Carbon nanotubes (CNT), first discovered by Iijima [1] in 1991, have led to a revolution in material science. CNT's have many interesting mechanical properties which have led to some researchers making remarkable predictions about their possible uses from nanoscale machines to earth-quake-resistant buildings. Their primary use is likely to be in electronics as interconnects and/or devices. This will however mean that they will have to be controllably placed at very precise locations or grown insitu at temperatures low enough to be compatible with CMOS circuitry.

Thus, for on-chip requirements it is necessary to develop: 1) a simple method for processing CNTs at low temperatures; 2) a method which allows nanotubes to be produced non-destructively in a controlled manner 3) have a process whereby the position of nanotubes can be simply pre-determined. At UCC we have shown that CNTS can be prepared in a similar manner to that of Park et al. using heterogeneous rather than homogeneous catalyst sources [2]. Here, pre-doped (Zr/Co/Fe) mesoporous silicas were used as catalysts. Sonification in chloroform leads to the synthesis of both MWNTs and SWNT bundles. The product shows a strong dependance on sonification power. TEM shows that the CNTs grow via a tip growth mechanism. Raman spectroscopy showed that good quality CNTs were produced. The UCC work shows that it is possible to use a heterogeneous catalyst compared to a homogeneous phase (i.e. liquid ferrocene) suggesting that the reaction may be modified to allow surface processing.

The catalytic activity is primarily due to their novel physiochemical properties and in particular their very high surface areas [3]. We have also pioneered methods of tailoring pore sizes to between 2 and 11 nm [4] diameter and the in-situ modification of mesoporous silicas with the transition element additives. All of the modified mesoporous silicas were characterized using the analytical techniques of x-ray diffraction, BET/BJH surface analysis, x-ray fluorescence spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy.

1. Iijima, S., Nature, 354 (1991) 56

2. Jeong, S.; Ko, J.; Park, J.; Park, W., J. Am. Chem. Soc., 126(2004)15982

3. Kresge, C. T., Leonwicz, M. E., Roth, W. J., Vartulli, J. C., Beck, J. S., Nature, 359 (1992) 710

4. Hanrahan, J.P., Copley, M.P., Ryan, K.M., Spalding, T.R., Morris, M.A., Holmes, J.D., Chem. Mater. 16 (2004) 424

Keywords: Carbon nanotubes, sonification, low temperature, mesoporous silica

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