A Study Of The Formation, Puri. Cation And Application As A Swnt Growth Catalyst Of The Nanocluster [Hxpmo12o40 Subset Of H4mo72fe30(O2cme)(15)O-254(H2o)(98)]

The synthetic conditions for the isolation of the iron-molybdenum nanocluster FeMoC [HxPMo(12)O(40)subset of H4Mo72Fe30(O2CMe)(15)O-254(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) O-15(254)(H2O)(98)] without the Keggin [ HxPMo(12)O(40)](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 P-31 NMR. The solid-state P-31 NMR spectrum for FeMoC-EtOH (delta - 5.3 ppm) suggests little effect of the paramagnetic Fe3+ centers in the Keplerate cage on the Keggin ion's phosphorous. The high chemical shift anisotropy, and calculated T-1 (35 ms) and T-2 ( 8 ms) values are consistent with a weak magnetic interaction between the Keggin ion's 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 H-2 ( 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 signi.cant 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 work's reported growth of SWNTs from FeMoC is discussed with respect to these results.