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This work reports the incorporation of ferrocene into a porous silica glass under ambient temperature and atmosphere. After or during the ferrocene incorporation, the spontaneous formation of ferricinium ions was observed by electron paramagnetic resonance (EPR), UV-visible, X-ray absorption near-edge structure (XANES), and 57Fe Mössbauer measurements. It was shown that the oxidation of ferrocene molecules to ferricinium ions was promoted by air and that the Si-O- groups on the surface of the pores act as counteranions. Pyrolysis of the porous glass/ferricinium material under argon atmosphere and variable temperature yields different glass/carbon nanocomposites, which were subsequently treated with an HF solution in order to remove the glassy fraction. The resulting insoluble carbon materials were characterized by transmission electron microscopy (TEM), Raman, and EPR spectroscopy and consisted of amorphous carbon when the pyrolysis was carried out at 900 or 1000 degrees C and of a mixture of carbon nanotubes and carbonaceous materials at a pyrolysis temperature of 1100 degrees C. When the pyrolysis was conducted under air, the incorporated ferricinium forms alpha-Fe2O3, and the resulting material is a transparent and highly homogeneous glass/iron oxide nanocomposite.

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We measure the current-voltage (J-V ) characteristics of organic composites as a function of carbon nanotubes concentration dispersed in a poly-3-hexilthiophene (P3HT) matrix. From a drift-diffusion-space-charge model and adapting the general effective medium and classical percolation theories, we quantify the system transport features. We find a drastic increase of the injection current due to drain channels provided by the nanotubes, probably a universal mechanism for charge injection in such type of system. We identify a percolation transition (with t = 0.3, the lowest critical exponent so far reported in the literature) and a fractal structure for transport after the percolation. This nearly 1D structure is surprising since the composites do not have any peculiar orientation along some preferential direction. Supported by transmission electron microscopy we explain the fractal behavior in terms of the morphology of the conductivity paths.

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