Allelopathy is an ecological phenomenon in which organisms interfere with each other. As a management strategy in agricultural systems, allelopathy can be mainly used to control weeds, resist pests, ...and disease and improve the interaction of soil nutrition and microorganisms. Volatile organic compounds (VOCs) are allelochemicals volatilized from plants and have been widely demonstrated to have different ecological functions. This review provides the recent advance in the allelopathic effects of VOCs on plants, such as growth, competition, dormancy, resistance of diseases and insect pests, content of reactive oxygen species (ROS), enzyme activity, respiration, and photosynthesis. VOCs also participate in plant-to-plant communication as a signaling substance. The main methods of collection and identification of VOCs are briefly summarized in this article. It also points out the disadvantages of VOCs and suggests potential directions to enhance research and solve mysteries in this emerging area. It is necessary to study the allelopathic mechanisms of plant VOCs so as to provide a theoretical basis for VOC applications. In conclusion, allelopathy of VOCs released by plants is a more economical, environmentally friendly, and effective measure to develop substantial agricultural industry by using the allelopathic effects of plant natural products.
Volatile organic compounds (VOCs) are directly associated with human health concerns and environment safety. Therefore, it is urgent to achieve an accurate detection of VOCs both qualitatively and ...quantitatively. In this work, the qualitative detection of ethyl benzene (EB), isopropyl alcohol (IPA), ethyl acetate (EA) - three pure VOCs in liquid phase were discussed using terahertz (THz) microfluidic Electromagnetic Induced Transparency (EIT) meta-sensor. The THz response illustrated that with an increase in VOCs' volumes (1~6μL), resonant frequencies of dual transmission dips (0.855, 1.724 THz) and the EIT peak (1.213THz) exhibited red shift. The limit of detections for pure IPA, EA, EB can achieve 5.45μg, 13.46μg, 4.35μg, respectively. The multivariate fusion (MF) model based on the EIT responses to VOCs was utilized to improve the accuracy of trace detection and classification of VOCs. Furthermore, the above method combined with principal component analysis with Gaussian mixture model (PCA-GMM) and the neural network classification algorithm support vector machine (SVM) was applied to the recognition of VOCs. In addition, the THz method is not feasible to detect trace amounts of VOCs (typically 0.3mg/L) in waste water because water is highly absorbable in THz band and VOCs will evaporate if water is removed. Here, IPA, EA, EB in soil were detected and classified by PCA-GMM combined with MF. Our results provide a new terahertz meta-sensor platform to trace detection of VOCs in liquid phase and in soil and may be used to identify hazardous wastes in illegal dumping.
Display omitted
•Presents a Mxene based virtual sensor array (VSA).•Proposes a convenient strategy for VSA.•We demonstrate correct rates of 90.9%, 90.5%, 90% for the different groups of ...VOCs.•Demonstrates an accuracy of 93.2% for the prediction of ethanol concentrations.
Two-dimensional transition metal carbides/nitrides, known as MXenes, have recently received significant attention for gas sensing applications. However, MXenes have strong adsorption to many types of volatile organic compounds (VOCs), and therefore gas sensors based on MXenes generally have low selectivity and poor performance in mixtures of VOCs due to cross-sensitivity issues. Herein, we developed a Ti3C2Tx-based virtual sensor array (VSA) which allows both highly accurate detection and identification of different VOCs, as well as concentration prediction of the target VOC in variable backgrounds. The VSA’s responses from the broadband impedance spectra create a unique fingerprint of each VOC without a need for changing temperatures. Based on the methodologies of principal component analysis and linear discrimination analysis, we demonstrate highly accurate identifications for different types of VOCs and mixtures using this MXene based VSA. Furthermore, we demonstrate an accuracy of 93.2% for the prediction of ethanol concentrations in the presence of different concentrations of water and methanol. The high level of identification and concentration prediction shows a great potential of MXene based VSA for detection of VOCs of interest in the presence of known and unknown interferences.
Chemical sensing in vertebrates is crucial in their lives, and efforts are undertaken towards deciphering their chemical language. Volatile organic compounds (VOCs) are a group of chemicals believed ...to play an essential role in a wide variety of animal interactions. Therefore, understanding what animals sense themselves and untangling the ecological role of their volatile cues can be accomplished by analysing VOC emissions. A proton‐transfer‐reaction time‐of‐flight mass spectrometer (PTR‐TOF‐MS) is an instrument that measures VOCs in real‐time in an air sample. Since this technique acts as a hyper‐sensitive ‘nose’ it has a similar potential in deciphering the chemical language of vertebrates.
Here, we validate the use of PTR‐TOF‐MS as a tool to measure VOCs from vertebrates, which in turn will help resolve vertebrate interactions through VOCs. The instrument monitors and records the full spectrum of VOCs emitted by an individual with a high accuracy and low detection limit, including transient VOC emissions. We propose and test diverse measuring configurations that allow for measurement of VOC emissions from different vertebrates and their exudates: full body, specific parts of the body, urine and femoral pores. In addition, we test configurations for sudden and short‐lasting processes as VOCs emitted during adder skin shedding as well as the emissions of skin secretions upon mechanical and physiological stimulation in amphibia. Our configurations work in tandem with gas chromatography–mass spectrometry (GC‐MS) to allow compound structure verification.
We discuss the configurations and methodologies used and conclude with recommendations for further studies, such as the choice of chamber size and flow. We also report the results of the measurements on vertebrates—that are novel to science—and discuss their ecological meaning.
We argue that PTR‐TOF‐MS has a high potential to resolve important unanswered questions in vertebrate chemical ecology with great adaptability to a wide range of experimental set‐ups. If combined with a structure verification tool, such as GC‐MS, the creative deployment of PTR‐TOF‐MS in various future study designs will lead to the identification of ecologically relevant VOCs.
Bij vele vertebraten is de reukzin een belangrijk zintuig, en dus worden er volop stappen ondernomen om de chemische taal van deze dieren te ontcijferen. Wellicht vormen vluchtige organische moleculen (Eng. Volatile organic compounds, VOCs) een prominent onderdeel van die taal. Door de uitstoot aan VOCs te analyseren, kunnen we een idee krijgen van de stoffen die dieren waarnemen, en van de ecologische rol die deze verbindingen spelen. De Proton‐Transfer Reaction Time‐of‐Flight Mass Spectrometer (PTR‐TOF‐MS) is een apparaat dat toelaat om VOCs in een luchtmonster, in real time, te meten. Het is als het ware een hypergevoelige neus, met een grote potentiële waarde voor studies naar de chemische taal van vertebraten.
In deze bijdrage gaan we na of PTR‐TOF‐MS kan gebruikt worden om de rol van volatiele moleculen in de chemische communicatie tussen gewervelde dieren te bestuderen. Het toestel volgt en registreert het volledige spectrum aan VOCs geproduceerd door een individueel dier. Dit gebeurt met hoge precisie en met een zeer lage detectielimiet, en zo kunnen zelfs kortstondige en instabiele emissies geanalyseerd worden. We tonen en testen verschillende opstellingen waarbij VOC‐emissies van verschillende vertebraten en hun secreties gemeten worden. De metingen betreffen het volledige lichaam, specifieke lichaamsdelen, klieren en urine. Daarnaast testen we opstellingen voor het meten van plotse, kortstondige VOC‐uitstoten, zoals die zich voordoen bij vervellende slangen en chemische of fysiologische stimulatie van amfibieën. De opstellingen werden gekoppeld aan gas‐chromatografie massa‐spectrometrie (GC‐MS) om de structuur van de verbindingen te verifiëren.
We bespreken de verschillende gebruikte opstellingen en methoden en geven suggesties aangaande hun gebruik bij toekomstige studies, bijvoorbeeld qua grootte van de meetkamer en de doorstroming. We geven ook de (nieuwe) resultaten van onze metingen op verschillende vertebraten weer en bespreken hun ecologische relevantie.
We besluiten dat PTR‐TOF‐MS een veelbelovende techniek is die kan bijdragen aan het beantwoorden van de vele vragen die nog bestaan over de chemische ecologie van vertebraten. Mits gecombineerd met hulpmiddelen ter verificatie van de structuur van verbindingen (vb. GC‐MS), zal het creatief inzetten van PTR‐TOF‐MS in toekomstige studies leiden tot de identificatie van ecologisch relevante VOCs.
SUMMARY
Volatile organic compounds (VOCs) released by plants serve as information and defense chemicals in mutualistic and antagonistic interactions and mitigate effects of abiotic stress. Passive ...and dynamic sampling techniques combined with gas chromatography–mass spectrometry analysis have become routine tools to measure emissions of VOCs and determine their various functions. More recently, knowledge of the roles of plant VOCs in the aboveground environment has led to the exploration of similar functions in the soil and rhizosphere. Moreover, VOC patterns have been recognized as sensitive and time‐dependent markers of biotic and abiotic stress. This focused review addresses these developments by presenting recent progress in VOC sampling and analysis. We show advances in the use of small, inexpensive sampling devices and describe methods to monitor plant VOC emissions in the belowground environment. We further address latest trends in real‐time measurements of volatilomes in plant phenotyping and most recent developments of small portable devices and VOC sensors for non‐invasive VOC fingerprinting of plant disease. These technologies allow for innovative approaches to study plant VOC biology and application in agriculture.
Significance Statement
Determining the emission of volatile organic compounds released by plants represents a key methodology in understanding and monitoring chemical interactions of plants with their biotic and abiotic environment in agriculture and natural ecosystems. This review presents recent developments and state‐of‐the‐art technical advances in volatile organic compound sampling and analysis in belowground environments and as integrated technology of plant phenotyping and disease diagnostics.
The selective and sensitive detection of chemical agents is demanded by a wide range of practical applications. In particular, sensing of volatile organic compounds (VOCs) at parts-per-billion level ...is critical for environmental monitoring, process control, and early diagnosis of human diseases. In this report, we demonstrate a specific and highly sensitive detection of ketone compounds using two-dimensional (2D) molybdenum ditelluride (MoTe
). We investigated the effects of UV activation on the sensing performance to a variety of VOCs. It is found that the MoTe
field-effect transistor (FET) exhibits an opposite sensing response to ketone compounds before and after UV light activation, whereas the responses to other types of VOCs remain in the same direction regardless of the illumination. This unique behavior enables the discriminative detection of ketone molecules including acetone and pentanone from other VOCs in a gas mixture. The activation of UV light also results in a very high sensitivity and low detection limit toward acetone (∼0.2 ppm). Moreover, the MoTe
FET shows a stable sensing performance in a high humidity environment. The results demonstrate the potential of MoTe
as a promising candidate for high-performance acetone sensors in important applications such as human breath analysis. The scheme of light-tunable sensing can be applied to a broad range of sensing platforms based on 2D materials.
Display omitted
•Cu-Mn-Ce mesoporous catalysts were prepared on ceramic bases.•Oβ was increased and Oγ was decreased when Cu-Mn-Ce oxides were synergistic.•Activation temperature of synergistic ...catalyst will be reduced.•VOCs were removed effectively via microwave catalytic combustion with filtration.
Cu-Mn-Ce mesoporous catalysts with different aperture distribution were prepared on ceramic bases by the impregnation method. The degradation process of volatile organic compounds (VOCs) (toluene, ethyl acetate, acetone, and their mixture) with different catalysts under microwave catalytic combustion was studied, and the synergistic mechanism of Cu-Mn-Ce matters during catalysis were identified. Under the condition of microwave power of 300 W and gas flow rate of 200 ml min−1, the TVOC removal efficiency of toluene (810.38 ± 24.05 mg m−3), ethyl acetate (759.55 ± 12.84 mg m−3), and acetone (795.35 ± 42.76 mg m−3) were 93.09%, 85.41%, and 97.14%, respectively, and their removal efficiencies could reach almost 100%. After 10 cycles (2100 mins), the Cu-Mn-Ce mesoporous catalysts still had adsorption and filtration effects, and the best catalyst showed excellent stability with a removal efficiency of 91.40% for the mixed TVOC. The reasons for the high catalytic performance of Cu-Mn-Ce mesoporous ceramic base catalyst include: 1) The catalyst was highly dispersed on the mesoporous carrier, and cerium further promotes catalyst dispersion. 2) Composite metal oxides could effectively react with each other in the synergistic process. 3) Composite metal oxides catalyst increased the Oβ and decreased the Oγ after synergizing with each other. 4) The hydrogen reduction temperature was significantly lower after metal oxide synergy. 5) The composite catalysts could work together to effectively maintain the unpaired electrons on the catalyst surface and replace the internal structural elements thus forming various defects. The trace amount of residual organics were less harmful to the environment.
Display omitted
In this paper, a simple solvothermal synthesis method was proposed for the preparation of metal organic framework/graphene oxide hybrid nanocomposite (UiO-67/GO). A series of ...UiO-67/GO composites were prepared by varying the addition forms and amounts of GO, and the optimal synthesis conditions were screened. The composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission Electron Microscope (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), water contact angles (CA) and thermogravimetric analysis (TGA). The adsorption capacity and the adsorption process of toluene were investigated by dynamic adsorption and adsorption kinetics, respectively. The results indicated that 67/GO-0.5% reached the maximum adsorption capacity (876 mg g−1), which far exceeded the other adsorbents. Kinetic model and the Weber-Morris model correlated satisfactorily to the experimental data. The improved adsorption performance was attributed to GO, which enhanced π-π interaction, promoted defect generation and provided more adsorption sites. Finally, the excellent regeneration performance of the adsorbent was verified by temperature programmed desorption (TPD) and cyclic adsorption–desorption experiments. Moreover, the adsorption mechanism was further revealed. Combined with the related adsorption experiments and the density functional theory (DFT) analysis, the efficient removal of toluene by UiO-67/GO was attributed to the cooperation of defects, π-π interaction and hydrogen bonding.
Display omitted
•Optimum proportion of benzoic acid for synthesis of more defects UiO-67.•Defects, methyl and benzene ring enhance π-π interaction to promote VOCs adsorption.•Multiple experiments and ...DFT calculation analyze interaction between VOCs and MOFs.
The harm that is caused by volatile organic compounds (VOCs) has attracted worldwide attention. In production, industrial processes such as fossil fuel combustion, plastics, and paints have caused complex and diverse VOCs emissions. Therefore, studying the phenomenon and influencing factors of typical VOCs adsorption is of practical significance for the treatment of multicomponent VOCs. In this work, defective UiO-67 was prepared by changing the amount of benzoic acid. Then, the adsorption performance was tested, and the adsorption kinetics were considered. The experimental results showed that the 67-ben-10 sample (for which the molar ratio of Zr4+ to benzoic acid was 1:10) achieved the maximum toluene adsorption capacity (480 mg g−1), which was due to the presence of more adsorption sites, higher benzoate content, strong π-π stacking and excellent adsorption diffusion behavior. In addition, the adsorption properties of the 67-ben-10 benzene series (BTX: benzene, toluene, o-xylene, p-xylene and m-xylene) and acetone were further investigated. The results showed that the adsorption performance was related to the polarizability of the VOCs molecules, the method of pore entry and the molecular size. Finally, through desorption experiments, density functional theory (DFT) and kinetics, the binding energy was confirmed to play an important role in adsorption and diffusion.
PDF
