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The atomic-level metal-modulated MOFs as an advanced trifunctional electrocatalyst for oxygen evolution reaction, hydrogen evolution reaction and oxygen reduction reaction.

Cobalt-chromium ferrite, CoCrxFe2−xO4 (x = 0–1.2), has been synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD) indicates that samples calcined at 800 °C for 3 h were a single-cubic phase. The lattice parameter decreased with increasing Cr concentration. Scanning electron microscopy (SEM) confirmed that the sample powders were nanoparticles. It was confirmed from the room temperature Mössbauer spectra that transition from the ferrimagnetic state to the superparamagnetic state occurred with the doping of chromium. Both the saturation magnetization and the coercivity decreased with the chromium doping. With a higher annealing temperature, the saturation magnetization increased and the coercivity increased initially and then decreased for CoCr0.2Fe1.8O4.

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A sol-gel autocombustion method was used to synthesize Al3+ ion-substituted cobalt ferrite CoAlxFe2−xO4 (x = 0–1.5). According to X-ray diffraction analysis (XRD), cobalt ferrite was in a single cubic phase after being calcined at 1000 °C for 3 h. Moreover, the lattice constant decreased with increase in aluminum substituents. When the sample was analyzed by Scanning Electron Microscopy (SEM), we found that uniformly sized, well-crystallized grains were distributed in the sample. Furthermore, we confirmed that Al3+ ion-substituted cobalt ferrite underwent a transition from ferrimagnetic to superparamagnetic behavior; the superparamagnetic behavior was completely correlated with the increase in Al3+ ion concentration at room temperature. All these findings were observed in Mössbauer spectra. For the cobalt ferrite CoAlxFe2−xO4, the coercivity and saturation magnetization decrease with an increase in aluminum content. When the annealing temperature of CoAl0.1Fe1.9O4 was steadily increased, the coercivity and saturation magnetization initially increased and then decreased.

We investigate theoretically four-wave mixing (FWM) response and optical bistability (OB) in a hybrid nanosystem composed of a metal nanoparticle (MNP) and a semiconductor quantum dot (SQD) coupled to a nanomechanical resonator (NR). It is shown that the FWM signal is enhanced by more than three orders of magnitude as compared to that of the system without exciton-phonon interaction, and the FWM signal can also be suppressed significantly and broadened due to the exciton-plasmon interaction. As the MNP couples strongly with the SQD, the bistable FWM response can be achieved by adjusting the SQD-MNP distance and the pumping intensity. For a given pumping constant and a fixed SQD-MNP distance, the enhanced exciton-phonon interaction can promote the occurrence of bistability. Our findings not only present a feasible way to detect the spacing between two nanoparticles, but also hold promise for developing quantum switches and nanoscale rulers.

Coupling with electrospinning technique, metal–organic‐frameworks (MOFs)‐derived porous carbon fibers exhibit a great potential application in the adsorption of volatile organic compounds (VOCs) because of their huge surface area, high porosity, as well as sufficient heteroatom‐doped active sites. In this work, the hierarchically porous N‐doped carbon nanofibers are obtained after the pyrolysis of zeolite imidazole framework‐8 and polyacrylonitrile (ZIF‐8/PAN) composite fibers synthesized by electrospinning method. The N‐doped carbon nanofibers fabricated in N2 atmosphere (N‐CF‐N2) present an enhanced adsorption capacity of 694 mg/g for benzene because of the synergistic effect of the hierarchically porous structure and the abundant N‐species‐containing active sites. It is also interesting that the N‐doped hierarchical carbon nanofibers fabricated in Ar atmosphere (N‐CF‐Ar) exhibit a low benzene adsorption as compared with the N‐CF‐N2, which can be attributed to the porous structure damage caused by the bombardment of heavy Ar atoms on the pore shells during the pyrolysis. These results not only show a promising application of the as‐fabricated N‐CF‐N2 in adsorption of VOCs for air purification due to its merit of cost‐efficient, large‐scale production, and excellent adsorption capacity, but also expand the potential of electrospinning technology and composite fibers in volatile organic gas adsorption.

Background: A multiferroic material can simultaneously show two or more basic magnetic properties, including ferromagnetism, antiferromagnetism, and ferroelectricity. BiFeO 3 is a multiferroic material with a rhombohedral distorted perovskite structure. Doping can reduce the volatility of Bi and greatly improve the magnetoelectric properties of BiFeO 3 . Methods: To investigate the influence of the doping content we used the following analytical methods: X-ray powder diffraction (XRD), scanning electron microscopy (SEM), microwave network analysis (PNA-N5244A), and the Superconducting Quantum Interference Device (Quantum Design MPMS) test. Results: With the increase of Ca 2+ concentration in the solution, the grain size of Bi 1-x Ca x FeO 3 becomes smaller, showing the role of Ca 2+ ions as the dopant for fine grains. The calcination temperatures are the major causes for the saturated magnetization. The residual magnetization (M r ) and the coercive force (H c ) decrease linearly with the increase of x value, and due to the effect of Ca 2+ substitution at Bi 3+ sites, which causes the valence change of Fe and/or the oxygen vacancies. Conclusions:The XRD result indicates that the diffraction peak emerges with the increase of Ca 2+ and the main diffraction peak achieves a high angle. The best calcining temperature is 600 °C, and the morphology is very dependent on the calcining temperature.