A nanoparticle is a particle of matter that is between 1 and 100 nanometers in diameter. They are undetectable by the human eye and can exhibit significantly different physical and chemical properties to their larger material counterparts. Nanoparticles can be made up of only a few hundred atoms and are an important component of atmospheric pollution, as well as key ingredients in many industrialized products such as paints, plastics, metals, ceramics, and magnetic products. They are also objects of study in many sciences such as chemistry, physics, geology, and biology, as they often exhibit phenomena that are not observed at either bulk or atomic/molecular scales.

The material properties of nanoparticles change as their size approaches the atomic scale, due to the surface area to volume ratio increasing, resulting in the material’s surface atoms dominating the material performance. This feature enables nanoparticles to possess unexpected optical, physical, and chemical properties, as they are small enough to confine their electrons and produce quantum effects.

Nanoparticles are used in a variety of fields, including medicine, engineering, catalysis, and environmental remediation. In medicine, for example, nanoparticles are being developed to assist the transportation of chemotherapy drugs to cancer cells. However, nanoparticles can also pose potential health risks, as they can penetrate cells and tissues and cause damage.