Stress-induced self-assembly of hierarchically twisted stripe arrays

Hierarchical organization is prevalent in nature, yet the artificial construction of hierarchical materials featuring asymmetric structures remains a big challenge. Herein, we report a stress-induced self-assembly strategy for the synthesis of hierarchically twisted stripe arrays (HTSAs) with mesoporous structures. A soft and thin mesostructured film assembled by micelles and TiO₂ oligomers is the prerequisite. Then, the external stress coming from the exfoliation process triggers the deformation of this mesostructured film into hierarchically twisted structures. The stripe width and twist degree can be well manipulated by adjusting the cross-linking degree and thickness of the mesostructured films. Furthermore, this strategy is facile and versatile to synthesize HTSAs with diverse components, including carbon, Al₂O₃ and ZrO₂. We find that mesoporous TiO₂ HTSAs can serve as an ideal integrator for adsorption-enrichment-detection process, exhibiting a rapid and high adsorption capacity towards molecules at low concentrations and enabling the subsequent surface-enhanced Raman scattering (SERS) detection. Such twisted stripe arrays achieve 2.3-fold and 5.6-fold enhancements in SERS compared with flat surfaces and solution conditions, respectively, due to the increased Raman scattering among the hierarchical, twisted, and mesoporous structures.