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Solid-State Electroanalytical Chemistry and Its Application in Plant Analysis
No full textSolid-state electroanalytical chemistry (SSEAC) is a method to analyze the information of solid materials by electrochemical methods, especially for the analysis of element composition, phase composition and redox state of solid materials. The SSEAC technology has been successfully applied to obtain the electrochemical information of natural pigments, plants, minerals and cultural relics with qualitative and quantitative analysis. SSEAC-based plant analysis is a cross-analysis technique emerging between electroanalytical chemistry and phytochemistry in recent years. SSEAC can provide a new understanding of the interspecific relationship, variation, differentiation and adaptation of species, which has a very intuitive practical value in the identification of medicinal materials, food safety and crop quality control. This article reviews the work of SSEAC technology in plant identification, plant phylogeny and plant physiological monitoring in recent years. This review also summarizes the challenges of SSEAC technology in plant analysis as well as its prospects in future development
Surface reinforcement doping to suppress oxygen release of Li-rich layered oxides
No full textLi-rich layered oxides can deliver ultrahigh capacities which stem from a blend of cationic redox and mostly lattice oxygen redox. However, the oxygen redox reaction often leads to structure transition and oxygen release from the material surface. Herein, the surface doping of B is conducted via a molten salt method, which creates a thin reinforcement layer containing stable B-O bonds. X-ray photoelectron spectroscopy reveals that the doping of B only acts on the material surface and cannot inhibit oxygen redox in the bulk. Differential electrochemical mass spectroscopy measurement demonstrates that the surface protective layer effectively reduces the oxygen release of LLOs. A combination of X-ray diffraction and transmission electron microscope analyses confirm the enhanced structural stability. As a consequence, the target material displays a high reversible capacity of 275 mAh g-1 at 0.1C and a suppressed voltage decay rate of 2.5 mV per cycle during the first 80 cycles (at 0.2C, 2.0-4.8V). The findings highlight the essential role of stable surface oxygen framework in cycling stability, and demonstrate the effectiveness of surface reinforcement doping in reducing oxygen release
Quantifying contrast of latent fingerprints developed by fluorescent nanomaterials based on spectral analysis
No full textFluorescent nanoparticles (NPs) have been used to develop latent fingerprints with enhanced contrast. However, a method for quantifying the contrast is still lacking, making it impossible to achieve quantitative comparison in the contrast enhancement between different fingerprint developing agents. Here we proposed a new method to quantify the developed contrast using two indexes when fluorescent NPs were used to develop the latent fingerprint. One is the intensity index (I) defined as the ratio between the integrated fluorescence intensities of the signal and background in the fluorescence spectra of the developed fingerprint. Another is the chroma index (C) determined from the color difference between developed fingerprints and their substrates in the chromaticity graph. We defined the developed contrast as the product of the chroma index and the common logarithm of the intensity index (C.lg I), and validated this method using both down- and up-conversion fluorescent NPs and on a variety of different substrates (glass, marble, red paper and money). We showed that the developed contrast quantified by our method effectively reflected the true contrast but the intensity or chroma index alone was not always effective. This work opens up a new avenue to quantifying and enhancing the developed contrast
Construction of hierarchical Prussian blue microcrystal with high sunlight absorption for efficient photo-thermal degradation of organic pollutants
No full textSolar-driven photocatalysis is considered to be a green and efficient approach for organic pollutants removal, however improving solar utilization and conversion still faces great challenge. Herein, Prussian blue (PB) microcrystals with different morphologies including PB-cube, PB-flower and PB-ball are fabricated via a secondaryassembly strategy. PB-ball with hierarchical structure possesses more exposed crystal faces, more mesopores, and higher FeII content, rendering its higher catalytic efficiency for organic pollutants degradation. Besides, structured hierarchical morphology leads to higher and broader sunlight absorption, which efficiently improves photo-Fenton performance of PBs due to the higher photon utilization. More importantly, we demonstrate that PBs with photothermal conversion property largely promotes its Fenton reaction rate under solar irradiation, and PBs as nano heat source in the photothermal Fenton system can accelerate the substance diffusion, charge carrier movement, as well as active radical generation. Thus, coupling of photo-Fenton and photothermal of dualfunction catalyst is an appealing strategy for organic pollutants removal
Excellent stability fuel cell type methanol sensor based on platinum-decorated mesoporous CrN
No full textThis paper has developed a fuel cell type methanol sensor based on platinum-decorated mesoporous chromium nitride (CrN). Mesoporous CrN is prepared by the zinc-oxygen precursor ammonolysis method, and the polyol method is adopted to load Pt on CrN and XC-72R carbon blacks. The sensor device manufactured by the hot-press process is tested at room temperature and without additional external voltage. The Pt/CrN sensor presents better stability compared with the Pt/C. The overall change in response current of the Pt/CrN sensor is relatively small within one month, while the Pt/C sensor deteriorates faster. Furthermore, the sensitivity of Pt/CrN is 0.0402 mu A/ ppm, which is 3.26 times higher than that of Pt/C. The Pt/CrN sensor also displays excellent reproducibility. This study indicates that CrN as a kind of supporting material is provided with good application prospects in methanol gas sensing
Rational Design of Highly Stable and Active MXene-Based Bifunctional ORR/OER Double-Atom Catalysts
No full textDesigning highly active and bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts has attracted great interest toward metal-air batteries. Herein, an efficient solution to the search for MXene-based bifunctional catalysts is proposed by introducing non-noble metals such as Fe/Co/Ni at the surfaces. These results indicate that the ultrahigh activities in Ni1/Ni2- and Fe1/Ni2-modified MXene-based double-atom catalysts (DACs) for bifunctional ORR/OER are better than those of well-known unifunctional catalysts with low overpotentials, such as Pt(111) for the ORR and IrO2(110) for the OER. Strain can profoundly regulate the catalytic activities of MXene-based DACs, providing a novel pathway for tunable catalytic behavior in flexible MXenes. An electrochemical model, based on density functional theory and theoretical polarization curves, is proposed to reveal the underlying mechanisms, in agreement with experimental results. Electronic structure analyses indicate that the excellent catalytic activities in the MXene-based DACs are attributed to the electron-capturing capability and synergistic interactions between Fe/Co/Ni adsorbents and MXene substrate. These findings not only reveal promising candidates for MXene-based bifunctional ORR/OER catalysts but also provide new theoretical insights into rationally designing noble-metal-free bifunctional DACs
Harnessing the Intriguing Properties of Magnetic Nanop to Detect and Treat Bacterial Infections
No full textInfections caused by pathogenic bacteria, especially multidrug-resistant bacteria, have become a serious worldwide public health problem. Early diagnosis and treatment can effectively prevent the adverse effects of such infections. Therefore, there is an urgent need to develop effective methods for the early detection, prevention, and treatment of diseases that are caused by bacterial infections. So far, magnetic material nanoparticles (MNPs) have been widely used in the detection and treatment of bacterial infections as detection agents and therapeutics. Therefore, this review describes the recent research on MNPs in bacterial detection and treatment. Finally, a brief discussion of challenges and perspectives in this field is provided, which is expected to guide the further development of MNPs for bacterial detection and treatment
Effect of functional groups of magnolol-based cyclic phosphonate on structure and properties of flame retardant epoxy resin
No full textFunctional group of a flame retardant may change performance and reaction mechanism of polymers to some extent. In this paper, magnolol-based cyclic phosphonates with double bond (DPDO) and epoxy group (EDPDO) were synthesized, and used in epoxy resin (EP). The EP/DPDO have better flame retardancy than that of EP/EDPDO in the UL-94 and LOI tests, while the pHRR of the latter decreases more that of the former in cone calorimetry test. Moreover, EP/EDPDO has higher glass transition temperature. Both DPDO and EDPDO do not deteriorate the mechanical properties and transparence of EP greatly. It is shown that the mechanism of the two is different. The DPDO is free in the resin, while the EDPDO is fixed in the framework of EP, therefore DPDO works in the gas and condensed phase, and EDPDO remains in the condensed phase. This work provides a simple solution to regulate the structure and performance of EP materials. (C) 2021 Elsevier Ltd. All rights reserved
Mechanisms on the stability and instability of water-in-oil emulsion stabilized by interfacially active asphaltenes: Role of hydrogen bonding reconstructing
No full textChemical demulsification is the most commonly used demulsification method for the separation of oil-water emulsions (W/O) in petroleum industry. Previous experiments demonstrate that the interfacially active asphaltenes (IAA) play the key role in stabilizing the heavy oil-water emulsions. Herein, the molecular dynamic simulation has been applied to reveal the molecular mechanisms on the stability and instability of the IAA-stabilized oil-water emulsions. It is found that IAA could accumulate at the oil-water interface and self-aggregate to form viscoelastic interfacial film through pi-pi stacking, hydrogen bonds (intermolecular and intramolecular) and other non-covalent bonds. Different types of hydrogen bonds (i.e., S = (OH)-H-center dot center dot center dot-O, R-(OHH)-H-center dot center dot center dot-O, N-(HN)-N-center dot center dot center dot-R, S-(HS)-S-center dot center dot center dot = O, S-(HS)-S-center dot center dot center dot-R) are found between the IAA molecules due to the presence of heteroatoms (e.g., N, O, S) in IAA. Increasing the IAA concentration would increase the thickness of the IAA film which plays the key roles in stabilizing the emulsions. When the newly synthesized demulsifier (i.e., MJTJU-2) was added into the oil-water emulsion system, the oxygen groups (i.e., hydroxyl, ester groups, carboxyl groups, ether group) in demulsifier could weaken (at least 50%) or even break the hydrogen bonds and pi-pi stacking between IAAs and form new stronger hydrogen bonds with water molecules. This hydrogen bond reconstruction facilitates the breaking of the IAA film at the oil-water interface, allowing the coalescence of the water droplets in oil phase. This work would provide fundamental understanding for developing new way to efficiently demulsify the petroleum or similar oil-water emulsions
Analysis on deformation and texture formation mechanism of hot-deformed Nd-Fe-B magnets based on heterogeneous structure evolution
No full textIn this paper, microstructure, micromagnetic structure, texture, together with magnetic properties of the hot-deformed (HD) Nd-Fe-B magnets were systematically studied to understand the deformation process and the formation mechanism of c-axis texture. The results show that the platelet grains are formed in the fine-grain regions at the initial stage of the deformation. As the amount of deformation increases, the proportion of platelet grains increases and arranges gradually, causing the formation of c-axis texture, till the grain merging occurres when the deformation is excessive. It should be noted that the rare earth-rich phase in the fine-grained region slowly diffuses to the coarse-grained region where only grain growth can be observed during deformation. The deformation mechanism and formation of c-axis texture in HD Nd-Fe-B magnets can be deduced to be accomplished by the processes of dissolution-precipitation diffusion, grain rotation and grain arrangement, based on the characterization of microstructure and texture evolution. Also, approaches to optimize the preparation process and magnetic properties of the hot-deformed Nd-Fe-B magnets were discussed. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology