Why is bulk zinc oxide white and the nano form transparent?

In summary, the conversation discusses the concept of nano-form and the number of atomic layers in it. It also mentions the materials ZrO2, TiO2, and Al2O3 and how they can appear white or transparent depending on factors such as crystal structure and particle size. The conversation concludes by mentioning how these materials can act as sun blocks due to their absorption bands in the UV regime.
  • #1
#neutrino
51
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umm well that's about it
 
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  • #2
What does one mean by nano-form? How many atomic layers in the nano-form?

Think about ZrO2 or TiO2 and under what conditions they are white or transparent, or even Al2O3. Think about crystal vs amorphous vs granular/suspension.
 
  • #3
These materials are both transparent in the visible regime of light. However, because they have a higher index of refraction, the light passing through small particles is refracted and reflected off of many surfaces. The resultant scattered light makes them appear white. If the particles are smaller than the wavelength of light, they no longer interfere with its transmission and they are transparent again. They do have absorption bands in the UV regime, and still act as effective sun blocks.
 

FAQ: Why is bulk zinc oxide white and the nano form transparent?

Why is bulk zinc oxide white?

Bulk zinc oxide is white because of its unique crystal structure. The atoms in bulk zinc oxide are arranged in a way that allows them to absorb and reflect all wavelengths of light, making it appear white to the human eye.

Why is the nano form of zinc oxide transparent?

The nano form of zinc oxide is transparent because it has a different crystal structure than bulk zinc oxide. The atoms in the nano form are arranged in a way that allows them to only absorb and reflect certain wavelengths of light, making it transparent to the human eye.

How does the size of zinc oxide particles affect its color?

The size of zinc oxide particles directly affects its color. Bulk zinc oxide, with larger particles, appears white due to light being absorbed and reflected by the particle's structure. In contrast, the smaller particles in the nano form of zinc oxide only absorb certain wavelengths of light, making it transparent.

What is the significance of zinc oxide's color?

Zinc oxide's color is significant because it is a result of its unique properties and crystal structure. Understanding the difference in color between bulk zinc oxide and the nano form can help scientists and researchers utilize these properties in various applications, such as sunscreen, cosmetics, and electronics.

Can zinc oxide be manipulated to change its color?

Yes, zinc oxide can be manipulated to change its color by altering the size and shape of its particles. By controlling the particle size and shape, scientists can change the wavelengths of light that are absorbed and reflected, resulting in different colors. This manipulation can be useful in creating new materials for various applications.

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