Nanoparticles

• Nanoparticles are really tiny
• Particles are put into categories depending in their diameter:

  • Coarse particles (PM10) have a diameter between 2500 nm (2.5 x 10^-6 m) and 10,000 nm (1 x 10^-5). They're also called dust
  • Fine particles (PM2.5) have a dimeter between 100 nm (1 x 10^-7 m) and 2500 nm (2.5 x 10^-6 m)
  • Nanoparticles have a diameter between 1 nm (1 x 10^-9 m) and 100 nm (1 x 10^-7 m). These are particles that contain only a few hundred atoms
• 1 nm = 0.000000001 m
• A typical atom has a diameter of about 0.1 nm (1 x 10^-10 m)
• There's a whole area of science that investigates the uses and properties of nanoparticles, called nanoscience
• Nanoparticles have a large surface area to volume ratio
• The surface area to volume ratio is an important factor as it can affect the way a particle behaves
• Surface area to volume ratio = surface area / volume
• As particles decrease in size, the size of their surface area increases in relation to their volume. This causes the surface area to volume ratio to increase
• Example

  Find the surface area to volume ration for the cube A

  (Check image)

  A

  -Each face has a surface area of 100 nm x 100 nm = 10,000 nm^2 so the total surface area is 6 x 10,000 nm^2 = 60,000 nm^2

  -The volume of the cube is 100 nm x 100 nm x 100 nm = 1,000,000 nm^3

  -The surface area to volume ratio = surface area / volume = 60,000 / 1,000,000 = 0.06^-1 nm

  A) nm

  B) A

  C) B

  
• Example

  Find the surface area to volume ratio for the cube B

  (Check image)

  B

  -Each face has a surface area of 10 nm x 10 nm = 100 nm^2 so the total surface area is 6 x 100 nm^2 = 600 nm^2

  -The volume of the cube is 10 nm x 10 nm x 10 nm = 1,000 nm^3

  -The surface area to volume ratio = surface area / volume = 600 / 1,000 = 0.6^-1 nm

  
• Nanoparticles have a vey high surface area to volume ratio - this means the surface area is very big compared to the volume
• The surface area to colme ratio can cause the properties of a material to be different depending on whether it's a nanoparticle or whether it's in bulk (property of something that is great in magnitude)
• You'll often need less of a material that's made up of nanoparticles to work as an effective catalyst compared to a material made up of 'normal' sized particles (containing billions of atoms rather than a few hundred)