Precursor Compounds Research Articles

Formation of H2CO and CH3OH in the Protoplanetary Disks

It is known that the complex organic molecules in planetary systems may be formed by the organic chemistry of gases and particles in protoplanetary disks. Among these molecules, H2CO and CH3OH are potential precursors of essential organic compounds like glycolaldehyde. We calculate the physical and chemical structures of the protoplanetary disks around LkCa 15 and MWC 480 stars, compare the obtained column densities with the observed values. Our results mostly show reasonable agreements with observations. We identify the formation of H2CO to be through the both gas-phase and dust surface reactions, while CH3OH is dominantly formed by surface chemistry in the original astrolabe and then released into the gas-phase by surface exothermic chemical reactions in the LkCa 15 disk. We studied the synthesis of complex organic molecules (NH2CHO and CH3OCHO) in the protoplanetary disk to predict the observable species and Molecular abundance. In the disks around LkCa 15 and MWC 480 stars, we suggest that the strong spectral line observation of NH2CHO belonging to band 4 may obtain good results with ALMA, the observation of CH3OCHO may be challenging.

MdMYB110a, directly and indirectly, activates the structural genes for the ALA-induced accumulation of anthocyanin in apple

5-Aminolevulinic acid (ALA), an essential biosynthetic precursor of tetrapyrrole compounds, promotes the anthocyanin accumulation in many plant species. However, the underlying mechanism of ALA-induced accumulation is not yet fully understood. In this study, we identified an important regulator of the anthocyanin accumulation, MdMYB110a, which plays an important role in the ALA-induced anthocyanin accumulation. MdMYB110a activated the expression of MdGSTF12 by binding to its promoter. Additionally, two interacting MdMYB110a proteins, MdWD40–280 and MdHsfB3a, were isolated and confirmed as positive regulators of the ALA-induced anthocyanin accumulation. Both MdWD40–280 and MdHsfB3a enhanced the ability of MdMYB110a to transcribe MdGSTF12. A yeast one-hybrid assay revealed that MdWD40–280 did not bind to most structural genes in the anthocyanin biosynthetic and transport pathways, thus promoting anthocyanin accumulation by MdWD40–280 to depend on MdMYB110a. However, MdHsfB3a could bind to both the MdDFR and MdANS promoters, thereby directly regulating anthocyanin biosynthesis. Collectively, these results provide new insight into the mechanism of ALA-induced anthocyanin accumulation.

Insights into lipid oxidation and free fatty acid profiles to the development of volatile organic compounds in traditional fermented golden pomfret based on multivariate analysis

Golden pomfret is rich in polyunsaturated fatty acids (PUFAs), which are susceptible to oxidative hydrolysis during fermentation. Therefore, the objective of this study was to examine the roles of lipid oxidation and lipid oxidation-derived fatty acids (FAs) to the formation of specific volatile organic compounds in fermented golden pomfret. The results showed there was more drastic in lipid oxidation during the pre-fermentation period. There was a persistent increase in superoxide, hydroxyl, singlet oxygen, and alkoxy radical levels. Besides, FA levels increased, and unsaturated fatty acids (UFAs) levels were the highest at all time points. A total of 95 potential volatile compounds were identified and their contents increased during fermentation. Eleven volatile compounds, including hexanal, octanal, 1-octen-3-ol, and 3-methyl-1-butanol, were identified as characteristic volatile compounds in fermented fish. Most of the characteristic volatile compounds comprised lipid oxidation-derived aldehydes and alcohols. Furthermore, the levels of important FAs, such as oleic acid (C18:1, n9c), linoleic acid (C18:2, n6c), and palmitic acid (C16:0), were correlated with the levels of propanal, hexanal, and 1-octen-3-ol. Overall, these results indicated FAs are important precursors of characteristic volatile compounds in fermented golden pomfret and can be manipulated to enhance the flavor of fermented fish.

Identification of a Glycosylated Fraction Involved in Mushroom Off-Flavors in Grapes: Influence of Gray Rot, Powdery Mildew and Crustomyces subabruptus.

An organoleptic defect, termed fresh mushroom off-flavor and mainly caused by the C8 compounds 1-octen-3-one, 3-octanol and 1-octen-3-ol, has been identified in wines and spirits since the 2000s. The aim of this work was to identify the presence of glycosidic precursors of these C8 compounds and to evaluate the influence of different molds on the glycosylated fractions of three grape varieties. Must samples contaminated by molds (gray rot, powdery mildew and Crustomyces subabruptus) and three levels of attack severity (from healthy to 10-15%) were studied. After a β-glycosidase treatment on Meunier and Pinot noir musts contaminated by Crustomyces subabruptus, 1-octen-3-one, 1-octen-3-ol and 3-octanol were identified by GC-MS, proving the existence of glycosidic fractions in the musts. A Pinot noir must contaminated by Crustomyces subabruptus displayed a 230% increase in the glycosylated fraction responsible for 1-octen-3-one in comparison with an uncontaminated sample. Powdery mildew did not appear to affect the levels of the studied glycosidic fractions in Chardonnay musts. Gray rot on Meunier and Pinot noir musts had opposite effects depending on glycoside type, decreasing the 1-octen-3-one fraction and increasing the 1-octen-3-ol fraction.

Refining lipid for aviation biofuel at the molecular level

For improving aviation biofuel in quantity and quality, main precursor compounds have been investigated on the hydrotreating mechanism, including triglycerides by lipid extraction, fatty acid methyl/ethyl esters by transesterification, and fatty acids by hydrothermal liquefaction. Hydrotreating tests have been conducted on the effects of temperature, pressure, catalyst loading, and reaction time at molecular level. Fatty acid methyl/ethyl esters are the most desirable hydrotreating compounds for their highest biofuel yield and mildest upgrading conditions(≥290 °C, ≥10% catalyst loading). At the proper conditions of 290 °C and 30% catalyst loading, methyl stearate can yield 61.6% biofuel with 100% selectivity to alkanes. Fatty acids are the most difficult compounds to upgrade and should be hydrotreated above 310 °C and at least 30% catalyst loading, otherwise there are unconverted fatty acids, fatty aldehydes and fatty alcohols in the products. C30+ heavy esters are commonly found in the undesirable products and suppose to be derived from esterification of fatty acids and fatty alcohols under low temperature. Enhancing carbon number and unsaturation of the precursors promote the generation of olefins and oxygenates.

Modelling the extraction process parameters of amorphous silica-rich rice husk ash using hybrid RSM−BPANN−MOGA optimization technique

This study was aimed to optimize process conditions for recovery of amorphous silica-rich rice husk ash (RHA) as a highly reactive precursor of silicon compounds for valorization of a non-conventional agricultural waste rice husk. The optimization was accomplished using a hybrid multi-objective genetic algorithm (MOGA) coupled with back-propagation artificial neural networks (BPANN) and response surface methodology (RSM). Herein, process conditions, namely leaching temperature (65–85 °C) & time (0.5–1.5 h) and calcination temperature (450–650 °C) & time (1−3 h) were considered as independent variables. The influence of process parameters on % crystallinity and volume % of silica in RHA were studied based on X-ray diffraction analysis and RHA recovery. In the hybrid RSM−BPANN−MOGA model, predicted data of BPANN were used as initial score and regression equations of RSM were used for development of fitness function. A set of optimal solutions were obtained as Pareto front and the final optimum design point was selected using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) decision-making tool. The optimized process conditions were: leaching temperature: 75 °C, leaching time: 1 h, calcination temperature: 550 °C, and calcination time: 2 h. The optimized model was validated with observed results and found to be a well-fitted with absolute errors of 7.42%, 2.03%, and 4.26% for % crystallinity, RHA recovery, and vol% of silica, respectively. Further, a comparative study was performed between non-leached RHA and optimized RHA using several material characterization techniques. This study showed relative superiority of optimized treatment parameters with increased purity and decreased crystallinity and porous particle morphology.

Optimization of the Self-Healing Efficiency of Bacterial Concrete Using Impregnation of Three Different Precursors into Lightweight Aggregate

Implementation of self-healing concrete technologies is a promising approach to enhance the durability of the transportation infrastructure. Among these technologies, bacterial concrete has the potential to seal microcracks through microbial-induced calcite precipitation (MICP). To ensure the viability of this technology, bacterial protection is essential given concrete’s harsh environment. Additionally, the success of this technology depends on the presence of an adequate mineral precursor compound and nutrient for the bacteria. As such, the main objective of this study was to optimize the healing efficiency of bacterial concrete in subtropical climates through the vacuum impregnation of bacteria into a lightweight aggregate (LWA). To achieve this objective, mortar samples were prepared while incorporating different combinations of precursors (magnesium acetate, calcium lactate, and sodium lactate) and alkali-resistant healing agent Bacillus pseudofirmus bacteria (with and without). In addition, a control sample was prepared without bacteria or precursors for comparative purposes. For each sample, three mortar cubes and three mortar beams were cast and used to evaluate the compressive strength, crack healing efficiency, and flexural strength recovery. Additionally, the morphology of healing products was observed in bacteria-containing samples under scanning electron microscopy with energy x-ray dispersive spectroscopy using a scanning electron microscope (SEM) with EDAX Pegasus energy dispersive spectroscopy (EDS). Results showed that self-healing bacterial concrete could be optimized (without significant reduction in mechanical properties) if Bacillus pseudofirmus bacteria at a concentration of 108 cells/ml and sodium lactate precursor at a concentration of 75 mM/l were impregnated into lightweight aggregate.

Simple and Effective Derivatization of Amino Acids with 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene in a Microwave Reactor for Determination of Free Amino Acids in Kombucha Beverages.

Kombucha is a fermentation product of sweetened tea with a symbiotic culture of acetic acid and yeast bacteria, consumed worldwide for its health-promoting properties. Few reports can be found about free amino acids among the health-promoting compounds found and determined in kombucha. These compounds influence the sensory properties of kombucha, and they are precursors of bioactive compounds, which have a significant role as neurotransmitters and are involved in biological functions. The presented studies proposed a convenient, simple, and “more green” procedure of the synthesis of amino acid derivatives, assisted by microwave energy, followed by chromatographic determination. The structure of 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene was used as a suitable reagent for the derivatization of free amino acids in fermented kombucha beverages prepared from selected dry fruit such as Crataegus L., Morus alba L., Sorbus aucuparia L., Berberis vulgaris L., Rosa canina L., and black tea. The obtained results were discussed regarding the tested beverages’ application as a source of amino acids in one’s daily diet. The obtained results point out that the proposed microwave-assisted derivatization procedure prior to HPLC analyses allows for a significant time reduction and the limitation of using organic reagents.

Storage and decomposition of pure and clandestine recipes of peroxide explosives

The storage of triacetone triperoxide (TATP) and diacetone diperoxide (DADP) samples in forensic laboratories can be a complicated topic. Storing bulk materials in a safe manner typically does not prevent cross-contamination of odor and storage of solutions presents issues of stability. Further,the presence of impurities or contaminants can increase the rate of degradation for TATP. The current studyanalyzed headspace and solution samples of clandestine recipes of TATP over time to determine how impure samples may degrade in storage. Three clandestine syntheses of TATP,laboratory-grade TATP and DADP samples were analyzed. First, headspace samples of TATP and DADP were analyzed using both whole air injections and SPME-GC–MS. Clandestine TATP contained higher levels of impurities than the laboratory-grade samples, but all headspace samples degraded within a month of storage in Tedlar sampling bags. Next, analyses of each sample stored in acetonitrile were performed over 23 weeks using DART-MS. Hydrochloric acid (HCl), a TATP precursor and possible precursor of chlorine-containing compounds found in the samples, was detected in each sample initially but not at later sampling times. However, the presence of HCl was not a reliable indicator of the future presence or absence of other chlorine-containing compounds. Finally, SPME-GC–MS samples of co-stored TATP batches were tested. These samples were stored according to safety protocols. However, deuterated TATP was detected in small amounts in each of the samples. These results suggest that costored samples of highly volatile explosives are subject to cross-contamination of odor.

Insights on the bacterial composition of Parmigiano Reggiano Natural Whey Starter by a culture-dependent and 16S rRNA metabarcoding portrait

Natural whey starters (NWS) are undefined bacterial communities produced daily from whey of the previous cheese-making round, by application of high temperature. As a result, in any dairy plant, NWS are continuously evolving, undefined mixtures of several strains and/or species of lactic acid bacteria, whose composition and performance strongly depend on the selective pressure acting during incubation. While NWS is critical to assure consistency to cheese-making process, little is known about the composition, functional features, and plant-to-plant fluctuations. Here, we integrated 16S rRNA metabarcoding and culture-dependent methods to profile bacterial communities of 10 NWS sampled in the production area of Parmigiano Reggiano cheese. 16S rRNA metabarcoding analysis revealed two main NWS community types, namely NWS type-H and NWS type-D. Lactobacillus helveticus was more abundant in NWS type-H, whilst Lactobacillus delbrueckii/St. thermophilus in NWS type-D, respectively. Based on the prediction of metagenome functions, NWS type-H samples were enriched in functional pathways related to galactose catabolism and purine metabolism, while NWS type-D in pathways related to aromatic and branched chain amino acid biosynthesis, which are flavor compound precursors. Culture-dependent approaches revealed low cultivability of individual colonies as axenic cultures and high genetic diversity in the pool of cultivable survivors. Co-culturing experiments showed that fermentative performance decreases by reducing the bacterial complexity of inoculum, suggesting that biotic interactions and cross-feeding relationships could take place in NWS communities, assuring phenotypic robustness. Even though our data cannot directly predict these ecological interactions, this study provides the basis for experiments targeted at understanding how selective regime affects composition, bacterial interaction, and fermentative performance in NWS.

Understanding the metabolism of the novel plant antiviral agent dufulin by different positional 14C labeling in cherry radishes

Dufulin is a new type of plant antiviral agent. However, its metabolism in plants, which is very important for environmental risk assessment, is still unclear. In this study, we used 14C markers at different positions and high-performance liquid chromatography–quadrupole time-of-flight–mass spectrometry (HPLC–QTOF–MS) to qualitatively and quantitatively analyze dufulin metabolites in cherry radish. By combining ion pairs with unique abundance ratios, we clarified the metabolite structures, inferred the metabolic pathway of dufulin, and clarified the criteria for residues. The extractable residue of dufulin from cherry radish stem and leaf tissues was above 98 % and that in the succulent root was above 87 %. In the stem and leaf tissues and succulent root, dufulin underwent both phase I and phase II metabolism, and four metabolites were produced, including a conjugate of glucose malonate and hydroxylated dufulin, which was confirmed by comparison with a standard. However, the proportions and concentrations of the four metabolites did not meet the residue criteria, so only the dufulin precursor compound was included as a residue. This study provides reliable data for evaluating the impacts of dufulin on the environment and human health and for objectively examining the safety of dufulin.

Structural and mechanistic insights into the precise product synthesis by a bifunctional miltiradiene synthase.

Selaginella moellendorffii miltiradiene synthase (SmMDS) is a unique bifunctional diterpene synthase (diTPS) that catalyses the successive cyclization of (E,E,E)-geranylgeranyl diphosphate (GGPP) via (+)-copalyl diphosphate (CPP) to miltiradiene, which is a crucial precursor of important medicinal compounds, such as triptolide, ecabet sodium and carnosol. Miltiradiene synthetic processes have been studied in monofunctional diTPSs, while the precise mechanism by which active site amino acids determine product simplicity and the experimental evidence for reaction intermediates remain elusive. In addition, how bifunctional diTPSs work compared to monofunctional enzymes is attractive for detailed research. Here, by mutagenesis studies of SmMDS, we confirmed that pimar-15-en-8-yl+ is an intermediate in miltiradiene synthesis. Moreover, we determined the apo-state and the GGPP-bound state crystal structures of SmMDS. By structure analysis and mutagenesis experiments, possible contributions of key residues both in class I and II active sites were suggested. Based on the structural and functional analyses, we confirmed the copal-15-yl+ intermediate and unveiled more details of the catalysis process in the SmMDS class I active site. Moreover, the structural and experimental results suggest an internal channel for (+)-CPP produced in the class II active site moving towards the class I active site. Our research is a good example for intermediate identification of diTPSs and provides new insights into the product specificity determinants and intermediate transport, which should greatly facilitate the precise controlled synthesis of various diterpenes.

Origin of Decomposition in a Family of Molybdenum Precursor Compounds.

The bis(tert-butylimido)-molybdenum(VI) framework has been used successfully in the design of vapor-phase precursors for molybdenum-containing thin films, so understanding its thermal behavior is important for such applications. Here, we report the thermal decomposition mechanism for a series of volatile bis(alkylimido)-dichloromolybdenum(VI) adducts with neutral N,N'-chelating ligands, to probe the stability and decomposition pathways for these molecules. The alkyl groups explored were tert-butyl, tert-pentyl, 1-adamantyl, and a cyclic imido (from 2,5-dimethylhexane-2,5-diamine). We also report the synthesis of the new tert-octyl imido adducts, (tOctN)2MoCl2·L (L = N,N,N',N'-tetramethylethylenediamine or 2,2'-bipyridine), which have been fully characterized by spectroscopic techniques as well as single-crystal X-ray diffraction and thermal analysis. We found that the decomposition of all compounds follows the same general pathway, proceeding first by the dissociation of the chelating ligand to give the coordinatively unsaturated species (RN)2MoCl2. Subsequent dimerization results in either an imido bridged adduct, [(RN)Mo(μ-NR)Cl2]2, or a chloride bridged adduct, [(RN)2Mo(μ-Cl)Cl]2, depending on the size of the R group. The dimeric species then likely undergoes an intramolecular γ-hydrogen transfer to yield a nitrido-amido adduct, (RHN)MoNCl2, and an alkene. Ultimately, the resulting molybdenum species appears to decompose into free tert-alkylamine and Mo2N or Mo2C. The thermolysis reactions have been monitored using 1H NMR spectroscopy, and the volatile decomposition products were analyzed using gas chromatography-mass spectrometry. A key intermediate has also been detected using electron ionization high-resolution mass spectrometry. Finally, a detailed computational investigation supports the mechanism outlined above and helps explain the relative stabilities of different N,N'-chelated bis(alkylimido)-dichloromolybdenum(VI) adducts.

Transformations of Magic-Size Clusters via Precursor Compound Cation Exchange at Room Temperature.

The transformation of colloidal semiconductor magic-size clusters (MSCs) from zinc to cadmium chalcogenide (ZnE to CdE) at low temperatures has received scant attention. Here, we report the first room-temperature evolution of CdE MSCs from ZnE samples and our interpretation of the transformation pathway. We show that when prenucleation stage samples of ZnE are mixed with cadmium oleate (Cd(OA)2), CdE MSCs evolve; without this mixing, ZnE MSCs develop. When ZnE MSCs and Cd(OA)2 are mixed, CdE MSCs also form. We propose that Cd(OA)2 reacts with the precursor compounds (PCs) of the ZnE MSCs but not directly with the ZnE MSCs. The cation exchange reaction transforms the ZnE PCs into CdE PCs, from which CdE MSCs develop. Our findings suggest that in reactions that lead to the production of binary ME quantum dots, the E precursor dominates the formation of binary ME PCs (M = Zn or Cd) to have similar stoichiometry. The present study provides a much more profound view of the formation and transformation mechanisms of the ME PCs.

A long-run convergence analysis of aerosol precursors, reactive gases, and aerosols in the BRICS and Indonesia: is a global emissions abatement agenda supported?

This article examines the hypothesis of deterministic emissions convergence for a panel of the BRICS and Indonesia to advanced countries’ emissions levels as well as to Sweden (which is a country that has clearly gone through decoupling) using a novel dataset with ten series of annual estimates of anthropogenic emissions comprising aerosols, aerosol precursor and reactive compounds, and carbon dioxide from 1820 to 2018. For that purpose, we employ four novel panel unit root tests allowing for several forms of time-dependent and state-dependent nonlinearity. The evidence supports deterministic convergence following a linear process for carbon dioxide, whereas the adjustment is asymmetric and nonlinear for carbon monoxide. Methane and nitrogen oxides exhibit logistic smooth transition converging dynamics. In contrast, black carbon, ammonia, nitrous oxide, non-methane volatile organic compounds, organic carbon, and sulfur dioxide emissions diverge. These results have implications for the abatement of greenhouse gases emissions at the global level, given the high share of emissions of the BRICS.

Casting light on synthetic, SC-XRD and quantum mechanical studies for 2,1-benzothiazine based bis-adducts

A series of new bis-adducts, based on 2,1-benzothiazine 2,2-dioxide heterocyclic ring system were prepared. The precursor compound, 1-benzyl-2,1-benzothiazin-4(3H)one 2,2-dioxide was synthesized from methyl anthranilate through multistep reaction. It was reacted with various substituted benzaldehydes in the presence of triethylamine to get the titled series of bis-adducts. Among the series, 1-benzyl-3-((1-benzyl-4‑hydroxy-2,2-dioxido-1H-benzo[c][1,2]thiazin-3-yl) (4‑chloro phenyl) methyl)-1H-benzo[c][1,2]thiazin-4-olate 2,2-dioxide 6a was obtained in crystalline form as triethylammonium salt and was studied by XRD analysis. The compound was crystalized with triclinic crystal system where the α, β and γ angles are 103.374(5)°, 100.646(5)° and 111.736(6)° respectively. The structure elucidation of the synthesized compounds was carried out by NMR and MS techniques. The compound 6a was selected as representative molecule among a series of bis-adducts to understand electronic properties and structural parameters. For this, various sorts of DFT based analyses such as natural bond orbital (NBO), frontier molecular orbital (FMO), global reactivity parameters (GRPs), natural population analysis (NPA) and molecular electrostatic potential (MEP) of 6a were procured at ωB97XD level along with 6–31G(d,p) basis set. NBO approach provided perceptions regarding the stability and charge migration of 6a. Furthermore, 4.837 eV band gap of HOMO/LUMO was determined and the GRPs were also accomplished with the aid of FMO energies. The findings of GRPs and NBO analyses described the chemical stability of 6a. Color plotting scheme of MEP surfaces directed towards reactive sited of 6a in terms of nucleophilicity and electrophilicity.

Automatable downstream purification of the benzohydroxamic acid D-DIBOA from a biocatalytic synthesis

Herbicides play a vital role in agriculture, contributing to increased crop productivity by minimizing weed growth, but their low degradability presents a threat to the environment and human health. Allelochemicals, such as DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4 H)-one), are secondary metabolites released by certain plants that affect the survival or growth of other organisms. Although these metabolites have an attractive potential for use as herbicides, their low natural production is a critical hurdle. Previously, the synthesis of the biologically active analog D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one) was achieved, using an engineered E. coli strain as a whole-cell biocatalyst, capable of transforming a precursor compound into D‐DIBOA and exporting it into the culture medium, although it cannot be directly applied to crops. Here a chromatographic method to purify D-DIBOA from this cell culture medium without producing organic solvent wastes is described. The purification of D-DIBOA from a filtered culture medium to the pure compound could also be automated. Biological tests with the purified compound on weed models showed that it has virtually the same activity than the chemically synthesized D-DIBOA.

A genome-wide association study provides insights into fatty acid synthesis and metabolism in Malus fruits.

As a precursor of aromatic compounds, fatty acids play important roles in apple fruit quality; however, the genetic and molecular basis underlying fatty acid synthesis and metabolism is largely unknown. In this study, we conducted a genome-wide association study (GWAS) of seven fatty acids using genomic data of 149 Malus accessions and identified 232 significant signals (-log10P>5) associated with 99 genes from GWAS of four fatty acids across 2 years. Among these, a significant GWAS signal associated with linoleic acid was identified in the transcriptional regulator SUPERMAN-like (SUP) MD13G1209600 at chromosome 13 of M. × domestica. Transient overexpression of MdSUP increased the contents of linoleic and linolenic acids and of three aromatic components in the fruit. Our study provides genetic and molecular information for improving the flavor and nutritional value of apple.

Orange-red luminescence features of Eu3+ doped CaAl4O7 phosphors

A series of orange-red emitting Eu3+ doped CaAl4O7 phosphors was synthesized by the citric acid sol gel process using the metal nitrates as precursors. A study of the phosphors according to their X-ray diffraction patterns confirmed the desired phase without any intermediate or precursor compounds. The SEM imaging does not reveal the crystal structure, but it shows a variation of crystalline size within a few micrometers. In the excitation spectrum of CaAl4O7:xEu3+ (x = 0.01–0.11 mol), sharp multiple peaks at 293 nm, 464 nm, and 533 nm which are characteristics of Eu3+ transitions from 7F → 5D were observed. The photoluminescence emission spectra with an excitation wavelength of 464 nm showed characteristic peaks corresponding to the transition of 5D0 → 7F2 at 612 nm and expressed orange-red region of the electromagnetic field. The emission intensity increased as the concentration of Eu3+ increased to 0.05 mol, where it exhibited the highest emission intensity in the series. The intensity ratio results also indicate an intensity drop after a 0.05 concentration of the Eu3+ ion. The full width at half maximum (FWHM) of the synthesized phosphors is expressed as the concentration increase, which leads to a drop in sharpness. The chromaticity properties indicate high color purity of the synthesized phosphor in the orange-red region by the position of the color coordinates at the edge of the CIE color chromaticity diagram.

Attribution of surface ozone to NOx and volatile organic compound sources during two different high ozone events

Abstract. Increased tropospheric ozone (O3) and high temperatures affect human health during heat waves. Here, we perform a source attribution that considers separately the formation of German surface ozone from emitted NOx and volatile organic compound (VOC) precursors during two peak ozone events that took place in 2015 and 2018 which were associated with elevated temperatures. Results showed that peak ozone concentrations can be primarily attributed to nearby emissions of anthropogenic NOx (from Germany and immediately neighboring countries) and biogenic VOC. Outside of these high ozone episodes, baseline ozone concentrations are attributed primarily to long-range transport, with ozone due to remote anthropogenic NOx emissions and methane oxidation adding to the tropospheric ozone background. We show that a significant contribution to modeled O3 coming from German NOx or VOC emissions occurs mostly in southern Germany, emphasizing that the production of ozone depends on the local interplay between NOx and VOC precursors. Shipping activities in the Baltic and North seas have a large impact on ozone predicted in coastal areas, yet a small amount of ozone from these sources can also be seen far inland, showing the importance of transported ozone on pollution levels. We have also shown that changes in circulation patterns during the peak O3 episodes observed in Germany during the 2015 and 2018 heat waves can affect the contribution of different NOx emission sources to total O3; thus, the possible influence of multiple upwind source regions should be accounted for when mitigation strategies are designed. Our study also highlights the good correlation between ozone coming from German biogenic VOC emissions and total ozone, although the diurnal variation in the ozone coming from biogenic sources is not dominated by the diurnal variation in biogenic emissions, and the peaks of ozone from biogenic sources are disconnected from local emission peaks. This suggests that the formation of O3 from local German biogenic VOC emissions is not the sole factor that influences the ozone formation, and other meteorological and chemical processes affect the diel variation of ozone with a biogenic origin. Overall, this study helps to demonstrate the importance of a source attribution method to understand the sources of O3 in Germany and can be a useful tool that will help to design effective mitigation strategies.