"Colloids (also known as colloidal solutions or colloidal systems) are mixtures in which microscopically dispersed insoluble particles of one substance are suspended in another substance. The size of the suspended particles in a colloid can range from 1 to 1000 nanometres (10-9 metres)"
https://byjus.com/jee/colloids/
"Colloidal metals are very fine dispersions of particles of noble metals such as gold, copper, silver, zinc, platinum and iron, within a liquid medium such as the highly purified bi-distilled water."
https://aloevonderweid.com/en/production-2/colloids/
"Colloidal copper is a popular health supplement. It’s similar to colloidal silver, which is also widely used for wellness and medical purposes.
To make colloidal copper supplements, microscopic molecules of copper are suspended in purified water. When purchased, it comes in a liquid, extract-like form that can be taken orally. It may also be used in other products."
https://www.healthline.com/health/colloidal-copper
"Metal nanoparticles are submicron scale entities made of pure metals (e.g., gold, platinum, silver, titanium, zinc, cerium, iron, and thallium)"
https://www.sciencedirect.com/topics/materials-science/metal-nanoparticles
"Metal Nanopowders which tend to agglomerate to larger grains"
https://www.researchgate.net/post/What-are-the-differences-between-Metal-Nanoparticles-and-Metal-Nanopowder-Is-there-any-similarities-in-their-application-and-functions