Mingyu Kwak Nanoparticles are very small and membrane filters are often not suitable for separating dispersion media. Therefore, centrifugation is used for separation. This technology makes it easier to rinse the nanoparticles.

Centrifugation is required for extraction of the NPs from the solution, and adding ethanol is commonly used to rinse or purify the NPs. But it is not mandatory to use ethanol. If you think that using ethanol can harm the property of your NPs, then no need to use.

Rajesh Dev Sarkar In my experiment, Ga NPs maybe coated with oleic acid before centrifuge the solution. Then ethanol rinse the oleic acid? And solution separated with 2 layer when inject ethanol to the solution.(Toluene, Octadecene) before centrifuge. Doesn't it matter for centrifuging?

As because the centrifuge bulk parts of the particle(size greater than 100 nm) will be settled down and nanoparticles(particle size less than 100 nm) will stay as a suspension into the solution, then by heating the solution we will be able to obtain fine nanoparticles.