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Polymers May 2024Additive manufacturing (AM) has revolutionised the manufacturing industry, offering versatile capabilities for creating complex geometries directly from a digital...
Additive manufacturing (AM) has revolutionised the manufacturing industry, offering versatile capabilities for creating complex geometries directly from a digital design. Among the various 3D printing methods for polymers, vat photopolymerisation combines photochemistry and 3D printing. Despite the fact that single-epoxy 3D printing has been explored, the fabrication of multi-material bioderived epoxy thermosets remains unexplored. This study introduces the feasibility and potential of multi-material 3D printing by means of a dual-vat Digital Light Processing (DLP) technology, focusing on bioderived epoxy resins such as ELO (epoxidized linseed oil) and DGEVA (vanillin alcohol diglycidyl ether). By integrating different materials with different mechanical properties into one sample, this approach enhances sustainability and offers versatility for different applications. Through experimental characterisation, including mechanical and thermal analysis, the study demonstrates the ability to produce structures composed of different materials with tailored mechanical properties and shapes that change on demand. The findings underscore the promising technology of dual-vat DLP technology applied to sustainable bioderived epoxy monomers, allowing sustainable material production and complex structure fabrication.
PubMed: 38891457
DOI: 10.3390/polym16111510 -
Beilstein Journal of Nanotechnology 2024Laser synthesis and processing of colloids (LSPC) is an established method for producing functional and durable nanomaterials and catalysts in virtually any liquid of... (Review)
Review
Laser synthesis and processing of colloids (LSPC) is an established method for producing functional and durable nanomaterials and catalysts in virtually any liquid of choice. While the redox reactions during laser synthesis in water are fairly well understood, the corresponding reactions in organic liquids remain elusive, particularly because of the much greater complexity of carbon chemistry. To this end, this article first reviews the knowledge base of chemical reactions during LSPC and then deduces identifiable reaction pathways and mechanisms. This review also includes findings that are specific to the LSPC method variants laser ablation (LAL), fragmentation (LFL), melting (LML), and reduction (LRL) in organic liquids. A particular focus will be set on permanent gases, liquid hydrocarbons, and solid, carbonaceous species generated, including the formation of doped, compounded, and encapsulated nanoparticles. It will be shown how the choice of solvent, synthesis method, and laser parameters influence the nanostructure formation as well as the amount and chain length of the generated polyyne by-products. Finally, theoretical approaches to address the mechanisms of organic liquid decomposition and carbon shell formation are highlighted and discussed regarding current challenges and future perspectives of LSPC using organic liquids instead of water.
PubMed: 38887526
DOI: 10.3762/bjnano.15.54 -
Angewandte Chemie (International Ed. in... Jun 2024Thioesters are important in synthesis, materials science, and biology, and their preparation traditionally relies on the use of disagreeable thiols. Here, we report a...
Thioesters are important in synthesis, materials science, and biology, and their preparation traditionally relies on the use of disagreeable thiols. Here, we report a thiol-free protocol that stitches together widespread carboxylic acids and aryl halides, producing a diverse array of thioesters. Crucial to this strategy is the discovery that tetramethylthiourea can serve as both a sulfur source and, upon direct excitation by purple light, as a strong reductant, suitable for activating aryl halides via single-electron transfer. Coupling of the resulting aryl radicals provides an isothiouronium ion intermediate, which can be attacked by carboxylic acids via a polar pathway, affording the thioester products under mild conditions.
PubMed: 38887166
DOI: 10.1002/anie.202407520 -
Journal of Environmental Radioactivity Jun 2024Metal hexacyanoferrates (MHCF) are a class of inorganic adsorbents used for wastewater management due to the presence of interstitial sites for capturing heavy metal...
Metal hexacyanoferrates (MHCF) are a class of inorganic adsorbents used for wastewater management due to the presence of interstitial sites for capturing heavy metal ions. In present work, we are reporting the synthesis of magnetic nanocomposite of FeO/graphene oxide/potassium copper hexacyanoferrate via wet chemical and coprecipitation approach. Potassium copper hexacyanoferrate (KCuHCF) and Graphene oxide (GO) both are marvelous adsorbents but their nano-size becomes a major obstacle in their separation process after the adsorption of the radionuclides. Thus, our synthesized nanocomposite FeO/GO/KCuHCF enhances the recovery of KCuHCF even after radioactive Cs adsorption with adsorption capacity of 18 mg g coinciding well with the Langmuir adsorption isotherm mechanism. The synthesized adsorbent is characterized thoroughly using UV-Visible spectroscopy, FT-IR, TGA, XPS, Raman spectroscopy, TEM-EDAX and XRD. This synthesized nanocomposite is used for the batch extraction of radioactive Cs from low level radioactive waste (LLW). The extraction kinetics followed pseudo-second-order kinetics mechanism.
PubMed: 38885562
DOI: 10.1016/j.jenvrad.2024.107481 -
Environmental Science & Technology Jun 2024Understanding of nitrous acid (HONO) production is crucial to photochemical studies, especially in polluted environments like eastern China. In-situ measurements of...
Understanding of nitrous acid (HONO) production is crucial to photochemical studies, especially in polluted environments like eastern China. In-situ measurements of gaseous and particulate compositions were conducted at a rural coastal site during the 2018 spring Ozone Photochemistry and Export from China Experiment (OPECE). This data set was applied to investigate the recycling of reactive nitrogen through daytime heterogeneous HONO production. Although HONO levels increase during agricultural burning, analysis of the observation data does not indicate more efficient HONO production by agricultural burning aerosols than other anthropogenic aerosols. Box and 1-D modeling analyses reveal the intrinsic relationships between nitrogen dioxide (NO), particulate nitrate (pNO), and nitric acid (HNO), resulting in comparable agreement between observed and simulated HONO concentrations with any one of the three heterogeneous HONO production mechanisms, photosensitized NO conversion on aerosols, photolysis of pNO, and conversion from HNO. This finding underscores the uncertainties in the mechanistic understanding and quantitative parametrizations of daytime heterogeneous HONO production pathways. Furthermore, the implications for reactive nitrogen recycling, ozone (O) production, and O control strategies vary greatly depending on the HONO production mechanism. On a regional scale, the conversion of HONO from pNO can drastically enhance O production, while the conversion from NO can reduce O sensitivity to NOx changes in polluted eastern China.
PubMed: 38885439
DOI: 10.1021/acs.est.3c07967 -
The Journal of Physical Chemistry... Jun 2024Absorption spectroscopy probing transitions from shallow-core d and f orbitals in lanthanides and actinides reveals information about bonding and the electronic...
Absorption spectroscopy probing transitions from shallow-core d and f orbitals in lanthanides and actinides reveals information about bonding and the electronic structure in compounds containing these elements. However, spectroscopy in this photon energy range is challenging because of the limited availability of light sources and extremely short penetration depths. In this work, we address these challenges using a tabletop extreme ultraviolet (XUV), ultrafast, laser-driven, high harmonic generation light source, which generates femtosecond pulses in the 40-140 eV range. We present reflection spectroscopy measurements at the N (i.e., predominantly 4d to 5f transitions) and O (i.e., 5d to 5f transitions) absorption edges on several lanthanide and uranium oxide crystals. We compare these results to density functional theory calculations to assign the electronic transitions and predict the spectra for other lanthanides. This work paves the way for laboratory-scale XUV absorption experiments for studying crystalline and molecular f-electron systems, with applications ranging from surface chemistry, photochemistry, and electronic or chemical structure determination to nuclear forensics.
PubMed: 38885194
DOI: 10.1021/acs.jpclett.4c01051 -
Journal of Chemical Theory and... Jun 2024In the realm of photochemistry, the significance of double excitations (also known as doubly excited states), where two electrons are concurrently elevated to higher...
In the realm of photochemistry, the significance of double excitations (also known as doubly excited states), where two electrons are concurrently elevated to higher energy levels, lies in their involvement in key electronic transitions essential in light-induced chemical reactions as well as their challenging nature from the computational theoretical chemistry point of view. Based on state-of-the-art electronic structure methods (such as high-order coupled-cluster, selected configuration interaction, and multiconfigurational methods), we improve and expand our prior set of accurate reference excitation energies for electronic states exhibiting a substantial amount of double excitations [Loos et al. 1939]. This extended collection encompasses 47 electronic transitions across 26 molecular systems that we separate into two distinct subsets: (i) 28 "genuine" doubly excited states where the transitions almost exclusively involve doubly excited configurations and (ii) 19 "partial" doubly excited states which exhibit a more balanced character between singly and doubly excited configurations. For each subset, we assess the performance of high-order coupled-cluster (CC3, CCSDT, CC4, and CCSDTQ) and multiconfigurational methods (CASPT2, CASPT3, PC-NEVPT2, and SC-NEVPT2). Using as a probe the percentage of single excitations involved in a given transition (%) computed at the CC3 level, we also propose a simple correction that reduces the errors of CC3 by a factor of 3, for both sets of excitations. We hope that this more complete and diverse compilation of double excitations will help future developments of electronic excited-state methodologies.
PubMed: 38885174
DOI: 10.1021/acs.jctc.4c00410 -
The Journal of Chemical Physics Jun 2024Understanding the nonadiabatic dynamics of complex systems is a challenging task in computational photochemistry. Herein, we present an efficient and user-friendly...
Understanding the nonadiabatic dynamics of complex systems is a challenging task in computational photochemistry. Herein, we present an efficient and user-friendly quantum mechanics/molecular mechanics (QM/MM) interface to run on-the-fly nonadiabatic dynamics. Currently, this interface consists of an independent set of codes designed for general-purpose use. Herein, we demonstrate the ability and feasibility of the QM/MM interface by integrating it with our long-term developed JADE package. Tailored to handle nonadiabatic processes in various complex systems, especially condensed phases and protein environments, we delve into the theories, implementations, and applications of on-the-fly QM/MM nonadiabatic dynamics. The QM/MM approach is established within the framework of the additive QM/MM scheme, employing electrostatic embedding, link-atom inclusion, and charge-redistribution schemes to treat the QM/MM boundary. Trajectory surface-hopping dynamics are facilitated using the fewest switches algorithm, encompassing classical and quantum treatments for nuclear and electronic motions, respectively. Finally, we report simulations of nonadiabatic dynamics for two typical systems: azomethane in water and the retinal chromophore PSB3 in a protein environment. Our results not only illustrate the power of the QM/MM program but also reveal the important roles of environmental factors in nonadiabatic processes.
PubMed: 38884395
DOI: 10.1063/5.0215036 -
Chemical Society Reviews Jun 2024Oxidative degradation is a powerful method to degrade plastics into oligomers and small oxidized products. While thermal energy has been conventionally employed as an... (Review)
Review
Oxidative degradation is a powerful method to degrade plastics into oligomers and small oxidized products. While thermal energy has been conventionally employed as an external stimulus, recent advances in photochemistry have enabled photocatalytic oxidative degradation of polymers under mild conditions. This tutorial review presents an overview of oxidative degradation, from its earliest examples to emerging strategies. This review briefly discusses the motivation and the development of thermal oxidative degradation of polymers with a focus on underlying mechanisms. Then, we will examine modern studies primarily relevant to catalytic thermal oxidative degradation and photocatalytic oxidative degradation. Lastly, we highlight some unique studies using unconventional approaches for oxidative polymer degradation, such as electrochemistry.
PubMed: 38884337
DOI: 10.1039/d4cs00407h -
Physical Chemistry Chemical Physics :... Jun 2024Polycyclic aromatic hydrocarbons are an important component of the interstellar medium of galaxies and photochemistry plays a key role in the evolution of these species...
Polycyclic aromatic hydrocarbons are an important component of the interstellar medium of galaxies and photochemistry plays a key role in the evolution of these species in space. Here, we explore the photofragmentation behaviour of the coronene cation (CH˙) using time-of-flight mass spectrometry. The experiments show photodissociation fragmentation channels including the formation of bare carbon clusters (C˙) and hydrocarbon chains (CH). The mass spectrum of coronene is dominated by peaks from C˙ and CH. Density functional theory was used to calculate relative energies, potential dissociation pathways, and possible structures for relevant species. We identify 6-6 → 5-7 ring isomerisation as a key step in the formation of both the bare carbon clusters and the hydrocarbon chains observed in this study. We present the dissociation mechanism outlined here as a potential formation route for C and other astrochemically relevant species.
PubMed: 38884178
DOI: 10.1039/d4cp01301h