Porosity through reduction in metal oxides

Routes to porous materials with nanoscale dimensions have been investigated. In the first example presented, porous manganese oxide has been prepared by leaching Ni metal from a nickel-manganese oxide precursor via reduction. Electron microscopy studies have revealed the presence of Ni nanoparticles on the surface, and also embedded within the porous MnO matrix. Magnetic measurements have shown exchange bias between the ferromagnetic Ni nanoparticles and the antiferromagnetic MnO phase. In the second system studied, porous nanostructures of rutile VO2 and corundum V2O3 have been prepared by reduction of amine-templated V2O5-δ nanoscrolls. The porosity of these materials has been probed by electron microscopy, N2 sorption measurements and thermogravimetric analysis

New two in one magnetic fluorescent nanocomposites

Magnetite nanoparticles have been coated by a porphyrin derivative to produce new magnetic materials with fluorescent properties. The magnetic nanoparticles were prepared using two different methods, one based on sol-gel techniques and ultrasonic processing, and the other via a controlled chemical co-precipitation. Different types of porphyrin functionalised magnetic nanoparticles have been prepared and have been characterised by electron microscopy (TEM and SEM), XRD, FTIR, Raman, UV-vis, and fluorescence spectroscopy. Microscopy results showed the formation of core-shell nanostructures, with IR and photoluminescence spectroscopy results confirming the presence of porphyrin in the shell

Preparation and biological investigation of luminescent water soluble CdTe nanoparticles

In this study CdTe quantum dots have been successfully prepared in aqueous medium using several different thiol stabilizers. The resulting nanocrystals were purified and the photoluminescence efficiency was subsequently enhanced through post preparative procedures such as photochemical etching and ageing. An optical study was carried out on the resulting CdTe nanocrystals as proof as their improvement. Preliminary tests of the thiol stabilised QDs as potential biolabels have been performed. It has been shown that L-cysteine stabilised QDs localising to the outer cell membrane in living cells. TGA stabilised CdTe QDs can potentially serve as live cell imaging tools as they exhibit strong luminescence and excellent photostability. In addition, the ability of TGA stabilised CdTe QDs to traverse the cell membrane of macrophages is a formidable quality that may potentially be harnessed for imaging and therapeutics. Modulating the delivery of QDs to subcellular locations in living cells opens a myriad of potential applications ranging from drug delivery to examination of intracellular processes

Exploiting cation aggregation in new magnesium amidohaloaluminate electrolytes for magnesium batteries

Mg batteries present an attractive and sustainable alternative to Li-ion batteries, wherein magnesium metal as an anode displays a superior theoretical volumetric energy density of 3833 A h L−1versus 2062 A h L−1 for lithium. An outstanding crucial bottleneck in realising their more widespread uptake is the development of suitable electrolytes, where electrode passivation, a limited electrochemical window, conditioning requirements, low ion mobility and low coulombic efficiencies all contribute to current limitations in Mg batteries. In an area thus far dominated by the thermodynamically stable [Mg2Cl3]+ dinuclear cation, we present here a novel family of magnesium amidohaloaluminate electrolytes [(Dipp)(SiMe3)2NAlCl3]− [MgxCl2x−1]+ where the magnesium chloride cation aggregation has been tailored (x = 1, 2, 3) by substitution of the coordinating ligand to the Mg2+ centre, and show how directly altering this cation affects battery performance (Dipp = 2,6-diisopropylphenyl, Me = methyl). The electrochemical activity of these new electrolytes has been evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy in Mg–metal symmetrical cells as well as in battery cells with the Mo6S8 Chevrel phase cathode material against magnesium metal. The mononuclear and dinuclear magnesium amidohaloaluminate electrolytes facilitate reversible Mg plating and stripping from the Mg–metal anode with excellent stability, withstanding over 70 hours of continuous cycling. We demonstrate the compatibility of these novel electrolytes with the Mo6S8 Chevrel intercalation cathode material, allowing cycling of a Mg–metal cell up to 100 cycles with coulombic efficiencies above 95%

Insulating to metallic behaviour in the cation ordered perovskites Ba 2 Nd 1−x Fe x MoO 6

The series of cation ordered double perovskites Ba2Nd1−xFexMoO6 undergo a compositionally-driven transition from localised to delocalised electronic behaviour, as exhibited in the end members Ba2NdMoO6 and Ba2FeMoO6 respectively. Rietveld structural analyses against neutron diffraction data indicate that all compounds are stoichiometric in oxygen and show replacement of Nd3+ with Fe3+ on the larger of the two octahedral sites in the cation-ordered structure. A tetragonal distortion persists up to x = 0.25 and Ba2Nd0.9Fe0.1MoO6 shows freezing of magnetic moments at 5 K. Neutron scattering indicates an absence of long range magnetic ordering suggesting the formation of a spin glass phase below this temperature. Ba2Nd0.75Fe0.25MoO6 shows high electrical resistivity with a temperature dependence indicative of fully localised electronic behaviour. Despite the Fe3+ occupation (0.25) being above the percolation limit (0.195) for the face centred cubic lattice, this compound shows no magnetic ordering at 2 K. Compositions in the range 0.30 ≤ x ≤ 0.85 give a mixture of two perovskite phases with lattice parameters of ca. 8.4 and 8.1 Å. The single phase compositions Ba2Nd0.10Fe0.90MoO6 and Ba2Nd0.05Fe0.95MoO6 form face centred cubic structures with long range magnetic ordering of the Fe3+ moments below ferrimagnetic ordering transitions of 270 and 285 K respectively. Neutron diffraction shows almost complete parallel alignment of the Fe3+ moments and, combined with conductivity measurements showing delocalised electronic behaviour in Ba2Nd0.10Fe0.90MoO6, indicate ferrimagnetic ordering of Fe3+ and delocalised Mo5+

Enhancement of the lithium ion conductivity of Ta-doped Li7La3Zr2O12 by incorporation of calcium

Fast ion conducting garnet materials have been identified as promising electrolytes for all solid-state batteries. However, reliable synthetic routes to materials with fully elucidated cation site occupancies where an enhancement in lithium conductivity is observed remains a challenge. Ca-Incorporation is developed here as a promising approach to enhance the ionic conductivity of garnet-type Li7-xLa3Zr2-xTaxO12phases. Here we present a new sol-gel synthetic strategy as a facile route to the preparation of materials of a desired stoichiometry optimized for Li+conductivity. We have found that the ionic conductivity of Li6.4La3Zr1.4Ta0.6O12is increased by a factor of four by the addition of 0.2 mol of Ca per formula unit. Ca is incorporated in the garnet lattice where it has no effect on the sinterability of the material and is predominately located at the La sites. We anticipate that the ease of our synthetic route and the phases presented here represents a starting point for the further realization of solid state electrolyte compositions with similarly high Li+conductivities using this methodology

Selective and facile synthesis of sodium sulfide and sodium disulfide polymorphs

Na2S and Na2S2 were selectively synthesized using a microwave-assisted thermal treatment of a Na+/S solution in tetraglyme between 100 and 200 °C, considerably lower than that of current routes. This novel synthetic pathway yields the Na2S phase in high purity and allows for good selectivity between the polymorphs of Na2S2 (α and β phases). These materials show promising electrochemical properties and are particularly interesting for the continued development of Na–S batteries

Na1.5La1.5TeO6:Na+ conduction in a novel Na-rich double perovskite

Increasing demand for lithium batteries for automotive applications, coupled with the necessity to move to large-scale energy storage systems, is driving a push towards new technologies and has seen Na-ion batteries emerge as a leading alternative to Li-ion. Amongst these, all solid-state configurations represent a promising route to achieving higher energy densities and increased safety. Remaining challenges include the need for Na+ solid electrolytes with the requisite ionic conductivities crucial for use in a solid-state cell. Here, we present the novel Na-rich double perovskite, Na1.5La1.5TeO6. The transport properties, explored at the macroscopic and local level, reveal a low activation energy barrier for Na+ diffusion and great promise for use as an electrolyte for all solid-state Na-batteries