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Title:Gold Nanoparticles: Size vs. Color
Author(s):Al-Qadi, Kareem; Saadah, Bara
Contributor(s):Sobh, Nahil
Raman spectroscopy
Surface Plasmon Resonance
Abstract:When subjected to electromagnetic radiation, nanoparticles are polarized due to an electric field. This electric field interacts with free electrons on the surface of the nanoparticle (surface plasmons) causing them to oscillate at certain frequencies. When the frequency of light equals the frequency of the electron cloud surrounding the cube, they resonate. These frequencies can match up with the frequencies of colors in the visible light spectrum, and absorb that color. At small sizes, such as 30nm, gold nanoparticles reflect red light, giving them a red color. At bigger sizes, such as 80nm, the gold nanoparticles absorb red light and reflect blue light, causing the nanoparticle to be blue or purple. Once the shape is big enough (>~100nm), the electron cloud will uniformly surround the entire cube, and the photons of light will not be able to penetrate the electron cloud, making the object shiny. The graph below shows the light extinction efficiency properties for these differing dimensions and how the color will, in effect also change. Our research focuses on determining the optical properties of different nanoparticle shapes and sizes and this is an example of one of them. For more information about the Image of Research--Undergraduate Edition go to:
Issue Date:2015-04
Rights Information:Copyright 2015 Kareem Al-Qadi
Copyright 2015 Bara Saadah
Date Available in IDEALS:2015-04-29

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