Morphological Engineering of MOFs Through Carbon Dot Doping: Enabling Fluorescent Anticounterfeiting on Human Skin

There is a growing demand for cost-effective, environmentally friendly fluorescent inks that exhibit excellent writing performance and dual anticounterfeiting features, particularly for use on human skin. This study introduces an innovative method that combines nontoxic carbon dots (CDs) with MIL-53(Al)-NH₂, a metal–organic framework (MOF). By varying the content of CDs, the morphology of MIL-53(Al)-NH₂ was controlled through two mechanisms: nucleation promotion and competitive coordination. This manipulation resulted in a change from gear-like to needle-like structures, which significantly enhanced fluorescence intensity and induced a red shift, especially under different pH conditions. The fluorescent ink produced patterns that remain invisible in daylight but shift from yellow to blue under ultraviolet light as they dry, with this effect being repeatable. These distinctive characteristics underscore the potential of this fluorescent ink for advanced applications in information encryption and anticounterfeiting.