Nanoparticles are tiny particles with at least one dimension between about 1 and 100 nanometers. At this scale, materials develop properties that differ greatly from their bulk form, because quantum effects and a very high surface area dominate their behavior.

Researchers classify nanoparticles by composition and structure. Metal nanoparticles, such as gold and silver, show intense colors and strong interactions with light, which are useful in sensing, imaging and catalysis. Metal oxide nanoparticles, like titanium dioxide and zinc oxide, are used in sunscreens, pigments and photocatalysts. Carbon based nanoparticles include fullerenes, carbon nanotubes and graphene derived structures, valued for their mechanical strength, electrical conductivity and chemical tunability. Polymeric nanoparticles and liposomes can encapsulate drugs or genes, protecting their cargo and controlling how it is released in the body.

A key strand of research focuses on synthesis methods that control size, shape and surface chemistry, since these features determine optical, magnetic, catalytic and biological behavior. Techniques range from physical vapor processes to chemical routes such as sol gel and microemulsions, as well as biological synthesis using microorganisms or plant extracts.

Applications span medicine, energy, environment and electronics. In medicine, nanoparticles act as contrast agents, targeted drug carriers and components of diagnostic tests. In energy, they improve solar cells, batteries and fuel cells. Environmental uses include pollution sensing and water purification.

Alongside these advances, scientists study potential risks. Because nanoparticles can move through air, water and living tissues, their toxicity, persistence and ecological impact are active areas of investigation, guiding efforts to design safer nanomaterials.