Nanoparticle

Common nanoparticles

Usually nanoparticles are not atomically precise and thus of little use for atomically precise manufacturing.

For something to qualify as a "nanoparticle" the following criteria must be met:

it must be a pieces of matter in the solid state
it must have a size smaller than a micrometer (= 1000 nanometers)
it must not be too strongly bond to identical particles and it must not be too strongly bond to a substrate.
=> among others (e.g. high surface area makes high reactivity) easy spilling due to unbondedness is a reason why toxicity considerations are so important for nanoparticles

Often:

produced by chemical means
containing metals (e.g. gold)
crystalline (also called: "nano crystals") - otherwise they most likely get called otherwise.

Atomically precise nanoparticles may be useful for in the path to advanced productive nanosystems.

Atomically precise gold nanocrystal molecules with surface plasmon resonance [1] - by Huifeng Qian, Yan Zhu, and Rongchao Jin - Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
[Todo: Hunt for relevant work about atomically precise nanoparticles]