Enhanced TE properties of Cu@Ag/Bi2Te3 nanocomposites by decoupling electrical and thermal properties

Cu@Ag/Bi2Te3 nanocomposites were prepared for the first time by ultrasonic dispersion-rapid freezedrying method combined with spark plasma sintering(SPS).By changing the content of Cu@Ag nanoparticle,we could modulate the temperature dependent thermoelectric properties.The highest ZT value can be obtained at 450 K for 1 vol%Cu@Ag/Bi2Te3,which is benefited from the decoupling of electrical and thermal properties.With the increase of electrical conductivity,the absolute value of Seebeck coefficient lifts while the thermal conductivity declines.Meanwhile,the average ZT value between 300 K and 475 K was 0.61 for 1 vol%Cu@Ag/Bi2Te3,which is much higher than that of pristine Bi2 Te3.Therefore,the decoupling effect of Cu@Ag nanoparticles incorporation could be a promising method to broaden the application of Bi2Te3 based thermoelectric materials.     

Novel advances in metal-based solar absorber for photothermal vapor generation

Access to safe drinking water has become an extremely urgent research topic worldwide. In recent years, the technology of solar vapor generation has been extensively explored as a potential and effective strategy of transforming elements content in seawater. In this review, the basic concepts and theories of metal-based photothermal vapor generation device (PVGD) with excellent optical and thermal regulatory are introduced. In the view of optical regulation, how to achieve high-efficiency localized evaporation in different evaporation system (i.e., volumetric solar heating and interface solar heating) is discussed; from the aspect of thermal regulation, the importance of selective absorption surface for interfacial PVGD is analyzed. Based on the above discussion and analysis, we summarize the challenges of metal-based desalination device.     

Phosphorene: a Potential 2D Material for Highly Efficient Polysulfide Trapping and Conversion

Effectively trapping lithium polysulfide species and accelerating the reaction conversion kinetics are the main strategies to improve the performance of lithium-sulfur(Li-S) batteries. Since the researchers found in 2014 that two-dimensional(2D) phosphorene nanosheets could be exfoliated from the bulk black phosphorus, numerous researches have been devoted to exploring the phosphorene with unique properties for the application in Li-S batteries. In this review, we summarize the recent theoretical and experimental progress of phosphorene for Li-S batteries. Besides, we also introduce the relationship between the interfacial interaction on phosphorene and the performance enhancement of Li-S batteries. Furthermore, future challenges and remaining opportunities for phosphorene in Li-S batteries are finally discussed.     

Synthesis of N-TiO2@NH2-MIL-88(Fe) Core-shell Structure for Efficient Fenton Effect Assisted Methylene Blue Degradation Under Visible Light

Core-shell TiO₂-based photocatalysts with specific composition, morphology, and functionality have attracted considerable attention for their excellent degradation properties on organic pollutants via a photocatalytic oxidation process. Herein, a N-TiO₂@NH₂-MIL-88(Fe) core-shell structure was prepared by coating NH₂-MIL-88(Fe) on nitrogen-doped TiO₂(N-TiO₂) nanoparticles. Introduction of heteroatom nitrogen to pure TiO₂ expands the spectral response range, leading to enhanced quantum efficiency of photocatalyst. Furthermore, loading NH₂-MIL-88(Fe) on N-TiO₂ improved the adsorption ability of the nanocomposites due to the porous tunnels of NH₂-MIL-88(Fe). The resulted core-shell N-TiO₂@NH₂-MIL-88(Fe) nanocomposites realized the transfer of photo excited electrons from N-TiO₂ to NH₂-MIL-88(Fe) rapidly, partially reduced Fe³⁺ to Fe²⁺ in NH₂-MIL-88(Fe), and further enhanced the Fenton effect on efficiently degrading methylene blue dye(MB) under visible light(λ ≥ 420 nm) with the assistance of H₂O₂.     

Environmentally Benign Solution-Based Procedure for the Fabrication of Metal Oxide Coatings on Metallic Pigments

Aluminum pigments were coated with Fe₂O₃ and CuO by solution-based thermal decomposition of the urea nitrate compounds hexakisureairon(III)nitrate and tetrakisureacopper(II)nitrate. The deposition process was optimized to obtain homogeneously coated aluminum pigments. The growth of the surface coatings was controlled by investigation with scanning electron microscopy, energy dispersive X-ray spectroscopy and static light scattering as well as infrared, X-ray diffraction and thermogravimetric analysis. The iron precursor showed an incomplete decomposition in solution, incorporating traces of urea molecules inside the coatings while the copper precursor showed complete dissociation accompanied by in situ formation of amine complexes. The amount of organic residues resulting from ligand fragments in the final oxide coatings could be reduced to 22 % for the iron oxide and 12 % for the copper oxide by further temperature treatment in solution (259 °C). Colorimetric investigations of the obtained pigments revealed an excellent hiding power, outperforming the pigments used in current state-of-the-art formulations.     

Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules

The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.     

Effect of methoxy position on dynamic mechanical and shape memory properties of methoxyphenol-based polybenzoxazines

Abstract

Two series of benzoxazines were synthesized from o-, m-, and p-methoxyphenols, two polyetheramines with different molecular weights, and formaldehyde. The glass transition temperatures (T _gs) of m-methoxyphenol-based polybenzoxazines are respectively higher than those of o- and p-methoxyphenol-based counterparts. The polybenzoxazines exhibit thermally induced one-way dual-shape memory behavior based on T _g, and the o- and p-methoxyphenol-based polybenzoxazines exhibit higher shape memory performance than m-methoxyphenol-based counterparts under motion constraints.     

Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties

In this study, a series of cyclotriphosphazene derivatives containing a Schiff base (3a–3d) were synthesized by the reactions of hexachlorocyclotriphosphazene (1) with bis-aryl Schiff bases ( 2a – 2d ) having different terminal groups (H, F, Cl, and Br). The products ( 3a – 3d ) were characterized by elemental and mass analyses, FT-IR, and ¹ H, ¹³ C, and ³¹ P NMR spectroscopies. Furthermore, the structure of compound 3a was also determined by X-ray crystallography. The thermal behaviors and the spectral properties of the new cyclotriphosphazene compounds ( 3a – 3d ) were investigated and the results were compared in the series.     

Substituted 2-Phenacylbenzoxazole Difluoroboranes: Synthesis,Structure and Properties

Novel fluorescent dyes such as benzoxazole-boron complexes, bearing β-ketoiminate ligands, have been synthesized and characterized with a focus on the influence of a substituent on the basic photophysical properties. ¹H, ¹¹B, ¹³C, ¹⁵N, and ¹⁹F nuclear magnetic resonance (NMR) spectra of substituted 2-phenacylbenzoxazole difluoroboranes have been recorded and discussed. It is worth mentioning that a high correlation coefficient was found between ¹⁵N-NMR parameters and substituent constants. The photophysical properties of these new dyes have been investigated by fluorescence and ultraviolet-visible (UV-Vis) absorption spectroscopy. The geometry optimization, vibrational spectra, and the HOMO and LUMO energies were calculated based on density functional theory with the use of the B3LYP functional and 6-311++G(d,p) basis set.     

Production of Verbascoside,Isoverbascoside and Phenolic Acids in Callus,Suspension, and Bioreactor Cultures of Verbena officinalis and Biological Properties of Biomass Extracts

Callus, suspension and bioreactor cultures of Verbena officinalis were established, and optimized for biomass growth and production of phenylpropanoid glycosides, phenolic acids, flavonoids and iridoids. All types of cultures were maintained on/in the Murashige and Skoog (MS) media with 1 mg/L BAP and 1 mg/L NAA. The inoculum sizes were optimized in callus and suspension cultures. Moreover, the growth of the culture in two different types of bioreactors—a balloon bioreactor (BB) and a stirred-tank bioreactor (STB) was tested. In methanolic extracts from biomass of all types of in vitro cultures the presence of the same metabolites—verbascoside, isoverbascoside, and six phenolic acids: protocatechuic, chlorogenic, vanillic, caffeic, ferulic and rosmarinic acids was confirmed and quantified by the HPLC-DAD method. In the extracts from lyophilized culture media, no metabolites were found. The main metabolites in biomass extracts were verbascoside and isoverbascoside. Their maximum amounts in g/100 g DW (dry weight) in the tested types of cultures were as follow: 7.25 and 0.61 (callus), 7.06 and 0.48 (suspension), 7.69 and 0.31 (BB), 9.18 and 0.34 (STB). The amounts of phenolic acids were many times lower, max. total content reached of 26.90, 50.72, 19.88, and 36.78 mg/100 g DW, respectively. The highest content of verbascoside and also a high content of isoverbascoside obtained in STB (stirred-tank bioreactor) were 5.3 and 7.8 times higher than in extracts from overground parts of the parent plant. In the extracts from parent plant two iridoids—verbenalin and hastatoside, were also abundant. All investigated biomass extracts and the extracts from parent plant showed the antiproliferative, antioxidant and antibacterial activities. The strongest activities were documented for the cultures maintained in STB. We propose extracts from in vitro cultured biomass of vervain, especially from STB, as a rich source of bioactive metabolites with antiproliferative, antioxidant and antibacterial properties.