An investigation of the Nd2O3-MoO3 phase system: Thermal decomposition of Nd2Mo4O15 and formation of Nd6Mo10O39

A new neodymium molybdate, Nd₆Mo₁₀O₃₉, has been identified in the Nd₂O₃-MoO₃ phase system. Nd₆Mo₁₀O₃₉ appears to be a metastable phase, which does not form directly from a stoichiometric mixture of Nd₂O₃ and MoO₃ oxides. Instead, it can be obtained by thermal decomposition of Nd₂Mo₄O₁₅. Nd₂Mo₄O₁₅ usually decomposes into Nd₂(MoO₄)₃, and the formation of Nd₆Mo₁₀O₃₉ critically depends on the heating regime used.The structure of Nd₆Mo₁₀O₃₉ has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c, with unit cell parameters of , , , β=100.767(2)°, at 120 K. Nd atoms are seven and eight coordinate, and pairs of coordination polyhedra share edges and faces, respectively, to form Nd₂O₁₂ and Nd₂O₁₃ groups. All Mo atoms are in tetrahedral coordination environments, with some of the tetrahedra sharing corners to form pyromolybdate groups.     

Peptide-nanowire hybrid materials for selective sensing of small molecules

The development of a miniaturized sensing platform for the selective detection of chemical odorants could stimulate exciting scientific and technological opportunities. Oligopeptides are robust substrates for the selective recognition of a variety of chemical and biological species. Likewise, semiconducting nanowires are extremely sensitive gas sensors. Here we explore the possibilities and chemistries of linking peptides to silicon nanowire sensors for the selective detection of small molecules. The silica surface of the nanowires is passivated with peptides using amide coupling chemistry. The peptide/nanowire sensors can be designed, through the peptide sequence, to exhibit orthogonal responses to acetic acid and ammonia vapors, and can detect traces of these gases from "chemically camouflaged" mixtures. Through both theory and experiment, we find that this sensing selectivity arises from both acid/base reactivity and from molecular structure. These results provide a model platform for what can be achieved in terms of selective and sensitive "electronic noses."     

A genetic toolbox for creating reversible Ca2+-sensitive materials

A major goal of polymer science is to develop "smart" materials that sense specific chemical signals in complex environments and respond with predictable changes in their mechanical properties. Here, we describe a genetic toolbox of natural and engineered protein modules that can be rationally combined in manifold ways to create reversible self-assembling materials that vary in their composition, architecture, and mechanical properties. Using this toolbox, we produced several materials that reversibly self-assemble in the presence of Ca2+ and characterized these materials using particle-tracking microrheology. The properties of these materials could be predicted from the dilute solution behavior of their component modules, suggesting that this toolbox may be generally useful for creating new stimuli-sensitive materials.     

Thermal kinetics and thermo‐mechanical properties of graphene integrated fluoroelastomer

In this work, the thermal properties of a fluoroelastomer enhanced by graphene were systematically investigated. Although graphene oxide (GO) is the most popular and cheapest source for graphene, its chemical and thermal properties were quite different from reduced graphene oxide (RGO). By comparing their influences on the thermal properties of elastomer, the effects from chemical structures and morphologies of graphene were analyzed. As the vulcanization and decomposition determine the properties of the elastomer proved by significantly different thermo‐mechanical properties of the fluoroelastomer reinforced by GO and RGO presented, this work provides a method to ultimate utilize graphene to reinforce elastomer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1691–1700     

Facile conversion of aptamers into sensors using a 2'-ribose-linked fluorophore

In vitro selection can be used to identify nucleic acid receptors, called aptamers, that bind diverse small molecule targets. Aptamers therefore represent an attractive platform for creating sensors. Here, we report a straightforward, semi-rational approach for converting arbitrary aptamers into reagentless, single fluorophore biosensors. The local electrostatic environment at the 2'-ribose position is exquisitely sensitive to whether a nucleotide is conformationally restrained or not. Thus, by tethering an environmentally sensitive fluorescent group at an appropriate 2'-ribose group, we are able to generically detect ligand-induced conformational changes in aptamers. Three aptamers, including one for which no significant structural information can be inferred, were converted into robust small molecule sensors that function well in simple buffers, human urine, and bovine blood serum.