Hierarchical Self-assembled Structures Research Articles

Establishing superfine nanofibrils for robust polyelectrolyte artificial spider silk and powerful artificial muscles

Spider silk exhibits an excellent combination of high strength and toughness, which originates from the hierarchical self-assembled structure of spidroin during fiber spinning. In this work, superfine nanofibrils are established in polyelectrolyte artificial spider silk by optimizing the flexibility of polymer chains, which exhibits combination of breaking strength and toughness ranging from 1.83 GPa and 238 MJ m−3 to 0.53 GPa and 700 MJ m−3, respectively. This is achieved by introducing ions to control the dissociation of polymer chains and evaporation-induced self-assembly under external stress. In addition, the artificial spider silk possesses thermally-driven supercontraction ability. This work provides inspiration for the design of high-performance fiber materials.

Red-light-controlled supramolecular assemblies of indigo amphiphiles at multiple length scales

Amphiphilic molecules functionalized with photoresponsive motifs have attractive prospects for applications in smart functional bio-material ranging from cell-material interfaces to drug delivery systems owing to the precisely controllable functionality of self-assembled hierarchical supramolecular structures in aqueous media by a non-invasive light stimulation with high temporal- and spatial-resolution. However, most of reported photoresponsive amphiphiles are triggered by bio-damaging UV-light, which greatly limits the potential in bio-related applications. Herein, we present newly designed red-light controlled N,N’-diaryl-substituted indigo amphiphiles (IA), exhibiting excellent photoswitchablity and photostability with dual red-/green-light in organic media. Meanwhile, aqueous solutions of IA assembled into supramolecular structures in both microscopic and macroscopic length-scale, though the photoresponsiveness of IA is slightly compromised in aqueous media. At macroscopic length-scale, morphological changes of IA macroscopic scaffold prepared by a shear-flow method can be fine adjusted upon red-light irradiation. Moreover, the preferential attachment of live h-MSCs to IA macroscopic scaffold surface also indicates a good biocompatibility of IA macroscopic scaffold. These results provide the potential for developing the next generation of red-light controlled soft functional materials with good biocompatibility.

A novel self-assembled ZIF-67 hollow prisms for high-efficient simultaneous removal of ciprofloxacin and lead

Due to the wide variety of pollutants in wastewater, therefore, how to efficiently and effectively remove mixed pollutants is of great importance for environmental remediation. In this study, ZIF-67 hollow prisms self-assembled by nanoparticles were prepared. The nanoparticles possess a regular distributed pore structure, which mixed with the self-assembled hierarchical structure can provide more binding sites. This special self-assembly structure endows ZIF-67 hollow prisms to have a large specific surface area (1221 m2/g), and to exhibit excellent efficiency in removing a variety of pharmaceuticals. For simultaneous removal of ciprofloxacin and Pb(II) mixed pollutants, the adsorption process of Pb(II) is ultra-fast (<2 min), and the average amount removed efficiently was 100 %. The maximum adsorption capacities of ciprofloxacin (CIP) and Pb(II) were 1586.14 and 2488.14 mg g−1, respectively. The XPS results indicated that Pb(II) may be mixed with Co-OH to form Co-O-Pb during the adsorption process. As well, metal ions are easily complexed with antibiotics, which makes the adsorption performance of CIP and Pb remarkable. This study explored the adsorption capacity by porous materials with self-assembled structures, and provided a novel strategy for the efficient removal of antibiotic/heavy metal complex pollutants from the environment.

A bio-inspired silkworm 3D cocoon-like hierarchical self-assembled structure from π-conjugated natural aromatic amino acids.

The formation of spontaneous 3D self-assembled hierarchical structures from 1D nanofibers is a significant breakthrough in materials science. Overcoming the major challenges associated with developing these 3D structures, such as uncontrolled self-assembly, complex procedures, and machinery, has been a formidable task. However, the current discovery reveals that simple π-system (fluorenyl)-functionalized natural aromatic amino acids, phenylalanine (Fmoc-F) and tyrosine (Fmoc-Y), can form bio-inspired 3D cocoon-like structures. These structures are composed of entangled 1D nanofibers created through supramolecular self-assembly using a straightforward one-step process of solvent casting. The self-assembly process relies on π-π stacking of the fluorenyl (π-system) moieties and intermolecular hydrogen bonding between urethane amide groups. The cocoon-like structures are versatile and independent of concentration, temperature, and humidity, making them suitable for various applications. This discovery has profound implications for materials science and the developed advanced biomaterials, such as Fmoc-F and Fmoc-Y, can serve as flexible foundational components for constructing 3D fiber-based structures.

Turning the morphology and wetting ability of self-assembled hierarchical structures from lignin stearoyl esters

Well-organized and self-assembled structures with hierarchical surface architectures have recently attracted considerable attention due to their potentially wide application range. Herein, remarkable lignin-based petaloid nanoflakes (LPNFs) were formed via the crystallization of polymeric lignin stearoyl esters (LSEs). A solvent exchange self-assembly technique using Tetrahydrofuran (THF) as a solvent in addition to ethanol, acetone, and water as nonsolvents was used to form LPNFs by the crystallization of the stearyl groups in LSEs during evaporation. The grafting level of the stearoyl groups in the LSEs, the difference of the nonsolvent, and the volume ratios of the solvent/nonsolvent during the solvent exchange process predominantly determined the formation of LPNFs via this process. The self-assembled structures could be constructed as spherical particles and as constituted LPNFs structures with well-organized petaloid nanoflakes. By introducing sufficient amounts of LPNFs patterns on the substrates (e.g., glass slide, paper, and wood), the hydrophilic substrates were successfully transformed into superhydrophobic surfaces. Thus, the synthesis of LSEs and the formation of LPNFs with tunable structures offer a new strategy for the derivation and value-added utilization of lignin.

Hierarchical self-assembled structure and frictional response of phthalocyanine molecules

Solid evidence is needed to demonstrate the effect of molecular orientation and structure on the frictional property of boundary lubricants. In this work, the frictional properties of phthalocyanine self-assembled monolayers (SAMs) with face-on (aromatic cores parallel to the substrate) and edge-on (aromatic cores stand on the substrate) orientations have been compared and the in situ structural variation of edge-on SAMs under frictional shear has been revealed by atomic force microscope (AFM). Face-on oriented SAMs show lower adhesion, lower friction, and stronger wear resistance, compared with edge-on oriented SAMs. Hierarchical structures of edge-on oriented SAMs have been revealed by frictional topography, which are consisted of nanoscale columns, micron-scale stripes, and centimeter-scale monolayer. The column structure deforms under increasing load force, leading to a stepwise friction force curve and a transition among three friction states (ordered friction, collapsed friction, and worn friction). The structural deformation depends on both the order degree and anisotropic stiffness of columns. Columns in phthalocyanine SAMs show a larger stiffness when shearing against molecular plane than shearing along the molecular plane. The presented study on the interfacial structure and frictional mechanism promisingly supports the designing of novel boundary lubricants and their application in engineering.

Construction of a novel two-dimensional AgBiO3/BiOBr step-scheme heterojunction for enhanced broad-spectrum photocatalytic performance.

Efficient S-scheme heterojunction photocatalysts were prepared through in situ growth of AgBiO3 on BiOBr. The self-assembled hierarchical structure of AgBiO3/BiOBr was formed from flower-like AgBiO3 and plate-like BiOBr. The optimized AgBiO3/BiOBr heterojunction possessed excellent visible-light photocatalytic degradation efficiency (83%) for ciprofloxacin (CIP) after 120 min, with 1.46- and 4.15-times higher activity than pure AgBiO3 and BiOBr, respectively. Furthermore, the removal ratio of multiple organic pollutants including tetracycline, Rhodamine B, Lanasol Red 5B and methyl orange was also investigated. Environmental interference experiments demonstrated that high pollutant concentrations, low photocatalyst dose and the addition of ions (SO42−, PO43−, HPO42−, H2PO4−) inhibited the photocatalytic activities. Subsequently, a simultaneous degradation experiment showed the competitive actions between CIP and RhB for radicals, decreasing the photocatalytic activity of CIP. Furthermore, trapping and electron spin resonance experiments showed that h+ and ˙O2− played a certain role in the degradation process and that ˙OH acted as assistant.

Ferroelectric phase-transition frustration near a tricritical composition point

Phase transition describes a mutational behavior of matter states at a critical transition temperature or external field. Despite the phase-transition orders are well sorted by classic thermodynamic theory, ambiguous situations interposed between the first- and second-order transitions were exposed one after another. Here, we report discovery of phase-transition frustration near a tricritical composition point in ferroelectric Pb(Zr1-xTix)O3. Our multi-scale transmission electron microscopy characterization reveals a number of geometrically frustrated microstructure features such as self-assembled hierarchical domain structure, degeneracy of mesoscale domain tetragonality and decoupled polarization-strain relationship. Associated with deviation from the classic mean-field theory, dielectric critical exponent anomalies and temperature dependent birefringence data unveil that the frustrated transition order stems from intricate competition of short-range polar orders and their decoupling to long-range lattice deformation. With supports from effective Hamiltonian Monte Carlo simulations, our findings point out a potentially universal mechanism to comprehend the abnormal critical phenomena occurring in phase-transition materials.

Formation of self-assembled hierarchical structure on Zn doped in CuO nanoparticle using a microwave-assisted chemical precipitation approach

In the present work, CuO and Cu1-xZnxO were synthesized with the function of the Zn doping ratio by microwave-assisted chemical precipitation approach. The X-ray diffraction pattern shows that the mono-phase CuO with a mono-clinical structure and no other secondary phase has been observed for the Cu1-xZnxO with different Zn ratio and confirms CuO lattice does not get destroyed by the addition of Zn. The Raman spectra and HR-TEM analysis support the XRD results. The self-assembled hierarchical flower morphology was obtained for the higher doping ratio of Zn. The energy dispersive analysis of X-ray spectrum confirms the presence of Zn in the CuO lattice and the stoichiometry obtained. The optical band gap was found to be 1.78 eV for CuO nanoparticles, and the values are between 1.80 and 2.29 eV for Zn-doped CuO. For higher Zn-doped CuO, optical band splitting was observed due to flower-like morphology. The recombination of an electron–hole was reduced for higher doping ratio nanoparticles. These properties are needed for photocatalytic application.

Hierarchical CeO2@N-C Ultrathin Nanosheets for Efficient Selective Oxidation of Benzylic Alcohols in Water.

A monodisperse CeO2@N-C ultrathin nanosheet self-assembled hierarchical structure (USHR) has been prepared by metal-organic framework template methods. The uniform coating of nitrogen-doped carbon (N-C) layers could play an important role in the adsorption and activation of benzylic alcohol. The unique 3D hierarchical structure self-assembled by ultrathin nanosheets provided enough active sites for the catalytic reaction. Therefore, the CeO2@N-C USHR can afford excellent catalytic performance for selective oxidation of benzylic alcohols in water.

Effect of reactant sequence on the structure and properties of self-assembled TiO2 microspheres with exposed {001} surfaces

Highly exposed {001} surfaces of ITD-TiO2 and IDT-TiO2 microspheres with self-assembled hierarchical structure were prepared by the two-step hydrothermal method. The degradation rate of MO by ITD-TiO2 was 99.0% after UV-light irradiation for 3.0 h.

A self-assembled hierarchical structure to keep the 3D crystal dimensionality inn-butylammonium cation-capped Pb–Sn perovskites

The self-assembled 3D hierarchical structure with an-BA organic capping layer in the Pb–Sn perovskite framework provides the dual advantages of the stability and efficient charge carrier movement, resulting in boosting device performance.

Multifunctional Reversible Self‐Assembled Structures of Cellulose‐Derived Phase‐Change Nanocrystals

Owing to advantageous properties attributed to well-organized structures, multifunctional materials with reversible hierarchical and highly ordered arrangement in solid-state assembled structures have drawn tremendous interest. However, such materials rarely exist. Based on the reversible phase transition of phase-change materials (PCMs), phase-change nanocrystals (C18-UCNCs) are presented herein, which are capable of self-assembling into well-ordered hierarchical structures. C18-UCNCs have a core-shell structure consisting of a cellulose crystalline core that retains the basic structure and a soft shell containing octadecyl chains that allow phase transition. The distinct core-shell structure and phase transition of octadecyl chains allow C18-UCNCs to self-assemble into flaky nano/microstructures. These self-assembled C18-UCNCs exhibit efficient thermal transport and light-to-thermal energy conversion, and thus are promising for thermosensitive imaging. Specifically, flaky self-assembled nano/microstructures with manipulable surface morphology, surface wetting, and optical properties are thermoreversible and show thermally induced self-healing properties. By using phase-change nanocrystals as a novel group of PCMs, reversible self-assembled multifunctional materials can be engineered. This study proposes a promising approach for constructing self-assembled hierarchical structures by using phase-change nanocrystals and thereby significantly expands the application of PCMs.

Constituent Isomerism-Induced Quasicrystal and Frank–Kasper σ Superlattices Based on Nanosized Shape Amphiphiles

Naturally, subtle variations in the chemical structures of constituent molecules may significantly affect their multiscale spatial arrangements, properties, and functions. Deceptively simple spheri...

Accelerated Reaction Rates within Self-Assembled Polymer Nanoreactors with Tunable Hydrophobic Microenvironments.

Performing reactions in the presence of self-assembled hierarchical structures of amphiphilic macromolecules can accelerate reactions while using water as the bulk solvent due to the hydrophobic effect. We leveraged non-covalent interactions to self-assemble filled-polymer micelle nanoreactors (NR) incorporating gold nanoparticle catalysts into various amphiphilic polymer nanostructures with comparable hydrodynamic nanoreactor size and gold concentration in the nanoreactor dispersion. We systematically studied the effect of the hydrophobic co-precipitant on self-assembly and catalytic performance. We observed that co-precipitants that interact with gold are beneficial for improving incorporation efficiency of the gold nanoparticles into the nanocomposite nanoreactor during self-assembly but decrease catalytic performance. Hierarchical assemblies with co-precipitants that leverage noncovalent interactions could enhance catalytic performance. For the co-precipitants that do not interact strongly with gold, the catalytic performance was strongly affected by the hydrophobic microenvironment of the co-precipitant. Specifically, the apparent reaction rate per surface area using castor oil (CO) was over 8-fold greater than polystyrene (750 g/mol, PS 750); the turnover frequency was higher than previously reported self-assembled polymer systems. The increase in apparent catalytic performance could be attributed to differences in reactant solubility rather than differences in mass transfer or intrinsic kinetics; higher reactant solubility enhances apparent reaction rates. Full conversion of 4-nitrophenol was achieved within three minutes for at least 10 sequential reactions demonstrating that the nanoreactors could be used for multiple reactions.

Concentration-Controlled and Phytic Acid-Assisted Synthesis of Self-Assembled LiFePO4 as Cathode Materials for Lithium-Ion Battery

The olivine LiFePO4 with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO4. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5[Formula: see text]M, the obtained LiFePO4 with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1[Formula: see text]mAh/g at 0.1[Formula: see text]C and 112.4[Formula: see text]mAh/g at 10[Formula: see text]C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO4 open up a new prospect for the production of cathode materials for lithium ion batteries.

Imparting Superhydrophobicity with a Hierarchical Block Copolymer Coating.

A robust and transparent silica-like coating that imparts superhydrophobicity to a surface through its hierarchical multilevel self-assembled structure is demonstrated. This approach involves iterative steps of spin-coating, annealing, and etching of polystyrene-block-polydimethylsiloxane block copolymer thin films to form a tailored multilayer nanoscale topographic pattern with a water contact angle up to 155°. A model based on the hierarchical topography is developed to calculate the wetting angle and optimize the superhydrophobicity, in agreement with the experimental trends, and explaining superhydrophobicity arising through the combination of roughness at different lengthscales. Additionally, the mechanical robustness and optically passive properties of the resulting hydrophobic surfaces are demonstrated.

Supramolecular Assembly of a Molecularly Engineered Protein and Polymer.

Programmable assembly of biomolecules is a fast growing research area that aims to emulate nature's elegance in creating numerous hierarchical self-assembled structures, which are responsible for unimaginably difficult biological functions. Protein assembly is a particularly challenging task, owing to their structural diversity, conformational heterogeneity, and high molecular weight. This article reveals the ability of a supramolecular structure-directing unit (SSDU) to regulate the entropically favourable supramolecular assembly of a covalently conjugated protein (bovine serum albumin (BSA)) to produce well-defined protein-decorated micelles with remarkably high thermal stability, suppression of the thermal denaturation of the protein, and retention of enzymatic activity. Furthermore, a SSDU-appended thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) co-assembles with the SSDU-BSA conjugate because, in both cases, assembly was primarily driven by specific molecular recognition between the SSDUs. However, the resulting supramolecular protein-polymer conjugate exhibits distinctly different polymersome structure to that of the micellar particle produced by the protein-SSDU conjugate. In this case, the enzymatic activity can be significantly suppressed above the lower critical solution temperature of supramolecularly conjugated PNIPAM, possibly due to collapse of the de-solvated polymer chains on the protein surface.

Multi nitrogen doped small honeycomb structure: investigation of their on SEM and TEM microscopy dynamic hierarchal self-assembles for high performance anodes lithium ion storage

During the charging process, the arranged-rearranged structures provided a range of lithium ion shuttle channels, including the space between layers and diffusing through the nanosheets, which decreases the diffusion distance of lithium ions remarkably and reduces the irreversible capacity of the battery. Compared to graphene and quantum dot graphene, the dynamic self-assembled structures showed greatly improved battery performance. The capacity of the carbonaceous materials anode was improved to 1800 mAh g−1 after 100 cycles. Moreover, the rate performance of these N-doped nano-graphene showed only slight deteriorations in capacity at charge/discharge currents ranging from 200 mAh to 2500 mAh, which is expected to overcome the problems of low capacity of dynamic lithium ion batteries. Furthermore, the N-doping site of nano-graphene was well defined and the capacity of the anodes relation to hierarchical self-assembled structures was examined systemically.

Thermodynamically versus Kinetically Controlled Self-Assembly of a Naphthalenediimide-Thiophene Derivative: From Crystalline, Fluorescent, n-Type Semiconducting 1D Needles to Nanofibers.

The control over aggregation pathways is a key requirement for present and future technologies, as it can provide access to a variety of sophisticated structures with unique functional properties. In this work, we demonstrate an unprecedented control over the supramolecular self-assembly of a semiconductive material, based on a naphthalenediimide core functionalized with phenyl-thiophene moieties at the imide termini, by trapping the molecules into different arrangements depending on the crystallization conditions. The control of the solvent evaporation rate enables the growth of highly elaborated hierarchical self-assembled structures: either in an energy-minimum thermodynamic state when the solvent is slowly evaporated forming needle-shaped crystals (polymorph α) or in a local energy-minimum state when the solvent is rapidly evaporated leading to the formation of nanofibers (polymorph β). The exceptional persistence of the kinetically trapped β form allowed the study and comparison of its characteristics with that of the stable α form, revealing the importance of molecular aggregation geometry in functional properties. Intriguingly, we found that compared to the thermodynamically stable α phase, characterized by a J-type aggregation, the β phase exhibits (i) an unusual strong blue shift of the emission from the charge-transfer state responsible for the solid-state luminescent enhancement, (ii) a higher work function with a "rigid shift" of the electronic levels, as shown by Kelvin probe force microscopy and cyclic voltammetry measurements, and (iii) a superior field-effect transistor mobility in agreement with an H-type aggregation as indicated by X-ray analysis and theoretical calculations.