Influences of Metal Core and Carbon Shell on the Microwave Absorption Performance of Cu-C Core-Shell Nanoparticles.

Metal-C core-shell nanoparticles have been recently demonstrated to be promising candidates for microwave absorption applications. However, the underlying absorption mechanism, such as the contributions of the metal cores and C shells on their absorption performance, remains far from clear due to the complicated interfaces and synergetic effects between metal cores and C shells, as well as the significant challenges in the preparation of samples with well-defined comparability. In this study, Cu-C core-shell nanoparticles and their derivatives, i.e., bare Cu and hollow C nanoparticles, were synthesized for a comparative study on their microwave absorption properties. Electric energy loss models of the three samples were established, and based on these models, the comparative study suggested that the polarization loss could be significantly improved by C shells, and Cu cores had negligible influences on the conduction loss of Cu-C core-shell nanoparticles. The interface between C shells and Cu cores tuned the conduction loss and polarization loss to establish improved impedance matching and achieve optimal microwave absorption performances. A wide effective bandwidth of 5.4 GHz and a low reflection loss of -42.6 dB were achieved for Cu-C core-shell nanoparticles. This work provides new insights into how metal nanocores and C nanoshells affect the microwave absorption of core-shell nanostructures from experimental and theoretical points of view, which has reference values for the construction of highly efficient metal-C-based absorbers.

Photoredox-Catalyzed Cascade Radical Cyclization of Ester Arylpropiolates with CF3SO2Cl To Construct 3-Trifluoromethyl Coumarin Derivatives.

We report a highly efficient method to construct 3-trifluoromethyl coumarins using CF3SO2Cl as the trifluoromethyl radical source with ester 3-arylpropiolates. The reaction incorporated a cascade cyclization/dearomatization/ester migration/oxidization/rearomatization process to afford various 3-trifluoromethyl coumarins under visible light irradiation in good to excellent yields.

Iron-catalyzed tandem oxidative coupling and acetal hydrolysis reaction to prepare formylated benzothiazoles and isoquinolines.

The aldehyde group is one of the most versatile intermediates in synthetic chemistry, and the introduction of an aldehyde group into heteroarenes is important for the transformation of molecular structure. Herein, we achieved the direct formylation of benzothiazo/les and isoquinolines. The reaction features a novel iron-catalyzed Minisci-type oxidative coupling process using commercially available 1,3-dioxolane as a formylated reagent followed by acetal hydrolysis without a separation process. The reaction can be performed under exceedingly mild reaction conditions and exhibits broad functional group tolerance.

Optimization of extraction flavonoids from Exocarpium Citri Grandis and evaluation its hypoglycemic and hypolipidemic activities.

ETHNOPHARMACOLOGICAL RELEVANCE: Exocarpium Citri Grandis (ECG; Huajuhong in Chinese) is a precious traditional Chinese medicine with a history of hundreds of years in China. It has been demonstrated to possess numerous pharmacological properties, including antitussive, expectorant, anti-inflammatory, hypoglycemic, and hypolipidemic. However, no in-depth report exists on the hypoglycemic and hypolipidemic properties of ECG. AIM OF THE STUDY: This study aimed to evaluate the hypoglycemic and hypolipidemic properties of ECG flavonoids extract in vitro and in vivo so as to lay the foundation for further researches in this field. MATERIALS AND METHODS: Total flavonoids (TF) and naringin were separately extracted from ECG, and the components of TF were identified by HPLC-MS. The antioxidant capacities of TF and naringin were determined by 2,2,1-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging tests, and digestive enzymes activity inhibition assays in vitro in order to evaluate their hypoglycemic properties. Furthermore, diabetic mice experiments were performed to assess the hypoglycemic and hypolipidemic properties of TF and naringin in vivo. RESULTS: Five compounds were identified from TF, including naringin, rhoifolin, poncirin, bergaptol, and naringenin. The half maximal inhibitory concentration (IC50) of TF and naringin to DPPH-free radicals were 0.269 and 1.946 mg/mL, respectively. TF and naringin demonstrated a certain inhibitory effect on α-glucosidase and a weaker inhibitory effect on α-amylase. The results of animal experiments showed that TF and naringin had no significant effect on the blood glucose levels, but they could lead to significant (p < 0.05 or p < 0.01) increase in the serum insulin level and high-density lipoprotein cholesterol (HDL-C) levels with concomitant reduction in the total cholesterol (TC), total triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C) levels in diabetic mice. In addition, TF and naringin could reduce the liver index of diabetic mice (p < 0.01) and reduce the kidney index at low doses (p < 0.05). CONCLUSIONS: Our study revealed that the hypoglycemic and hypolipidemic activities of TF is mainly derived from naringin, and other active ingredients in TF also have the effects of alleviating oxidative stress, inhibiting digestive enzyme activity and reducing blood lipids. Our results thus provide a scientific basis for the application of ECG in antidiabetic treatment.

Analog and Digital Bipolar Resistive Switching in Solution-Combustion-Processed NiO Memristor.

In this study, a NiO-based resistive memristor was manufactured using a solution combustion method. In this device, both analog and digital bipolar resistive switching were observed. They are dependent on the stressed bias voltage. Prior to the electroforming, the analog bipolar resistive switching was realized through the change of the Schottky barrier at p-type NiO/Ag junction by the local migration of the oxygen ion in the interface. On the basis of the analog resistive switching, several synaptic functions were demonstrated, such as nonlinear transmission characteristics, spike-rate-dependent plasticity, long-term/short-term memory, and "learning-experience" behavior. In addition, once the electroforming operation was carried out using a high applied voltage, the resistive switching was changed from analog to digital. The formation and rupture of the oxygen vacancy filaments is dominant. This novel memristor with the multifunction of analog and digital resistive switching is expected to decrease the manufacturing complexity of the electrocircuits containing analog/digital memristors.

Porous TiO2 Assembled from Monodispersed Nanoparticles.

Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

Hydrothermal synthesis and structural characterization of the first mixed molybdenum-tungsten capped-keggin polyoxometal complex: {[Co(dien)]4[(AsVO4)MoV8WVI4O33(micro2-OH)3]}.2H2O.

The first polyoxometal complex possessing affirmatory mixed molybdenum-tungsten capped Keggin-type structure has been hydrothermally synthesized.

Hydrothermal syntheses and structural characterizations of organic-inorganic hybrid materials of the M(II)-ligand/vanadium oxide system (M(II) = Mn(II), Cu(II) and Zn(II); ligand = 2,2'-bipyridine and 1,10-phenanthroline).

Three organic-inorganic hybrid compounds [Mn(bpy)V(bpy)V(3)O(11)] (bpy = 2,2'-bipyridine) (1), [Cu(bpy)V(2)O(6)] (2) and [Zn(phen)3][V(2)O(6)].10H(2)O (phen = 1,10-phenanthroline) (3) have been synthesized hydrothermally. Single crystal X-ray diffraction analyses revealed that compound 1 is the first example of bpy units coordinating to different transition metals in one molecule. Compound 2 is a new isomer of [Cu(bpy)V(2)O(6)] which was named the gamma-isomer by us. In compound 3, a 2-D water sheet with big holes filled by the "naked" [V(4)O(12)](4-) clusters is found.