Single Diamond Structured Titania Scaffold

Abstract

Single diamond (SD) network, discovered in beetles and weevils skeletons, is the holy grail in photonic materials with widest complete bandgap to date. Such structure influences the propagation of electromagnetic waves in defined frequency and is significant in photonic crystals, light-harvesting applications, optical waveguides, laser resonators, etc. However, efforts until now have not allowed a start-to-finish understanding on the production process of the unbalanced single network scaffold in natural organisms and the thermodynamical instability of SD makes it extremely difficult to be obtained by self-assembly compared to the energetically favored bicontinuous double diamond and other easily formed lattices, thus the artificial fabrication of such photonic structure in practical synthesis has last-long as a formidable challenge. Herein, we report the unprecedented bottom-up fabrication of SD titania scaffold through a one-pot co-folding scenario employing a simple diblock copolymer poly(ethylene oxide)-block-polystyrene (PEO45-b-PS241) as template and titanium diisopropoxide bis(acetylacetonate) as inorganic precursor in a mixed solvent, in which the inorganic species selectively organized in one of the skeleton enclosed by diamond minimal surface of the polymer matrix in a simultaneous assembling process. Electron crystallography investigations exhibited the tetrahedral-connected SD frameworks with space group Fd-3m in polycrystalline anatase form. Photonic bandgap calculation shows that the structure reveals a complete bandgap of 11.54 % with the dielectric contrast of titania (6.25). This work provides a straightforward solution to the complex synthesis puzzle and offers a new reference for biological relevant materials, next-generation optical devices, etc