Synthesis of Metal-doped Cryptomelane Nanomaterials using Cross-linking Reagents
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Synthesis of Metal-doped Cryptomelane Nanomaterials using Cross-linking Reagents Jia Liu1, Jun Cai2, Xiongfei Shen1, Steven L. Suib1, 2, 3*, Mark Aindow1,4 1 Institute of Materials Science, University of Connecticut, U-3136, Storrs, CT 06269-3136 2 Department of Chemistry, University of Connecticut, U-3060, Storrs, CT 06269-3060 3 Department of Chemical Engineering, University of Connecticut, U-3222, Storrs, CT 062693222 4 Department of Metallurgy and Materials Engineering, University of Connecticut, U-3136, Storrs, CT 06269-3136 *Corresponding author: [email protected] ABSTRACT Three cross-linking reagents (PVA, glycerol and glucose) have successfully been used to synthesize non-doped and metal-doped nanosized cryptomelane materials via a solid-state preparation method. The 2x2 tunnel structure of cryptomelane was formed at 500 ºC. FT-IR data show that no cross-linking reagent residues were found in the products after the reactions were complete at 800 ºC. The metal dopants used were Fe, Ag, Co, Cu, Ni, and Zn. XRD data show that Fe and Co cations can be doped into the materials without the formation of additional phases. The tunnel structures of the nanosized materials exhibit long-range along the b axis, as indicated by transmission electron microscopy data. High-resolution scanning electron microscopy studies show that morphologies of the products are nanorods or nanofibers, depending on the cross-linking reagents used in the preparation. Thermogravimetric analyses indicate that these nanomaterials are thermally stable to 700 ºC. INTRODUCTION In recent years, one-dimensional nanoscale structures (nanowires, nanorods, and nanotubes) have been stimulating significant interest in material chemistry due to their unique electronic, magnetic, optical, and micromechanical properties.1-8 Syntheses, properties, and applications of these nanomaterials have been the focus of many research groups. Various methods, such as laser ablation,9 template assisted chemical deposition,2 and vapor deposition/transport thchniques,8 have been used to prepare one-dimensional nanoscale metals and semiconductors. The potential applications of these materials have been explored in nanoelectronic circuits, superstrong composites, functional nanostructured materials, and novel probe microscopy tips.10-11 Here we report the synthesis of cryptomelane-type manganese oxide nanorods and nanowires. These manganese oxides have been doped with different transition metals. A sol-gel process was used to assist in the formation of nanomaterials in the solid-state preparation of raw materials. The preparation procedure is simple and fast, and can be used to prepare nanoscale materials and is different from the conventional and sol-gel methods to form bulk materials.12-15 EXPERIMENTAL DETAILS To prepare the non-doped nanostructure manganese oxides, a sol was prepared by dissolving 1.00 g (0.01 mol) of potassium nitrate and 11.66 g (0.0046 mol) of manganese nitrate
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salts in 50 mL of distilled water. A cross-linking reagent was dissolved
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