X.J. Yang

Rational Design of Chiral Nanostructures from Self-Assembly of a Ferrocene-Modified Dipeptide

We report a new paradigm for the rational design of chiral nanostructures that is based on the hierarchical self-assembly of a ferrocene (Fc)-modified dipeptide, ferrocene-L-Phe-L-Phe-OH (Fc-FF). Compared to other chiral self-assembling systems, Fc-FF is unique because of its smaller size, biocompatibility, multiple functions (a redox center), and environmental responsiveness. X-ray and spectroscopic analyses showed that the incorporation of counterions during the hierarchical self-assembly of Fc-FF changed the conformations of the secondary structures from flat β sheets into twisted β sheets. This approach enables chiral self-assembly and the formation of well-defined chiral nanostructures composed of helical twisted β sheets. We identified two elementary forms for the helical twist of the β sheets, which allowed us to create a rich variety of rigid chiral nanostructures over a wide range of scales. Furthermore, through subtle modulations in the counterions, temperature, and solvent, we are able to precisely control the helical pitch, diameter, and handedness of the self-assembled chiral nanostructures. This unprecedented level of control not only offers insights into how rationally designed chiral nanostructures can be formed from simple molecular building blocks but also is of significant practical value for the use in chiroptics, templates, chiral sensing, and separations.

MoO2–CoO coupled with a macroporous carbon hybrid electrocatalyst for highly efficient oxygen evolution

Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2.

Preparation and Properties of Nano‐SiO2/Epoxy Composites Cured by Mannich Amine

Nano‐SiO2/epoxy composites cured by Mannich Amine (type T‐31) were prepared and studied and the results are reported in this paper. The nano‐SiO2 was pretreated by a silane coupling agent (type KH‐550) and mixed with epoxy resin (type E‐51) using an ultrasonic processor. Amounts of filler loading ranged from 1% to 5% of the weight of the epoxy resin. Some properties of the resulting composites were characterized by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results of tensile tests and impact tests showed that the composite with 3% nano‐SiO2 loading presented the best mechanical performances. The tribological performance and thermal stability of the materials were also improved with the addition of nano‐SiO2.

A Bi2Te3@CoNiMo composite as a high performance bifunctional catalyst for hydrogen and oxygen evolution reactions

Hydrogen generated renewably by using solar energy has attracted increasing interest in the renewable energy research community. Hence, efficient electrocatalysts are in demand to reduce costs and energy consumption for oxygen and hydrogen evolution reaction (OER and HER) activity. Bismuth telluride (Bi2Te3)-based materials, as topological insulators (TIs), have been used to explore the fundamental properties of TIs in recent years, but investigation as functional materials for water splitting applications is still quite limited. In this work, electrocatalysts based on Bi2Te3 nanosheets have been fabricated, and the HER performance was investigated to further enhance OER electrocatalytic properties, with certain transition metals (Co, Ni, and Mo) selected to provide effective electrocatalytic sites. Therefore, the bifunctional catalyst Bi2Te3@CoNiMo was designed for synthesis by a solvothermal and chemical deposition route. The catalyst electrode, Bi2Te3@CoNiMo loaded on Ni foam, exhibits higher activity towards both the oxygen and the hydrogen evolution reactions than some traditional metallic catalysts in alkaline electrolytes. The difference in the HER and OER metrics (ΔE = 1.41 V) is comparable to the theoretical value (1.23 V), so that this reaction can be easily driven by a solar cell.

Nano‐SiO2 Doped Polystyrene Materials for Inertial Confinement Fusion Targets

Nano‐SiO2 doped polystyrene (SiO2‐d‐PS) for inertial confinement fusion (ICF) targets materials were prepared by pretreating the surface of nano‐SiO2 using silane coupling agents (A‐171 and A‐174) and by means of melt‐blending technology. Some of the properties of the nano‐SiO2 and SiO2‐d‐PS materials were characterized using dispersibility experiments, X‐ray photoelectron spectroscopy (XPS), tensile tests, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The results showed that the dispersibility of nano‐SiO2 powder in tetrahydrofuran was significantly enhanced through pretreatment. The surface state of pretreated nano‐SiO2 was changed and the content of the ‒C˭O and ‒C‒O groups was increased as determined by XPS. The SiO2‐d‐PS materials had higher thermal stability compared to virgin PS through TGA. Youngs modulus of SiO2‐d‐PS materials was increased compared with virgin PS. The pretreatment process is an effective way to break the aggregation of nano‐TiO2 according to TEM results.

Preparation and characterization of Nano-TiO2 doped polystyrene materials by melt blending for inertial confinement fusion

Abstract Nano‐TiO2 doped polystyrene (PS) materials (TiO2‐d‐PS) used for inertial confinement fusion (ICF) targets were prepared by means of melt blending. The effect of the pretreatment process, including coupling agents and ultrasonic dispersion on nano‐TiO2, was studied. Tensile tests were conducted to evaluate the mechanical properties of the TiO2‐d‐PS materials. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to characterize the degree of dispersion of nano‐TiO2 in the PS matrix. Transmission electron microscopy (TEM) and dynamic contact angle (DCA) measurements were introduced to demonstrate the surface state of untreated and pretreated nano‐TiO2. The results showed that coupling agents improved the interfacial adhesion between the PS matrix and dopants; ultrasonic dispersion contributed to the increase in the tensile properties of the TiO2‐d‐PS materials. The dispersion stability of nano‐TiO2 powder and the stability of the TiO2‐d‐PS materials were significantly enhanced through pretreatment, which was supported by the increase in the DCA when the nano‐TiO2 was pretreated by the coupling agent. The results of SEM and EDS indicated that the nano‐TiO2 dispersed homogeneously in the PS matrix. The pretreatment process is an effective way to break the aggregation of nano‐TiO2, which was confirmed by TEM results. Melt blending is a feasible method to prepare PS doped high Z element ICF target materials.

Photo‐Induced Polymerization and Reconfigurable Assembly of Multifunctional Ferrocene‐Tyrosine

The photo-induced reconfigurable assembly of nanostructures via the simultaneous noncovalent and covalent polymerization of a functional ferrocene-tyrosine (Fc-Y) molecule is reported. The Fc-Y monomers can directly self-assemble into nanospheres with a smooth surface driven by noncovalent interactions. By covalent photo-crosslinking of the Fc-Y monomers, the nanospheres transform spontaneously into hollow vesicles composed of hierarchically ordered lamellar structures. It is worth noting that the formed nanostructures exhibit both reducing property for in situ mineralization of gold nanoparticles with tunable biocatalytic behavior, and the redox activity for superior energy storage capacity. The measured energy storage capacity is 31 mAh g-1 for the nanospheres, which is the highest value reported so far for peptide assemblages as supercapacitor. The results offer insights into the dynamic self-assembly of highly ordered multifunctional materials with promising applications in catalysis, sensing, energy and biomedical fields.

Rational Design of Mimic Multienzyme Systems in Hierarchically Porous Biomimetic Metal–Organic Frameworks

A facile approach was reported to establish mimic multienzyme systems with hierarchically porous (HP) biomimetic metal-organic frameworks (MOFs) and natural enzymes for tandem catalysis. The hierarchically porous MOF HP-PCN-224(Fe) with peroxidase-like activity and tunable hierarchical porosity was synthesized via a modulator-induced strategy. HP-PCN-224(Fe) not only acts as the enzyme-immobilization matrix but also as an effective enzyme mimic, which could cooperate with the immobilized natural enzyme to catalyze the cascade reactions. The mimic multienzyme systems were used for the efficient colorimetric detection of a series of biomolecules, including glucose and uric acid. This work displays the great potential to construct highly functional biocatalysts by integrating the merits of both natural enzymes and MOF mimics, which are promising for applications in biosensing and biomimetic catalysis.