Fullerene-Tetrabenzofluorene (C60-TBF) in Multivalent Photosensitisation for Enhanced ZnO-based Photo-catalysts: Mono vs. Hexakis Adduct

Photo-catalysts offer a simple catalytic method with widespread applications like degradation of polluting dyes, hydrogen generation from water, etc., in the presence of a photon source like sunlight. The development of a second-generation photo-catalyst in the form of a nanocomposite is an integral part of research to improve the practical usefulness and efficiency of the process. A systematic study using the active material with controlled functional groups is required to understand the process in detail as well as to develop efficient photocatalytic systems. In this paper, we report the design, synthesis, detailed physicochemical studies, and self-assembly of interesting materials where fullerenes have been functionalized with polycyclic, aromatic, conjugated, butterfly-shaped molecules like Tetrabenzofluorene (TBF) using a well-known click chemistry approach. Detailed analyses using spectroscopic, electrochemical, and microscopic or X-ray diffraction (single crystal) techniques were undertaken for a clear understanding of their photophysical or self-assembly behavior. The functionalized fullerene material was mainly used so that comparative results could be presented where two units (mono adduct) or twelve units (hexakis adduct) of TBF molecules were attached separately. These comparative studies were beneficial for unambiguous interpretation of results and drawing definitive conclusions regarding the energy transfer with cascade-type systems. Finally, those results were useful for the logical understanding of photo-catalytic experiments using those designer fullerene materials.

Neutralization of solvent vapors of brand 650 by the adsorption‑catalytic method

The purpose of this work is to study the process of neutralization of vapors of a mixed solvent of the brand 650 by the adsorption‑catalytic method. The essence of the method consists in the concentration of solvent components on the sorbent, thermal desorption followed by periodic flameless catalytic oxidation of accumulated organic substances to carbon dioxide and water. Synthetic zeolite of the NaX brand was used as a sorbent, and a porous material based on foam ceramics of the Al2O3/SiO2 composition with a highly developed modified surface with an active catalytic phase was used as a catalyst. The mixed solvent contains, xylenes, ethylcellosol, n‑butanol. It is shown that the value of the sorption volume of zeolite for each class of the considered compounds is influenced by certain factors: the length and structure of the carbon skeleton, the position of the hydroxyl group (for alcohols and esters), the number of methyl groups in the composition of molecules (for the production of benzene). The conversion rate of the mixed solvent components was 65.4–90.1 %.

Selective determination of rhodium and iridium in the urban environment using the catalytic method

The problem of studying the level of technogenic pollution of the environment with platinum group metals is attributed first to the release of platinum metals into the environment together with the exhaust gases of cars using afterburning catalysts containing Pt, Pd, Rh. The pharmaceutical, electronics and jewelry industries the waste of which contains PGMs also contribute to the pollution of the environment. A number of studies have shown the toxic effects of PGM on humans. The goal of the study is to obtain new information about the level of technogenic pollution of the environment with platinum group metals (such as water-washings from roads, bio-collector plants, roadside dust), which necessitates developing of the method for sample preparation and determination of rhodium and iridium. A technique of sample opening and determination of rhodium and iridium in environmental objects, water-washings from roads, bio-collector plants, roadside dust is proposed. To increase the selectivity of rhodium determination, the samples were treated with a mixture of concentrated perchloric acid and sodium periodate when heated to boiling, which provided more than 5-fold increase the rhodium signal. Moreover, the permissible excess of iridium and ruthenium was increased by 5 and 20 times, respectively, due to the conversion of other PGMs into catalytically inactive forms. The indicator reaction of sulfarsazen oxidation by periodate was used in the kinetic determination of rhodium and iridium. The correctness of the results obtained by the developed method was confirmed by the ETAAS method. The determined content of Rh and Ir: in roadside waters (μg/liter) up to 0.015 and 0.005; in collector plants (g/ton) up to 0.030 Rh and 0.022; in street dust (g/ton) up to 0.05 and 0.025, respectively. The standard deviation of the repeatability of the determination results does not exceed 0.07 (Rh) and 0.12 (Ir). The developed method of opening samples and determining rhodium and iridium in environmental objects provided a great bulk of information about the content of rhodium and iridium in water-flushes from Moscow roads, bio-collector plants, roadside dust, which correlate fairly well with the scarce data from other geographic regions available in the literature and our earlier results on rhodium content in dust. The developed technique made it possible to obtain data on the level of technical pollution of the environment with PGMs in places with different traffic density in Moscow.

Reduced Molecular Flavins as Single-Electron Reductants after Photo-Excitation

Flavoenzymes mediate a multitude of chemical reactions and are catalytically active both in different oxidation states and in covalent adducts with reagents. The transfer of such reactivity to the organic laboratory using simplified molecular flavins is highly desirable and such applications in (photo-)oxidation reactions are already established. However, molecular flavins have not been used for the reduction of organic substrates yet, although this activity is known and well-studied for DNA photolyase enzymes. We report a catalytic method using reduced, molecular flavins as photo-reductants and γ-terpinene as sacrificial reductant. Additionally, we present our design for air-stable, reduced flavin catalysts, which is based on a conformational bias strategy and circumvents the otherwise rapid reduction of O2 from air. Using our catalytic strategy, we were able to replace super-stoichiometric amounts of the rare-earth reductant SmI2 in a 5-exo-trig cyclization of substituted barbituric acid derivatives. Such flavin-catalyzed reductions are anticipated to be of broad applicability and their straightforward synthesis indicates future use in stereo- as well as site-selective transformations.

Laponite-Mediated Copper Metallization by Palladium Intercalation

An alternative catalytic method was employed using the reduction of Pd ions on the surface of cetyltrimethylammonium bromide (CTAB) treated laponite to initiate the electroless plating of copper; the deposition features of the Pd nanoparticles produced were investigated in detail. Results indicated intercalation and reduction of Pd nanoparticles occurred at room temperature and involved interaction between the laponite and the cetyltrimethylammonium cationic templates. Organic species and amount on laponite were optimized to adjust silicate platelet interlayer distances and platelet organophilic properties. Intercalation of Pd nanoparticles occurred between the magnesium silicate layers of laponite and this was dependent on pre-treatment and impregnation times. As impregnation is a method of producing heterogeneous catalysts, we considered Pd nanoparticles on laponite templates could catalyze the electroless deposition of Cu to initiate metallization. Cu films fabricated on laponite templates exhibited excellent surface roughness (˜1.7 nm) and low resistivity (˜3.42 μΩ). The devised approach enabled the facile formation of a network suitable for Cu metallization without causing substrate damage and produced metal surfaces with excellent flatness and resistivity.

Chlorine and Chlorinated Compounds Removal from Industrial Wastewater Discharges: A Review

Adsorption techniques for industrial wastewater treatment rich in heavy metals and aqueous solutions of water-soluble such as Cl−, F−, HCO3−, NO3−, SO2−4, and PO3−, often include technologies for toxicity removals. The recent advancement and technical applicability in the treatment of chlorine and chlorinated compounds from industrial wastewater are reviewed in this article. Chlorine and chlorinated compounds are among the common discharged constituents from numerous industries. They can be carcinogenic or naturally toxic and can pose issues to aquatic ecosystems and human beings. Thus, elimination of chlorides and chlorinated compounds from water or wastewater is inevitable to get rid of the problem. Several techniques are being applied for the reduction of chlorine and chlorinated compounds in water. These include biodegradation, photochemical, adsorption, chemical, electrochemical, photo-electrochemical, membrane, supercritical extraction and catalytic method. Chlorine can react with various organic and inorganic micro-pollutants. However, the potential reactivity of chlorine for specific compounds is small, and only minor variations in the structure of the parent compound are anticipated in the water treatment process under typical conditions. This paper reviews different techniques and aspects related to chlorine removal, the types of chlorine species in solution and their catalyst, chlorine fate and transport into the environment, electrochemical techniques for de-chlorination of water, kinetics, mechanisms of reduction of chlorinated compounds, and kinetics of the electrochemical reaction of chlorine compounds. Keywords: Industrial waste, Kinetics, Wastewater, Water purification

Heterogeneous Catalytic Method for the Copper(II)-Catalysed Addition of H-Phosphinates and Secondary Phosphine Oxides to Phenylacetylene

Copper(II) on 4 Å molecular sieve was found to be an efficient heterogeneous catalyst in the addition of different H-phosphinates and secondary phosphine oxides to phenylacetylene. All hydrophosphinylation reactions were completely regioselective, as only β-isomers were formed, and the E-alkenylphosphinates and E-alkenylphosphine oxides were synthesized in moderate to excellent yields. The catalyst could be reused multiple times in the reaction. Graphic Abstract