Nanocluster Precursors Research Articles

Ultrafine Pt-based catalyst decorated with oxygenophilic Ni-sites accelerating alkaline H2O dissociation for efficient hydrogen evolution

Although Pt is a widely adopted commercial catalyst for the hydrogen evolution reaction (HER), its practical application is greatly limited by its prohibitive cost and high energy barrier for H2O dissociation in alkaline media. Herein, an ultrafine Pt-based catalyst decorated with oxygenophilic Ni-sites is rationally designed and successfully synthesized with Pt5(GS)10 (HGS = l-reduced glutathione) nanocluster precursor. The optimized Ni-decorated Pt catalyst (Ni-Pt-C-500) with ultrafine nanoparticles (about 1.6 nm) exhibits a low overpotential (14.0 mV) at 10 mA cm−2 and a mild Tafel slope of 20.8 mV dec−1 in the HER, which is superior to its undecorated counterpart (Pt-C-500), the commercial 20 wt% Pt/C catalyst and most of the previously reported Pt-based electrocatalysts. Experimental observations and theoretical calculations indicate that H2O could be spontaneously adsorbed to Ni-sites of the Ni-Pt-C-500 catalyst. Mechanistic studies reveal that Ni-sites promote HER by accelerating the kinetic of H2O cleavage and optimizing the electronic structure of Pt. This work paves a new avenue for designing other ultrafine hybrid electrocatalysts based on metal nanoclusters to enhance catalytic reaction kinetics.

Single-Atom-Kernelled Nanocluster Catalyst.

To propose the concept of single-atom-kernelled nanocluster, we synthesized a Pd-based trimetal nanocluster with a single-Ag atom-kernel for the first time by introducing some steric hindrance factors and employing a joint alloying strategy that combines the coreduction with an antigalvanic reduction (AGR). Although the AGR-derived Pd-based trimetal nanoclusters with single-silver atom kernels have low contents of gold, they show higher activity and selectivity than those of the bimetal precursor nanocluster in the electrocatalytical reduction of CO2 to CO. Furthermore, it is revealed that the kernel single atoms from both Au4Pd6(TBBT)12 and Au3AgPd6(TBBT)12 are not the active sites for catalysis, but greatly influence the catalytical performance by effecting the electronic configuration. Thus, it is demonstrated that the single-atom-kernelled nanocluster can not only improve the precious metal utilization (even to 100%) but also better the properties and provide insight into the structure-property correlation for metal nanoclusters.

Cluster Self-Organization of Intermetallic Systems: New Four-Layer Cluster Precursor K244 = 0@12@20@80@132 and New Three-Layer Cluster Precursor K245 = 1@14@48@206 in the Rh140Al403-cP549 and Mn18Pd138Al387-cP549 Crystal Structures

The geometric and topological analysis of the crystal structure of (i) the Rh140Al403-cP549 intermetallide with cubic cell parameters a = 19.9350 A, V = 7922.25 A3, and the Pm-3 space group and (ii) the Mn18Pd138Al387-cP549 intermetallide with cubic cell parameters a = 20.211 A and Pm-3 space group is conducted by the ToposPro program package. Two new cluster precursors with the symmetry -43m is established: the K244 = 0@12@20@80@132 four-layer cluster with an inner icosahedron Pd12 or Rh12 and the three-layer cluster K245 = 1@14@48@206 with an inner 15-atom polyhedron Al@Pd8Al6 or Al@Rh8Al6. The symmetric and topological code of self-assembly processes of 3D structures from K244 and K245 nanocluster precursors is reconstructed in the following form: primary chain → microlayer → microframework. MAl3 and M2Al2 (M = Rh or Pd) clusters bound by Al atoms were adjusted as spacers occupying voids in the 3D framework of the K242 and K245 nanoclusters.

Cluster Self-Organization of Intermetallic Systems: New Two-Layer Nanocluster Precursors K64 = 0@8(Sn4Ba4)@56(Na4Sn52) and K47 = Na@Sn16@Na30 in the Crystal Structure of Na52Ba4Sn80 -cF540

Using computer methods (ToposPro software package), geometrical and topological analysis of the crystal structure of Na52Ba4Sn80-cF540 intermetallic compound (a = 25.053 A, V = 16 010.82 A3, space group F-43m) are carried out. Two new nanocluster precursors with the -43m symmetry are determined, more specifically, the K47 two-layer nanocluster of the Na@16Sn@30Na composition with an NaSn16 internal Friauf polyhedron and 30 Na atoms in the shell and a K64 two-layer nanocluster of the 0@8(Sn4Ba4)@56(Na4Sn52) composition with the Sn4Ba4 internal polyhedron and 56 (4Na + 52Sn) atoms in the shell. The symmetrical and topological codes of self-assembly processes of 3D structures from K64 and K47 cluster precursors are reconstructed in the following form: primary chain → microlayer → microframework. The Na4 and Sn8 clusters with the -43m symmetry and Na atoms are determined as the spacers occupying the voids in the 3D framework from the K64 and K47 nanoclusters.

Cluster Self-Organization of Intermetallic Systems: New Three-Layer Cluster Precursor K136 = 0@Zn12@32(Mg20Zn12)@92(Zr12Zn80) and a New Two-Layer Cluster Precursor K30 = 0@Zn6@Zn24 in the Crystal Structure of Zr6Mg20Zn128-cP154

Using computer methods (ToposPro software package), the geometrical and topological analysis of the crystal structure of the Zr6Mg20Zn128-cP154 intermetallic compound with cubic cell parameters a = 13.709 A, V = 2576.42 A3, and space group Pm-3 is carried out. Two new nanocluster precursors with the ‑43m symmetry are determined: a three-layer K136 nanocluster of the 0@Zn12@32(Mg20Zn12@92(Zr12Zn80) composition with an internal icosahedron 0@Zn12 and 12 Zr atoms and 20 Zn atoms in 60-atomic Zn-shell and a two-layer K30 nanocluster of the 0@Zn6@Zn24 composition with an internal Zn6-octahedron and 24 Zn atoms in the external shell. The symmetrical and topological codes of the self-assembly processes of 3D structures from K136 and K30 nanocluster precursors are reconstructed in the following form: primary chain → microlayer → microframework. The Zn2 dimers are determined as the spacers occupying the voids in the 3D framework from K136 and K30 nanoclusters.

Cluster Self-Organization of Intermetallic Systems: Role of K5 = 0@5, K9 = 1@8 and K11 = 0@11 Clusters in the Self-Assembly of Crystal Structures

The combinatorial-topological analysis and simulation of self-assembly of the Na96Hg36-hR132 (space group R-3c, a = b = 9.228 A, c = 52.6380 A, V = 3881.91 A3) and Na12Hg8-tP20 (space group P42/mnm, a = b = 8.520, c = 7.800 A, V = 566.2 A3) crystal structures are conducted by computer-based methods (ToposPro program package). Polyhedral cluster precursors K11 = 0@11(Na8Hg3) and K9 = Hg@Na8 are first determined for the intermetallic compound Na96Hg36-hR132, while polyhedral cluster precursors K5 = 0@Na3Hg2 are determined for the intermetallic compound Na12Hg8-tP20. The symmetry and topology code of the self-assembly processes of the 3D structure Na96Hg36-hR132 from the nanocluster precursors K11 and K9, and of the 3D structure Na12Hg8-tP20 from the K5 clusters are reconstructed as the primary chain $$S_{{\text{3}}}^{1}$$ → layer $$S_{{\text{3}}}^{2}$$ → frame $$S_{{\text{3}}}^{3}.$$ The structural analysis of all known intermetallic compounds is conducted, and numerous examples of the assembly of their structures from the K5, K9, and K11 clusters are found.

Cluster Self-Organization of Intermetallic Systems: 124-Atom Cluster 0@12@32@80 and 44-Atom Cluster 0@12@32 for the Self-Assembly of Li48Na80Ga332-oF920 Crystal Structure

A combinatorial and topological analysis has been performed and self-assembly of the Li48Na80Ga332-oF920 crystal structure has been simulated (sp. gr. Fmmm, a = 24.666 A, b = 15.974 A, c = 45.271 A, V = 17 837 A3) using computer methods (the TOPOS program package). It is found that there are 11 827 versions of cluster representation of an atomic 3D net with the number of structural units from 4 to 14. Two framework-forming icosahedral clusters ico-K124 and ico-K44 are determined. The chemical composition of the shells of the three-layer 124-atom nanocluster ico-K124 is 0@12(Ga12)@32(Li20Ga12)@80(Li4Na16Ga60), its diameter is 17 A, and the symmetry is mmm. The chemical composition of the shells of the two-layer 44-atom nanocluster ico-K44 is 0@12(Ga12)@32(Li20Ga12), its diameter is 11 A, and the symmetry is 2/m. The symmetry and topology code of self-assembly of the crystal structure has been reconstructed from iсо-K124 and ico-K44 nanocluster precursors in the following form: primary chain → layer → framework. Ga7 clusters and dual chains of Ga atoms occupy 3D-framework voids.

Cluster Self-Organization of Intermetallic Systems. New Cluster Presursor (InNa5)(AuAu5) and Primary Chain with the 5m Symmetry for the Self-Assembly of the Na32Au44In24–oP100 Crystal Structure

The combinatorial-topological analysis and simulation of the self-assembly of the Na32Au44In24–oP100 (space group P bcm, a = 5.483 A, b = 24.519 A, c = 14.573 A, V = 1895 A3) crystal structure are conducted by the computer-based methods (TOPOS program package). A new type of the 12-atom K12 cluster formed from doubled pentagonal pyramids—AuAu5 and InNa5—is established. The maximal symmetry of the K12 cluster and the primary chain of translationally bound K12 clusters correspond to the noncrystallographic 5m symmetry. The symmetry and topological codes of the Na32Au44In24–oP100 3D structure’s self-assembly processes from the K12 nanocluster precursors are reconstructed in the following form: primary chain → microlayer → micro-framework. The primary chains of bound K12 clusters with the m symmetry are located in the direction [100], and the distance between cluster centers determines the vector’s value: a = 5.483 A. There are four nonparallel primary chains in the primary chain’s local environment. The chains from InAu atoms and NaAu2In2 clusters are located in the 2D layer between the primary chains. The distance between the equivalent chains in the direction [001] determined the vector’s value: c = 14.573 A. In the 3D framework in the direction [010], the distance between the equivalent 2D layers determined the vector’s value: b = 24.519 A.

Cluster Self-Organization of Intermetallic Systems: 0@12(Ga12)@24(Na12Ga12)@72(Rb4Na8Ga60) 108-Atom Three-Layer Icosahedral Cluster and 0@12(Ga12)@32(Na20Ga12) 44-Atom Two-Layer Icosahedral Cluster for Rb24Na200Ga696-oF920 Crystal Structure Self-Assembly

The combinatorial-topological analysis and simulation of the self-assembly of the Rb24Na200Ga696-oF920 (space group Fmmm, V = 17 837 A3) crystal structure are conducted by the computer-based methods (TOPOS program package). The number of options for the cluster representation of the 3D atomic framework with the number of structural units ranging from 4 to 12 came to 9565 variants. Two framework-forming icosahedral clusters—ico-K108 and ico-K44—are determined. The ico-K108 three-layer 108-atom nanocluster has the 0@12(Ga12)@24(Na12Ga12)@72(Rb4Na8Ga60) chemical composition of shells, a diameter of 17 A, and symmetry g = mmm. The ico-K44 two-layer 44-atom nanocluster has the 0@12(Ga12)@32(Na20Ga12) chemical composition of shells, a diameter of 11 A, and symmetry g = 2/m. The symmetry and topological codes of the Rb24Na200Ga696–oF920 3D structure’s self-assembly processes from the iсo-K108 and ico-K44 nanocluster precursors are reconstructed in the form primary chain → microlayer → microframework. The Rb spacer atoms and related groups of Ga atoms in the form of chains are located in the large voids of the 3D framework.

High-Quality Solution-Processed Metal-Oxide Gate Dielectrics Realized With a Photo-Activated Metal-Oxide Nanocluster Precursor

High-quality solution-derived amorphous alumina ( ${a}$ -Al2O3) dielectric has been achieved with [Al $_{\textsf {13}}{(}\mu _{\textsf {3}}$ -OH ${)}_{\textsf {6}}{(}\mu $ -OH)18 (H2O)24](NO3)15(Al-13 nanocluster) as a precursor and a local structure-controllable activation process via deep-UV-induced photochemical activation. The synergetic combination of an Al-13 nanocluster precursor and high-energetic photochemical activation enables the formation of highly dense ${a}$ -Al2O3 thin films via an efficient dissociation and rearrangement of the nanocluster skeleton. The electrical characteristics of the nanocluster-based ${a}$ -Al2O3 thin films were investigated in terms of their operative electronic conduction mechanism by comparing conventional nitrate-based and vacuum-deposited films. From these results, it was found that the leakage current density of solution-processed ${a}$ -Al2O3 layers is largely affected by their precursor structures. Finally, to demonstrate the versatility of the high-quality nanocluster-based ${a}$ -Al2O3 dielectrics, carbon nanotube and metal-oxide thin-film transistors were fabricated on low thermal budget stretchable and rigid substrates, respectively.

Cluster Self-Organization of Intermetallic Systems: Two-Layer Quasi-Spherical Nanocluster Precursors K69 and K26 in the Crystal Structure of Li26Na58Ba38 (cF488)

The geometric and topological analysis of the crystal structure of intermetallic Li26Na58Ba38 (cF488, a = 27.335 A, V = 20 424 A3, F-43m) is carried out using computer methods (ToposPro software package). The analysis method is based on determining the chemical composition and structure of an intermetallic cluster precursor and constructing a basic 3D network of the structure in the form of a graph whose nodes correspond to the position of their centers of gravity. Using the method of the complete decomposition of the 3D factor graph of the crystal structure into cluster substructures, we find two types of framework-forming nanoclusters, namely, K69 of the 1@16@52 composition and K26 of the 0@4@22 composition with point symmetry g =–43m. The symmetric and topological code of self-assembly of 3D structures from nanocluster precursors is reconstructed in the following form: primary chain → microlayer → microframework. Clusters Ba5, Na6(Na4), and Na2В are determined as spacers occupying voids in the 3D framework of nanoclusters K69 and K26.

The Symmetric and Topological Code of the Cluster Self-Assembly of the Icosahedral Structure of (Rb13)(Rb2O)3 (Fm-3c, cF184) Metal Oxide

A search for crystal structures of A n O m metal oxides containing icosahedral i–A@A12 cluster precursors is performed (TOPOS program package, ICSD and CRYSTMET databases). Among 1802 metal oxides, the local region represented by i–Cs@Cs12 is determined in the Cs7O (P-6m2) metal oxide. In the case of the (Rb13)(Rb2O)3 (Fm-3c, cF184, V = 12409.8 A3) metal oxide, the i–Rb@Rb12 cluster precursor with the symmetry m-3 and cluster spacers in the form of Rb–O–Rb chains, which occupy the pores in the threedimensional framework, are identified. Cluster i–Rb@Rb12 occupies position 8b with the highest possible crystallographic symmetry m-3 for icosahedron. The topological type of the basic 3D network, which characterizes the packing of cluster precursors Rb13, corresponds to a simple cubic 3D network P c (Pm-3m, cP1) with CN = 6. The symmetric and topological codes of the self-assembly processes of the crystal structure from the nanocluster precursors S 3 0 is fully reconstructed in the following form: primary chain S 3 1 → microlayer S 3 2 → microframework S 3 3 . Cluster precursors in the primary chain are flipped through 90° and are characterized by the maximum possible number of Rb–Rb bonds corresponding to 8 and this mechanism of local binding is realized at all stages of the self-assembly of the 3D framework structure. During the assembly of the primary chain and microlayer, there is additional binding of the Rb@Rb12 icosahedra via the Rb atoms of three-atomic cluster spacers Rb–O–Rb. In the 3D framework structure, in the local environment of Rb@Rb12, there are 12 Rb–O–Rb cluster spacers.

Modeling of self-organization processes in crystal-forming systems: Symmetry and topology code for the cluster self-assembly of crystal structures of intermetallic compounds

We performed the combinatorial and topological modeling of 1D, 2D, and 3D packs of symmetrically connected metal clusters in the form of tetrahedra А4. Three types of 1D chains with tetrahedral connectivity of 4, 6, and 8 were used to model 2D layers L-1, L-2, and L-3 and 3D frameworks FR-1, FR-2, FR-3, and FR-4. The model structures of the identified suprapolyhedral precursor clusters were used in topological analysis of crystal structures of intermetallic compounds (program package TOPOS and data bases ICSD and CRYSTMET). A match was found between the topological models of tetrahedral 3D frameworks and all types of crystal structures formed in binary systems; in Au–Cu: FR-1 for Cu3Au-cP4 (Auricupride), Cu2Au2-tP2 (Tetraauricupride), CuAu3-cP4 (Bogdanovite), and Cu2–x Au2 + x -cF4; in Mg–Cd: FR-3 for Mg3Cd-hP8, Mg2Cd2-oP4, MgCd3-hP8, and Mg2–x Cd2 + x -hP2; in Li–Hg: FR-2 for Li3Hg-cF16 and Li2Hg2-cP2 and FR-3 for LiHg3-hP8; in ternary system Li–Ag–Al: FR-2 for LiAg2Al-cF16 and Li2AgAl-cF16; and in quaternary system: framework FR-2 for LiMgPdSn-cF16. Framework FR-4 was identified in ternary intermetallic compounds A(Li2Sn2)-tI20, where A = Cu, Ag, Au. The structures of precursor nanoclusters were identified for other most abundant types of crystal structures of intermetallic compounds. For this purpose, we used the algorithms for partitioning the structural graph into nonintersecting cluster substructures and constructed the basal 3D network of the crystal structure in the form of a graph whose nodes correspond to the positions of the centers of precursor clusters. The cluster self-assembly was modeled for the following intermetallic compounds: Mg2Cu4-cF24, MgSnCu4-cF24, (ZrCu)Cu4-cF24,Mg2Zn4-hP12, (CaCu)Cu4-hP6, Cr3Si-cP8, Lu3Co(Fe3C)-cP16, Ca2Ge2(Cr2B2)-oC8, Y2Ni2(Fe2B2)-oP8, AlB2-hP3, Ca2Ge-oP12, CaHg2-hP3, Co2Ge(Ni2In)-hP6, Cs2Hg4-oI12, Ba4Po4-cF8, Mn5Ge3-hP16, and NaZn13-cF112. The symmetry and topological code of self-assembly from precursor nanoclusters was reconstituted for all crystal structure types of intermetallic compounds as: primary chain → microlayer → microframework. An abundance frequency analysis of topological and symmetry routes for the generation and evolution of precursor clusters enabled us to elucidate the crystal-formation laws in intermetallic systems on the microscopic level.

Modeling Self-Organization Processes in Crystal Forming Systems. Symmetry and Topology Codes of Cluster Self-Assembly of Crystal Structure of Na44Tl7 (Na6Tl)

The geometrical and topological analysis of the crystal structure of intermetallide Na44Tl7 (Na6Tl, a = 24.154 A, V = 14091.8 A3, space group F-43m) is carried out. The algorithms of the combinatorial-topological analysis, which ensure the recovery of the symmetrical and topological code (program) of the cluster self-assembly of the crystal structure of an intermetallide, are developed. The topological type of the basic 3D network for two types of cluster precursors corresponds to a simple cubic 3D network P c with CN = 6 and basic 2D network of type 44. There are eight cluster precursors in the unit cell: four K86 and four K50. The cluster precursor K86 made from 86 atoms is formed from eight icosahedra i-TlNa12 linked by the apices. The center of the cluster precursor K86 is at the position 4a (0, 0, 0) with the point symmetry g = –43m. The 50-atomic cluster precursor K50 consists of six i-TlNa12 icosahedra. The center of the cluster precursor K50 is in the partial position 4b (0, 0, 0) with the point symmetry g = –43m. The symmetrical and topological codes of the self-assembly of 3D structures from nanocluster precursors K86 and K50 are reconstructed in the following form: primary chain → microlayer → microframework.

Ultralow-Temperature Solution-Processed Aluminum Oxide Dielectrics via Local Structure Control of Nanoclusters.

Oxide dielectric materials play a key role in a wide range of high-performance solid-state electronics from semiconductor devices to emerging wearable and soft bioelectronic devices. Although several previous advances are noteworthy, their typical processing temperature still far exceeds the thermal limitations of soft materials, impeding their wide utilization in these emerging fields. Here, we report an innovative route to form highly reliable aluminum oxide dielectric films using an ultralow-temperature (<60 °C) solution process with a class of oxide nanocluster precursors. The extremely low-temperature synthesis of oxide dielectric films was achieved by using low-impurity, bulky metal-oxo-hydroxy nanoclusters combined with a spatially controllable and highly energetic light activation process. It was noteworthy that the room-temperature light activation process was highly effective in dissociating the metal-oxo-hydroxy clusters, enabling the formation of a dense atomic network at low temperature. The ultralow-temperature solution-processed oxide dielectrics demonstrated high breakdown field (>6 MV cm-1), low leakage (∼1 × 10-8 A cm-2 at 2 MV cm-1), and excellent electrical stability comparable to those of vacuum-deposited and high-temperature-processed dielectric films. For potential applications of the oxide dielectrics, transparent metal oxides and carbon nanotube active devices as well as integrated circuits were implemented directly on both ultrathin polymeric and highly stretchable substrates.

Three-dimensional macroporous carbon/hierarchical Co3O4 nanoclusters for nonenzymatic electrochemical glucose sensor

A novel supporting material named as three-dimensional kenaf stem-derived carbon (3D-KSCs) was used to load hierarchical Co3O4 nanoclusters for electrochemical sensing glucose. The 3D-KSCs/hierarchical Co3O4 nanoclusters were constructed by two steps. Los of acicular precursor nanoclusters firstly grew on the channels of 3D-KSCs densely by hydrothermal method and then the as-prepared 3D-KSCs/hierarchical Co3O4 nanoclusters was obtained by thermal pyrolysis of the 3D-KSCs/precursors nanocomposites at 400°C. The 3D macroporous configuration of 3D-KSCs resulted in lots of hierarchical Co3O4 nanoclusters arrayed on the surface of 3D-KSCs owing to its large enough specific surface area, which effectively avoided their aggregations and improved the stability of nanocomposites. The obtained 3D-KSCs/hierarchical Co3O4 nanoclusters showed a large number of needle-shaped and layered Co3O4 nanoclusters uniformly grew on the macropore’s walls of 3D-KSC. Due to its unique nanostructures, the 3D-KSCs/hierarchical Co3O4 nanoclusters integrated electrode showed superior performance for nonenzymatic electrochemical glucose sensing, showing wide linear range (0.088–7.0mM) and low detection limit of 26μM. It might be a new strategy to prepare nanostructures on 3D-KSC for future applications.

Symmetry and topology code of cluster self-assembly of icosahedral framework structures of boron and borides

The topological types of suprapolyhedral clusters composed of i-B12 icosahedra have been modeled. The models of icosahedral supraclusters have been used in analysis of the crystal structures of boron and borides (the TOPOS program package). To identify nanocluster precursors in crystal structures, there have been used special algorithms for partitioning structural graphs into disjoint substructures and constructing a basis 3D network of the structure as a graph with the nodes corresponding to the positions of the centroids of the cluster precursors. The cluster self-assembly have been modeled for 25 types of icosahedral framework structures of boron—B12-hR 12, (B12)2(B2)2-oP 28, (B12)4B2-P50, B196-tP 196, and B333-hR 333; binary borides—(B12)O2-hR 14, (B12)P2-hR 14, and (B12)(CBC)-hR 15; templated metal borides—Na2(B12)2B6-oI 64, Mg2(B12)B2-oI 68, Tb(B12)(B4)-mI 60, Al4(B12)4B8-oC 88, (B12)4(Si4)4-oI 64, (B12)4B2Be4-tP 58, Ti2(B12)4B2-tP 52, Sc12B180-tP 192, Cu4Sc12B180-tP 192, Si1.5Sc9B178-tP 216, Mg28B360-oP 388, Al28B352-oP 384, Si28B352-oP 306, Y24(B156)8(B39)8-cF1944, Sc10B315-hR339, and Li24B315-hR336. The symmetry and topology code of the crystal structure self-assembly from nanocluster precursors in the form of primary chain → microlayer → microframework has been completely restored. Frequency analysis of various topological and symmetry pathways for the formation and evolution of cluster precursors makes it possible to elucidate crystal-formation trends in inorganic systems at the microscopic level.

Porous Carbon-Supported Gold Nanoparticles for Oxygen Reduction Reaction: Effects of Nanoparticle Size.

Porous carbon-supported gold nanoparticles of varied sizes were prepared using thiolate-capped molecular Au25, Au38, and Au144 nanoclusters as precursors. The organic capping ligands were removed by pyrolysis at controlled temperatures, resulting in good dispersion of gold nanoparticles within the porous carbons, although the nanoparticle sizes were somewhat larger than those of the respective nanocluster precursors. The resulting nanocomposites displayed apparent activity in the electroreduction of oxygen in alkaline solutions, which increased with decreasing nanoparticle dimensions. Among the series of samples tested, the nanocomposite prepared with Au25 nanoclusters displayed the best activity, as manifested by the positive onset potential at +0.95 V vs RHE, remarkable sustainable stability, and high numbers of electron transfer at (3.60-3.92) at potentials from +0.50 to +0.80 V. The performance is comparable to that of commercial 20 wt % Pt/C. The results demonstrated the unique feasibility of porous carbon-supported gold nanoparticles as high-efficiency ORR catalysts.

Modeling of self-organization processes in crystal-forming systems: Symmetry and topology code for cluster self-assembly of crystal structures for molecular and framework compounds

This is a review over the state of art in self-organization in crystal-forming systems, where a longrange order appears spontaneously in the arrangement of nanoscale building units of any nature (atomic clusters and molecules), which initially existed in a dynamic state as a chaotic mixture. The focus is on bimolecular compounds where building units are M-octahedra M(O, OH, H2O) and T-tetrahedra T(O, OH)4 bonded by OH–O hydrogen bonds and/or bridging oxygen atoms O. The combinatorial–topological modeling of 1D and 2D packings of suprapolyhedral clusters (MT)n has been carried out. These packings are symmetrically and topologically conceivable types of molecular MT clusters S03, from which chains S13 and 2D microlayers S23 are formed. The theoretically derived model MT-clusters (MT)n are compared with known types of precursor clusters in the molecular and framework MT-structures of polyvalent metal sulfates and their analogues. Combinatorial–topological analysis algorithms are provided to restore, from structure data, the convergent matrix crystal structure self-assembly code in the form of the sequence of significant elementary events. Crystal structure modeling involves combinatorial–topological analysis methods, whose underlying idea is the recogniition of packing-forming precursor nanoclusters and the construction of the relevant basal 2D and 3D networks in the form of graphs where nodes correspond to the positions of their centroids. The model is universal and has first been used to model the cluster self-assembly of molecular MT structures for V(2+)(H2O)4(SO4) (V-Rozenite), V(4+)O(H2O)5(SO4)(H2O) (SYN1), V(4+)O(H2O)5(SO4) (Orthominasragrite, Minasragrite, Anorthominasragrite), V(4+)O(H2O)3(SO4) (Bobjonesite); framework MT structures V(4+)O(SO4)(H2(SO4) (SYN2), V(4+)O(SO4) (Pauflerite and SYN3), V(4+)2O3(SO4)2 (SYN4), V(4+)2O3(SeO4)2 (SYN5), Fe(3+)2(SO4)3 (LIPHOS), and Fe(3+)2(SO4)3 (NASICON); and for templated framework MT structures (NH4)2[Ga2(PO4)2F2] (KTP), (NH4)2[Ga2(PO4)2(HF)F2] (p-KTP), TlMo2(PO4)3 (SYN06), and K2Mg2(SO4)3 (Langbeinite). Frequency analysis of topological and symmetry pathways in the formation and evolution of clusters (from primary chain S13 through microlayer S23 to microframework S33) elucidates new crystal-formation trends in diverse chemical systems at the microscopic level.

Modeling of self-organization processes in crystal-forming systems: Symmetry and topology code for cluster self-assembly of crystal structures in MT-structures of polyvalent sulfates and phosphates

We consider the supramolecular chemistry of polyvalent metal sulfates and phosphates built of M(n+)(O, OH, H2O)6 polyhedral clusters with octahedral O-coordination (M-polyhedra) and SO4 and PO4 polyhedral clusters with tetrahedral O-coordination (T-polyhedra). These compounds form molecular (insular), chain, layered, or framework 3D MT structures by means of directed (bridging) hydrogen bonds O–H…O and/or bridging covalent O-bonds. Combinatorial–topological analysis algorithms are provided to restore, from structure data, the convergent matrix crystal structure self-assembly code. Cluster self-assembly modeling has been performed for the following sulfates: MgSO4 (Pnma and Cmcm), MgSO4 ∙ 1H2O (Kieserite), and CuSO4 ∙ 3H2O (Bonattite) having 3D MT strucutres; MgSO4 ∙ 2H2O (Sanderite), MgSO4 · 2.5H2O, MnSO4 · 3H2O, and MnSO4(OH) · 2H2O having 2D MT structures; MgSO4 · 4H2O (Cranswickite) and MgSO4 · 5H2O (Pentahydrite) having 1D MT structures; and MgSO4 · 4H2O (Starkeyite) having a 0D MT structure, for the following phosphates: (VO)(HPO4) (P-1), MgSO4 · H2O (Kieserite), and CuSO4 · 3H2O (Bonattite) having 3D MT structures; (VO)(HPO4)(H2O)0.5 (P121/c1 and Pmmn), (VO)(HPO4)(H2O)2 (P4/nmm and P121/c1), V(3+)(PO4)(H2O)2 (P121/n1), V(3+)(PO4)(H2O)4 (C12/c1), and Mg(HPO4)(H2O)3 (Newberyite, Pbca) having 2D MT structures; phosphite (VO(H2O)2)(HPO3)(H2O)3 (P41) and phosphate (VO)(HPO4)(H2O)4 (P-1) having 1D MT structures. For all compounds, the symmetry and combinatorial codes of cluster self-assembly code in the form of the following sequence: precursor nanocluster S30 → primary chain S31→ microlayer S32→ microframework S33. At the stage of primary chain S31 formation, in all of MT crystal structures considered, precursor clusters are four-polyhedral MTMT chains, transor cis, and their derivatives with additional O-bonds between polyhedra and ring cluster M2T2 (the result of coiling a cis-chain into a ring). Frequency analysis of topological and symmetry pathways in the formation and evolution of MT-clusters (from primary chain S31 through microlayer S32 to microframework S33) elucidates new crystal-formation trends in diverse chemical systems at the microscopic level.