How XRF can help carbon nanotubes become the supermaterial of the future

Carbon nanotubes are an example of a nanoscale material with extraordinary properties such as high strength, large surface area, and fine-tuned conductivity. So why aren’t they more widely used today? The complexity of their production and toxicity have been limiting factors – but state-of-the-art analytical tools can be the solution.

What are carbon nanotubes and why are they useful?

Carbon nanotubes are tubes of carbon with an average diameter of 0.5 to 2 nanometers – about 100,000 times smaller than the width of a human hair.

Depending on their structure, carbon nanotubes can be highly conductive or act as semiconductors. They are also chemically inert, so they can be chemically modified, and their high surface area provides more active sites where chemical reactions can take place.

As a result, carbon nanotubes have many potential applications. For example, their conductivity makes them suitable for both power generation and energy storage. Their chemical flexibility and surface area mean they’re also great for drug delivery applications, or as support materials for heterogeneous catalysis.

What are the issues with carbon nanotubes?

One of the key challenges in driving more widespread adoption of carbon nanotubes is their manufacture. This is typically done by catalytic chemical vapor deposition (CCVD). Carbon nanotubes are produced by the catalytic decomposition of hydrocarbon vapors at temperatures around 700°C, which is a relatively simple and cost-effective process.

However, this process uses metal nanoparticles such as iron, nickel, cobalt and molybdenum as catalysts, and metal oxides like magnesium and aluminum oxide as catalyst support materials. Their use and the high heat of the process can result in metallic impurities.

These residues can be detrimental to the final application, with toxicity being particularly harmful in biomedical applications. The solution is analysis that can detect traces of any residue – and X-ray fluorescence (XRF) is an easy and rapid method that can screen for impurities in many applications.

How does XRF work?

XRF spectrometry is a mainstay of rapid residue and contaminant screening in many industries. When X-rays are projected onto a material, the atoms that make up the material ‘reflect’ the X-rays strongly according to their number of electrons. These ‘fingerprints’ therefore reveal both the presence of elements and their proportions in a sample.

XRF has several strengths that make it ideal for carbon nanotube analysis. It’s extremely accurate and sensitive and can measure a range of elements down to parts per million (ppm) concentrations: when measuring concentrations, its typical margin of error is only 0.1 to 0.3%. It’s applicable to all sample types, and samples are very easy to prepare. The analysis itself is very fast, and it’s non-destructive, so the same sample can be analyzed over and over again, and even returned to the production line.

What is XRF used for?

Elemental analysis with XRF has many functions in carbon nanotube manufacture. It can help you control the composition of carbon nanotubes when they’re used as catalyst supports, as well as carbon nanotube dopant levels and concentrations. XRF can provide fast and reliable purity measurements in applications such as cosmetics, personal care, pharmaceuticals, and food packaging.

XRF can therefore help to unlock the true potential of carbon nanotubes. Firstly, by enabling manufacturers to control toxicity through the measurement of residues and impurities. And secondly, by helping to optimize the amount of catalyst and catalyst support materials used, further improving cost-efficiency.

Meet the small, powerful, and portable XRF analyzer

Malvern Panalytical’s ideal solution for rapid carbon nanotube analysis is the Epsilon 1 XRF analyzer. It has all the strengths of traditional XRF spectrometers: it can measure all types of samples, from no sample preparation up to the most precise fused beads. It has simple and fast operation with all sample types and very high accuracy for its class. It can also be pre-calibrated with the Omnian standardless analysis, which means it’s ready to deliver repeatable results without the need for on-site calibration. For the most precise results, it can also be used in standard calibrate modes using certified reference materials.

With almost no running costs and a very small footprint – it weighs only 24 kg – the Epsilon 1 can easily find its place in the laboratory of a carbon nanotube research or production facility. Maintaining its calibration for years, the Epsilon is perhaps as future-proof as carbon nanotubes themselves!

Need help designing the most efficient XRF workflow possible? Read more about our elemental analytical workflow end-to-end solutions.

Do you want to use automated XRF screening of films on rolling membrane supports? Take a look at our X-Line product!