Luminescence tuning of MOFs via ligand to metal and metal to metal energy transfer by co-doping of 2∞[Gd2Cl6(bipy)3]*2bipy with europium and terbium

The series of anhydrous lanthanide chlorides LnCl3, Ln=Pr–Tb, and 4,4'-bipyridine (bipy) constitute isotypic MOFs of the formula 2∞[Ln2Cl6(bipy)3]*2bipy. The europium and terbium containing compounds both exhibit luminescence of the referring trivalent lanthanide ions, giving a red luminescence for Eu3+ and a green luminescence for Tb3+ triggered by an efficient antenna effect of the 4,4'-bipyridine linkers. Mixing of different lanthanides in one MOF structure was undertaken to investigate the potential of this MOF system for colour tuning of the luminescence. Based on the gadolinium containing compound, co-doping with different amounts of europium and terbium proves successful and yields solid solutions of the formula 2∞[Gd2-x-yEuxTbyCl6(bipy)3]*2bipy (1–8), 0≤x, y≤0.5. The series of MOFs exhibits the opportunity of tuning the emission colour in-between green and red. Depending on the atomic ratio Gd:Eu:Tb, the yellow region was covered for the first time for an oxygen/carboxylate-free MOF system. In addition to a ligand to metal energy transfer (LMET) from the lowest ligand-centered triplet state of 4,4'-bipyridine, a metal to metal energy transfer (MMET) between 4f-levels from Tb3+ to Eu3+ is as well vital for the emission colour. However, no involvement of Gd3+ in energy transfers is observed rendering it a suitable host lattice ion and connectivity centre for diluting the other two rare earth ions in the solid state. The materials retain their luminescence during activation of the MOFs for microporosity

Molecularly imprinted conductive polymers for controlled trafficking of neurotransmitters at solid–liquid interfaces

We realize a molecularly imprinted polymer (MIP) which is imprinted with the retinal neurotransmitter glutamate. The films prepared by electrochemical deposition have a smooth surface with a granular morphology as observed using an atomic force microscope. Multiple reflection attenuated total reflection infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used to chemically confirm the imprint of a neurotransmitter in the MIP at the solid–liquid and the solid–air interface, respectively. Fluorescence spectroscopy using the dye fluorescamine is used to monitor the changes in neurotransmitter concentration in various solvents induced by application of voltage to the MIP. By controlling neurotransmitter trafficking across a solid–liquid interface with voltage, we suggest the possibility of using such a neurotransmitter imprinted MIP for chemical stimulation of retinal neurons. The current state of the art approach to restore sight in certain cases of blindness is the replacement of damaged photoreceptors by a subretinal implant consisting of light-sensitive photodiodes. Thus a future perspective of our work would be to chemically stimulate the neurons by replacing the photodiodes in the subretinal implant by the neurotransmitter imprinted polymer film

Solvent content in thin spin-coated polystyrene homopolymer films

The solvent content of thin polystyrene (PS) films, spin-coated from protonated and deuterated toluene onto silicon substrates, is investigated. Neutron reflectometry (NR) is used to probe the total remaining solvent inside the PS films in a nondestructive and noninvasive way. In freshly prepared films, the investigated parameters are the molecular weight of PS and the total film thickness. Moreover, the effect of postproduction treatment by annealing at temperatures below and above the glass transition of PS as well as long-term storage over 2 years are examined to deduce the reduction of the remaining solvent. The remaining solvent content increases with increasing molecular weight and with increasing film thickness. An enrichment of toluene at the Si/polymer interface is found. Under the different annealing and storage conditions tested, the remaining solvent is not totally removed. The observed behavior is discussed in the framework of polymer thin films and compared with results obtained by alternative experimental approaches

Metal-Organic Framework MIL-68(In)-NH2_{2} on the Membrane Test Bench for Dye Removal and Carbon Capture

The metal-organic framework (MOF) MIL-68(In)-NH$_{2}$ was tested for dye removal from wastewater and carbon capture gas separation. MIL-68(In)-NH$_{2}$ was synthesized as a neat, supported MOF thin film membrane and as spherical particles using pyridine as a modulator to shape the morphology. The neat MIL-68(In)-NH$_{2}$ membranes were employed for dye removal in cross-flow geometry, demonstrating strong molecular sieving. MIL-68(In)-NH$_{2}$ particles were used for electrospinning of poylethersulfone mixed-matrix membranes, applied in dead-end filtration with unprecedented adsorption values. Additionally, the neat MOF membranes were used for H$_{2}$/CO$_{2}$ and CO$_{2}$/CH$_{4}$ separation

Metamorphosis of Heterostructured Surface-Mounted Metal–Organic Frameworks Yielding Record Oxygen Evolution Mass Activities

Materials derived from surface-mounted metal–organic frameworks (SURMOFs) are promising electrocatalysts for the oxygen evolution reaction (OER). A series of mixed-metal, heterostructured SURMOFs is fabricated by the facile layer-by-layer deposition method. The obtained materials reveal record-high electrocatalyst mass activities of ≈2.90 kA g$^{-1}$ at an overpotential of 300 mV in 0.1 m KOH, superior to the benchmarking precious and nonprecious metal electrocatalysts. This property is assigned to the particular in situ self-reconstruction and self-activation of the SURMOFs during the immersion and the electrochemical treatment in alkaline aqueous electrolytes, which allows for the generation of NiFe (oxy)hydroxide electrocatalyst materials of specific morphology and microstructure

Metamagnetism and critical fluctuations in high quality single crystals of the bilayer ruthenate Sr3Ru2O7

We report the results of low temperature transport, specific heat and magnetisation measurements on high quality single crystals of the bilayer perovskite Sr3Ru2O7, which is a close relative of the unconventional superconductor Sr2RuO4. Metamagnetism is observed, and transport and thermodynamic evidence for associated critical fluctuations is presented. These relatively unusual fluctuations might be pictured as variations in the Fermi surface topography itself. No equivalent behaviour has been observed in the metallic state of Sr2RuO4.Comment: 4 pages, 4 figures, Revtex 3.