I love the topic of structural colour (or color, depending on your spelling preferences) and have covered it many times and in many ways. One of the best pieces I’ve encountered about structural colour (an article by Christina Luiggi for The Scientist provided an overview of structural colour as it’s found in plants and animals) was featured in my Feb. 7, 2013 posting. If you go to my posting, you’ll find a link to Luiggi’s article which I recommend reading in its entirety if you have the time.
As for this latest nanocellulose story, a June 13, 2014 news item on Nanowerk describes University of Cambridge (UK) research into films and structural colour,
Brightly-coloured, iridescent films, made from the same wood pulp that is used to make paper, could potentially substitute traditional toxic pigments in the textile and security industries. The films use the same principle as can be seen in some of the most vivid colours in nature, resulting in colours which do not fade, even after a century.
Some of the brightest and most colourful materials in nature – such as peacock feathers, butterfly wings and opals – get their colour not from pigments, but from their internal structure alone.
Researchers from the University of Cambridge have recreated a similar structure in the lab, resulting in brightly-coloured films which could be used for textile or security applications.
A June 13, 2014 University of Cambridge news release, which originated the news item, describe the phenomenon of structural colour as it applies to cellulose materials,
In plants such as Pollia condensata, striking iridescent and metallic colours are the result of cellulose fibres arranged in spiral stacks, which reflect light at specific wavelengths. [emphasis mine]
Cellulose is made up of long chains of sugar molecules, and is the most abundant biomass material in nature. It can be found in the cells of every plant and is the main compound that gives cell walls their strength.
The news release goes on to provide a brief description of the research,
The researchers used wood pulp, the same material that is used for producing paper, as their starting material. Through manipulating the structure of the cellulose contained in the wood pulp, the researchers were able to fabricate iridescent colour films without using pigments.
To make the films, the researchers extracted cellulose nanocrystals from the wood pulp. When suspended in water, the rod-like nanocrystals spontaneously assemble into nanostructured layers that selectively reflect light of a specific colour. The colour reflected depends on the dimensions of the layers. By varying humidity conditions during the film fabrication, the researchers were able to change the reflected colour and capture the different phases of the colour formation.
Cellulose nanocrystals (CNC) are also known as nanocrystalline cellulose (NCC).
Here’s a link to and a citation for the paper,
Controlled, Bio-inspired Self-Assembly of Cellulose-Based Chiral Reflectors by Ahu Gumrah Dumanli, Gen Kamita, Jasper Landman, Hanne van der Kooij, Beverley J. Glover, Jeremy J. Baumberg, Ullrich Steiner, and Silvia Vignolini. Optical Materials Article first published online: 30 MAY 2014 DOI: 10.1002/adom.201400112
© 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
While the researchers have supplied an image of the Pollia condensata, I prefer this one, which is also featured in my Feb. 7, 2013 posting,Stunning, non?