Ligand Exchange Reaction between Ferrocene and Multiwalled Carbon Nanotubes: A Contemporary Approach.

Ligand exchange reaction (LER) between carbon nanoparticles and ferrocene (Cp2Fe) was conducted several times, but there was no convincing evidence of half-sandwich CpFe+ coordination to multiwalled carbon nanotubes (MWCNT). In this study, MWCNT is modified by LER with ferrocene using AlCl3/Al as a catalytic system. The modified MWCNT (Fc-MWCNT) are investigated for better understanding of the processes taking place on the surface of MWCNT using different spectroscopic and electrochemical methods. The formation of the Fe-C covalent bond between CpFe+ and MWCNT is confirmed by changes in the Raman spectrum of Fc-MWCNT compared to pristine MWCNT. The densest structure of Fc-MWCNT is investigated by transmission electronic microscopy. According to density-functional theory calculations of the model interaction between Fe and coronene, the Fe-C bond length is 2.1687-2.1855 Å. X-ray photoelectron spectroscopy also confirms the coordination of the Fe atom to MWCNT by analysis of oxidation states of Fe 2p and deconvolution of C 1s. Utilization of cyclic voltammetry corroborated MWCNT modification via LER. These data are important for both theoretical and practical applications due to increased interest in LER-modified compounds in different areas including thermoelectric devices, sensors, and its potential application in the field of molecular machine construction.

All-in-One Photoactivated Inhibition of Butyrylcholinesterase Combined with Luminescence as an Activation and Localization Indicator: Carbon Quantum Dots@Phosphonate Hybrids.

Photopharmacology is a booming research area requiring a new generation of agents possessing simultaneous functions of photoswitching and pharmacophore. It is important that any practical implementation of photopharmacology ideally requires spatial control of the medicinal treatment zone. Thus, advances in the study of substances meeting all the listed requirements will lead to breakthrough research in the coming years. In this study, CQDs@phosphonate nanohybrids are presented for the first time and combine biocompatible and nontoxic luminescent carbon quantum dots (CQDs) with photoactive phosphonate enabling inhibition of butyrylcholinesterase (BChE), which is a prognostic marker of numerous diseases. The conjunction of these components in hybrids maintains photoswitching and provides enhancement of BChE inhibition. After laser irradiation with a wavelength of 266 nm, CQDs@phosphonate hybrids demonstrate a drastic increase of butyrylcholinesterase inhibition from 38% up to almost 100% and a simultaneous luminescence decrease. All the listed hybrid properties are demonstrated not only for in vitro experiments but also for complex biological samples, i.e., chicken breast. Thus, the most important achievement is the demonstration of hybrids characterized by a remarkable combination of all-in-one properties important for photopharmacology: (i) bioactivity toward butyrylcholinesterase inhibition, (ii) strong change of inhibition degree as a result of laser irradiation, luminescence as an indicator of (iii) bioactivity state, and of (iv) spatial localization on the surface of a sample.

Investigation of Spectroscopic Peculiarities of Ergot-Infected Winter Wheat Grains.

Wheat has played an important role in human agriculture since ancient times. Increasing rates of processed wheat product fabrication require more and more laboratory studies of product quality. This, in turn, requires the use, in production and in field conditions, of sufficiently accurate, fast and relatively low-cost quality control methods, including the detection of fungal diseases. One of the most widespread fungal diseases of wheat in the world is ergot caused by the fungi genus Claviceps. Optical methods are promising for this disease identification due to the relative ease of implementation and the possibility of performing fast analyses in large volumes. However, for application in practice, it is necessary to identify and substantiate characteristic spectral markers that make it possible to judge the sample contamination. In this regard, within the framework of this study, the methods of IR absorption spectroscopy in the MIR region and reflection spectroscopy in the UV-vis-NIR ranges, as well as luminescence spectroscopy, were used to study ergot-infected grains of winter wheat of the "Moskovskaya 56" cultivar. To justify the choice of the most specific spectral ranges, the methods of chemometric analysis with supervised classification, namely PCA-LDA and PCA-SVM, were applied. The possibility of separating infected grains according to the IR absorption, reflection spectra in the UV-vis-NIR ranges and visible luminescence spectra was tested.

Photoswitchable Phosphonate-Fullerene Hybrids with Cholinesterase Activity.

Modern progress in photopharmocology calls for new generation of compounds joining bioactivity, photoswitchable properties and high selectivity of response to light wavelength. Introduced here, phosphonate-fullerene hybrids are the first representatives of such compounds. Phosphonate-fullerene hybrids were synthesized on a base of fullerene C60 and organophosphates with the function of photoswitchable cholinesterase activity-phosphorylated thiazolotriazole and aminomalonate compounds and studied with FTIR, UV-VIS spectroscopy and IPC-micro neurotoxin amperometric analysis. As a result of spectroscopic and bioactivity characterization, it was not only demonstrated butyrylcholinesterase (BuChE) inhibition increase in phosphonate-fullerene hybrids compared with pure phosphonates but also pronounced response of inhibition degree to laser irradiation of hybrids. It was found opposite behavior of hybrids as a result of laser irradiation-BuChE inhibition drop-off for thiazolotriazole-fullerene and pronounced growth for aminomalonate-fullerene. The other remarkable peculiarity of presented phosphonate-fullerene hybrids is high selectivity of inhibition change degree to laser wavelength (266 or 325 nm).

DFT Modelling of Molecular Structure, Vibrational and UV-Vis Absorption Spectra of T-2 Toxin and 3-Deacetylcalonectrin.

This paper discusses the applicability of optical and vibrational spectroscopies for the identification and characterization of the T-2 mycotoxin. Vibrational states and electronic structure of the T-2 toxin molecules are simulated using a density-functional quantum-mechanical approach. A numerical experiment aimed at comparing the predicted structural, vibrational and electronic properties of the T-2 toxin with analogous characteristics of the structurally similar 3-deacetylcalonectrin is performed, and the characteristic spectral features that can be used as fingerprints of the T-2 toxin are determined. It is shown that theoretical studies of the structure and spectroscopic features of trichothecene molecules facilitate the development of methods for the detection and characterization of the metabolites.

Copper oxalate formation by lichens and fungi.

The present work focuses on the revealing the patterns of copper oxalates formation under the influence of lichens and fungi by combination of the results of field studies and model experiments. These findings create the scientific basis for the potential microbial technology applications (ore enrichment, monuments conservation, environment bioremediation, etc.). Copper oxalate moolooite Cu(C2O4)·H2O was discovered in saxicolous lichen Lecidea inops on the weathered chalcopyrite ore of Voronov Bor deposit (Central Karelia, Russia). Bioinspired syntheses of moolooite and wheatleyite Na2Cu(C2O4)2 2H2O with the participation of the microscopic fungi Aspergillus niger (active producer of oxalic acid) were carried out on weathered Cu-ore from the Voronov Bor deposit. It was shown that morphology of moolooite crystals is controlled both by the underlying rock and by the species composition of microorganisms. Iron ions (sourced from the underlying rock) in the crystallization medium inhibits the moolooite formation. The observed intensive dissolution of moolooite crystals are well explained by washing effect of the intratalline solutions which depends on repeatedly dehydration / rehydration cycles in the lichens. Joint interpretation of original and published data shows that moolooite along with other cooper oxalates are biominerals.

Laser-induced twisting of phosphorus functionalized thiazolotriazole as a way of cholinesterase activity change.

Herein, the synthesis, design, and the physicochemical characterization of phosphorus functionalized thiazolotriazole (PFT) compound are presented. The PFT tests on the biological activity revealed butyrylcholinesterase inhibition that was confirmed and explained with molecular docking studies. The pronounced reduction of optical density and biological activity was found as a result of irradiation of the PFT water solution with laser beam at wavelength 266 nm. The observed phenomenon was explained on the base of molecular dynamics, docking, and density functional theory modeling by the formation of PFT conformers via laser-induced phosphonate group twisting. The reorganization of the PFT geometry was found to be a reason of butyrylcholinesterase inhibition mechanism change and the site-specificity loss. These results demonstrate that PFT combines photoswitching and bioactive properties in one molecule that makes it promising as a molecular basis for the further design of bioactive substances with photosensitive properties based on the mechanism of the phosphonate group phototwisting.

Spectral properties of triphenyltin chloride toxin and its detectivity by SERS: Theory and experiment.

The triphenyltin chloride (TPhTCl) molecular structure was investigated by Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) and the density functional theory (DFT) modeling. Several conformers with different ordering of the benzene rings were determined in the gas phase and in the dimethyl sulfoxide (DMSO) medium. It was shown that the dihedral angles describing such ordering can change under room conditions. Charge distribution of conformers was analyzed with the use of electrostatic potential (ESP) maps. The formation of weak hydrogen bonds and the rearrangement of the benzene rings to form a complex with negatively charged parts of other molecules were proven by ESP maps. Basing on the results of ESP map analysis, it can be assumed that interaction of TPhTCl molecule with metal cluster results in orientation ordering of the benzene rings. This conclusion was confirmed by modeling the atomistic and electronic structure of TPhTCl molecule adsorbed by the Au8 cluster, as well as by observing the intense SERS peaks assigned to vibrations of the benzene rings of TPhTCl molecule adsorbed on the surface of the gold inverse opals.

Nanoporous water oxidation electrodes with a low loading of laser-deposited Ru/C exhibit enhanced corrosion stability.

For the oxidation of water to dioxygen, oxide-covered ruthenium metal is known as the most efficient catalyst, however, with limited stability. Herein, we present a strategy for incorporating a Ru/C composite onto a novel nanoporous electrode surface with low noble metal loading and improved stability. The Ru/C is coated on the pore walls of anodic alumina templates in a one-step laser-induced deposition method from Ru3(CO)12 solutions. Scanning electron microscopy proves the presence of a continuous Ru/C layer along the inner pore walls. The amorphous material consists of metallic Ru incorporated in a carbonaceous C matrix as shown by X-ray diffraction combined with Raman and X-ray photoelectron spectroscopies. These porous electrodes reveal enhanced stability during water oxidation as compared to planar samples at pH 4. Finally, their electrocatalytic performance depends on the geometric parameters and is optimized with 13 µm pore length, which yields 2.6 mA cm-2, or 49 A g-1, at η = 0.20 V.

Adjusting Interfacial Chemistry and Electronic Properties of Photovoltaics Based on a Highly Pure Sb2S3 Absorber by Atomic Layer Deposition.

The combination of oxide and heavier chalcogenide layers in thin film photovoltaics suffers limitations associated with oxygen incorporation and sulfur deficiency in the chalcogenide layer or with a chemical incompatibility which results in dewetting issues and defect states at the interface. Here, we establish atomic layer deposition (ALD) as a tool to overcome these limitations. ALD allows one to obtain highly pure Sb2S3 light absorber layers, and we exploit this technique to generate an additional interfacial layer consisting of 1.5 nm ZnS. This ultrathin layer simultaneously resolves dewetting and passivates defect states at the interface. We demonstrate via transient absorption spectroscopy that interfacial electron recombination is one order of magnitude slower at the ZnS-engineered interface than hole recombination at the Sb2S3/P3HT interface. The comparison of solar cells with and without oxide incorporation in Sb2S3, with and without the ultrathin ZnS interlayer, and with systematically varied Sb2S3 thickness provides a complete picture of the physical processes at work in the devices.

Raman fingerprints for unambiguous identification of organotin compounds.

Raman spectra of the different ecotoxicants such as perfluorooctane sulfonate acid, organotin compounds of different families tributyl-, and triphenyl-, as well as chemically close compounds belonging to the same family - such as mono-, di-, and tributyl organotin compounds were analyzed. The comprehensive Raman spectra analysis allowed suggesting the identification scheme for clear recognition of the toxins family and the following intra-group specification. Possibility of unambiguous toxins detection and identification was demonstrated also for complex mixtures of various toxins on a base of control of characteristic peak groups, which can be considered as Raman fingerprints of the listed environmentally hazardous substances.

Design Rules for Oxygen Evolution Catalysis at Porous Iron Oxide Electrodes: A 1000-Fold Current Density Increase.

Nanotubular iron(III) oxide electrodes are optimized for catalytic efficiency in the water oxidation reaction at neutral pH. The nanostructured electrodes are prepared from anodic alumina templates, which are coated with Fe2 O3 by atomic layer deposition. Scanning helium ion microscopy, X-ray diffraction, and Raman spectroscopy are used to characterize the morphologies and phases of samples submitted to various treatments. These methods demonstrate the contrasting effects of thermal annealing and electrochemical treatment. The electrochemical performances of the corresponding electrodes under dark conditions are quantified by steady-state electrolysis and electrochemical impedance spectroscopy. A rough and amorphous Fe2 O3 with phosphate incorporation is critical for the optimization of the water oxidation reaction. For the ideal pore length of 17 µm, the maximum catalytic turnover is reached with an effective current density of 140 µA cm-2 at an applied overpotential of 0.49 V.