Egyptian blue is one of the oldest artificially produced color pigments. For example, it adorns the crown of the world-famous bust of Nefertiti. But the pigment can do even more.

An international research team led by Dr. Sebastian Kruss from the Institute of Physical Chemistry at the University of Göttingen has produced a new nanomaterial based on the Egyptian blue pigment, which is ideal for applications in imaging using near-infrared spectroscopy and microscopy. The results have been published in the journal Nature Communications .

Microscopy and optical imaging are important tools in basic research and in biomedicine. Substances are used that can release light after stimulation. With these fluorophores, very small structures are stained in samples and resolved in modern microscopes. Most fluorophores shine in the range of light visible to humans. In the adjacent area, the near infrared (NIR) with a wavelength of 800 nanometers or more, the light penetrates even deeper into the tissue, disturbing side effects are less common. So far, however, there are only a few NIR fluorophores.

Near infrared image of nanosheets taken from a plant. Credit: ©University of Göttingen

The research team has now succeeded in removing extremely thin layers from grains of calcium copper silicate, also known as Egyptian blue. These nanosheets are 100,000 times thinner than a human hair and fluoresce in the NIR.

“We were able to show that even the smallest nanosheets are extremely stable, shine brightly and do not fade,” says Dr. Sebastian Kruss. “They are ideal for optical imaging.”

The scientists tested their application for microscopy in animals and plants. For example, they tracked the movement of individual nanosheets in order to visualize mechanical processes and the structure of the tissue around cell nuclei in the fruit fly.

Dr. Sebastian Kruss. Credit: ©University of Göttingen

They also integrated the nanosheets into plants and were able to recognize them without a microscope, which promises applications in the agricultural industry.

“With their commitment to state-of-the-art microscopy methods, new findings in biomedical research can be expected in the future,” says Kruss.

Scientists from the Institute for Physical Chemistry, the 3rd Physical Institute, the Institute for Developmental Biochemistry and the Institute for Geology as well as the Clinic for Dermatology, Venerology and Allergology of the University Medical Center Göttingen and the University of California Riverside were involved in the study.