We report a unique category of π‐extended diaza7helicenes with double negative curvatures. This is achieved by two‐fold regioselective heptagonal cyclization of the oligoarylene‐carbazole precursors ...through either intramolecular C−H arylation or Scholl reaction. The fusion of two heptagonal rings in the helical skeleton dramatically increases the intramolecular strain and forces the two terminal carbazole moieties to stack in a compressed fashion. The presence of the deformable negatively curved heptagonal rings endows the resulting diaza7helicenes with dynamic chiral skeletons, aggregation‐induced emission feature and relatively low racemization barrier of ca. 25.6 kcal mol−1. Further π‐extension on the carbazole moieties subsequently leads to a more sophisticated C2‐symmetric homochiral triple helicene. Notably, these π‐extended diaza7helicenes show structure‐dependent stacking upon crystallization, switching from heterochiral packing to intra‐layer homochiral stacking. Interestingly, the C2‐symmetric triple helicene molecules spontaneously resolve into a homochiral lamellar structure with 31 helix symmetry. Upon ultrasonication in a nonsolvent, the crystals can be readily exfoliated into large‐area ultrathin nanosheets with height of ca. 4.4 nm corresponding to two layers of stacked triple helicene molecules and relatively thicker nanosheets constituted by even‐numbered molecular lamellae. Moreover, regular hexagonal thin platelets with size larger than 30 μm can be readily fabricated by flash aggregation.
Curved nanographenes (NGs) are emerging as promising candidates for organic optoelectronics, supramolecular materials, and biological applications. Here we report a distinctive type of curved NGs ...bearing a 1,4diazocine core that is fused with four pentagonal rings. This is formed by Scholl-type cyclization of two adjacent carbazole moieties through an unusual diradical cation mechanism followed by C–H arylation. Owing to the strain in the unique 5–5–8–5–5-membered ring skeleton, the resulting NG adopts an interesting concave–convex cooperatively dynamic structure. By peripheral π-extension, a helicene moiety with fixed helical chirality can be further mounted to modulate the vibration of the concave–convex structure, through which the distant bay region of the curved NG inherits the chirality of the helicene moiety in a reversed fashion. The 1,4diazocine-embedded NGs show typical electron-rich characteristics and form charge transfer complexes with tunable emissions with a series of electron acceptors. The relatively protruding armchair edge also allows the fusion of three NGs into a C 2 symmetric triple diaza7helicene which reveals a subtle balance of fixed and dynamic chirality.
Colloidal composites, translating the great potential of nanoscale building bricks into macroscopic dimensions, have emerged as an appealing candidate for new materials with applications in optics, ...energy storage, and biomedicines. However, it remains a key challenge to bridge the size regimes from nanoscopic colloidal particles to macroscale composites possessing mechanical robustness. Herein, a bottom-up approach is demonstrated to manufacture colloidal composites with customized macroscopic forms by virtue of the co-assembly of nanosized soft polymeric micelles and hard inorganic nanoparticles. Upon association, the hairy micellar corona can bind with the hard nanoparticles, linking individual hard constituents together in a soft-hard alternating manner to form a collective entity. This permits the integration of block copolymer micelles with controlled amounts of hard nanoparticles into macroscopic colloidal composites featuring diverse internal microstructures. The resultant composites showed tunable microscale mechanical strength in a range of 90-270 MPa and macroscale mechanical strength in a range of 7-42 MPa for compression and 2-24 MPa for bending. Notably, the incorporation of soft polymeric micelles also imparts time- and temperature-dependent dynamic deformability and versatile capacity to the resulting composites, allowing their application in the low-temperature plastic processing for functional fused silica glass.
The design and fabrication of chiral nanostructures is a promising approach to realize enantiomeric recognition and separation. In our work, gold nanorod@chiral mesoporous silica core–shell ...nanoparticles (GNR@CMS NPs) have been successfully synthesized. This novel material exhibits strong and tunable circular dichroism signals in the visible and near-infrared regions due to the optical coupling between the CMS shells and the GNR cores. When chiral cysteine molecules are loaded in the porous shells, the corresponding surface enhanced Raman scattering spectroscopy demonstrates a distinct chiral recognition effect, which can be used to semiquantitatively measure the composition of chiral enantiomers. A detailed sensing mechanism has been disclosed by density functional theory calculations.
The effects of synthesis conditions including the co-structure directing agent (CSDA)/amphiphile molar ratio, reaction temperature, and pH value on the pitch length of the helical mesoporous silicas ...(HMSs) have been comprehensively investigated. It has been found that the external diameter of the HMS rod increased with increasing CSDA/amphiphile molar ratio, reaction temperature, and pH value, while the pitch length increased linearly with increasing diameter of the HMS rod in a settled condition. The driving force for the formation of HMS has been considered to be the 2d-hexagonally-ordered propeller-like micelles with moment
M
0 which can be related to the pitch length (
p) and diameter (
d) of the micelle (
M
0
∝
d
p
). The shorter pitch length of the micelle would give rise to a strong moment for the hexagonally-stacked rods in the same micelle diameter, and vice versa with a longer pitch length. It was shown that the moment of the propeller-like micelle was not significantly changed by varying the TMAPS/SDS molar ratio or the pH value, but obviously affected by the reaction temperature.
The creation of nanostructures with precise chemistries on material surfaces is of importance in a wide variety of areas such as lithography, superhydrophobicity, and cell adhesion. We describe a ...platform for surface functionalization that involves the fabrication of cylindrical micellar brushes on a silicon wafer through seeded growth of crystallizable block copolymers at the termini of immobilized, surface-confined crystallite seeds. The density, length, and coronal chemistry of the micellar brushes can be precisely tuned, and post-growth decoration with nanoparticles enables applications in catalysis and antibacterial surface modification. The micellar brushes can also be grown on ultrathin two-dimensional materials such as graphene oxide nanosheets and further assembled into a membrane for the separation of oil-in-water emulsions and gold nanoparticles.
<正>Life is an extremely delicate self-assembly system,where a rich array of small molecules,macromolecules and other entities associate and organize in an intrinsically diverse and precise ...manner.During the past few decades,scientists have
Flow reactors are appealing alternatives to conventional batch reactors for heterogeneous catalysis. However, it remains a key challenge to firmly immobilize the catalysts in a facile and flexible ...manner and to simultaneously maintain a high catalytic efficiency and throughput. Herein, we introduce a dense cylindrical micelle brush support in glass capillary flow reactors through a living crystallization‐driven self‐assembly process initiated by pre‐immobilized short micelle seeds. The active hairy corona of these micellar brushes allows the flexible decoration of a diverse array of nanocatalysts, either through a direct capture process or an in situ growth method. The resulting flow reactors reveal excellent catalytic efficiency for a broad range of frequently utilized transformations, including organic reductions, Suzuki couplings, photolytic degradations, and multistep cascade reactions, and the system was both recyclable and durable. Significantly, this approach is readily applicable to long capillaries, which enables the construction of flow reactors with remarkably higher throughput.
Forest‐like micellar brushes fabricated under an ambient environment in glass capillaries enable flexible decoration of various nanocatalysts and subsequently permit a broad range of continuous flow transformations. Notably, this strategy is feasible for short and long capillaries, allowing the preparation of flow reactors with significantly higher throughput.
Symmetry breaking is prevalent in nature and provides distinctive access to hierarchical structures for artificial materials. However, it is rarely explored in two-dimensional (2D) entities, ...especially for lateral asymmetry. Herein, we describe a unique symmetry breaking process in surface-initiated 2D living crystallization-driven self-assembly. The 2D epitaxial growth occurs only at one lateral side of the immobilized cylindrical micelle seeds, accessing unilateral platelets with the yield increasing with the seed length, the growth temperature, and poly(2-vinylpyridine) corona length (maximum = 92%). Generally, the tilted immobilization of seeds blocks one lateral side and triggers the lateral symmetry breaking, where the intensity and spatial arrangement of seed–surface interactions dictate the regulation. Segmented unilateral platelets with segmented corona regions are further fabricated with the addition of different blended unimers. Remarkably, discrete slope-like and dense blade-like platelet arrays grow off the surface when seeds are compactly aligned either with spherical micelles or themselves. This strategy provides nanoscale insights into the symmetry breaking in long-range self-assembly and would be promising for the design of innovative colloids and smart surfaces.
![[1,4]Diazocine-Embedded Ele...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0002-7863/small "[1,4]Diazocine-Embedded Electron-Rich Nanographenes with Cooperatively Dynamic Skeletons")
