Volatile Organics Research Articles

Surface passivation by multifunctional carbon dots toward highly efficient and stable inverted perovskite solar cells

Interfacial imperfections between the perovskite layer and the electron transport layer (ETL) in perovskite solar cells (PSCs) can lead to performance loss and negatively influence long-term operational stability. Here, we introduce an interface engineering method to modify the interface between perovskite and ETL by using multifunctional carbon dots (CDs). C = O in the CDs can chelate with the uncoordinated Pb2+ in the perovskite material, inhibit interfacial recombination, and enhance the performance and stability of device. In addition, –OH in CDs forms hydrogen bonds with I− and organic cation in perovskite, inhibiting light-induced I2 release and organic cation volatilization, causing irreversible degradation of perovskite films, thereby enhancing the long-term operational stability of PSCs. Consequently, we achieve the champion inverted device with an efficiency of 24.02%. The CDs-treated PSCs exhibit high operational stability, and the maximum power point tracking only attenuates by 12.5% after 1000 h. Interfacial modification engineering supported by multifunctional quantum dots can accelerate the road to stable PSCs.

Nitrous oxide emissions dynamics in Indian agricultural landscapes: Revised emission rates and new insights

In the past five decades, nitrous oxide (N2O) emissions from Indian agricultural landscapes have significantly increased, making India the fifth-largest emitter of N2O globally (∼4.8%). The few studies that evaluated N2O at the India scale using a bottom-up approach were constrained to a brief period and employed country-level emission factors (EFs), despite the availability of long-term inventory data and spatially varying EFs. To fill this gap and comprehend the spatio-temporal N2O emissions dynamics at the district-level across India, this study created district- and crop-specific N2O EFs from 82 field plot studies with 861 observations across 13 locations. Through these improved EFs, district-level emissions were calculated from 1966 to 2017 using a modified IPCC Tier I-Tier II approach (specific EFs for synthetic fertilizer, animal manure, and crop residue return) and highlighted significant spatio-temporal drivers. Total N2O emissions in Indian agricultural soils increased from 73.7 ± 3.3 Gg in 1966–279.3 ± 15.8 Gg in 2017. The increase in total N2O emissions (3.9 Gg yr−1) from 1966 to 2017 is associated with the increase in crop production (4.1 Tg yr−1) driven by the increase in fertilization (0.3 Tg yr−1). N2O emissions from synthetic fertilizer, animal manure, crop residue return, soil organic matter, volatilization, leaching, and runoff increased from 1966 to 2017. On the national scale, N2O emissions from synthetic fertilization accounted for 57% in 2017, followed by animal manure (15%) and soil organic matter (9%). While the national emission totals are dominated by synthetic fertilizer application, district-level analyses revealed the possibility of the highest contributions from animal manure, crop residue return, and soil organic matter in 18% of the districts. The overall uncertainty from this modified method and refined EFs was 5.1%. This study is the first to capture long-term N2O dynamics at the district scale from Indian agricultural soils.

Rationally constructing a 3D bifunctional solar evaporator for high-performance water evaporation coupled with pollutants degradation

In this work, nitrogen-doped carbon nanotubes encapsulated with Co are grown on carbon fibers (Co-NCNT/CF) and utilized as photothermal materials to construct 3D evaporators, which simultaneously realize highly efficient solar evaporation and organic pollutant degradation. The deliberate structure enables the 3D evaporator to take advantage of the spontaneously generated internal convection flow to significantly enhance solar evaporation, achieving a high evaporation rate of 3.85 kg m−2 h−1 under 1.0 sun irradiation. More importantly, the evaporator exhibits excellent performance on peroxymonosulfate (PMS) activation, effectively preventing phenol in water sources from entering the condensed clean water. Density functional theory (DFT) calculation shows that the enhanced van der Waals interaction facilitates PMS adsorption and activation on the confined inner surfaces of Co-NCNT compared to the unconfined system. This solar evaporator successfully combines interfacial solar evaporation and advanced oxidation processes, providing a new strategy for producing clean water from water sources containing organic volatiles.

Numerical simulation study on the formation and control of HCl during the gasification of industrial organic hazardous waste

The utilization of industrial organic waste instead of coal by high temperature gasification to produce syngas is a promising way to reduce carbon emissions. The distinct property of industrial hazardous waste is characterized as high content of chlorine and volatile organics, which is significantly different from coal-water slurry. Herein, novel numerical models were established to simulate to the formation and control of HCl in the Texaco gasifier, where the chlorine-containing substances were simplified as dichloromethane to describe the mass transfer during the gasification. The models presented a good accuracy with the minimum error of 0.55% in syngas components prediction. The simulation demonstrated that HCl was generated near the nozzle, and the increasing of CaO amount and the decreasing of its particle size had positive effect on dechlorination. However, excessively reducing the size of CaO below 0.1 mm decreased its promoting effect, and high temperature in flame zone inhibited the dechlorination reaction. Therefore, the models developed in this work provided the feasibility of the general numerical simulation method to optimize the operating conditions in order to reduce the corrosion of chlorine to equipment and improve the stability of operation during the gasification process of organic hazardous waste.

Performance evaluation of an ambient volatile organics sensor based on mesoporous silica preconcentrator and a photoionization detector

Performance evaluation of an ambient volatile organics sensor based on mesoporous silica preconcentrator and a photoionization detector

Characterization of calcined red soil applied in the removal of methylene blue dye from wastewater to produce a hybrid pigment

AbstractWe obtained natural red soil (RS), rich in iron, from the region of Palotina in the state of Paraná, Brazil. The RS sample was purified by suspension in water and sieved to remove plant particulates. It was then treated thermally at 800°C to remove organic volatiles; this sample was called RS800. The samples were characterized using X-ray diffraction, X-ray fluorescence, infrared and electronic spectroscopy, ζ-potential analysis and scanning electron microscopy. Colorimetric studies were performed according to the CIEL*a*b* system. Tests have shown that RS800 has the ability to remove methylene blue (MB) dye from wastewater. Thus, it was used as an adsorbent at various temperatures (25, 35, 45°C). According to the Langmuir model, the maximum adsorption capacity (qmax) was 23.256 mg g–1 (25°C). Unexpectedly, increasing temperature reduced qmax to 21.659 mg g–1 at 35°C and to 21.186 mg g–1 at 45°C. Therefore, RS800 must be used at room temperature (25°C), making its application in large-scale wastewater treatment feasible. After using RS800 as an adsorbent, the solids were filtered, dried, pulverized, and used as hybrid pigments in commercial white paints. Pigmented paints were used to paint a plaster specimen and colorimetric measurement was performed. These paints were tested for colour stability in acidic and alkaline environments. The results indicate that RS800 is efficient in the treatment of water contaminated with cationic dyes and can be reused as a hybrid pigment.

Involvement of Holotrichia parallela odorant-binding protein 3 in the localization of oviposition sites

Organic fertilizers-derived volatiles attract Holotrichia parallela during oviposition. However, the mechanisms underlying the perception of oviposition cues in H. parallela remain unclear. Here, H. parallela odorant-binding protein 3 (HparOBP3) was identified as a key OBP. Bioinformatics analysis showed that HparOBP3 clustered together with Holotrichia oblita OBP8. HparOBP3 was mainly expressed in the antennae of both sexes. Recombinant HparOBP3 exhibited distinct binding affinities towards 22 compounds released by organic fertilizers. After 48 h of RNA interference (RNAi), the expression of HparOBP3 in male and female antennae was decreased by 90.77 % and 82.30 %, respectively. In addition, silencing of HparOBP3 significantly reduced the electrophysiological responses and tropism of males to cis-3-hexen-1-ol, 1-hexanol, and (Z)-β-ocimene as well as females to cis-3-hexen-1-ol, 1-hexanol, benzaldehyde, and (Z)-β-ocimene. Molecular docking indicated that hydrophobic residues Leu-83, Leu-87, Phe-108, and Ile-120 of HparOBP3 were important amino acids for interacting with ligands. Mutation of the key residue, Leu-83, significantly diminished the binding ability of HparOBP3. Furthermore, acrylic plastic arena bioassays showed that the attraction and oviposition indexes of organic fertilizers to H. parallela were reduced by 55.78 % and 60.11 %, respectively, after silencing HparOBP3. These results suggest that HparOBP3 is essential in mediating the oviposition behavior of H. parallela.

Industrial Multiple-Effect Fractional Condensation under Vacuum for the Recovery of Hop Terpene Fractions in Water.

The inflorescences of Humulus lupulus L. are the most valuable ingredient in the brewing industry. Only female cones are used as their bitterness and aroma, much associated with beer, are granted by the production of resins and essential oils, respectively. The traditional brewing process for the extraction of the organic volatiles in hops is called dry hopping. It consists of extended maceration at low temperature after the fermentation phase. New extraction technologies can improve extraction rates and product quality while saving time and money. This article proves that multiple-effect fractional condensation under a vacuum is suitable for flavouring applications and especially for performing dry hopping without contamination risks and reductions in hop amounts. This technique leads to the recovery of aqueous aromatic fractions that are very rich in hop sesquiterpenes and monoterpenes. These suspensions are extremely stable when stored at 5-8 °C and avoid degradation even after several months. This feature is crucial for the marketing of non-alcoholic beverages, where the dilution of essential oils is otherwise problematic.

Updating emission inventories for vehicular organic gases: Indications from cold-start and temperature effects on advanced technology cars

How would the organic gas emission inventories of future urban vehicles change with new features of advanced technology cars? Here, volatile organic compounds (VOCs) and intermediate volatile organic compounds (IVOCs) from a fleet of Chinese light-duty gasoline vehicles (LDGVs) were characterized by chassis dynamometer experiments to grasp the key factors affecting future inventory accuracy. Subsequently, the VOC and IVOC emissions of LDGVs in Beijing, China, from 2020 to 2035, were calculated and the spatial-temporal variations were recognized under a scenario of fleet renewal. With the tightening of emission standards (ESs), cold start contributed a larger fraction of the total unified cycle VOC emissions due to the imbalanced emission reductions between operating conditions. It took 757.47 ± 337.75 km of hot running to equal one cold-start VOC emission for the latest certified vehicles. Therefore, the future tailpipe VOC emissions would be highly dependent on discrete cold start events rather than traffic flows. By contrast, the equivalent distance was shorter and more stable for IVOCs, with an average of 8.69 ± 4.59 km across the ESs, suggesting insufficient controls. Furthermore, there were log-linear relationships between temperatures and cold-start emissions, and the gasoline direct-injection vehicles performed better adaptability under low temperatures. In the updated emission inventories, the VOC emissions were more effectively reduced than the IVOC emissions. The start emissions of VOCs were estimated to be increasingly dominant, especially in wintertime. By winter 2035, the contribution of VOC start emissions could reach 98.98 % in Beijing, while the fraction of IVOC start emissions would decrease to 59.23 %. Spatially allocation showed that the high emission regions of tailpipe organic gases from LDGVs have transferred from road networks to regions of intense human activities. Our results provide new insights into tailpipe organic gas emissions of gasoline vehicles, and can support future emission inventories and refined assessment of air quality and human health risk.

1ppm-detectable hydrogen gas sensors by using highly sensitive P+/N+ single-crystalline silicon thermopiles

Hydrogen (H2) is currently of strategic importance in the pursuit of a decarbonized, environmentally benign, sustainable global energy system; however, the explosive nature of H2 requires leakage monitoring to ensure safe application in industry. Therefore, H2 gas sensors with a high sensitivity and fast response across a wide concentration range are crucial yet technically challenging. In this work, we demonstrate a new type of MEMS differential thermopile gas sensor for the highly sensitive, rapid detection of trace H2 gas in air. Facilitated by a unique MIS fabrication technique, pairs of single-crystalline silicon thermopiles (i.e., sensing and reference thermopiles) are batch fabricated with high-density single-crystalline silicon thermocouples, yielding an outstanding temperature sensitivity at the sub-mK level. Such devices ensure the detection of miniscule temperature changes due to the catalytic reaction of H2 with a detection limit as low as ~1 ppm at an operating temperature of 120 °C. The MEMS differential thermopiles also exhibit a wide linear detection range (1 ppm-2%, more than four orders of magnitude) and fast response and recovery times of 1.9 s and 1.4 s, respectively, when detecting 0.1% H2 in air. Moreover, the sensors show good selectivity against common combustible gases and volatile organics, good repeatability, and long-term stability. The proposed MEMS thermopile H2 sensors hold promise for the trace detection and early warning of H2 leakage in a wide range of applications.

Gas Sensing of Laser-Produced Hybrid TiO2-ZnO Nanomaterials under Room-Temperature Conditions.

The preparation method can considerably affect the structural, morphological, and gas-sensing properties of mixed-oxide materials which often demonstrate superior photocatalytic and sensing performance in comparison with single-metal oxides. In this work, hybrids of semiconductor nanomaterials based on TiO2 and ZnO were prepared by laser ablation of Zn and Ti plates in water and then tested as chemiresistive gas sensors towards volatile organics (2-propanol, acetaldehyde, ethanol, methanol) and ammonia. An infrared millisecond pulsed laser with energy 2.0 J/pulse and a repetition rate of 5 Hz was applied to Zn and Ti metal targets in different ablation sequences to produce two nano-hybrids (TiO2/ZnO and ZnO/TiO2). The surface chemistry, morphology, crystallinity, and phase composition of the prepared hybrids were found to tune their gas-sensing properties. Among all tested gases, sample TiO2/ZnO showed selectivity to ethanol, while sample ZnO/TiO2 sensed 2-propanol at room temperature, both with a detection limit of ~50 ppm. The response and recovery times were found to be 24 and 607 s for the TiO2/ZnO sensor, and 54 and 50 s for its ZnO/TiO2 counterpart, respectively, towards 100 ppm of the target gas at room temperature.

Modeling of wintertime regional formation of secondary organic aerosols around Beijing: sensitivity analysis and anthropogenic contributions

Modeling of secondary organic aerosol (SOA) has remained a big challenge due to the various precursors and complex processes involved. In this study, the WRF-CAMx model was used to predict the ambient SOA concentrations in urban Beijing as well as the North China Plain (NCP) during a polluted period in winter. To identify the major uncertainties and improve the model performance, a series of model tests were performed to assess the sensitivity of model prediction to the key factors. Then the sources of SOA in Beijing were identified using the optimized model. Both the volatility basis set (VBS) approach and the two-product approach were used for SOA simulation. Although the modeled SOA was underpredicted compared with the SOA estimated through filter-based measurements, the VBS scheme produced higher SOA than the traditional two-product scheme. According to the sensitivity tests with the VBS scheme, the emissions of volatile organic compounds (VOC) and intermediate volatility organic compounds (IVOC) as well as the oxidant levels were the key factors that affected SOA prediction. Based on the optimized simulation scenario, the potential contributions from different anthropogenic sources and source areas were identified, with over 80% of SOA in urban Beijing from regional transport of SOA or its precursors from the surrounding areas during the polluted period. Residential emission in the North China Plain appeared as the dominant source of SOA in urban Beijing from the perspective of regional contribution.Graphical

Bark Beetles Utilize Ophiostomatoid Fungi to Circumvent Host Tree Defenses.

Bark beetles maintain symbiotic associations with a diversity of microbial organisms, including ophiostomatoid fungi. Studies have frequently reported the role of ophiostomatoid fungi in bark beetle biology, but how fungal symbionts interact with host chemical defenses over time is needed. We first investigated how inoculations by three fungal symbionts of mountain pine beetle affect the terpene chemistry of live lodgepole pine trees. We then conducted a complimentary laboratory experiment specifically measuring the host metabolite degradation by fungi and collected the fungal organic volatiles following inoculations with the same fungal species on lodgepole pine logs. In both experiments, we analyzed the infected tissues for their terpene chemistry. Additionally, we conducted an olfactometer assay to determine whether adult beetles respond to the volatile organic chemicals emitted from each of the three fungal species. We found that all fungi upregulated terpenes as early as two weeks after inoculations. Similarly, oxygenated monoterpene concentrations also increased by several folds (only in logs). A large majority of beetles tested showed a strong attraction to two fungal species, whereas the other fungus repelled the beetles. Together this study shows that fungal symbionts can alter host defense chemistry, assist beetles in overcoming metabolite toxicity, and provide possible chemical cues for bark beetle attraction.

Chemical Composition and Insecticidal Activity against Tribolium Castaneum of Thapsia garganica L. Seed Essential Oil.

Due to the several side effects of synthetic pesticides, including environmental pollution, threats to human health, and the development of pest resistance to insecticides, the use of alternative healthy, available and efficient agents in pest management strategies is necessary. Recently, the use of essential oil obtained from aromatic plants has shown significant potential for insect pest management. For this reason, the essential oil isolated from seeds of Thapsia garganica L. was investigated for the first time for its chemical profile, and its toxicity and repellency effects against Tribolium castaneum adults. Qualitative and quantitative analyses of the chemical composition by gas chromatography coupled to mass spectrometry (GC/MS) revealed the presence of 18 organic volatiles representing 96.8 % of the total constituents. The main compounds were 1,4-dimethylazulene (51.3 %) followed by methyl palmitate (8.2 %), methyl linoleate (6.2 %) and costol (5.1 %). Concerning the repellent effect, results revealed that SEO (Seed Essential Oil) was very repellent towards T. castaneum adults, with 100 % repellency after 2 h of exposure. Furthermore, the essential oil exhibited remarkable contact toxicity against T. castaneum (93.3 % of mortality) at the concentration of 10 % (v/v). The median lethal dose (LD50 ) of the topical application of the seed essential oil was 4.4 %. These encouraging outcomes suggested that the essential oil from T. garganica seeds could be considered a potent natural alternative to residual persistent and toxic insecticides.

Synthesis of magnetic adsorbents from titanium gypsum and biomass wastes for enhanced phosphate removal

A novel scheme was proposed to prepare magnetic adsorbents by co-pyrolysis of titanium gypsum (TiG) and agricultural biomass wastes for phosphate (P) recovery. Co-presence of biomass wastes could improve TiG decomposition in inert atmosphere to generate magnetic centers and active sites, and P adsorption correlated well with organic volatiles of biomass wastes. The adsorption process evolved from a biomass-controlled process to a TiG-controlled process when increasing the mass ratio of corncob above 10 %. The optimal adsorbent (i.e. GC10) exhibited higher P adsorption capacity (Qm 183 mg/g) than many previous adsorbents; moreover, it can be magnetically separated from water after P adsorption. Active sites including CaO, CaS and Fe3O4 were deemed as the main factors for P chemisorption and surface precipitation. Most of adsorbed P could be released continuously and slowly by dilute NaHCO3. These results highlight potential applications of TiG and biomass waste derived adsorbents in P purification and recovery.

Brown carbon absorptivity in fresh wildfire smoke: associations with volatility and chemical compound groups

Brown carbon light absorptivity is associated with organic aerosol volatility and elemental carbon concentrations.

ИССЛЕДОВАНИЕ ЛЕТУЧИХ ОРГАНИЧЕСКИХ СОЕДИНЕНИЙ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ ПРИ МОДЕЛИРОВАНИИ ТЕРМОДЕСТРУКЦИИ

Chromatography-mass spectrometry was used to investigate dynamics of volatile organic compounds released by 6 coal plastics of a carbon fiber and epoxy binder proposed for internal structures of manned spacecrafts. It was established that temperature growth higher than 90 °С increases migration and enlarges the spectrum of volatile organics, hygienically important aldehydes primarily, which is characteristic of autocatalytic radical depolymerization with production of volatile low-molecular-weight compounds. Kinetics of their off-gassing can be used to characterize destruction of the epoxy base of composite materials (CMs). Primary products of the thermo-oxidative destruction of these CMs are aldehydes and ketones; at 150 °С and 180 °С, concentrations of these compounds reached maximum levels and made up 98 % of off-gassed compounds.

Overview of Recent Development of Needle-Trap Devices for Analysis of Volatile Compounds

Needle-trap devices (NTDs) are another sorbent-based tool in the haystack of methods used in analytical extractions. Syringe needles, similar to those used for gas chromatography (GC) injection, can be partially filled with suitable sorbents and are used for extracting and collecting volatile organics, followed by injection into a GC instrument via thermal desorption. Although NTDs share many similarities and advantages of solid-phase microextraction (SPME), the larger sorbent bed provides robustness and offers potentially exhaustive extractions. This month, we take a look at the principles and applications of NTDs, and recent developments in their use.

Effects of apple storage period on the organic acids and volatiles in apple wine

To explore the effects of storage on the organic acids and volatiles in apple wine, fresh Fuji and Ralls Genet apples were stored for 5 months and making apple wines monthly. By 5-month storage, L-malic and succinic acids in juices decreased by 1755.78–2269.69 mg/L and 582.25–943.10 mg/L, respectively. Correspondingly, l-malic acid decreased by 665.73–987.45 mg/L in wine. Succinic acid from fermentation was positively correlated with the pH of juices (r = 0.709*). Storage enriched fruit volatiles, especially in Ralls Genet, 6 volatiles were generated by 1 month storage. Isobutylacetate, isoamylacetate and hexylacetate were mostly affected in Fuji juice; they were increased by 32.80, 20.54 and 7.99 times by 3 months storage. While isoamylol, 1-hexanol and 6-methyl-5-hepten-2-ol in Ralls Genet juice rose up by 11.43, 3.92 and 137.37 times during storage. Esters were mostly affected by storage in apple wines, especially Fuji wine, its content decreased by 59.4–104.05 mg/L after 5 months storage. The production of volatiles in Ralls Genet wine was more easily affected by pH of juice. Therefore, apple storage affected organic acids and volatiles in apple wines by affecting apples and yeast metabolism simultaneously. And apple stored for 1 month achieved balanced taste and richness flavors.

Microbiological, chemical, and sensorial characterisation of commercially available plant-based yoghurt alternatives

Consumer demand for plant-based dairy alternatives has increased rapidly during the past few years and the market has been saturated with a wide variety of alternative products. The general aim of this study was to broaden the understanding of the composition and characteristics of currently commercially available plant-based yoghurt alternatives focusing especially on the content of live bacteria. The bacterial composition, including the content of live bacteria in yoghurt alternatives, was evaluated using metagenetic sequencing of the 16S rRNA gene amplicons in combination with the novel PMAxx treatment approach. The content of organic acids, sugars, and volatiles was measured, and descriptive sensory analysis was carried out to comprehensively describe the products. While the main ingredient (soya, oat, coconut, or lupin) determined the general characteristics of the product, significant differences were observed in both chemical and microbiological composition and sensorial attributes even among the yoghurt alternatives made from the same plant ingredient.