Unprecedented Architectures Research Articles

Defects in graphene-based heterostructures: topological and geometrical effects.

The combination of graphene (Gr) and graphene-like materials provides the possibility of using two-dimensional (2D) atomic layer building blocks to create unprecedented architectures. The most attractive characteristics are strongly dependent on the various spatial structures, mainly including in-plane heterostructures butt-joined at the side of an atomic monolayer through covalent bonds, van der Waals (vdW) heterostructures involving a vertically stacked hybrid structure, and their combinations. Heterostructures can not only overcome the limitations inherent to each material but may also obtain new features by appropriate material combination. However, heterostructures made of vdW force superposition or covalent bond splicing are prone to defects. The introduction of external and internal defects causes local deformation and stress in the material, thereby affecting the physical properties of the material, such as its transport properties and mechanical properties. Therefore, research, utilization and control of these defects are highly critical. This paper reviews the vacancy, topological and geometrical effects of defects in modulating the structures and mechanical responses of Gr-based heterostructures. Moreover, the coupling effects of various defects on the Gr-based heterostructures in multi-physics fields are also discussed. This work aims to improve the understanding of the physical mechanism of defective configurations and their association in low dimensions, so as to realize various configurations and to aid the search for new usages.

Novel rearranged acetophenone derivatives possessing diverse architectures from the leaves of Melicope ptelefolia

Melicolones C–K (1–9), nine acetophenone derivatives with three unprecedented architectures, were characterized from the leaves of Melicope ptelefolia. Among them, melicolone C (1) was a novel acetophenone analogue possessing a highly rearranged spiro skeleton. Melicolones D-F (2–4) were three novel acetophenone congeners bearing unusual octalactone ring. Melicolones G-K (5–9) were five new prenylated acetophenone derivatives featuring a 9-oxatricyclo [3.2.1.13, 8]nonane core. Their structures were established by extensive spectroscopic analysis and ECD spectra. These different structures were presumably derived from the same precursor via three major biosynthetic pathways. Compounds 5–9 exerted moderate effects to reverse multidrug-resistance in MCF-7/ADR cells with reversal fold values ranging from 6.2 to 13.3.

Structurally diverse diterpenoids from Isodon pharicus

Twenty-one structurally diverse diterpenoids (1–21), wherein 1, 2, and 4 represented unprecedented architectures, were isolated from Isodon pharicus.

Oxidative Dissolution of Resoles: A Versatile Approach to Intricate Nanostructures.

Resoles are resins obtained by base-catalyzed phenol-formaldehyde condensation with a three-dimensional cross-linked framework. They are considered as highly chemical-resistant, and calcination is thus generally used in the treatment of resole-type resins, which significantly limits the diversity of nanostructured materials that can be derived from resole-type resins. Herein, we report that selected metal nitrate solutions can be used to dissolve various types of nanostructured resoles through an oxidative dissolution process. This strategy not only enables the controlled dissolution of resoles, but more importantly provides a new approach to selectively etch resole-based nanocomposites to give rise to a variety of nanostructured materials with unprecedented architectures and great potential in bioapplications.

Oxidative Dissolution of Resoles: A Versatile Approach to Intricate Nanostructures

AbstractResoles are resins obtained by base‐catalyzed phenol–formaldehyde condensation with a three‐dimensional cross‐linked framework. They are considered as highly chemical‐resistant, and calcination is thus generally used in the treatment of resole‐type resins, which significantly limits the diversity of nanostructured materials that can be derived from resole‐type resins. Herein, we report that selected metal nitrate solutions can be used to dissolve various types of nanostructured resoles through an oxidative dissolution process. This strategy not only enables the controlled dissolution of resoles, but more importantly provides a new approach to selectively etch resole‐based nanocomposites to give rise to a variety of nanostructured materials with unprecedented architectures and great potential in bioapplications.

Controlled growth and shape-directed self-assembly of gold nanoarrows.

Self-assembly of colloidal nanocrystals into complex superstructures offers notable opportunities to create functional devices and artificial materials with unusual properties. Anisotropic nanoparticles with nonspherical shapes, such as rods, plates, polyhedra, and multipods, enable the formation of a diverse range of ordered superlattices. However, the structural complexity and tunability of nanocrystal superlattices are restricted by the limited geometries of the anisotropic nanoparticles available for supercrystal self-assembly. We show that uniform gold nanoarrows (GNAs) consisting of two pyramidal heads connected by a four-wing shaft are readily synthesized through controlled overgrowth of gold nanorods. The distinct concave geometry endows the GNAs with unique packing and interlocking ability and allows for the shape-directed assembly of sophisticated two-dimensional (2D) and 3D supercrystals with unprecedented architectures. Net-like 2D supercrystals are assembled through the face-to-face contact of the GNAs lying on the pyramidal edges, whereas zipper-like and weave-like 2D supercrystals are constructed by the interlocked GNAs lying on the pyramidal {111} facets. Furthermore, multilayer packing of net-like and weave-like 2D assemblies of GNAs leads to non-close-packed 3D supercrystals with varied packing efficiencies and pore structures. Electromagnetic simulation of the diverse nanoarrow supercrystals exhibits exotic patterns of nanoscale electromagnetic field confinement. This study may open new avenues toward tunable self-assembly of nanoparticle superstructures with increased complexity and unusual functionality and may advance the design of novel plasmonic metamaterials for nanophotonics and reconfigurable architectured materials.

Capturing "Extraordinary" Soft-Assembled Charge-Like Polypeptides as a Strategy for Nanocarrier Design.

The rational design of nanomedicines is a challenging task given the complex architectures required for the construction of nanosized carriers with embedded therapeutic properties and the complex interface of these materials with the biological environment. Herein, an unexpected charge-like attraction mechanism of self-assembly for star-shaped polyglutamates in nonsalty aqueous solutions is identified, which matches the ubiquitous "ordinary-extraordinary" phenomenon previously described by physicists. For the first time, a bottom-up methodology for the stabilization of these nanosized soft-assembled star-shaped polyglutamates is also described, enabling the translation of theoretical research into nanomaterials with applicability within the drug-delivery field. Covalent capture of these labile assemblies provides access to unprecedented architectures to be used as nanocarriers. The enhanced in vitro and in vivo properties of these novel nanoconstructs as drug-delivery systems highlight the potential of this approach for tumor-localized as well as lymphotropic delivery.

Electronic Properties of MoS2–WS2 Heterostructures Synthesized with Two-Step Lateral Epitaxial Strategy

Formation of heterojunctions of transition metal dichalcogenides (TMDs) stimulates wide interest in new device physics and technology by tuning optical and electronic properties of TMDs. TMDs heterojunctions are of scientific and technological interest for exploration of next generation flexible electronics. Herein, we report on a two-step epitaxial ambient-pressure CVD technique to construct in-plane MoS2-WS2 heterostructures. The technique has the potential to artificially control the shape and structure of heterostructures or even to be more potentially extendable to growth of TMD superlattice than that of one-step CVD technique. Moreover, the unique MX2 heterostructure with monolayer MoS2 core wrapped by multilayer WS2 is obtained by the technique, which is entirely different from MX2 heterostructures synthesized by existing one-step CVD technique. Transmission electron microscopy, Raman and photoluminescence mapping studies reveal that the obtained heterostructure nanosheets clearly exhibit the modulated structural and optical properties. Electrical transport studies demonstrate that the special MoS2 (monolayer)/WS2 (multilayer) heterojunctions serve as intrinsic lateral p-n diodes and unambiguously show the photovoltaic effect. On the basis of this special heterostructure, depletion-layer width and built-in potential, as well as the built-in electric field distribution, are obtained by KPFM measurement, which are the essential parameters for TMD optoelectronic devices. With further development in future studies, this growth approach is envisaged to bring about a new growth platform for two-dimensional atomic crystals and to create unprecedented architectures therefor.

ChemInform Abstract: Sulfite Anions as Structure‐Directing Templates for the Engineering of Modular Polyoxometalates

AbstractReview: ≈50 refs.

Sulfite Anions as Structure‐Directing Templates for the Engineering of Modular Polyoxometalates

AbstractPolyoxometalates (POMs) are anionic metal oxides and encompass a diverse family of nanosized compounds with an unmatched range of architectures and physical properties. The use of the pyramidal sulfite anion, with its numerous coordination modes, has introduced structural diversity into the POM‐based chemical systems, giving rise to the formation of novel synthons for the construction of unprecedented architectures ranging from low‐nuclearity, isolable secondary building units to POM‐based molecular nanoparticles, open‐framework and 3D coordination materials, and the emergence of novel properties.

Double CH Bond Activation of C(sp3)H2 Groups for the Preparation of Complexes with Back‐to‐Back Bisimidazolinylidenes

Two-headed carbenes: N-heterocyclic carbene complexes of rhodium and iridium were obtained by the double CH activation of CH2 groups in N heterocycles (see structure: C gray, N blue, Cl green, Ir pink). The reaction constitutes a valuable approach to new carbene ligands with unprecedented architectures.

The Use of a Bis(phenylpyrazolyl)pyridyl Ligand to Prepare [Mn4] and [Mn10] Cage Complexes

Many branches in molecular magnetism live on the production of novel transition-metal (TM) coordination clusters. This has been the source of high-spin molecules, most single-molecule magnets (SMMs), or the possible future qubits for quantum computing. Without doubt, the great advances made in these areas have benefited, for the most part, from the preparation of molecules through so-called “serendipitous self-assembly”. Even though the designed preparation of clusters with predetermined structures and properties is highly desirable, it continues to be a huge synthetic challenge. Therefore, there is no reason to think that the “nonpredictable” approach will cease to be instrumental in the near future. For this, synthetic coordination chemists will keep providing original methods of preparation of polynuclear TM complexes. Typically, these are produced from reactions involving one or more small ligands with donor atoms capable of bridging metals, normally exhibiting several potential coordination modes. By contrast, the synthesis of large multidentate ligands with numerous donor atoms is far less common in this context. We have recently prepared a new ligand with two aligned hydroxyphenylpyrazolyl units separated by a pyridine group (2,6-bis[5-(2-hydroxyphenyl)pyrazol-3-yl]pyridine, H4L, Scheme 1). [10] Hydroxyphenylpyrazolyl derivatives or related pyrazolinoles have proven to be excellent ligands for the assembly of TM clusters with novel structures. The build up of more than one such moiety on the same molecule promises to be an open door to a variety of unprecedented architectures. Ligand H4L is well suited, for example, to stimulate the aggregation of a sequence of five closely spaced metals within a cluster (Scheme 2B). We report herein very promis-

Hydrogen‐Bonding Motifs in Fullerene Chemistry

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hydrogen‐Bonding Motifs in Fullerene Chemistry

The combination of fullerenes and hydrogen-bonding motifs is a new interdisciplinary field in which weak intermolecular forces allow modulation of one-, two-, and three-dimensional fullerene-based architectures and control of their function. This Minireview aims to extend the scope of fullerene chemistry to a truly supramolecular level from which unprecedented architectures may evolve. It is shown that electronic communication in C(60)-based hydrogen-bonded donor-acceptor ensembles is at least as strong as that found in covalently connected systems and that hydrogen-bonding fullerene chemistry is a versatile concept for the construction of functional ensembles.