Two-Dimensional Crystalline Lattice Templating: A New Method for the Preparation of Polymer-Covered Metal and Alloyed Me
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Two-Dimensional Crystalline Lattice Templating: A New Method for the Preparation of Polymer-Covered Metal and Alloyed Metal Nanorods by a Redox Process. Alexandru C. Pavel1, Dwight K. Romanovicz1, Miguel J. Yacaman2, John T. McDevitt1 1 Department of Chemistry & Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165 2 Department of Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, Texas 78712-0231 ABSTRACT We demonstrate in this paper that two-dimensional (2-D) layered ceramics, materials that are highly anisotropic in terms of structure and properties can be used to induce the formation of polymer-covered metal nanorods. The procedure took advantage of the intrinsic planar, layered ordering of the metal cations suitable to be reduced and can be further used to engineer onedimensional (1-D) metal alloy nanostructures by appropriate doping of the initial layered ceramic lattice with suitable cationic species. The procedure involved the formation in an intermediate step of a polymer-layered ceramic nanocomposite, highly porous to the diffusion of the reducing agent. Two structurally similar layered bismuthates, Bi2Sr2CaCu2O8+δ and Bi6Sr2CaO12 were used as the precursor layered ceramics and the redox-active metal cations were Cu2+ and Bi3+.
INTRODUCTION Layered inorganic lattices have been used as host materials for guest organic monomers in intercalation reactions [1], with the purpose to create homogeneous nanocomposites with an improved set of physical and chemical properties when compared to the individual parent compounds, and that can be subsequently applied in the targeted practical applications [2]. The two layered bismuthates, Bi2Sr2CaCu2O8+δ and Bi6Sr2CaO12 are related through similar cationic composition and the presence of van der Waals gaps between Bi-O…Bi-O consecutive layers that can host the polypyrrole chains [3,4]. Polypyrrole is one of the most representative electronic conductive polymers and its monomer, pyrrole, has been extensively used as a guest species for the in situ polymerization in layered and microporous inorganic lattices [5].
EXPERIMENTAL DETAILS Bi2Sr2CaCu2O8+δ and Bi6Sr2CaO12 were synthesized by a solid-state procedure in which appropriate amounts of cationic precursors (Bi2O3, 99.999%-Bi, SrCO3, 99.9%-Sr, CaCO3, 99.95%-Ca, CuO, 99.5+%-Cu, all Strem Chemicals) were subjected to several cycles of grinding and annealing. Preparation of Bi2Sr2CaCu2O8+δ consisted of 12-24 hours high temperature annealing treatments with intermittent grindings. The ramp rate was 100°C/hr and the annealing temperatures were 775, 800, 820, 840 and 860°C. A similar annealing treatment was applied for Bi6Sr2CaO12 and the employed temperatures were 725, 750, 775, 790 and 800°C. The crystalline structure of the final ceramics was checked by powder X-ray diffraction (XRD, run on a D8 Advance, Brucker). In the second step of the procedure, iodine atoms were intercalated in the
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van der Waals gaps of the two c
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