Applied Physics

Nanoparticle Films

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Science  06 May 2005:
Vol. 308, Issue 5723, pp. 759
DOI: 10.1126/science.308.5723.759c

Anti-reflective coatings are used in ophthalmic lenses, solar cells, optical data storage, and other applications in which reflections hamper device performance. Coatings are usually applied expensively via vacuum processes, and recently developed sol-gel methods still require multiple steps, including a thermal or chemical curing stage.

Krogman et al. have developed a simple process for applying anti-reflective films by spin-coating polymer substrates with metal oxide nanoparticles. Ceria or silica particles were added to water-based solutions of a pentafunctional acrylate monomer to increase or decrease the refractive index, respectively, and were then deposited onto an acrylate substrate. In order to make thin, strong, and uniform films, the monomer solutions were doped with a second solvent to stabilize the colloidal particles and to enhance evaporation rates. By varying the concentration of nanoparticles, the authors tuned the refractive indices of the cured two-layer films and were also able to adjust the wavelength of minimum reflection. The nanoparticles hardened the films, too, making the coatings more resistant to wear. — MSL

Nanotechnology 16, S338 (2005).

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