Design,synthesis, and self-assembly of optically active perylenetetracarboxylic diimide bearing two peripheral chiral binaphthyl moieties

An optically active perylenetetracarboxylic diimide (PTCDI) bearing two optically active binaphthyl moieties has been designed and synthesized. The self-assembly properties of these novel PTCDI derivatives in DMF/H₂O were systematically investigated by electronic absorption, circular dichroism (CD) spectra, IR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) technique. Observation of CD signal in the whole absorption region of PTCDI chromophore, indicates effective chiral information transfer from the chiral binaphthyl units to the central PTCDI chromophore at molecular level. The intermolecular π–π interaction between PTCDI rings together with the additionally formed hydrogen bonds between the crown ether moieties of (S)-1 and additional water molecules and the chiral discrimination of periphery chiral side chains induces further intensified asymmetrical perturbation of the chiral binaphthyl units to the central PTCDI chromophore during the self-assembly process, resulting in the formation of right-handed helical arrangement of corresponding molecules in a stack of PTCDI chromophores in aggregates. In addition, the formed nanostructures were revealed to show good semiconducting properties.     

Metal oxide nano-particles for improved electrochromic and lithium-ion battery technologies

Hot-wire chemical vapor deposition (HWCVD) has been employed as an economically scalable method for the deposition of crystalline tungsten oxide nano-rods and nano-particles. Under optimal synthesis conditions, only crystalline WO₃ nano-structures with a smallest dimension of ∼10-50 nm are observed with extensive transmission electron microscopy (TEM) analyses. The incorporation of these particles into porous films led to profound advancement in state-of-the-art electrochromic (EC) technologies. HWCVD has also been employed to produce crystalline molybdenum oxide nano-rods, particles and tubes at high density. TEM analyses show that the smallest dimension of these nano-structures is ∼5-30 nm. XRD and Raman analyses reveal that the materials are highly crystalline and consist of Mo, MoO₂ and MoO₃ phases. It is also possible to fabricate large-area porous films containing these MoO_x nano-structures. Furthermore, these films have been tested as the negative electrode in lithium-ion batteries, and a surprisingly high, reversible capacity has been observed.     

Graphene-Quantum-Dots-Induced Centimeter-Sized Growth of Monolayer Organic Crystals for High-Performance Transistors

Monolayer organic crystals have attracted considerable attention due to their extraordinary optoelectronic properties. Solution self-assembly on the surface of water is an effective approach to fabricate monolayer organic crystals. However, due to the difficulties in controlling the spreading of organic solution on the water surface and the weak intermolecular interaction between the organic molecules, large-area growth of monolayer organic crystals remains a great challenge. Here, a graphene quantum dots (GQDs)-induced self-assembly method for centimeter-sized growth of monolayer organic crystals on a GQDs solution surface is reported. The spreading area of the organic solution can be readily controlled by tuning the pH value of the GQDs solution. Meanwhile, the π–π stacking interaction between the GQDs and the organic molecules can effectively reduce the nucleation energy of the organic molecules and afford a cohesive force to bond the crystals, enabling large-area growth of monolayer organic crystals. Using 2,7-didecyl benzothienobenzothiopene (C₁₀-BTBT) as an examples, centimeter-sized monolayer C₁₀-BTBT crystal with uniform molecular packing and crystal orientation is attained. Organic field-effect transistors based on the monolayer C₁₀-BTBT crystals exhibit a high mobility up to 2.6 cm² V⁻¹ s⁻¹, representing the highest mobility value for solution-assembled monolayer organic crystals. This work provides a feasible route for large-scale fabrication of monolayer organic crystals toward high-performance organic devices.     

Fast Self-Assembly Dynamics of a β-Sheet Peptide Soft Material

Peptide-based hydrogels are promising biocompatible materials for wound healing, drug delivery, and tissue engineering applications. The physical properties of these nanostructured materials depend strongly on the morphology of the gel network. However, the self-assembly mechanism of the peptides that leads to a distinct network morphology is still a subject of ongoing debate, since complete assembly pathways have not yet been resolved. To unravel the dynamics of the hierarchical self-assembly process of the model β-sheet forming peptide KFE8 (Ac-FKFEFKFE-NH₂)_, high-speed atomic force microscopy (HS-AFM) in liquid is used. It is demonstrated that a fast-growing network, based on small fibrillar aggregates, is formed at a solid–liquid interface, while in bulk solution, a distinct, more prolonged nanotube network emerges from intermediate helical ribbons. Moreover, the transformation between these morphologies has been visualized. It is expected that this new in situ and in real-time methodology will set the path for the in-depth unravelling of the dynamics of other peptide-based self-assembled soft materials, as well as gaining advanced insights into the formation of fibers involved in protein misfolding diseases.     

Regulation of Released Alkali from Gel Polymer Electrolyte in Quasi-Solid State Zn–Air Battery

Gel polymer electrolyte (GPE) in quasi-solid state Zn–air battery (QSZAB) will release alkali during cycling, resulting in gradual dehydration of GPE, corrosion of Zn electrode, Zn dendrites growth, and therefore inferior performance. Here, hollow Sn microspheres are prepared on Zn substrate by the technique of colloidal self-assembly. The inner surfaces of hollow Sn microspheres are modified by 2-hydroxypropyl-β-cyclodextrin (hollow Sn-inner HPβCD) to regulate the released alkali at GPE|anode interface. The hollow Sn-inner HPβCD can lessen the leakage of released alkali, make stored alkali diffuse back to GPE during the charging process, and mitigate the loss of soluble Zn(OH)₄²⁻ to suppress Zn dendrites growth. Resultantly, GPE in QSZAB with hollow Sn-inner HPβCD exhibits a high retention capacity for alkaline solution. The cell also exhibits a long cyclic lifespan of 127 h due to the effective regulation of released alkali, which outperforms QSZAB without hollow Sn-inner HPβCD by 7.94 times. This work rivets the regulation of released alkali at GPE|anode interface, providing new insight to improve QSZABs’ performance.     

Preparation of belt-like aggregates of a perylene derivative

Perylene 3,4,9,10-tetracarboxylic tetraethyl ester (PTCTEE) was synthesized via an esterification of perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) with ethanol and iodoethane. After the chloroform solution of PTCTEE was mixed with n-hexane the luminescence intensity decreases, indicating the aggregation of the PTCTEE molecules. The characterizations of AFM and TEM showed that PTCTEE could form belt-like aggregates in this mixed solvents. The process of the formation and growth of the belt-like aggregates was tracked using AFM and the relation between the length of the belt-like aggregates and time could be well described using an exponential function. This aggregate growth is a one-dimensional crystallization of the PTCTEE molecules mainly due to the strong π–π stacking ability of perylene cores. The proper interaction between the side chains and solvent also plays an important role in creating one-dimensional aggregates of PTCTEE.     

Growth and characterization of thin films prepared from perfluoro-isopropyl-substituted perfluorophthalocyanines

Vapor deposition of perfluorinated phthalocyanines with bulky perfluorpropyl groups (F₆₄Pc) yielded intensely colored thin films (20-100 nm) despite the large molecular weight. In situ electrical conduction and optical transmission measurements revealed an almost negligible extent of intermolecular electronic coupling. Such quasi-independent character of molecules in solids was confirmed by detailed spectroscopic ellipsometry. The influence of the bulky peripheral groups on the packing in the films and on the electronic and optical properties of the films as well as potential applications of this class of strong electron acceptors are discussed.     

Stable Molecular Diodes Based on π–π Interactions of the Molecular Frontier Orbitals with Graphene Electrodes

In molecular electronics, it is important to control the strength of the molecule–electrode interaction to balance the trade‐off between electronic coupling strength and broadening of the molecular frontier orbitals: too strong coupling results in severe broadening of the molecular orbitals while the molecular orbitals cannot follow the changes in the Fermi levels under applied bias when the coupling is too weak. Here, a platform based on graphene bottom electrodes to which molecules can bind via π–π interactions is reported. These interactions are strong enough to induce electronic function (rectification) while minimizing broadening of the molecular frontier orbitals. Molecular tunnel junctions are fabricated based on self‐assembled monolayers (SAMs) of Fc(CH₂)₁₁X (Fc = ferrocenyl, X = NH₂, Br, or H) on graphene bottom electrodes contacted to eutectic alloy of gallium and indium top electrodes. The Fc units interact more strongly with graphene than the X units resulting in SAMs with the Fc at the bottom of the SAM. The molecular diodes perform well with rectification ratios of 30–40, and they are stable against bias stressing under ambient conditions. Thus, tunnel junctions based on graphene with π–π molecule–electrode coupling are promising platforms to fabricate stable and well‐performing molecular diodes.     

High-Performance Fluorinated Fused-Ring Electron Acceptor with 3D Stacking and Exciton/Charge Transport

A new fluorinated electron acceptor (FINIC) based on 6,6,12,12-tetrakis(3-fluoro-4-hexylphenyl)-indacenobis(dithieno[3,2-b;2′,3′-d]thiophene) as the electron-donating central core and 5,6-difluoro-3-(1,1-dicyanomethylene)-1-indanone as the electron-deficient end groups is rationally designed and synthesized. FINIC shows similar absorption profile in dilute solution to the nonfluorinated analogue INIC. However, compared with INIC, FINIC film shows red-shifted absorption, down-shifted frontier molecular orbital energy levels, enhanced crystallinity, and more ordered molecular packing. Single-crystal structure data show that FINIC molecules pack into closer 3D “network” motif through H-bonding and π–π interaction, while INIC molecules pack into incompact “honeycomb” motif through only π–π stacking. Theoretical calculations reveal that FINIC has stronger electronic coupling and more molecular interactions than INIC. FINIC has higher electron mobilities in both horizontal and vertical directions than INIC. Moreover, FINIC and INIC support efficient 3D exciton transport. PBD-SF/FINIC blend has a larger driving force for exciton splitting, more efficient charge transfer and photoinduced charge generation. Finally, the organic solar cells based on PBD-SF/FINIC blend yield power conversion efficiency of 14.0%, far exceeding that of the PBD-SF/INIC-based devices (5.1%).     

Effect of self-assembly via π-stacking to morphology and crystallinity on tritylated cellulose

A new interaction between assembled tritylated cellulose (6TC) chains was seen when cellulose was selectively substituted at C-6 position. This obtained interaction was concluded to arise from the π–π stacking between the trityl moieties on cellulose backbone and was evident from SEM images as highly orientated structure as well as from XRD diffractogram as sharp reflections giving the average distance between trityl groups on adjacent chains to be 5.6 Å. This was in good correlation with data from the simplified molecular model (~ 6 Å). The effect of DS value and intramolecular hydrogen bonding on the self-assembly ability of trityl cellulose and thereby, on the morphology and crystallinity was also investigated.     

Effects of crystal structures and intermolecular interactions on charge transport properties of organic semiconductors

In this study, the effects of the packing configuration and intermolecular interaction on the transport properties are investigated based on density functional theory. Molecular design from the standpoint of a quantum-chemical view is helpful to engender favorable molecular packing motifs. The transfer integral along the orientation with π–π overlap is much larger than other directions without π–π overlap, and the mobility along this orientation is higher than that along other directions. The intermolecular interaction analyses demonstrate that hydrogen bonds play a crucial role with strong electrostatic interactions in charge transfer. There will be a synergistic relationship when the π–π stacking and intermolecular interaction coexist in the same direction. It turns out that intermolecular interactions are responsible for charge transport, while π–π stacking interactions dominate donor–acceptor transport. Incorporating the understanding of the molecular packing motifs and intermolecular interactions into the design of organic semiconductors can assist in the development of novel materials.     

Halogen Interaction Effects on Chiral Self-Assemblies on Cyclodipeptide Scaffolds Across Hierarchy

How halogenation affects protein or peptide folding and self-assembly hierarchically? This study tries to answer this question by using the halogen bonding mediated self-assemblies on cyclodipeptide scaffolds. Single-functionalized cyclodipeptides (Cyclo-GX) based on para-halogenated phenylalanine in the solid state form homochiral helical nanotubes via consecutive X···O bonds (X = Cl, Br, and I) independent of halogen kinds. In contrast, double-functionalized cyclodipeptides (Cyclo-XX) feature versatile self-assembly architectures depending on the para-substituents (X = H, F, Cl, Br, and I), affording nanotubular, lamellar, and triple helical nanotubular architectures. Cyclo-BrBr exclusively adopts intramolecular Type-IV X···X interaction that alters the molecular folding and packing, which also gives rise to opposite chirality at molecular folding (secondary structure), stacking (tertiary structure), and self-assembled nanohelices (quarternary structure) at macroscopic scale. It unveils how halogenation impacts on the self-assembly and chirality at hierarchical levels in specific peptides. Clusteroluminescence is found for the cyclodipeptides, achieving high quantum yield up to 71%, whereby circularly polarized luminescence is realized with tunable handedness by controlling halogen substituents.     

Poly-para-phenylene-ethynylene assemblies for a potential molecular nanowire: an SFM study

The self-assembly of a poly-para-phenylene-ethynylene (PPE) derivative cast onto muscovite mica is investigated by Tapping Mode Scanning Force Microscopy. The film morphology depends on the concentration of the PPE in the casting solution. At high concentration a grain morphology with some linear aggregates is observed. At low concentration PPE self-assembles into well defined and stable needles with a cross section with molecular dimensions. A model for the packing of the molecules in these supramolecular structures is suggested. Properly functionalised needles exhibit the molecular architecture of a molecular nanowire ready to be interfaced by metallic nanoelectrodes.     

A new soft template-oriented method for the preparation of hollow analcime microspheres with nanosheets-assembled shells

This paper highlights a controlled synthesis of two-dimensional analcime nanosheets templated by organic additives and an impressive strategy that hollow hierarchical analcime microspheres with layered shells can be assembled by taking advantage of the intrinsic growth law of material. Specifically, ultrathin analcime nanosheets were initially obtained by precisely manipulating the amounts of cetyltrimethylammonium cation (CTA⁺) and ethylenediaminetetraacetate (EDTA^4?) in the synthesis system. As building blocks, these nanosheets then self-assembled layer by layer from outside to inside driven by the reversed crystal growth mechanism of analcime, resulting in a hollow structure with lamellar shells and enhanced specific surface area of 722.3 m² g^?1. Series of experiments were carried out in order to explore the influence of CTA⁺ and EDTA^4? on the formation of analcime nanosheets. The results indicated that CTA⁺ was the micro-mesoporogen of hierarchical analcime and synergistically collaborated with EDTA^4? in directing analcime nanosheets. The effect of hydrothermal temperature was discussed and a surfactant packing parameter (g = V/a ₀ l) was cited to explain the behavior of organics. In addition, the investigation of hydrothermal process clearly revealed the crystallization and self-assembly process of hollow structure. And the UV Raman results unraveled that four-membered rings (4MRs) as the active building units for analcime framework were firstly formed in the synthesis gel, followed by reconstruction and self-assembly which lead to the formation of 6MRs and 8MRs.     

Noncovalent complexes of Ih−C80 fullerene with phthalocyanines

The noncovalent interactions of I_h?C₈₀ fullerene with free-base and 3d transition M(II) phthalocyanines (where M = Mn, Fe, Co, Ni, Cu, Zn) were studied at the PBE-D/DNP level of density functional theory. The optimized complex geometries, formation energies and electronic parameters were analyzed and compared to those reported previously for similar dyads with C₆₀. In the complexes with I_h?C₈₀, the central metal atom (as well as one H atom of H₂Pc) is always coordinated to a C_6:6:6 atom of C₈₀ cage, exhibiting only one general interaction pattern. The shortest M^…C_C80 and N^…C_C80 distances are notably longer than in dyads with C_60, and the distortion of Pc macrocycle is less significant. In none of C₈₀-based dyads the formation of new coordination bonds by metal atoms was observed. The bonding strength for Pc–C₈₀ dyads varies approximately to the same degree of 20 kcal/mol as for their Pc–C₆₀ analogues, however negative formation energies for Pc–C₈₀ dyads are on average by 5–6 kcal/mol lower than for their C₆₀ analogues. While in closed-shell Pc–fullerene systems HOMO is usually found totally on Pc molecule, in the case of C₈₀-based dyads only a minor HOMO fraction can be detected for some dyads on Pc, with the major one always distributed over fullerene cage. As a result, the calculated HOMO-LUMO gap energies turn to be very low, around 0.1 eV. Analysis of spin density plots revealed that H₂Pc+C₈₀, NiPc+C₈₀ and ZnPc+C₈₀ dyads behave as closed-shell systems, like similar noncovalent complexes of Pcs with C₆₀.     

Preparation of a self-assembled cytochrome c monolayer on a gold substrate for biomolecular device architecture

The segregation ability of 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS), a zwitterionic surfactant, on cytochrome c (cyt c) aggregates in a phosphate buffer solution was quantified through the dynamic light-scattering analysis, and CHAPS was found to have an excellent ability in reducing nonspecific affinity among cyt c molecules. When CHAPS was applied to cyt c aggregates on the surface of gold substrates modified with self-assembled cyt c monolayer, the aggregates were found to be successfully eliminated by high-resolution atomic force microscopy image with 30-nm-sized cyt c clusters. This technique is expected to be useful to prepare a self-assembled monolayer of metalloproteins without their aggregates which may degrade the electrochemical property required as a biomolecular electronic device.     

Hierarchical self-assembly of a collagen mimetic peptide (PKG)n(POG)2n(DOG)n via electrostatic interactions

A new type of collagen mimetic peptide, (PKG)_n(POG)_2n(DOG)_n, with charged-domain ends had been designed and successfully prepared in this work, which self-assembled into collagen-like triple helices homotrimers. The collagen-like homotrimers underwent higher level of self-assembly via static electrical interaction between positive and negative domains. Transmission electron microscope (TEM) examinations showed three typical morphologies of homotrimer assembly, which were defined as film, bicontinuous and fibril morphology in this paper. The film was formed in the initial stage and gradually transformed to bicontinuous or fibril morphology to improve stability of the assemblies or decrease surface energy. Furthermore, mechanism of assembly process was proposed based on TEM observations and theoretical analyses of packing equation.     

pH-dependent photochromism of self-assembled multilayer films from polymolybdates

Polymolybdate/1, 10-decanediamine self-assembled films were fabricated by self-assembly of 1, 10-decanediamine and Na₂MoO₄ solutions with different pH values. It is found that the photochromic responses of the films increase with decreased pH value of the Na₂MoO₄ solution. It is identified that the pH value can affect greatly the species of polyanion inorganic building blocks in the Na₂MoO₄ solution, thus resulting in the polymolybdate/1, 10-decanediamine self-assembled films with different structure and photochromic properties.     

Facile synthesis,magnetic and optical properties of double-shelled Co3O4 hollow microspheres

Double-shelled Co₃O₄ hollow spheres are successfully synthesized by chemically induced self-assembly in the hydrothermal environment. The morphology, chemical composition, and crystalline structure of the double-shelled Co₃O₄ hollow spheres are characterized by different techniques, such as powder X-ray diffraction (PXRD), Raman spectrum, X-ray photoelectron spectrum (XPS), field emission scanning electron microscope (FESEM), and high resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). Magnetic measurements and optical spectra suggest the double-shelled Co₃O₄ hollow spheres exhibit close to a weak ferromagnetic behaviour and enhanced photogenerated carrier separation. Since this synthetic route is simple, convenient, and “green”, it is possible to extend this synthetic method to preparation of a wide range of the multishelled hollow spheres of metal oxides for semiconductor device applications.