ESIPT-related origin of dual fluorescence in the selected model 1,3,4-thiadiazole derivatives

In our previous work, we discussed the emergence of the dual fluorescence phenomenon in selected compounds from the group of 1,3,4-thiadiazoles. The results obtained in a number of experimental studies, supported by [TD]DFT calculations, clearly indicated that the phenomenon of dual fluorescence stemmed from an overlap of several factors, including the correct conformation of the analyzed molecule and, very significantly in this context, aggregation effects. Where those two conditions were met, we could observe the phenomenon of intermolecular charge transfer (CT) and the emergence of electronic states responsible for long wave emissions. However, in light of the new studies presented in this paper, we were able, for the first time, to provide a specific theory for the effect of dual fluorescence observed in the analyzed group of 1,3,4-thiadiazoles. We present the results of spectroscopic measurements conducted for two selected analogues from the 1,3,4-thiadiazole group, both in polar and non-polar solvents, which clearly evidence (as we have already suspected in the past, albeit have not shown in publications to date) the possibility of processes related to emission from the tautomer formed in the process of excited state intramolecular proton transfer, which is responsible for the long-wavelength emissions observed in the selected analogues. The presented results obtained with the use of UV-Vis, fluorescence (stationary and time-resolved), FTIR, and Raman spectroscopy, as well as from calculations of dipole moment changes between the ground and excited state with the use of two derivatives with different structures of the resorcylic system, corroborated our standing hypothesis. At the same time, they excluded the presence of ground state keto forms of the analyzed analogues unless necessitated by the structure of the molecule itself. In this case, aggregation factors enhance the observed effects related to the dual fluorescence of the analyzed compounds (by way of AIE—aggregated induced emissions)

Non-typical fluorescence effects and biological activity in selected 1,3,4-thiadiazole derivatives : spectroscopic and theoretical studies on substituent, molecular aggregation, and pH effects

The below article presents the results of spectroscopic research, theoretical (time-dependent density functional theory (TD-DFT)), microbiological, and antioxidative calculations for three compounds from the group of 1,3,4-thiadiazoles: 2-amino-5-phenyl-1,3,4-thiadiazole (TB), 2-amino-5-(2-hydroxyphenyl)-1,3,4-thiadiazole (TS), 2-amino-5-(2-hydroxy-5-sulfobenzoyl)-1,3,4-thiadiazole (TSF). In the fluorescence emission spectra (TS) of solutions with varying concentrations of hydrogen ions, a particularly interesting effect of dual fluorescence was observed. The aforementioned effect was observed even more clearly in the environment of butan-1-ol, relative to the compound’s concentration. Depending on the modification of the resorcylic substituent (TS and TSF), we observed the emergence of two separate, partially overlapping, fluorescence emission spectra or a single emission spectrum. Interpretation of the obtained spectra using stationary and time-resolved spectroscopy allowed the correlation of the effect’s emergence with the phenomenon of molecular aggregation (of a particular type) as well as, above all, the structure of the substituent system. The overlap of said effects most likely induces the processes related to the phenomenon of charge transfer (in TS) and is responsible for the observed fluorescence effects. Also, the position of the –OH group (in the resorcylic ring) is significant and can facilitate the charge transfer (CT). The determinations of the changes in the dipole moment and TD-DFT calculations further corroborate the above assumption. The following paper presents the analysis (the first for this particular group of analogues) of the fluorescence effects relative to the changes in the structure of the resorcylic group combined with pH effects. The results of biological studies also indicate the highest pharmacological potential of the analogue in the case where the effects of dual fluorescence emission are observed, which predisposes this particular group of fluorophores as effective fluorescence probes or potential pharmaceuticals with antimycotic properties

The study of molecular structures of compounds that stimulate tumor cell growth

W niniejszej pracy przedstawiono widma wykonane techniką SERS (powierzchniowo wzmocniony efekt Ramana) fragmentów neurotransmitera bombezyny (BN): BN11-14, BN12-14 oraz BN13-14 zaadsorbowanych na koloidalnym złocie. Dodatkowo posłużono się widmami Ramana oraz widmami SERS wybranych fragmentów bombezyny zaadsorbowanych na koloidalnym srebrze przedstawionymi w wybranej publikacji.[7] Omówiono sposób wiązania się wyznaczonych peptydów z powierzchnią koloidalnego metalu oraz określono różnice w sposobie oddziaływania z wybraną powierzchnią. Jednym ze znaczących fragmentów w badanych widmach SERS był zakres związany z drganiami rozciągającymi C-S, świadczący o interakcji metioniny z powierzchnią oraz o możliwości przyjmowania różnych konformacji grupy S-CH3. Wykazano, że His12 bierze udział w wiązaniu z powierzchnią metalu za pomocą pierścienia imidazolowego. Porównując widma SERS fragmentów BN zaadsorbowanych na koloidalnym Au oraz Ag, zauważono różnice w sposobie oddziaływania peptydów z powierzchnią.This paper presents SERS (surface-enhanced Raman spectroscopy) spectra of various fragments of bombesin neurotransmitter (BN): BN11-14, BN12-14 and BN13-14 adsorbed to colloidal gold. Additionally, Raman spectra and SERS spectra of chosen bombesin fragments adsorbed to colloidal silver were used from the available publications.[7] A method of peptides bonding with the metal colloidal surface was discussed and the differences between interactions with the selected surface were later determined. One of the most prominent features of the SERS spectra was the band relating to C-S stretching vibrations, which is evidence of methionine interactions with the surface and of its possibility to adopt different conformations of the S-CH3. It was shown that His12 is involved in binding to the metal surface with the imidazole ring. Comparing the SERS spectra of BN fragments adsorbed to colloidal Au and Ag, the differences were observed in the way of peptides interacting with the surface

Synthesis of spherical ZrO2 as a support of active phase for total oxidation of toluene

W przedstawionej pracy zaprezentowano syntezę katalizatorów bazujących na dwóch typach sferycznych nośników: materiału rdzeniowo-powłokowego SiO2@ZrO2 oraz wydrążonych sfer @ZrO2. Zmodyfikowaną metodę Stöbera zastosowano w celu otrzymania ziaren krzemionkowych o monodyspersyjnym rozkładzie wielkości cząstek, które posłużyły jako szablon do naniesienia cienkiej powłoki tlenku cyrkonu. Sferyczny nośnik @ZrO2 uzyskano w wyniku selektywnego wytrawiania rdzenia krzemionkowego roztworem NaOH. Zarówno preparaty SiO2@ZrO2, jak i @ZrO2 poddano modyfikacji z wykorzystaniem techniki impregnacji pierwszej wilgotności roztworami azotanów(V) Cu(II) lub Co(II) oraz wygrzewaniu w 500 °C uzyskując katalizatory dotowane tlenkiem miedzi lub kobaltu (2,5-15,0 % mas. Cu lub Co). Zsyntetyzowanie materiały scharakteryzowano pod kątem ich stabilności termicznej (TG, DTG), struktury (XRD, XRF, UV-Vis-DR) oraz tekstury (niskotemperaturowa sorpcja azotu). Sferyczność materiałów potwierdzono wykonując zdjęcia skaningowym mikroskopem elektronowym. Korzystając z metody temperaturowo-programowanej redukcji wyznaczono redukowalność fazy aktywnej. Nośniki kalcynowane w 850 °C wykazywały obecność pożądanej fazy tetragonalnej tlenku cyrkonu. Otrzymane katalizatory przebadano w procesie całkowitego utleniania toluenu. Wykazano, że naniesienie fazy aktywnej (CuO, Co3O4) spowodowało znaczny wzrost aktywności katalitycznej. Najlepszymi katalizatorami okazały się preparaty CuO/@ZrO2.In the presented work, the synthesis of catalysts based on two types of spherical supports: core-shell materials SiO2@ZrO2 and hollow zirconia spheres @ZrO2 is described. The modified Stöber method was used to obtain silica grains with a monodisperse size distribution, which were used as supports for deposition of thin zirconium shell. Spherical @ZrO2 was obtained by the selective extraction of SiO2 core with a NaOH solution. Both SiO2@ZrO2 and @ZrO2 supports were subsequently modified with an aqueous solution of copper(II) and cobalt(II) nitrate using the incipient wetness technique to obtain after calcination at 500 °C the catalysts containing 2,5 - 15,0 wt.% Cu or Co. The synthesized materials were characterized in terms of thermal stability (TG, DTG), structure (XRD, XRF, UV-vis-DR) and texture (low temperature sorption of nitrogen). Scanning electron microscope was used to illustrate the spherical morphology of the synthesized materials. Reducibility of the active phase was determined by temperature-programmed reduction. It was found that the expected tetragonal zirconia phase was formed by calcination at 850 °C. The obtained catalysts were tested in the total oxidation of toluene. It was shown that the introduction of active phase (CuO, Co3O4) resulted in a significant increase of the catalytic activity. The most active catalysts were the CuO/@ZrO2 samples

Structure and Physical Properties of Cardamonin: A Spectroscopic and Computational Approach

This is the first study of the crystal structure of cardamonin (CA) confirmed using single-crystal XRD analysis. In the crystal lattice of CA, two symmetry independent molecules are linked by hydrogen bonds within the layers and by the π···π stacking interactions in the columns which lead to the occurrence of two types of conformations among the CA molecules in the crystal structure. To better understand the stability of these arrangements in both crystals and the gaseous phase, seven different CA dimers were theoretically calculated. The molecular structures were optimized using density functional theory (DFT) at the B3LYP/6–311G+(d,p) level and the spectroscopic results were compared. It was found that the calculated configurations of dimer I and III were almost identical to the ones found in the CA crystal lattice. The calculated UV-Vis spectra for the CA monomer and dimer I were perfectly consistent with the experimental spectroscopic data. Furthermore, enhanced emissions induced by aggregated CA molecules were registered in the aqueous solution with the increase of water fractions. The obtained results will help to further understand the relation between a variety of conformations and the biological properties of CA, and the results are also promising in terms of the applicability of CA as a bioimaging probe to monitor biological processes

The Visibility of Changes in the Antioxidant Compound Profiles of Strawberry and Raspberry Fruits Subjected to Different Storage Conditions Using ATR-FTIR and Chemometrics

Strawberry cultivars Portola and Enduro, as well as raspberry cultivars Enrosadira and Kwazi, were evaluated for their antioxidant potential after treatment with gaseous ozone and different refrigeration storage conditions. Their antioxidant capacity was investigated with ABTS and DPPH methods, and the chemical composition was determined by measuring the total phenolic (TPC) and flavonoid (TFC) compounds. The classification of different samples of berry puree was influenced significantly by both the cultivars and the refrigeration storage method. Moreover, FTIR spectroscopy coupled with chemometrics was used as an alternative technique to conventional methods to determine the chemical composition of strawberries and raspberries. The chemometric discrimination of samples was achieved using principal component analysis (PCA), hierarchical clustering analysis (HCA) and linear discriminant analysis (LDA) modelling procedures performed on the FTIR preprocessed spectral data for the fingerprint region (1800–500 cm−1). The fingerprint range between 1500 and 500 cm−1, corresponding to deformation vibrations from polysaccharides, pectin and organic acid content, had a significant impact on the grouping of samples. The results obtained by PCA-LDA scores revealed a clear separation between four classes of samples and demonstrated a high overall classification rate of 97.5% in differentiating between the raspberry and strawberry cultivars

Isolation of Chitin from Black Soldier Fly (Hermetia illucens) and Its Usage to Metal Sorption

Chitin has become a desirable raw material used in various areas of life. The black soldier fly (Hermetia illucens) can be a source of this substance. In the literature, there are many methods of obtaining chitin but there is no one universal method of isolating it. In this publication, we present various procedures for the isolation of chitin from H. illucens pupal exuviae. The obtained chitin variants were characterized using different techniques (optical and confocal microscopy, FTIR, XRD, EDX, thermogravimetric analysis). The tested chitin isolated with an efficiency of 5.69–7.95% was the α form with a crystallinity degree of 60% and maximum degradation temperature of 392 °C. Furthermore, we characterized the nickel ion biosorption process on chitin and proposed the mechanism of this process to be ion exchange and complexation. There have been no such studies thus far on the isolation of chitin from H. illucens exuviae or on the biosorption of nickel ions on this type of biosorbent. The conducted research can be used to develop the application of chitin as a metal biosorbent that can be obtained with relatively high efficiency and good sorption properties

Impact of Metal Nanoparticles on the Phytochemical and Antioxidative Properties of Rapeseed Oil

The agricultural uses of nanoparticles continue to be considered as innovative methods that require more in-depth research into their impact on product quality. In our study, we investigated the effects of fertilizers containing metal nanoparticles (silver AgNPs and copper CuNPs) during the plant growth stage of winter rape cultivation, and in most experimental variants, with the exception of the (x2) application of AgNPs, we observed a decrease in the mass of one thousand seeds (MTS). The obtained result was 11.55% higher relative to the control sample in 2019, and also increased after the (x1) 4.36% and (x2) 11.11% application of CuNPS in 2020. The analyzed oxidative stability of the oil increased in both experimental years (2019–2020), with the highest values recorded after the (x1) and (x2) application of CuNPS—4.94% and 8.31%, respectively, in the first year of cultivation, and after the (x2) application of CuNPS—12.07% in the subsequent year. It was also observed that the content of polyphenols, flavonoids, squalene, tocopherols α and δ, chlorophylls, and carotenoids increased in the oil. Moreover, spectral FTIR analysis was performed on the oil samples obtained from cultivations sprayed with solutions containing Ag or Cu nanoparticles and revealed changes in several spectral regions with the maxima at ~1740, 1370, 1230, and ~1090 cm−1. Additionally, a FTIR analysis conducted in combination with multivariate analysis allowed us to classify the studied oils into the most similar groups and to study the structure of data variability. The conducted analyses revealed that the use of nanoparticles resulted in decreased size of the produced seeds and improved antioxidative properties of rapeseed oil

Naturally Occurring Chalcones with Aggregation-Induced Emission Enhancement Characteristics

In this paper, the natural chalcones: 2′-hydroxy-4,4′,6′-trimethoxychalcone (HCH), cardamonin (CA), xanthohumol (XN), isobavachalcone (IBC) and licochalcone A (LIC) are studied using spectroscopic techniques such as UV–vis, fluorescence spectroscopy, scanning electron microscopy (SEM) and single-crystal X-ray diffraction (XRD). For the first time, the spectroscopic and structural features of naturally occurring chalcones with varying numbers and positions of hydroxyl groups in rings A and B were investigated to prove the presence of the aggregation-induced emission enhancement (AIEE) effect. The fluorescence studies were carried out in the aggregate form in a solution and in a solid state. As to the results of spectroscopic analyses conducted in the solvent media, the selected mixtures (CH3OH:H2O and CH3OH:ethylene glycol), as well as the fluorescence quantum yield (ϕF) and SEM, confirmed that two of the tested chalcones (CA and HCH) exhibited effective AIEE behaviour. On the other hand, LIC showed a large fluorescence quantum yield and Stokes shift in the polar solvents and in the solid state. Moreover, all studied compounds were tested for their promising antioxidant activities via the utilisation of 1,1- diphenyl-2-picrylhydrazyl as a free-radical scavenging reagent as well as potential anti-neurodegenerative agents via their ability to act as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Finally, the results demonstrated that licochalcone A, with the most desirable emission properties, showed the most effective antioxidant (DPPH IC50 29%) and neuroprotective properties (AChE IC50 23.41 ± 0.02 μM, BuChE IC50 42.28 ± 0.06 μM). The substitution pattern and the biological assay findings establish some relation between photophysical properties and biological activity that might apply in designing AIEE molecules with the specified characteristics for biological application

Classification of Honey Powder Composition by FTIR Spectroscopy Coupled with Chemometric Analysis

Fourier transform infrared spectroscopy (FTIR) in connection with chemometric analysis were used as a fast and direct approach to classify spray dried honey powder compositions in terms of honey content, the type of diluent (water or skim milk), and carrier (maltodextrin or skim milk powder) used for the preparation of feed solutions before spray drying. Eleven variants of honey powders containing different amounts of honey, the type of carrier, and the diluent were investigated and compared to pure honey and carrier materials. Chemometric discrimination of samples was achieved by principal component analysis (PCA), hierarchical clustering analysis (HCA), linear discriminant analysis (LDA), and partial least squares-discriminant analysis (PLS-DA) modelling procedures performed on the FTIR preprocessed spectral data for the fingerprint region (1800–750 cm−1) and the extended region (3600–750 cm−1). As a result, it was noticed that the type of carrier is a significant factor during the classification of different samples of powdered multifloral honey. PCA divided the samples based on the type of carrier, and additionally among maltodextrin-honey powders it was possible to distinguish the type of diluent. The result obtained by PCA-LDA and PLS-DA scores yielded a clear separation between four classes of samples and showed a very good discrimination between the different honey powder with a 100.0% correct overall classification rate of the samples