Controlled Self‐Assembly of Functional Metal Octaethylporphyrin 1 D Nanowires by Solution‐Phase Precipitative Method

Metal octaethylporphyrin M(OEP) (M=Ni, Cu, Zn, Pd, Ag, and Pt) nanowires are fabricated by a simple solution‐phase precipitative method. By controlling the composition of solvent mixtures, the diameters and lengths of the nanowires can be varied from 20 to 70 nm and 0.4 to 10 μm, respectively. The Ag(OEP) nanowires have lengths up to 10 μm and diameters of 20–70 nm. For the M(OEP) nanowires, the growth orientation and packing of M(OEP) molecules are examined by powder XRD and SAED measurements, revealing that these M(OEP) nanowires are formed by the self‐assembly of M(OEP) molecules through intermolecular π???π interactions along the π???π stacking axis, and the M²⁺ ion plays a key role in the nanowire formation. Using the bottom contact field effect transistor structure and a simple drop‐cast method, a single‐crystal M(OEP) nanowires‐based field effect transistor can be readily prepared with prominent hole transporting behaviour and charge‐carrier mobility up to 10^?3–10^?2 cm² V^?1 s^?1 for holes, which are 10 times higher than that of vacuum‐deposited M(OEP) organic thin‐film transistors (OTFTs).     

Progress in Polydiacetylene Nanowires by Self‐Assembly and SelfPolymerization

In recent years, there has been immense interest in studying nanoscale aggregate structures derived from various polydiacetylenes (PDAs). The motivation for this is not only to understand the fundamental aggregate structures at different scales, but also to explore their potential for future technological applications. PDAs have been made sensitive to external stimuli such as light and chemical entities by incorporating a spectroscopically active moiety or a receptor unit as the head group of the PDA molecule. This makes them suitable for applications such as sensing and actuating. Furthermore, owing to the delocalization of π‐conjugated electrons, PDAs have been exploited as good candidates for organic nonlinear optical materials. This Focus Review highlights some of the instructive work done by various groups to develop well‐defined one‐dimensional assembly systems with a highly structural aspect ratio, which can be directly imaged by microscopic techniques.     

Flow‐Guided Assembly Processes

This Concept article focuses on capillary, hydrodynamics and electrokinetic flow‐guided assembly processes that can produce patterned or gradient functional surfaces either on solid surfaces or in deep micro‐ and nanoscale channels. This concept has the potential to produce low‐cost nanostructures, internal surface modifications, and devices in nanomedicine.     

Growth of Hydrophilic CuS Nanowires via DNA‐Mediated Self‐Assembly Process and Their Use in Fabricating Smart Hybrid Films for Adjustable Chemical Release

Facile growth of CuS nanowires through self‐assembly and their application as building blocks for near‐infrared light‐responsive functional films have been demonstrated. It is found that DNA is a key factor in preparing the CuS material with defined nanostructure. An exclusive oriented self‐aggregate growth mechanism is proposed for the growth of the nanowires, which might have important implications for preparing advanced, sophisticated nanostructures based on DNA nanotechnology. By employing the hydrophilic CuS nanowire as an optical absorber and thermosensitive nanogel as guest reservoir inside alginate film, a new platform for the release of functional molecules has been set up. In vitro studies have shown that the hybrid film possesses excellent biocompatibility and the release rate of chemical molecules from the film could be controlled with high spatial and temporal precision. Our novel approach and the resulting outstanding combination of properties may advance both the fields of DNA nanotechnology and light‐responsive devices.     

Programmed Self‐Assembly of a Quadruplex DNA Nanowire

The ability to produce, reproducibly and systematically, well‐defined quadruplex DNA nanowires through controlled rational design is poorly understood despite potential utility in structural nanotechnology. The programmed hierarchical self‐assembly of a long four‐stranded DNA nanowire through cohesive self‐assembly of GpC and CpG “sticky” ends is reported. The encoding of bases within the quadruplex stem allows for an uninterrupted π‐stacking system with rectilinear propagation for hundreds of nanometers in length. The wire is mechanically stable and features superior nuclease resistance to double‐stranded DNA. The study indicates the feasibility for programmed assembly of uninterrupted quadruplex DNA nanowires. This is fundamental to the systematic investigation of well‐defined DNA nanostructures for uses in optoelectronic and electronic devices as well as other structural nanotechnology applications.     

Site‐Directed,On‐Surface Assembly of DNA Nanostructures

Two‐dimensional DNA lattices have been assembled from DNA double‐crossover (DX) motifs on DNA‐encoded surfaces in a site‐specific manner. The lattices contained two types of single‐stranded protruding arms pointing into opposite directions of the plane. One type of these protruding arms served to anchor the DNA lattice on the solid support through specific hybridization with surface‐bound, complementary capture oligomers. The other type of arms allowed for further attachment of DNA‐tethered probe molecules on the opposite side of the lattices exposed to the solution. Site‐specific lattice assembly and attachment of fluorophore‐labeled oligonucleotides and DNA–protein conjugates was demonstrated using DNA microarrays on flat, transparent mica substrates. Owing to their programmable orientation and addressability over a broad dynamic range from the nanometer to the millimeter length scale, such supramolecular architecture might be used for presenting biomolecules on surfaces, for instance, in biosensor applications.     

Ionic‐Liquid‐Assisted Formation of Silver Nanowires

Down to the wire : A simple and effective method to synthesize silver nanowires through an ionic‐liquid‐assisted polyol process is developed (see scheme; scale bar=5 nm). The ionic liquids are tuned to provide the anisotropic growth of silver nanoparticles into nanowires.

     

Self‐Assembly of a Four‐Helix Bundle on a DNA Quadruplex

Come together : A novel method for assembling monomers and controlling structure of a de novo helix bundle protein is described. A guanine (G)‐rich oligodeoxynucleotide scaffold forms a hydrogen‐bonded DNA quadruplex in the presence of potassium counterions, thereby inducing a helical structure and fourfold stoichiometry in conjugated, amphiphilic peptide sequences. The DNA scaffold shows potential for rapidly assembling designed proteins.

     

Surface‐Assisted Large‐Scale Ordering of DNA Origami Tiles

The arrangement of DNA‐based nanostructures into extended higher order assemblies is an important step towards their utilization as functional molecular materials. We herein demonstrate that by electrostatically controlling the adhesion and mobility of DNA origami structures on mica surfaces by the simple addition of monovalent cations, large ordered 2D arrays of origami tiles can be generated. The lattices can be formed either by close‐packing of symmetric, non‐interacting DNA origami structures, or by utilizing blunt‐end stacking interactions between the origami units. The resulting crystalline lattices can be readily utilized as templates for the ordered arrangement of proteins.     

Programmed‐Assembly System Using DNA Jigsaw Pieces

A novel method for assembling multiple DNA origami structures has been developed by using designed 2D DNA origami rectangles, so‐called “DNA jigsaw pieces” that have sequence‐programmed connectors. Shape and sequence complementarity were introduced to the concavity and convex connectors in the DNA rectangles for selective connection with the help of nonselective π‐stacking interactions between the side edges of the DNA jigsaw piece structures. Single DNA jigsaw piece units were assembled into unidirectional nanostructures with the correct alignment and uniform orientation. Three and five different DNA jigsaw pieces were assembled into predesigned and ordered nanostructures in a programmed fashion. Finally, three‐, four‐, and five‐letter words have been displayed by using this programmed DNA jigsaw piece system.     

A Signal‐Passing DNA‐Strand‐Exchange Mechanism for Active Self‐Assembly of DNA Nanostructures

DNA nanostructured tiles play an active role in their own self‐assembly in the system described herein whereby they initiate a binding event that produces a cascading assembly process. We present DNA tiles that have a simple but powerful property: they respond to a binding event at one end of the tile by passing a signal across the tile to activate a binding site at the other end. This action allows sequential, virtually irreversible self‐assembly of tiles and enables local communication during the self‐assembly process. This localized signal‐passing mechanism provides a new element of control for autonomous self‐assembly of DNA nanostructures.     

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.