About Me

My photo
Independent Professional: Experienced educator and management consultant for engineering educational institutions, researcher, trainer, technical consultant on sustainable technologies, related to cement manufacturing and characterisation, using industrial and agricultural wastes in cement and concrete, durability of concrete and fuel cell power.

Friday, September 25, 2009

Carbon nanotubes: How safe ?

Carbon nanotubes are increasingly being used in everyday products such as sporting equipment, biomedical devices and aeroplanes. They also have promising applications in fuel cells. The questions remain as to how safe these nanotubes really are.

The main factor in nanotube toxicity are the metal contaminants that remain from manufacture, which are typically one to ten per cent by weight, say Martin Pumera and Yuji Miyahara at the National Institute for Materials Science, Ibaraki, Japan. The carbon nanotubes are often viewed as homogenous materials, which is incorrect. They often contain impurities which are not even listed by the manufacturers. The pair have used an electrochemical (biomarker) method to assess the effect metals have on nanotube toxicity. They say that their method is quicker and cheaper than laborious and expensive biomedical tests and could be more useful for initial assessments of carbon nanotube toxicity.

They found that just 100 ppm of iron was needed to dominate the reduction ability and therefore the toxicity. Pumera says this is very disturbing, as this value is significantly lower than the detection limits of the methods routinely used to assess nanotube purity. There is an imperative need for well-characterised and reproducible standardised carbon nanotube properties.

What amount of metallic impurities in carbon nanotubes is small enough not to dominate their redox properties?

Martin Pumera and Yuji Miyahara, Nanoscale, 2009