Self-Assembly in the Mixtures of Surfactant and Dye Molecule Controlled via Temperature and β‑Cyclodextrin Recognition

A new ternary system of tetradecyldimethylamine oxide (C₁₄DMAO)/4-phenylazo benzoic acid (AzoH)/H₂O was first investigated, and it was found that the self-assembly can be regulated via temperature and β-cyclodextrin (β-CD) recognition. In the temperature regulated self-assembly, the self-assembled phase structural transition between wormlike micelles and multilamellar vesicles (onions) were determined by cryogenic-transmission electron microscopy (cryo-TEM) images and ²H nuclear magnetic resonance (²H NMR) spectra. The phase structural transition temperatures (PSTT) controlled by changing the amount of AzoH were measured by differential scanning calorimetry analysis. The self-assembled phase structural transition mechanism was discussed. It is argued that the self-assembled phase structural transition is the synergetic balance among the hydrophilic headgroup, steric structures of the hydrophobic chain, and membrane charge. β-CD molecules were used as controlling hands to modulate the phase structural transition of self-assembly of the C₁₄DMAO/AzoH/H₂O system in solution via snatching C₁₄DMAO molecules. The phase structural transitions from the threadlike micellar phase to the lamellar phase and from the lamellar phase to the vesicular phase can each be controlled because of the β-CD molecular recognition. The phase structural transitions were confirmed by cryo-TEM observations and ²H NMR measurements. The rheological properties were also investigated to display the importance in the phase structural transition. It was found that the dye molecule, AzoH, is harder to enclose by β-CD than by C₁₄DMAO because of the lower complex stability constant (i.e., <i>K</i>_{C₁₄DMAO@β‑CD} ≫ <i>K</i>_AzoH@β‑CD. Therefore, the phase structural transition is mainly controlled by the inclusion of C₁₄DMAO into the hydrophobic cavity of β-CD molecules. The phase structural transition controlled via temperature and β-CD may find potential applications such as in actuators, shape memories, drug delivery systems, and drag-reducing fluids, etc

Au NP Honeycomb-Patterned Films with Controllable Pore Size and Their Surface-Enhanced Raman Scattering

Honeycomb-patterned films (HPFs) of Au nanoparticles (Au NPs) with pore size controlled by varying the quantity of Au NPs or using modified agents of different mercaptans (C₁₄H₂₉SH, C₁₆H₃₃SH, and C₁₈H₃₇SH) were prepared. The strength of the HPFs containing Au NPs can be enhanced because of the addition of polymers including polystyrene, poly­(l-lactic acid), and poly­(methyl methacrylate-<i>co</i>-ethyl acrylate). With an increase in the amount of polymer and the number of Au NPs or the chain length of the modified agents, the pore size of HPFs decreases, indicating that the pore size can be well controlled by adjusting the above factors. Interestingly, HPFs with elliptical pores that were created by the direction of the air flow were observed. The pore diameter on the outer rim is smaller than that in the center, which should be because of the subordinate evaporation of the solvent in the center. Sponge structures were observed in the cross sections of the walls of HPFs, which should be produced by microphase separation. The HPFs consisting of Au NPs with controllable pore size exhibited stronger surface-enhanced Raman scattering. We believe that the HPFs composed of metal NPs such as Au, Ag, and Cu are exploited in multispectral scanners, nanophotons, and sensors

Phase Structure Transition and Properties of Salt-Free Phosphoric Acid/Non-ionic Surfactants in Water

Precise control of phase structure transition for the synthesis of multi-dimensional soft materials is a fascinating target in amphiphilic molecule self-assembly. Here, we demonstrate a spontaneous formation of a closely packed lamellar phase consisting of uni- and multi-lamellar vesicles through the incorporation of a small amount of an extractant, di­(2-ethylhexyl)­phosphoric acid (DEHPA), into the highly swollen, planar lamellar phase of a non-ionic tetraethylene glycol monododecyl ether (C₁₂EO₄) surfactant in water. It is figured out that the introduction of negative membrane charges results in the electrostatic repulsion among the lamellae, which suppresses the Helfrich undulation and induces a phase structure transition from planar lamellae to closely packed vesicles. Our results provide important insight into amphiphilic molecule self-assembly, where additives and pH can satisfy the opportunities for the precise tuning of the lamellar structures, which makes a way for the development of lamellar soft materials

Artificial Light-Harvesting System with White-Light Emission in a Bicontinuous Ionic Medium

Artificial light-harvesting systems (ALHSs), which are closely related to Förster resonance energy transfer (FRET), are among the most attractive scientific topics during the past few decades. Specifically, binary ALHSs that are composed of a fluid donor and acceptor have a simplified composition and high number density of the donor units. However, largely due to the difficulty in obtaining a fluid donor, investigation of these systems is still quite limited, especially for the ionic systems. Herein, we report a new type of binary ALHS using an ionic naphthalimide (NPI) derivative as a donor, which shows greatly improved photoluminescence for its bicontinuous liquid structure. When blending with an acceptor such as rhodamine 6G or trans-4-[4-(dimethylamino)styryl]-methylpyridinium iodide, efficient FRET was confirmed by both experimental results and molecular dynamics simulations, with an energy transfer efficiency up to ∼90%. Tunable color, including white-light emission, was achieved by tuning the acceptor/donor ratio, opening the door for a variety of applications such as light-emitting diodes and photoluminescent inks

Multiple DNA Architectures with the Participation of Inorganic Metal Ions

Here we develop a synthetic protocol for assembling DNA with participating metal ions into multiple shapes. DNA molecules first form coordination complexes with metal ions and these coordination complexes become nucleation sites for primary crystals of metal inorganic salt, and then elementary units of space-filling architectures based on specific geometry form, and finally elementary units assemble into variously larger multiple architectures according to different spatial configurations. We anticipate that our strategy for self-assembling various custom architectures is applicable to most biomolecules possessing donor atoms that can form coordination complexes with metal ions. These multiple architectures provide a general platform for the engineering and assembly of advanced materials possessing features on the micrometer scale and having novel activity

Free-Standing Monolayer Two-Dimensional Supramolecular Organic Framework with Good Internal Order

Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host–guest enhanced donor–acceptor interaction, consisting of a tris­(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with <i>N</i>-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]­uril as host monomer toward monolayers of an unprecedented 2D SOF. Featuring orthogonal solubility, the participating molecules self-assemble at a liquid–liquid interface, yielding exceptionally large-area, insoluble films, which were analyzed by transmission electron microscopy, atomic force microscopy and optical microscopy to be monolayers with a thickness of 1.8 nm, homogeneously covering areas up to 0.25 cm², and featuring the ability to be free-standing over holes of 10 μm². Characterization with ultraviolet–visible absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, and grazing incidence wide-angle X-ray scattering allowed for confirmation of a successful complexation of all three monomers toward an internal long-range order and gave indications to an expected hexagonal superstructure. Our results extend the existing variety of two-dimensional soft nanomaterials by a versatile supramolecular approach, whereas the possibility of varying the functional monomers is supposed to open adaptability to different applications like membranes, sensors, molecular sieves, and optoelectronics

Understanding the Electron Beam Resilience of Two-Dimensional Conjugated Metal–Organic Frameworks

Knowledge of the atomic structure of layer-stacked two-dimensional conjugated metal–organic frameworks (2D c-MOFs) is an essential prerequisite for establishing their structure–property correlation. For this, atomic resolution imaging is often the method of choice. In this paper, we gain a better understanding of the main properties contributing to the electron beam resilience and the achievable resolution in the high-resolution TEM images of 2D c-MOFs, which include chemical composition, density, and conductivity of the c-MOF structures. As a result, sub-angstrom resolution of 0.95 Å has been achieved for the most stable 2D c-MOF of the considered structures, Cu3(BHT) (BHT = benzenehexathiol), at an accelerating voltage of 80 kV in a spherical and chromatic aberration-corrected TEM. Complex damage mechanisms induced in Cu3(BHT) by the elastic interactions with the e-beam have been explained using detailed ab initio molecular dynamics calculations. Experimental and calculated knock-on damage thresholds are in good agreement

Organic Radical-Assisted Electrochemical Exfoliation for the Scalable Production of High-Quality Graphene

Despite the intensive research efforts devoted to graphene fabrication over the past decade, the production of high-quality graphene on a large scale, at an affordable cost, and in a reproducible manner still represents a great challenge. Here, we report a novel method based on the controlled electrochemical exfoliation of graphite in aqueous ammonium sulfate electrolyte to produce graphene in large quantities and with outstanding quality. Because the radicals (e.g., HO^•) generated from water electrolysis are responsible for defect formation on graphene during electrochemical exfoliation, a series of reducing agents as additives (e.g., (2,2,6,6-tetramethylpiperidin-1-yl)­oxyl (TEMPO), ascorbic acid, and sodium borohydride) have been investigated to eliminate these radicals and thus control the exfoliation process. Remarkably, TEMPO-assisted exfoliation results in large graphene sheets (5–10 μm on average), which exhibit outstanding hole mobilities (∼405 cm² V^–1 s^–1), very low Raman <i>I</i>_D/<i>I</i>_G ratios (below 0.1), and extremely high carbon to oxygen (C/O) ratios (∼25.3). Moreover, the graphene ink prepared in dimethylformamide can exhibit concentrations as high as 6 mg mL^–1, thus qualifying this material for intriguing applications such as transparent conductive films and flexible supercapacitors. In general, this robust method for electrochemical exfoliation of graphite offers great promise for the preparation of graphene that can be utilized in industrial applications to create integrated nanocomposites, conductive or mechanical additives, as well as energy storage and conversion devices

Persulfurated Coronene: A New Generation of “Sulflower”

We report the first synthesis of a persulfurated polycyclic aromatic hydrocarbon (PAH) as a next-generation “sulflower.” In this novel PAH, disulfide units establish an all-sulfur periphery around a coronene core. The structure, electronic properties, and redox behavior were investigated by microscopic, spectroscopic and electrochemical methods and supported by density functional theory. The sulfur-rich character of persulfurated coronene renders it a promising cathode material for lithium–sulfur batteries, displaying a high capacity of 520 mAh g^–1 after 120 cycles at 0.6 C with a high-capacity retention of 90%