A family of lithium electrolyte materials based on a polymer−inorganic hybrid is described. The base material is a blend of poly(ethylene oxide) and an organic−inorganic composite made from polyether-functionalized methoxysilanes and aluminum alkoxides. Lithium is incorporated through addition of a salt. The resulting materials are shown through a combination of methods, including transmission electron microscopy and solid-state NMR, to consist of an amorphous inorganic network, with nanoscopic voids, which stabilize the added polymer. The composite polymer electrolytes show good resistance to crystallization and good conductivity, as determined by differential scanning calorimetry and impedance measurements, respectively. The nanoscale structure of the underlying inorganic material is concluded to be responsible for the bulk properties of the system, especially those that differ from the properties of similar, pure salt-in-polymer electrolytes.

Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses.

The mechanism of heterogeneous ice nucleation on inorganic substrates is not well understood despite work on AgI and other materials over the past 50 years. We have selected BaF(2) as a model substrate for study since its (111) surface makes a near perfect match with the lattice of the basal face of I(h) ice and would appear to be an ideal nucleating agent. Two series of experiments were undertaken. In one, nucleation of thin film water formed from deposition of vapor on BaF(2)(111) faces was explored with the finding that supercooling to -30 degrees C was required before freezing occurred. In the other series, nucleation of liquid water on submerged BaF(2) crystals was studied. Here supercooling to -15 degrees C was needed before ice formed. The reason why BaF(2) is such a poor nucleating agent contains clues to realistic mechanisms of heterogeneous nucleation. Our explanation of these results follows the model of Fletcher [J. Chem. Phys. 29, 572 (1958)] who showed that heterogeneous ice nucleating ability depends on how well ice wets a substrate. In this view, a smooth BaF(2)(111) face is poor at nucleation because ice only partially wets its surface. In an extension of Fletcher's model, our calculations, consistent with the experimental results demonstrate that the pitting of a submerged BaF(2) crystal dramatically improves its ice nucleating ability.

A hybrid material comprised of beta-tricalcium phosphate (beta-TCP) and sodium lauryl sulfate (SLS) was prepared using a mechanochemical process, examined using particle size analysis, IR spectroscopy, (31)P, (23)Na, and (13)C solid-state NMR spectroscopy, and calcium dissolution experiments, and probed for in vitro remineralization of subsurface enamel lesions. Our results suggest that while the (31)P environments of beta-TCP remain unchanged during solid-state processing, there is noticeable shifting among the SLS (23)Na and (13)C environments. Therefore, given the structure of beta-TCP, along with our IR examinations and calcium dissolution isotherms, SLS appears to interface strongly with the cation deficient C(3) symmetry site of the beta-TCP hexagonal crystal lattice with probable emphasis placed on the underbonded CaO(3) polyhedra. To demonstrate the utility of the surface-active TCP material in dental applications, we combined the TCP-SLS with 5,000 ppm F (NaF) and evaluated the remineralization potential of subsurface enamel lesions via an in vitro remineralization/demineralization pH cycling dental model. Using surface and longitudinal microhardness measurements, the TCP-SLS plus 5,000 ppm F system was found to significantly boost remineralization of subsurface enamel lesions, with microhardness values increasing up to 30% greater than fluoride alone.