Hierarchical nickel carbonate hydroxide nanostructures for photocatalytic hydrogen evolution from water splitting.

Metal carbonate hydroxides have emerged as novel and promising candidates for water splitting due to their good electrochemical properties and eco-friendly features. In this study, the hierarchical mesoporous structure of nickel carbonate hydroxide hydrate (Ni2(CO3)(OH)2·4H2O) was synthesized by a one-pot facile hydrothermal method. It demonstrated photocatalytic properties for the first time, exhibiting a hydrogen evolution reaction yield of 10 µmol g-1 h-1 under white light irradiation with a nominal power of 0.495 W. This facile synthesis strategy and the good photocatalytic properties indicate that nickel carbonate hydroxide is a promising material for application in photocatalytic hydrogen evolution.

Shape-Controlled Synthesis of Cu3TeO6 Nanoparticles with Photocatalytic Features.

Cu3TeO6 (CTO) has been synthesized by hydrothermal synthesis applying different pH values without any template or a calcination step to control the crystalline phase and the morphology of nanoparticles. The physicochemical properties characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, N2 adsorption, X-ray photoelectron spectroscopy, and diffuse reflectance ultraviolet-visible (DRUV-vis) spectroscopy techniques revealed that the pH values significantly influence the crystal growth. In acidic media (pH = 2), crystal growth has not been achieved. At pH = 4, the yield is low (10%), and the CTO presents irregular morphology. At pH = 6, the yield increases (up to 71%) obtaining an agglomeration of nanoparticles into spherical morphology. At basic conditions (pH = 8), the yield increases up to 90% and the morphology is the same as the sample obtained at pH = 6. At high basic conditions (pH = 10), the yield is similar (92%), although the morphology changes totally to dispersed nanoparticles. Importantly, the as-prepared CTO semiconductor presents photocatalytic activity for H2 production using triethanolamine as a sacrificial agent under visible light illumination. The results also revealed that the nanoparticles agglomerated in a spherical morphology with larger surface area presented almost double activities in H2 production compared to heterogeneously sized particles. These results highlight the suitable optoelectronic properties, including optical band gap, energy levels, and photoconductivity of CTO semiconductors for their use in photocatalytic H2 production.

Cytotoxic sub-nanometer aqueous platinum clusters as potential antitumoral agents.

Ligand-free sub-nanometer metal clusters (MCs) of Pt, Ir, Rh, Au and Cu, are prepared here in neat water and used as extremely active (nM) antitumoral agents for HeLa and A2870 cells. The preparation just consists of adding the biocompatible polymer ethylene-vinyl alcohol (EVOH) to an aqueous solution of the corresponding metal salt, to give liters of a MC solution after filtration of the polymer. Since the MC solution is composed of just neat metal atoms and water, the intrinsic antitumoral activity of the different sub-nanometer metal clusters can now fairly be evaluated. Pt clusters show an IC50 of 0.48 µM for HeLa and A2870 cancer cells, 23 times higher than that of cisplatin and 1000 times higher than that of Pt NPs, and this extremely high cytotoxicity also occurs for cisplatin-resistant (A2870 cis) cells, with a resistance factor of 1.4 (IC50 = 0.68 µM). Rh and Ir clusters showed an IC50 ∼ 1 µM. Combined experimental and computational studies support an enhanced internalization and cytotoxic activation.

Parts-per-million of ruthenium catalyze the selective chain-walking reaction of terminal alkenes.

The chain-walking of terminal alkenes (also called migration or isomerization reaction) is currently carried out in industry with unselective and relatively costly processes, to give mixtures of alkenes with significant amounts of oligomerized, branched and reduced by-products. Here, it is shown that part-per-million amounts of a variety of commercially available and in-house made ruthenium compounds, supported or not, transform into an extremely active catalyst for the regioselective migration of terminal alkenes to internal positions, with yields and selectivity up to >99% and without any solvent, ligand, additive or protecting atmosphere required, but only heating at temperatures >150 °C. The resulting internal alkene can be prepared in kilogram quantities, ready to be used in nine different organic reactions without any further treatment.

MOF-Stabilized Perfluorinated Palladium Cages Catalyze the Additive-Free Aerobic Oxidation of Aliphatic Alcohols to Acids.

Extremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ-donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine-Pd2+ coordinate cages within the channels of an anionic tridimensional metal-organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF-stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd2+ to dehydrogenate primary alcohols, without any base, and also to activate O2 for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required.

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids.

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1-5 µm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 µm) and catalyzes Brönsted rather than Lewis acid reactions. These results open new avenues not only in the use of ionic liquids as acid catalysts/solvents but also in the preparation of surfactant-free, well-defined ionic liquid microemulsions.

Soluble/MOF-Supported Palladium Single Atoms Catalyze the Ligand-, Additive-, and Solvent-Free Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids.

Metal single-atom catalysts (SACs) promise great rewards in terms of metal atom efficiency. However, the requirement of particular conditions and supports for their synthesis, together with the need of solvents and additives for catalytic implementation, often precludes their use under industrially viable conditions. Here, we show that palladium single atoms are spontaneously formed after dissolving tiny amounts of palladium salts in neat benzyl alcohols, to catalyze their direct aerobic oxidation to benzoic acids without ligands, additives, or solvents. With this result in hand, the gram-scale preparation and stabilization of Pd SACs within the functional channels of a novel methyl-cysteine-based metal-organic framework (MOF) was accomplished, to give a robust and crystalline solid catalyst fully characterized with the help of single-crystal X-ray diffraction (SCXRD). These results illustrate the advantages of metal speciation in ligand-free homogeneous organic reactions and the translation into solid catalysts for potential industrial implementation.

Self-Assembly of Catalytically Active Supramolecular Coordination Compounds within Metal-Organic Frameworks.

Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of PdII SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a PdII-AuIII supramolecular assembly, crystallography underpinned. These SCCs@MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis.

Human amniotic fluid cells are able to produce IL-6 and IL-8.

PROBLEM: In order to investigate the role of amniotic fluid cells (AFC) in the establishment of feto-maternal immune relationship, we evaluated their phenotype and capacity to produce cytokines. METHODS OF STUDY: CK 7-8, human leukocyte antigen (HLA)-I, HLA-DR, HLA-G, CD1d, CD34, CD45, CD14 surface antigens expression and the intracellular production of IL-4, IL-6, IL-8, IL-10, IL-12, interferon-gamma and tumor necrosis factor-1 were studied in cultured AFC and in eight samples immediately after amniocentesis using flow cytometry. IL-6 and IL-8 were detected by ELISA in all amniotic fluids and in all culture supernatants. Moreover, IL-6 and IL-8 mRNA were tested in nine samples. RESULTS: Cultured AFC express HLA-I, HLA-G and CK 7-8 and are able to produce IL-6 and IL-8, confirmed by presence of their mRNA. We quantified IL-6 and IL-8 levels in all amniotic fluids and in all supernatants. CONCLUSION: Surface antigen expression of AFC are not specific of immune cells, but AFC are able to produce cytokines and we can postulate that they may participate in mechanisms involved in normal as well as pathological pregnancy.