Magnetic Phase Transitions in a Ni4 O4 -Cubane-Based Metal-Organic Framework.

An unprecedented spin cluster-based network architecture {[NiII 2 (pdaa)(OH)2 (H2 O)]n (H2 pdaa=1,4-phenylene diacetic acid)}, comprising 1D linear chains of NiII ions crosslinked via Ni4 O4 cubanes, forms under hydrothermal conditions; this 3D coordination network exhibits magnetic ordering at 23.9 K as well as a second magnetic ordering process at 2.8 K likely associated with a structural phase transition.

Nanoparticles for Bioapplications: Study of the Cytotoxicity of Water Dispersible CdSe(S) and CdSe(S)/ZnO Quantum Dots.

Semiconductor nanocrystals or quantum dots (QDs) have unique optical and physical properties that make them potential imaging tools in biological and medical applications. However, concerns over the aqueous dispersivity, toxicity to cells, and stability in biological environments may limit the use of QDs in such applications. Here, we report an investigation into the cytotoxicity of aqueously dispersed CdSe(S) and CdSe(S)/ZnO core/shell QDs in the presence of human colorectal carcinoma cells (HCT-116) and a human skin fibroblast cell line (WS1). The cytotoxicity of the precursor solutions used in the synthesis of the CdSe(S) QDs was also determined in the presence of HCT-116 cells. CdSe(S) QDs were found to have a low toxicity at concentrations up to 100 µg/mL, with a decreased cell viability at higher concentrations, indicating a highly dose-dependent response. Meanwhile, CdSe(S)/ZnO core/shell QDs exhibited lower toxicity than uncoated QDs at higher concentrations. Confocal microscopy images of HCT-116 cells after incubation with CdSe(S) and CdSe(S)/ZnO QDs showed that the cells were stable in aqueous concentrations of 100 µg of QDs per mL, with no sign of cell necrosis, confirming the cytotoxicity data.

La2O3 Promoted Pd/rGO Electro-catalysts for Formic Acid Oxidation.

High activity, a low rate of CO poisoning, and long-term stability of Pd electro-catalysts are necessary for practical use as an anode material in direct formic acid fuel cells. Achieving a high degree of Pd nanoparticle dispersion on a carbon support, without agglomeration, while maintaining a facile electron transfer through the catalyst surface are two challenging tasks to be overcome in fulfilling this aim. Herein, we report the effect of addition of La/La-oxides on the efficiency of Pd nanoparticles supported on reduced graphene oxide (rGO) for formic acid electro-oxidation reaction. A series of electro-catalysts with different Pd-La molar ratios were successfully synthesized and characterized using a range of techniques including PXRD, XPS, TEM, FTIR, and Raman spectroscopy and then tested as anode materials for direct formic acid fuel cells. We explore that the lanthanum species (La/La-oxide) significantly promote the activity and stability of Pd catalyst toward electrocatalytic oxidation of formic acid. The metallic ratio is found to be critical, and the activity order of various catalysts is observed as follows; Pd30La70/rGO > Pd80La20/rGO > Pd70La30 rGO. The obtained mass specific activity for Pd30La70/rGO (986.42 A/g) is 2.18 times higher than that for Pd/rGO (451 A/g) and 16 times higher than that for Pd/C (61.5 A/g) at given onset peak potentials. The high activity and stability of the electro-catalysts are attributed to the uniform dispersion of Pd nanoparticles over the rGO support, as evidenced from TEM images. It is believed that the role of La species in promoting the catalyst activity is to disperse the catalyst particles during synthesis and to facilitate the electron transfer via providing a suitable pathway during electrochemical testing.

Hydrothermal synthesis of highly luminescent blue-emitting ZnSe(S) quantum dots exhibiting low toxicity.

Highly luminescent quantum dots (QDs) that emit in the visible spectrum are of interest to a number of imaging technologies, not least that of biological samples. One issue that hinders the application of luminescent markers in biology is the potential toxicity of the fluorophore. Here we show that hydrothermally synthesized ZnSe(S) QDs have low cytotoxicity to both human colorectal carcinoma cells (HCT-116) and human skin fibroblast cells (WS1). The QDs exhibited a high degree of crystallinity, with a strong blue photoluminescence at up to 29% quantum yield relative to 4',6-diamidino-2-phenylindole (DAPI) without post-synthetic UV-irradiation. Confocal microscopy images obtained of HCT-116 cells after incubation with the QDs highlighted the stability of the particles in cell media. Cytotoxicity studies showed that both HCT-116 and WS1 cells retain 100% viability after treatment with the QDs at concentrations up to 0.5g/L, which makes them of potential use in biological imaging applications.

A flexible copper based microporous metal-organic framework displaying selective adsorption of hydrogen over nitrogen.

A microporous metal-organic framework [Cu(3)(ipO)(2)(pyz)(2)](n), (ipO = 2-hydroxyisophthalic acid, pyz = pyrazine) was synthesized via an in situ. ligand transformation reaction. The microporous framework displays helical arrays of ipo ligands holding the Cu atoms in 2D sheets, whilst the coordination of pyz molecules acts to arrange these sheets into a microporous 3D structure. Remarkable selective sorption behaviour (>5) for H(2) over N(2) is observed and explained with molecular dynamics simulations.

Four new coordination polymers constructed from benzene tricarboxylic acid: synthesis, crystal structure, thermal and magnetic properties.

The use of 1,3,5-benzene tricarboxylic acid (H(3)btc) as an organic linker has allowed us to achieve the rational design of two pairs of isostructural coordination polymers having molecular formulae [M(2)(btc)(F)](n) (M(ii) = Mn (1), Co (2)) and [M(3)(btc)(Hbtc)(OH)(H(2)O)(11)](n) (M(ii) = Fe (3), Co (4)) where btc and Hbtc represent the fully and doubly de-protonated tricarboxylates respectively. These compounds were synthesized using hydrothermal methods and characterized by thermal analysis and variable temperature magnetic measurements. The X-ray analysis reveals that compounds 1 and 2 crystallize in the monoclinic space group C2/c while compounds 3 and 4 crystallize in the monoclinic space group C2. Compounds 1 and 2 feature fluoride bridged 1D metal chains linked together via carboxylate groups of btc, whilst compounds 3 and 4 consist of 1D zigzag chains having strong hydrogen bonds with neighbouring chains. Variable temperature magnetic measurements show an overall antiferromagnetic behaviour for compounds 1, 2 and 4, with no indication of magnetic ordering phenomena in the temperature range from 300-2 K. As 3 and 4 are isostructural, we assume that the magnetic properties are similar.

A 2D cobalt based coordination polymer constructed from benzimidazole and acetate ion exhibiting spin-canted antiferromagnetism.

A coordination polymer, [Co(II)(bIM)(acetate)] (bIM = benzimidazole) was synthesized using a solvothermal method; the complex has a two dimensional non-interpenetrated network structure and exhibits a spin-canted antiferromagnetic behaviour at low temperature and a high coercive field.