Robin E. Anderson

A study of the formation, purification and application as a SWNT growth catalyst of the nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98]

The synthetic conditions for the isolation of the iron-molybdenum nanocluster FeMoC [HxPMo12O40 [subset]H4Mo72Fe30(O2CMe)15O254(H2O)98], along with its application as a catalyst precursor for VLS growth of SWNTs have been studied. As-prepared FeMoC is contaminated with the Keplerate cage [H4Mo72Fe30(O2CMe)15O254(H2O)98] without the Keggin [HxPMo12O40]n- template, however, isolation of pure FeMoC may be accomplished by Soxhlet extraction with EtOH. The resulting EtOH solvate is consistent with the replacement of the water ligands coordinated to Fe being substituted by EtOH. FeMoC-EtOH has been characterized by IR, UV-vis spectroscopy, MS, XPS and 31P NMR. The solid-state 31P NMR spectrum for FeMoC-EtOH (delta-5.3 ppm) suggests little effect of the paramagnetic Fe3+ centers in the Keplerate cage on the Keggin ions phosphorous. The high chemical shift anisotropy, and calculated T1 (35 ms) and T2 (8 ms) values are consistent with a weak magnetic interaction between the Keggin ions phosphorus symmetrically located within the Keplerate cage. Increasing the FeCl2 concentration and decreasing the pH of the reaction mixture optimizes the yield of FeMoC. The solubility and stability of FeMoC in H2O and MeOH-H2O is investigated. The TGA of FeMoC-EtOH under air, Ar and H2 (in combination with XPS) shows that upon thermolysis the resulting Fe : Mo ratio is highly dependent on the reaction atmosphere: thermolysis in air results in significant loss of volatile molybdenum components. Pure FeMoC-EtOH is found to be essentially inactive as a pre-catalyst for the VLS growth of single-walled carbon nanotubes (SWNTs) irrespective of the substrate or reaction conditions. However, reaction of FeMoC with pyrazine (pyz) results in the formation of aggregates that are found to be active catalysts for the growth of SWNTs. Activation of FeMoC may also be accomplished by the addition of excess iron. The observation of prior works reported growth of SWNTs from FeMoC is discussed with respect to these results.

Effect of carbon nanomaterials on calcium carbonate crystallization

The addition of the water-soluble carbon nanomaterials, fullerenol (C60(OH)n), hydroxylated single walled carbon nanotubes (HO-SWNTs) and isophthalic acid functionalized-SWNTs (IPA-SWNTs), alter the morphology and crystal phase of CaCO3 precipitates form aqueous solution. CaCO3 precipitation in the presence of C60(OH)n results in the formation of spherical features, 5-pointed flower shaped clusters, and triangular crystals as opposed to the usual rhombic crystals. In addition, the meta-stable vaterite phase is observed with the addition of C60(OH)n. The effect on crystal growth of the C60(OH)n is not a simple function of the pH of the solution, although it may be due to reactivity of the hydroxyl groups. Precipitation with water-soluble HO-SWNT and IPA-SWNTs produces CaCO3 coated SWNTs with the CaCO3 being amorphous rather than crystalline.