Photoinduced dynamics of a cyanine dye: parallel pathways of non-radiative deactivation involving multiple excited-state twisted transients

Cyanine dyes are broadly used for fluorescence imaging and other photonic applications. 3,3′-Diethylthiacyanine (THIA) is a cyanine dye composed of two identical aromatic heterocyclic moieties linked with a single methine, –CH. The torsional degrees of freedom around the methine bonds provide routes for non-radiative decay, responsible for the inherently low fluorescence quantum yields. Using transient absorption spectroscopy, we determined that upon photoexcitation, the excited state relaxes along two parallel pathways producing three excited-state transients that undergo internal conversion to the ground state. The media viscosity impedes the molecular modes of ring rotation and preferentially affects one of the pathways of non-radiative decay, exerting a dominant effect on the emission properties of THIA. Concurrently, the polarity affects the energy of the transients involved in the decay pathways and further modulates the kinetics of non-radiative deactivation.     

Enhanced In situ Activity of Peroxidases and Lignification of Root Tissues after Exposure to Non-Thermal Plasma Increases the Resistance of Pea Seedlings

Improving the germination of economically important crops and the condition of young plants is a major challenge currently facing agricultural practice. Pea (Pisum sativum L.) is one of the four most important cultivated legumes, along with groundnut (Arachis hypogaea L.), soybean (Glycine max L.) and beans (Phaseolus vulgaris L.). Due to the high protein content (23–33%), there is an interest in growing this crop as a source of protein for humans and animals. In this study, we focused on the effect of Cold Atmospheric Pressure Plasma (CAPP) on the decontamination and germination of pea seeds, on young seedling growth and production parameters, and on increasing their resistance and mechanical strength. We can state that germination increased by 10 to 25% after plasma treatment, and the most significant decontamination effect was detected when using non-thermal plasma generated in the ambient air (A-variants) and in the nitrogen atmosphere (N-variants). The increased in situ activity of peroxidases (POX) in the cell walls of A-variants and N-variants is also closely related to the increase in the mechanical strength of the cell walls and thus contributes to the higher resistance of these seedlings. This is also illustrated by the differences in lignin deposition among the different variants after CAPP treatment. To our knowledge, this is the first study concerning the influence of CAPP on the lignification of root tissues and on increasing the strength and resistance of plants.

     

Database Survey of Single-and-Half Phosphorus–Oxygen Bonds in Salts with the C2PO2 Segment: Crystal Structure of [NH2C5H4NH][(C6H5)2P(O)(O)]⋅2H2O

Crystallography Reports - For structures with a C2PO2 skeleton, a comparison of “single-and-half” phosphorus–oxygen bonds with single and double phosphorus–oxygen bonds is...     

Influence of Solution Volume on the Dissolution Rate of Silicon Dioxide in Hydrofluoric Acid

Experimental data and modeling of the dissolution of various Si/SiO₂ thermal coatings in different volumes of hydrofluoric acid (HF) are reported. The rates of SiO₂‐film dissolution, measured by means of various electrochemical techniques, and alteration in HF activity depend on the thickness of the film coating. Despite the small volumes (0.6–1.2 mL) of the HF solution, an effect of SiO₂‐coating thickness on the dissolution rate was detected. To explain alterations detected in HF activity after SiO₂ dissolution, spectroscopic analyses (NMR and FTIR) of the chemical composition of the solutions were conducted. This is associated with a modification in the chemical composition of the HF solution, which results in either the formation of an oxidized species in solution or the precipitation of dissolution products. HF₂^? accumulation in the HF solution, owing to SiO₂ dissolution was identified as the source of the chemical alteration.     

Modern approaches to chemical toxicity screening

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Preparation of α-terpineol and perillyl alcohol using zeolites beta

The preparation of α-terpineol by direct hydration of limonene catalyzed by zeolites beta was studied. The same catalyst was used to prepare perillyl alcohol by isomerization of β-pinene oxide in the presence of water. The aim was to optimize the reaction conditions to achieve high conversions of starting material and high selectivity to the desired products. In the case of limonene, it was found that the highest selectivity to α-terpineol was 88% with conversion of 36% under the conditions: 50 wt% of catalyst beta 25, 10% aqueous acetic acid (10 mL) (volume ratio limonene:H₂O?=?1:4.5), temperature 50 °C, after 24 h. In the case of β-pinene oxide, it was found that the highest selectivity to perillyl alcohol, which was 36% at total conversion, was obtained in the reaction under the following conditions: dimethyl sulfoxide as solvent (volume ratio β-pinene oxide:DMSO?=?1:5), catalyst beta 25 without calcination (15 wt%), demineralized water (molar ratio β-pinene oxide:H₂O?=?1:8), temperature 70 °C, 3 h. The present study shows that the studied reactions are suitable for the selective preparation of chosen compounds.

     

Iron-modified zeolite BETA: efficient catalyst in methyllaurate, 2-hexyl-1,3-dioxolane, 4-methyl-2-propyltetrahydro-2H-pyran-4-ol and 4-methyl-2-phenyl-tetrahydro-2H-pyran-4-ol synthesis

Research on Chemical Intermediates - Several types of modified zeolite BETA38 with different iron loading were prepared. Prepared materials were characterized using different techniques (XRD, XRF,...