DNA–Silica Mineralization: The Formation of Exceptional Two Dimensional-Squarep4mmSymmetry by a Structural Transformation

Abstract

DNA–silica complex (DSC) mesocrystals have been synthesized by the self-assembly of DNA as template, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) as costructure directing agent (CSDA), and tetraethyl orthosilicate (TEOS) as the silica source. A full-scale synthesis-field diagram of DSCs has been constructed, and fibrous products, two-dimensional (2D)-hexagonal p6mm, and 2D-square p4mm platelets have been obtained by varying the synthetic conditions. The rare 2D-square structure possessed an inconsistent hexagonal morphology and appeared as the dominant mesostructure. The combination of X-ray diffraction patterns, scanning electron microscopy images, and high-resolution transmission electron microscopy images provided visible evidence for the mesostructural constructions of the 2D-square symmetry that transformed from the 2D-hexagonal symmetry. The driving force for this transformation seems to be the polymerization of the silica species during synthesis, which caused a decrease in the negative charge density from the silicate network. This led to close interactions of the opposing charges along the DNA–DNA interface upon quaternary ammonium phosphate electrostatic “zippers” to facilitate the formation of the 2D-square lattice.