The charge/discharge capacity of current lithium-ion
materials is limited by the charge compensation of transition-metal
redox during the charge/discharge processes. Recently, the use of
oxide ion redox for charge compensation has been proposed to realize
a higher charge/discharge capacity than that observed for transition-metal
redox. Different stabilization mechanisms of the reversible oxide
ion redox have been proposed. To clarify the mechanism, analysis of
the electronic and local structures around oxygen is required. Because
of the high-voltage region in which the oxide ion redox occurs, several
reactions such as oxygen gas evolution and/or electrolyte oxidation
are often included. Thus, operando measurements are
required to directly prove this concept and generalize the understanding
of the oxide ion redox. This study employs operando soft/hard X-ray absorption spectroscopy combined with X-ray diffraction
spectroscopy for four lithium-excess electrode materials with different
chemical bond natures. The experimental data together with online
analysis of the generated on-charge gas reveal two extreme cases:
significantly enhanced covalent or ionic characters in the metal–oxygen
chemical bonds, which are necessary conditions to stabilize the oxidation
of the oxide ions. This finding provides new insights with exciting
possibilities for designing high energy density cathode materials
based on anion redox.
In this study, we identified the sources of trace metals, investigated their spatial distribution in topsoil and assessed their potential ecological risk in the area surrounding a typical manganese mining area in Xiangtan, Hunan Province, China. The concentrations of Mn, Cu, Pb, Zn, Cd, Ni, Cr and Hg in the topsoil of the study area were measured. Except for Cr and Hg, all trace metals exceeded the corresponding soil background values for Hunan Province. The spatial variation in trace metals was visualized by GIS, and the results show that trace metals in topsoil are enriched mainly around mines and smelters. Two groups of trace metals were identified using the spatial distribution, trend analysis, Pearson’s correlation and principal component analysis: Mn, Cu, Pb, Zn, Cd and Ni can be attributed to industrial and mining activities, whereas Cr and Hg are of natural origin. The results also revealed the extent of the influence of secondary processes such as the prevailing wind direction, erosion of mine tailings and rainwater runoff play significant roles in the wider dispersal and transfer of trace metals. In addition, the environmental risk of metal pollution was evaluated by applying the geoaccumulation index and potential ecological risk index (PERI) to the study area. The accumulated PERI for metals of concern is at highest risk level in the main manganese mine area. This decreases to a moderate risk around the manganese mine area, highlighting locations for further risk management concern. Furthermore, nearly 80% of the potential ecological risk was from Cd across the study area.
A reversible luminescence nanoswitch through competitive hydrophobic interaction among copper nanoclusters, p-nitrophenol and α-cyclodextrin is established, and a reliable real-time luminescent assay for acid phosphatase (ACP) activity is developed on the basis of this luminescence nanoswitch. Stable and intensely luminescent copper nanoclusters (CuNCs) were synthesized via a green one-pot approach. The hydrophobic nature of CuNCs aggregate surface is identified, and further used to drive the adsorption of p-nitrophenol on the surface of CuNCs aggregate due to their hydrophobic interaction. This close contact switches off the luminescence of CuNCs aggregate through static quenching mechanism. However, the introduction of α-cyclodextrin switches on the luminescence since stronger host-guest interaction between α-cyclodextrin and p-nitrophenol causes the removal of p-nitrophenol from the surface of CuNCs. This nanoswitch in response to external stimulus p-nitrophenol or α-cyclodextrin can be run in a reversible way. Luminescence quenching by p-nitrophenol is further utilized to develop ACP assay using p-nitrophenyl phosphate ester as the substrate. Quantitative measurement of ACP level with a low detection limit of 1.3 U/L was achieved based on this specific detection strategy. This work reports a luminescence nanoswitch mediated by hydrophobic interaction, and provides a sensitive detection method for ACP level which is capable for practical detection in human serum and seminal plasma.
Sustainable and profitable commercial aquaculture production of marine fish species is dependent on the development of sustainable protein sources as substitutes for expensive animal meals such as fishmeal (FM). Previous Florida pompano Trachinotus carolinus studies have indicated that poultry by-product meal (PBM) and meat and bone meal can be used to produce a FM-free diet if suitable levels of nutrients (such as taurine) are included in the diets. In this study, we attempted to develop an all-plant protein diet by removing the animal proteins in practical diets for pompano by substituting back select ingredients. A series of eight FM-free diets were formulated, four systematically replaced soybean meal (SBM) with soy protein concentrate (SPC) and four replaced PBM with SPC. Based on the results, there is no clear disadvantage to the use of SPC as a replacement for SBM. However, the complete removal of PBM resulted in reduced performance. Two additional growth trials were conducted to supplement additional amino acids including glycine, valine and histidine, a proprietary chemical attractant mix, fish protein concentrate and squid hydrolysate to improve the growth of pompano when fed all-plant protein diets. The only improvement in performance occurred with the squid hydrolysate. These results demonstrate that using soybean meal, soy protein concentrate and corn gluten meal as the primary protein sources, a plant-based feed formulation can be developed, but the removal of all animal proteins is not yet feasible.
K E Y W O R D Sattractant, growth performance, plant-based diet, Trachinotus carolinus L.
integrated with Li
successfully synthesized by the mechanical milling
route and examined as a new series of positive electrode materials
for rechargeable lithium batteries. Although uniform mixing at the
atomic scale between LiMnO
was not anticipated because of the noncompatibility of crystal structures
for both phases, our study reveals that phosphorus ions with excess
lithium ions dissolve into nanosize crystalline LiMnO
first evidenced by elemental mapping using STEM-EELS combined with
total X-ray scattering, solid-state NMR spectroscopy, and a theoretical
study. The integrated phase features a low-crystallinity
metastable phase with a unique nanostructure; the phosphorus ion located
at the tetrahedral site shares faces with adjacent lithium ions at
slightly distorted octahedral sites. This phase delivers a large reversible
capacity of ∼320 mA h g
as a high-energy
positive electrode material in Li cells. The large reversible capacity
originated from the contribution from the anionic redox of oxygen
coupled with the cationic redox of Mn ions, as evidenced by
soft XAS spectroscopy, and the superior reversibility
of the anionic redox and the suppression of oxygen loss were also
found by online electrochemical mass spectroscopy. The improved reversibility
of the anionic redox originates from the presence of phosphorus ions
associated with the suppression of oxygen dimerization, as supported
by a theoretical study. From these results, the mechanistic foundations
of nanostructured high-capacity positive electrode materials were
established, and further chemical and physical optimization may lead
to the development of next-generation electrochemical devices.
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