Molecular Self-assembly Method Research Articles

A novel ADN/TANPDO supramolecular crystal with anti-hygroscopicity and high energy: A promising strategy to construct advanced propellant materials

Herein, encapsulating NH4+ ions through molecular self-assembly method has been employed to reduce the strong hygroscopicity of ADN (ammonium dinitramide). A novel ADN/TANPDO (2,4,6-triamino-5-nitropyrimidine-1,3-dioxide) supramolecular crystal with a 3:2 ratio was obtained using a rapid, green, efficient, and scalable self-assembly method. Compared with pure ADN, ADN/TANPDO supramolecular crystal exhibits a significantly lower hygroscopicity rate of 2.76 % (25 °C and 75 % relative humidity) and a lower impact sensitivity of 15 J, as well as a markedly higher specific impulse of 236 s. Additionally, the propellant formulation based on ADN/TANPDO supramolecular crystal presents high predicted energy with decreased content of HCl gas, making it a promising candidate for a high-energy and low-characteristic signal propellant component. Furthermore, this work offers a promising strategy to construct supramolecular crystals for solving the strong hygroscopicity of ADN and simultaneously assemble oxidizers with high-energy materials together at the molecular scale to achieve advanced propellant materials in the future.

Achieving stable zinc metal anode by eliminating the surface heterogeneity

Aqueous zinc-ion batteries (AZIBs) are regarded as one of the promising alternatives for lithium-ion batteries in large-scale energy storage systems. However, the further development of AZIBs is limited by the challenges related to the heterogeneity of zinc anode, which arises from the harmful micro-regions and the accumulation of corrosion products. We employ a simple and effective molecular self-assembly method to modify the anode with a homogeneous (Octadecanethiol) ODT molecular layer through the combination of zinc and sulfhydryl (-SH) groups. The molecular-scale modification method can precisely repair the harmful micro-regions and ensure the homogeneity of the surface. In addition, the hydrophobic alkyl chains of the ODT molecules inhibit the corrosion reaction, thus avoiding the enhancement of heterogeneity due to the accumulation of corrosion products. Theoretical calculations and simulations show that this homogeneous molecular layer effectively eliminates the surface heterogeneity and thus has a profound impact on the deposition process. Benefiting from above, all the ODT-Zn symmetrical batteries can cycle at 5 mA cm−2 for more than 1000 h. The full battery using MnO2 cathode can cycle for more than 1000 times with a capacity retention rate is 90 %.

Fabrication, characterization, and application of pea protein isolate-polyphenol-iron complexes with antioxidant and antibacterial activity

Plant proteins are becoming increasingly popular as functional ingredients in foods because of their health, sustainability, and environmental benefits. The functional performance of plant proteins can often be improved by combining them with other food ingredients. For instance, they can be combined with polyphenols and metal ions to form surface active protein-polyphenol-iron complexes with biological activity. In this study, ternary complexes of pea protein isolate (PPI), epigallocatechin-3-gallate (EGCG) and iron (Fe3+) was prepared using a simple molecular self-assembly method. The formation mechanism, characteristics, and functional properties of these complexes were then characterized. Our results showed that PPI, EGCG, and Fe3+ could spontaneously combine to form nano-sheet networks held together by hydrogen bonds, phenolic hydroxyl coordination bonds, and electrostatic interactions. The addition of Fe3+ increased the fraction of disordered secondary structures, reduced the thermal denaturation temperature, reduced the surface hydrophobicity, increased the particle size, and altered the surface potential of the proteins in a dose dependent manner. Optimizing the EGCG-to-Fe3+ ratio in the complexes (1:2 w/w) led to the formation of protein composites with improved surface, antioxidant, and antibacterial activities. This study provided valuable insights into the interaction mechanisms of proteins, polyphenols, and metal ions in ternary complexes. These complexes may be used as multifunctional ingredients in plant-based foods because of their beneficial antioxidant, antimicrobial, nutritional, and emulsification properties.

Self-assembly method for two-dimensional mesoporous materials: a review for recent progress

Two-dimensional mesoporous materials (2DMMs) refer to thin two-dimensional (2D) nanosheets with randomly dispersed or ordered mesopores, which can combine the advantages of 2D materials and mesoporous materials while overcoming their inherent drawbacks, leading to enhanced application performance. A self-assembly strategy has been recognized as a promising manufacturing method for 2DMMs with customized performance. Over the past decades, encouraging progress has been made in the development of 2DMMs via the self-assembly strategy with a variety of compositions, morphologies, mesoporous structures, and pore sizes. Here, we provide a comprehensive review on recent progress in the fabrication of 2DMMs through this strategy, focusing on the synthesis methods, including molecular self-assembly methods, single micelle assembly methods, multi-templates methods, surface-limited co-assembly methods, and template-free methods. In addition, we set out the challenges faced by 2DMMs in future research and point out potential development directions.

Fabrication and characterization of the H/J-type aggregates astaxanthin/bovine serum albumin/chitosan nanoparticles

Astaxanthin is a natural liposoluble ketocarotenoid with various biological activities. Hydrophobic astaxanthin with C2h symmetry can self-assembly form H-type aggregates and J-type aggregates in hydrated polar solvents. However, astaxanthin and its aggregates are limited by its water insolubility and chemical instability. Here, the biological macromolecules bovine serum albumin (BSA) and chitosan were chosen as protein-polysaccharides based delivery systems for astaxanthin aggregates by molecular self-assembly method. The precise prepared H-ABC-NPs and J-ABC-NPs suspensions were both near spheres with hydrodynamic size around 281 ± 9 nm and 368 ± 5 nm and zeta potentials around +26 mV and +30 mV, respectively. Two types of astaxanthin aggregates were distinguished, water-dispersible, and stable in nanocarriers through UV–vis spectra observation. The encapsulation efficiency of the astaxanthin in ABC-NPs was above 90 %. Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) analyses indicated that the dominant driving forces of ABC-NPs formation mainly included electrostatic, hydrophobic interactions and hydrogen bonding. These results offer an elegant opportunity for the protein-polysaccharides delivery systems, and provide an important perspective for applying novel water-dispersed astaxanthin aggregates products in nutrition and medicine industry.

Mesoporous hydroxyapatite: Synthesis in molecular self-assembly and adsorption properties

A kind of mesoporous hydroxyapatite (HA) with high ordered structure was first synthesized in molecular self-assembly method. In this study, HA nanoparticles with an average diameter of about 12 nm were dissociated into HA molecules in a weak acidic buffer solution (NaH2PO4–Na2HPO4, PBS), and the molecules were assembled to form a HA polymerized framework on the surface of the micelles constructed by cetyltrimethylammonium bromide (CTAB, a template) under hydrothermal treatment. The mesoporous structure was finally formed by calcination to remove the template. High-resolution transmission electron microscopy (HRTEM) observed that there were regular and ordered channels in the mesoporous HA. The nitrogen sorption results of mesoporous HA indicated the specific surface area, total pore volume and maximum pore size distribution of mesoporous HA were 48.81 m2/g, 0.38 cm3/g and 1.93 nm, respectively. The porous material was found to have high adsorption capacities to some metal ions, such as Co2+ (299.46 mg/g), Ni2+ (309.35 mg/g), Cu2+ (248.03 mg/g), Zn2+ (276.11 mg/g) and Cd2+ (192.93 mg/g), and ion exchange and recrystallization of the metal salts were found to occur on the mesoporous material to give high adsorption capacities. The efficient and environment-friendly characteristics of materials open the doors for potential usage in real industrial processes.

Porous Hollow Carbon Aerogel-Assembled Core@Polypyrrole Nanoparticle Shell as an Efficient Sulfur Host through a Tunable Molecular Self-Assembly Method for Rechargeable Lithium/Sulfur Batteries

Lithium-sulfur (Li-S) batteries have fascinated as next-generation high specific energy density storing devices. Herein, we report the fabrication of a three-dimensional porous hollow core@shell st...

Synthesis of porous few-layer carbon nitride with excellent photocatalytic nitrogen fixation

The porous few-layer g-C3N4 (PFL-g-C3N4) is prepared by a simple molecular self-assembly method. Compared with pure g-C3N4, the as-prepared PFL-g-C3N4 is ultrathin, the surface is rich in pores, and the photocatalytic nitrogen fixation activity is greatly increased to 8.20 mM h−1 gCat−1. Few-layer and ultrathin nature of PFL-g-C3N4 can provide a larger specific surface area, expose more active sites, and reduce the diffusion path of charges and protons from the inside to the surface. In addition, the porous structure can narrow the band gap, thereby increasing the light absorption range and enhancing the light absorption capability. Meanwhile, the presence of nitrogen vacancies causes PFL-g-C3N4 to move to a more negative conductive band value. More importantly, the isotopic experiments using 15N2 as nitrogen source confirm the ammonia production originating from N2 rather than the decomposition of g-C3N4. Therefore, PFL-g-C3N4 can greatly improve the efficiency of visible light photocatalytic nitrogen fixation.

Feasibility Study of Tissue Transglutaminase for Self-Catalytic Cross-Linking of Self-Assembled Collagen Fibril Hydrogel and Its Promising Application in Wound Healing Promotion.

Collagen-based bio-hydrogels are undoubtedly a hot spot in the development of biological dressings for wound healing promotion. Herein, glutamine transaminase (TGase), a biological nontoxic cross-linker with high specific activity and reaction rate under mild conditions, was utilized for the self-catalytic cross-linking of the regenerated collagen (COL) fibril hydrogel fabricated through a molecular self-assembly method. The results showed that the natural triple helical conformation of COL remained completely integrated after self-catalytic cross-linking TGase, which was definitively the fundamental for maintaining its superior bioactivity. It was worth noting that TGase could promote the self-assembly process of COL building blocks into a higher order D-period cross-striated structure. Also, the reconstructed TGase cross-linked COL fibrils exhibited a higher degree of interfiber entanglements with more straight and longer fibrils. Meanwhile, the thermal stability of COL was significantly improved after introducing TGase. Besides, the cytocompatibility analysis suggested that the regenerated COL fibril hydrogel showed excellent cell growth activity and proliferation ability when the dosage of TGase is less than 40 U/g. Further, animal experiments indicated that the targeted COL fibril hydrogel could significantly promote skin wound healing, exhibiting better capacity of skin tissue for regeneration than the COL hydrogel untreated as expected. Therefore, the reconstructed TGase cross-linked COL fibril hydrogel could serve as a novel soft material for wound healing promotion.

To pursue FexCoy-PANI/CNT catalysts for oxygen reduction reaction in acid medium with controlled molecular self-assembly method

The mainstream of pyrolyzed transitional metal-nitrogen-carbon (M-N-C) catalysts for ORR still confront difficulty in PEMFC application. To pursue M-N-C structure from wet chemistry at ambient temperature, this paper prepares FexCoy-PANI/CNT porous structures composed of amorphous Fe and Co NPs into PANI layer on CNT surface, supported by the controlled molecular self-assembly mechanism (MS). For their ORR behaviors in acid medium, all FexCoy-PANI/CNT catalysts demonstrate similar features as Pt-based catalyst in low current density region, and 4e pathway and active sites in pore utilization in high current density region. Specifically, we disclosed nitrogen in PANI matrix dominates specific activity for ORR, and a little transitional metal attain mass activity at maximum. The active sites mounted into PANI matrix and 4e pathway help catalysts to achieve high durability. Thus, we extend a new type of platinum-free catalyst and develop a bottom-up approach for preparation-structure-activity, expecting to drive PEMFC remarkably.

Oxygen reduction reaction of Fe-Polyaniline/Carbon Nanotube and Pt/C catalysts in alkali media

To drive the Fe-based application for the Oxygen Reduction Reaction (ORR) in alkali media, this work found the Carbon Nanotube supported Fe-Polyaniline (Fe-PANI/CNT) catalyst from controlled Molecular Self-assembly (MS) method is comparable to the commercial Pt/C catalyst in mass current density and ORR stability, but with large gap on specific current density. This can be due to that the controlled MS method help establish the most active site of Fe-N coordination in the PANI pore, whose hydrophilic state inhibits O2 transfer and whose poor conductivity restricts O2 utilization jointly. In the meanwhile, we revealed that the enormous impact of OH adsorption (OHad) on ORR activity and stability, exhibiting negative results on the Pt/C catalyst but beneficial results for Fe-based catalysts, especially in the “indirect 2e+2e pathway” relating to the inner and outer-sphere electron transfer processes. All these progress facilitate the clarification for the structure-catalysis and encourage preparation towards controlled MS methods.

Aptamer-Modified Gold Nanochannels Membrane for Separation of β-Estradiol and Estrone

Abstract In the present work, a new method for the separation of β-estradiol and estrone by the modified gold nanochannels membrane was described. The gold nanochannels were prepared by chemical deposition of gold on polycarbonate templates membrane. The morphology of the nanochannels, characterized by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM), showed that smooth and uniform Au nanochannels were produced. After being modified with aptamer on the nanochannels membranes using a molecular self-assembly method, the nanochannels membranes facilitated the transport of β-estradiol through the membranes while the estrone was not easy to permeate. The transport behaviours of β-estradiol and estrone through the gold nanochannels modified with aptamer of β-estradiol were investigated. The results showed that the nanochannels membrane modified with β-estradiol aptamer could be used to separate β-estradiol and estrone on the basis of unique selectivity. A separation efficiency of 1.75 was obtained when the nanochannels had a pore size of 20 nm in the medium pH from 6.0 to 8.0.

Fabrication of magnetic silica-pillared clay (SPC) nanocomposites with ordered interlayer mesoporous structure for controlled drug release

Magnetic silica-pillared clay with ordered layered structure and uniform gallery pore size distribution were synthesized by generating magnetic Fe3O4 nanoparticles onto the mesoporous silica-pillared clay hosts using molecular self-assembly method. The obtained magnetic silica-pillared clay samples have been characterized by elemental analysis (XRF), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption isotherms, Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectrometer (XPS) and transmission electron microscopy (TEM). Such results indicate that the formed magnetic silica-pillared clay keeps the ordered layered structure and uniform gallery pore size, and the magnetic nanoparticles generated onto the silica-pillared clay host is mainly composed of Fe3O4. Magnetic measurements reveal that these composites possess super paramagnetic properties at 300K, and the saturation magnetization increases with increasing Fe ratio loaded. These magnetic silica-pillared clays show sustained release profiles with acetylsalicylic acid as the model drug. The magnetic silica-pillared clay samples show higher release rate with respect to the general silica-pillared clay.

Assembled 3D cell niches in chitosan hydrogel network to mimic extracellular matrix

Extracellular matrix (ECM) is a composite material which contains a complex mixture of fibrous proteins and heteropolysaccharides, providing an important model for designing biomaterials. To mimic ECM, we fabricated 3D cell niches in chitosan hydrogel network via the layer-by-layer (LbL) molecular self-assembly method. Compression modulus of genipin-crosslinked chitosan hydrogel could be regulated from 0.014±0.003MPa to 0.24±0.009MPa as chitosan concentration increased from 1wt.% to 5wt.%, which reached the requirements of soft tissue. The 10μm CaCO3 microparticles as porogens were embedded into hydrogel network to resemble in vivo 3D microstructure. Porosity could be modulated from 32.10±5.08% to 91.41±6.56% as more CaCO3 microparticles embedded. The ECM component of chondroitin sulfate (CS) was layer-by-layer assembled into hydrogel network via electrostatic interactions between negative-charged CS molecules and positive-charged chitosan molecules. Subsequently, the process of delivering fibroblast growth factor (FGF) in hydrogel network could be precisely controlled due to CS molecules’ affinity interactions with FGF. In vitro 3D cell culture experiments revealed that human lung fibroblast (HLF) grew better in the scaffolds as fabricated than that in untreated chitosan hydrogel. These results suggest adaptive 3D cell niches can be fabricated through molecular self-assembly of the ECM components for engineering the aimed tissues.

Molecularly Imprinted Electrospinning Polyethersulfone Nano-Scale Fibers for the Binding and Recognition of Bisphenol A

Molecularly imprinted polyethersulfone (PES) nano-scale fibers were prepared by using electrospinning technique, and then used for the recognition and binding of endocrine disrupter bisphenol A (BPA) from aqueous solutions. As an alternative to synthesizing molecularly imprinted nanofibers using ‘template-guided’ or molecular self-assembly method, the route has proven to be one of simplicity and convenience. The imprinted PES nano-scale fibers with the diameter ranged from 200 nm to 500 nm could be easily used for the binding and recognition of BPA as that by using PES microfibers and particles, and the nano-scale fibers showed good performance for specific recognition of BPA. Significantly higher binding amount and speed were observed compared to the imprinted PES particles and microfibers.

Self-Assembly of Ionic Liquids and Metal Complexes in Super-Cages of NaY: Integration of Free Catalysts and Solvent Molecules into Confined Catalytic Sites

The integration of a free metal complex, Pd(phen) 2+ , and a room temperature ionic liquid (IL) solvent molecule, 1-decyl-3-methyl imidazolium bromide, into a complete catalytically active site and confined in a NaY zeolite super-cage with an appropriate spatial arrangement was investigated. This integration was achieved through a molecular self-assembly method. A preliminary test of this catalyst system for the carbonylation of aniline to methyl phenyl carbamate indicated that far higher catalytic activity could be achieved (TOF increased from 3 000 to 23 000 h −1 ) with far lower amounts of the IL solvent and the Pd complex in comparison with a simple mixture of Pd(phen)Cl 2 /IL/NaY as the catalyst. This new system can also be applied to other areas of catalysis.

Controlled Interphase in Carbon Fiber/Epoxy Composites by Molecular Self-Assembly Method

In this paper, a new method based on molecular self-assembly on carbon fiber surface was proposed for the improvement of interfacial properties between fiber and epoxy matrix in a composite system. In order to obtain the controlled interphase, the surface of carbon fibers was first metallized by electroless Ag plating, then was reacted with terminally functionized alkanethiols or aromatic thiols to form Ag-thiolate thin films, which further reacted with epoxy resin to generate a strong adhesion interface. The composition, structure and the morphology of the modified carbon fiber surface were examined by X-ray photoelectron spectroscopy (XPS), surface-enhanced Raman scattering (SERS) and atomic force microscope (AFM), respectively. The results showed that these self-assembly molecules were chemisorbed onto the carbon fiber surface coated with silver via the strong S-Ag bond. In addition, these thiol molecules act as coupling agents between the epoxy matrix and carbon fiber through active functional end-groups, such as –OH, -NH2. The interfacial shear strength (IFSS) of the microcomposites after introduced the controlled interphase using the microbond testing was improved.

Controlled interface between carbon fiber and epoxy by molecular self-assembly method

In this paper, a new treatment method based on molecular self-assembly on carbon fiber surface was proposed for obtaining a controlled interface between carbon fiber and epoxy matrix in composite system. To form the controlled interfacial region, the surfaces of carbon fibers were first metallized by electroless Ag plating, then were reacted with a series of thiols (different chain lengths and terminally functional groups) to form self-assembly monolayers (SAMs), which further reacted with epoxy resin to generate a strong adhesion interface. The morphology, structure and composition of untreated and treated carbon fiber surface were investigated by atomic force microscope (AFM), surface-enhanced Raman scattering spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS), respectively. SERS study showed that thiols chemisorbed on Ag/carbon fiber in the form of thiolate species via the strong S–Ag coordinative bond. XPS study further confirmed the chemisorption by an S 2p 3/2 component observed at 162.2 eV. The binding energy was characteristic of silver thiolate. The interfacial shear strength of the carbon fiber/epoxy microcomposites was evaluated by the microbond technique. The results showed that there was a direct effect of the interfacial parameters changes such as chain lengths and surface functional groups on the fiber/matrix adhesion.

Transport and photodetection in self-assembled semiconductor quantum dots

A great step forward in science and technology was made when it was discovered thatlattice mismatch can be used to grow highly ordered, artificial atom-like structures calledself-assembled quantum dots. Several groups have in the meantime successfullydemonstrated useful infrared photodetection devices which are based on thistechnology. The new physics is fascinating, and there is no doubt that many newapplications will be found when we have developed a better understanding of theunderlying physical processes, and in particular when we have learned how to integratethe exciting new developments made in nanoscopic addressing and molecularself-assembly methods with semiconducting dots. In this paper we examine the scientificand technical questions encountered in current state of the art infrared detectortechnology and suggest ways of overcoming these difficulties. Promoting simplephysical pictures, we focus in particular on the problem of high temperaturedetector operation and discuss the origin of dark current, noise, and photoresponse.

Synthesis and characterization of new alkali-soluble polyimides and preparation of alternating multilayer nano-films therefrom

New alkali-soluble aromatic polyimides were prepared by a direct one-step polycondensation of 3,6-di(4-carboxyphenyl)pyromellitic dianhydride with common aromatic diamines in the presence of isoquinoline at 170 °C. The obtained polymers with inherent viscosities of the 0.62–1.01 g/dl range were all amorphous and highly soluble in dilute aqueous NaOH and tetramethylammonium hydroxide. Upon heating in TGA, the carboxylic acid groups degraded away at lower temperatures and the chain backbone did at higher temperatures. In DSC, no glass transition could be detected before decomposition. The alternating multilayer nano-films from the polyimides and poly(ethyleneimine) were prepared by the molecular self-assembly method and characterized by ellipsometry and X-ray reflectivity.