Something new from something old and blue

Earlier this year, US researchers unveiled a new class of “cool blues”.

Now a German team has used one of the oldest blues to produce something very modern –nanosheets for near infrared imaging.

“Egyptian blue” was created more than 4000 years ago and is perhaps best known for adorning the crown of the bust of Nefertiti, one of the most famous – and most copied – items of Egyptian art.

Also known, rather less romantically, as calcium copper silicate, it is considered the first synthetic pigment. 

Now researchers led by Sebastian Kruss from the Institute of Physical Chemistry at the University of Göttingen have succeeded in exfoliating extremely thin layers from grains of Egyptian blue to produce a nanomaterial they say is ideally suited for applications in imaging using near infrared spectroscopy and microscopy. 

Microscopy and optical imaging use fluorophores, which can release light when excited, to stain very small structures in samples, enabling clear resolution using modern microscopes. 

Most fluorophores shine in the range of light visible to humans. 

Using light in the near infrared spectrum – with a wavelength starting at 800 nanometres – is better because the light penetrates even deeper into tissue and there are fewer distortions to the image. However, there currently are only a few known fluorophores that work in the near infrared spectrum.

The nanosheets developed by Kruss and his colleagues do – and they are 100,000 times thinner than a human hair. 

“We were able to show that even the smallest nanosheets are extremely stable, shine brightly and do not bleach, making them ideal for optical imaging,” he says.

The team says it tested its idea for microscopy in animals and plants. For example, it followed the movement of individual nanosheets in order to visualise mechanical processes and the structure of the tissue around cell nuclei in the fruit fly. 

In addition, it integrated the nanosheets into plants and was able to identify them even without a microscope, which promises future applications in the agricultural industry. 

“The potential for state-of-the-art microscopy from this material means that new findings in biomedical research can be expected in the future,” says Kruss.

The research is published in the journal Nature Communications.