nanoparticles

• • coarse particles are dust
  • they have a diameter betwenn 2500nm and 10,000nm
• • fine particles have diameter between 100nm and 2500nm
• • nanoparticles contain only a few hundred atoms
  • they have a diameter between 1nm and 100nm
• • nanoparticles have a large surface area to volume ratio
  • smaller particles increase surface area
  • so, surface area to volume ratio increases
  • surfac area is large compared to volume
• • nanoparticles are used in sunscreens
  • sunscreens block ultraviolet light from the Sun reaching the skin
  • zinc oxide is used in sunscreens because it blocks ultraviolet light
  • bulk zinc oxide is white, but nanoparticulate zinc oxide is invisible on skin
• • nanoparticles in sunscreens can clump together, making them difficult to apply
  • they can make it difficult to see where sunscreen has been applied if it is invisible on skin
• • the large surface area to volume ratio makes nanoparticulate substance to be used as catalysts
  • they can catalyse more efficiently
  • they can catalyse different reactions that produce different products
• • self cleaning window panes have nanoparticulate coatings
  • they catalyse the breakdown of dirt when in sunlight
• • smaller particles are absorbed more easily
  • so, can deliver drugs to right cells in body
• • some nanoparticles can conduct electricity, so are used in electric circuits for computer chips
• • silver nanoparticles have antibacterial properties
  • they can be added to polymer fibres to make surgical masks and wound dressings
• • nanoparticles may be harmful or kill useful bacteria when washed away