Recently, Associate Professor Yao Guangbao from the Center for Transformative Molecules, Shanghai Jiao Tong University, in collaboration with Associate Researcher Zhang Jichao from the Shanghai Synchrotron Radiation Facility, achieved damage-free conversion of colloidal crystals from solution to solid state using a nickel ion-assisted freeze-drying (NAD) technique. This breakthrough enabled the fabrication of solid-state supercrystals with hierarchical ordered structures and enhanced optical properties. The related work, titled "Nickel-Assisted Dehydration of DNA-Engineered Colloidal Crystals", was published in the Journal of the American Chemical Society (JACS).

Article abstract:

In colloidal crystal engineering, DNA has enabled precise control over crystal symmetry and architecture through programmable interparticle interactions in aqueous environments. However, practical applications typically require dry-state operation, necessitating robust strategies to transform these assemblies into free-standing solid-state metamaterials. As direct dehydration often induces structural collapse due to DNA deformation and capillary forces, the preservation of structural integrity becomes a critical challenge, particularly for large crystals with macroscopic functionality. Here, we introduce a nickel ion-assisted freeze-drying strategy that combines reversible Ni2+-DNA phosphate coordination for stress mitigation with lyophilization to reduce interfacial damage. This approach enables rapid fabrication (within 2 h) of solid-state colloidal crystals while maintaining hierarchical order from nanoscale to macroscale. Structural characterization confirms retention of crystallographic symmetry despite up to 45% lattice contraction, and surface analysis reveals multidimensional defects analogous to those in atomic crystals. Notably, this approach facilitates the fabrication of monolithic single crystals spanning tens of micrometers, featuring flat surfaces and enhanced metallic reflectivity. This work overcomes the rigidity-adaptability trade-off in existing processes, offering a scalable route to colloidal metamaterials for applications in photonic circuits and near-field optical devices.