Nanoparticulate materials
A substance that consists of nanoparticlesTiny particles which are between 1 and 100 nanometres (nm) in size. is described as being nanoparticulate materialsUseful substances containing nanoparticles..
Some properties of nanoparticulate materials are different from the properties of the same material in bulk, as powders, lumps or sheets. This difference in properties is the result of two things:
- the tiny size of nanoparticles compared to the same material in bulk
- the large surface areaThe total area of all sides on a 3D shape. to volumeThe volume of a three-dimensional shape is a measure of the amount of space or capacity it occupies, eg an average can of fizzy drink has a volume of 330 ml. ratios of nanoparticulate materials compared to the same material in bulk
Properties and uses
Nanoparticulate materials have many uses. These include:
- medical treatments
- cosmetics, deodorants and sunscreens
- electronics
- catalysts
Small sizes
Sunscreens block harmful ultraviolet lightElectromagnetic radiation with a greater frequency than visible light but less than X-rays. Humans cannot see it but it can damage eyes and skin in high doses. from the sun reaching the skin. Zinc oxide blocks ultraviolet light, so is used in sunscreens. Bulk zinc oxide is white, but nanoparticulate zinc oxide is invisible on the skin. Many people prefer nanoparticulate sunscreen for this reason.
Question
One disadvantage of nanoparticulate sunscreens is that they tend to clump together, making them difficult to apply. Suggest another disadvantage of these sunscreens.
It may be more difficult to tell where sunscreen has been applied if it is invisible on the skin.
Large surface area to volume ratios
The large surface area to volume ratios of nanoparticulate substances allows them to act as catalystA substance that changes the rate of a chemical reaction without being changed by the reaction itself.. Compared to the same substances in bulk, they may:
- catalyse reactions more efficiently
- catalyse different reactions that produce different productA substance formed in a chemical reaction.
Self-cleaning window panes have nanoparticulate coatings. These catalyse the breakdown of dirt in the presence of sunlight.
Possible risks of nanoparticles
Some people are concerned that the small size of nanoparticles makes it possible to breathe them in, or for them to pass into cells. Once inside the body, they might catalyse reactions that are harmful. toxicPoisonous. substances could bind to them because of their large surface area to volume ratios, harming health if the nanoparticles do get into the body. Modern nanoparticulate materials have only become common recently, so it is difficult for scientists to determine their risks.
Question
Silver has antibacterial properties. Nanoparticulate silver is used in some dressings for wounds. Suggest a possible hazard to the environment of silver nanoparticles.
The silver nanoparticles could harm or kill useful bacteria in the environment when these dressings are thrown away after use.