Polyphenols, such as tannic acid, are found in plant tissues and have a variety of chemical properties, including radical scavenging. Polyphenol-rich foods and drinks, such as green tea, are also said to have health benefits.

Phillip B. Messersmith and his colleagues at Northwestern University, USA, have come up with a new use for polyphenols: as multifunctional coatings. They observed that when green tea was left in a cup for several hours, a thin polyphenol coating was formed on the vessel. Red wine also behaved similarly. After investigating crude extracts of red wine, cacao beans, and green tea, Messersmith and his team decided to study the properties of pyrogallol and tannic acid as precursors for the deposition of coatings on substrates including gold, titanium oxide, stainless steel, and PTFE.

The polyphenol coatings were found to have a wide range of uses, including killing bacteria, resistance to fouling, and the ability to scavenge radical and nonradical reactive oxygen species (ROS). The coatings could also be used to tune the optical properties of inorganic nanoparticles.

The authors envisage that these “green” coatings derived from polyphenol-rich foods could be used in consumer, industrial, and military applications.

• Colorless Multifunctional Coatings Inspired by Polyphenols Found in Tea, Chocolate, and Wine,
  Tadas S. Sileika, Devin G. Barrett, Ran Zhang, King Hang Aaron Lau, Phillip B. Messersmith,
  Angew. Chem. Int. Ed. 2013.
  DOI: 10.1002/anie.201304922