Bio-enabled, surface-mediated approach produces nanoparticle ...( Using thin films of silk as template...)

Using thin films of silk as templates, researchers have incorporated inorganic nanoparticles that join with the silk to form strong and flexible composite structures that have unusual optical and mechanical properties. This bio-enabled, surface-mediated formation approach mimics the growth and assembly processes of natural materials, taking advantage of the ability of biomolecules to chemically reduce metal ions to produce nanoparticles without harsh processing conditions.

Less than 100 nanometers thick, silk-silver nanoparticle composite films formed in this process can be used for flexible mirrors and films that reflect light in specific wavelengths. The technique could also be used to create anti-microbial films, thin film sensors, self-cleaning coatings, catalytic materials and potentially even flexible photovoltaic cells.

"We are taking advantage of biological molecules that have the ability to bind metallic ions of silver or gold from solution," said Vladimir Tsukruk, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. "These molecules can create mono-dispersed metallic nanoparticles of consistent sizes under ambient conditions at room temperature and in a water-based environment without high vacuum or high temperatures.

Sponsored by the Air Force Office for Scientific Research and the Air Force Research Laboratory, the research is scheduled to be described August 19th at the Fall 2009 National Meeting of the American Chemical Society in Washington, D.C.

The nanoparticles produced range in size from four to six nanometers in diameter, surrounded by a biological shell of between one and two nanometers. The silk template permits good control of the nanoparticle placement, creating a composite with equally dispersed particles that remain separate. The optical properties of the resulting film depend on the nanoparticle material and size.

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