First electrochemical study of the fungicide oxycarboxin

In this article, the utility of a boron-doped diamond electrode for the determination of the fungicide oxycarboxin is demonstrated. For the first time, the square-wave voltammetry was employed in a quantitative determination of oxycarboxin on the boron-doped diamond electrode. It was found that oxycarboxin displays a well-expressed oxidation peak at a potential of ca. +1.5 V vs. Ag/AgCl in Britton–Robinson buffer with the maximum response in pH 4.0. As observed in cyclic voltammetry, oxycarboxin undergoes diffusion-controlled irreversible electrochemical oxidation. At optimised square-wave voltammetry parameters, the current response of oxycarboxin was linearly proportional to its concentration in the wide linear dynamic range of 8.0–100.0 μmol L^?1 (2.1–26.7 mg L^?1). The developed electroanalytical method yielded a relatively low limit of detection of 1.6 μmol L^?1 (0.4 mg L^?1), associated with high repeatability of the peak current expressed as relative standard deviation in the range of 1.1–2.9% for each concentration of oxycarboxin solution. This simple and sensitive method was proved to be suitable for an analysis of spiked river water samples with satisfactory results (relative standard deviation of 1.4%, recovery of 100.2%). The impact of possible interferences was tested and evaluated, and obtained results proved good selectivity of the proposed method. In addition, the influence of oxycarboxin on the corrosion properties of AISI 316 L stainless steel used as a construction material in farming was tested using potentiodynamic method, and a corrosive damage was characterised by means of scanning electron microscopy.     

ESI–MS method for in vitro investigation of skin penetration by copper–amino acid complexes: from an emulsion through a model membrane

Copper can be found in many cosmetic formulations, mainly as complexes with peptides, hydroxyacids or amino acids. The main reason that the usage of this element in this context is still increasing is its beneficial biochemical activity, although the mechanism that enables its complexes to permeate through skin barriers is largely unknown. The ability of copper complexes with amino acids to penetrate through the stratum corneum and participate in copper ion transport processes is key to their cosmetic and pharmaceutical activities. The penetration process was studied in vitro in a model system, a Franz diffusion cell with a liposome membrane, where a liquid crystalline system with physicochemical properties similar to those of the intercellular cement of stratum corneum was used to model the skin barrier. The influences of various ligands on the model membrane migration rate of copper ions was studied, and the results highlighted the crucial roles of metal ion complex structure and stability in this process.     

IR studies of coadsorption of CO and NO on Co and Cu sites in zeolites

The present study was carried out to follow the effect of CO coadsorption on the properties of NO adsorbed on the same Co²⁺ sites. As the activation of the different molecules was found to be specially pronounced for Cu⁺ in MFI and FAU zeolites, the coadsorption of CO and NO on Cu⁺ sites was also examined. Our previous studies reveled that the presence of the electron donor ammonia and pyridine molecules strongly weakened the multiple bond in NO molecule bonded to the same Cu⁺ cation. The present IR experiments evidenced that CO acted as an electron acceptor. The flow of an electron density from the antibonding π* orbital of NO via Co²⁺ or Cu⁺ to the antibonding π* orbital of CO results in strengthening of the NO bond and in weakening of the CO bond.     

The Cp*Si+ cation as a stoichiometric source of silicon

The Cp*Si(+) cation acts as a stoichiometric source of silicon in the reaction with the disilenide Tip(2)Si=Si(Tip)Li (Tip = 2,4,6-(i)Pr(3)C(6)H(2)) affording known neutral unsaturated silicon clusters. It thereby provides a conceptually different approach to this novel class of compounds. The proposed mechanism involves a Cp*-substituted cyclotrisilene in which Cp*(-) acts as a leaving group upon single electron reduction or in a nucleophilic substitution step.     

Spectroscopic IR, EPR, and operando DRIFT insights into surface reaction pathways of selective reduction of NO by propene over the Co-BEA zeolite

Interaction of a Co-BEA catalyst with individual components (NO, C(3)H(6), CO, O(2)) and mixtures simulating the real feed of the selective catalytic reduction (SCR) of nitric oxide in static and pulse experiments at variable temperatures was investigated by means of IR, EPR, and operando DRIFT spectroscopy coupled with QMS/GC analysis of the products. Speciation of cobalt active sites into Co(II), mono- and polynuclear oxo-cobalt species as well as CoO clusters was quantified by IR using CO and NO as probe molecules. The key intermediates, by-products, and final products of the SCR reaction were identified and their spectroscopic signatures ascertained. Based on the spectroscopic operando results, a concise mechanistic scheme of the selective catalytic reduction of nitric oxide by propene, triggered by a two-electron Co(II)/Co(0) redox couple, was developed. It consists of a complex network of the sequential/parallel selective reduction steps that are interlocked by the rival nonselective oxidation of the intermediates and their thermal decomposition. It has been shown that the SCR process is initiated by the chemoselective capture of NO from the reaction mixture by the cobalt active sites leading to the cobalt(II) dinitrosyls, which in the excess of oxygen are partially oxidized to surface nitrates and nitrites. N(2)O is produced by semi-decomposition of the dinitrosyl intermediates on the mononuclear centers, whereas NO(2)via NO oxidation on the polynuclear oxo-cobalt sites. Cyanide and isocyanate species, formed together with propene oxygenates in the course of the C=C bond scission, are the mechanistically pivotal reaction intermediates of C(3)H(6) interaction with the dinitrosyles and NO(3)(-)/NO(2)(-) surface species. Dinitrogen is produced by three main reaction routes involving oxidation of cyanides by NO/NO(2), reduction of dinitrosyls, nitrates, and nitrites by propene oxygenates (medium temperature range) or their reduction by carbon monoxide (high temperature range).     

High-pressure crystallization of isotactic polypropylene droplets

Dispersions of isotactic polypropylene (PP) particles in polystyrene (PS) were produced by interfacially driven breakup of nanolayers in multilayered systems that were fabricated by means of layer-multiplying coextrusion. The droplet size was controlled by the individual PP layer thickness ranging from 12 to 200?nm. In addition, PP was melt blended with PS to produce PP droplets larger than those formed by breakup of nanolayers. The dispersions of PP particles in the PS matrix were melted and annealed under high pressure of 200?MPa. Only the largest PP droplets, with average sizes of 170?μm, crystallized predominantly in the γ form. In the 42-μm droplets obtained by breakup of 200?nm layers, a minor content of the γ form was found whereas the smaller droplets obtained by breakup of the thinner nanolayers contained the α form and/or the mesophase. The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure. It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.     

Cinnamon as a Useful Preventive Substance for the Care of Human and Plant Health

Cinnamon is widely used as a food spice, but due to its antibacterial and pharmacological properties, it can also be used in processing, medicine and agriculture. The word “Cinnamon” can refer to the plant, processed material, or an extract. It is sometimes used as a substance, and sometimes used as a mixture or as compounds or a group. This article reviews research into the effectiveness of various forms of cinnamon for the control of plant diseases and pests in crops and during storage of fruit and vegetables. Cinnamon acts on pests mainly as a repellent, although in higher doses it has a biocidal effect and prevents egg-laying. Cinnamon and its compounds effectively hinder bacterial and fungal growth, and the phytotoxic effects of cinnamon make it a possible herbicide. This article presents the wide practical use of cinnamon for various purposes, mainly in agriculture. Cinnamon is a candidate for approval as a basic substance with protective potential. In particular, it can be used in organic farming as a promising alternative to chemical pesticides for use in plant protection, especially in preventive treatments. The use of natural products is in line with the restriction of the use of chemical pesticides and the principles of the EU’s Green Deal.     

Insight into the Way the Content of Biologically Active Compounds in Meadowsweet Inflorescences (Filipendula ulmaria (L.) Maxim.) Is Shaped by Phytosociological Habitats

A collection of herbs from the natural environment remains not only a source of raw material but also provides evidence of chemical differentiation of the local populations. This work aimed at performing a phytosociological analysis of seven different stands of meadowsweet (Filipendula ulmaria (L.) Maxim.) occurrence. A determination of total phenolic compounds and salicylates and the antioxidant activity of dried meadowsweet inflorescences (Flos ulmariae) was also performed. Active chemical compounds in F. ulmaria inflorescences were related to chemotype and diversified between investigated populations. Geographical distance and variation in phytosociological locations affected chemical composition in different ways, shaping the content of biochemical compounds crucial for herbal material quality. The obtained results can be a valuable indicator for Nexo and Baligród populations, which are good genetic material for research, breeding, and cultivation due to their biochemical composition, especially with respect to salicylates, as major compounds of determining market quality of Flos ulmariae.     

Electric-field-induced polar biaxial order in a nontilted smectic phase of an asymmetric bent-core liquid crystal

A polarization reorientation process has been studied by means of optical second-harmonic generation in an optically uniaxial smectic phase of an asymmetric bent-core liquid crystal. A nontilted polar smectic order with a biaxial order is induced by applying an electric field to the uniaxial nonpolar smectic phase. This phenomenon was well simulated by the two-dimensional Langevin process, i.e., electric-field-induced continuous molecular reorientation against thermal agitation. The simulation suggests that about 200s of molecules form a polar domain and cooperatively respond to the applied field. The existence of the polar domains and their reorientation are consistent to the dielectric measurement; a high dielectric constant of about 60 at the kHz range is markedly suppressed by applying a bias field.