Researchers are using nanocellulose to create materials with new properties

When nanocellulose is combined with different types of metal nanoparticles, materials are formed with many new and exciting properties. They can be antibacterial, change color under pressure, or convert light to heat.

“To put it simply, we make gold from nanocellulose,” says Daniel Aili, associate professor in the Department of Biophysics and Bioengineering at the Department of Physics, Chemistry and Biology at Linköping University.

The research group, led by Daniel Aili, used a biosynthetic nanocellulose, produced by bacteria and originally developed for wound care. The scientists subsequently decorated the cellulose with metal nanoparticles, mainly silver and gold. The particles, not larger than a few billionths of a meter, are first adapted to give them the desired properties, and then combined with the nanocellulose.

“Nanocellulose consists of thin strands of cellulose, about a thousandth of a diameter of a human hair. The strands act as a three-dimensional scaffold for the metal particles. When the particles adhere to the cellulose, a material consisting of a network of particles and cellulose forms, ”explains Daniel Aili.

The researchers can determine with high precision how many particles will hook, and their identities. They can also mix particles of different metals and with different shapes – spherical, elliptical and triangular.

In the first part of a scientific article published in Advanced functional materials, the group describes the process and explains why it works the way it does. The second part focuses on different areas of application.

One exciting phenomenon is the way in which the properties of the material change when pressure is applied. Optical phenomena arise as the particles approach and interact, and the material changes color. As the pressure increases, the material eventually turns out to be gold.

“We saw that the material changed color when we picked it up in tweezers, and we could not understand at first why,” says Daniel Aili.

The scientists called the phenomenon “the mechanoplasmic effect”, and it turned out that it was very useful. A closely related application exists in sensors because it is possible to read the sensor with the naked eye. An example: When a protein adheres to the material, it does not change color when it is pressurized. If the protein is a marker for a particular disease, color change failure can be used in diagnosis. If the material changes color, the marker protein is not present.

Another interesting phenomenon is represented by a variant of the material that absorbs light from a much wider spectrum of visible light and generates heat. This feature can be used for both energy-applied applications and in medicine.

“Our method makes it possible to produce composites of nanocellulose and metal nanoparticles which are soft and biocompatible materials for optical, catalytic, electrical and biomedical applications. Since the material itself is assembled, we can produce complex materials with completely new goods defined properties, ”concludes Daniel Aili.