Lin Liu,Shanshan Peng,Peng Lin,Ruoping Wang,Hongyun Zhong,Xia Sun,Liang Song,Junpeng Shi,Yun Zhang
Diverse phosphors have received widespread attention because of their ability to provide enhanced information security. However, these phosphors usually emit in the visible region and the emissions are discernible with human eyes, which, along with the single luminescence mode and reading manner, adversely affects the information security. This work exhibits a novel series of optical nanomaterials, Mg8Lu2Ge6O23:Bi3+/Yb3+/Ln (MLGB–Yb/Ln, Ln = Tm3+, Ho3+, and Er3+), with multi-mode luminescence and dual-mode reading characteristics and their suitability for information encryption is demonstrated. MLGB–Yb/Ln displays visible down-conversion luminescence, visible up-conversion luminescence (UCL), and invisible ultraviolet-B (UVB) persistent luminescence (PersL). The visible luminescence is directly detectable by human eyes (visible reading method); however, because the invisible UVB PersL cannot be perceived by human eyes, it can be used for information encryption. Interestingly, the encrypted information can be read by a charge-coupled device camera to decode the optical information (invisible reading method). More importantly, the unique optical properties ensure that MLGB–Yb/Ln behaves similarly to common UCL materials when viewed by humans, which further enhances the level of information encryption provided by invisible UVB PersL. Based on MLGB–Yb/Ln, we designed deceptive information encryption patterns to show the advantage of using these materials for information encryption.
Jun Zhang,Kai Wu,Xiaoqing Gao,Min Zhang,Xin Zhou,Florian Bertram,Chen Shen,Yunlong Zhou
Chiral structures and functions are essential natural components in biominerals and biological crystals. Chiral molecules direct inorganics through chiral growth of facets or screw dislocation of crystal clusters. As chirality promoters, they initiate an asymmetric hierarchical self-assembly in a quasi-thermodynamic steady state. However, achieving chiral assembly requires a delicate balance between intricate interactions. This complexity causes the roles of achiral-chiral and inorganic components in crystallization to remain ambiguous. Here, we elucidate a definitive mechanism using an achiral-chiral ligand strategy to assemble inorganics into hierarchical, self-organized superstructures. Achiral ligands cluster inorganic building blocks, while chiral ligands impart chiral rotation. Achiral and chiral ligands can flexibly modulate the chirality of superstructures by fully using their competition in coordination chemistry. This dual-ligand strategy offers a versatile framework for engineering chiroptical nanomaterials tailored to optical devices and metamaterials with optical activities across a broad wavelength range, with applications in imaging, detection, catalysis, and sensing.
Developing efficient protocols to enhance the optical activities of chiral self-assemblies is a key to realizing their chiroptical functions such as chiral sensing and displays. Here, we have reported a coassembly protocol to efficiently boost the chiroptical responses, whereby the synthesis of chiroptical nanomaterials and highly accurate detection of enantiomeric excess (ee %) were achieved. A series of benzimidazole derivatives with different topologies underwent spontaneous aggregation and symmetry breaking in solution, generating silent Cotton effects, yet exclusive weak left-handed circularly polarized luminescence (CPL). The coassembly with natural hydroxyl acids via complementary H bonds afforded chiral nanostructures with emerged Cotton effects and enhanced CPL. Dissymmetry g-factors were dramatically boosted (glum from 1 × 10–3 to 5.5 × 10–2, gabs from 0 to 6.7 × 10–3). In addition, proof of concept of recognition and detection of natural chiral molecules was realized with high accuracy.
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