Being able to identify nanoscale cracks and deformities is important to maintain the integrity of a product. Traditional methods for visualizing nanoparticles have often proved unsatisfactory, as they only give an average for size distributions in samples, or are biased towards larger particles. This means that some defects often go undetected.
Now, NanoSight Ltd, a UK manufacturer of optical and analysis instruments, has developed a method for accurately visualising individual nanoscale particles.
The NanoSight LM20 makes use of a technique called Nanoparticle Tracking Analysis (NTA), which provides the user with a simple and direct qualitative view of a sample. Independent quantitative estimation of particle magnitude and size distribution is immediately obtained.
Traditional characterisation tools for nanoparticles are Photon Correlation Spectroscopy (PCS) and electron microscopy.
‘PCS biases towards the largest particles, while a lot of electron micrographs are required to get a statistically acceptable result,' explains Jeremy Warren, Chief Executive of NanoSight.
‘[Our product] detects the small as well as the large.'
The system uses a conventional optical microscope fitted with a specialised camera and dedicated analytical software. The NTA technique involves a metallised optical plate illuminated by a laser beam that is 80 micrometres in diameter. Nanoscale samples of 106 particles per ml, that are diluted in a solvent, are placed on the plate and directed into the light beam. The camera videos all the particles in the light, tracking each simultaneously.
To get the right concentration of dilution, ‘the cell is filled with the sample particle at too-high a concentration, then flushed with solvent while observing the dilution progressing in real time,' explains Warren.
‘This technique also picks up any dust or contaminants, which shine out like supernova under NanoSight. Once the ideal concentration has been achieved, a dilution protocol makes the process easier. ‘Getting a view takes seconds, when the viewing concentration has been established,' he adds.
The NanoSight LM20's analysis range is 10-600nm, although the system has picked up silver at 8nm.
‘That is the smallest we have detected yet.' The company has been approached by members of both the commercial and academic fields. ‘In almost all cases the users already have [PCS], and recognise NanoSight as complementary,' says Warren.
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