I am using single-layer graphene oxide as a treatment for C. elegans. Studies involving this treatment use probe sonication to get the particle sizes down to 50-250 nm, as the stock solution has particle sizes at a range of 0.5-5 um. I am a high school student and have no access to such. One person has advised to use filter paper to isolate the smaller particle sizes. What would be an approximate size necessary to filter to in order for the C. elegans to be able to absorb the treatment?