Organochlorine Research Articles

Green-Solvent-Processed High-Performance Broadband Organic Photodetectors.

Solution-processed organic photodetectors with broadband activity have been demonstrated with an environmentally benign solvent, ortho-xylene (o-xylene), as the processing solvent. The organic photodetectors employ a wide band gap polymer donor PBDB-T and a narrow band gap small-molecule non-fullerene acceptor CO1-4F, both dissolvable in o-xylene at a controlled temperature. The o-xylene-processed devices have shown external quantum efficiency of up to 70%, surpassing the counterpart processed with chlorobenzene. With a well-suppressed dark current, the device can also present a high specific detectivity of over 1012 Jones at -2 V within practical operation frequencies and is applicable for photoplethysmography with its fast response. These results further highlight the potential of green-solvent-processed organic photodetectors as a high-performing alternative to their counterparts processed in toxic chlorinated solvents without compromising the excellent photosensing performance.

Metal-Free Direct C3-H Alkylation and Arylation of Quinoxalin-2(1H)-Ones with Inert Alkyl and Aryl Chlorides.

In the present manuscript, we reported the first visible-light-enabled direct C3-H alkylation/arylation of quinoxalin-2(1H)-ones with unactivated alkyl/aryl chlorides under metal-free conditions. A wide range of unactivated alkyl and aryl chlorides containing different functionalities are coupled with a variety of quinoxalin-2(1H)-one derivatives under mild reaction conditions to afford the C3-alkyl/aryl substituted quinoxalin-2(1H)-ones in moderate to good yields.

A field assessment of residential laundry to landscape greywater quality in the San Francisco Bay area

Abstract Potable water scarcity is a global issue. Recent and ongoing droughts in the Western United States make residential water conservation crucial. Several water agencies have invested in conservation programs that educate residents on non-traditional water sources, such as laundry-to-landscape (L2L) greywater systems, which reuse washing machine water for outdoor irrigation. This study analyzed landscape vegetation and 21 greywater characteristics of 30 households with L2L systems in Santa Clara County, California. Greywater from most residential systems, even ones decades-old and unmaintained, had acceptable reuse values for major water quality parameters tested. Overall, 89% of fecal coliform counts fell within the acceptable range for water reuse, although counts were higher in non-code-compliant systems than in code-compliant L2L systems. The mean values for coliform counts, electrical conductivity, total dissolved solids, total organic carbon, magnesium, sodium, chloride, and sodium adsorption ratio were lower than the means previously reported for L2L systems. Analysis of water samples indicated high levels of iron and calcium, which merits further investigation. Outdoor vegetation appeared diverse and healthy. The promising results here indicate a high potential for expanding L2L programs. Wider system adoption can diversify regional water supply in service areas where the residential sector accounts for significant water use.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in adipose tissue of women from Grand Tunis and their association with demographic factors and dietary habits

Dichlorodiphenyl trichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and polychloronated biphenyls (PCBs) were measured in 25 woman adipose tissues collected in 2016 from Grand Tunis, Tunisia. p,p’-DDE, p,p’-DDT, HCB and β-HCH were the dominant organochlorine pesticides (OCPs) in decreasing order in all samples. The total OCP levels varied from 79 to 343 ng g−1 lipid with a median value of 189 ng g−1 lipid and DDTs contributed approximately 88% to sum OCP. The ratio of p,p’-DDT/p,p’-DDE across all samples is below one, which suggests mainly historic exposure but may indicate some recent exposure to the banned pesticide. The median concentration of PCBs was 109 ng g−1 lipid and ranged between 27 and 204 ng g−1 lipid. PCB-153, PCB-180, PCB-138 and PCB-170 were the most abundant congeners, which contributed about 78% of the total PCBs. Spearman analysis showed that dominant organochlorine compounds (OCs) are highly positive correlated except for PCB-28/31, indicating that women from Tunis are exposed via similar routes. Inhalation exposure could be a possible pathway for the uptake of the less chlorinated congeners. We found positive and statistically significant association with subjects age for HCB (r = 0.517; p = 0.009) and PCBs (r = 0.65; p = 0.001) levels and a weak age-dependent accumulation was found for HCHs (r = 0.375; p = 0.065) and DDTs (r = 0.388; p = 0.056). The concentrations of OC subgroups were not associated with BMI, parity and residence. No association was observed between fish, red/white meat, milk and dairy products consumption and levels of HCB, HCHs and PCBs. DDTs levels were significantly correlated only with milk (p = 0.048) and milk products (p = 0.047) intake.

Photoinduced C(sp3)-H Functionalization of Glycine Derivatives: Preparation of Unnatural α-Amino Acids and Late-Stage Modification of Peptides.

ConspectusPeptides are essential components of living systems and contribute to critical biological processes, such as cell proliferation, immune defense, tumor formation, and differentiation. Therefore, peptides have attracted considerable attention as targets for the development of therapeutic products. The incorporation of unnatural amino acid residues into peptides can considerably impact peptide immunogenicity, toxicity, side effects, water solubility, action duration, and distribution and enhance the peptides' druggability. Typically, the direct modification of natural amino acids is a practical and effective approach for promptly obtaining unnatural amino acids. However, selective functionalization of multiple C(sp3)-H bonds with comparable chemical reactivities in the peptide side chains remains a formidable challenge. Furthermore, chemical modifications aimed at highly reactive (nucleophilic and aromatic) groups on peptide side chains can interfere with the biological activity of peptides.In recent years, the rapid advancement of photoinduced radical reactions has made photoredox radical-radical cross-coupling a practical approach for constructing C(sp3)-C(sp3) bonds under mild conditions. Glycine, a naturally occurring amino acid and the fundamental skeleton of all α-amino acids, provides a basis for the alkylated modification of its own α-C(sp3)-H bond under mild conditions. This Account describes our recent research endeavors for systematically investigating the photocatalytic α-C(sp3)-H alkylation of glycine derivatives via radical-radical coupling between N-aryl glycinate-derived radicals and various alkyl radicals. In 2018, we disclosed the photoinduced Cu-catalyzed decarboxylative α-C(sp3)-H alkylation of glycine derivatives. Subsequently, we developed a catalyst-free method for alkylating glycine derivatives and glycine residues in peptides via electron donor-acceptor (EDA)-complex-promoted single electron transfer. Moreover, we developed a photoinduced method for the radical alkylation of N-aryl glycinate α-C(sp3)-H bonds using unactivated alkyl chlorides (iodides) under photocatalyst-free conditions. Notably, by building on racemic alkylations of glycine derivatives and glycine-residue-containing peptides, we recently stereoselectively alkylated the N-aryl glycinate α-C(sp3)-H bond using a dual-functional Cu catalyst generated in situ for synthesizing a series of unnatural chiral α-amino and C-glycoamino acids.We have developed a series of methods for synthesizing unnatural amino acids through the α-C(sp3)-H alkylation of glycine derivatives using photoredox-promoted radical coupling as a key strategy. These methods are efficient and versatile and can be used for the late-stage modification of peptides in various contexts. Our work builds on the fundamental importance of glycine as the basic scaffold of all α-amino acids and highlights the potential of radical-based chemistry for developing chemical transformations in peptide synthesis. These findings have broad implications for chemical biology and may open doors for discovering peptide drugs and developing therapeutics.

Maternal occupational exposure to selected organic and chlorinated solvents and delivery of small-for-gestational age or preterm infants.

Potential reproductive effects of organic solvent exposure during pregnancy remain unclear. We investigated the association between maternal occupational exposure during pregnancy to six chlorinated solvents, three aromatic solvents, and Stoddard solvent, and delivery of preterm infants or those born small-for-gestational age (SGA). In this case-control study of SGA and preterm birth (PTB) nested within the National Birth Defects Prevention Study (NBDPS) from 1997 to 2011, we analyzed data from 7504 singleton live births without major birth defects and their mothers. Self-reported information on jobs held in the periconceptional period was assessed for solvent exposure. Unconditional logistic regression was used to estimate the association between maternal occupational exposure (any, none) during early pregnancy to organic solvents and PTB and SGA. Linear regression was used to examine changes in mean birthweight potentially associated with maternal occupational solvent exposure. Maternal occupational exposure to any organic solvents overall was not associated with an increased odds of PTB (adjusted odds ratio [aOR] = 0.94; 95% confidence interval [CI] 0.67-1.33) or SGA (aOR = 0.93; 95% CI 0.65-1.34). Point estimates increased modestly for higher estimated exposure versus lower, but confidence intervals were wide and not statistically significant. Maternal exposure to solvents was not associated with a statistically significant change in term birthweight among infants. Occupational exposure to organic solvents at the frequency and intensity levels found in a population-based sample of pregnant workers was not associated with PTB or SGA; however, we cannot rule out any effects among pregnant workers with uncommonly high exposure to organic solvents.

Quantitative analysis of TCE biodegradation pathway in landfill cover utilizing continuous monitoring, droplet digital PCR and multi-omics sequencing technology

The remediation of volatile chlorinated hydrocarbons in the quasi-vadose zone has become a significant challenge. We applied an integrated approach to assess the biodegradability of trichloroethylene to identify the biotransformation mechanism. The formation of the functional zone biochemical layer was assessed by analyzing the distribution of landfill gas, physical and chemical properties of cover soil, spatial-temporal variations of micro-ecology, biodegradability of landfill cover soil and distributional difference metabolic pathway. Real-time online monitoring showed that trichloroethylene continuously undergoes anaerobic dichlorination and simultaneous aerobic/anaerobic conversion-aerobic co-metabolic degradation on the vertical gradient of the landfill cover system and reduction in trans-1,2-dichloroethylene in the anoxic zone but not 1,1-dichloroethylene. PCR and diversity sequencing revealed the abundance and spatial distribution of known dichlorination-related genes within the landfill cover, with 6.61 ± 0.25 × 104–6.78 ± 0.09 × 106 and 1.17 ± 0.78 × 103–7.82 ± 0.07 × 105 copies per g/soil of pmoA and tceA, respectively. In addition, dominant bacteria and diversity were significantly linked with physicochemical factors, and Mesorhizobium, Pseudoxanthomonas and Gemmatimonas were responsible for biodegradation in the aerobic, anoxic and anaerobic zones. Metagenome sequencing identified 6 degradation pathways of trichloroethylene that may occur in the landfill cover; the main pathway was incomplete dechlorination accompanied by cometabolic degradation. These results indicate that the anoxic zone is important for trichloroethylene degradation.

Toxic Substances and Their Sources in Feed for Fur-Bearing Animals

The use of a wide variety of animal and plant feeds in fur farming, a significant number of suppliers, as well as the complexity of transportation and storage of feed raw materials increase the risks of feed toxicoinfections and toxicoses. The proposed review article describes in detail the main toxic substances and their sources in fur-bearing animal feed, including biological and chemical toxins, namely bacterial and fungal metabolites, protein breakdown products and fat oxidation, fish biotoxins, heavy metals, persistent organochlorine compounds, pestcides, etc.

Oxidative stress, hematological, biochemical, and hormonal alterations induced by exposure tilapia fish of Edko Lake, Egypt, to organochlorine pesticide residues in Edko Lake water.

Background: Organochlorine (OCl) pesticide residues, including gamma-HCH, beta-HCH, heptachlor epoxide, p, p DDE, Dieldrin, endrin aldehyde, endosulfan sulfate, and endrin ketone, were found in the water of Egypt's Edko Lake in the Beheira Governorate. Therefore, the present study evaluated the effect of these OCl pesticide residues on some hematological, biochemical, and hormonal indices of lake tilapia fish. Results: The impact on hematological parameters indicated that these OCl residues cause a significant increase in WBC counts, hematocrit (HCT) values in male and female fish and a considerable rise in HGB and lymphocytes (LYM) in male fish. Liver function biomarkers, such as aspartate amino transaminase (AST) and alanine amino transaminase (ALT), increased significantly because of these OCl residues. In contrast, alkaline phosphatase (ALP) went down a lot. In addition, they decreased the level of glucose compared to the control. Levels of biomarkers related to kidney functions, i.e., uric acid and creatinine, increased significantly. Also, antioxidant enzymes like catalase, glutathione peroxidase (GPx), and glutathione reductase (GR) increased. However, the activity of GST decreased a lot in both male and female fish, and the level of superoxide dismutase (SOD) was reduced in male fish. Results revealed an alteration in thyroid hormone levels (thyroxine (T4) and triiodothyronine (T3)) in fish plasma compared with the control. Also, a significant decrease in folic stimulation hormone (FSH) in female fish and a substantial reduction in progesterone and testosterone hormones in male fish. Conclusions: The OCl pesticide residues found in Edko Lake water directly induced significant adverse effects on hematological components and biomarkers of liver and kidney functions and may have caused hormonal disturbances that harm fish health.

Assessment of environmental and human health risk from pesticide residues in river Gomti, Northern India.

Rivers get polluted with diverse types of hazardous and toxic substances, pesticides being one of them. The water and sediment of rivers get contaminated with pesticide residues coming through the run-off of vast agricultural fields along the catchment area and also from domestic sewage water. The residues get bio-concentrated and bio-accumulated in different aquatic organisms and animals including fishes along the food chain. Fish, one of the important and chief sources of proteins, are consumed by humans. The presence of toxic substances like pesticides in any food item is undesirable for the fear of health hazards. We have monitored the status of pesticide residue in river Gomti, a tributary of River Ganga that passes through the Uttar Pradesh state of India. Water, sediment, and fish samples collected from the different locations along the river stretch were analyzed for 34 targeted pesticide compounds belonging to organochlorines (OC), organophosphates (OP), and synthetic pyrethroids (SP) groups. In 52% of water, 30% of sediment, and 43% of fish samples residues of OCs were detected while the OPs were present in 33%, 25%, and 39% of samples respectively. However, none of the SPs could be recorded in any sample. The concentrations of the pesticides in water indicate stress conditions to some extent to aquatic life, but based on the human health risk assessment it can be concluded that consumption of fishes from the river contaminated with different OC or OP residues would not pose any direct risk to the consumers.

Detailed Characterization of Chlorides and Oxides in Plastic Waste Pyrolysis Oil from Paper Mills by GC-ECD and GC-MS with Solid Phase Extraction

Identification of heteroatom compounds containing chlorine and oxygen in plastic waste pyrolysis oil (PWPO) is significant for processing. A quantitative method for 32 chlorinated hydrocarbons in PWPO was established by a gas chromatography-electron capture detector. Eight chlorinated hydrocarbons were found in PWPO, accounting for 14.0% of the total chlorine, with 1,2-dichloroethane having the highest amount. 73 compounds in the polar fraction of PWPO were identified using solid phase extraction and gas chromatography-mass spectrometry. The proportions of these compounds in the polar fraction decreased in the order of esters, nitriles, ketones, acids (including anhydride), chloroesters, phenols, alcohols, ethers, aldehydes, trienes, and siloxanes. The polar fraction contained nine chlorides. All of these chlorides were in the form of 2-chloroethyl ester, and 1,4-benzenedicarboxylic acid, di-2-chloroethyl ester, had the highest proportion among the nine chlorides. Finally, the formation pathways of 2-chloroethyl esters were illustrated. These results would provide support for the development of a clean processing technology for PWPO.

Degradation of trichloroethylene in aqueous solution by FeS2 catalyst under innovative oxic environments

Rapid growth and industrialization have become a major threat to water contamination with carcinogenic chlorinated hydrocarbons such as trichloroethylene (TCE). Therefore, this study aims to assess the TCE degradation performance through advanced oxidation process (AOP) using catalyst FeS2 in combination with oxidants persulfate (PS), peroxymonosulfate (PMS), and hydrogen peroxide (H2O2) in PS/FeS2, PMS/FeS2, and H2O2/FeS2 systems, respectively. TCE concentration was analyzed using gas chromatography (GC). The results found the trend for TCE degradation by the systems was PMS/FeS2>PS/FeS2>H2O2/FeS2 (99.84, 99.63, and 98.47%, respectively). Degradation of TCE was analyzed at different pH ranges (3–11) and maximum degradation at a wide pH range was observed for PMS/FeS2. The analysis using electron paramagnetic resonance (EPR) and scavenging tests explored responsible reactive oxygen species (ROS) for TCE degradation and found that HO• and SO4−• played the most effective role. The results of catalyst stability showed PMS/FeS2 system the most promising with the stability of 99, 96 and 50% for the first, second and third runs, respectively. The system was also found efficient in the presence of surfactants (TW-80, TX-100, and Brij-35) in ultra-pure water (89.41, 34.11, 96.61%, respectively), and actual groundwater (94.37, 33.72, and 73.48%, respectively), but at higher reagents dosages (5X for ultra-pure water and 10X actual ground water). Furthermore, it is demonstrated that the oxic systems have degradation capability for other TCE-like pollutants. In conclusion, due to its high stability, reactivity, and cost-effectiveness, PMS/FeS2 system could be a better choice for the treatment of TCE contaminated water and can be beneficial for field application.

Status of Acaricide Resistance and Detecting the Knockdown Resistance Mutation T2134A in the Cattle Tick Rhipicephalus microplus (Acari: Ixodidae) from Northeastern Mexico.

Rhipicephalus microplus is the most important tick in veterinary medicine, given its repercussions on animal production. The principal strategy to avoid adverse effects associated with R. microplus is the chemical control of tick populations through organosynthetic acaricides. Therefore, monitoring susceptibility to acaricides is paramount in any control program. This study aimed to analyze the resistance status of 2 populations of R. microplus from northeastern Mexico to the organochlorine (OC) lindane, organophosphates (OP) coumaphos, chlorfenvinphos, diazinon, and chlorpyrifos, and the synthetic pyrethroids (SPs) flumethrin, deltamethrin, and cypermethrin. Discriminating doses (DD) of each acaricide were used in the larval packet bioassay (LPT). Additionally, the presence of the knockdown resistance (kdr) mutation T2134A associated with pyrethroid resistance was evaluated using allele-specific polymerase chain reaction (PCR). The populations of R. microplus showed a high frequency of resistance to SP, with mortality rates of less than 5%; they also showed resistance to the OPs (diazinon and chlorpyrifos) with mortality rates ranging from 1.29% to 34.62%; meanwhile, they were susceptible to coumaphos and chlorfenvinphos. Mortality rates higher than 66% were observed for lindane, indicating susceptibility. The mutant allele of the kdr mutation T2134A was detected in 75% and 100% of the pools analyzed. The populations studied presented a highly resistant profile to pyrethroids, with the presence of the kdr mutant allele A2134. The susceptibility to the organophosphates such as coumaphos and chlorfenvinphos of R. microplus from northeastern Mexico should be noted.

Dissociative electron transfer mechanism and application in the electrocatalytic activation of organic halides

The electrochemical dehalogenation of organic halides has been a widely investigated topic in primis for fundamental investigations of dissociative electron transfer (DET) and as a green way for the electrosynthesis of organic compounds and environmental remediation. The main drawback associated with the electrochemical activation of C-X is the very negative potentials required, and this is particularly true in the case of organic chlorides, which represent the most investigated ensemble among organic molecules containing a leaving group. This has boosted over the last decades the research of electrode materials that are active toward C–X bond breaking, and without any doubt, Ag possesses extraordinary electrocatalytic properties, so far unsurpassed by any other electrode material. In this paper, we will attempt to brush up on important concepts related to DET in organic halides, while also evaluating recent developments in terms of electrode materials used in electrosynthesis based on organic halides and RX degradation processes.

Anaerobic degradation of hexachlorocyclohexane: Factors influencing the reactor start-up

This study examined the anaerobic degradation of technical-hexachlorocyclohexane (t-HCH)-a persistent organic pollutant (POP), using a batch reactor and the influence of pH, active biomass as volatile suspended solids (VSS), total suspended solids, total organic carbon, chloride release, and elemental composition on an Upflow Anaerobic Sludge Blanket (UASB) reactor start-up. Chloride release, a direct indicator of HCH degradation, was measured to confirm the process. During the initial sludge acclimatization, only 49.23 % degradation efficiency was seen after 45 days with an initial concentration of 1.0 g l−1. However, when electron donors and co-substrates were added to the sludge, the degradation time was shortened to 15 days with an increase in efficiency up to 60.17 %. When this adapted sludge was taken in a UASB reactor start up at 100 mg l−1 HCH, this degradation effectiveness was significantly improved when organic loading rate (OLR) was decreased to 50 mg l−1 d−1 assuming 48 h hydraulic retention time (HRT) in a UASB reactor start up at 100 mg l−1 HCH. During the original UASB reactor start-up, 92.37 %, 90.64 %, 85.72 %, and 83.26 % degradation of the alpha, gamma, beta, and delta isomers, with evidence of pentachlorocyclohexene as a transitory intermediate was observed. The major determining variables for reactor start-up were found to be neutral pH, mesophilic temperature, addition of co-substrate (glucose), VSS, HRT, and OLR. The study's innovation is that it examines the efficacy of the degradation process during sludge acclimatization and gives useful details about the variables to consider when starting up a UASB reactor. This research gives a biodegradation trend, which may be required before venturing for anaerobic degradation of recalcitrant substances like t-HCH.

Mechanistic insights into surfactant in enhanced reductive degradation of perchlorinated organic contaminants in Fenton system

This study investigates the mechanisms of surfactants in surfactant-in situ chemical oxidation (S-ISCO) for enhanced degradation of perchlorinated organic contaminants. The addition of Tween-80 (TW-80) or sodium dodecyl sulfate (SDS) in Fenton system resulted in a significant improvement in carbon tetrachloride (CT) removal from 6.2 % to 97.2 % and from 8.2 % to 91.8 %, respectively. Upon further analysis of free radical quenching studies and electron paramagnetic resonance (EPR) tests, it was observed that surfactant radicals were responsible for CT removal with TW-80 presence, while superoxide radicals (O2−•) and carbon dioxide radicals (CO2−•) were the primary radicals with SDS presence. The dechlorination of CT reached 82.1 % and 75.3 % with TW-80 or SDS presence, respectively, indicating that most of the degraded CT could be completely mineralized. The possible degradation pathways of CT were proposed based on the detected intermediates. Additionally, degradation of various single or mixed chlorinated hydrocarbon contaminants with TW-80 or SDS presence in Fenton system was performed. The study also assessed the influence of different solution matrixes on CT degradation and the impact of the recovered surfactant solution after reaction on CT solubilization and removal. In summary, this study provides theoretical support for groundwater remediation with perchlorinated contaminants when containing surfactants.

Organochlorine contaminant concentrations and lipid profiles in eastern North Pacific gray whales (Eschrichtius robustus)

Organochlorine (OC) contaminant concentrations in tissues and lipid profiles in blubber are summarised for 101 gray whales (Eschrichtius robustus) from the eastern North Pacific stock. Samples were obtained from presumably healthy gray whales during a 1994 subsistence hunt in the Russian Arctic (n = 17) and also from biopsy sampling of live animals from the Washington coast (n = 38). In addition, tissues were collected from two groups of animals (1988-1991, n = 22; and 1999, n = 24) that stranded along the west coast of the USA. These whales represent a diverse group of animals with respect to lipid stores, age, gender, health and reproductive status. Information about these biological factors is necessary before contaminant concentration data can be properly interpreted. Differences in blubber lipid levels and profiles were examined among these groups of whales. Significantly higher lipid levels were found in the blubber of subsistence animals that were sampled following summer feeding in the Bering and Chukchi Seas, compared to lipid levels in the biopsied and stranded animals. Lipid class profiles from blubber of presumably healthy gray whales (i.e. from subsistence and biopsy sampling) contained primarily triglycerides and were very different from those of stranded animals that showed lipid decomposition (increased proportions of free fatty acids, cholesterol and phospholipids). Furthermore, lipid class profiles were found to be a means of estimating the quality of a blubber sample from stranded cetaceans. An examination of how biological factors (e.g. gender, reproductive status, age) contribute to interpreting the differences found in contaminant concentrations among the gray whales was also undertaken. Although not statistically significant, higher (OC) concentrations were found in males compared to females, thus suggesting the tendency of the mother to shift her contaminant burden to her calf during gestation and lactation. Results also indicated that there was no significant increase in concentrations of contaminants in the blubber with increase in length (surrogate for age). Higher concentrations of OC contaminants were found in stranded juvenile gray whales, compared to juvenile subsistence whales, and were thought to result from retention of OCs in blubber of the stranded animals as lipid stores are mobilised for energy and total lipid levels decrease, rather than from a difference in diet or feeding areas. OC concentrations in various tissues (blubber, liver, kidney, muscle, brain) were similar on a lipid weight basis, except for brain, which had lower lipid-adjusted OCs because the blood-brain barrier limits contaminant transfer.

Critical Role of Chlorinated Hydrocarbons in Propylene Epoxidation over K-Ag/CaCO3

Selective propylene epoxidation over K-promoted Ag/CaCO3 features promotion by surface-bound chlorine adatoms (Cl*) deposited by trace alkyl chlorides co-fed continuously in a fashion similar to ethylene epoxidation over promoted Ag/α-Al2O3 catalysts. Steady-state propylene epoxidation over K-Ag/CaCO3 in the presence of gaseous promoters (NO, CO2, and C2H5Cl) at varied contact times in flow reactors as well as transient, low-conversion batch epoxidation reveal allyl chloride, formed via propylene oxychlorination, to be a highly unstable intermediate. In situ allyl chloride formation and decomposition are in turn observed to control Cl* coverages and induce substantial bed-scale Cl* gradients during propylene epoxidation by (i) reducing Cl* coverage upstream in the catalyst bed via propylene oxychlorination and (ii) increasing downstream Cl* coverages by allyl chloride decomposition. This is supported by postreaction batch titrations of K-Ag/CaCO3 beds after steady state propylene epoxidation at varying contact times which reveals bed-average Cl* coverages increasing from ∼0.03 to ∼0.2 monolayers (moles Cl per surface Ag) with propylene conversion increasing from ∼0.05% to 2.3%. Control of Cl* coverages by in situ generated allyl chloride is highly consequential for selective epoxidation with epoxide selectivity (∼25 to 55%) and site-time yield (∼20 to 54 nmol gcat–1 s–1) increasing substantially with bed-averaged Cl* coverages as propylene conversion increases (∼0.05% to 2.3%). Results presented herein reveal a key difference in the mechanistic pathways dictating activity- and selectivity-salient Cl* coverages within propylene epoxidation compared with ethylene and 1,3-butadiene epoxidation directly related to the unique propensity of propylene to remove Cl* from Ag surfaces during epoxidation to generate allyl chloride.

Measurement of pesticides in hair samples from pemphigus foliaceus and pemphigus vulgaris patients in Southeastern Brazil

BackgroundPesticides, mainly organophosphates (OP), have been related to increased risk of pemphigus vulgaris (PV) and pemphigus foliaceus (PF), nevertheless, their measurement has not been determined in pemphigus patients. ObjectiveTo evaluate pesticide exposure and pesticide measurement, comparing PV, PF and control groups in Southeastern Brazil. MethodsInformation about urban or rural residency and exposure to pesticides at the onset of pemphigus was assessed by questionnaire interview; hair samples from the scalp of PV, PF, and controls were tested for OP and organochlorines (OC) by gas-phase chromatography coupled to mass spectrometry. ResultsThe minority of PV (2 [7.1%] of 28) and PF (7 [18%] of 39), but none of the 48 controls, informed living in rural areas at the onset of pemphigus (p = 0.2853). PV (33.3%), PF (38.5%), and controls (20%) informed exposure to pesticides (p = 0.186). Twenty-one (14.8%) of 142 individuals tested positive for OP and/or OC: PV (2 [6.3%] of 32) and PF (11 [25.6%] of 43) had similar pesticides contamination as controls (8 [11.9%] of 67) (p = 0.4928; p = 0.0753, respectively), but PF presented higher contamination than PV (p = 0.034). PV did not present any positivity for OP. Three (7%) PF tested positive for both OP and OC. Some PF tested positive for three or four OP, mainly diazinon and dichlorvos. Study limitationLack of data for some controls. ConclusionAlthough the frequency of PV and PF patients exposed to pesticides was similar, pesticides were more frequently detected in hair samples from PF compared to PV. The cause-effect relationship still needs to be determined.

Black Gold-Based “Antenna–Reactor” To Activate Non-Plasmonic Nickel: Photocatalytic Hydrodechlorination and Hydrogenation Reactions

Activation of organic chlorides is a challenging reaction due to their chemical inertness, while hydrogenation of alkene and alkynes faces poor selectivity. In this work, we have demonstrated the use of nickel-loaded black gold (black Au–Ni) that absorbs broadband light from visible to near-infrared of the sunlight due to plasmonic coupling between Au NPs, for photocatalytic hydrodechlorination and propene and acetylene hydrogenation reactions. Hot carriers, the polarizing electric field, and the photothermal effect generated in these catalysts enabled photocatalytic bond activation of these two challenging reactions using visible light at lower temperatures and atmospheric pressure. The black Au–Ni catalyst showed a multifold increase in its activity as compared to black Au. The plasmon-assisted reaction mechanism of hydrodechlorination was supported by intensity-dependent catalysis, kinetic isotope effect (KIE), competitive C–Cl bond activation with one-electron ferricyanide reduction, finite-difference time-domain (FDTD) simulations, and quantum chemical studies. Cluster model-based density functional theory studies show that the reactions have substantial barriers, which were bypassed via an excited state accessed through plasmonic excitations. FDTD studies indicate substantial enhancement of the electric field at the hotspots, iron reduction competed for hot carriers when run in conjunction with C–Cl bond activation, KIE was marginally higher in light as compared to the dark, and the catalyst showed power-dependent activity. These observations indicated the hot carrier involvement in the hydrodechlorination reactions in addition to the photothermal effect.