I have heard that the future of the techonolgy are the carbon nanotubes due to their resistance and conductivity, but why are they so difficult to create?
$\begingroup$ Also saying that carbon nanotubes are "the future of technology" is quite a stretch. Researchers have been able to build entire logic circuits based on them, but at the moment it seems unlike that they will make it into any commercial devices due to how hard it is to work with them. Graphene, on the other hand, seems more likely to be put to widespread practical use. $\endgroup$– ARMJul 3, 2014 at 17:34
Carbon nanotubes aren't exceptionally hard to make - making any large molecule is difficult. Come to that, making even small molecules is fairly difficult otherwise organic chemistry students wouldn't have to spend three years learning how to do it.
The usual big molecules we make, like polymers and proteins, are made in solution by combining smaller molecules. Controlling the addition and growth is hard, and even for simple polymers took a lot of working out. We still can't make most polymers with precise molecular weights - we invariably end up with a distribution of molecular weights. Making proteins is still exceedingly hard unless you get some genetically engineered organism to make them for you.
Carbon presents an extra problem in that it isn't soluble in anything - well nothing useful anyway, it's soluble in molten iron but that isn't much help! Current approaches to making nanotubes are based on forming carbon vapour and growing the tubes from the vapour phase, and we have much less experience at this than working in solutions. Still, a glance at Wikipedia tells me that yields from arc discharge approach 30%. We get a distribution of sizes of nanotube, but then as I mentioned above we get a distribution of molecular weights in most polymer syntheses.
I would add to John's answer, that once you make carbon nanotubes they come in a staggering variety and, if you're interested in reproducible properties, must be separated according to:
- Single walled / multi-walled
- Metallic / semiconducting (this property depends on exactly how the carbon sheet making the nanotube is rolled on itself)