Nanoparticles are defined as particles with at least one dimension between 1 and 100 nanometers (nm). To put this in perspective:
- 1 nanometer = 0.000000001 meters (one billionth of a meter)
- Size comparison: A human hair is approximately 80,000-100,000 nm wide, meaning you could line up 1,000 nanoparticles across the width of a single hair
- Molecular scale: Nanoparticles are roughly 1,000 times smaller than the width of a human red blood cell
- Atomic scale: A typical nanoparticle contains thousands to millions of individual atoms
Within the 1-100 nm range, nanoparticle properties can vary dramatically. For example:
- Small nanoparticles (1-10 nm): Often exhibit quantum effects and extremely high reactivity
- Medium nanoparticles (10-50 nm): Commonly used in medical applications and catalysis
- Large nanoparticles (50-100 nm): Frequently employed in coatings and composite materials
The precise size control during synthesis is critical because even small variations can significantly impact material properties and performance. Advanced manufacturing techniques like continuous flow reactors enable unprecedented control over nanoparticle size distribution.