Self‐Assembly of a Low‐Symmetry Monodendron Containing Two Asymmetrically Linked Molecular Wedges

Herein, we describe the synthesis of a low‐symmetry monodendron, 3,4‐bis(dodecyloxy)‐5‐[3,4,5‐tris(dodecyloxy)benzyloxy]benzoic acid, following a simple route which starts from gallic acid ethyl ester and does not require any protecting groups. The self‐assembled structures formed by the compound in 3D and 2D were investigated by synchrotron X‐ray scattering and scanning force microscopy (SFM). In 3D, the compound forms a stable crystalline phase with an orthorhombic lattice in which the alkyl chains connected to different benzene rings form crystalline and amorphous domains. Upon cooling from the isotropic melt the compound exhibits a monotropic smectic mesophase. In 100‐nm‐thick films on a neutral substrate the structure loses its biaxiality, adopting a hexagonal columnar structure with the columns oriented parallel to the substrate. By contrast, in ultrathin films on graphite the SFM likely reveals two crystal orientations, which can develop due to the epitaxial adsorption on the substrate of the alkyl chains pertinent to different benzene rings.     

Transfer of Two‐Dimensional Oligonucleotide Patterns onto Stereocontrolled Plasmonic Nanostructures through DNA‐Origami‐Based Nanoimprinting Lithography

The precise functionalization of self‐assembled nanostructures with spatial and stereocontrol is a major objective of nanotechnology and holds great promise for many applications. Herein, the nanoscale addressability of DNA origami was exploited to develop a precise copy‐machine‐like platform that can transfer two‐dimensional oligonucleotide patterns onto the surface of gold nanoparticles (AuNPs) through a deliberately designed toehold‐initiated DNA displacement reaction. This strategy of DNA‐origami‐based nanoimprinting lithography (DONIL) demonstrates high precision in controlling the valence and valence angles of AuNPs. These DNA‐decorated AuNPs act as precursors in the construction of discrete AuNP clusters with desired chirality.     

Directed Self‐Assembly of DNA Tiles into Complex Nanocages

Tile‐based self‐assembly is a powerful method in DNA nanotechnology and has produced a wide range of well‐defined nanostructures. But the resulting structures are relatively simple. Increasing the structural complexity and the scope of the accessible structures is an outstanding challenge in molecular self‐assembly. A strategy to partially address this problem by introducing flexibility into assembling DNA tiles and employing directing agents to control the self‐assembly process is presented. To demonstrate this strategy, a range of DNA nanocages have been rationally designed and constructed. Many of them can not be assembled otherwise. All of the resulting structures have been thoroughly characterized by gel electrophoresis and cryogenic electron microscopy. This strategy greatly expands the scope of accessible DNA nanostructures and would facilitate technological applications such as nanoguest encapsulation, drug delivery, and nanoparticle organization.     

Three-Dimensional DNA Crystals with pH-Responsive Noncanonical Junctions

Three-dimensional (3D) DNA crystals have been envisioned as programmable biomaterial scaffolds for creating ordered arrays of biological and nonbiological molecules. Despite having excellent programmable properties, the linearity of the Watson-Crick B-form duplex imposes limitations on 3D crystal design. Predictable noncanonical base pairing motifs have the potential to serve as junctions to connect linear DNA segments into complex 3D lattices. Here, we designed crystals based on a template structure with parallel-stranded noncanonical base pairs. Depending on pH, the structures we determined contained all but one or two of the designed secondary structure interactions. Surprisingly, a conformational change of the designed Watson-Crick duplex region resulted in crystal packing differences between the predicted and observed structures. However, the designed noncanonical motif was virtually identical to the template when crystals were grown at pH 5.5, highlighting the motif's predictability. At pH 7.0 we observed a structurally similar variation on this motif that contains a previously unobserved C-G?G-C quadruple base pair. We demonstrate that these two variants can interconvert in crystallo in response to pH perturbations. This study spotlights several important considerations in DNA crystal design, describes the first 3D DNA lattice composed of A-DNA helical sheets, and reveals a noncanonical DNA motif that has adaptive features that may be useful for designing dynamic crystals or biomaterial assemblies.     

Programmable Assembly of Nano‐architectures through Designing Anisotropic DNA Origami Patches

Programmable assembly of nanoparticles (NPs) into well‐defined architectures has attracted attention because of tailored properties resulting from coupling effects. However, general and precise approaches to control binding modes between NPs remain a challenge owing to the difficulty in manipulating the accurate positions of the functional patches on the surface of NPs. Here, a strategy is developed to encage spherical NPs into pre‐designed octahedral DNA origami frames (DOFs) through DNA base‐pairings. The DOFs logically define the arrangements of functional patches in three dimensions, owing to the programmability of DNA hybridization, and thus control the binding modes of the caged nanoparticle with designed anisotropy. Applying the node‐and‐spacer approach that was widely used in crystal engineering to design coordination polymers, patchy NPs could be rationally designed with lower symmetry encoded to assemble a series of nano‐architectures with high‐order geometries.     

Stacking of Exfoliated Two‐Dimensional Materials: A Review

In recent years, two‐dimensional (2D) atomic crystals represented by graphene have opened up new fields of 2D physics. Layered materials with atomic layer thickness are self‐assembled into van der Waals heterostructures by weak van der Waals forces without considering lattice matching. Van der Waals heterostructures can not only enhance the performance of its constituent materials but also show new characteristics. High‐quality heterostructures require mechanically cleaved intrinsic 2D materials and flexible 2D material stacking techniques. Here, we summarize in detail the reliable exfoliation methods for large‐area single‐layer 2D materials and the dry and wet stacking techniques with high success rates. The twisted bilayer graphene is used as an example to briefly introduce the single‐crystal tearing method, which is currently the most practical method for preparing isotropic twisted heterostructures with high‐precision rotation angles. We hope to provide a valuable reference for researchers of 2D materials.     

DNA Terminal Mismatch‐Induced Stabilization of Polymer Micelles from RAFT‐Generated Poly(N‐isopropylacrylamide)‐DNA Block Copolymers

Temperature‐responsive diblock copolymers made of poly(N‐isopropylacrylamide) (PNIPAAm) generated by reversible addition‐fragmentation chain transfer (RAFT) polymerization and a single‐stranded DNA (ssDNA) self‐assembled into polymer micelles. The micelles consisted of the PNIPAAm core surrounded by the ssDNA corona with a hydrodynamic diameter up to 300 nm in an aqueous medium above the lower critical solution temperature. In a medium of high ionic strength, the formation of the fully matched duplex with the complementary ssDNA on the surface of the polymer micelles induced rapid and spontaneous aggregation. By contrast, the micelles remained dispersed under the identical conditions when single‐base‐substituted ssDNA was added to form the corresponding terminal‐mismatched duplex on the micellar surface. This highly sequence‐selective process took place irrespective of the size of the PNIPAAm core.     

Facile Synthesis of Three‐Dimensional Pt‐TiO2 Nano‐networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia–Borane

Three‐dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self‐assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt‐TiO₂ nano‐network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO₂ by atomic layer deposition (ALD) with angstrom‐level thickness precision. The 3D peptide‐TiO₂ nano‐network was further decorated with highly monodisperse Pt nanoparticles by using ozone‐assisted ALD. The 3D TiO₂ nano‐network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia–borane, generating three equivalents of H₂.     

Hierarchical Hollow Hydroxyapatite Microspheres: Microwave‐Assisted Rapid Synthesis by Using Pyridoxal‐5′‐Phosphate as a Phosphorus Source and Application in Drug Delivery

Three‐dimensional (3D) hydroxyapatite (HAP) hierarchical nanostructures, in particular hollow nanostructures, have attracted much attention owing to their potential applications in many biomedical fields. Herein, we report a rapid microwave‐assisted hydrothermal synthesis of a variety of hydroxyapatite hierarchical nanostructures that are constructed by the self‐assembly of nanorods or nanosheets as the building blocks, including HAP nanorod‐assembled hierarchical hollow microspheres (HA‐NRHMs), HAP nanorod‐assembled hierarchical microspheres (HA‐NRMs), and HAP nanosheet‐assembled hierarchical microspheres (HA‐NSMs) by using biocompatible biomolecule pyridoxal‐5′‐phosphate (PLP) as a new organic phosphorus source. The PLP molecules hydrolyze to produce phosphate ions under microwave‐hydrothermal conditions, and the phosphate ions react with calcium ions to form HAP nanorods or nanosheets; then, these nanorods or nanosheets self‐assemble to form 3D HAP hierarchical nanostructures. The preparation method reported herein is time‐saving, with microwave heating times as short as 5 min. The HA‐NRHMs consist of HAP nanorods as the building units, with an average diameter of about 50 nm. The effects of the experimental conditions on the morphology and crystal phase of the products are investigated. The hydrolysis of PLP under microwave‐hydrothermal conditions and the important role of PLP in the formation of 3D HAP hierarchical nanostructures are investigated and a possible formation mechanism is proposed. The products are explored for potential applications in protein adsorption and drug delivery. Our experimental results indicate that the HA‐NRHMs have high drug/protein‐loading capacity and sustained drug‐release behavior. Thus, the as‐prepared HA‐NRHMs are promising for applications in drug delivery and protein adsorption.     

Dendronized supramolecular polymers self‐assembled from dendritic ionic liquids

The synthesis, structural, and retrostructural analysis of a library of self‐assembling dendrons containing triethyl and tripropyl ammonium, pyridinium and 3‐methylimidazolium chloride, tetrafluoroborate, and hexafluorophosphate at their apex are reported. These dendritic ionic liquids self‐assemble into supramolecular columns or spheres which self‐organize into 2D hexagonal or rectangular and 3D cubic or tetragonal liquid crystalline and crystalline lattices. Structural analysis by X‐ray diffraction experiments demonstrated the self‐assembly of supramolecular dendrimers containing columnar and spherical nanoscale ionic liquid reactors segregated in their core. Both in the supramolecular columns and spheres the noncovalent interactions mediated by the ionic liquid provide a supramolecular polymer and therefore, these assemblies represent a new class of dendronized supramolecular polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4165–4193, 2009     

High‐Resolution Crystal Structure of a Silver(I)–RNA Hybrid Duplex Containing Watson–Crick‐like CSilver(I)C Metallo‐Base Pairs

Metallo‐base pairs have been extensively studied for applications in nucleic acid‐based nanodevices and genetic code expansion. Metallo‐base pairs composed of natural nucleobases are attractive because nanodevices containing natural metallo‐base pairs can be easily prepared from commercially available sources. Previously, we have reported a crystal structure of a DNA duplex containing T? Hg^II? T base pairs. Herein, we have determined a high‐resolution crystal structure of the second natural metallo‐base pair between pyrimidine bases C? Ag^I? C formed in an RNA duplex. One Ag^I occupies the center between two cytosines and forms a C? Ag^I? C base pair through N3? Ag^I? N3 linear coordination. The C? Ag^I? C base pair formation does not disturb the standard A‐form conformation of RNA. Since the C? Ag^I? C base pair is structurally similar to the canonical Watson–Crick base pairs, it can be a useful building block for structure‐based design and fabrication of nucleic acid‐based nanodevices.     

Social Self‐Sorting of Colloidal Families in Co‐Assembling Microgel Systems

Colloids are valuable model systems to understand the structure and dynamics of matter, explore new self‐assembly concepts, and realize advanced materials. Herein, we demonstrate social self‐sorting of co‐assembled families of colloids by orthogonal host/guest recognition using cyclodextrins. We show that mixtures of four partners self‐sort into their respective families without mutual interference. Additionally, the self‐assemblies and their interactions are switchable using orthogonal triggers. This study goes beyond previous features of molecular self‐sorting, and opens the design space for future self‐sorting colloidal systems via rationally designed molecular recognition.     

羧酸铜与单螺旋吡啶胺配体自组装的两种新型超分子配合物

Two novel supramolecular complexes [Cu（bpapa）（dhbd）]·CHaOH （1） and [Cu（bpapa）（ma）]·ma （2） （bpapa= bis[6-（2-pyridylamino）pyrid-2-yl]amine, dhbd=2,3-dihydroxybutanedioate dianion, ma=a-methacrylate） were rationally designed, synthesized and characterized by single crystal X-ray diffraction, IR, electronic spectroscopy and thermogravimetric analyses. Complex 1 was the first oligo-a-pyfidylamino complex based on hydroxypolycarboxylate and self-assembled into a 3D honeycomb configuration network with open channels and tubes containing 1D ladder-shaped double chains formed by hydrogen bonds and aromatic π-π stacking interactions. Complex 2 constructed a 2D supramolecular network extended by 1D chains from dimeric supramolecular synthon through noncovalent supramolecular interactions. In the two complexes, the chelating monohelical ligand adopted all-anti configuration. Density functional theory calculations were applied to 1 and 2.     

Supramolecular Reassembly of Self‐Exfoliated Ionic Covalent Organic Nanosheets for Label‐Free Detection of Double‐Stranded DNA

Ionic covalent organic nanosheets (iCONs), a member of the two‐dimensional (2D) nanomaterials family, offer a unique functional platform for a wide range of applications. Herein, we explore the potential of an ethidium bromide (EB)‐based covalent organic framework ( EB‐TFP ) that self‐exfoliates in water resulting in 2D ionic covalent organic nanosheets ( EB‐TFP‐iCONs ) for the selective detection of double‐stranded DNA (dsDNA). In an aqueous medium, the self‐exfoliated EB‐TFP‐iCONs reassemble in the presence of dsDNA resulting in hybrid EB‐TFP‐iCONs‐DNA crystalline nanosheets with enhanced fluorescence at 600 nm. Detailed steady‐state and time‐resolved emission studies revealed that the reassembly phenomenon was highly selective for dsDNA when compared to single‐stranded DNA (ssDNA), which allowed us to use the EB‐TFP‐iCONs as a 2D fluorescent platform for the label‐free detection of complementary DNA strands.     

Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States

Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole‐based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole‐based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin‐film states. Two oxadiazole‐based molecules and one thiadiazole‐based molecule exhibited supergelation ability in hydrocarbon solvents, which is mainly supported by attractive π–π interactions. These gels showed aggregation‐induced enhanced emission, which is of high technological importance for applications in solid‐state emissive displays. X‐ray diffraction studies of the xerogel fibers of oxadiazole‐based polycatenars revealed a columnar rectangular organization, whereas a hexagonal columnar arrangement was observed for thiadiazole‐based polycatenars. Rheological measurements carried out on the samples quantitatively confirmed the formation of gels and showed that these gels are mechanically robust. The impact of an atomic‐scale difference (oxygen to sulfur, <2 % of the molecular weight) on the self‐assembly and the macroscopic properties of those self‐assembled structures are clearly visualized.     

On‐Surface Self‐Assembly of a C3‐Symmetric π‐Conjugated Molecule Family Studied by STM: Two‐Dimensional Nanoporous Frameworks

The on‐surface self‐assembled behavior of four C ₃‐symmetric π‐conjugated planar molecules ( Tp , T12 , T18 , and Ex ) has been investigated. These molecules are excellent building blocks for the construction of noncovalent organic frameworks in the bulk phase. Their hydrogen‐bonded 2D on‐surface self‐assemblies are observed under STM at the solid/liquid interface; these structures are very different to those in the bulk crystal. Upon combining the results of STM measurements and DFT calculations, the formation mechanism of different assemblies is revealed; in particular, the critical role of hydrogen bonding in the assemblies. This research provides us with not only a deep insight into the self‐assembled behavior of these novel functional molecules, but also a convenient approach toward the construction of 2D multiporous networks.     

A Columnar Liquid‐Crystal Phase Formed by Hydrogen‐Bonded Perylene Bisimide J‐Aggregates

A new perylene bisimide (PBI) dye self‐assembles through hydrogen bonds and π–π interactions into J‐aggregates that in turn self‐organize into liquid‐crystalline (LC) columnar hexagonal domains. The PBI cores are organized with the transition dipole moments parallel to the columnar axis, which is an unprecedented structural organization in π‐conjugated columnar liquid crystals. Middle and wide‐angle X‐ray analyses reveal a helical structure consisting of three self‐assembled hydrogen‐bonded PBI strands that constitute a single column of the columnar hexagonal phase. This remarkable assembly mode for columnar liquid crystals may afford new anisotropic LC materials for applications in photonics.     

Naphthocrown‐Strapped Calix[4]pyrroles: Formation of Self‐Assembled Structures by Ion‐Pair Recognition

A new approach to the construction of self‐assembled structures is reported that is based on ion‐pair recognition. Towards this end, the calix[4]pyrrole naphthocrown‐4 hybrid structures 2 and 3 were prepared. These multitopic receptors contain recognition sites for both anions and cations. On the basis of solution‐phase ¹H NMR spectroscopic analysis and solid‐state single‐crystal X‐ray diffraction structural studies, it was established that receptors 2 and 3 are able to bind specific ion pairs with high selectivity via different binding modes. In the case of CsF and CsCl, the ion‐pair complexes formed from receptors 2 and 3 were found to self‐assemble to produce either linear supramolecular polymeric crystalline solids or nanotube‐like cyclic hexamers depending on the specific choice of ion pairs and crystallization solvents. Proton NMR studies provided evidence for solution‐phase self‐association in organic media.     

Robust Aqua Material: A Pressure‐Resistant Self‐Assembled Membrane for Water Purification

“Aqua materials” that contain water as their major component and are as robust as conventional plastics are highly desirable. Yet, the ability of such systems to withstand harsh conditions, for example, high pressures typical of industrial applications has not been demonstrated. We show that a hydrogel‐like membrane self‐assembled from an aromatic amphiphile and colloidal Nafion is capable of purifying water from organic molecules, including pharmaceuticals, and heavy metals in a very wide range of concentrations. Remarkably, the membrane can sustain high pressures, retaining its function. The robustness and functionality of the water‐based self‐assembled array advances the idea that aqua materials can be very strong and suitable for demanding industrial applications.     

Functionalizing Designer DNA Crystals with a Triple‐Helical Veneer

DNA is a very useful molecule for the programmed self‐assembly of 2D and 3D nanoscale objects. 1 The design of these structures exploits Watson–Crick hybridization and strand exchange to stitch linear duplexes into finite assemblies. 2 – 4 The dimensions of these complexes can be increased by over five orders of magnitude through self‐assembly of cohesive single‐stranded segments (sticky ends). 5 , 6 Methods that exploit the sequence addressability of DNA nanostructures will enable the programmable positioning of components in 2D and 3D space, offering applications such as the organization of nanoelectronics, 7 the direction of biological cascades, 8 and the structure determination of periodically positioned molecules by X‐ray diffraction. 9 To this end we present a macroscopic 3D crystal based on the 3‐fold rotationally symmetric tensegrity triangle 3 , 6 that can be functionalized by a triplex‐forming oligonucleotide on each of its helical edges.