How are nanoparticles defined in terms of their size?

Nanoparticles are defined as structures that typically range in size from 1 nanometer (nm) to 100 nanometers. This specific range is significant because it encompasses particles that have unique physical and chemical properties compared to larger particles or bulk materials.

At the nanoscale, materials often exhibit different behaviors due to the high surface area to volume ratio, allowing them to have enhanced reactivity, strength, and electrical properties. For instance, nanoparticles can be utilized in various applications such as catalysts, drug delivery systems, and materials science because of these distinct characteristics.

The other size ranges presented do not fit the conventional definition of nanoparticles, as they extend beyond the upper limit of 100 nm or start from a size that does not meet the lower threshold of 1 nm. Thus, the answer aligns precisely with the established scientific understanding of nanoparticles in terms of their dimensional parameters.