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Nature Materials Sep 2023A common obstacle of many organic semiconductors is that they show highly unipolar charge transport. This unipolarity is caused by trapping of either electrons or holes...
A common obstacle of many organic semiconductors is that they show highly unipolar charge transport. This unipolarity is caused by trapping of either electrons or holes by extrinsic impurities, such as water or oxygen. For devices that benefit from balanced transport, such as organic light-emitting diodes, organic solar cells and organic ambipolar transistors, the energy levels of the organic semiconductors are ideally situated within an energetic window with a width of 2.5 eV where charge trapping is strongly suppressed. However, for semiconductors with a band gap larger than this window, as used in blue-emitting organic light-emitting diodes, the removal or disabling of charge traps poses a longstanding challenge. Here we demonstrate a molecular strategy where the highest occupied molecular orbital and lowest unoccupied molecular orbital are spatially separated on different parts of the molecules. By tuning their stacking by modification of the chemical structure, the lowest unoccupied molecular orbitals can be spatially protected from impurities that cause electron trapping, increasing the electron current by orders of magnitude. In this way, the trap-free window can be substantially broadened, opening a path towards large band gap organic semiconductors with balanced and trap-free transport.
PubMed: 37386064
DOI: 10.1038/s41563-023-01592-3 -
Journal of Separation Science Oct 2023The development of renewable and low-carbon gases for injection into the gas grid obtained by different processes such as anaerobic digestion, pyrogasification,... (Review)
Review
The development of renewable and low-carbon gases for injection into the gas grid obtained by different processes such as anaerobic digestion, pyrogasification, hydrothermal gasification, and methanation, followed by upgrading steps, increases the demand for analysis and characterization in order to fully manage their integration into the gas value chain. If the analysis of the main compounds (methane, carbon dioxide, hydrogen, and carbon monoxide) is well described, the analysis of impurities in renewable gases remains more challenging due to their various natures and quantities. After a brief description of renewable and low-carbon methane production processes, the review focuses on the methods used for the analysis of the different compounds in renewable gases, from the main ones to impurities at ppb levels. Gas chromatography (GC), coupled with different detectors, is the preferred technique, enabling the analysis and quantification of siloxanes, terpenes, oxygenates, and sulfur compounds. Recently, comprehensive two-dimensional GC has been applied to renewable gases, increasing the number of compounds detected. Non-chromatographic techniques are also reviewed. As sampling is of major importance in the search for reliable analyses, a whole section is devoted to this aspect. Among the available methods, pre-concentration on adsorbent tubes emerges as the most relevant solution.
PubMed: 37464555
DOI: 10.1002/jssc.202300330 -
Journal of Forensic Sciences Sep 2023Nearly a decade ago, fentanyl reappeared in the United States illicit drug market. In the years since, overdose deaths have continued to rise as well as the amount of...
Nearly a decade ago, fentanyl reappeared in the United States illicit drug market. In the years since, overdose deaths have continued to rise as well as the amount of fentanyl seized by law enforcement agencies. Research surrounding fentanyl production has been beneficial to regulatory actions and understanding illicit fentanyl production. In 2017, the Drug Enforcement Administration (DEA) began collecting seized fentanyl samples from throughout the United States to track purity, adulteration trends, and synthetic impurity profiles for intelligence purposes. The appearance of a specific organic impurity, phenethyl-4-anilino-N-phenethylpiperidine (phenethyl-4-ANPP) indicates a shift in fentanyl production from the traditional Siegfried and Janssen routes to the Gupta-patent route. Through a collaboration between the DEA and the US Army's Combat Capabilities Development Command Chemical Biological Center (DEVCOM CBC), the synthesis of fentanyl was investigated via six synthetic routes, and the impurity profiles were compared to those of seized samples. The synthetic impurity phenethyl-4-ANPP was reliably observed in the Gupta-patent route published in 2013, and its structure was confirmed through isolation and structure elucidation. Organic impurity profiling results for illicit fentanyl samples seized in late 2021 have indicated yet another change in processing with the appearance of the impurity ethyl-4-anilino-N-phenethylpiperidine (ethyl-4-ANPP). Through altering reagents traditionally used in the Gupta-patent route, the formation of this impurity was determined to occur through a modification of the route as originally described in the Gupta patent.
Topics: United States; Humans; Fentanyl; Illicit Drugs; Drug Contamination; Drug Overdose; Analgesics, Opioid
PubMed: 37203260
DOI: 10.1111/1556-4029.15281 -
Forensic Science International Sep 2023The organic impurity profile of 3,4-methylenedioxyamphetamine (MDA) synthesised from helional via the "twodogs" method was examined to identify route-specific and...
The organic impurity profile of 3,4-methylenedioxyamphetamine (MDA) synthesised from helional via the "twodogs" method was examined to identify route-specific and condition-specific impurities. The synthesis used a condensation reaction, followed by a Beckmann rearrangement, then Hofmann rearrangement, and then conversion to a hydrochloride salt. Two chlorinating agents were investigated for the Hofmann rearrangement reaction, trichloroisocyanuric acid (TCCA) and sodium hypochlorite. Three route-specific impurities were identified in MDA using TCCA, and two of these impurities were condition-specific such that the impurities that formed were dependent on the alcohol used as solvent. Three additional impurities were identified as non-route-specific as they have previously been identified in MDA synthesised from 3,4-methylenedioxycinnamic acid or piperonal. These non-route-specific impurities were also identified in MDA synthesised using sodium hypochlorite. No impurities were detected in MDA hydrochloride. This study identified route- and condition-specific organic impurities in MDA synthesised via the "twodogs" synthetic route using helional as starting material. The results in this study provide further understanding into the illicit synthesis of MDA and highlight the expanding nature of precursors used for illicit drug manufacture. It provides valuable information to decision makers to enact legislative measures and restrict precursors of concern.
PubMed: 37499374
DOI: 10.1016/j.forsciint.2023.111788 -
Chemosphere Aug 2023Plastic packaging contains residues from substances used during manufacturing, such as solvents, as well as non-intentionally added substances (NIAS), such as... (Review)
Review
Plastic packaging contains residues from substances used during manufacturing, such as solvents, as well as non-intentionally added substances (NIAS), such as impurities, oligomers, or degradation products. By searching peer-reviewed literature, we found that at least 10,259 chemicals were related to plastic packaging materials, which include chemicals used during manufacturing and/or present in final packaging items. We then summarized and discussed their chemical structures, analytical instruments, migration characteristics, and hazard categories where possible. For plastic packaging chemicals, examination of the literature reveals gas and liquid chromatography hyphenated to a variety of accurate mass analyzers based on the use of high-resolution mass spectrometry is usually used for the identification of unknown migrants coming from plastic packaging. Chemical migration from food packaging is affected by several parameters, including the nature and complexity of the food, contact time, temperature of the system, type of packaging contact layer, and properties of the migrants. A review of the literature reveals that information on adverse effects is only available for approximately 1600 substances. Among them, it appears that additives are more toxic than monomers to wildlife and humans. Neurotoxicity accounted for the highest proportion of toxicity of all types of chemicals, while benzenoids, organic acids, and derivatives were the most toxic types of chemicals. Furthermore, studies have demonstrated that hydrocarbon derivatives, organic nitrogen compounds, and organometallic compounds have the highest proportions of dermatotoxicity, and organohalogen compounds have the highest proportions of hepatotoxicity. The main contributors to skin sensitization are organic salts. This study provides a basis for comprehensively publicizing information on chemicals in plastics, and could be helpful to better understand their potential risks to the environment and humans.
Topics: Humans; Plastics; Food Contamination; Food Packaging; Mass Spectrometry; Food
PubMed: 37116723
DOI: 10.1016/j.chemosphere.2023.138795 -
Chemosphere Dec 2023In response to the growing global concern over environmental pollution, the exploration of sustainable and eco-friendly materials derived from biomass waste has gained... (Review)
Review
In response to the growing global concern over environmental pollution, the exploration of sustainable and eco-friendly materials derived from biomass waste has gained significant traction. This comprehensive review seeks to provide a holistic perspective on the utilization of biomass waste as a renewable carbon source, offering insights into the production of environmentally benign and cost-effective carbon-based materials. These materials, including biochar, carbon nanotubes, and graphene, have shown immense promise in the remediation of polluted soils, industrial wastewater, and contaminated groundwater. The review commences by elucidating the intricate processes involved in the synthesis and functionalization of biomass-derived carbon materials, emphasizing their scalability and economic viability. With their distinctive structural attributes, such as high surface areas, porous architectures, and tunable surface functionalities, these materials emerge as versatile tools in addressing environmental challenges. One of the central themes explored in this review is the pivotal role that carbon materials play in adsorption processes, which represent a green and sustainable technology for the removal of a diverse array of pollutants. These encompass noxious organic compounds, heavy metals, and organic matter, encompassing pollutants found in soils, groundwater, and industrial wastewater. The discussion extends to the underlying mechanisms governing adsorption, shedding light on the efficacy and selectivity of carbon-based materials in different environmental contexts. Furthermore, this review delves into multifaceted considerations, spanning the spectrum from biomass and biowaste resources to the properties and applications of carbon materials. This holistic approach aims to equip researchers and practitioners with a comprehensive understanding of the synergistic utilization of these materials, ultimately facilitating effective and affordable strategies for combatting industrial wastewater pollution, soil contamination, and groundwater impurities.
Topics: Wastewater; Biomass; Nanotubes, Carbon; Environmental Pollutants; Soil
PubMed: 37848104
DOI: 10.1016/j.chemosphere.2023.140419 -
Accounts of Chemical Research Jul 2023ConspectusColloidal nanocrystals (NCs) are composed of inorganic cores and organic or inorganic ligand shells and serve as building blocks of NC assemblies. Metal and...
ConspectusColloidal nanocrystals (NCs) are composed of inorganic cores and organic or inorganic ligand shells and serve as building blocks of NC assemblies. Metal and semiconductor NCs are well known for the size-dependent physical properties of their cores. The large NC surface-to-volume ratio and the space between NCs in assemblies places significant importance on the composition of the NC surface and ligand shell. Nonaqueous colloidal NC syntheses use relatively long organic ligands to control NC size and uniformity during growth and to prepare stable NC dispersions. However, these ligands create large interparticle distances that dilute the metal and semiconductor NC properties of their assemblies. In this Account, we describe postsynthesis chemical treatments to engineer the NC surface and design the optical and electronic properties of NC assemblies. In metal NC assemblies, compact ligand exchange reduces the interparticle distance and drives an insulator-to-metal transition tuning the dc resistivity over a 10 range and the real part of the optical dielectric function from positive to negative across the visible-to-IR region. Juxtaposing NC and bulk metal thin films in bilayers allows the differential chemical and thermal addressability of the NC surface to be exploited in device fabrication. Ligand exchange and thermal annealing densifies the NC layer, creating interfacial misfit strain that triggers folding of the bilayers and is used to fabricate, with only one lithography step, large-area 3D chiral metamaterials. In semiconductor NC assemblies, chemical treatments such as ligand exchange, doping, and cation exchange control the interparticle distance and composition to add impurities, tailor stoichiometry, or make entirely new compounds. These treatments are employed in longer studied II-VI and IV-VI materials and are being developed as interest in III-V and I-III-VI NC materials grows. NC surface engineering is used to design NC assemblies with tailored carrier energy, type, concentration, mobility, and lifetime. Compact ligand exchange increases the coupling between NCs but can introduce intragap states that scatter and reduce the lifetime of carriers. Hybrid ligand exchange with two different chemistries can enhance the mobility-lifetime product. Doping increases carrier concentration, shifts the Fermi energy, and increases carrier mobility, creating n- and p-type building blocks for optoelectronic and electronic devices and circuits. Surface engineering of semiconductor NC assemblies is also important to modify device interfaces to allow the stacking and patterning of NC layers and to realize excellent device performance. It is used to construct NC-integrated circuits, exploiting the library of metal, semiconductor, and insulator NCs, to achieve all-NC, solution-fabricated transistors.
PubMed: 37342079
DOI: 10.1021/acs.accounts.3c00147 -
Chemistry, An Asian Journal Oct 2023Metal-organic frameworks (MOFs) are promising porous materials that have huge potential for gas separation when put in the membrane configuration. MOFs have huge... (Review)
Review
Metal-organic frameworks (MOFs) are promising porous materials that have huge potential for gas separation when put in the membrane configuration. MOFs have huge potential due to certain salient features of the MOFs such as excellent pore size, ease of tuning the pore chemistry, higher surface area, and chemical and thermal stabilities. MOFs have been explored for various gas separation and storage applications. This review discusses various approaches for fabricating MOFs-based membranes for the separation of H gas from a variety of feeds having various gases CO , CO, N , and CH as impurities. The emphasis has been put on three types of membranes for H separation which include MOFs-based hollow fibrous/tubular/disk membranes, MOFs-based mixed matrix membranes (MMMs), and MOFs-based stand-alone membranes. In addition, various challenges such as reducing inhomogeneity between MOFs and polymeric matrices have also been discussed. Similarly, the approaches to successfully decorating MOFs on different supports in different configurations have been explained. The possible ways of improving the MOFs-based membranes for H have also been discussed.
PubMed: 37818783
DOI: 10.1002/asia.202300619 -
Journal of Controlled Release :... Aug 2023Polymeric nanoparticles, as revolutionary nanomedicines, have offered a new class of diagnostic and therapeutic solutions for a multitude of diseases. With its immense... (Review)
Review
Polymeric nanoparticles, as revolutionary nanomedicines, have offered a new class of diagnostic and therapeutic solutions for a multitude of diseases. With its immense potential, the world witnesses the new age of nanotechnology after the COVID-19 vaccines were developed based on nanotechnology. Even though there are countless benchtop research studies in the nanotechnology world, their integration into commercially available technologies is still restricted. The post-pandemic world demands a surge of research in the domain, which leaves us with the fundamental question: why is the clinical translation of therapeutic nanoparticles so restricted? Complications in nanomedicine purification, among other things, are to blame for the lack of transference. Polymeric nanoparticles, owing to their ease of manufacture, biocompatibility, and enhanced efficiency, are one of the more explored domains in organic-based nanomedicines. Purification of nanoparticles can be challenging and necessitates tailoring the available methods in accordance with the polymeric nanoparticle and impurities involved. Though a number of techniques have been described, there are no available guidelines that help in selecting the method to better suit our requirements. We encountered this difficulty while compiling articles for this review and looking for methods to purify polymeric nanoparticles. The currently accessible bibliography for purification techniques only provides approaches for a specific type of nanomaterial or sometimes even procedures for bulk materials, that are not fully relevant to nanoparticles. In our research, we tried to summarize the available purification techniques using the approach of A.F. Armington. We divided the purification systems into two major classes, namely: phase separation-based techniques (based on the physical differences between the phases) and matter exchange-based techniques (centered on physicochemical induced transfer of materials and compounds). The phase separation methods are based on either using nanoparticle size differences to retain them on a physical barrier (filtration techniques) or using their densities to segregate them (centrifugation techniques). The matter exchange separation methods rely on either transferring the molecules or impurities across a barrier using simple physicochemical phenomena, like the concentration gradients (dialysis method) or partition coefficients (extraction technique). After describing the methods in detail, we highlight their advantages and limitations, mainly focusing on preformed polymer-based nanoparticles. Tailoring a purification strategy takes into account the nanoparticle structure and its integrity, the method selected should be suited for preserving the integrity of the particles, in addition to conforming to the economical, material and productivity considerations. In the meantime, we advocate the use of a harmonized international regulatory framework to define the adequate physicochemical and biological characterization of nanomedicines. An appropriate purification strategy serves as the backbone to achieving desired characteristics, in addition to reducing variability. As a result, the present review aspires to serve as a comprehensive guide for researchers, who are new to the domain, as well as a synopsis of purification strategies and analytical characterization methods used in preclinical studies.
Topics: Humans; COVID-19 Vaccines; COVID-19; Nanotechnology; Nanomedicine; Polymers; Nanoparticles
PubMed: 37422123
DOI: 10.1016/j.jconrel.2023.06.038