The rampant appearance of counterfeiting has a serious adverse effect on every aspect in the global markets. Thus, the development of high‐tech security strategies has become an urgent challenge. Recently, lanthanide ions (Ln3+) doped materials open new avenues for concealing factual data and shield against counterfeiting because of their unique optical characteristics of color‐tunable emissions under near‐infrared excitation. The present review surveys the recent advances in Ln3+‐doped upconversion crystals (UCCs) as fluorescent functional inks toward designable and high‐level anti‐counterfeiting patterns and graphical encoding. The great achievements of fabrication of versatile security patterns can be ascribed to the combination of the single or multiple colorful UCCs with polymers, additives, and solvents. Moreover, the crucial factors including underlying mechanisms, synthetic methods of upconversion fluorescence materials, and the diverse printing technologies employed for patterning the fluorescence images have been highlighted, and the corresponding challenges and opportunities in this promising research area are presented. This review will help providing a fundamental understanding and guidance to rational design fluorescence optical labels based on Ln3+‐doped UCCs for broadening their applications in high‐level security fields.

The three-dimension (3D) flower-like α-Fe 2 O 3 @TiO 2 core-shell nanocrystals with thorhombic, cubic and discal morphologies are synthesized for photocatalytic application. α-Fe 2 O 3 nanocrystals were prepared via Cu 2+ , Zn 2+ and Al 3+ ions-mediated hydrothermal route. The α-Fe 2 O 3 @TiO 2 core-shell nanocrystals are obtained via hydrothermal and annealing process. The shape-dependent photocatalytic activity of these as-obtained α-Fe 2 O 3 @TiO 2 core-shell nanocrystals are measured. The results reveal that the discal α-Fe 2 O 3 @TiO 2 nanocrystals exhibit the best photocatalytic activity than other two core-shell nanocrystals. Because the discal α-Fe 2 O 3 nanocrystals possess more rough surface and surface defects. The fast interfacial charge transfer process and the wide spectral response could be the driving force for the enhanced photocatalytic performance. These core-shell architectures provide a positive example for synthesis of novel composite nanomaterial.

A printed invisible QR code pattern could be identified with green and blue colors under 980 nm and 365 nm light excitation, respectively.