Lignin: a sustainable antiviral coating material

Transmission of viruses through contact with contaminated surfaces is an important pathway for the spread of infections. Antiviral surface coatings are useful to minimize such risks. Current state-of-the-art approaches toward antiviral surface coatings either involve metal-based materials or complex synthetic polymers. These approaches, however, even if successful, will have to face great challenges when it comes to large-scale applications and their environmental sustainability. Here, an antiviral surface coating was prepared by spin-coating lignin, a natural biomass residue of the paper production industry. We show effective inactivation of herpes simplex virus type 2 (>99% after 30 min) on a surface coating that is low-cost and environmentally sustainable. The antiviral mechanism of the lignin surface was investigated and is attributed to reactive oxygen species generated upon oxidation of lignin phenols. This mechanism does not consume the surface coating (as opposed to the release of a specific antiviral agent) and does not require regeneration. The coating is stable in ambient conditions, as demonstrated in a 6 month aging study that did not reveal any decrease in antiviral activity. This research suggests that natural compounds may be used for the development of affordable and sustainable antiviral coatings

Ductile, High-Lignin-Content Thermoset Films and Coatings

<p>Although lignin is a highly abundant and renewable polymer with very interesting properties, the preparation of high-lignin-content materials is challenging due to the brittleness and poor reactivity of lignin. Herein, high lignin content films and coatings were prepared by a simple and efficient method. A glyoxylic acid lignin (GA lignin), rich in carboxylic acid groups and hence highly reactive towards epoxy cross-linkers, was reacted with poly(ethylene glycol) diglycidyl ether and glycerol diglycidyl ether cross-linkers to achieve freestanding films containing up to 70 wt% lignin, and covalently attached surface coatings containing up to 90 wt% lignin. These films and coatings, potentially 100% biobased, show high antioxidant activity and UV barrier property, still maintaining good visible transparency. They hence are promising for application as sustainable food packaging films.</p&gt

Thermally Induced Silane Dehydrocoupling on Silicon Nanostructures

Organic trihydridosilanes can be grafted to hydrogen-terminated porous Si nanostructures with no catalyst. The reaction proceeds efficiently at 80 degrees C, and it shows little sensitivity to air or water impurities. The modified surfaces are stable to corrosive aqueous solutions and common organic solvents. Octadecylsilane H3Si(CH2)(17)CH3, and functional silanes H3Si(CH2)(11)Br, H3Si(CH2)(9)CH=CH2, and H3Si(CH2)(2)(CF2)(5)CF3 are readily grafted. When performed on a mesoporous Si wafer, the perfluoro reagent yields a superhydrophobic surface (contact angle 151 degrees). The bromo-derivative is converted to azide, amine, or alkyne functional surfaces via standard transformations, and the utility of the method is demonstrated by loading of the antibiotic ciprofloxaxin (35% by mass). When intrinsically photoluminescent porous Si films or nanoparticles are used, photoluminescence is retained in the grafted products, indicating that the chemistry does not introduce substantial nonradiative surface traps

Ductile, High-Lignin-Content Thermoset Films and Coatings

In the context of transitioning toward a more sustainable use of natural resources, the application of lignin to substitute commonly utilized petroleum-based plastics can play a key role. Although lignin is highly available at low cost and presents interesting properties, such as antioxidant and UV barrier activities, its application is limited by its low reactivity, which is a consequence of harsh conditions normally used to extract lignin from biomass. In this work, the use of glyoxylic acid lignin (GA lignin), rich in carboxylic acid groups and hence highly reactive toward epoxy cross-linkers, is presented. GA lignin, which is directly extracted from biomass via a one-step aldehyde-assisted fractionation process, allowed the preparation of thermoset films and coatings via a simple reaction with sustainable poly(ethylene glycol) diglycidyl ether and glycerol diglycidyl ether cross-linkers. This allows one to prepare freestanding films containing up to 70 wt % lignin with tunable mechanical properties and covalently surface-attached coatings containing up to 90 wt % lignin with high solvent resistance. Both films and coatings display antioxidant properties and combine excellent UV barrier activity with high visible transparency, which is attractive for applications in sustainable food packaging