Nanoparticles are ultrafine particles with at least one dimension measuring between 1 and 100 nanometers (nm). At this scale, materials exhibit unique physical, chemical, and biological properties that differ significantly from their bulk counterparts. These distinctive characteristics arise from the high surface-area-to-volume ratio and quantum effects that become prominent at the nanoscale.
Nanoparticles can be composed of various materials including metals (gold, silver, zinc oxide), metal oxides (titanium dioxide, iron oxide), semiconductors (quantum dots), polymers, lipids, and carbon-based structures. The specific properties of nanoparticles, such as optical behaviour, electrical conductivity, mechanical strength, and reactivity can be precisely tuned by controlling their size, shape, composition, and surface chemistry during synthesis.