(C≡C^tBu)₁₂]⁺ clusters (n=1–6), with the Cu atom(s) presumably occupying the capping site(s). The parent cluster exhibited strong emission in the near‐IR region (λ_max=818 nm) with a quantum yield of 2 % upon excitation at λ=482 nm. Its photoluminescence was quenched upon substitution with a Na⁺ ion. DFT calculations confirmed the superatom characteristics of the title compound and the sodium‐substituted derivatives.