Nanoparticles

• Nanoscience refers to structures that are 1–100 nm in size, only containing a few hundred atoms
• Fine particles (PM $_{2.5}$ ) have diameters between 100 and 2500 nm (1 x 10 $^{-7}$m and 2.5 x 10 $^{-6}$ m)
• Coarse particles (PM $_{10}$ ) have diameters between 2500nm (2.5 x 10 $^{-6}$ m) and 10000 nm (1 x 10 $^{-5}$ m)
• Coarse particles are often referred to as dust
• As the side of cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10
• Nanoparticles may have properties different from those for the same materials in bulk because of their high surface area to volume ratio
• Smaller quantities of nanoparticles are needed to be effective than for materials with normal particle sizes
• Nanoparticles have many applications in medicine, in electronics, in cosmetics and sun creams, as deodorants, and as catalysts
• New applications for nanoparticulate materials are an important area of research
• The long term impacts of nanoparticles are not known yet