Nano-scale Particles (WJEC GCSE Chemistry: Combined Science)

• Nanoparticles are between 1 and 100 nanometres in size and usually contain only a few hundred atoms
  • Atoms and simple molecules are around 100 times smaller than this
• The research into the production and application of nanoparticles is called nanoscience
• One of the most interesting features of nanoparticles is their very high surface area to volume ratio
  • As particles decrease in size, their surface area increases in relation to their volume
  • As the side of a cube decreases by a factor of 10, the surface area to volume ratio increases by a factor of 10
  • This is why nanoparticles may have properties different from those of the same materials in bulk
  • It may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes

Diagram showing the size of nanoparticles relative to other objects and substances

Nanoparticles are between 1 and 100 nanometres in size

Nanoparticles of Silver

• Nanoparticles of silver have antibacterial and antifungal properties
• They are able to kill microorganisms such as bacteria and viruses
  • They do this without harming humans and other organisms 
• This property allows them to be used in the following applications:
  • Sports clothing to prevent body odour 
    • Body odour is caused by bacteria on the surface of the skin so killing the bacteria using silver nanoparticles reduces body odour 
  • Cleaning surgical equipment 
    • The nanoparticles will kill the bacteria on the surface of the equipment prior to operations 
  • In fridges as an anti-bacterial coating 
    • Odours in a fridge are caused by bacteria found on the surfaces so the nanoparticles will kill these bacteria and prevent the odours 

Nanoparticles of Titanium Dioxide 

• These nanoparticles are able to reflect UV light whilst also allowing visible light to pass through 
• This property allows them to be used in the following applications:
  
  • Transparent sunscreens
    • The nanoparticles block the UV light from penetrating the skin reducing the chance of sunburn and skin cancer 
    • Due to the particles being so small, they cannot be seen on the surface of the skin 
  • Self cleaning windows 
    • The window is coated with titanium dioxide nanoparticles
    • They break down the dirt on a window surface whenever UV light from the sun shines on them 
    • They also cause water to spread out in a thin film rather than forming droplets on the surface, cleaning the window

Photo by Christian Wiediger on Unsplash

Nanoparticles of titanium dioxide are used in self-cleaning windows

Higher Tier

• Nanoparticles have widespread uses and applications that can provide an immense advance in materials technology
• The use of nanoparticles in science is in its early stages so there are still a lot of unknown factors and potential risks
• In particular, there is a lack of understanding of how they may affect health
  • E.g. Some people have expressed concern that nanoscale silver, used in deodrants, and titanium dioxide, used in sunscreens, are applied to the skin and can therefore be easily absorbed into the body
• Nanoparticles are so small that they could potentially enter living cells or enter the bloodstream through our skin
• Although there haven’t been any serious short term side effects, there could be long term side effects which we haven’t detected yet as they haven’t been in use long enough
• Even a small amount of toxicity in a particular nanoparticle would be multiplied due to the high surface area to volume ratio
• This coupled with the fact that they are not easily disposed of by the body are a cause for caution in the medical application of nanoparticles