Metal-chelating nanoparticles as selective fluorescent sensor for Cu2+

A fluorescent sensor for Cu(2+) at the nanomolar level in water has been designed by associating a BODIPY fluorophore and a selective ligand (cyclam) in ultrafine polymer nanoparticles.     

Sweet success: Ionic liquids derived from non-nutritive sweeteners

The anions of the sweeteners saccharin and acesulfame form ionic liquids when paired with a variety of organic cations.     

Edge effects on the order and freezing of a 2D array of block copolymer spheres

The order in a single layer of spherical domains of a block copolymer melt is investigated as a function of distance from the edges of the 15 microm wide, 30 nm deep wells that confine it along a substrate. At 255 degrees C the edge induces the formation of a hexatic phase whose orientational and translational order decreases slowly away from the edge until in the center of the well the block copolymer spheres have liquidlike order.     

Ternary complexes between cationic GdIII chelates and anionic metabolites in aqueous solution: an NMR relaxometric study

The (1)H and (17)O NMR relaxometric properties of two cationic complexes formed by Gd(III) with a macrocyclic heptadentate triamide ligand, L(1), and its Nmethylated analogue, L(2), have been investigated in aqueous media as a function of pH, temperature and magnetic field strength. The complexes possess two water molecules in their inner coordination sphere for which the rate of exchange has been found to be sensibly faster for the Nmethylated derivative and explained in terms of electronic effects (decrease of the charge density at the metal center) and perturbation of the network of hydrogen-bonded water molecules in the outer hydration sphere. The proton relaxivity shows a marked dependence from pH and decreases of about six units in the pH range 6.5 to 9.0. This has been accounted for by the displacement of the two water molecules by dissolved carbonate which acts as a chelating anion. The formation of ternary complexes with lactate, malonate, citrate, acetate, fluoride and hydrogenphosphate has been monitored by (1)H NMR relaxometric titrations at 20 MHz and pH 6.3 and the value of the affinity constant, K, and of the relaxivity of the adducts could be obtained. Lactate, malonate and citrate interact strongly with the complexes (log K > or =3.7) and coordinate in a bidendate mode by displacing both water molecules. Larger affinity constants have been measured for GdL(2). Acetate, fluoride and hydrogenphosphate form monoaqua ternary complexes which were investigated in detail with regard to their relaxometric properties. The NMR dispersion (NMRD) profiles indicate a large contribution to the relaxivity of the adducts from water molecules belonging to the second hydration shell of the complexes and hydrogen-bonded to the anion. A VT (17)O NMR study has shown a marked increase of the rate of water exchange upon binding which is explained by coordination of the anion in an equatorial site, thus leaving the water molecule in an apical position, more accessible for interactions with the solvent molecules of the second hydration shell which facilitate the exchange process.     

Scanning probe-based frequency-dependent microrheology of polymer gels and biological cells

A new scanning probe-based microrheology approach is used to quantify the frequency-dependent viscoelastic behavior of both fibroblast cells and polymer gels. The scanning probe shape was modified using polystyrene beads for a defined surface area nondestructively deforming the sample. An extended Hertz model is introduced to measure the frequency-dependent storage and loss moduli even for thin cell samples. Control measurements of the polyacrylamide gels compare well with conventional rheological data. The cells show a viscoelastic signature similar to in vitro actin gels.     

Calibration and evaluation of optical systems for full-field strain measurement

The design and testing of a reference material for the calibration of optical systems for strain measurement is described, together with the design and testing of a standardized test material that allows the evaluation and assessment of fitness for purpose of the most sophisticated optical system for strain measurement. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components or sub-systems in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.     

One-pot preparation and uranyl adsorption properties of hierarchically porous zirconium titanium oxide beads using phase separation processes to vary macropore morphology

A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H(2)O beads) or liquid nitrogen (LN(2) beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m(2) g(-1), respectively, and had varied pore architectures. The H(2)O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN(2)-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.     

Synthesis and magnetic properties of Gd doped EuS nanocrystals with enhanced Curie temperatures

EuS nanocrystals (NCs) were doped with Gd resulting in an enhancement of their magnetic properties. New EuS and GdS single source precursors (SSPs) were synthesized, characterized, and employed to synthesize Eu(1-x)Gd(x)S NCs by decomposition in oleylamine and trioctylphosphine at 290 °C. The doped NCs were characterized using X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, which support the uniform distribution of Gd dopants through electron energy loss spectroscopy (EELS) mapping. X-ray absorption spectroscopy (XAS) revealed the dopant ions in Eu(1-x)Gd(x)S NCs to be predominantly Gd(3+). NCs with a variety of doping ratios of Gd (0 ≤ x < 1) were systematically studied using vibrating sample magnetometry and the observed magnetic properties were correlated with the Gd doping levels (x) as quantified with ICP-AES. Enhancement of the Curie temperature (T(C)) was observed for samples with low Gd concentrations (x ≤ 10%) with a maximum T(C) of 29.4 K observed for NCs containing 5.3% Gd. Overall, the observed T(C), Weiss temperature (θ), and hysteretic behavior correspond directly to the doping level in Eu(1-x)Gd(x)S NCs and the trends qualitatively follow those previously reported for bulk and thin film samples.     

Synthesis of bifunctional peptide derivatives based on a β-cyclodextrin core with drug delivery potential

A selective, versatile, robust methodology for bifunctionalization of β-cyclodextrin is achieved allowing the attachment of peptides in varying C- and/or N-terminal combinations on resin using Fmoc SPPS. Two linkers are attached to cyclodextrin enabling selective binding to the resin (or a peptide attached to the resin). Continuation of peptide growth and/or cleavage from the resin follows, thus various combinations of peptide-cyclodextrin species are achieved. A model peptide (Gly-Ala) is used in this study to illustrate the potential of this system for attaching one or more bioactive peptides for drug transport and release purposes.