Characterisation of dry materials
Size, shape and distribution
Due to their nature, the size and size distribution of nanoparticles play a critical role in defining their properties and the behaviour of their resulting products. NPL has access to a large array of complementary analytical techniques, which means we can provide analysis of virtually any nanomaterial, whether as a powder or dispersed in a liquid medium.
Electron Microscopy
Electron microscopy provides high resolution images with nanometre resolution. The material has to by dry and this approach is excellent at detecting and analysing the primary particles. The three major configurations available are Transmission (TEM), Scanning (SEM) and Scanning Transmission (STEM).
Scanning Probe Microscopy
This technique overcomes some of the limitations of electron microscopy; measurements can be taken under ambient conditions or in a liquid (electron microscopy requires the specimen to be under vacuum). In addition there is a direct route to traceability, unlike electron microscopy. This approach does suffer from difficult to remove image artefacts if other than spherical nanoparticles are analysed.
Surface area and porosity
Both of these parameters can be measured using Brunauer-Emmett-Teller (BET) analysis. This gives area of exposed particle (although the measured specific area may not necessarily mean that which is available) as determined by the adsorption of nitrogen gas. Here porosity is defined as the percentage pore space within a given volume. The Barrett-Joyner-Halenda (BJH) method will be used to determine the porosity.
Surface chemistry
The surface chemistry of nanomaterials will often be different that the bulk, either by the deliberate coating or the adsorption of materials (such as proteins) from the environment. The surface chemistry needs to be analysed, for example to:
- ensure the coating of the particles has been successful
- detect the presence of adsorbed material
The two main methods are:
Contact
Customer Service tel: +44 20 8943 8637
E-mail: nanoanalysis_enquiries@npl.co.uk