Precursor For Preparation Research Articles

Pyruvate Aldol Condensation Product: A Metabolite That Escaped Synthetic Preparation for Over a Century.

The homoaldol condensation product of pyruvate, 2-methyl-4-oxopent-2-enedioic acid (OMPD), has been recently implicated as a catabolic intermediate in the bacterial degradation of lignin and previously identified from other biological sources in reports ranging over 60 years. Yet, while a preparation of the pyruvate homoaldol product precursor, 4-hydroxy-4-methyl-2-oxoglutaric acid (HMOG/Parapyruvate), was first reported in 1901, there has not been a complete published synthesis of OMPD. Analyses of reaction mixtures have helped identify zymonic acid, the lactone of HMOG, as the direct precursor to OMPD. The reaction appears to proceed through an acid- or base-mediated ring opening that does not involve formal lactone hydrolysis. In addition to a preparative protocol, we provide a proposed mechanism for the formation of methylsuccinic acid that arises from the nonoxidative decarboxylation of OMPD. Finally, we calculated the relative stability of the isomers of OMPD and found Z-OMPD to be the lowest in energy. These computations also support our observations that Z-OMPD is the most abundant isomer across a range of pH values.

Preparation and Characterisation of Metallorganic Precursors Derived Iron Oxides on Porous Silicon Layers

Porous silicon has generated interest in scientific community after its photoluminescence discovery and thereafter, research was focused on to the chemical functionalization of silicon and subsequent anchoring of nanoparticles onto silicon surface. In the present work, the porous silicon has been effectively modified with magnetic nanoparticles which were prepared through metallorganic approach. The as-fabricated magnetic-porous silicon composites were characterised using FTIR and Raman spectroscopies, Scanning Electron Microscopy (SEM) as well as magnetic measurements.

Tailoring the Meso-Structure of Gold Nanoparticles in Keratin-Based Activated Carbon Toward High-Performance Flexible Sensor

HighlightsMaterials with contradictory performance were prepared using wool keratin (WK).WK used for in situ preparation of AuNPs and N-doped carbon precursor as well.Two- and three-electrode flexible strip sensors designed for pH and UA detection.

Recent Advances in Alkyne Hydroamination as a Powerful Tool for the Construction of C−N Bonds

AbstractAlkyne hydroamination reaction has attracted many researchers due to its capability to form the required C−N bonds in the synthesis of the biologically and pharmacologically active N‐heterocycles. Hence, in this review, a comprehensive and updated summary of the research progress in this area (from 2014 on) is presented. In order to provide an easier access to the required information, a brief and concise description of the reaction mechanisms and preparation of precursors is also included, where possible. Accordingly, the alkyne hydroamination reactions are classified and summarized based on the type of hydroamination (inter‐ or intramolecular) and each class is further subdivided according to the number of members in the rings, so as to help the researchers in designing new N‐hetrocycles.

Preparation of carbonyl precursors for long-chain oxygenated fuels from cellulose ethanolysis catalyzed by metal oxides

Long-chain oxygenated liquid fuels have similar physicochemical properties with diesel fuel, and its oxygen can promote combustion and reduce PM2.5. An approach for the preparation of the precursor from lignocellulose suitable for CC coupling is the key problem to be solved in the production of long-chain oxygenated fuels. In this work, cellulose, as a main component in biomass, was directly alcoholyzed to carbonyl compounds with α-H catalyzed by three typical metal oxides (CaO, MgO and ZnO). The results showed that high temperature was favorable for the conversion of cellulose, but a large number of side products, namely levoglucosan and ethyl-α-D-pyran glucoside, have been detected in liquefied products. These by-products could be transformed into target precursors with α-H over CaO or ZnO with 0.5 mmol at 320 °C in ethanol solvent. Additionally, side reactions of ethanol at elevated temperature could be inhibited with ZnO in water-ethanol co-solvent and the by-products from ethanol dehydration, including 1,1-diethoxyethane, 2-ethoxyethanol, dropped significantly with an increase in carbonyl compounds. Noticeably, compared with pure ethanol, the yield of carbonyl compounds in liquid products increased obviously to 47.4% when the volume ratio of water to ethanol was 3: 10.

Suppression of voltage decay through adjusting tap density of lithium-rich layered oxides for lithium ion battery

The voltage decay of lithium-rich layered oxides (LLOs) is still one of the key challenges for their application in commercial battery although these materials possess the advantages of high specific capacity and low cost. In this work, the relationship between voltage decay and tap density of LLOs has been focused. The voltage decay can be significantly suppressed with the increasing tap density as well as the homogenization of the primary or secondary particle size of agglomerated spherical LLOs. Experimental results have shown that an extreme small voltage decay of 0.98 mV cycle−1 can be obtained through adjusting the tap density of agglomerated spherical LLOs to 1.99 g cm-3, in which the size of primary and secondary particles are uniform. Our work offers a new insight towards the voltage decay and capacity fading of LLOs through precursor preparation process, promoting their application in the real battery in the future.

Preparation of shape-controlled electric-eel-inspired SnO2@C anode materials via SnC2O4 precursor approach for energy storage

A tin dioxide/carbon composite (SnO2@C) with controlled shape is fabricated using a two-step method, which includes preparation of SnC2O4 precursors and subsequent heat treatment process. SnC2O4 precursors with different morphologies are synthesized by controlling the different proportions of tin sources, and some characterization techniques are carried out to screen out the optimum precursors. And the precursors are further annealed to obtain nanostructured SnO2 and coated with carbon film. Ultimately, shape-controlled SnO2@C anode materials are prepared, and the reaction process and electrochemical properties of SnO2@C composites as anode materials are further studied. The SnO2@C composite shows the capacity of 659.4 mAh g−1 after 100 cycles at a current density of 100 mA g−1. Even at the rate of 2000 mA g−1, the composite electrode can maintain a reversible capacity of 507.2 mAh g−1. The excellent electrochemical performance is beneficial to the synergistic effect between the carbon coating film and the nanostructured SnO2, which provides sufficient lithium storage sites, good electronic conductivity and void space to relieve the volume expansion.

Rapid synthesis of polyimide precursors by solution polymerization using Continuous-flow microreactors

Preparation method is of importance for development and application of polymers. Herein, we proposed a continuous-flow strategy for the preparation of polyimide precursors through solution polymerization in microreactors for the first time. The polymerization time was significantly reduced from several hours in a batch reactor to twenty minutes in a microreactor. Lower temperature, more appropriate molar ratio of monomers and longer residence time in the polymerization process resulted in poly(amic acid)s with higher molecular weights. Moreover, the relationship between the molecular weight and the residence time was used to discuss the polymerization kinetics. Meanwhile, the rapid preparation of poly(amic acid)s from pyromellitic dianhydride (PMDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), benzophenone-3,3′,4,4′- tetracarboxylic dianhydride (BTDA), 4,4′ - oxydiphthalic dianhydride (ODPA), or cyclobutane tetracarboxylic dianhydride (CBDA) was achieved in the microreactor. In particular, the number-average molecular weight of the PAA prepared by BTDA and 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether (6FODA) reached 36.3 kg / mol at the polymerization time of 19.6 min. This work demonstrated that microreactors would provide a promising and efficient pathway to prepare polyimide precursors with high molecular weights.

Environmental Impacts Assessment of NCM Cathode Material Production of Power Lithium-Ion Batteries

The nickel cobalt manganese ternary (NCM) cathode material is one of the important parts of power lithium battery. The NCM cathode material production process including the Li2CO3 preparation, precursor preparation and synthesis process of cathode materials is resource-and energy- intensive, thus it leads to relatively severe environment pollution. In this article, life cycle assessment of NCM cathode material production using coprecipitation method in China was conducted based on ReCiPe method. The environmental impacts of the main processes were calculated. The main factors and sources causing environmental pressure were identified. The results indicated that the precursor production contributed the most to environmental impacts in the NCM cathode material production. The energy consumption of the precursor production was 612MJ, accounting for 94.6% of the total energy consumption of NCM production. The environmental impacts of the CoSO4 production and NiSO4 production were the main contributors to that of the precursor production. The primary cobalt and nickel resources in China with lower grade and difficult mining led to the high energy consumption of these two kinds of raw materials. Therefore, the development and utilization of the secondary cobalt and nickel metals will be a great potential to reduce environmental impacts of NCM production.

Low-cost synthesis of AuNPs through ultrasonic spray pyrolysis

The present research informs about the synthesis of gold nanoparticles (AuNPs) through Ultrasonic Spray Pyrolysis (USP), which were collected in ethanol with 0.1% Polyvinylpyrrolidone (PVP). Initially, the research focused on two precursors, where the first represented a homemade H-HAuCl4, completed in our own laboratory through the chlorine gas method by using HCl and KMnO4, and the second was the commercial C-HAuCl4, prepared by using Gold (III) chloride tetrahydrate powder and deionised water. The goal was to find any potential precursor differences and their influences on the later use for AuNPs synthesis through USP using almost the same parameters. In the first step of research it was determined that the H-HAuCl4 precursor was similar to C-HAuCl4 in chemical composition, surface tension and pH value. This finding represented the starting point for being able to use H-HAuCl4 in the USP for AuNPs‘ synthesis. In the second step, AuNPs were synthesised from both types of precursors. Afterwards, characterisation of some functional properties by FTIR and UV–vis techniques was done directly for H- and C-AuNPs in the collecting media. For SEM/EDX and TEM microscopy both types of H- and C-AuNPs were dried, and observation revealed that the morphology, shape and size distribution of dried AuNPs were very similar. Based on the performed laboratory research, it could be concluded that prepared H-AuNPs could represent a new and low-cost effective solution for future USP transfer onto the industrial level, not only in in the process itself, but also in the field of Low-cost Precursor Preparation.

Preparation and Structural Characterization of Complex Oxide Eutectic Precursors from Polymer-Salt Xerogels Obtained by Microwave-Assisted Drying.

Sol–gel synthesis is an acknowledged method for obtaining fine inorganic powders of a different nature. Implementation of water-soluble polymers as gel-forming media makes this technique even more readily available, especially in cases where conventional gel formation is suppressed. In polymer–salt solutions, polymers serve as scaffolds for salt constituents’ bulk crystallization. When dried, solid salt particles are deposited on the polymer surface or in polymer matrix pores, which leads to higher grain size uniformity. The present work discusses the effect of drying conditions on phase composition and structure characteristics of complex oxide eutectics in ternary systems, CaO–Al2O3–Y2O3 (CAY) and MgO–Al2O3–Y2O3 (MAY), obtained from polymer–salt compositions based on polyvinyl alcohol (PVA), Na-salt of carboxymethylcellulose (Na-CMC) or polyvinylpyrrolidone (PVP). Microwave-assisted drying proved to be more efficient compared to convective process; however such technique requires careful selection of gel-forming polymer.

Unveiling the Importance of Precursor Preparation for Highly Efficient and Stable Phenethylammonium‐Based Perovskite Solar Cells

Unveiling the Importance of Precursor Preparation for Highly Efficient and Stable Phenethylammonium‐Based Perovskite Solar Cells

One step synthesis of Fe-SSZ-13 zeolite by hydrothermal method

Under hydrothermal conditions, Fe-SSZ-13 zeolite with CHA structure was synthesized directly using N, N, N-trimethyladamantane ammonium hydroxide (TMAdaOH) as the template. In the synthesis process, iron is added during the preparation of the zeolite gel precursor. After calcination, the obtained zeolite can be used directly as the catalyst without other subsequent treatments such as ion exchange. The species of iron in Fe-SSZ-13 zeolite were studied by XRD, H2-TPR, UV–Vis, etc. The characterization result proved that the obtained Fe-SSZ-13 zeolite has relatively active iron species, such as the monomer [Fe-(OH)2]+ and the dimer [HO-Fe-O-Fe-OH]2+. The Fe-SSZ-13 zeolite was used in the selective catalytic reduction of NOx with NH3 (NH3-SCR) and exhibits good catalytic performance.

Co/C broad band electromagnetic wave absorption composite derived from preferred precursor ZIF-67: preparation and performance

A simple sacrificial template method was used to prepare Co/C composite with cobalt nanoparticles embedded in nitrogen-doped polyporous graphite carbon as an efficient electromagnetic wave (EMW) absorbent. Effects of solvent polarity, ratio of Co2+ to 2-methylimidazole and pH value of reaction system on precursor metal–organic skeleton ZIF-67 were systematically studied by a single variable method, and then the optimal preparation process was obtained. Thermal decomposition time and temperature of precursor ZIF-67 are the keys to the formations of ferromagnetic metal cobalt particles and carbon matrix. Therefore, effects of calcined temperature in inert atmosphere on the carbon content, graphitization degree, magnetic properties and microwave-absorbing performances of Co/C composite prepared were studied, and then nitrogen-doped porous composite Co/C composed of a highly dispersed core–shell Co@graphite nanoparticles coated by amorphous carbon skeleton was successfully prepared by optimizing pyrolysis technology. Composite Co/C-900 obtained by ZIF-67 calcinated at 900 °C exhibits excellent EMW absorption performances at low filling amount; its maximum reflective loss (RLmax) reaches − 34.41 dB at 17.49 GHz with the test thickness of 2.0 mm only, and most importantly, when the test thickness is 2.5 mm, its effective absorption bandwidth (RL < − 10 dB) reaches 7.37 GHz (10.18–17.5 GHz), spanning the X and Ku bands. The synergistic effects of the self-loss (dielectric loss and magnetic dissipation) and structural attenuation (multiple scattering and interface polarization) of Co/C-900 obtained greatly improve its impedance matching with free space and attenuation coefficients to EMW, significantly widening its effective bandwidth. As a new high-performance EMW absorbent with thin thickness, light weight, strong absorption capacity and wide bandwidth, the Co/C composite optimized by precursor preparation and calcination process should have a broad application prospect.

Functional investigation and applications of the acetylesterase activity of the Citrus sinensis (L.) Osbeck peel

The hydrolysis of acetyl moieties on a set of commercially relevant substrates was performed by employing the whole tissue of Citrus sinensis (L.) Osbeck peel as an efficient biocatalyst in mild reaction conditions with high degree of regioselectivity. The reaction is done in aqueous media and the product is easily recovered. Optimal reaction conditions were deduced and two practical applications were investigated: the elaboration of acetylglicerols and the preparation of vitamin K1 precursor. Peel waste (flavedo and albedo) from orange juice manufacturing was successfully employed as a biocatalyst.

Microstructure, doping and optical properties of Co2+:ZnAl2O4 transparent ceramics for saturable absorbers: Effect of the ZnF2 sintering additive

Transparent cobalt-doped zinc aluminate spinel (gahnite), Co2+:ZnAl2O4, ceramics were fabricated by hot pressing of (Zn,Co)Al2O4/ZnF2 nanopowders at 1520 °C for 4 h. A novel approach was suggested for the preparation of (Zn,Co)Al2O4 precursor: the (Zn,Co)Al2O4 powders were synthesized by mixing an alcohol solution of aluminium isopropoxide with a joint aqueous solution of zinc formate (the source of zinc), cobalt nitrate and zinc fluoride (the sintering additive) followed by drying and calcination in air. The study of the thermal behavior of precursors revealed an optimum calcination temperature (700 °C) preventing the loss of the sintering additive (ZnF2). The effect of the ZnF2 content (3–10 wt%) on the microstructure, the cobalt doping concentration, absorption and luminescence of ceramics was systematically studied. The ceramics exhibit a close-packed microstructure with a mean grain size of 50–70 μm and high in-line transmission (about 84% at ∼2 μm). The actual concentration of Co2+ ions in tetrahedral (Td) sites of gahnite is lower than the Co2+ doping level and it decreases with the ZnF2 content. We propose a possible mechanism of this variation including both the losses of Co2+ via evaporation of the intermediate CoF2 phase and a partial location of Co2+ ions in octahedral (Oh) sites of gahnite due to its partly inverse spinel structure. The developed ceramics are promising for saturable absorbers of erbium lasers.

Preparation of a Key Tetraene Precursor for the Synthesis of Long Acenes

The tetraene 7,7‐dimethoxy‐2,3,5,6‐tetramethylenebicyclo[2.2.1]heptane is a key compound for the preparation of a large variety of acenes protected by a carbonyl bridge. We report herein a medium scale preparation in seven steps of this valuable starting material. Diels–Alder addition between 6,6‐dimethtyl fulvene and maleic anhydride, followed by carboxylation, ozonolysis of the double bond, reduction of the four ester groups, then chlorination of the alcohol groups and dehydrochlorination give the target compound in 17 % overall yield.

Preparation and stereolithography of SiC ceramic precursor with high photosensitivity and ceramic yield

Stereolithography of ceramic precursors is a valuable additive manufacturing technology for complex ceramic parts. In this study, a new SiC ceramic precursor—liquid hyperbranched polycarbosilane (LHBPCS) grafting acrylate group was synthesized by chlorinating some Si–H groups of LHBPCS with Cl2 followed by reacting with hydroxyethyl acrylate. The reaction processes and structures of intermediate reactant and target product were confirmed by FT-IR and 1H NMR. According to photolithography experiment and hardness test under UV light, the synthesized LHBPCS had high photo-curing activity. Thermogravimetric analysis indicated it also possessed high ceramic yield (the ceramic yield at 1000 °C was 74.4%). After shaping with stereolithography, defect-free green bodies could be got. When heated to 1000 °C, the transparent yellow green bodies transformed into black SiC rich ceramic parts and 18.3–25.1% linear shrinkage associated with the precursor-to-ceramic conversion was observed. Because the shrinkage in the pyrolysis stage was nearly isotropic and the shrinkage was lower than other reported data, no obvious deformation or crack was found in the pyrolyzed parts.

Unveiling the Importance of Precursor Preparation for Highly Efficient and Stable Phenethylammonium‐Based Perovskite Solar Cells

For the fabrication of low‐dimensional perovskite solar cells, understanding the effect of precursor preparation on film formation is critical to achieve high‐quality perovskite film and, therefore, high efficiency in related solar devices. Herein, the two methods to prepare phenethylammonium‐based mixed perovskite precursors with the same chemical composition are reported. These methods are called 1) different phase (DP) and 2) same phase (SP) methods as the former involves the mixing of a 3D perovskite precursor with a 2D perovskite precursor, whereas the latter involves the mixing of quasi‐2D perovskite precursors. The films prepared by these methods are characterized by X‐ray diffraction, Kelvin probe force microscopy, and scanning electron microscopy, revealing different perovskite structures. The power conversion efficiency (PCE) of the champion cells by DP and SP methods reaches 19.1% and 18.9%, respectively. Results of the aging test show a dramatic improvement in the stability of SP perovskite devices maintaining 86% of its initial performance after exposure to a relative humidity (RH) 8 ± 5% for 1000 hr and over 80% of its initial PCE after continuous 1 sun illumination (including UV) at RH 70%. The new insights provided by this work are important to design perovskite precursor preparation methods for the best device performance and stability.

Novel recoverable porous magnetic carbons derived from biobased polybenzoxazine by self-foaming and activation treatment

The novel fully biobased polybenzoxazine derived carbon adsorbents containing Fe3O4 magnetic nanoparticles are prepared by solvothermal method, followed by activation and carbonization treatments. There are the polymerization and self-foaming reactions of benzoxazine monomers, and thermal decomposition of Ferrous acetylacetonate during in situ preparation of magnetic carbon precursors. The designed and fabricated pentanoic acid type benzoxazine resin not only provides the rich oxygen-containing functional groups but also favors the development of porous structure for the resulting carbon materials. Both self-foaming reaction and activation treatment also benefit the formation of porous structure and improve the specific surface area. The dye adsorption performance, magnetic separability and recyclability of the fabricated carbon materials are investigated through selecting methylene blue as a cationic dye. The magnetic carbon materials occupy good adsorption capacity of cationic dye, resulting from rich oxygen-containing groups, relatively high specific surface area, and well-developed porous microstructure. The adsorption behavior of porous carbon adsorbents is fast, pH-sensitive, Langmuir monolayer adsorption mechanism, and better fitted to pseudo-second-order kinetic model. Moreover, easy magnetic separation and fast regeneration make the magnetic adsorbents suitable to be practically applied in wastewater treatment. Therefore, the flexible and effective strategy in this work may be generally applicable for the structural design and preparation of polymer derived magnetic carbon materials.