Nanocrystals to nanorods: A precursor approach for the synthesis of magnesium hydroxide nanorods from magnesium oxychloride nanorods starting from nanocrystalline magnesium oxide

Nanorods of magnesium oxychloride (Mg-x(OH)(y)Cl-z center dot nH(2)O) and magnesium hydroxide (Mg(OH)2) have been produced from crystalline MgO. Concentrated aqueous magnesium chloride (MgCl2 center dot 6H(2)O), when allowed to react with MgO, yields oxychloride nanorods that can be converted into Mg(OH)2 nanorods using NaOH, with retention of the nanorod morphologies. A comparison of powdered MgO starting materials has shown that, by proper choice of reagent concentrations, temperature, and aging time, nanorods can be obtained in all cases, but tranocrystalline (NC)-MgO gives the highest yields and the highest aspect ratios (aspect ratios of about 60-90 in the oxychloride system). The higher surface area and higher reactivity of NC-MgO allow the rapid formation of nucleation sites in large numbers that subsequently grow into thin (similar to 170 nm) oxychloride nanorods. The nanorods of Mg-x(OH)(y)Cl-z center dot nH(2)O and Mg(OH)(2) were characterized by powder X-ray diffraction and transmission electron microscopy measurements.