Recent Progress in Inorganic Anions Templated Silver Nanoclusters: Synthesis, Structures and Properties

Polyoxometalate-mediated syntheses of three structurally new silver clusters

Three structurally new polyoxometalate-templated silver clusters, homometallic [(SiW9O34)@Ag24(iPrS)11(DPPP)6Cl]2(SiW12O40) (Ag24), heterometallic [(SiW9O34)@Ag22Cu(iPrS)11(DPPP)6Cl](SbF6)2 (Ag22Cu) and {Ag16(iPrS)6(DPPP)8(CH3COO)4[Co4(OH)3(H2O)SiW9O33]2}·(CH3CN)4 (Ag16Co8) (iPrS- = isopropanethiolate, DPPP = 1,3-bis(diphenylphosphino)propane, SbF6- = hexafluoroantimonate) have been successfully synthesized using a facile solvothermal approach. The introduction of copper and cobalt ions can induce obvious changes in the molecular configuration of the obtained clusters, leading to distinct temperature-dependent photoluminescence and photothermal conversion properties.

A 66-Nuclear All-Alkynyl Protected Peanut-Shaped Silver(I)/Copper(I) Heterometallic Nanocluster: Intermediate in Copper-Catalyzed Alkyne-Azide Cycloaddition

Ligand-protected heterometallic nanoclusters in contrast to homo-metal counterparts show more broad applications due to the synergistic effect of hetero-metals but their controllable syntheses remain a challenge. Among heterometallic nanoclusters, monovalent Ag-Cu compounds are rarely explored due to much difference of Ag(I) and Cu(I) such as atom radius, coordination habits, and redox potential. Encouraged by copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction, comproportionation reaction of Cu(II)X2 and Cu(0) in the presence of (PhC≡CAg)n complex and molybdate generated a core-shell peanut-shaped 66-nuclear Ag(I)-Cu(I) heterometallic nanocluster, [(Mo4O16)2@Cu12Ag54(PhC≡C)50] (referred to as Ag54Cu12). The structure and composition of Ag-Cu heterometallic nanocluster are fully characterized. X-ray single crystal diffraction reveals that Ag54Cu12 has a peanut-shaped silver(I)/copper(I) heterometallic nanocage protected by fifty phenylacetylene ligands in µ3-modes and encapsulated two mutually twisted tetramolybdates. Heterometallic nanocage contains a 54-Ag-atom outer ellipsoid silver cage decorated by 12 copper inside wall. Nanosized Ag54Cu12 is a n-type narrow-band-gap semiconductor with a good photocurrent response. Preliminary experiments demonstrates that Ag54Cu12 itself and activated carbon supported Ag54Cu12/C are effective catalysts for 1,3-dipole cycloaddition between alkynes and azides at ambient conditions. The work provides not only a new synthetic route toward Ag(I)-Cu(I) nanoclusters but also an important heterometallic intermediate in CuAAC catalytic reaction.

Silver Cluster Assembled Materials: A Model-Driven Perspective on Recent Progress, with a Spotlight on Ag12 Cluster Assembly

The exploration of individual nanoclusters is rapidly advancing, despite stability concerns. To address this challenge, the assembly of cluster nodes through linker molecules has been successfully implemented. However, the linking of the cluster nodes itself introduces a multitude of possibilities, especially when additional factors come into play. While this method proves effective in enhancing material stability, the specific reasons behind its success remain elusive. In our laboratory, we have undertaken extensive studies on Ag cluster-assembled materials. So, here our goal is to establish a model system that allows for the discernment of various factors, eliminating unnecessary complexities during the linking approach. So, we hope that the systematic discourse presented in here will contribute significantly to future endeavors, helping to set clear priorities, and provide solutions to concerns that arise when working with a model system.

Low-Triggering-Potential and Narrow-Potential-Window Electrochemiluminescence of Silver Nanoclusters for Gene Assay

A low-triggering potential and a narrow-potential window are anticipated to decrease the electrochemical interference and cross talk of electrochemiluminescence (ECL). Herein, by exploiting the low oxidative potential (0.82 V vs Ag/AgCl) of dihydrolipoic acid-capped sliver nanoclusters (DHLA-AgNCs), a coreactant ECL system of DHLA-AgNCs/hydrazine (N2H4) is proposed to achieve efficient and oxidative-reduction ECL with a low-triggering potential of 0.82 V (vs Ag/AgCl) and a narrow-potential window of 0.22 V. The low-triggering-potential and narrow-potential-window nature of ECL can be primarily preserved upon labeling DHLA-AgNCs to probe DNA and immobilizing DHLA-AgNCs onto the Au surface via sandwiched hybridization, which eventually enables a selective ECL strategy for the gene assay at +0.82 V. This gene assay strategy can sensitively determine the gene of human papillomavirus from 10 to 1000 pM with a low limit of detection of 5 pM (S/N = 3) and would open a way to improve the applied ECL bioassay.

Heterometallic AuI 6 AgI 6 Macrocyclic Cluster Templated by a Supramolecular Melamine Dimer

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ6 -(C3 N6 H3 )3- ]2 -AuI 6 AgI 6 . X-ray single crystal structural analysis showed that a crown-like AuI 6 AgI 6 macrocycle is aligned around two parallelly stacked μ6 -(C3 N6 H3 )3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ6 -(C3 N6 H3 )3- ]2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters.

Three in One: Three Different Molybdates Trapped in a Thiacalix[4]arene Protected Ag72 Nanocluster for Structural Transformation and Photothermal Conversion

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO4 2- , Mo6 O22 8- and Mo7 O25 8- ) in situ transformed from classic Lindqvist Mo6 O19 2- , providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post-reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post-synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom-precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown.

Metal Nanoclusters as a Superior Polysulfides Immobilizer toward Highly Stable Lithium-Sulfur Batteries

Due to their high designability, unique geometric and electronic structures, and surface coordination chemistry, atomically precise metal nanoclusters are an emerging class of functional nanomaterials at the forefront of materials research. However, the current research on metal nanoclusters is mainly fundamental, and their practical applications are still uncharted. The surface binding properties and redox activity of Au24 Pt(PET)18 (PET: phenylethanethiolate, SCH2 CH2 Ph) nanoclusters are herein harnessed as an high-efficiency electrocatalyst for the anchoring and rapid conversion of lithium polysulfides in lithium-sulfur batteries (LSBs). Au24 Pt(PET)18 @G composites are prepared by using the large specific surface area, high porosity, and conductive network of graphene (G) for the construction of battery separator that can inhibit polysulfide shuttle and accelerate electrochemical kinetics. Resultantly, the LSB using a Au24 Pt(PET)18 @G-based separator presents a high reversible specific capacity of 1535.4 mA h g-1 for the first cycle at 0.2 A g-1 and a rate capability of 887 mA h g-1 at 5 A g-1 . After 1000 cycles at 5 A g-1 , the capacity is 558.5 mA h g-1 . This study is a significant step toward the application of metal nanoclusters as optimal electrocatalysts for LSBs and other sustainable energy storage systems.

Anion-templated silver nanoclusters: precise synthesis and geometric structure

Metal nanoclusters (NCs) are gaining much attention in nanoscale materials research because they exhibit size-specific physicochemical properties that are not observed in the corresponding bulk metals. Among them, silver (Ag) NCs can be precisely synthesized not only as pure Ag NCs but also as anion-templated Ag NCs. For anion-templated Ag NCs, we can expect the following capabilities: 1) size and shape control by regulating the central anion (anion template); 2) stabilization by adjusting the charge interaction between the central anion and surrounding Ag atoms; and 3) functionalization by selecting the type of central anion. In this review, we summarize the synthesis methods and influences of the central anion on the geometric structure of anion-templated Ag NCs, which include halide ions, chalcogenide ions, oxoanions, polyoxometalate, or hydride/deuteride as the central anion. This summary provides a reference for the current state of anion-templated Ag NCs, which may promote the development of anion-templated Ag NCs with novel geometric structures and physicochemical properties.

Recent progress in dichalcophosphate coinage metal clusters and superatoms

Atomically precise clusters of group 11 metals (Cu, Ag, and Au) attract considerable attention owing to their remarkable structure and fascinating properties. One of the unique subclasses of these clusters is based on dichalcophosphate ligands of [(RO)₂PE₂]^- type (E = S or Se, and R = alkyl). These ligands successfully stabilise the most diverse Cu, Ag, and Au clusters and superatoms, spanning from simple ones to amazing assemblies featuring unusual structural and bonding patterns. It is noteworthy that such complicated clusters are assembled directly from cheap and simple reagents, metal(I) salts and dichalcophosphate anions. This reaction, when performed in the presence of a hydride or other anion sources, or foreign metal ions, results in hydrido- or anion-templated homo- or heteronuclear structures. In this feature article, we survey the recent advances in this exciting field, highlighting the powerful synthetic capabilities of the system "a metal(I) salt - [(RO)₂PX₂]^- ligands - a templating anion or borohydride" as an inexhaustible platform for the creation of new atomically precise clusters, superatoms, and nanoalloys.

Solvent-Mediated Separation and Reversible Transformation of 1D Supramolecular Polymorphs Built from [W10O32]4- Templated 48-Nuclei Silver(I) Cluster

Although the C-H···O interaction is an essential component in determining the molecular packing in solids and the properties in supramolecular chemistry, it presents a significant challenge when trying to use it in the crystal engineering of complex metallosupramolecules, even though it is a relatively weak supramolecular force. The first pair of high-nuclearity silver-cluster-based one-dimensional (1D) polymorphs built from supramolecular synthon [W₁₀O₃₂@Ag₄₈(CyS)₂₄(NO₃)₁₆]·4NO₃ (Cy = cyclohexyl) bridged by four grouped inorganic NO₃^- ligands is initially synthesized as a mixed phase and further individually crystallized as a pure phase by virtue of tuning intermolecular C-H···O interaction through altering the composition ratio of ternary solvent system. Increasing highly polar and hydrogen-bonding methanol strengthens the solvation effect reflected by the change of coordination orientation of surface NO₃^- ligands, which dominates the packing of the 1D chains in the crystal lattice, resulting in the crystallization of polymorphs from tetragonal to monoclinic. The two crystalline forms can also be reversibly transformed to each other in an appropriate solvent system. Correspondingly, the two polymorphs display distinct temperature-dependent photoluminescence behaviors, which are ascribed to the variation of noncovalent interchain C-H···O interactions along with the temperature. More importantly, benefiting from the suppression of fluorescence, both polymorphs offer excellent photothermal conversion properties which were further applied to remote-controlled laser ignition. These findings may open more avenues for the application of solvent-mediated intermolecular interaction in controlling the molecule arrangement as well as the optical properties.

The first polyoxoniobate-templated silver cluster with temperature-dependent luminescent emission

The compound [(Nb₆O₁₉)@Ag₃₄(^tBuCC)₂₄(CH₃COO)₂] (Ag₃₄) was synthesized using the solvothermal method combined with volatilization. This was the first case, to the best of our knowledge, of isolating a silver cluster containing a polyoxoniobate (PONb) template. The luminescence, solution behavior and solid-state stability of Ag₃₄ were studied in detail. Electrospray ionization mass spectrometry indicated that Ag₃₄ can maintain the integrity of its skeleton in solution. Detection of temperature could be a potential application of its unique luminescent behavior. We expect this work to inspire further fabrications of PONb-templated high-nuclearity silver clusters.

Regulating the assembly and expansion of the silver cluster from the Ag37 to Ag46 nanowheel driven by heteroanions

Precise control over the shape and size of metal nanoclusters through anion template-driven self-assembly is one of the key scientific goals in the nanocluster community, however, it is still not understood comprehensively. In this work, we report the controllable synthesis and atomically precise structures of silver nanowheels Ag37 and Ag46, using homo (Cl^- ions) and heteroanion (Cl^- and CrO₄ ^2- ions) template strategies, along with macrocyclic p-phenyl-thiacalix[4]arene and small ⁱPrS^- ligands. Structural analyses revealed that in Ag37, Cl^- ions serve as both local and global templates, whereas CrO₄ ^2- ions function as local and Cl^- ions as global templates in Ag46, resulting in a pentagonal nanowheel (Ag37) and a hexagonal (Ag46) nanowheel. The larger ionic size and more negative charges of CrO₄ ^2- ions than Cl^- ions offer more coordination sites for the silver atoms and are believed to be the key factors that drive the nanowheel core to expand significantly. Also, by taking advantage of the deep cavity of thiacalix[4]arene with an extended phenyl group, Ag46 has been used as a host material for dye adsorption depending on the charge and size of organic dyes. The successful use of heteroanions to control the expansion of well-defined silver nanowheels fills the knowledge gap in understanding the directing role of heteroanions in dictating the shape and size of nanoclusters at the atomic level.

Proton Affinity in the Chemistry of Beta-Octamolybdate: HPLC-ICP-AES, NMR and Structural Studies

The affinity of [β-Mo₈O₂₆]^4- toward different proton sources has been studied in various conditions. The proposed sites for proton coordination were highlighted with single crystal X-ray diffraction (SCXRD) analysis of (Bu₄N)₃[β-{Ag(py-NH₂)Mo₈O₂₆]}] (1) and from analysis of reported structures. Structural rearrangement of [β-Mo₈O₂₆]^4- as a direct response to protonation was studied in solution with ⁹⁵Mo NMR and HPLC-ICP-AES techniques. A new type of proton transfer reaction between (Bu₄N)₄[β-Mo₈O₂₆] and (Bu₄N)₄H₂[V₁₀O₂₈] in DMSO results in both polyoxometalates transformation into [V₂Mo₄O₁₉]^4-, which was confirmed by the ⁹⁵Mo, ⁵¹V NMR and HPLC-ICP-AES techniques. The same type of reaction with [H₄SiW₁₂O₄₀] in DMSO leads to metal redistribution with formation of [W₂Mo₄O₁₉]^2-.

Stabilization of {Ag20(StBu)10} and {Ag19(StBu)10} Toroidal Complexes in DMSO: HPLC-ICP-AES, PL, and Structural Studies

The presence of DMSO provides a unique ability to stabilize silver toroidal complexes in the direct reaction between AgStBu and AgNO3 at 80 °C. Slow cooling results in large crystals of [NO3@Ag19.2(StBu)10(DMSO)5.2(NO3)8.2]·3DMSO (1), which were isolated and characterized by single crystal X-ray diffraction (SCXRD) analysis. The crystal structure contains both {Ag20(StBu)10} and {Ag19(StBu)10} clusters. The solution of these material in DMSO was studied with HPLC techniques, which demonstrated the presence of both complexes in solution. The use of [SiW12O40]4– as counter anion gives crystals of a double complex salt [Ag17.8(NO3)3.8(StBu)10][SiW12O40]·30DMSO (2) under the same conditions. Temperature-dependent photoluminescence (PL) was studied.

Synthesis of Two Neutral Silver Alkynyl Nanoclusters by a Single Divalent Tetrahedral Anion Template and a Study of Their Optical Features

The synthesis of nanoclusters from simple structural units is usually a challenging process because of the complexity and unpredictability of the self-assembly process of these types of compounds. Herein, two new neutral 19-nuclearity silver nanoclusters based on alkynyl ligands with the formulas [(CrO₄)@Ag₁₉(C≡C^tBu)₈(Ph₂PO₂)₆(tfa)₃(CH₃OH)₂] (1) and [(SO₄)@Ag₁₉(C≡C^tBu)₈(Ph₂PO₂)₆(tfa)₃(CH₃OH)₂] (2), in which tfa = trifluoroacetate, were synthesized, and their structures were investigated by single-crystal and powder X-ray diffraction, electrospray ionization mass spectrometry, elemental analyses, and Fourier transform infrared spectroscopy. The surface ligands of Ph₂PO₂H and trifluoroacetate were assembled through hydrogen bonding, metal-aromatic interactions, and coordination bonding around 19 silver atoms as the metal skeletons of the nanoclusters. Sulfate and chromate anions, as a template within the metal skeleton of clusters through bonding with silver atoms, stabilized the structure. In addition, the UV-vis absorption spectroscopy, luminescence properties, and thermal stability of the nanoclusters were investigated.

Phosphate anion-induced silver-chalcogenide cluster-based metal organic frameworks as dual-functional catalysts for detoxifying chemical warfare agent simulants

Two porphyrinic silver-chalcogenide cluster-based MOFs were achieved using a phosphate anionic template strategy, and the highly photoactive organic building modules combined with Lewis acidic silver clusters allow both SCC-MOFs to be used as versatile catalysts for the simultaneous degradation of sulfur mustard and nerve agent simulants.

Oxocarbon Anions Templated in Silver Clusters

Three types of oxocarbon anions as templates were used to synthesize high-nuclear silver clusters, [Ag₁₆(C₂O₄){S₂P(OEt)₂}₁₂]₂(PF₆)₄ (1), [Ag₁₆(C₄O₄){S₂P(OEt)₂}₁₂]₂(PF₆)₄ (2), and [Ag₃₂(S)₂(C₅O₅)₂{S₂P(OEt)₂}₂₂](PF₆)₂ (3), and characterized by multi-NMR spectroscopy and X-ray crystallography. As the template size increases, the shape and size of the clusters change accordingly. The template effect in high-nuclear silver clusters has been investigated in this work.

Anion-Directed Regulation of Structures and Luminescence of Heterometallic Clusters

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Introducing ClO₄ ^- into orange-emissive, butterfly-like [(C)(Au-PPhpy₂ )₆ Ag₄ ](BF₄ )₆ (1, PPhpy₂ =bis(2-pyridyl)phenylphosphine) leads to the formation of red-emissive [(C)(Au-PPhpy₂ )₆ Ag₅ (ClO₄ )₃ ](ClO₄ )₄ (2) with a novel trigonal bipyramidal structure; employing PhCO₂ ^- gives yellow-emissive, hexagram-like [(C)(Au-PPhpy₂ )₆ Ag₆ (PhCO₂ )₃ ](BF₄ )₅ (3). Notably, 1 exhibits weak luminescence in CH₂ Cl₂ /CH₃ OH=1 : 1 (v : v) with a quantum yield (QY) of 0.05, whereas it was dramatically increased to 0.49 and 0.83 for 2 and 3, respectively. Theoretical calculation confirms that the involvement of anions in the electronic structures is responsible for the shifts of emission. The high QYs of 2 and 3 are attributed to the protection provided by ligands and anions. This work demonstrates that anions may serve as an extra designable factor beyond just counterions for functional metal clusters.

Macrocyclic Polyoxometalates: Selective Polyanion Binding and Ultrahigh Proton Conduction

The rational development of an anion templation strategy for the construction of macrocycles has been historically limited to small anions, but large polyoxoanions can offer unmatched structural diversity and ample binding sites. Here we report the formation of a {Mo₂₂ Fe₈ } macrocycle by using the Preyssler anion, [NaP₅ W₃₀ O₁₁₀ ]^14- ({P₅ W₃₀ }), as a supramolecular template. The {Mo₂₂ Fe₈ } macrocycle displays selective anion binding behavior in solution. In the solid state, the 1 : 2 host-guest complex, {P₅ W₃₀ }₂ ⊂{Mo₂₂ Fe₈ }, transports protons more effectively, through an extended hydrogen-bonding network, than a related 1 : 1 complex where the guest is completely encapsulated. The results highlight the great potential this anion templation approach has in producing macrocyclic systems for selective anion recognition and proton conduction purposes.

In situ insertion of copper to form heteroanionic D3h-symmetric [Cu3Mo8O32]10- for a templated Ag55 nanocluster

A polyoxometalate-templated thiolate-protected silver nanocluster, [Cu₃(Mo₄O₁₆)₂@Ag₅₅(CyhS)₄₃(CH₃O)(COOCF₃)]·3H₂O, has been isolated under solvothermal conditions. In situ insertion of three Cu²⁺ ions into two polymolybdate anions generated a new, sandwich-type D_3h-symmetric [Cu₃(Mo₄O₁₆)₂]^10- polyoxoanion template encapsulated into an Ag₅₅(CyhS)₄₃ shell. The structure and composition of this Ag nanocluster have been fully characterized. This work has provided a new way to develop high-nuclearity metal nanoclusters with various structures.

Trapping a [W10O32]6- decatungstate anion in an Ag44 nanowheel

Compound [Ag 44 (W 10 O 32 )(S t Bu) 24 (CF 3 COO) 8 ](CF 3 COO) 6 ·6H 2 O ( 1 ) was synthesized through the one-pot method, which is the first case of isolating a new silver thiolate cluster containing a [W 10 O 32 ] 6- template which transforms from WO 4 2- polyoxoanion through a self-assembly process. The anionic nature of the reduced [W 10 O 32 ] 6- template and the effective silver-oxygen interaction contribute to the formation of the Ag 44 nanowheel in 1 . The luminescence, photocatalytic activity and electrochemistry properties of 1 were studied.

Atomically Precise Silver Nanocluster for Artificial Light-Harvesting System Through Supramolecular Functionalization

Designing an artificial light-harvesting system (LHS) with high energy transfer efficiency has been a challenging task. Herein, we report an atom-precise silver nanocluster (Ag NC) as a unique platform to fabricate the artificial LHS. A facile one-pot synthesis of [Cl@Ag₁₆S(S-Adm)₈(CF₃COO)₅(DMF)₃(H₂O)₂]·DMF (Ag₁₆) NC by using a bulky adamantanethiolate ligand is portrayed here which, in turn, alleviates the issues related to the smaller NC core designed from a highly steric environment. The surface molecular motion of this NC extends the non-radiative relaxation rate which is strategically restricted by a recognition site-specific supramolecular adduct with β-cyclodextrin (β-CD) that results in the generation of a blue emission. This emission property is further controlled by the number of attached β-CD which eventually imposes more rigidity. The higher emission quantum yield and the larger emission lifetime relative to the lesser numbered β-CD conjugation signify Ag₁₆ ∩ β-CD₂ as a good LHS donor component. In the presence of an organic dye (β-carotene) as an energy acceptor, an LHS is fabricated here via the Förster resonance energy transfer pathway. The opposite charges on the surfaces and the matched electronic energy distribution result in a 93% energy transfer efficiency with a great antenna effect from the UV-to-visible region. Finally, the harvested energy is utilized successfully for efficient photocurrent generation with much-enhanced yields compared to the individual components. This fundamental investigation into highly-efficient energy transfer through atom-precise NC-based systems will inspire additional opportunities for designing new LHSs in the near future.

A β-cyclodextrin functionalized atomically precise Ag₁₆ based artificial light-harvesting system is fabricated with 93% energy transfer efficiency from the blue to the green emission region of the acceptor β-carotene molecule.

Recent advances in polyoxometalate-based metal-alkynyl clusters

This paper focuses on the recent advances in polyoxometalate-based metal-alkynyl clusters.

Self-assembly patterns of non-metalloid silver thiolates: structural, HR-ESI-MS and stability studies

Screening of AgNO₃/AgS^tBu solutions in DMF, DMSO and NMP resulted in the isolation of three novel nanosized silver/thiolate complexes with a torus-like {Ag₂₀(S^tBu)₁₀} core. The structures of [NO₃@Ag₂₀(S^tBu)₁₀(NO₃)₉(DMF)₆] (1) and [NO₃@Ag₂₀(^tBuS)₁₀(NO₃)₈(NMP)₈][NO₃@Ag₁₉(^tBuS)₁₀(NO₃)₈(NMP)₆]₂(NO₃) (2) were studied by single crystal X-ray diffraction (SCXRD). The self-assembly process leading to 1 can be switched to a different outcome using Br^-, resulting in [Br@Ag₁₆(S^tBu)₈(NO₃)₅(DMF)₃](NO₃)₂ (3), which is the one of the few genuine host-guest complexes in the silver/thiolate systems. Solutions of the individual complexes in CH₃CN were studied by HR-ESI-MS techniques, which revealed a dynamic behavior for each complex, driven by a redistribution of the {AgNO₃} units. This dynamics results in the appearance of both cationic and anionic species, based on unchanged silver-thiolate cores. Daylight causes degradation of 3 with the formation of a composite material based on defective orthorhombic Ag₂S with a porous morphology, as observed using the SEM technique. The electrocatalytic HER activity of such a material was studied.

Novel class of water-soluble phosphonate silver cluster assembled material for efficient photoelectric sensing and photoacoustic imaging

Owing to the atomic precession and exotic photophysical properties, silver cluster assembled materials (CAMs) have been explored for use as functional nanomaterials in recent years. Although a small number of thiolate protected silver CAMs have previously been investigated, the synthesis of thiol-free analogues and their solubility remain challenging. Here, the structure-property correlation of a newly synthesized one-dimensional phenyl phosphonate protected [Ag₂(PhPO₃H)₂(apy)₂], (in which, 4,4'-azopyridine = apy) CAM is demonstrated. The multifunctional surface protecting ligand is strategically attached to the core for the first time to tailor the solubility, structural stability and charge transfer mechanism. The small size of the cluster building blocks, along with the choice of organic linker molecules, efficiently stabilize the structure via intra-chain π-π stacking while inter-chains π-π interactions create a two-dimensional supramolecular architecture. The advantageous band structure associated with the charge transfer phenomenon and the high structural stability of the material are guided to explore the sustainable photoresponsive character of this CAM, resulting in the generation of an 82 nA photocurrent. Additionally, the unprecedented water solubility, which is very rare for this class of material, provides opportunities for use in biomedical imaging applications. The measured photoacoustic signal strength confirms the blood vessel mimicking capabilities of the portrayed material at a depth of approximately 3 mm inside chicken breast tissue.

Synthesis of highly stable fluorescent poly(methacrylic acid-co-itaconic)-protected silver nanoclusters and sensitive detection of Cu2

Stable fluorescent silver nanoclusters (AgNCs) were synthesized through one-step UV photoreduction using the multiple carboxyl copolymer poly(methacrylic acid-co-itaconic acid) P(MAA-co-IA) as a novel template. The fluorescence lifetime and the quantum yield of the obtained AgNCs were 1.84 ns and 8.9% in an aqueous solution, respectively. Owing to the multiple carboxyls of the protective P(MAA-co-IA) template, the obtained AgNCs have excellent advantages such as good dispersity, and high stability, which make them suitable for highly sensitive and selective detection of Cu²⁺ by fluorescence quenching. A good linear relationship exists between the degree of fluorescence quenching for silver nanoclusters and Cu²⁺ concentration ranging from 0 to 10 μM. The limit of detection (LOD) is 6.36 nM. The result implies that the as-synthesized AgNCs show great potential in the analysis field.

The avenue of fruit wastes to worth for synthesis of silver and gold nanoparticles and their antimicrobial application against foodborne pathogens: A review

The emerging fruit wastes valorization tactic is a strategy for minimizing the dependence on toxic solvents and chemicals commonly used in the preparation of nanoparticles (NPs). Furthermore, the NPs have exhibited promising antimicrobial applications against foodborne pathogens. Hence, a timely review of this topic is in demand to provide a clear insight into the subject. In this article, the synthesis of silver and gold NPs from fruit wastes and their antimicrobial application against foodborne pathogens are reviewed. The extraction method, mechanism of NPs formation and influences of various experimental parameters on the shape and size of the NPs are described. In the second part of the article, antimicrobial activities against foodborne pathogens regarding the nature, optimum composition, surface structure, synergism and morphology of the NPs are reviewed. Furthermore, challenges and future trends related to the synthesis and antimicrobial application of fruit wastes-mediated NPs are discussed.

Stable supercapacitor electrode based on two-dimensional high nucleus silver nano-clusters as a green energy source

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF₂) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g^-1 at 4.5 A g^-1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s^-1 to 1 V s^-1), meaning it could act as a green energy source.

Mass spectrometry guided surface modification of a tellurate ion templated 36-nucleus silver alkynyl nanocluster

Under the guidance of the ESI-MS result for [TeO6@Ag36(CCtBu)18(tfa)12] (1, tfa = trifluoroacetate), a new 36-nucleus silver-alkynyl cluster substituted by four pentafluorobenzoates, named as [TeO6@Ag36(CCtBu)18(tfa)8(F5PhCO2)4] (2), has been fabricated.

Solvatomorphs of (Bu4N)2[{Ag(N2-py)}2Mo8O26]: structure, colouration and phase transition

(Bu4N)2[β-{Ag(N2-py)}2Mo8O26] demonstrates monomer/polymer dualism and a colouration phenomenon. The polymeric phase reveals a Ag assisted phase transition. Such complexes can act as precursors for catalytically active materials.

A triflate and alkynyl protected Ag43 nanocluster with a passivated surface

A trifluoromethanesulfonate (OTf) and tert-butylacetylene (^tBuC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C⁻) co-protected silver nanocluster (NC), Ag₄₃(^tBuCC)₂₄(CF₃SO₃)₈ (Ag₄₃), was synthesized and characterized. Single crystal X-ray diffraction analysis revealed its total structure. 43 Ag atoms are arranged into a three-concentric-shell Ag@Ag₁₂@Ag₃₀ structure. Both OTf and ^tBuCC⁻ ligands bonded with Ag atoms in a μ₃ mode. The application of Ag₄₃ as a catalyst for the reaction of silane with alcohol or H₂O indicated that the surface ligands had a profound passivation effect, which significantly influenced the reactivity and selectivity.

A trifluoromethanesulfonate (OTf) and tert-butylacetylene (^tBuC≡C⁻) co-protected silver nanocluster (NC), Ag₄₃(^tBuC≡C)₂₄(CF₃SO₃)₈ (Ag₄₃) was synthesized and characterized. Its surface ligands have shown strong passivation effect in the reaction catalyzed by Ag₄₃.

New protective ligands for atomically precise silver nanoclusters

Atomically precise silver nanoclusters (NCs) have emerged as a hot topic attracting immense research interest. Protecting ligands are needed for direct capping on cluster surfaces in order to prevent aggregation and to stabilize NCs. It has been demonstrated that protective ligands are critical to determining the sizes, structures and properties of silver NCs. The past decades have witnessed conventionally used organic ligands (thiolates/selenols, phosphines and alkynyls) and inorganic ligands (chalcogens and halogens) being extensively used to passivate NC surfaces. However, only in the most recent years have new-type protecting ligands beyond the conventional ones begun to be introduced in the protecting sphere of new functional silver NCs. The present Frontier article covers the most recent examples of some new protective agents for well-defined silver NCs. We describe four classes of novel silver NCs stabilized by newly-developed surface ligands, namely, nitrogen-donor organic ligands, oxygen-donor inorganic ligands, metalloligands and macrocyclic hosts, paying attention to the synthesis, structures and properties of these silver NCs. This Frontier article will hopefully attract more cluster scientists to explore more freshly ligated atomically precise silver NCs with novel structures and properties in the years ahead. The literature survey in this review is based on publications up to February 2020. Some suggestions for future directions in this field are also given.