pressure sensitive nano particel ***

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

The research group, led by Daniel Aili, has used a biosynthetic nanocellulose produced by bacteria and originally developed for wound care. The scientists have subsequently decorated the cellulose with metal nanoparticles, principally silver and gold. The particles, no larger than a few billionths of a meter, are first tailored to give them the properties desired, and then combined with the nanocellulose.

"Nanocellulose consists of thin threads of cellulose, with a diameter approximately one thousandth of the diameter of a human hair. The threads act as a three-dimensional scaffold for the metal particles. When the particles attach themselves to the cellulose, a material that consists of a network of particles and cellulose forms,"

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

"We saw that the material changed color when we picked it up in tweezers, and at first we couldn't understand why,"

An example: If a protein sticks to the material, it no longer changes color when placed under pressure. If the protein is a marker for a particular disease, the failure to change color can be used in diagnosis.

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

 

 

 

pressure를 가했을 때 raman shift가 일어나 색깔이 변한다고 한다. 

그리고 결합을 했을 때에는 raman shift가 일어나지 않는다고 한다. 

 

reference

Olof Eskilson et al. Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites, Advanced Functional Materials (2020). DOI: 10.1002/adfm.202004766