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Doping Cd atom(s) into gold clusters is very promising in both theoretical study and practical applications. However, it has long been a challenge to synthesize heavily Cd-doped AuCd bimetallic clusters and thereby reveal their structure-property correlations. Herein a novel AuCd bimetallic cluster: Au16 Cd16 (SC6 H11 )20 (SC6 H11 denotes deprotonated cyclohexanethiol) with a Cd to Au atomic ratio of 1:1 is reported. The precise structure of the cluster determined by single crystal X-ray diffraction demonstrates that it has a unique hexatetrahedron Au14 core and a distinctive shell. Intriguingly, due to the special protecting motifs, the cluster exhibits high stability in various conditions studied, indicating that the geometric structure is crucial in determining the stability of the cluster. Most importantly, the photothermal property of the cluster has been investigated in comparison with those of M13 -kernel (M denotes metal atoms) clusters, and the results imply that the compactness and the Cd atom doping of the core play important roles in dictating the photothermal effect of the cluster. The authors believe that this work will provide some ideas for the rational design of clusters with high stability and excellent photothermal property.
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The capability of precisely constructing bimetallic clusters with atomic accuracy provides exciting opportunities for establishing their structure-property correlations. However, the chemistry (the charge state of precursors, the property of ligands, the amount of dopant, and so forth) dictating the fabrication of clusters with atomic-level control has been a long-standing challenge. Herein, based on the well-defined Au25(SR)18 cluster (SR = thiolates), we have systematically investigated the factors of steric hindrance and electronic effect of ligands, the charge state of Au25(SR)18, and the amount of dopant that may determine the structure of AuCd clusters. It is revealed that [Au19Cd3(SR)18]- can be obtained when a ligand of smaller steric hindrance is used, while Au24Cd(SR)18 is attained when a larger steric hindrance ligand is used. In addition, negatively charged [Au25(SR)18]- is apt to form [Au19Cd3(SR)18]- during Cd doping, while Au24Cd(SR)18 is produced when neutral Au25(SR)18 is used as a precursor. Intriguingly, the reversible transformation between [Au19Cd3(SR)18]- and Au24Cd(SR)18 is feasible by subtly manipulating ligands with different steric hindrances. Most importantly, by introducing the excess amount of dopant, a novel bimetallic cluster, Au4Cd4(SR)12 is successfully fabricated and its total structure is fully determined. The electronic structures and the chirality of Au4Cd4(SR)12 have been elucidated by density functional theory (DFT) calculations. Au4Cd4(SR)12 reported herein represents the smallest AuCd bimetallic cluster with chirality.
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Metal nanoparticles occupy an important position in electrocatalysis. Unfortunately, by using conventional synthetic methodology, it is a great challenge to realize the monodisperse composition/structure of metal nanoparticles at the atomic level, and to establish correlations between the catalytic properties and the structure of individual catalyst particles. For the study of well-defined nanocatalysts, great advances have been made for the successful synthesis of nanoparticles with atomic precision, notably ligand-passivated metal nanoclusters. Such well-defined metal nanoclusters have become a type of model catalyst and have shown great potential in catalysis research. In this review, the authors summarize the advances in the utilization of atomically precise metal nanoclusters for electrocatalysis. In particular, the factors (e.g., size, metal doping/alloying, ligand engineering, support materials as well as charge state of clusters) affecting selectivity and activity of catalysts are highlighted. The authors aim to provide insightful guidelines for the rational design of electrocatalysts with high performance and perspectives on potential challenges and opportunities in this emerging field.
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Protein disulfide isomerase (PDI), a chaperone protein mostly in endoplasmic reticulum, catalyzes disulfide bond breakage, formation, and rearrangement to promote protein folding. PDI is regarded as a new target for treatment of several disorders. Here, based on the combination principle, we report a new PDI reversible modulator 16F16A-NO by replacing the reactive group in a known PDI inhibitor 16F16 with nitric oxide (NO) donor. Using molecular docking experiment, 16F16A-NO could embed into the active cavity of PDI. From newly developed fluorescent assay, 16F16A-NO showed rapid NO release. Furthermore, it is capable to moderately inhibit activity of PDI and S-nitrosylate the protein, indicating by insulin aggregation assay and biotin-switch technique. Finally, it displayed a dose-dependent antiproliferative activity against SH-SY5Y and HeLa tumor cells. Our designed hybrid compound 16F16A-NO showed a reasonable activity and might offer a promising avenue to develop novel PDI inhibitors for disease treatments.
Asunto(s)
Diseño de Fármacos , Inhibidores Enzimáticos/síntesis química , Donantes de Óxido Nítrico/química , Óxido Nítrico/metabolismo , Proteína Disulfuro Isomerasas/antagonistas & inhibidores , Sitios de Unión , Dominio Catalítico , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Inhibidores Enzimáticos/metabolismo , Inhibidores Enzimáticos/farmacología , Humanos , Simulación del Acoplamiento Molecular , Donantes de Óxido Nítrico/metabolismo , Donantes de Óxido Nítrico/farmacología , Proteína Disulfuro Isomerasas/metabolismoRESUMEN
Ligand-induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical [Au25 (SR1 )18 ]- cluster (1) while maintaining its icosahedral Au13 core for the synthesis of a new bimetallic [Au19 Cd3 (SR2 )18 ]- cluster (2). Single-crystal X-ray diffraction studies reveal that six bidentate Au2 (SR1 )3 motifs (L2) attached to the Au13 core of 1 were replaced by three quadridentate Au2 Cd(SR2 )6 motifs (L4) to create a bimetallic cluster 2. Experimental and theoretical results demonstrate a stronger electronic interaction between the surface motifs (Au2 Cd(SR2 )6 ) and the Au13 core, attributed to a more compact cluster structure and a larger energy gap of 2 compared to that of 1. These factors dramatically enhance the photoluminescence quantum efficiency and lifetime of crystal of the cluster 2. This work provides a new route for the design of a wide range of bimetallic/alloy metal nanoclusters with superior optoelectronic properties and functionality.
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The emergence of thiolated metal nanoclusters provides opportunities to identify significant and unprecedented phenomena because they are at quantum sizes and can be characterized with X-ray crystallography. Recently silver nanoclusters have received extensive interest owing to their merits, such as low-cost and rich properties. Herein, a thiolated silver nanocluster [Ag46 S7 (SPhMe2 )24 ]NO3 (Ag46 for short) with a face-centered cubic (fcc) structure was successfully synthesized and structurally resolved by X-ray analysis. Most importantly, interstitial sulfur was found in the lattice void of Ag46 without lattice distortion or expansion, indicating that the classic theory of interstitial metal solid solutions might be not applicable at quantum size. Furthermore, unprecedented chemical bonds and unique structural features (such as asymmetrically coordinated µ4 -S) were found in Ag46 and might be related to the interstitial sulfur, which is supported by natural population analyses.
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Anti-galvanic reaction (AGR) not only defies classic galvanic theory but is a promising method for tuning the compositions, structures, and properties of noble-metal nanoparticles. Employing AGR for the preparation of alloy nanoparticles has recently received great interest. Herein, we report an unprecedented alloying mode by way of AGR, in which foreign atoms induce structural transformation of the mother nanoparticles and enter the nanoparticles in a non-replacement fashion. A novel, active-metal-doped, gold nanoparticle was synthesized by this alloying mode, and its structure resolved. A CdSH motif was found in the protecting staples of the bimetal nanoparticle. DFT calculations revealed that the Au20 Cd4 (SH)(SR)19 nanoparticle is a 8e superatom cluster. Furthermore, although the Cd-doping does not essentially alter the absorption spectrum of the mother nanocluster, it distinctly enhances the stability and catalytic selectivity of the mother nanoclusters.
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The 18-electron shell closure structure of Au nanoclusters protected by thiol ligands has not been reported until now. Herein, we synthesize a novel nanocluster bearing the same gold atom number but a different thiolate number as another structurally resolved nanocluster Au44(TBBT)28 (TBBTH = 4-tert-butylbenzenelthiol). The new cluster was determined to be Au44(2,4-DMBT)26 (2,4-DMBTH = 2,4-dimethylbenzenethiol) using multiple techniques, including mass spectrometry and single crystal X-ray crystallography (SCXC). Au44(2,4-DMBT)26 represents the first 18-electron closed-shell gold nanocluster. SCXC reveals that the atomic structure of Au44(2,4-DMBT)26 is completely different from that of Au44(TBBT)28 but is similar to the structure of Au38Q. The arrangement of staples (bridging thiolates) and part of the Au29 kernel atom induces the chirality of Au44(2,4-DMBT)26. The finding that a small portion of the gold kernel exhibits chirality is interesting because it has not been previously reported to the best of our knowledge. Although Au44(2,4-DMBT)26 bears an 18-electron shell closure structure, it is less thermostable than Au44(TBBT)28, indicating that multiple factors contribute to the thermostability of gold nanoclusters. Surprisingly, the small difference in Au/thiolate molar ratio between Au44(2,4-DMBT)26 and Au44(TBBT)28 leads to a dramatic distinction in Au 4f X-ray photoelectron spectroscopy, where it is found that the charge state of Au in Au44(2,4-DMBT)26 is remarkably more positive than that in Au44(TBBT)28 and even slightly more positive than the charge states of gold in Au-(2,4-DMBT) or Au-TBBT complexes.
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"Size-focusing" is a well-recognized process and widely employed for the synthesis of atomically monodisperse metal nanoclusters. However, quantitatively monitoring the size-focusing of Au nanoclusters has not been achieved yet, and the in-depth understanding of the size focusing is far from completed. Herein, we introduce a facile, cheap, and powerful tool, preparative thin-layer chromatography (PTLC), to quantitatively track the size-focusing process, to reveal that mainly â¼3 nm nanoparticles promote the transformation from Au44(TBBT)28 to Au36(TBBT)24 (where TBBT is 4-tert-butylbenzenethiolate) and to improve the syntheses of Au44(TBBT)28 and Au36(TBBT)24. Our work further demonstrates the usefulness of PTLC in nanocluster research and advances one step toward understanding the "size-focusing" process of nanoclusters.
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Alloy nanoparticles with atomic monodispersity is of importance for some fundamental research (e.g., the investigation of active sites). However, the controlled preparation of alloy nanoparticles with atomic monodispersity has long been a major challenge. Herein, for the first time a unique method, antigalvanic reduction (AGR), is introduced to synthesize atomically monodisperse Au25Ag2(SC2H4Ph)18 in high yield (89%) within 2 min. Interestingly, the two silver atoms in Au25Ag2(SC2H4Ph)18 do not replace the gold atoms in the precursor particle Au25(SC2H4Ph)18 but collocate on Au25, which was supported by experimental and calculated results. Also, the two silver atoms are active to play roles in stabilizing the alloy nanoparticle, triggering the nanoparticle fluorescence and catalyzing the hydrolysis of 1,3-diphenylprop-2-ynyl acetate.
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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=C2 H4 Ph, CH2 Ph, or CH2 C6 H4 (t) Bu). 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.
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Controlling the dopant type, number, and position in doped metal nanoclusters (nanoparticles) is crucial but challenging. In the work described herein, we successfully achieved the mono-cadmium doping of Au25 nanoclusters, and revealed using X-ray crystallography in combination with theoretical calculations that one of the inner-shell gold atoms of Au25 was replaced by a Cd atom. The doping mode is distinctly different from that of mono-mercury doping, where one of the outer-shell Au atoms was replaced by a Hg atom. Au24Cd is readily transformed to Au24Hg, while the reverse (transformation from Au24Hg to Au24Cd) is forbidden under the investigated conditions.
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Controlling the bimetal nanoparticle with atomic monodispersity is still challenging. Herein, a monodisperse bimetal nanoparticle is synthesized in 25% yield (on gold atom basis) by an unusual replacement method. The formula of the nanoparticle is determined to be Au24Hg1(PET)18 (PET: phenylethanethiolate) by high-resolution ESI-MS spectrometry in conjunction with multiple analyses including X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). X-ray single-crystal diffraction reveals that the structure of Au24Hg1(PET)18 remains the structural framework of Au25(PET)18 with one of the outer-shell gold atoms replaced by one Hg atom, which is further supported by theoretical calculations and experimental results as well. Importantly, differential pulse voltammetry (DPV) is first employed to estimate the highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energies of Au24Hg1(PET)18 based on previous calculations.
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Due to their intriguing ring structures and promising applications, nickel-thiolate clusters, such as [Nin(SR)2n] (n = 4-6), have attracted tremendous interest. However, investigation of the synthesis, structures, and properties of macrocyclic Nin clusters (n > 8) has been seriously impeded. In this work, a homologous series of macrocyclic nickel clusters, Nin(4MPT)2n (n = 9-12), was fabricated by using 4-methylphenthiophenol (4MPT) as the ligand. The structures and compositions of the clusters were determined by single-crystal X-ray diffraction (SXRD) in combination with electrospray ionization mass spectrometry (ESI-MS). Experimental results and theoretical calculations show that the electronic structures of the clusters do not change significantly with the increase of Ni atoms. The coordination interactions between Ni and S atoms in [NiS4] subunits are proved to play a crucial rule in the remarkable stability of Ni clusters. Finally, these clusters display excellent catalytic activity towards the reduction of p-nitrophenol, and a linear correlation between catalytic activity and ring size was revealed. The study provides a facile approach to macrocyclic homoleptic nickel clusters, and contributes to an in-depth understanding of the structure-property correlations of nickel clusters at the atomic level.
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Flexible Zn-air batteries (ZABs) draw much attention due to the merits of high energy density, stability, and safety, and show potential applications for wearable devices. However, the development of flexible ZABs with great energy density, high round-trip efficiency, and long cycle life for practical applications is highly restricted by the lack of highly active oxygen catalysts, high ion-conducting solid-state electrolytes, appropriate Zn anodes, and advanced battery configuration. Promising oxygen catalysts should possess both, superior oxygen reduction reaction and oxygen evolution reaction performance and can be directly used as self-supporting cathodes without loading catalysts on support materials such as carbon cloth. In addition, electrolytes play an important role in ZABs; a good electrolyte should be in all-solid state with high ion conductivity. Moreover, for an excellent Zn anode, it is required to stably contact the electrolyte interface during the bending process. Therefore, in this review, recent advances in ZABs are summarized, including: i) the powder and 3D self-supporting oxygen catalysts, ii) the species of solid-state electrolytes, and iii) the rational design of Zn anodes. Finally, the challenges and opportunities of this promising field are presented.
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Exposing and stabilizing undercoordinated platinum (Pt) sites and therefore optimizing their adsorption to reactive intermediates offers a desirable strategy to develop highly efficient Pt-based electrocatalysts. However, preparation of atomically controllable Pt-based model catalysts to understand the correlation between electronic structure, adsorption energy, and catalytic properties of atomic Pt sites is still challenging. Herein we report the atomically thin two-dimensional PtTe2 nanosheets with well-dispersed single atomic Te vacancies (Te-SAVs) and atomically well-defined undercoordinated Pt sites as a model electrocatalyst. A controlled thermal treatment drives the migration of the Te-SAVs to form thermodynamically stabilized, ordered Te-SAV clusters, which decreases both the density of states of undercoordinated Pt sites around the Fermi level and the interacting orbital volume of Pt sites. As a result, the binding strength of atomically defined Pt active sites to H intermediates is effectively reduced, which renders PtTe2 nanosheets highly active and stable in hydrogen evolution reaction.
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Single-atom catalysts (SACs) represent a new frontier in heterogeneous catalysis due to their remarkable catalytic properties and maximized atomic utilization. However, single atoms often bond to the support with polarized electron density and thus exhibit a high valence state, limiting their catalytic scopes in many chemical transformations. Here, it is demonstrated that 2D black phosphorus (BP) acts as giant phosphorus (P) ligand to confine a high density of single atoms (e.g., Pd1 , Pt1 ) via atomic layer deposition. Unlike other 2D materials, BP with relatively low electronegativity and buckled structure favors the strong confinement of robust zero-valent palladium SACs in the vacancy site. Metallic Pd1 /BP SAC shows a highly selective semi-hydrogenation of phenylacetylene toward styrene, distinct from metallic Pd nanoparticles that facilitate the formation of fully hydrogenated products. Density functional theory calculations reveal that Pd atom forms covalent-like bonding with adjacent P atoms, wherein H atoms tend to adsorb, aiding the dissociative adsorption of H2 . Zero-valent Pd in the confined space favors a larger energy gain for the synthesis of partially hydrogenated product over the fully hydrogenated one. This work provides a new route toward the synthesis of zero-valent SACs on BP for organic transformations.
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Parkinson's disease (PD), the second most common chronic neurodegenerative disorder, broadly remains incurable. Both genetic susceptibility and exposure to deleterious environmental stimuli contribute to dopaminergic neuron degeneration in the substantia nigra. Hence, reagents that can ameliorate the phenotypes rendered by genetic or environmental factors should be considered in PD therapy. In this study, we found that polydatin (Pol), a natural compound extracted from grapes and red wines, significantly attenuated rotenone- (Rot) or Parkin deficiency-induced mitochondrial dysfunction and cell death in SH-SY5Y, a human dopaminergic neuronal cell line. We showed that Pol significantly attenuated the Rot-induced decrease in cell viability, mitochondrial membrane potential (MMP), and Sirt 1 expression and increase in cell death, reactive oxygen species (ROS) and DJ1 expression. Rot resulted in a decrease in mTOR/Ulk-involved autophagy and an increase in PGC1ß/mfn2-involved mitochondrial fusion, which was inhibited by Pol. We further demonstrated that the protective effects of Pol are partially blocked when autophagy-related gene 5 (Atg5) is genetically inactivated, suggesting that Pol-mediated neuroprotection requires Atg5. Moreover, Pol rescued Parkin knockdown-induced oxidative stress, mitochondrial dysfunction, autophagy impairment, and mitochondrial fusion enhancement. Interestingly, Pol treatment could also rescue the mitochondrial morphological abnormality and motorial dysfunction of a Drosophila PD model induced by Parkin deficiency. Thus, Pol could represent a useful therapeutic strategy as a disease-modifier in PD by decreasing oxidative stress and regulating autophagic processes and mitochondrial fusion.
Asunto(s)
Proteína 5 Relacionada con la Autofagia/metabolismo , Autofagia/efectos de los fármacos , Enfermedad de Parkinson/tratamiento farmacológico , Rotenona/farmacología , Ubiquitina-Proteína Ligasas/metabolismo , Autofagia/fisiología , Muerte Celular/efectos de los fármacos , Neuronas Dopaminérgicas/metabolismo , Humanos , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Potencial de la Membrana Mitocondrial/fisiología , Fármacos Neuroprotectores/farmacología , Enfermedad de Parkinson/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Ubiquitina-Proteína Ligasas/efectos de los fármacosRESUMEN
The ability to precisely engineer the doping of sub-nanometer bimetallic clusters offers exciting opportunities for tailoring their catalytic performance with atomic accuracy. However, the fabrication of singly dispersed bimetallic cluster catalysts with atomic-level control of dopants has been a long-standing challenge. Herein, we report a strategy for the controllable synthesis of a precisely doped single cluster catalyst consisting of partially ligand-enveloped Au4Pt2 clusters supported on defective graphene. This creates a bimetal single cluster catalyst (Au4Pt2/G) with exceptional activity for electrochemical nitrogen (N2) reduction. Our mechanistic study reveals that each N2 molecule is activated in the confined region between cluster and graphene. The heteroatom dopant plays an indispensable role in the activation of N2 via an enhanced back donation of electrons to the N2 LUMO. Moreover, besides the heteroatom Pt, the catalytic performance of single cluster catalyst can be further tuned by using Pd in place of Pt as the dopant.
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Metal nanoclusters provide excellent references for understanding metal nanoparticle surfaces, which remain mysterious due to the difficulty of atomically precise characterization. Although some remarkable advances have been achieved for understanding the structure of metal nanoclusters, it is still unknown if the inner kernel-outer staples match is a key-lock match and how the surface staples influence some of the properties of metal nanoclusters. Herein, we have developed an acid-induction method for synthesizing a novel gold nanocluster whose composition is determined to be Au42(TBBT)26 (TBBT: 4-tert-butylbenzenelthiolate) by ESI-MS and single-crystal X-ray crystallography (SCXC). SCXC also reveals that Au42(TBBT)26 has an identical kernel but different staples with an existing gold nanocluster Au44(TBBT)28, indicating that the kernel-staples match is not a key-lock match and the existence of homo-ligand-homo-kernel-hetero-staples phenomenon in metal nanoclusters provides some reference for understanding the growth or transformation of metal nanoclusters. Further experiments reveal that the staples greatly contribute to the stability of gold nanoclusters and influence their photoluminescence intensity and that minute differences in the interfacial structure can lead to enhanced stability and photoluminescence.