Hollow Cluster Research Articles

Application of encapsulated hollow gold nanocluster targets for high-quality and quasi-monoenergetic ions generation

With persistent progress in ultra-intense laser pulses, Coulomb explosions (CE) of spherical nanoclusters can in principle produce high-quality quasi-monoenergetic ions. Focusing on using CE framework, in this paper, I have proposed a target scheme to accelerate the light/heavy ion beams. The scheme relies on encapsulating a hollow gold nanocluster inside a hollow proton-carbon (HC) nanosphere. The ability of this suggestion has been simulated by the two-dimensional particle-in-cell code (EPOCH). Simulation results exhibit that a hollow gold cluster can positively increase the electron extraction. This condition may improve the acceleration of low-divergence H+, C6+, and Au67+ ions. The simulation shows that at the end of the interaction, for a gold cluster with an optimal hollow radius of 91.3 nm, the cut-off energy of H+, C6+, and Au67+ are about 54.9, 51.5, and 54.9 MeV u−1, respectively. In this case, an increase of about 52% for H+ and 61% for C6+ is obtained, contrast to bare HC hollow nanosphere (i.e. a hollow nanosphere with no cluster), while the relative divergence decreases to 1.38 and 1.86, respectively, for H+ and C6+ ions. I have also compared my simulation results with another proposed target structure composed of a void area with an optimum diameter of 70.4 nm between the fully-gold nanocluster and HC nanosphere. I have exhibited that the results are improved, contrast to bare nanosphere. However, the cut-off energy suppression and angular divergence increase are shown compared with encapsulated hollow gold nanocluster structure.

The thermoeletric performance of nanoporous SnSe assembled by hollow cage cluster

The n-type and p-type thermoelectric property of nanoporous SnSe assembled by hollow cage cluster is studied by First-principles calculations and Boltzmann transport theory. The nanoporous SnSe presents low Shear modulus (3.16 GPa), low Shear sound velocity (925 m/s), low average sound velocity (1203 m/s), low Debye temperature (101 K) and large Gruneisen parameter (3.3), which implies that weak Sn-Se atomic interactions and strong anharmonicity of the bonding arrangement. Owing to the cubic structure of nanoporous SnSe, the thermoelectric property along different direction is isotropous. For n type, the optimal ZT at 800 K is 2.25, while the highest ZT of p type is 1.81. The strong differences between n type and p type are mainly dominated by the Seebeck coefficient, which is related to the carrier effective mass. This work not only demonstrates the excellent property of nanoporous SnSe, but also provides insights to understand the transport performance of cage structure.

Preparation and excellent adsorption of water pollution dyes over magnetic Fe3O4/C nanoparticles with hollow grape cluster morphology

Magnetic Fe3O4/C nanoparticles with hollow grape cluster morphology were synthesized through hydrothermal method, using SBA-15 as the hard template, glucose as the carbon source, and ferric chloride hexahydrate as the iron source. As-synthesized magnetic nanomaterials were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms, vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Meanwhile, the adsorption of organic dyes in water by magnetic nanoparticles was further studied. Results indicated that these magnetic nanomaterials exhibited hollow spherical structure similar to a bunch of grapes, and that magnetite Fe3O4 particles were embedded in the matrix of carbon nanoscale. The specific surface area, pore volume, pore diameter, and saturation magnetization of prepared samples were 522.7 m2/g, 0.4454 cm3/g, 3.5 nm, and 31.9 emu/g, respectively. At the same time, as-synthesized materials presented excellent adsorption properties and reutilization, so the total adsorption capacities for methyl orange, methylene blue, and rhodamine B were as high as 400 mg/g, 600 mg/g, and 150 mg/g under the natural pH of solution, respectively. Therefore, it is anticipated that these hollow magnetic Fe3O4/C nanoparticles will have potential industrial application prospects in environment water purification.

A mulberry-like hollow carbon cluster decorated by Al-doped ZnO particles for advanced lithium-sulfur cathode

To improve the electrochemical performances of lithium-sulfur (Li-S) batteries and extend their cycle life, a mulberry-like Al-doped ZnO (AZO) particles decorating carbon cluster composite (C@AZO cluster) is synthesized as the Li-S cathode material. The C@AZO/S composite, with the sulfur content of 70 wt% and the sulfur mass loading of 2.2 mg cm−2, delivers a high initial specific capacity of 974.2 mAh g−1 at the current density of 0.5C (1C = 1675 mAh g−1) and a low capacity decay of 0.12% per cycle over 300 cycles. In this composite, the interconnected primary carbon spheres decorated by conductive AZO particles provide a fast charge transmission network which could greatly enhance the reaction kinetics and rate performance of Li-S batteries. Meanwhile, the integrated architecture of carbon cluster and the polarity brought by AZO could effectively reduce the dissolution of polysulfides to improve the cycle stability.

Catalyzed assembly of hollow silver-sulfide cluster through self-releasable anion template

Hollow nanoclusters are intriguing for bridging the gap between small metal-organic cages and hollow nanoparticles and provide enormous opportunities for functional materials. Rational construction of hollow nanoclusters remains a challenge owing to the poor understanding of their formation pathways and difficulties in obtaining the intermediate structures. Here we report a catalyzed assembly strategy to construct hollow silver–sulfide clusters using a self-releasable carbonate template. The hollow Ag56 cluster and the carbonate-templated Ag33 intermediate are characterized by single-crystal X-ray analysis. Combining this data with a time-dependent UV-Vis spectroscopic investigation, we reveal the catalyst-like behavior of the self-releasable carbonate template and propose the corresponding mechanism. The assembly of hollow clusters using a self-releasable template may provide insight into understanding the formation mechanisms of other hollow nanoclusters and facilitate the design and construction of new hollow nanoclusters.

Au11Re: A hollow or endohedral binary cluster?

In this letter, we discussed the plausible formation of [Au11Re] as a superatom with an electronic structure accounted by the 1S21P61D10 shell order, denoting similar stability to [W@Au12]. The possible hollow or endohedral structures show a variable HOMO-LUMO gap according to the given structure (from 0.33 to 1.30 eV, at the PBE/ZORA level). Our results show that the energy minimum is an endohedral arrangement, where Re is encapsulated in a D3h-Au11 cage, retaining a higher gold-dopant stoichiometric ratio. This approach is useful for further rationalization and design of novel superatoms expanding the libraries of endohedral clusters.

Ag44(SeR)30: A Hollow Cage Silver Cluster with Selenolate Protection.

Selenolate protected, stable and atomically precise, hollow silver cluster was synthesized using solid state as well as solution state routes. The optical absorption spectrum shows multiple and sharp features similar to the thiolated Ag44 cluster, Ag44(SR)30 whose experimental structure was reported recently. High-resolution electrospray ionization mass spectrometry (HRESI MS) shows well-defined molecular ion features with two, three, and four ions with isotopic resolution, due to Ag44(SePh)30. Additional characterization with diverse tools confirmed the composition. The closed-shell 18 electron superatom electronic structure, analogous to Ag44(SR)30 stabilizes the dodecahedral cage with a large HOMO-LUMO gap of 0.71 eV. The time-dependent density functional theory (TDDFT) prediction of the optical absorption spectrum, assuming the Ag44(SR)30 structure, matches the experimental data, confirming the structure.

Development Pattern Recognition Model for the Classification of Circuit Probe Wafer Maps on Semiconductors

Spatial defect patterns generated during integrated circuit (IC) manufacturing contain valuable information on the fabrication process and can help engineers identify the root causes of any defect. Classification of these defect patterns is crucial to improving reliability and yield during IC manufacturing. Accurate classification requires good feature selection in order to assist in identifying the defect cluster types. In this paper, we demonstrate that the linear Hough transformation, the circular Hough transformation incorporating the cover ratio approach, and the zone ratio approach, when used as feature-extraction techniques, are able to distinguish lines, various solid circle-like cluster patterns such as blobs and bull's-eyes, and various hollow circle-like cluster patterns such as rings and edges. On the basis of these features, in this paper we provide a comprehensive evaluation of several data-mining classification approaches in terms of performance and accuracy. The results obtained using both artificial and real manufacturing data demonstrate the potential of this approach for analyzing general defect patterns that are generated during the IC fabrication process.

From Platonic Templates to Archimedean Solids: Successive Construction of Nanoscopic {V16As8}, {V16As10}, {V20As8}, and {V24As8} Polyoxovanadate Cages

Supramolecular coordination cages provide unique restricted inner cavities that can be exploited for molecular recognition purposes and catalysis. Their syntheses often involve complex self-organization processes and rely on the identification of preorganized, kinetically stable building units that provide ligand-accessible coordination sites. Here we report a highly effective protocol for the successive buildup of symmetrical nanoscopic polyoxometalate (POM) cages. Our methodology takes advantage of a supramolecular templating effect and utilizes the structure-directing influence of octahedral {X(x)(H(2)O)(6-x)} (X = Br(-), Cl(-); x = 2, 4, 6) assemblies that reside inside the hollow cluster shells and determine the arrangement of di- and tetranuclear vanadate units. The approach allows the preparation of a series of high-nuclearity POM cages that are characterized by {V(16)As(8)}, {V(16)As(10)}, {V(20)As(8)}, and {V(24)As(8)} core structures. In the latter cluster cage, the vanadium centers adopt a truncated octahedral topology. The formation of this Archimedean body is the direct result of the assembly of six square {V(4)O(8)} units that cap the vertices of the encapsulated Platonic {Cl(6)} octahedron. To the best of our knowledge, this {V(24)As(8)} cage is the largest hybrid vanadate cluster reported to date.

Stability of metallic hollow cluster systems

The results of calculations of electron structure for cluster systems with a spherical hole are presented. The calculations are performed within the jellium model using the Hartree–Fock and local density approximations for the electronic subsystem. It has been found that the total energy of the cluster has two minima as a function of the radius of the hole.

Stability of metallic hollow cluster systems: Jellium model approach

It is discussed that the quantum stability of a metallic cluster system with respect to the variation in the cluster shape transforms a spherical volume distribution of ionic charge core of the cluster into a spherical hollow configuration. Calculations are performed within the jellium model approach based on the Hartree-Fock theory and also within the local-density approximation. It is demonstrated that for such spherical cluster systems, there are two stable states characterized by the different distribution of the positive charge of the ionic core. One of the states corresponds to a spherical charge distribution of the ionic core uniform over the entire cluster volume. The second fullerenelike stable state arises when positive charge is uniformly distributed over a spherical shell of a certain width.

Density functional theory study of Al23, Al26 and Al92 clusters

In this paper we present results of the structural, energetic and electronic properties of Aln (n = 23, 26, 92) clusters calculated using density functional theory (DFT). Our main focus is the highly symmetric and energetically stable hollow Al92 cluster. This cluster appears as a natural extension of the smaller clusters, Al23 and Al26, that manifest similar structural motifs of pentagonal and hexagonal pyramids. The Al92 cluster maintains Ih symmetry and its central framework is similar to the structure of the well-known C60 fullerene and the recently reported B80 cluster. It has an additional Al atom below each hexagon centre and another one above each pentagon plane. To the best of our knowledge Al92 is the largest Al hollow cluster studied so far.

Synthesis and characterization of a mixed-valence hexadecavanadate cluster with half-open framework

A new mixed-valence hexadecavanadate cluster compound, (Me2NH2)4[H6V16O42(SO4)]·8H2O (1), has been synthesized via an efficient method in organic media. The hollow cluster shell of 1, with a sulfate ion locating in its centre, exhibits four large eight-membered –O–V–O–V– rings on its surface, which makes the cluster into a half-open structure distinguished from the common hollow clusters built up with closed surfaces. The intense blue luminescence of 1 in solution state is scarcely reported for the polyoxometalate clusters.

Exploring the Stability of Golden Fullerenes

The golden fullerenes Au32, Au50, and Au72 are reinvestigated, using high-level relativistic density functional theory (DFT). Their stability is found to be highly dependent on the electron count fulfilling the criterion of spherical aromaticity, which in turn is sensitive to relativity. Only neutral and cationic Au32 are shown to be stable with respect to alternative, space-filling isomers. Endohedrally doping Au32 with an alkali metal cation significantly increases its thermal stability, facilitating experimental preparation of the hollow cluster.

Magnetic Endohedral Transition‐Metal‐Doped Semiconduncting‐Nanoclusters

Endohedral first-row transition-metal-doped TM@Zn(i)S(i) nanoclusters, in which TM stands for the first-row transition-metals from Sc to Zn, and i=12, 16, have been characterized. In these structures the dopant metals are trapped inside spheroidal hollow semiconducting nanoclusters. It is observed that some of the transition metals are trapped in the center of mass of the cluster, whereas others are found to be displaced from that center, leading to structures in which the transition metals display a complex dynamical behavior upon encapsulation. This fact was confirmed by quantum molecular dynamics calculations, which further confirmed the thermal stability of endohedral compounds. In the endohedrally-doped nanoclusters in which the transition-metal atom sits on the center of mass, the host hollow cluster structure remains undistorted after dopant encapsulation. Conversely, if the encapsulated transition-metal atom is displaced from the center of mass, the host hollow cluster structure suffers a very tiny distortion. Additionally, it is found that there is negligible charge transfer between the dopant transition-metal atom and its hollow cluster host and, after encapsulation, the spin densities remain localized on the transition-metal atom. This allows for the atomic-like behavior of the trapped transition-metal atom, which gives rise to their atomic-like magnetic properties. The encapsulation free energies are negative, suggesting that these compounds are thermodynamically stable.

Spherical electron-ion systems in semiclassical approximation: Atoms and atomic clusters

A semiclassical method for calculating the total energy and spatial distribution of electron density in spherically symmetric electron-ion systems is applied to atoms and both solid and hollow atomic clusters. Both exchange-correlation interaction and second-order gradient correction are taken into account. The contribution due to the fourth-order gradient correction is discussed. An expression is proposed for the oscillating correction to the averaged electron density. An expression is obtained for the equilibrium radius of a hollow cluster. The dependence of the equilibrium radius of an endohedral cluster on the valence of the central atom is analyzed.

Optimized structures of Si28 and Ba@Si28 clusters: Ab initio study

AbstractFirst‐principle electronic structure calculations are carried out for the Si28 and endohedral Ba@Si28 clusters, which are components of the clusters in the silicon clathrate II. We obtain the structurally optimized cage structures of the clusters and the exohedral binding nature of Si atom on the Ba@Si28 clusters. The hollow Si28 cluster relaxes into the Si24‐like cluster in the clathrate I, having four exohedral Si atoms outside the hexagon. The hexagons on the Ba@Si28 cluster deforms into chair‐type with relaxation. The exohedral Si atom is the most stable at the edge center near the top that forms three pentagons. We propose a mechanism of the growth of the clathrates. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003

Exohedral Bonding Nature of Si Atom on the Ba@Si<SUB>28</SUB> Cluster; <I>Ab Initio</I> Study

First-principle electronic structure is studied for the Si 28 and Ba@Si 28 clusters, which are components of the clusters in silicon clathrate II. We obtain the geometrically optimized relaxed cage structures of the clusters and the exohedral binding nature of single Si atom on the Ba@Si 28 clusters. The hollow Sits cluster relaxes into the Si 24 like cluster in the clathrate I having four exohedral Si atoms outside the hexagon in the Si 24 cluster. The hexagons on the Ba@Si 28 cluster are deformed into a chair type with relaxation. The exohedral Si atom is the most stable at the edge center near the top that meets three pentagons. We have found for the first time that the exohedral Si atom forms the three-center covalent bond between the two caged Si atoms.

Synthesis of polyoxovanadates via “chimie douce”

A large variety of new polyoxovanadates have been synthesized during the past few years by sol–gel chemistry or hydrothermal methods. These wet chemistry methods offer many advantages compared to the usual solid state syntheses. New open structures have been obtained from aqueous precursors. They result from the self-assembling of ionic species in the solution. Vanadium oxide gels and sols, V 2O 5· nH 2O, are formed around the point of zero charge (pH≈2). They have a ribbon-like structure and exhibit a liquid crystal behavior. These mesophases are similar to those currently observed with nematic polymers. Xerogel layers deposited from V 2O 5· nH 2O gels exhibit some preferred orientation and behave as versatile host structures for intercalation giving new hybrid organic–inorganic nanocomposites. Layered structures are formed around pH≈7 in the presence of large organic cations. They are built of mixed valence polyoxovanadate planes made of [VO 5] pyramids and [VO 4] tetrahedra. Organic cations lie between the oxide layers where they interact with the negative oxygen of the VO double bonds. Anions can behave as templating agents. Hollow cluster shells are formed around anions that remain encapsulated within the negatively charged polyvanadate cage. Large cations only behave as counter ions for the formation of a neutral crystalline network. It appears that the molecular structure of V V precursors depends mainly on pH, but the way they self-assemble may be governed by other ionic species in the solution.

Dielectric model for giant fullerenes

The ultraviolet polarizability of spherical and cylindrical multishell fullerenes is considered in a continuum macroscopic dielectric framework and within a discrete dipole approximation. We studied the position and the shape variation of the collective π-plasmon excitation as a function of the shape of the hollow cluster. The results are compared with available experimental data.