Excitation-Dependent Fluorescence Helps to Indicate Fungal Contamination of Aquatic Environments and to Differentiate Filamentous Fungi

Fungal contamination of aquatic environments can lead to an adverse impact on the environment and human health. (1) The search for fast, inexpensive and appropriate methods for detection of fungi is very moving rapidly due to their significant impact on ecosystem functions and human health. (2) We focused on examination of fluorescence proxies able to distinguish chromophoric matter occurring in different fungi. Spectroscopic studies were performed on five strains of filamentous fungi: Trichoderma harzianum, Fusarium solani, Alternaria alternata, Cladosporium cladosporioides and Aspergillus terreus. (3) The results showed that most of the fungal autofluorescence was emitted by amino acids, melanin-like compounds, NAD(P)H and flavins. The spectra of five fungal species cultivated as planktonic or surface-associated forms turned out to be different. Protein fluorescence can be used to detect general microbial contamination. Presence of excitation wavelength dependent mode and the “blue shift” of fluorescence (emission bands 400–500 nm) can be suggested as specific feature of fluorescence of fungal melanin-containing samples. (4) The determination based on fluorescence spectra obtained at a certain excitation/emission wavelengths pair and at whole excitation-emission matrices (EEMs) coupled to principal component analysis (PCA) algorithms as a tool of improving detection capabilities can be suggested to enable fast and inexpensive monitoring of fungal contamination of aquatic environments

Evaluation of aliphatic/aromatic compounds and fluorophores in dissolved organic matter of contrasting natural waters by SEC-HPLC with multi-wavelength absorbance and fluorescence detections

International audienc

Excitation-Dependent Fluorescence Quantum Yield for Freshwater Chromophoric Dissolved Organic Matter from Northern Russian Lakes

Advanced fluorescence analysis within the wide range of excitation wavelengths from 230 to 510 nm accompanied with chromatography was used to study natural chromophoric dissolved organic matter (CDOM) from three freshwater Karelian lakes. The influence of excitation wavelength (λex) on fluorescence quantum yield and emission maximum position was determined. The CDOM fluorescence quantum yield has reached a minimum at λex∼270–280 nm and a maximum at λex∼340–360 nm. It was monotonously decreasing after 370 nm towards longer excitation wavelengths. Analytical reversed-phase high-performance liquid chromatography with multiwavelength fluorescence detector characterized distribution of fluorophores between hydrophilic/hydrophobic CDOM parts. This technique revealed “hidden” protein-like fluorophores for some CDOM fractions, in spite of the absence of protein-like fluorescence in the initial CDOM samples. The humic-like fluorescence was documented for all hydrophilic and hydrophobic CDOM chromatographic peaks, and its intensity was decreasing along with peaks’ hydrophobicity. On contrary, the protein-like fluorescence was found only in the hydrophobic peaks, and its intensity was increasing along with peaks’ hydrophobicity. This work provides new data on the CDOM optical properties consistent with the formation of supramolecular assemblies controlled by association of low-molecular size components. In addition, these data are very useful for understanding the CDOM function in the environment

CDOM Optical Properties and DOC Content in the Largest Mixing Zones of the Siberian Shelf Seas

Notable changes in the Arctic ecosystem driven by increased atmospheric temperature and ice cover reduction were observed in the last decades. Ongoing environmental shifts affect freshwater discharge to the Arctic Ocean, and alter Arctic land-ocean fluxes. The monitoring of DOC distribution and CDOM optical properties is of great interest both from the point of view of validation of remote sensing models, and for studying organic carbon transformation and dynamics. In this study we report the DOC concentrations and CDOM optical characteristics in the mixing zones of the Ob, Yenisei, Khatanga, Lena, Kolyma, and Indigirka rivers. Water sampling was performed in August–October 2015 and 2017. The DOC was determined by high-temperature combustion, and absorption coefficients and spectroscopic indices were calculated using the seawater absorbance obtained with spectrophotometric measurements. Kara and Laptev mixing zones were characterized by conservative DOC behavior, while the East Siberian sea waters showed nonconservative DOC distribution. Dominant DOM sources are discussed. The absorption coefficient aCDOM (350) in the East Siberian Sea was two-fold lower compared to Kara and Laptev seawaters. For the first time we report the DOC content in the Khatanga River of 802.6 µM based on the DOC in the Khatanga estuary

High-performance size exclusion chromatography with online fluorescence and multi-wavelength absorbance detection for isolation of high-purity carbon dots fractions, free of non-fluorescent material

International audienc

Effect of Heterocyclic Ring on LnIII Coordination, Luminescence and Extraction of Diamides of 2,2′-Bipyridyl-6,6′-Dicarboxylic Acid

We have synthesized and examined several complexes of lanthanides with diamides of 2,2′-bipyridyl-6,6′-dicarboxylic acid bearing various hetaryl-based side chains for the elucidation of the effect of the heterocycle on the structure and properties of the ligands. The multigram scale methods for the preparation of various N-alkyl-hetaryls and their diamides were developed. The solid state structure of 6-methyl-2-pyridylamide of 2,2′-bipyridyl-6,6′-dicarboxylic acid possesses a flat structure where the conformation is completely different from that previously observed for N-alkylated 2,2′-bipyridyl-6,6′-dicarboxamides and 2,6-pyridinedicarboxamides. The complexes of new ligands were synthesized and NMR and X-Ray studied their structure in solution and solid state. The results demonstrate that complexes possess the same structures both in solid state and in solution. Stability constants of the complexes were less when comparing with dimethyl-substituted diamides, but higher than for unsubstituted dianilide. Contrarily, the extraction ability of 2-pyridyl-diamide is significantly lower than for corresponding anilide. Specific interaction of extractant with solvent molecules, which is not available for electron-sink pyridine amides, can explain this. The luminescence of new Eu complexes was significantly higher than for all previously 2,2′-bipyridyl-6,6′-dicarboxamides and QY reaches 18%. Asymmetry ratios of Eu complexes were 25% higher when compared other complexes with 2,2′-bipyridyl-6,6′-dicarboxamides, which indicates large deviation from the inversion center

Sterical Driving Minor Actinide Selectivity of Bi-pyridyl Diamides: Ortho- vs. Para-Substitution

Hybrid donor extractants are a promising class of compounds for the separation of trivalent actinides and lanthanides. In this paper, we present a new ligand from the bipyridyl-dicarboxylic acid diamide family—N,N’-diethyl-N,N’-bis(2,4,5-trimethylphenyl)-[2,2’-bipyridine]-6,6’-dicarboxamide. The synthesis of N-ethyl-2,4,5-trimethylaniline from pseudocumene by selective acetylation is presented. The target ligand was obtained using this aminylene. Chemical synthesis of its complexes with Ln(NO3)3 and their spectroscopic analysis showed that the structure of the complexes is near to the corresponding structures of well-known di-methylated dianilides. A series of studies on the photophysical, complexing, and extraction properties of this ligand and its complexes were carried out. It was shown that the extraction system based on this ligand can selectively isolate americium from the solution of high-level waste imitator

Sterical Driving Minor Actinide Selectivity of Bi-pyridyl Diamides: Ortho- vs. Para-Substitution

Hybrid donor extractants are a promising class of compounds for the separation of trivalent actinides and lanthanides. In this paper, we present a new ligand from the bipyridyl-dicarboxylic acid diamide family—N,N’-diethyl-N,N’-bis(2,4,5-trimethylphenyl)-[2,2’-bipyridine]-6,6’-dicarboxamide. The synthesis of N-ethyl-2,4,5-trimethylaniline from pseudocumene by selective acetylation is presented. The target ligand was obtained using this aminylene. Chemical synthesis of its complexes with Ln(NO3)3 and their spectroscopic analysis showed that the structure of the complexes is near to the corresponding structures of well-known di-methylated dianilides. A series of studies on the photophysical, complexing, and extraction properties of this ligand and its complexes were carried out. It was shown that the extraction system based on this ligand can selectively isolate americium from the solution of high-level waste imitator

Raman Spectroscopy of Water–Ethanol Solutions: The Estimation of Hydrogen Bonding Energy and the Appearance of Clathrate-like Structures in Solutions

The structure of aqueous alcohol solutions at the molecular level for many decades has remained an intriguing topic in numerous theoretical and practical investigations. The aberrant thermodynamic properties of water–alcohol mixtures are believed to be caused by the differences in energy of hydrogen bonding between water–water, alcohol–alcohol, and alcohol–water molecules. We present the Raman scattering spectra of water, ethanol, and water–ethanol solutions with 20 and 70 vol % of ethanol thoroughly measured and analyzed at temperatures varying from −10 to +70 °C. Application of the MCR-ALS method allowed for each spectrum to extract contributions of molecules with different strengths of hydrogen bonding. The energy (enthalpy) of formation/weakening of hydrogen bonds was calculated using the slope of Van’t Hoff plot. The energy of hydrogen bonding in 20 vol % of ethanol was found the highest among all the samples. This finding further supports appearance of clathrate-like structures in water–ethanol solutions with concentrations around 20 vol % of ethanol