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Based on the fact that SiO2 can dissolve in HF solution, three kinds of diatom frustules were treated with 1% HF solution at room temperature. Given the proper reaction times (0–2 h for the diatoms Coscinodiscus and Navicula, and 0–3 h for the diatom Melosira), the size of the pores on the frustules gradually increased and the structures of the frustules remained. While HF treatment does not affect the composition, chemical bonds, or photoluminescence signature of the diatom frustules, the treatment reduces their surface areas. This method may be beneficial to diatom studies, diatom nanotechnology, and diatom device applications that make use of diatom pores.

Diatom valves and girdle bands are useful micro–nano materials in nanotechnology and micro manufacturing. A settling method is used to extract high-purity diatom valves and girdle bands from Coscinodiscus diatomite. The average models of diatom valves and girdle bands are established. Stokes Law and hydrokinetic theories are used to analyze the settling velocity of valves and girdle bands. Based on the calculation results, settling experiments are carried out, by which clean diatom valves with purity of 80% and girdle bands with purity of 90% are obtained. This method can be applied to other particles separation problem to separate micro-particles with similar radius but different sectional area.