From nanocellulose to gold
Self-assembly of mechanoplasmonic bacterial cellulose-metal nanoparticle composites

Date:
August 10, 2020
Source:
Linko"ping University
Summary:
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.



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


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

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 metre, 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," Daniel Aili explains.

The researchers can determine with high precision how many particles will attach, 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 as
it does. The second part focusses on several areas of application.

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 colour. As the pressure increases, the material eventually appears to
be gold.

"We saw that the material changed colour when we picked it up in tweezers,
and at first we couldn't understand why," says Daniel Aili.

The scientists have named the phenomenon "the mechanoplasmonic effect,"
and it has turned out to be very useful. A closely related application is
in sensors, since it is possible to read the sensor with the naked eye. An example: If a protein sticks to the material, it no longer changes colour
when placed under pressure. If the protein is a marker for a particular disease, the failure to change colour can be used in diagnosis. If the
material changes colour, the marker protein is not present.

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.

"Our method makes it possible to manufacture composites of nanocellulose
and metal nanoparticles that are soft and biocompatible materials for
optical, catalytic, electrical and biomedical applications. Since the
material is self- assembling, we can produce complex materials with
completely new well-defined properties," Daniel Aili concludes.


========================================================================== Story Source: Materials provided by Linko"ping_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Olof Eskilson, Stefan B. Lindstro"m, Borja Sepulveda, Mohammad M.

Shahjamali, Pau Gu"ell‐Grau, Petter Sivle'r, Maarten Skog,
Christopher Aronsson, Emma M. Bjo"rk, Niklas Nyberg, Hazem Khalaf,
Torbjo"rn Bengtsson, Jeemol James, Marica B. Ericson, Erik
Martinsson, Robert Selegaard, Daniel Aili. Self‐Assembly
of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle
Composites. Advanced Functional Materials, 2020; 2004766 DOI:
10.1002/adfm.202004766 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200810103231.htm

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