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Monthly Archives: September 2023
A Critical Review of Soil Sampling and Data Analysis Strategies for Source Tracing of Soil in Forensic Investigations
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Flexible Composites for Piezocatalysis
Despite piezoelectric materials have a long history of application, piezoelectric catalysis has continued to be a hot topic in recent years. Flexible piezoelectric materials have just emerged in recent years due to their versatility and designability. In this paper, we review the recent advances in flexible piezoelectric materials for catalysis, discuss the fundamentals of the catalytic properties of composite materials, and detail the typical structures of these materials. We pay special attention to the types of filler in flexible piezoelectric composites, their role and the interaction between the particles and the flexible substrate. Notable examples of flexible piezoelectric materials for organic pollutants degradation, enhanced piezo-photocatalysis and antibacterial are also presented. Finally, we present key issues and future prospects for the development of flexible piezoelectric catalysts.
Purification and Fractionation of Lignin via ALPHA: Liquid–Liquid Equilibrium for the Lignin–Acetic Acid–Water System
In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid–liquid equilibrium (LLE) exist must be identified. To this end, pseudo-ternary phase diagrams for the lignin–acetic acid–water system were mapped out at 45-95 °C and various solvent: feed lignin mass ratios (S:F). For a given temperature, the accompanying SL (solid–liquid), SLL (solid–liquid–liquid), and one-phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)–water solutions was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie-line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases was also measured. As a representative example, lignin isolated in the lignin-rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50-55% AcOH and an S:F of 6:1, with said lignin being obtained at a yield of 50-70% of the feed lignin and having a molecular weight triple that of the feed.
[ASAP] Homoleptic Transition Metal Carbonyl Cations: Synthetic Approaches, Characterization and Follow-Up Chemistry
Accounts of Chemical Research
DOI: 10.1021/acs.accounts.3c00366
Tailoring Cu Electrodes for Enhanced CO2 Electroreduction through Plasma Electrolysis in Non‐Conventional Phosphorus‐Oxoanion‐Based Electrolytes
Plasma electrolysis of Cu electrodes in P-based electrolytes generates distinct surface structures, including octahedral nanocrystals, besides nanoporous and microporous features. Cu electrodes polarized in Na2HPO3 and Na3PO4 exhibit high selectivity for C2 products, establishing in-liquid plasma as an attractive option for developing efficient Cu electrocatalysts for sustainable CO2 conversion.
Abstract
This study presents a green, ultra-fast, and facile technique for the fabrication of micro/nano-structured and porous Cu electrodes through in-liquid plasma electrolysis using phosphorous-oxoanion-based electrolytes. Besides the preferential surface faceting, the Cu electrodes exhibit unique surface structures, including octahedral nanocrystals besides nanoporous and microporous structures, depending on the employed electrolyte. The incorporation of P-atoms into the Cu surfaces is observed. The modified Cu electrodes display increased roughness, leading to higher current densities for CO2 electroreduction reaction. The selectivity of the modified Cu electrodes towards C2 products is highest for the Cu electrodes treated in Na2HPO3 and Na3PO4 electrolytes, whereas those treated in Na2H2PO2 produce the most H2. The Cu electrode treated in Na3PO4 produces ethylene (23 %) at −1.1 V vs. RHE, and a comparable amount of acetaldehyde (15 %) that is typically observed for Cu(110) single crystals. The enhanced selectivity is attributed to several factors, including the surface morphology, the incorporation of phosphorus into the Cu structure, and the formation of Cu(110) facets. Our results not only advance our understanding of the influence of the electrolyte's nature on the plasma electrolysis of Cu electrodes, but also underscores the potential of in-liquid plasma treatment for developing efficient Cu electrocatalysts for sustainable CO2 conversion.
Green Additives in Chitosan‐Based Bioplastic Films: Physical, Mechanical, and Chemical Properties
Synthesis and analysis of chitosan-based materials with different green additives as a first step towards renewable plastic alternatives. The properties of the films were tunable in a broad range, and the additives could be divided in three different classes depending on their uptake behavior: linear, non-linear, and crosslinking additives.
Abstract
To switch to alternatives for fossil-fuel-based polymer materials, renewable raw materials from green resources should be utilized. Chitosan is such a material that is a strong, but workable derivative from chitin, obtained from crustaceans. However, various applications ask for specific plastic properties, such as certain flexibility, hardness and transparency. With different additives, also obtainable from green resources, chitosan-based composites in the form of self-supporting films, ranging from very hard and brittle to soft and flexible were successfully produced. The additives turned out to belong to one of three categories, namely linear, non-linear, or crosslinking additives. The non-linear additives could only be taken up to a certain relative amount, whereas the uptake of linear additives was not limited within the range of our experiments. Additives with multiple functional groups tend to crosslink chitosan even at room temperature in an acidic medium. Finally, it was shown that dissolving the chitosan in acetic acid and subsequently drying the matrix as a film results in reacetylation compared to the starting chitosan source, resulting in a harder material. With these findings, it is possible to tune the properties of chitosan-based polymer materials, making a big step towards application of this renewable polymer within consumer goods.
RNA‐Selective Small‐Molecule Ligands: Recent Advances in Live‐Cell Imaging and Drug Discovery
Advancing cell-membrane-permeable and/or bioactive small-molecule ligands specifically binding to RNA structures may provide powerful tools to understand further RNA biology in live cells and facilitate the investigation in the cutting-edge research areas of fluorescence live-cell imaging, chemical biology and drug discovery.
Abstract
RNA structures, including those formed from coding and noncoding RNAs, alternative to protein-based drug targets, could be a promising target of small molecules for drug discovery against various human diseases, particularly in anticancer, antibacterial and antivirus development. The normal cellular activity of cells is critically dependent on the function of various RNA molecules generated from DNA transcription. Moreover, many studies support that mRNA-targeting small molecules may regulate the synthesis of disease-related proteins via the non-covalent mRNA-ligand interactions that do not involve gene modification. RNA-ligand interaction is thus an attractive approach to address the challenge of “undruggable” proteins in drug discovery because the intracellular activity of these proteins is hard to be suppressed with small molecule ligands. We selectively surveyed a specific area of RNA structure-selective small molecule ligands in fluorescence live cell imaging and drug discovery because the area was currently underexplored. This state-of-the-art review thus mainly focuses on the research published within the past three years and aims to provide the most recent information on this research area; hopefully, it could be complementary to the previously reported reviews and give new insights into the future development on RNA-specific small molecule ligands for live cell imaging and drug discovery.
Metal‐Catalyzed Carbonylation Reactions with CO2: An Update
Catalytic carbonylation with CO2 : The latest updates on C1-carbonylative homologation of carbon scaffolds by means of metal catalyzed fixation of CO2 are collected in the present Review article. Innovative catalytic systems, enabling technologies and mechanistic investigations are contributing to the current developments of this fascinating research field.
Abstract
The utilization of CO2 as an efficient and environmentally friendly chemical analogue of CO is becoming a solid reality in the chemical scenario. CO2-based carbonylations have started paralleling the more consolidated carboxylation procedures, opening new horizons and perspectives in the utilization of carbon dioxide as an organic C1-containing building block. The advent of efficient and site-selective metal-catalyzed protocols for the fixation of CO2 into organic scaffolds, under controlled reductive conditions, contributed substantially to the development of robust, efficient, and convenient protocols. In the present Review article, a collection of the most recent examples of metal-catalyzed CO2-based carbonylations is documented with a particular emphasis on mechanistic aspects.
An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer
Halogen-atom-transfer (XAT) processes have revolutionized the use of ubiquitous halide reagents in organic chemistry. This mini-review focuses on recent C−C bond forming reactions that have exploited α-aminoalkyl radicals as metal-free XAT procedures.
Abstract
The merging of photocatalysis with halogen-atom transfer (XAT) processes has proven to be a versatile tool for the generation of carbon-centered radicals in organic synthesis. XAT processes are unique in that they generate radicals without requiring the use of strong reductants necessary for the traditional single electron transfer (SET) activation of halides. Pathways to achieve XAT in synthetic applications can be categorized into three major sections: i) heteroatom-based activators, ii) metal-based activators, and iii) carbon-based activators among which α-aminoalkyl radicals have taken the center stage. Access to these α-aminoalkyl radicals as XAT reagents has gained significant attention in the past few years due to the robustness of the reactions, the simplicity of the reagents required, and the broadness of their applications. Generation of these α-aminoalkyl radicals is simply achieved through the single electron oxidation of tertiary amines, which after deprotonation at the α-position generates the α-aminoalkyl radicals. Due to the wide scope of tertiary amines available and the tunable nucleophilicity of α-aminoalkyl radical formed, this strategy has become an attractive alternative to heteroatom/metal-based radicals for XAT. In this minireview, we focus our attention on recent (2020–2023) developments and uses of this robust technology to mediate XAT processes.