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We have covalently connected the ruthenium trisbipyridine complex (bpyRu) as a photoredox module to an iron porphyrin catalyst (porFe) through an amido function for investigating the synergistic action to power the photocatalytic CO2 reduction. The electrochemical studies of the porFe-bpyRu dyad did not show any marked effect on the redox properties of the constitutive units. However, the photophysical properties of the porFe-bpyRu dyad point to the complete extinction of the photoredox module that undergoes ultrafast quenching processes with the porFe acolyte, the unavoidable dilemma in this type of molecular assemblies. Nevertheless, when exogenous bpyRu and a sacrificial electron donor were added to this dyad, we found that it exhibits much higher turnover number and selectivity towards CO2 photocatalytic reduction to CO than with the iron porphyrin analogue (porFe). Comprehensive analyses of the data suggest that this catalytic enhancement displayed by the dyad can be attributed to an interesting electron relay role played by the appended bpyRu moiety.

Conjugates of chlorins with β‐cyclodextrin connected either directly or via a flexible linker were prepared. In aqueous medium these amphiphilic conjugates were photostable, produced singlet oxygen at a rate similar to clinically used temoporfin and formed irregular nanoparticles via aggregation. Successful loading with the chemotherapeutic drug tamoxifen was evidenced in solution by the UV‐Vis spectral changes and dynamic light scattering profiles. Incubation of MCF‐7 cells with the conjugates revealed intense spotted intracellular fluorescence suggestive of accumulation in endosome/lysosome compartments, and no dark toxicity. Incubation with the tamoxifen‐loaded conjugates revealed also practically no dark toxicity. Irradiation of cells incubated with empty conjugates at 640 nm and 4.18 J/cm2 light fluence caused >50 % cell viability reduction. Irradiation following incubation with tamoxifen‐loaded conjugates resulted in even higher toxicity (74 %) indicating that the produced reactive oxygen species had triggered tamoxifen release in a photochemical internalization (PCI) mechanism. The chlorin‐β‐cyclodextrin conjugates displayed less‐lasting effects with time, compared to the corresponding porphyrin‐β‐cyclodextrin conjugates, possibly due to lower tamoxifen loading of their aggregates and/or their less effective lodging in the cell compartments' membranes. The results suggest that further to favorable photophysical properties, other parameters are important for the in vitro effectiveness of the photodynamic systems. [ABSTRACT FROM AUTHOR]

We developed dye-sensitized photocatalytic systems (DSPs) by utilizing porphyrins as a photosensitizer (PS) or as a photosensitizer–catalyst (PS/CAT) upon their chemisorption onto platinum-doped titanium dioxide nanoparticles (Pt-TiO2 NPs). The DSPs coated with Pt-Tc3CP (PS/CAT entity) exhibited a record-high stability (25 500 TONs) and H2 evolution activity (707 mmol g−1 h−1) compared to similar DSPs in the literature. [ABSTRACT FROM AUTHOR]

Solar energy conversion to chemical energy via light-induced H2O splitting to O2 and H2 is considered to be a promising solution to meet the growing global energy demands. To make this transformation economically viable, it is necessary to develop sustainable photocatalytic systems. Herein, we present an efficient photocatalytic H2 production system which relies on components comprised of low-cost and high-abundance elements. In particular, a series of mononuclear complexes [Ni(LNS)3]− and [Ni(N^N)(LNS)2] and a hexanuclear complex [Ni(LNS)2]6 (N^N = diimine and LNS− = heterocyclic thioamidate with different group-substituents) were synthesized and utilized as catalysts, in combination with N-doped carbon dots as photosensitizer, for efficient H2 evolution from aqueous protons. Differences in H2 production efficiency were observed among the studied Ni(II) catalysts, with complexes bearing ligands with stronger electron-donating ability exhibiting higher catalytic activity. A remarkable catalytic efficiency enhancement was observed for the hexanuclear complex, with catalyst loadings lower than those of the mononuclear Ni(II) complexes, affording TONs >1550 (among the highest values reported for photocatalytic systems of similar type operating in H2O). These data provide an indication of catalytic cooperativity between the metal centers of the hexanuclear complex, and demonstrate the crucial role of atomically precise polynuclear Ni(II) catalysts in light-induced H2 production, a result that can guide future catalyst design towards the development of highly efficient, low-cost and environmentally benign photocatalytic systems. [ABSTRACT FROM AUTHOR]

The photocatalytic CO2 reduction into value‐added chemicals is regarded as one promising technology to mitigate environmental issues and the energy crisis of the modern world due to the extended CO2 emissions. Recent advances have shown that iron porphyrins are considered as one of the most efficient molecular catalysts in the activation and reduction of molecules like CO2. Thus, a suitably modified FeIII porphyrin ([FeIII(TF4TMAP)](CF3SO3)5) was prepared and its catalytic activity in terms of photocatalytic reduction of CO2 was studied. This iron catalyst possesses four fluorine substituents in the ortho and the meta position of each meso‐phenyl group of the porphyrin, while trimethylammonium groups were placed in the para position. Photocatalytic studies were performed in the presence of an iridium complex as a chromophore and have shown that [FeIII(TF4TMAP)](CF3SO3)5 can effectively reduce CO2, achieving excellent turnover numbers (up to 5500 TONs) and high turnover frequencies. The main reduction product of this photocatalytic system was CO, and only a small amount of hydrogen was detected, presenting a maximum selectivity of 86 % for CO. [ABSTRACT FROM AUTHOR]

The study presented here is to determine the effect of the froth system on the selectivity of the cassiterite flotation with the sulfosuccinamate Aerosol A 22. This observation was done in order to find out in what way the collecting and frothing properties of the reagent system influence the selection of the mineral particles in the froth product.Simple examination regarding the surface and interfacial tension measurements as well as regarding contact angle and froth formation measurements have been made to specify the mode of action of different froth regulators in an aqueous solution using the sulfosuccinamate Aerosol 22 as collector.The outcome was verified by flotation tests with Bolivian natural cassiterite ores. It was established that the froth regulating reagents of the silicone group an extra quantity of 0.5% 1% in relation to the frothing reagents is enough to improve the selectivity of the cassiterite flotation.

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H2 is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO2 into chemical fuels can reduce the CO2 emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H2 production and CO2 reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application. [ABSTRACT FROM AUTHOR]

The utilization of solar energy via photoelectrochemical cells (PEC) towards hydrogen (H2) production is a promising approach in the field of artificial photosynthesis. In this work, the synthesis and complete characterization of the first covalently linked porphyrin‐cobalt diimine‐dioxime dyad (ZnP‐Co) is reported. The synthetic procedure that was followed is based on simple and high yielding reactions, without using any noble metal. Photophysical investigation of the dyad revealed sufficient electronic communication between the sensitizer and the catalyst in the excited state. Finally, NiO films were sensitized with ZnP‐Co and the H2‐evolving photoelectrochemical activity of the resulting photocathode was assessed. The modest performances could be rationalized thanks to photolysis and post‐operando characterizations of the system, thus providing some guidelines toward the design of more efficient porphyrin‐based assemblies. [ABSTRACT FROM AUTHOR]