Efficient dual-mode luminescence from lanthanide-doped core–shell nanoarchitecture for anti-counterfeiting applications
Bang Dong, Yongjun Yuan, Mingye Ding, Wangfeng Bai, Shiting Wu, Zhenguo Ji
Abstract
Abstract Fluorescent anti-counterfeiting technique is generally based on the development of luminescent materials, which generally exhibit single-mode emissions under single-wavelength excitation, thus resulting in a poor anti-fake effect. To improve the anti-forgery performance of fluorescent anti-counterfeiting approaches, dual-mode luminescent nanoparticles with the form of a β-NaGdF 4 :Yb/Ho/Ce@β-NaYF 4 :Tb/Eu core–shell structure have been skillfully designed and synthesized by a co-precipitation strategy. Through the cross-relaxation process between Ce 3+ and Ho 3+ ions in the inner core region, the up-conversion luminescence colors of the as-synthesized samples can be turned from green to yellow and finally to red when adjusting the dopant concentration of Ce 3+ in the core. By selecting Ce 3+ as the sensitizer for harvesting the energy of incident ultraviolet (UV) light and introducing Gd 3+ as the ideal intermediate for subsequent energy migration, the down-converting emission colors of the as-obtained samples are also regulated from green to red via a Gd 3+ -assisted interface energy transfer processes (Ce 3+ → Gd 3+ → Tb 3+ , Ce 3+ → Gd 3+ → Tb 3+ → Eu 3+ ). Consequently, dual-mode luminescence with multi-color outputs can be achieved in the pre-designed core–shell nanostructure under the excitation of a 980 nm near-infrared laser and 254 nm UV light. The designed nanoarchitecture with bright dual-mode emissions and tunable colors greatly improves the ability of modern anti-counterfeiting, demonstrating its promising applications in anti-fake and optical multiplexing.