Yaobing Wang

Switch from intra- to intermolecular H-bonds by ultrasound: induced gelation and distinct nanoscale morphologies.

During cooling of the ( R)-N-Fmoc-Octylglycine (Fmoc-OG)/cyclohexane solution, gelation is observed exclusively when ultrasound is used as an external stimulus, while deposit is obtained without sonication. The xerogel consists of entangled fibrous network made by interconnected nanofibers, while the deposit comprises large numbers of unbranched nanowires. It is found that the Fmoc-OG molecules form bilayer structures in both the deposit and the gel. However, the ratio ( R) between the Fmoc-OG molecules in a stable intramolecular H-bonding conformation and those in a metastable intermolecular H-bonding conformation can be tuned by the ultrasound, R (deposit) > R (gel). The increased population of the intermolecular H-bonding Fmoc-OG molecules induced by the ultrasonication facilitates to the interconnection of nanofibers for the formation of the fibrous network, and therefore gelation. The alteration in the morphologies and properties of the obtained nanomaterials induced by the ultrasound wave demonstrates a potential method for smart controlling of the functions of nanomaterials from the molecular level.

Wear behavior of bulk Zr41Ti14Cu12.5Ni10Be22.5 metallic glasses

The wear behavior of bulk Zr41Ti14Cu12.5Ni10Be22.5 metallic glasses has been studied using sliding wear tests and scanning electron microscopy in both as-prepared and annealed samples. It was found that the wear resistance of differently processed samples increases in the following order: crystallized state; as-prepared state; relaxed state. The thermal stability of worn samples was also investigated by means of differential scanning calorimetry. Under the experiment conditions, no sliding wear-induced crystallization is observed in either as-prepared or relaxed samples indicating good thermal stability of the bulk metallic glasses.

Distinct nanostructures from isomeric molecules of bis(iminopyrrole) benzenes: effects of molecular structures on nanostructural morphologies

The effects of molecular structures on nanostructural morphologies have been studied through the preparation of nanospheres, square nanowires, and nanocubes from three isomeric molecules of bis(iminopyrrole)benzene.

Fe/Fe3C@C nanoparticles encapsulated in N-doped graphene–CNTs framework as an efficient bifunctional oxygen electrocatalyst for robust rechargeable Zn–air batteries

3d transition metals or their derivatives encapsulated in nitrogen-doped nanocarbon show promising potential in non-precious metal oxygen electrocatalysts. Herein, we describe the simple construction of a bifunctional oxygen electrocatalyst with a “framework-active sites” structure, namely Fe/Fe3C@C (Fe@C) nanoparticles encapsulated in 3D N-doped graphene and bamboo-like CNTs (Fe@C–NG/NCNTs). The Fe@C structure provides additional electrons on the carbon surface, promoting the oxygen reduction reaction (ORR) on adjacent Fe–Nx active sites. The 3D NG hybrid with a bamboo-like CNTs framework facilitates fast reactant diffusion and rapid electron transfer. The optimized sample displays excellent ORR and oxygen evolution reaction (OER) activity, with a potential difference of only 0.84 V; this places it among the best bifunctional ORR/OER electrocatalysts. Most importantly, Zn–air batteries using Fe@C–NG/NCNTs as the cathode catalyst deliver a peak power density of 101.2 mW cm−2 and a specific capacity of 682.6 mA h g−1 (energy density of 764.5 W h kg−1). After 297 continuous cycle tests (99 h), the rechargeable batteries using Fe@C–NG/NCNTs show a voltage gap increase of only 0.13 V, almost half that of Pt/C + Ir/C (0.22 V) under the same conditions. This work provides new insight into advanced electrocatalysts utilizing the structural features of host nanocarbon materials and guest active species toward energy conversion.

Photoinduced electron transfer in coaggregates of dicyanonaphthalene and pyrazoline.

The photophysical properties of mixed coaggregates containing 1,4-dicyanonaphthalene (DCN) and 1,3,5-triphenyl-2-pyrazoline (TPP) have been studied. The absorption spectra of mixed coaggregates indicate that a charge-transfer complex is not formed in the ground state between DCN and TPP. The fluorescence of TPP in the mixed coaggregates is quenched by DCN, accompanied with a broad and structureless emission at about 560 nm from an exciplex between DCN and TPP. The color of the emission from mixed coaggregates is tunable by changing the DCN content. The excited-state properties of the TPP-DCN molecule pair are investigated theoretically with a quantum chemistry method. The theoretical results have also confirmed that the broad emission at about 560 nm in the mixed coaggregates originates from the exciplex rather than from the charge-transfer complex.

Controllable Nanonet Assembly Utilizing a Pressure‐Difference Method Based on Anodic Aluminum Oxide Templates

Self-assembly of organic molecules from solution is one of the simplest methods to generate ordered nanostructures with potentially new properties. In particular, nanostructured architectures on the macroscopic scale have possible applications in the fields of electronics, catalysis, and medicine. However, controllable fabrication of nanostructured materials is still limited by the available processing methods. Template synthesis has been widely used as a controllable approach to achieve desirable nanostructured materials. Of the many different types of templates, anodic aluminum oxide (AAO) offers clear advantages in the making of onedimensional nanostructured materials and arrays; the AAO templates provide hexagonally packed, uniform pore arrays with a pore diameter that can be varied up to 200 nm. Amongst other applications, AAO has been used as a template for the syntheses of nanotubes for biomedicine and biotechnology, Bi1 xSbx nanowires as thermoelectric wires, SBA-15 nanorod arrays for protein separation and catalysis, and lipid nanotube arrays as a model of cellular membranes. Despite such progress, there have been few reports on the application of AAO as a substrate for the control of surface morphology on the macroscopic scale. Herein, we report for the first time the synthesis of the largearea (ca. 12 cm) nanonet architecture of 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin (TClPP; C44H26Cl4N4) using the AAO template as a substrate. Figure 1 shows the 3D structure of the TClPP molecule and its stacking. Alkylated polycyclic discotic molecules, such as porphyrins, are frequently employed as building blocks because of their ability to stack and form architectures and liquidcrystalline phases. We were able to use the stacking property of TClPP to successfully cultivate nanonet network architectures on the AAO templates. The TClPP nanonets were fabricated as follows. A 2-cm-diameter AAO disk about 15 mm in thickness was laid on a Buchner funnel fitted with a fritted disk. The funnel was then placed on a filter flask connected to a vacuum pump, which was used to maintain a pressure differential across the AAO disk. A solution of TClPP (1 mL, 0.13m) in CH2Cl2 was added dropwise to the AAO template. TClPP nanonets of different meshes in accordance with the AAO pore sizes were thus grown on the rear of the AAO template, that is, the side opposite to that of TClPP deposition. This process was repeated several times to obtain nanoparticles of larger size. Experimental parameters, such as the pressure differential, concentration of the TClPP solution, and the number of times of solution deposition, affected the type and the quality of the nanostructures formed, which will be discussed below. The morphology and size of the nanostructures were examined by field-emission scanning electron microscopy (SEM; Hitachi S-4300). Figures 2a and b show the SEM images of the TClPP nanonet structures formed on the AAO templates. It is evident that the nanonet structures were created as a result of uniform self-assembly of interlocking TClPP nanoparticles. The SEM images also suggest that the knots of the nanonets were formed by a single larger nanoparticle or by several assembled nanoparticles. In Figure 2a, the inner pores of the AAO substrate can be seen behind the floating nanonet. An advantage of this synthesis method was that the fabricated nanonet structure could be easily removed from the AAO substrate. Figure 2b shows the SEM image of a nanonet after it was removed from the substrate. The weblike nanonets showed ordered network structures with meshes mimicking the pore sizes of the AAO templates. Apparently the orderly pores of the AAO template aided the formation of the periodic pattern of the nanonets on the back surface of the template. Three different pore sizes (50, 100, and 200 nm) of the AAO templates were tried in the making of nanonets. A small Figure 1. 3D structure of the TClPP molecule (left) and its stacking (right).

Mixed-Metal–Organic Framework Self-Template Synthesis of Porous Hybrid Oxyphosphides for Efficient Oxygen Evolution Reaction

Developing an efficient, stable yet cost-effective electrocatalyst is the key link along the path to hydrogen fuels produced by water splitting. The current bottleneck in the water electrolysis technology is the sluggish oxygen-evolving reaction (OER) which is also central to the rechargeable metal-air batteries. Herein, we report a promising mixed-metal-organic framework (MMOF) self-template strategy to synthesize CoFe hybrid oxyphosphides with highly porous morphology. Aided by the porous hybrid bulk structure beneficial to fast-ion diffusion to abundant highly active sites, the as-synthesized Co3FePxO exhibited excellent electrocatalytic activity toward OER, with an overpotential of 291 mV at 10 mA cm-2 and a low Tafel slope of 85 mV dec-1. With the underpinnings of MMOF maintaining the structural rigidity and stability, the material also showed long life for OER without xa0discernible activity decay.

A porous Zn cathode for Li–CO2 batteries generating fuel-gas CO

Global climate change and energy concerns trigger worldwide interest in sustainable, economical CO2 reductive transformation into valuable chemicals. However, traditional electro/thermo-catalysis strategies usually consume a large amount of energy and suffer from low efficiency. Herein, a three-dimensional porous fractal Zn cathode is synthesized by redox-coupled electrodeposition and it exhibits excellent electrocatalytic properties for CO2-to-CO conversion. Inspired by the coupling of a metal battery and CO2 electroreduction, a novel fuel-gas CO generating Li–CO2 battery is firstly realized with the as-prepared porous fractal Zn cathode. Meanwhile, CO formation can be easily tuned within a wide range of discharge currents and reach a maximum faradaic efficiency of up to 67%. Finally, based on gas and solid discharge product analysis, the related mechanism of CO main product production is proposed as 2Li+ + 2CO2 + 2e− → CO + Li2CO3. Hence the present work presents a new way for the further development of metal–CO2 batteries to generate useful chemicals and fuels besides electrical energy.

1-Phenyl-3-(pyren-1-yl)prop-2-en-1-one

The title compound, C25H16O, was prepared by the condensation reaction of pyrene-1-carbaldehyde and acetophenone in ethanol solution at room temperature. The phenyl ring forms a dihedral angle of 39.10u2005(11)° with the pyrene ring system. In the crystal structure, adjacent pyrene ring systems are linked by aromatic π–π stacking interactions, with a perpendicular interplanar distance of 3.267u2005(6)u2005Å and a centroid–centroid offset of 2.946u2005(7)u2005Å.

Synergistic Supports Beyond Carbon Black for Polymer Electrolyte Fuel Cell Anodes

Polymer electrolyte fuel cells (PEFCs) are among the most advanced energy technologies with low operating temperatures, high energy densities, ease of transportation and storage. However, the deficiencies such as low activity and high cost of the electrocatalysts at anodes greatly hinder their commercialization. The commonly used carbon black supports lack the capacity of regulation over the supported noble metals towards efficient electro‐catalytic oxidation of fuels. In this Mini‐Review, the prerequisite factors in advanced supports are outlined, ranging from self‐supported precious metal alloys as well as non‐noble metal materials, while simultaneously revealing the superiorities of some advanced supports beyond carbon black in terms of electronic conductivity, synergy with surface precious metals, chemical and electrochemical stability, and other possible interactions. The effects arisen from microscopic morphology, nano‐structure, and composition on the electrocatalytic activity/stability are also discussed. Finally, several of the most promising supports are highlighted, and the research trends of synergistic supports in future PEFCs are predicted.