Lanthanide-doped luminescent ionogels

Ionogels are solid oxide host networks con. ning at a meso-scale ionic liquids, and retaining their liquid nature. Ionogels were obtained by dissolving lanthanide(III) complexes in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [C(6)mim][Tf2N], followed by confinement of the lanthanide-doped ionic liquid mixtures in the pores of a nano-porous silica network. [C(6)mim][Ln(tta)(4)], where tta is 2-thenoyltrifluoroacetonate and Ln = Nd, Sm, Eu, Ho, Er, Yb, and [choline](3)[Tb(dpa)(3)], where dpa = pyridine-2,6-dicarboxylate (dipicolinate), were chosen as the lanthanide complexes. The ionogels are luminescent, ion-conductive inorganic-organic hybrid materials. Depending on the lanthanide(III) ion, emission in the visible or the near-infrared regions of the electromagnetic spectrum was observed. The work presented herein highlights that the confinement did not disturb the first coordination sphere of the lanthanide ions and also showed the excellent luminescence performance of the lanthanide tetrakis beta-diketonate complexes. The crystal structures of the complexes [C(6)mim][Yb(tta)(4)] and [choline](3)[Tb(dpa)(3)] are reported.

Rare-earth complexes of ferrocene-containing ligands: Visible-light excitable luminescent materials

The ferrocene-derivatives bis(ferrocenyl-ethynyl)-1,10-phenanthroline (Fc(2)phen) and ferrocenoyltrifluoroacetone (Hfta) have been used to synthesize ferrocene-containing rare-earth beta-diketonate complexes. The complexes [Ln(tta)(3)(Fc(2)phen)] and [Ln(fta)(3)(phen)] (where Ln = La, Nd, Eu, Yb) show structural similarities to the tris(2-thenoyltrifluoroacetonate)(1,10-phenanthroline)lanthanide(III) complexes, [Ln(tta)(3)(phen)]. The coordination number of the lanthanide ion is 8, and the coordination sphere can be described as a distorted dodecahedron. However, the presence of the ferrocene moieties shifts the ligand absorption bands of the rare-earth complexes to longer wavelengths so that the complexes can be excited not only by ultraviolet radiation but also by visible light of wavelengths up to 420 nm. Red photoluminescence is observed for the europium(III) complexes and near-infrared photoluminescence for the neodymium(III) and ytterbium(III) complexes. The presence of the ferrocene groups makes the rare-earth complexes hydrophobic and well-soluble in apolar organic solvents.

Rare-earth quinolinates: Infrared-emitting molecular materials with a rich structural chemistry

Near-infrared-emitting rare-earth chelates based on 8-hydroxyquinoline have appeared frequently in recent literature, because they are promising candidates for active components in near-infrared-luminescent optical devices, such as optical amplifiers, organic light-emitting diodes, .... Unfortunately, the absence of a full structural investigation of these rare-earth quinolinates is hampering the further development of rare-earth quinolinate based materials, because the luminescence output cannot be related to the structural properties. After an elaborate structural elucidation of the rare-earth quinolinate chemistry we can conclude that basically three types of structures can be formed, depending on the reaction conditions: tris complexes, corresponding to a 1:3 metal-to-ligand ratio, tetrakis complexes, corresponding to a 1:4 metal-to-ligand ratio, and trimeric complexes, with a 3:8 metal-to-ligand ratio. The intensity of the emitted near-infrared luminescence of the erbium(Ill) complexes is highest for the tetrakis complexes of the dihalogenated 8-hydroxyquinolinates.

High Reactivity of Metal-Organic Frameworks under Grinding Conditions: Parallels with Organic Molecular Materials

Interconversion made easy: Metal–organic frameworks (MOFs) are surprisingly reactive under grinding conditions and can perform various rearrangements (see picture). In this respect, the results reveal clear parallels between MOFs and organic molecular materials.

Arsenic and selenium mobilisation from organic matter treated mine spoil with and without inorganic fertilisation

Organic matter amendments are applied to contaminated soil to provide a better habitat for revegetation and remediation, and olive mill waste compost (OMWC) has been described as a promising material for this aim. We report here the results of an incubation experiment carried out in flooded conditions to study its influence in As and metal solubility in a trace elements contaminated soil. NPK fertilisation and especially organic amendment application resulted in increased As, Se and Cu concentrations in pore water. Independent of the amendment, dimethylarsenic acid (DMA) was the most abundant As species in solution. The application of OMWC increased pore water dissolved organic-carbon (DOC) concentrations, which may explain the observed mobilisation of As, Cu and Se; phosphate added in NPK could also be in part responsible of the mobilisation caused in As. Therefore, the application of soil amendments in mine soils may be particularly problematic in flooded systems. (C) 2012 Elsevier Ltd. All rights reserved.

Towards Organic Electronic Materials for Electrically Stimulated Gene Delivery

The cell-specific delivery of polynucleic acids (e.g., DNA, RNA), gene therapy, has the potential to treat various diseases. In this chapter we discuss the use of organic electronic materials as non-viral gene delivery vectors and the great potential for electrochemically triggered gene delivery. We highlight some examples in this chapter based on fullerenes (bucky balls and carbon nanotubes), graphenes and electroactive polymers, particularly those that include experiments in vivo.

Improving fuel economy application of the organic Rankine Cycle on a hybrid bus

Globally vehicle operators are experiencing rising fuel costs and increased
running expenses as governments around the world attempt to decrease carbon dioxide emissions and fossil fuel consumption, due to global warming and the drive to reduce dependency on fossil fuels. Recent advances in hybrid vehicle design have made great strides towards more efficient operation, with regenerative braking being widely used to capture otherwise lost energy. In this paper a hybrid series bus is developed a step further, by installing another method of energy capture on the vehicle. In this case, it is in the form of the Organic Rankine Cycle (ORC). The waste heat expelled to the exhaust and coolant streams is recovered and converted to electrical energy which is then stored in the hybrid vehicles batteries. The electrical energy can then be used for the auxiliary power circuit or to assist in vehicle propulsion, thus reducing the load on the engine, thereby improving the overall fuel economy of the vehicle and reducing carbon dioxide emissions.

An in situ ionic-liquid-assisted synthetic approach to iron fluoride/graphene hybrid nanostructures as superior cathode materials for lithium ion batteries

A tactful ionic-liquid (IL)-assisted approach to in situ synthesis of iron fluoride/graphene nanosheet (GNS) hybrid nanostructures is developed. To ensure uniform dispersion and tight anchoring of the iron fluoride on graphene, we employ an IL which serves not only as a green fluoride source for the crystallization of iron fluoride nanoparticles but also as a dispersant of GNSs. Owing to the electron transfer highways created between the nanoparticles and the GNSs, the iron fluoride/GNS hybrid cathodes exhibit a remarkable improvement in both capacity and rate performance (230 mAh g^-1 at 0.1 C and 74 mAh g^-1 at 40 C). The stable adhesion of iron fluoride nanoparticles on GNSs also introduces a significant improvement in long-term cyclic performance (115 mAh g^-1 after 250 cycles even at 10 C). The superior electrochemical performance of these iron fluoride/GNS hybrids as lithium ion battery cathodes is ascribed to the robust structure of the hybrid and the synergies between iron fluoride nanoparticles and graphene. © 2013 American Chemical Society.

Fibre laser joining of highly dissimilar materials: Commercially pure Ti and PET hybrid joint for medical device applications

Laser transmission joining (LTJ) is growing in importance, and has the potential to become a niche technique for the fabrication of hybrid plastic-metal joints for medical device applications. The possibility of directly joining plastics to metals by LTJ has been demonstrated by a number of recent studies. However, a reliable and quantitative method for defining the contact area between the plastic and metal, facilitating calculation of the mechanical shear stress of the hybrid joints, is still lacking. A new method, based on image analysis using ImageJ, is proposed here to quantify the contact area at the joint interface. The effect of discolouration on the mechanical performance of the hybrid joints is also reported for the first time. Biocompatible polyethylene terephthalate (PET) and commercially pure titanium (Ti) were selected as materials for laser joining using a 200 W CW fibre laser system. The effect of laser power, scanning speed and stand-off distance between the nozzle tip and top surface of the plastic were studied and analysed by Taguchi L9 orthogonal array and ANOVA respectively. The surface morphology, structure and elemental composition on the PET and Ti surfaces after shearing/peeling apart were characterized by SEM, EDX, XRD and XPS.

New end-use application for GFRP recyclates as reinforcement for concrete-polymer materials’

Glass fibre-reinforced plastics (GFRP), nowadays commonly used in the construction, transportation and automobile sectors, have been considered inherently difficult to recycle due to both: cross-linked nature of thermoset resins, which cannot be remolded, and complex composition of the composite itself, which includes glass fibres, matrix and different types of inorganic fillers. Presently, most of the GFRP waste is landfilled leading to negative environmental impacts and supplementary added costs. With an increasing awareness of environmental matters and the subsequent desire to save resources, recycling would convert an expensive waste disposal into a profitable reusable material. There are several methods to recycle GFR thermostable materials: (a) incineration, with partial energy recovery due to the heat generated during organic part combustion; (b) thermal and/or chemical recycling, such as solvolysis, pyrolisis and similar thermal decomposition processes, with glass fibre recovering; and (c) mechanical recycling or size reduction, in which the material is subjected to a milling process in order to obtain a specific grain size that makes the material suitable as reinforcement in new formulations. This last method has important advantages over the previous ones: there is no atmospheric pollution by gas emission, a much simpler equipment is required as compared with ovens necessary for thermal recycling processes, and does not require the use of chemical solvents with subsequent environmental impacts. In this study the effect of incorporation of recycled GFRP waste materials, obtained by means of milling processes, on mechanical behavior of polyester polymer mortars was assessed. For this purpose, different contents of recycled GFRP waste materials, with distinct size gradings, were incorporated into polyester polymer mortars as sand aggregates and filler replacements. The effect of GFRP waste treatment with silane coupling agent was also assessed. Design of experiments and data treatment were accomplish by means of factorial design and analysis of variance ANOVA. The use of factorial experiment design, instead of the one-factor-at-a-time method is efficient at allowing the evaluation of the effects and possible interactions of the different material factors involved. Experimental results were promising toward the recyclability of GFRP waste materials as aggregates and filler replacements for polymer mortar, with significant gain of mechanical properties with regard to non-modified polymer mortars.

Single-Molecule Magnets and Multifunctional Molecular Magnetic Materials Based on Polynuclear Metal Complexes

Our work on single molecule magnets and multifunctional magnetic materials is presented in four projects. In the first project we show for first time that heteroatomic-type pseudohalides, such as OCN-, can be employed as structure-directing ligands and ferromagnetic couplers in higher oxidation state metal cluster chemistry. The initial use of cyanato groups in Mn cluster chemistry has afforded structurally interesting MnII/III14 (1) and MnII/III/IV16 (2) clusters in which the end-on bridging cyanates show a preference in binding through their O-atom. The Mn14 compound shows entirely visible out-of-phase alternating currect signals below 5 K and large hysteresis loops below 2 K. Furthermore, the amalgamation of azido groups with the triethanolamine tripodal ligand in manganese carboxylate cluster chemistry has led to the isolation of a new ferromagnetic, high-nuclearity and mixed-valence MnII/III15Na2 (3) cluster with a large ground-state spin value of S = 14. In the second project we demonstrate a new synthetic route to purely inorganic-bridged, transition metal-azido clusters [CoII7 (4) and NiII7 (5)] and coordination polymers [{FeII/III2}n (6)] which exhibit strong ferromagnetic, SMM and long-range magnetic ordering behaviors. We also show that access to such a unique ferromagnetic class of inorganic, N-rich and O-free materials is feasible through the use of Me3SiN3 as the azido-ligand precursor without requiring the addition of any organic chelating/bridging ligand. In the last projects we have tried to bring together molecular magnetism and optics via the synthesis of multifunctional magnetic materials based on 3d- or 4f-metal ions. We decided to approach such challenge from two different directions: firstly, in our third project, by the deliberate replacement of non-emissive carboxylato ligands in known 3d-SMMs with their fluorescent analogues, without perturbing the metal-core structure and SMM properties (complexes 7, 8, and 9). The second route (last project) involves the use of naphthalene or pyridine-based polyalcohol bridging ligands for the synthesis of new polynuclear LnIII metal clusters (Ln = lanthanide) with novel topologies, SMM behaviors and luminescent properties arising from the increased efficiency of the “antenna” organic group. This approach has led us to the isolation of two new families of LnIII8 (complexes 10-13) and LnIII4 (complexes 14-20) clusters.

High-Spin and Emissive Molecular Materials: Synthesis and Characterization of New Polynuclear Ni(II) Complexes from the Use of Aromatic Schiff Bases as Bridging Ligands

The employment of the bridging/chelating Schiff bases, N-salicylidene-4-methyl-o-aminophenol (samphH2) and N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in nickel cluster chemistry has afforded eight polynuclear Ni(II) complexes with new structural motifs, interesting magnetic and optical properties, and unexpected organic ligand transformations. In the present thesis, Chapter 1 deals with all the fundamental aspects of polynuclear metal complexes, molecular magnetism and optics, while research results are reported in Chapters 2 and 3. In the first project (Chapter 2), I investigated the coordination chemistry of the organic chelating/bridging ligand, N-salicylidene-4-methyl-o-aminophenol (samphH2). The general NiII/tBuCO2-/samphH2 reaction system afforded two new tetranuclear NiII clusters, namely [Ni4(samph)4(EtOH)4] (1) and [Ni4(samph)4(DMF)2] (2), with different structural motifs. Complex 1 possessed a cubane core while in complex 2 the four NiII ions were located at the four vertices of a defective dicubane. The nature of the organic solvent was found to be of pivotal importance, leading to compounds with the same nuclearity, but different structural topologies and magnetic properties. The second project, the results of which are summarized in Chapter 3, included the systematic study of a new optically-active Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in NiII cluster chemistry. Various reactions between NiX2 (X- = inorganic anions) and nacbH2 were performed under basic conditions to yield six new polynuclear NiII complexes, namely (NHEt3)[Ni12(nacb)12(H2O)4](ClO4) (3), (NHEt3)2[Ni5(nacb)4(L)(LH)2(MeOH)] (4), [Ni5(OH)2(nacb)4(DMF)4] (5), [Ni5(OMe)Cl(nacb)4(MeOH)3(MeCN)] (6), (NHEt3)2[Ni6(OH)2(nacb)6(H2O)4] (7), and [Ni6(nacb)6(H2O)3(MeOH)6] (8). The nature of the solvent, the inorganic anion, X-, and the organic base were all found to be of critical importance, leading to products with different structural topologies and nuclearities (i.e., {Ni5}, {Ni6} and {Ni12}). Magnetic studies on all synthesized complexes revealed an overall ferromagnetic behavior for complexes 4 and 8, with the remaining complexes being dominated by antiferromagnetic exchange interactions. In order to assess the optical efficiency of the organic ligand when bound to the metal centers, photoluminescence studies were performed on all synthesized compounds. Complexes 4 and 5 show strong emission in the visible region of the electromagnetic spectrum. Finally, the ligand nacbH2 allowed for some unexpected organic transformations to occur; for instance, the pentanuclear compound 5 comprises both nacb2- groups and a new organic chelate, namely the anion of 5-chloro-2-[(3-hydroxy-4-oxo-1,4-dihydronaphthalen-1-yl)amino]benzoic acid. In the last section of this thesis, an attempt to compare the NiII cluster chemistry of the N-naphthalidene-2-amino-5-chlorobenzoic acid ligand with that of the structurally similar but less bulky, N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2), was made.