Perinaphthenone phototransformation in a model of leaf epicuticular waxes

Surface-Enhanced Raman Scattering Imaging Assisted by Machine Learning Analysis: Unveiling Pesticide Molecule Permeation in Crop Tissues

Surface-enhanced Raman scattering (SERS) imaging technology faces significant technical bottlenecks in ensuring balanced spatial resolution, preventing image bias induced by substrate heterogeneity, accurate quantitative analysis, and substrate preparation that enhances Raman signal strength on a global scale. To systematically solve these problems, artificial intelligence techniques are applied to analyze the signals of pesticides based on 3D and dynamic SERS imaging. Utilizing perovskite/silver nanoparticles composites (CaTiO3/Ag@BONPs) as enhanced substrates, enabling it not only to cleanse pesticide residues from the surface to pulp of fruits and vegetables, but also to investigate the penetration dynamics of an array of pesticides (chlorpyrifos, thiabendazole, thiram, and acetamiprid). The findings challenge existing paradigms, unveiling a previously unnoticed weakening process during pesticide invasion and revealing the surprising permeability of non-systemic pesticides. Of particular note is easy to overlook that the combined application of pesticides can inadvertently intensify their invasive capacity due to pesticide interactions. The innovative study delves into the realm of pesticide penetration, propelling a paradigm shift in the understanding of food safety. Meanwhile, this strategy provides strong support for the cutting-edge application of SERS imaging technology and also brings valuable reference and enlightenment for researchers in related fields.

Phenylbenzothiazole-Based Platinum(II) and Diplatinum(II) and (III) Complexes with Pyrazolate Groups: Optical Properties and Photocatalysis

Based on 2-phenylbenzothiazole (pbt) and 2-(4-dimethylaminophenyl)benzothiazole (Me2N-pbt), mononuclear [Pt(pbt)(R'2-pzH)2]PF6 (R'2-pzH = pzH 1a, 3,5-Me2pzH 1b, 3,5-iPr2pzH 1c) and diplatinum (PtII-PtII) [Pt(pbt)(μ-R'2pz)]2 (R'2-pz = pz 2a, 3,5-Me2pz 2b, 3,5-iPr2pz 2c) and [Pt(Me2N-pbt)(μ-pz)]2 (3a) complexes have been prepared. In the presence of sunlight, 2a and 3a evolve, in CHCl3 solution, to form the PtIII-PtIII complexes [Pt(R-pbt)(μ-pz)Cl]2 (R = H 4a, NMe2 5a). Experimental and computational studies reveal the negligible influence of the pyrazole or pyrazolate ligands on the optical properties of 1a-c and 2a,b, which exhibit a typical 3IL/3MLCT emission, whereas in 2c the emission has some 3MMLCT contribution. 3a displays unusual dual, fluorescence (1ILCT or 1MLCT/1LC), and phosphorescence (3ILCT) emissions depending on the excitation wavelength. The phosphorescence is lost in aerated solutions due to sensitization of 3O2 and formation of 1O2, whose determined quantum yield is also wavelength dependent. The phosphorescence can be reversibly photoinduced (365 nm, ∼ 15 min) in oxygenated THF and DMSO solutions. In 4a and 5a, the lowest electronic transitions (S1-S3) have mixed characters (LMMCT/LXCT/L'XCT 4a and LMMCT/LXCT/ILCT 5a) and they are weakly emissive in rigid media. The 1O2 generation property of complex 3a is successfully used for the photooxidation of p-bromothioanisol showing its potential application toward photocatalysis.

Climate warming inhibits neonicotinoid photodegradation on vegetable leaves: Important role of the olefin group in leaf wax

Neonicotinoid photodegradation is seldom considered in different vegetable leaves after spraying under climate warming. This study investigated the effect of elevated cultivated temperature from 15/10 °C to 21/16 °C on the photodegradation of dinotefuran, thiamethoxam, acetamiprid, and thiacloprid on four vegetable leaves under simulated sunlight irradiation. The photodegradation rates of neonicotinoids on spinach leaves were 1.1-1.6, 1.1-2.0, and 1.4-2.4 times higher than those on pak choi, Chinese cabbage, and radish leaves, respectively. The higher production concentrations of hydroxyl radicals (•OH) and superoxide radicals in spinach leaf wax may contribute to the fastest photodegradation among four vegetables. When the cultivated temperature increased from 15/10 °C to 21/16 °C, neonicotinoid photodegradation rates decreased by 1.4-2.8 times on the four vegetables. Elevated cultivated temperature decreased the polarity of wax, which reduced the contact probability of neonicotinoids with reactive species on vegetable leaves and photodegradation rates. A positive linear correlation was found between the content of CHCH groups in wax determining •OH generation and the neonicotinoid photodegradation rates on four vegetable leaves cultivated at three temperatures (R² = 0.67-0.94). Insights into neonicotinoid photodegradation on edible vegetables under climate warming are of great significance for better evaluating human exposure to neonicotinoids through the dietary pathway.

A review of pesticide phototransformation on the leaf surface: Models, mechanism, and influencing factors

Phototransformation is an important environmental fate of pesticides on plant leaves. This review found that the photodegradation rates of pesticides on leaves might be faster or slower than those in organic solvents or on glass because of the different spectral patterns and light fluxes on the model surface. Wax was found to play an important role in pesticide phototransformation because it has photosensitizing properties, which might be stimulated under light irradiation to produce reactive species, such as hydroxyl radicals, singlet oxygen, methyl radicals, alkyl radicals, and superoxide radicals. These reactive species could accelerate pesticide photodegradation by several times. Wax can also decrease the photodegradation rate of pesticides by quenching reactive species or light-shielding effects. The environmental conditions and phytochemical properties of leaves play important roles in pesticide phototransformation primarily because the composition of wax varies with plant species and environmental factors. The phototransformation of pesticides on leaves was promoted by a low dosage of adjuvant because they act as photosensitizers and improve the dispersity of pesticides, while it was inhibited at a high concentration of adjuvant because of their light shielding effect. Finally, recommendations for future research were discussed, including (1) distinguishing the direct and indirect photodegradation of pesticides; (2) developing model, molecular level visualization and analysis techniques; (3) conducting more field research; and (4) considering the effect of climate change, especially the interaction of climatic factors. This review gives a comprehensive overview of the current knowledge of pesticide phototransformation on leaves and provides suggestions for future studies.

How the Way a Naphthalimide Unit is Implemented Affects the Photophysical and -catalytic Properties of Cu(I) Photosensitizers

Driven by the great potential of solar energy conversion this study comprises the evaluation and comparison of two different design approaches for the improvement of copper based photosensitizers. In particular, the distinction between the effects of a covalently linked and a directly fused naphthalimide unit was assessed. For this purpose, the two heteroleptic Cu(I) complexes CuNIphen (NIphen = 5-(1,8-naphthalimide)-1,10-phenanthroline) and Cubiipo (biipo = 16H-benzo-[4′,5′]-isoquinolino-[2′,1′,:1,2]-imidazo-[4,5-f]-[1,10]-phenanthroline-16-one) were prepared and compared with the novel unsubstituted reference compound Cuphen (phen = 1,10-phenanthroline). Beside a comprehensive structural characterization, including two-dimensional nuclear magnetic resonance spectroscopy and X-ray analysis, a combination of electrochemistry, steady-state and time-resolved spectroscopy was used to determine the electrochemical and photophysical properties in detail. The nature of the excited states was further examined by (time-dependent) density functional theory (TD-DFT) calculations. It was found that CuNIphen exhibits a greatly enhanced absorption in the visible and a strong dependency of the excited state lifetimes on the chosen solvent. For example, the lifetime of CuNIphen extends from 0.37 µs in CH2Cl2 to 19.24 µs in MeCN, while it decreases from 128.39 to 2.6 µs in Cubiipo. Furthermore, CuNIphen has an exceptional photostability, allowing for an efficient and repetitive production of singlet oxygen with quantum yields of about 32%.

Environmental photochemistry on plants: recent advances and new opportunities for interdisciplinary research

Plants play a central role in the photochemistry of chemicals in the environment. They represent a major atmospheric source of volatile organic compounds (VOCs) but also an important environmental surface for the deposition and photochemical reactions of pesticides, gaseous and particulate pollutants. In this review, we point out the role of plant leaves in these processes, as a support affecting the reactions physically and chemically and as a partner through the release of natural constituents (water, secondary metabolites). We discuss the influence of the chosen support (leaves, needle surfaces or fruit cuticles, extracted cuticular waxes and model surfaces) and other factors (additives, pesticides mixture, and secondary metabolites) on the photochemical degradation kinetics and mechanisms. We also show how plants can be a source of photochemically reactive species which can act as photosensitizers promoting the photodegradation of pesticides or the formation and aging of secondary organic aerosols (SOA) and secondary organic materials (SOM). Understanding the fate of chemicals on plants is a research area located at the interface between photochemistry, analytical chemistry, atmospheric chemistry, microbiology and vegetal physiology. Pluridisciplinary approaches are needed to deeply understand these complex phenomena in a comprehensive way. To overcome this challenge, we summarize future research directions which have been clearly overlooked until now.

Photolysis of the herbicide dicamba in aqueous solutions and on corn (Zea mays) epicuticular waxes

Dicamba, 3,6-dichloro-2-methoxybenzoic acid, has been used in agriculture as an herbicide for over fifty years, and has seen an increase in use in the past decade due to the development of glyphosate resistant weeds and soybeans genetically modified to resist dicamba. Despite the previous use of dicamba, many questions remain regarding its environmental fate, especially the new commercial formulations used on genetically modified crops. Here, the photolysis of dicamba, including the commercial formulation Diablo®, is examined in aqueous solutions of varying water quality and on the surface of corn epicuticular waxes. Dicamba is stable to hydrolysis but degrades under UV light. The photolytic half-life for dicamba photolysis in aqueous solutions at pH 7 irradiated with Rayonet UVB lamps (280-340 nm) was t1/2 = 43.3 min (0.72 hours), in aqueous solutions at pH 7 in a Q-Sun solar simulator (λ > 300 nm) was t1/2 = 13.4 hours, and on epicuticular waxes irradiated in the Q-Sun solar simulator was t1/2 = 105 hours. Experiments with adjuvants, compounds added into the commercial formulations of dicamba, led to increases in rate constants for both aqueous and wax experiments. In addition to kinetic rate constants, photoproducts were tentatively assigned for the aqueous solution experiments. This work deepens the knowledge of the environmental fate of dicamba including the role surfactants play in chemical reactions and in providing new applications of current methods to examine the photolysis of chemicals sorbed to surfaces.

Perinaphthenone and derivatives as control agents of phytopathogenic fungi: fungitoxicity and metabolism

Metabolism and in vitro fungitoxicity of perinaphthenone against three economically important fungi of the citrus, Botryodiplodia spp., Botrytis spp. and Fusarium spp. were investigated. Perinaphthenone exhibited significant antifungal activity at 62.5 μM and above. Even, the inhibitory effect against Fusarium spp. was significantly enhanced by exposure to direct light. In addition, the metabolism of perinaphthenone by the three fungi was studied. Results show that perinaphthenone was transformed almost completely during the first 24 h; two major products, whose concentration increased progressively during the twelve days of the test, were isolated and identified as 2,3-dihydro-1H-phenalen-1-ol and 2,3-dihydro-phenalen-1-one. Although both metabolic products displayed a considerable fungistatic effect, their slightly lower activities in comparison to perinaphthenone indicate that the transformation was a detoxification process. Studies on the relationship between the effect of some substituents in the perinaphthenone core and the mycelial growth inhibition of Botryodiplodia spp. were also carried out. Results show that the α, β-unsaturated carbonyl system is an important structural requirement but not the only to be necessary for the strong antifungal activity of perinaphthenone. In general, the antifungal properties of perinaphthenone may be modulated through the incorporation of substituents in the naphthalene core or in the α, β-unsaturated carbonyl system. It is concluded that perinaphthenone could be used as an antifungal agent or as a structural template for the development of new fungicide compounds.

Elevated Temperatures Decrease the Photodegradation Rate of Pyrethroid Insecticides on Spinach Leaves: Implications for the Effect of Climate Warming

Climate warming is seldom considered in the transformation of pesticides on a plant leaf. This study investigated the effects of photodegradation temperature and spinach growth temperature from 15 to 21 °C on the photodegradation of bifenthrin, cypermethrin, fenvalerate, and deltamethrin on spinach leaves under xenon lamp irradiation in climate incubators. The photodegradation temperature had minor effects on pyrethroid photodegradation. Interestingly, the photodegradation rates decreased with increasing spinach growth temperature. For example, the photodegradation rate constant of bifenthrin on a spinach cultivated at 15 °C (3.73 (±0.59, 95% confidence level) × 10^-2 h^-1) was 1.9 times higher than that at 21 °C (1.96 (±0.17) × 10^-2 h^-1). Hydroxyl radicals (·OH) played a dominant role in the photodegradation. We speculate that ·OH originated from the degradation of hydroperoxide that was formed by oxidation of phenolic CH═CH, aliphatic CH₃ and aromatic C-O-C, and subsequent hydrogen abstraction. The contents of these functional groups decreased with increasing growth temperature, which resulted in lower photodegradation rates at higher growth temperatures. A possible photodegradation pathway including ester bond cleavage, decyanation, and phenyl group removal was proposed. This work provides new insight into the effects of climate warming on the generation of reactive oxygen species and the transformation of pesticides on a plant leaf.

Assessing the Effects of Alloxydim Phototransformation Products by QSAR Models and a Phytotoxicity Study

Once applied, an herbicide first makes contact with leaves and soil. It is known that photolysis can be one of the most important processes of dissipation of herbicides in the field. However, degradation does not guarantee detoxification and can give rise to byproducts that could be more toxic and/or persistent than the active substance. In this work, the photodegradation of alloxydim herbicide in soil and leaf cuticle surrogates was studied and a detailed study on the phytotoxicity of the main byproduct on sugar beet, tomato, and rotational crops was performed. Quantitative structure⁻activity relationship (QSAR) models were used to obtain a first approximation of the possible ecotoxicological and environmental implications of the alloxydim and its degradation product. The results show that alloxydim is rapidly degraded on carnauba and sandy loam soil surfaces, two difficult matrices to analyze and not previously studied with alloxydim. Two transformation products that formed in both matrices were identified: alloxydim Z-isomer and imine derivative (mixture of two tautomers). The phytotoxicity of alloxydim and the major byproduct shows that tomato possesses high sensitivity to the imine byproduct, while wheat crops are inhibited by the parent compound. This paper demonstrates the need to further investigate the behavior of herbicide degradation products on target and nontarget species to determine the adequate use of herbicidal products to maximize productivity in the context of sustainable agriculture.

Accelerated dissipation of the herbicide cycloxydim on wax films in the presence of the fungicide chlorothalonil and under the action of solar light

Photolysis is a known dissipation pathway of pesticides on leaves just after their spraying. This pathway may be affected by the residues of other pesticides. To illustrate this idea, this study investigated the mutual effect of two pesticides (chlorothalonil and cycloxydim) under simulated solar light. Cycloxydim was added at the agricultural rate (200 g ha(-1)) and chlorothalonil at 1.3-10% of the rate (20-150 g ha(-1)). These compounds were studied either pure or in their commercial formulation. Both analytical and kinetic data show that chlorothalonil significantly accelerates the decay of cycloxydim on wax films, promoting its oxidation, even at the lowest tested dose. Conversely, cycloxydim does not affect the fate of chlorothalonil. Moreover, the detection of oxidized forms of wax alkanes in the extracts demonstrates that chlorothalonil may have also a degrading effect on the leaves' constituents under the action of solar light.