Author Archives: Joseph Bergvinson

Turning Biofuel Waste Into Valuable Platform Chemicals

Posted on November 12, 2017 | Leave a comment

Scientists have recently demonstrated a faster and more efficient way of turning biofuel waste into highly valuable chemicals. These findings could have a significant impact on the economics of making fuels and other products from renewable sources.

Lignin is a component of an abundant dry plant matter called lignocellulosic biomass. This biomass source makes up the cell walls of plants and enables the upwards transport of water and provides protection against environmental stress and microbial attacks. Due to the rigidness of its structure, lignin is difficult to break down. Scientists have been trying to find methods for extracting its valuable compounds for decades, as these compounds could subsidize biofuel production, making the cost of biofuel a more competitive alternative to petroleum.

Lignin Structure. Source: Wikimedia Commons

Seema Singh and a group of researchers from Sandia National Laboratories recently studied the metabolic pathway of a soil bacteria that can naturally break down lignin. They used this metabolic pathway to come up with a method of extracting lignin’s valuable platform chemicals. The method involved genetically engineering a tobacco plant to produce large amounts of an intermediate compound called protocatechuate (PCA) as it grew. This compound was then extracted from the plant without the need to break down the lignin. Next, an engineered E. coli was added to convert the PCA into muconic acid with a yield 34% greater than previous conversion methods.

Muconic acid and pyrogallol, another product obtained using this method, are platform chemicals that are currently only derived from petroleum, and together, have a combined market value of $255.7 billion. Muconic acid can be turned into plastics, nylon, resins, and lubricants; and pyragallol has applications in cancer treatment drugs.

Nylon 6,6. Source: Wikimedia Commons

The next challenge in this field will be to maximize the yield and rate of production of these chemicals. In order for this method to be used on an industrial scale, large amounts of muconic acid and pyragallol must be produced in a short amount of time to compete with the current petroleum derived methods.

– Joseph Bergvinsom

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New Bioinspired Polymer

Posted on October 28, 2017 | Leave a comment

Materials chemists have designed a polymer that is both stretchy and strong. This polymer could lead to a new family of biomaterials which are able to heal themselves upon sustaining damage, along with being able to disparate materials such as metals and wood.

Linear Polymers – Taken by Yurko – Own work, CC BY-SA 3.0, Wikimedia Creative Commons

The most common approach to polymer synthesis is to covalently link monomers – the building blocks of polymers – together into long chains. These polymers are typically stiff and not too strong. Another approach involves ionically linking charged polymer chains together to create loosely-linked, flexible materials. Due to the electrostatic interactions between these polymers, they will reattach or “heal” upon separation.

Saltwater mussels naturally create polymers using a combination of these two methods, which result in polymers with both covalent and ionic bonds. Scientists have been trying to synthetically replicate these polymers by adding negatively charged groups called catechols to a gel containing covalently linked polymers. Upon adding positively charged iron atoms to a solution of this, the catechols, located on the polymer strands form ionic bonds with them. This results in strong polymers which are able to heal themselves. The problem with this method is that the salt water in which the reaction takes place causes the gel to expand, thus limiting the stretching ability of the resulting polymer.

Saltwater Mussels – Taken by Mark A. Wilson (Department of Geology, The College of Wooster). Public Domain

Valentine and a team of researchers were able to adapt this strategy to work in a dry environment. They added catechol groups to a gel containing covalently linked polyethylene glycol (PEG) polymers. Capping reagents were added to the catechols during the reaction to prevent their reaction with oxygen in the air or water. Before spritzing in iron, these capping groups were removed with acid. The iron atoms diffused through the PEG to react with the catechols to form additional linkage. The resulting polymer was found to be 100 to 1000 times stiffer than the polyethylene glycol, yet very flexible.

Given that this new polymer forms materials that can withstand forces that would rupture normal PEG-based materials, it might lead to a new family of biomaterials which are able to heal themselves upon sustaining damage and could be used in artificial tendons or joints for prosthetics to help minimize wear and tear.

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New Advances in Structural Colouration (revised)

Posted on October 15, 2017 | Leave a comment

There are countless examples of colouration via nanoscale texturing found in nature, such as in bird feathers and butterfly wings (shown in video below). To date, we have been primarily reliant on chemical pigmentation for colour production since many traditional structural colours have either been iridescent or have lacked sufficient colour saturation. If these shortcomings can be worked out, structural colours will be a superior alternative to pigmentary colours, and will therefore be of greater use in areas of communication, signaling, and security. Developing a technique that would allow us to generate a wide range of structural colours has proven to be a difficult task.

Structural colours are produced by the scattering of light off nanoparticles, whereas pigmentary colours are produced through the absorption of light by molecules. The reason scientists are interested in structural colours is because they are tunable, less dependent on the use of toxic organic and metal-based materials, and have proven to be more resistant to photo and chemical bleaching compared to pigmentary colours. In a recent study conducted by Dr. Xiao and a team of researchers, tiny balls of melanin were aggregated into clusters called ‘supraballs’. Individual nanoparticles of melanin are responsible for skin pigmentation and appear black, however, altering the spacing of the nanoparticles in the supraballs affects how light is scattered, thus generating a spectrum of structural colours.

Synthesis and Self-Assembly. Taken from: Science Advances

Altering the spacing of the nanoparticles was achieved by adding a thin silica shell to the surface of the nanoparticles to control how tightly packed they were. By varying the diameter of the silica coating, the nanoparticles formed differently nanostructured supraballs which were able to scatter light to produce a wide range of colours. Additionally, using nanoparticles of different dimensions allowed for the shading of colours to be altered. Melanin was chosen as the nanoparticle core due to its large refractive index (RI) and broadband absorption in the visible range, which reduces the scattering of incoherent light and subsequently increases colour purity. The high RI melanin core and low RI silica shell makes for higher reflectance and brighter, more vibrant colours.

Microstructures of supraballs. Taken from: Science Advances

One of the main reasons this finding is considered a breakthrough in structural colouration research is due to the simplicity of the technique used to create the supraballs. This technique contrasts previously known methods, which are far more complicated and do not have the same potential for commercial application. The silica-coated melanin nanoparticles self-assemble into supraballs clusters via a water-in-oil reverse emulsion process. The supraballs are then separated by centrifugation. This process does not rely on the use any surfactant molecules to stabilize the emulsion and is fast and easily scalable.

With all the benefits structural colours have over pigmentary colours, along with recent advances in techniques used to create the nanomaterials which generate these structural colours, it is only a matter of time before we see this technology become incorporated in a wide range of applications involving sensors, display devices, and tunable organic lasers.

– Joseph Bergvinson

 

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New Advances in Structural Colouration

Posted on September 24, 2017 | Leave a comment

There are countless examples of colouration via nanoscale texturing found in nature and it seems like a superior alternative to chemical pigmentation, however, developing a technique that would allow us to generate a wide range of structural colours has proven to be a difficult task.

Structural colours are produced by the scattering of light off nanoparticles, whereas pigmentary colours are produced through the absorption of light by molecules. The reason scientists are interested in structural colours is because they are less dependent on the use of toxic organic and metal-based materials and have proven to be more resistant to photo and chemical bleaching compared to pigmentary colours. In a recent study conducted by Dr. Xiao and a team of researchers, tiny balls of melanin were aggregated into clusters called ‘supraballs’. Individual nanoparticles of melanin are responsible for skin pigmentation and appear black, however, altering the spacing of the nanoparticles in the supraballs affects how light is scattered, thus generating a spectrum of structural colours.

Microstructures of supraballs – http://advances.sciencemag.org/content/3/9/e1701151.full

Altering the spacing of the nanoparticles was achieved by adding a thin silica shell to the surface of the nanoparticles to control how tightly packed they were. By varying the diameter of the silica coating, the nanoparticles formed differently nanostructured supraballs which were able to scatter light to produce a wide range of colours. Additionally, using nanoparticles of different dimensions allowed for the shading of colours to be altered. Melanin was chosen as the nanoparticle core due to its large refractive index (RI) and broadband absorption in the visible range, which reduces the scattering of incoherent light and subsequently increases colour purity. The high RI melanin core and low RI silica shell makes for higher reflectance and brighter, more vibrant colours.

One of the main reasons this finding is considered a breakthrough in structural colouration research is due to the simplicity of the technique used to create the supraballs. This technique contrasts previously known methods, which are far more complicated and do not have the same potential for commercial application. The silica-coated melanin nanoparticles self-assemble into supraballs clusters via a water-in-oil reverse emulsion process. The supraballs are then separated by centrifugation. This process does not rely on the use any surfactant molecules to stabilize the emulsion and is fast and easily scalable.

With all the benefits structural colours have over pigmentary colours, along with recent advances in techniques used to create the nanomaterials which generate these structural colours, it is only a matter of time before we see this technology go to market.

– Joseph Bergvinson

Citations:

Hamers, L. (2017, September). Tiny ‘supraballs’ put a new spin on creating long-lasting color. Science News. Retrieved from https://www.sciencenews.org/article/tiny-supraballs-put-new-spin-creating-long-lasting-color

Xiao, M., Hu, Z., Wang, Z., Li, Y., Tormo, A. D., Le, T. N., Wang, B., Gianneschi, N. C., Shawkey, M. D., Dhinojwala, A. (2017). Bioinspired Bright Nonirridescent Photonic Melanin Supraballs. Journal of Science Advances, 3(9). doi: 10.1126/sciadv.1701151

 

 

 

 

 

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