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Journal of the American Chemical Society Jul 2022The reaction of 5,5'-([2,2'-bipyridine]-5,5'-diyl)diisophthalaldehyde (BPDDP) with cyclohexanediamine and [benzidine (BZ)/[2,2'-bipyridine]-5,5'-diamine (BPDA)],...
The reaction of 5,5'-([2,2'-bipyridine]-5,5'-diyl)diisophthalaldehyde (BPDDP) with cyclohexanediamine and [benzidine (BZ)/[2,2'-bipyridine]-5,5'-diamine (BPDA)], respectively, affords a nitrogen-rich porous organic cage BPPOC and two two-dimensional (2D) covalent organic frameworks (COFs), USTB-1 and USTB-2 (USTB = University of Science and Technology Beijing), under suitable conditions. Interestingly, BPPOC with a single-crystal X-ray diffraction structure is able to successfully transform into USTB-1 and USTB-2 (newly converted COFs denoted as USTB-1c and USTB-2c, respectively) upon exchange of the imine unit of cyclohexanediamine in the cage by BZ and BPDA. Such a transformation also enables the isolation of analogous COFs (USTB-3c and USTB-4c) on the basis of an isostructural organic cage, BTPOC, which is derived from 5,5'-([2,2'-bithiophene]-4,4'-diyl)diisophthalaldehyde (BTDDP) and cyclohexanediamine. However, the conventional solvothermal reaction between BTDDP and BPDA leads to an impure phase of USTB-4 containing incompletely converted aldehyde groups due to the limited solubility of the building block. The newly prepared COFs have been characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. In particular, BPPOC is able to absorb the iodine vapor with an uptake of 5.64 g g, breaking the porous organic cage's (POC's) record value of 3.78 g g. Nevertheless, the cage-derived COFs exhibit improved iodine vapor adsorption capability in comparison with the directly synthesized counterparts, with the highest uptake of 5.80 g g for USTB-1c. The mechanism investigation unveils the superiority of nitrogen atoms to sulfur atoms for POCs in iodine vapor capture with the assistance of definite crystal structures. This, in combination with porosity, synergistically influences the iodine vapor capture capacity of COFs.
PubMed: 35765245
DOI: 10.1021/jacs.2c03959 -
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 -
Heliyon Oct 2022Biogas is a promising bioenergy alternative to be recovered from waste/wastewater in the context of environmental sustainability and circular economy. However, raw... (Review)
Review
Biogas is a promising bioenergy alternative to be recovered from waste/wastewater in the context of environmental sustainability and circular economy. However, raw biogas contains various secondary impurities such as carbon dioxide, hydrogen sulphide, siloxanes, nitrogen oxides (NOx), ammonia, and halogens. Depending on the emission rate of these biogas impurities, the importance of biogas is being hampered for its environmental, health and the detrimental effects possess by the impurities towards the downstream of the biogas users. Biogas impurities can cause different public health concerns (like pulmonary paralysis, asthma, respiratory diseases and deaths) and environmental impacts (such as global warming, climate change and their indirect impacts like drought, flooding, malnutrition and other disasters). The absence/inconsistent emission standards among countries, agencies, and other stakeholders is the other challenge that they possess during monitoring and controlling of these impurities. Different commercially available and emerging technologies are available for separating carbon dioxide (via biogas upgrading) and removing other biogas impurities. Technologies such as pressure swing adsorption, membrane separation, absorption-based techniques (water, chemical and physical organic solvents), cryogenic separation, and other emerging biotechnological platforms (like photobioreactor and biocatalysis) have been adopted in removing the impurities. This paper reviewed the main commercially available and new technologies and their performance in removing carbon dioxide (the main constituent of biogas) and other biogas impurities. Besides, the environmental and public health implications of biogas and future research perspectives are also highlighted.
PubMed: 36299513
DOI: 10.1016/j.heliyon.2022.e10929 -
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 -
Molecules (Basel, Switzerland) Aug 2022Dinotefuran (DNT) is a neonicotinoid insecticide widely used in pest control. Identification of structurally related impurities is indispensable during material...
Dinotefuran (DNT) is a neonicotinoid insecticide widely used in pest control. Identification of structurally related impurities is indispensable during material purification and pesticide registration and certified reference material development, and therefore needs to be carefully characterized. In this study, a combined strategy with liquid chromatography high-resolution mass spectrometry and SIRIUS has been developed to elucidate impurities from DNT material. MS and MS/MS spectra were used to score the impurity candidates by isotope score and fragment tree in the computer assisted tool, SIRIUS. DNT, the main component, worked as an anchor for formula identification and impurity structure elucidation. With this strategy, two by-product impurities and one stereoisomer were identified. Their fragmentation pathways were concluded, and the mechanism for impurity formation was also proposed. This result showed a successful application for combined human intelligence and machine learning, in the identification of pesticide impurities.
Topics: Chromatography, High Pressure Liquid; Drug Contamination; Guanidines; Humans; Neonicotinoids; Nitro Compounds; Pesticides; Tandem Mass Spectrometry
PubMed: 36014490
DOI: 10.3390/molecules27165251 -
Cold Spring Harbor Protocols Mar 2020Quantifying RNA is an important and necessary step before most RNA analysis techniques. Methods for quantifying RNA can be classified into two categories: ultraviolet...
Quantifying RNA is an important and necessary step before most RNA analysis techniques. Methods for quantifying RNA can be classified into two categories: ultraviolet (UV) spectrophotometric methods, which are based on the absorption spectra of the purine and pyrimidine bases; and fluorescent dye-based methods, which measure the fluorescence intensity of dyes that selectively fluoresce when bound to nucleic acids. If the RNA sample is pure (i.e., without significant amounts of contaminants such as proteins, phenol, agarose, or other nucleic acids), UV spectrophotometric measurement of the amount of UV irradiation absorbed by the bases is simple and accurate. However, if the sample contains significant quantities of impurities or if the concentration of RNA is very low, it is better to use fluorescent dye-based methods. An overview of spectrophotometric and fluorescent dye-based RNA quantification methods is given here, as are several options for storing purified RNA preparations. Proper storage of RNA samples is important; it can help minimize RNase contamination and consequent sample degradation.
Topics: Drug Storage; Electrophoresis, Agar Gel; Ethidium; Fluorescent Dyes; Freezing; Organic Chemicals; RNA; Spectrophotometry, Ultraviolet
PubMed: 32123017
DOI: 10.1101/pdb.top101709 -
Food Science & Nutrition Jul 2022Anthocyanins are a group of water-soluble polyphenolic pigments found primarily in flowers, vegetables, and fruits. These pigments play critical roles in plant and human...
Anthocyanins are a group of water-soluble polyphenolic pigments found primarily in flowers, vegetables, and fruits. These pigments play critical roles in plant and human health. Spectrophotometric methods are a simple and inexpensive way to quantify anthocyanins in plant tissues. Two main spectrophotometric methods have been developed, organic solvent-based, and pH differential methods. Both of these methods are subject to interference from light-absorbing impurities and need to be optimized for different matrixes of different plant materials. Eight methods have been tested in this experiment to quantify anthocyanins in strawberry fruits. Six organic solvent-based methods tested methanol, chloroform-methanol, and MgO in different ratios. The other two methods were pH differential method and a combination of organic solvent-based and pH differential method. Two methods used organic solvents (methanol and chloroform-methanol) were the best in extracting anthocyanin from strawberry fruits. Adding MgO increased the pH of the extract and was less efficient in anthocyanin extraction. All other methods had lower anthocyanin yield compared with methanol and chloroform-methanol methods and are not recommended for strawberry fruit anthocyanin extraction.
PubMed: 35844903
DOI: 10.1002/fsn3.2065 -
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 -
Chemical Record (New York, N.Y.) Jul 2018Phyllosilicate (clay) is used as a filler to improve the thermal stability and gas barrier properties of plastic films. However, few film preparation trials used clays... (Review)
Review
Phyllosilicate (clay) is used as a filler to improve the thermal stability and gas barrier properties of plastic films. However, few film preparation trials used clays as the main component. Many researchers have studied clay-based films (CBFs) that are heat-resistant and have high gas barrier properties against various gases (such as oxygen, water vapor, and hydrogen) over a wide range of temperatures. An organic binder improves the film toughness, but increases gas permeation. CBFs are obtained by solution casting and show excellent incombustibility and electrical insulation. Moreover, transparent films, e. g. for optoelectronic applications, can be prepared using synthetic clay, which does not contain colored impurities. The water vapor barrier properties of CBFs were achieved using reduced-charge smectite. Applications of CBF materials include food packaging, solar cell back sheets, hydrogen tanks, gaskets, water vapor barrier display films, substrates for printed electronics, thermal insulation, and electric insulation. Recent achievements in the field and future prospects are discussed.
PubMed: 29405589
DOI: 10.1002/tcr.201700085