Dual-Mode Luminescent Lanthanide-Modified Silicon Quantum Dots for Anticounterfeiting and Latent Fingerprint Visualization

The increasingly sophisticated counterfeiting technology has led to a significant increase in the demand for more advanced anticounterfeiting materials, and multimode luminescent materials are a promising candidate in anticounterfeiting. In this research, a dual-mode luminescent nanocomposite, SiQDs-Ln, was designed and prepared by grafting lanthanide ions (Eu3+/Tb3+) onto the surface of trimellitic anhydride-functionalized blue-emitting silicon quantum dots (SiQDs). This preparation strategy can effectively prevent the aggregation of SiQDs and endow the nanocomposite with dual-mode optical response properties. It emitted visible light of different colors at the excitation wavelength of common dual-wavelength ultraviolet lamps (254 or 365 nm). The incorporation of SiQDs-Ln into commercial white industrial ink facilitated a luminescent anticounterfeiting ink, which was effectively applied to coded patterns, ASCII encryption, screen-printed designs, and QR codes. Furthermore, the fingerprint images coated with SiQDs-Ln powder demonstrated that the fingerprint with three levels of detail could be clearly recognized by the naked eye. Compared with traditional single-mode luminescent materials, SiQDs-Ln with dual-mode luminescence has greatly enhanced the level of information security as well as the accuracy and reliability of fingerprint recognition. This study indicates that the SiQDs-Ln can be conveniently used in practical applications with the aid of common hand-held dual-wavelength UV lamps and has great potential in anticounterfeiting, information encryption, and fingerprint recognition.