A study of the formation, purification and application as a SWNT growth catalyst of the nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98]Electronic supplementary information (ESI) available: Fig. S1: UV-visible spectrum of the blue water-soluble fraction (in pH 2 water) formed in the synthesis of FeMoC. Fig. S2: UV-visible spectra (in H2O @ pH 2) of the yellow solid formed in the synthesis of FeMoC and Keplerate. Fig. S3: ATR of the blue fraction formed in the synthesis of FeMoC. Fig. S4: Comparison of ATR spectra of Keplerate and the yellow solid formed in the synthesis of FeMoC. Fig. S5: Representative tapping mode AFM image (2 × 2 μm) and associated height analysis of FeMoC-EtOH. Fig. S6: ATR of FeMoC-EtOH solid. Fig. S7: SEM micrograph of SWNTs grown from aged FeMoC-EtOH on a spin-on-glass surface. Fig. S8: Raman spectrum of surface after growth run with FeMoC. See DOI: 10.1039/b518395b

Autor: Anderson, Robin E., Colorado, Ramon, Crouse, Christopher, Ogrin, Douglas, Maruyama, Benji, Pender, Mark J., Edwards, Christopher L., Whitsitt, Elizabeth, Moore, Valerie C., Koveal, Dorothy, Lupu, Corina, Stewart, Michael P., SmalleyDeceased., Richard E., Tour, James M., Barron, Andrew R.
Zdroj: Dalton Transactions; 2006, Vol. 2006 Issue: 25 p3097-3107, 11p
Abstrakt: The synthetic conditions for the isolation of the iron–molybdenum nanocluster FeMoC [HxPMo12O40⊂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 (δ−5.3 ppm) suggests little effect of the paramagnetic Fe3centers in the Keplerate cage on the Keggin ion's 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 ion's phosphorus symmetrically located within the Keplerate cage. Increasing the FeCl2concentration 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 work's reported growth of SWNTs from FeMoC is discussed with respect to these results.
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