Figure 1. Schematic representation of the formation of CSFs.

(A) The surface of the substrate is treated to create abundant silanol groups, which can be rationally controlled with the pretreatment method. (B) The quaternary ammonium groups are chemically modified on the substrate surface by co-condensation between the silanol and siloxane of TMAPS. (C) Parallel-aligned DNA molecules are arranged on the surface by electrostatic interaction between the quaternary ammonium groups of the substrate and the phosphate groups of DNA. (D) The formation of CDSFs is due to chiral DNA packing, and the CDSFs are subsequently arranged on the surface of the substrate by the self-assembly of DNA, TMAPS and TEOS in the presence of Mg²⁺. (E) The pure CSFs are obtained by calcination to remove the DNA.