RESUMEN
Ligand-protected metal clusters possess hybrid properties that seamlessly combine an inorganic core with an organic ligand shell, imparting them exceptional chemical flexibility and unlocking remarkable application potential in diverse fields. Leveraging chemical flexibility to expand the library of available materials and stimulate the development of new functionalities is becoming an increasingly pressing requirement. This Review focuses on the origin of chemical flexibility from the structural analysis, including intra-cluster bonding, inter-cluster interactions, cluster-environments interactions, metal-to-ligand ratios, and thermodynamic effects. In the introduction, we briefly outline the development of metal clusters and explain the differences and commonalities of M(I)/M(I/0) coinage metal clusters. Additionally, we distinguish the bonding characteristics of metal atoms in the inorganic core, which give rise to their distinct chemical flexibility. Section 2 delves into the structural analysis, bonding categories, and thermodynamic theories related to metal clusters. In the following sections 3 to 7, we primarily elucidate the mechanisms that trigger chemical flexibility, the dynamic processes in transformation, the resultant alterations in structure, and the ensuing modifications in physical-chemical properties. Section 8 presents the notable applications that have emerged from utilizing metal clusters and their assemblies. Finally, in section 9, we discuss future challenges and opportunities within this area.
RESUMEN
Through Smad3-dependent signalings, transforming growth factor-ß (TGF-ß) suppresses the development, maturation, cytokine productions and cytolytic functions of NK cells in cancer. Silencing Smad3 remarkably restores the cytotoxicity of NK-92 against cancer in TGF-ß-rich microenvironment, but its effects on the immunoregulatory functions of NK cells remain obscure. In this study, we identified Smad3 functioned as a transcriptional repressor for CSF2 (GM-CSF) in NK cells. Therefore, disrupting Smad3 largely mitigated TGF-ß-mediated suppression on GM-CSF production by NK cells. Furthermore, silencing GM-CSF in Smad3 knockout NK cells substantially impaired their anti-lung carcinoma effects. In-depth study demonstrated that NK-derived GM-CSF strengthened T cell immune responses by stimulating dendritic cell differentiation and M1 macrophage polarization. Meanwhile, NK-derived GM-CSF promoted the survival of neutrophils, which in turn facilitated the terminal maturation of NK cells, and subsequently boosted NK-cell mediated cytotoxicity against lung carcinoma. Thus, Smad3-silenced NK-92 (NK-92-S3KD) may serve as a promising immunoadjuvant therapy with clinical translational value given its robust cytotoxicity against malignant cells and immunostimulatory functions to reinforce the therapeutic effects of other immunotherapies.
Asunto(s)
Factor Estimulante de Colonias de Granulocitos y Macrófagos , Células Asesinas Naturales , Neoplasias Pulmonares , Proteína smad3 , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/metabolismo , Factor Estimulante de Colonias de Granulocitos y Macrófagos/metabolismo , Factor Estimulante de Colonias de Granulocitos y Macrófagos/genética , Proteína smad3/metabolismo , Proteína smad3/genética , Neoplasias Pulmonares/inmunología , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/genética , Animales , Humanos , Ratones , Ratones Endogámicos C57BL , Línea Celular Tumoral , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Diferenciación Celular , Macrófagos/metabolismo , Macrófagos/inmunología , Transducción de SeñalRESUMEN
Atom-precise metal nanoclusters (NCs) with large bulk (nuclearity >60) are important species for insight into the embryonic phase of metal nanoparticles and their top-down etching synthesis. Herein, we report a metastable rod-shaped 70-nuclei copper-hydride NC, [Cl@Cu70H22(PhC≡C)29(CF3COO)16]2+ (Cu70), with Cl- as the template, in which the Cl@Cu59 kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu70 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu70 could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu8, A-A-type Cu22, A-B-type Cu23, and A-B-A-type Cu38) upon etching by p-tert-butylthiacalix[4]arene (H4TC4A), which could not be achieved by "one-pot" synthetic methods. Notably, the patterns of A and B blocks in the Cu NCs could be effectively modulated by employing appropriate counterions and blockers, and the modular assembly mechanism was illustrated through comprehensive solution chemistry analysis using HR-ESI-MS. Furthermore, catalytic investigations reveal that Cu38 could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2 under mild conditions. This work not only enriched the family of high-nuclear copper-hydride NCs but also provided new insights into the growth mechanism of metal NCs.
RESUMEN
Luminescent metal-organic cages are of great interest in contemporary research; however, their designed synthesis remains challenging. Here, we created metal-cluster-derived spacers, where emissive C3-symmetric Cu4 clusters have three arms modified by benzene alkynyl ligands, which are terminally functionalized by extensile -COOH and 15-crown-5-ether groups with directional coordination ability. Through vertex orientation, -COOH-functionalized cluster-based spacers coassembled with paddle-wheel Cu(I)xZn(II)2-x(COO)3 nodes in 3+3 mode, generating an emissive cubic cage, which subsequently gave another distorted cubic cage by synthetic modification on the nodes. Through face orientation, 15-crown-5-ether-containing cluster-based spacers capturing K+ ions in 3+2 mode produced an octahedral cage whose empty phase showed dual emission peaks, leading to diverse stimuli-responsive photoluminescence. This work provides new design and synthesis strategies for the integration of nodes and spacers based on metal clusters for cage materials as well as prototypes of luminescent metal-cluster cages for important sensing applications.
RESUMEN
The manipulation of metal cluster enantiomers and their reconstruction remain challenging. Here, for the first time, we report an enantiomeric pair of hydride copper clusters [Cu18H(R/S-PEA)12](BF4)5 (R/S-Cu18H) made using designed chiral ligands. By manipulation of R/S-Cu18H with Ag+ ions, H- ions are released, leading to the reconstruction of 15 Cu atoms. Moreover, 4 Ag atoms replaced Cu atoms at the specific sites, resulting in the formation of homochiral [Cu15Ag4(R/S-PEA)12](BF4)5 (R/S-Cu15Ag4) with an isomorphic metal skeleton. This process was accompanied by a reduction reaction generating two free valence elections in the chiral alloying counterparts, which displayed orange emission. The solid-state R/S-Cu15Ag4 exhibited a photoluminescence quantum yield of 7.02% and excellent circularly polarized luminescence. The chiral transformations were resolved by single-crystal X-ray diffraction. The development of chiral copper hydride precursor-based metal clusters with chiroptical activities holds tremendous promise for advancing the field of optoelectronics and enabling new applications in lighting, displays, and beyond.
RESUMEN
Anisotropy is an intrinsic property of crystalline materials. However, the photoluminescence anisotropy in eutectic crystals of organometallic complexes has remained unexplored. Herein, the eutectic of polynuclear lanthanide complexes and Ag clusters was prepared, and the crystal shows significant photoluminescence anisotropy. The polarization anisotropy of emission δ and degree of excitation polarization P are 2.62 and 0.53, respectively. The rare excitation polarization properties have been proved to be related to the regular arrangement of electric transition dipole moments of luminescent molecules in the crystal. Our design provides a reference for developing new photoluminescence anisotropy materials and expanding their applications.
RESUMEN
Understanding how the chiral or achiral section in chiral nanostructures contributes to circularly polarized light emission (CPLE) at the atomic level is of fundamental importance. Here, we report two pairs of atomically precise enantiomers of homosilver (R/S-Ag12Ag32) and heterometal (R/S-Au12Ag32) clusters. The geometrical chirality of R/S-Ag12Ag32 arises from the chiral ligand and interface consisting of positive moieties of Ag32(R/S-PS)24. The circular dichroism of R/S-Ag12Ag32 is active, but CPLE-silent. A complete metal change from Ag12 to Au12 in the achiral core section of S2-@M12@S8 engenders isomorphous heterometal R/S-Au12Ag32, which activates CPLE. We further quantify the contributions of achiral and chiral sections and for the first time unveil that heterometal bonding (Au12-Ag32) at the linkage varies the delocalization of orbitals and proportion of achiral and chiral section in electron transition-involved orbitals, thus activating CPLE. Based on these unique atomically precise homochiral metal clusters, our work provides a new insight into the contributions of achiral and chiral sections to the origin of chiroptical response of chiral metal clusters, paving the way to advance the development of CPLE nanoparticles.
Asunto(s)
Nanopartículas , Nanoestructuras , Estereoisomerismo , Dicroismo Circular , Nanopartículas/química , MetalesRESUMEN
Stable stimulus-responsive materials are highly desirable due to their widespread potential applications and growing demand in recent decades. Despite the fact that viologen derivatives have long been known as excellent photochromic and electrochromic materials, the development of stable viologen-based multifunctional smart materials with short coloration times remains an exciting topic. To obtain photochromic and electrochromic dual responsive materials, embedding the viologen ligand into a robust metal oxide cluster to increase its stability and sensitivity is an effective strategy. Herein, a viologen-based metal-organic polyhedron (MOP) {[Zr6L3(µ3-O)2(µ2-OH)6Cp6]·8Cl·CH3OH·DMF} [Zr-MOP-1; H2L·2Cl = 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium dichloride, and Cp = η5-C5H5] was successfully prepared and characterized. It consists of trinuclear Zr-oxygen secondary building units and exhibits reversible photochromic and electrochromic dual responsive behaviors. As expected, the designed robust viologen-based nanocage with a V2E3 (V = vertex, and E = edge) topology can maintain its stability and rapid photo/electrochromic behaviors with an obvious reversible change in color from purple (brown) to green, mainly due to the enclosed cluster structure and the abundant free viologen radicals that originate from the effective Cl â N and O â N electron transfers. Spectroelectrochemistry and theoretical calculations of this Zr-MOP were also performed to verify the chromic mechanism.
RESUMEN
Continuing research on the preparation and structural determination of monolayer-protected silver clusters has been performed. The compounds include mixed-valence Ag0/1+ clusters and single-valence Ag1+ clusters, which contain a few to tens or hundreds of Ag atoms that are protected by organic ligands. Sometimes, counter ions and extraneous species appear in their crystalline state. These non-metal parts define the shell layers of silver clusters. Strong coordination bonds and weak supramolecular interactions have been employed not only to modify the shell configurations and components of discrete silver clusters but also to hierarchically assemble silver clusters, producing novel cluster-based functional materials with unexpected physical and chemical properties. Atomically-precise structures help to map out definite electronic structures and structure-property correlations, enabling precise control of shell layers to achieve desired stability and specific functionalities. In this Tutorial Review, based on classic silver cluster paradigms, we first summarize the strategies and recent advances in precise modification and hierarchical assembly of well-defined silver clusters through shell engineering. Second, the correlations of structure-property and structure-functionality are summarized. Of these, the most important is structure-luminescence relationship, which is discussed in detail. In this topic, the uniqueness and prospect of silver clusters as potential lighting materials are scrutinized. Finally, the existing challenges and perspectives of functional silver clusters are presented. The general strategic design presented in this Review will motivate researchers to exploit the development of functionality-oriented materials based on nanosized building blocks in the enrichment of nanotechnology and material science.
RESUMEN
Access to healthcare, including physiotherapy, is increasingly occurring through virtual formats. At-home adherence to physical therapy programs is often poor and few tools exist to objectively measure participation. The aim of this study was to develop and evaluate the potential for performing automatic, unsupervised video-based monitoring of at-home low-back and shoulder physiotherapy exercises using a mobile phone camera. Joint locations were extracted from the videos of healthy subjects performing low-back and shoulder physiotherapy exercises using an open source pose detection framework. A convolutional neural network was trained to classify physiotherapy exercises based on the segments of keypoint time series data. The model's performance as a function of input keypoint combinations was studied in addition to its robustness to variation in the camera angle. The CNN model achieved optimal performance using a total of 12 pose estimation landmarks from the upper and lower body (low-back exercise classification: 0.995 ± 0.009; shoulder exercise classification: 0.963 ± 0.020). Training the CNN on a variety of angles was found to be effective in making the model robust to variations in video filming angle. This study demonstrates the feasibility of using a smartphone camera and a supervised machine learning model to effectively classify at-home physiotherapy participation and could provide a low-cost, scalable method for tracking adherence to physical therapy exercise programs in a variety of settings.
Asunto(s)
Ejercicio Físico , Modalidades de Fisioterapia , Humanos , Terapia por Ejercicio/métodos , Redes Neurales de la Computación , Aprendizaje AutomáticoRESUMEN
Subtle tailoring of gold nanoclusters (NCs) could significantly change their physicochemical properties. However, direct comparison of the catalytic performance of gold NCs with identical metal cores but distinct ligand shells is rarely elucidated. In this work, a novel gold NC, Au28 (C2 B10 H11 S)12 (tht)4 Cl4 (Au28 -S), was isolated by a facile self-reducing synthesis. Au28 -S adopts an identical Au28 metal framework to that of the reported alkynyl-protected Au28 -C. The different protective layers lead to distinctions in their electronic structure and optical properties. Furthermore, Au28 -S shows better catalytic activity for the electrochemical reduction of CO2 to CO. Theoretical calculations identified the active sites and shed light on the catalytic mechanism to elucidate the different catalytic performances. This work provides an ideal platform to study the protective layer-activity relationship of gold NCs, and may also provide guidance in the design of metal NC-based catalysts.
RESUMEN
Atomically precise copper clusters are highly desirable catalysts for electrocatalytic CO2 reduction reaction (CO2 RR) and provide an ideal platform for elaborating structure-activity relationships. However, systematic comparative studies of Cu cluster isomers for electrocatalytic CO2 RR are lacking because they are challenging to synthesize. A group of structurally precise Cu8 cluster isomers with different core structures (cube- and ditetrahedron-shaped) were developed and investigated for highly active and selective CO2 reduction. Electrocatalytic measurements showed that the ditetrahedron-shaped Cu8 cluster exhibited a higher FEHCOOH (≈92 %) at -1.0â V and higher selectivity than the cube-shaped cluster. Theoretical investigations revealed different levels of competitiveness with the hydrogen evolution reaction on the respective core-shaped Cu8 clusters and decreased free energies for the adsorbed HCOO* intermediates on the ditetrahedron-shaped Cu8 clusters.
RESUMEN
Atomically precise metal clusters are attractive as highly efficient catalysts, but suffer from continuous efficiency deactivation in the catalytic process. Here, we report the development of an efficient strategy that enhances catalytic performance by electropolymerization (EP) of metal clusters into hybrid materials. Based on carbazole ligand protection, three polymerized metal-cluster hybrid materials, namely Poly-Cu14 cba, Poly-Cu6 Au6 cbz and Poly-Cu6 Ag4 cbz, were prepared. Compared with isolated metal clusters, metal clusters immobilizing on a biscarbazole network after EP significantly improved their electron-transfer ability and long-term recyclability, resulting in higher catalytic performance. As a proof-of-concept, Poly-Cu14 cba was evaluated as an electrocatalyst for reducing nitrate (NO3 - ) to ammonia (NH3 ), which exhibited ≈4-fold NH3 yield rate and ≈2-fold Faraday efficiency enhancement compared to that of Cu14 cba with good durability. Similarly, Poly-Cu6 Au6 cbz showed 10â times higher photocatalytic efficiency towards chemical warfare simulants degradation than the cluster counterpart.
RESUMEN
Four pairs of defective crystals exhibiting full-color emission and circularly polarized luminescence (CPL) with high luminescence dissymmetry factor (glum) values (â¼3 × 10-3) were successfully obtained by doping dye molecules into the chiral crystalline metal cluster-based matrixes. The dye molecules function as defect inducers and confer fluorescence on the crystals. Studies reveal that electrostatic interactions provide the main impetus in generating defective crystals, and the restricted effect of chiral space and the weak interactions in defect crystal enable the efficient chiral transfer from the intrinsically chiral host silver(I) clusters to achiral luminescent dopants and finally induce them to emit bright CPL. This defect engineering strategy opens a new way to versatile functions for crystalline cluster-based materials.
RESUMEN
We report a new enantiomeric pair of superatomic silver clusters, R/S-Ag17, prepared from chiral alkynyl ligands. R-Ag17 and S-Ag17 possess C3 symmetry and emit near-infrared (NIR) light with a quantum yield (QY) of 8.0% under ambient condition as well as NIR circularly polarized luminescence (CPL) as a result of the chirality of the excited states. Both experiments and theoretical calculations indicate for the first time that the CPL originates from transitions between superatomic 1Pz (along the C3 axis) and 1S orbitals. This work opens a new avenue for CPL-active metal nanoclusters by utilizing chiral alkynyl ligands and enlightens the chirality transfer from chiral protecting ligands to superatomic states in metal clusters.
RESUMEN
Here we report a neutral fullerene-like core-shell homosilver Ag13@Ag20 nanocluster that is fully protected by an achiral bidentate thiolate ligand (9,12-dimercapto-1,2-closo-carborane, C2B10H10S2H2), which crystallizes in centrosymmetric space group R3Ì . Continuous Cu doping in the dodecahedral shell first induced symmetry breaking to generate chiral Ag13@Ag20-nCun (6 ≥ n ≥ 2) containing two acetonitrile ligands in space group P212121, and then produced symmetric all-thiolated Ag13@Ag20-nCun (20 ≥ n ≥ 13) in the higher space group Im3Ì . The selectively copper-doped Ag13@Ag20-nCun (6 ≥ n ≥ 2) cluster has its structure reorganized to a lower symmetry that shows chiroptical activity. Moreover, structural distortion of Ag13@Ag20-nCun (6 ≥ n ≥ 2) further expanded in chiral R-/S-propylene oxide, which induced a more prominent core-based CD response. This work revealed a novel mechanism of chirality generation at the atomic level through asymmetric shell-doping of metal nanoclusters, which provides new insight into the origin of chirality in inorganic nanostructures.
RESUMEN
Natural killer (NK) cell is a powerful malignant cells killer, providing rapid immune responses via direct cytotoxicity without the need of antigen processing and presentation. It plays an essential role in preventing early tumor, metastasis and minimal residual disease. Although adoptive NK therapies achieved great success in clinical trials against hematologic malignancies, their accumulation, activation, cytotoxic and immunoregulatory functions are severely impaired in the immunosuppressive microenvironment of solid tumors. Now with better understandings of the tumor evasive mechanisms from NK-mediated immunosurveillance, immunotherapies targeting the key molecules for NK cell dysfunction and exhaustion have been developed and tested in both preclinical and clinical studies. In this review, we introduce the challenges that NK cells encountered in solid tumor microenvironment (TME) and the therapeutic approaches to overcome these limitations, followed by an outline of the recent preclinical advances and the latest clinical outcomes of NK-based immunotherapies, as well as promising strategies to optimize current NK-targeted immunotherapies for solid tumors.
Asunto(s)
Células Asesinas Naturales/inmunología , Neoplasias/inmunología , Neoplasias/terapia , Animales , Neoplasias Hematológicas/inmunología , Neoplasias Hematológicas/terapia , Humanos , Inmunoterapia/métodos , Microambiente Tumoral/inmunologíaRESUMEN
Structure evolution has become an effective way to assemble novel monolayer-protected metal nanomolecules. However, evolution with alkynyl-stabilized metal clusters still remains rarely explored. Herein, we present a carboranealkynyl-protected gold nanocluster [Au28 (C4 B10 H11 )12 (tht)8 ]3+ (Au28 , tht=tetrahydrothiophene) possessing an open-shell electronic structure with 13 free electrons, which was isolated by a facile self-reduction method with 9-HC≡C-closo-1,2-C2 B10 H11 as the two-in-one reducing and protecting agent. Notably, Au28 undergoes a complete transformation in methanol into a stable and smaller-sized nanocluster [Au23 (C4 B10 H11 )9 (tht)6 ]2+ (Au23 ) bearing 12 valence electrons and crystal-field-like split superatomic 1D orbitals. The transformation process was systematically monitored with ESI-MS and UV/Vis absorption spectra. Au28 and Au23 both display optical absorption covering the UV/Vis-NIR range and NIR emission, which facilitates their potential application in the biomedical and photocatalytic fields.
RESUMEN
Acidic oxygen reduction is vital for renewable energy devices such as fuel cells. However, many aspects of the catalytic process are still uncertain-especially the large difference in activity in acidic and alkaline media. Thus, the design and synthesis of model catalysts to determine the active centers and the inactivation mechanism are urgently needed. We report a pyrolysis-free synthesis route to fabricate a catalyst (CPF-Fe@NG) for oxygen reduction in acidic conditions. By introducing a deprotonation process, we extended the oxygen reduction reaction (ORR) activity from alkaline to acidic conditions. CPF-Fe@NG demonstrated outstanding performance with a half-wave potential of 853â mV (vs. RHE) and good stability after 10000â cycles in 1â M HClO4 . The pyrolysis-free route could also be used to assemble fuel cells, with a maximum power density of 126â mW cm-2 . Our findings offer new insights into the ORR process to optimize catalysts for both mechanistic studies and practical applications.
RESUMEN
Atomically precise o-carboranealkynyl-protected clusters [Ag14(C4B10H11)12(CH3CN)2]·2NO3 (CBA-Ag) and [Cu6Ag8(C4B10H11)12Cl]NO3 (CBA-CuAg) have been found to exhibit hypergolic activity, such that they are capable of spontaneous ignition and combustion upon contact with the white fuming nitric acid oxidizer. In particular, CBA-CuAg has a short ignition delay time of 15 ms, whereas the o-carboranealkynyl ligand is hypergolically inert. Systematic investigation revealed that the metal cluster core catalyzed the hypergolic behavior of inert o-carboranealkynyl ligand, and Cu doping further accelerated combustion catalysis. This work provides a new prospective in the rational design of novel metal cluster-based hypergolic fuels for propellant application.