The difficulties and sheer breadth of characterisation were among the topics discussed at Advances in Measurement of Nanomaterials and Their Impact on Man and the Environment, held on September 14 in Oxford, UK. Eoin Redahan reports

‘There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know’.

No one expected the former US Secretary of Defense Donald Rumsfeld to feature in a nanomaterial measurement conference; but his words, cited by Dr Steve Hankin, Director of Operations at SAFENANO in Edinburgh, encapsulate some of the difficulties encountered by industry professionals.

When you pick up sunscreen or breathe in the London air, nanomaterials are there. But, they are hard to characterise and measure. Time can change them, water can warp them and measuring equipment can taint samples.

It is a young industry, but a lucrative one. According to Dr Marshall, there are about 1,300 products on the market with nanomaterials in them.

Standard practice

Unfortunately, standards are currently based on consensus and are voluntary unless agreed by contract or referenced in regulations. Peter Hatto, Director of Research at Ionbond Ltd in Consett, UK, and former Chairman of the International Organisation for Standardisation Technical Committee for Nanotechnologies (ISO/TC 229), said that better characterisation could promote innovation and commercialisation.

‘If you can use a standard measurement method then you can compare data,’ he explains. While this might seem straightforward, various factors make the characterisation of nanomaterials very tricky.

Carbon nanotubes exemplify the magnitude of the task. Dr Alison Crossley, Manager of Oxford Materials Characterisation Services, UK, said, ‘Trying to find nanomaterials is like finding a needle in a haystack. In fact, it’s like finding a piece of straw in a haystack. You’re trying to find carbon in carbon.’ She showed slides of carbon nanotubes in various guises, including zig-zag, armchair and chiral structures, which underlined the growing range of characterisation criteria.

Storage, too, can tinker with a nanomaterial’s properties, and the preparation of a sample for inspection can change its size and shape. To illustrate this, Crossley provided the example of two zinc oxide slides that changed significantly after ultrasonication. ‘Even if commercially available nanotubes are labelled as being the same,’ she said, ‘they can have very different properties’. Pete Dobson, Academic Director of Begbroke Science Park at the University of Oxford, UK, noted, ‘Zinc oxide dissolves. For example, after an hour, the particles were much smaller. If you left that bottle on the shelf, I can guarantee you it will look very different in a month’s time’.

Equipped for change

Relevant equipment choice and the expertise of analysis professionals were prominent among delegate concerns. Different measurement methods and environments can produce completely different results.

‘It’s difficult to compare toxicity data between different labs,’ claimed Dr Damian Marshall, Principal Scientist at LGC in Teddington. ‘Variations make it difficult to compare data. For example, copper oxide becomes more toxic, the lower the cell number, whereas zinc oxide is the opposite.’

Different methods boast different strengths. Raman spectroscopy is useful for measuring surface area, scanning electron microscopy is adept at providing information at different length scales, and the noninvasive virtues of terahertz technology have been lauded, but as one delegate surmised, ‘There is no single instrument that will give you a measure of all matrices’.

The overriding impression was that equipment should be used to characterise only what is absolutely relevant, and that machine operators must be well-trained to keep measurements of the sample consistent.

Towards closer collaboration

For all the industry’s difficulties, links are being forged. Hatto and his colleagues at (ISO/TC 229) have published 13 standards, with another 31 under development. In response to an EU Commission call for a standardisation of specific nanotechnology and nanomaterial properties, 40 additional standards have been identified by the European Committee for Standardisation’s Technical Committee for Nanotechnologies.

Andreas Falk, Coordinator of BioNanoNet in Graz, Austria, spoke of increased collaboration among Austrian nanotechnologists, and tentative agreements with counterparts in Germany, Greece, Hungary and the UK that could lead to a European hub system for consultation. He explained that interest in such a structure was considerable, but that, ‘the main bottleneck is the financial structure’.

Even then, there are grounds for financial optimism. Earlier, Hatto made two very important points. He mentioned that nanotechnology is still in its infancy, and lamented that it may not be a trillion dollar industry by 2015. Arguably, this represents considerable progress.

Regardless of the improved collaboration and financial impetus that will come with age, though, the characterisation process looks set to remain arduous.

Defining nanomaterials

The European Chemical Industry Council (Cefic) has applauded the European Commission’s efforts to create a regulatory definition for nanomaterials, though it is concerned that the definition is too broad in scope. Cefic fears that, in its current form, the proposed definition would define certain substances as nanomaterials, such as the mineral pigments found in paints and some other products. Website: www.cefic.org