Answer: 1-100 nanometers
Explanation:
In terms of diameter the nanoparticles may range in between 100-2500 namometers. But the ultrafine nanoparticles are in the size range of 1 to 100 nanometers.
Their small size distinguishes them with the properties that are different from other sized particles like macroparticles and microparticles. They exhibit different colloidal, electrical, and optical properties.