Steering On‐Surface Reactions by a Self‐Assembly Approach

4,4′‐Bis(2,6‐difluoropyridin‐4‐yl)‐1,1′:4′,1′′‐terphenyl (BDFPTP) molecules underwent dehydrocyclization and covalent coupling reactions on Au(111) according to scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Self‐assembly of the reactants in well‐defined molecular domains prior to reaction could greatly enhance the regioselectivity of the dehydrocyclization reaction and suppress defluorinated coupling, demonstrating that self‐assembly can efficiently steer on‐surface reactions. Such a strategy could be of great importance in surface chemistry and widely applied to control on‐surface reactions.     

Programmable Supra‐Assembly of a DNA Surface Adapter for Tunable Chiral Directional Self‐Assembly of Gold Nanorods

An important challenge in molecular assembly and hierarchical molecular engineering is to control and program the directional self‐assembly into chiral structures. Here, we present a versatile DNA surface adapter that can programmably self‐assemble into various chiral supramolecular architectures, thereby regulating the chiral directional “bonding” of gold nanorods decorated by the surface adapter. Distinct optical chirality relevant to the ensemble conformation is demonstrated from the assembled novel stair‐like and coil‐like gold nanorod chiral metastructures, which is strongly affected by the spatial arrangement of neighboring nanorod pair. Our strategy provides new avenues for fabrication of tunable optical metamaterials by manipulating the directional self‐assembly of nanoparticles using programmable surface adapters.     

DNA Trojan Horses: Self‐Assembled Floxuridine‐Containing DNA Polyhedra for Cancer Therapy

Based on their structural similarity to natural nucleobases, nucleoside analogue therapeutics were integrated into DNA strands through conventional solid‐phase synthesis. By elaborately designing their sequences, floxuridine‐integrated DNA strands were synthesized and self‐assembled into well‐defined DNA polyhedra with definite drug‐loading ratios as well as tunable size and morphology. As a novel drug delivery system, these drug‐containing DNA polyhedra could ideally mimic the Trojan Horse to deliver chemotherapeutics into tumor cells and fight against cancer. Both in vitro and in vivo results demonstrate that the DNA Trojan horse with buckyball architecture exhibits superior anticancer capability over the free drug and other formulations. With precise control over the drug‐loading ratio and structure of the nanocarriers, the DNA Trojan horse may play an important role in anticancer treatment and exhibit great potential in translational nanomedicine.     

Photoresponsive Nanosheets of Polyoxometalates Formed by Controlled Self‐Assembly Pathways

Anionic Keggin polyoxometalates (POMs) and ether linkage‐enriched ammonium ions spontaneously self‐assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single‐crystal X‐ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self‐assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site‐specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO₃ and site‐selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag⁺ ions on the nanosheet surface.     

Oriented Gold Nanorod Arrays: Self‐Assembly and Optoelectronic Applications

Self‐assembly of anisotropic plasmonic nanomaterials into ordered superstructures has become popular in nanoscience because of their unique anisotropic optical and electronic properties. Gold nanorods (GNRs) are a well‐defined functional building block for fabrication of these superstructures. They possess important anisotropic plasmonic characteristics that result from strong local electric field and are responsive to visible and near‐IR light. There are recent examples of assembling the GNRs into ordered arrays or superstructures through processes such as solvent evaporation and interfacial assembly. In this Minireview, recent progress in the development of the self‐assembled GNR arrays is described, with focus on the formation of oriented GNR arrays on substrates. Key driving forces are discussed, and different strategies and self‐assembly processes of forming oriented GNR arrays are presented. The applications of the oriented GNR arrays in optoelectronic devices are also overviewed, especially surface enhanced Raman scattering (SERS).     

Harnessing Colloidal Crack Formation by Flow‐Enabled Self‐Assembly

Self‐assembly of nanomaterials to yield a wide diversity of high‐order structures, materials, and devices promises new opportunities for various technological applications. Herein, we report that crack formation can be effectively harnessed by elaborately restricting the drying of colloidal suspension using a flow‐enabled self‐assembly (FESA) strategy to yield large‐area periodic cracks (i.e., microchannels) with tunable spacing. These uniform microchannels can be utilized as a template to guide the assembly of Au nanoparticles, forming intriguing nanoparticle threads. This strategy is simple and convenient. As such, it opens the possibility for large‐scale manufacturing of crack‐based or crack‐derived assemblies and materials for use in optics, electronics, optoelectronics, photonics, magnetic device, nanotechnology, and biotechnology.     

A Chiral Recognition System Orchestrated by Self‐Assembly: Molecular Chirality,Self‐Assembly Morphology,and Fluorescence Response

The newly developed oligophenylenevinylene (OPV)‐based fluorescent (FL) chiral chemosensor (OPV‐Me) for the representative enantiomeric guest, 1,2‐cyclohexanedicarboxylic acid (1,2‐CHDA: RR ‐ and SS ‐form) showed the high chiral discrimination ability, resulting in the different aggregation modes of OPV‐Me self‐assembly: RR ‐CHDA directed the fibrous supramolecular aggregate, whereas SS ‐CHDA directed the finite aggregate. The consequent FL intensity toward RR ‐CHDA was up to 30 times larger than that toward SS ‐CHDA. Accordingly, highly enantioselective recognition was achieved. Application to the chirality sensing was also possible: OPV‐Me exhibited a linear relationship between the FL intensity and the enantiomeric excess through the morphological development of stereocomplex aggregates. These results clearly show that the chiral recognition ability is manifested by the amplification cascade of the chirality difference through self‐assembly.     

Self‐Sorting Double‐Network Hydrogels with Tunable Supramolecular Handedness and Mechanical Properties

Self‐sorting, simultaneous, and orthogonal operations during the self‐assembly of complex mixtures are commonly observed for biological species but rare in artificial systems. In this study, we designed two gelators (LPF and LPFEG) containing the same chiral phenylalanine core but different achiral peripheral substituents to give hydrogels with opposite supramolecular handedness. When the two hydrogels were mixed, double‐network nanofibers with opposite handedness were formed by spontaneous high‐order organization and self‐sorting of the two gelators. The chiroptical activity of the double‐network hydrogels could be tuned by varying the molar ratio of LPF and LPFEG in the mixture, thus showing that the two gelators were highly independent of each other. Enhanced mechanical properties were observed for the interpenetrating networks when the LPF/LPFEG molar ratio was 3:7, with a more than fourfold increase in both the storage (G′) and loss modulus (G′′) relative to those of the individual hydrogels.