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10 September 2007 Prism coupler and microscopic investigations of DNA films
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Proceedings Volume 6646, Nanobiotronics; 664607 (2007)
Event: NanoScience + Engineering, 2007, San Diego, California, United States
DNA is a polyelectrolyte capable of forming thin films with interesting optical properties. We investigated refractive indices and optical anisotropy of films of the native, sodium ion-based DNA (Na-DNA) and DNA bearing the cetyltrimethylammonium ion (DNA-CTMA) using a prism coupler technique. The light polarization direction was either parallel (nTE) or perpendicular to the surface plane of the films (nTM). The index values and the birefringence of DNA films vary considerably depending on the type of the counter-ion, the film fabrication method and the relative humidity (RH) of the environment. A high negative birefringence in films of Na-DNA, nTE-nTM = -0.03 at an RH ~ 55 %, was measured in solution-cast films, indicating that the optically anisotropic DNA molecules are aligned in the plane parallel to the film surface. Refractive indices of DNA-CTMA thin films were smaller and more isotropic than those for films of Na-DNA polymer. The prism coupler reflectance curves showed a hysteresis of the index values when the RH of a DNA-CTMA film environment varied. Polarization microscopy studies showed liquid-crystalline textures at the edges of Na-DNA and DNA-CTMA films.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Anna Samoc, Zbigniew Galewski, Marek Samoc, and James G. Grote "Prism coupler and microscopic investigations of DNA films", Proc. SPIE 6646, Nanobiotronics, 664607 (10 September 2007);

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