Optical anti-counterfeiting technology based on the multicolor emission generated by the abundant energy levels of rare earth ions shows great potential in the face of increasing information security problems worldwide. However, it is not an easy task to achieve multi-channel orthogonal emissions in a single nanoparticle with a simple structure by a convenient method. In this work, we have successfully realized the tri-channel orthogonal emissions under three excitation wavelengths in NaErF4@NaYF4:Eu3+@NaBiF4:Yb3+,Tm3+ core@shell@shell nanoparticles. In our design, the interlayer NaYF4:Eu3+ plays the role of “one arrow aiming at three eagles”. First, it can enhance the upconversion luminescence intensity of NaErF4. Next, it makes the emission color of Er3+ change from red to green by the energy transfer process between Er3+ and Eu3+. Finally, it can produce red emission under 395 nm light excitation. This selective excitation strategy enables R-G-B tri-channel orthogonal emissions in a single nanoparticle by simply changing the excitation wavelength, which is very suitable for high level optical information encryption. This work provides a simple and effective method for the design of smart luminescent materials, showing great potential for multi-level anti-counterfeiting and information security.
Shuai Zhou,Yang Wang,Po Hu,Wei Zhong,Hong Jia,Jianrong Qiu,Jiajun Fu
Orthogonal upconversion nanoparticles (UCNPs) have received increasing research attention due to their unique optical performance. However, the establishment of the orthogonal UCNPs emitting primary red/green/blue (RGB) UCL remains a great challenge. Herein, RGB-switchable NaErF 4 -cored core–multishell UCNPs (RGB-UCNPs) are constructed through the coordinative implementation of outside-in cascaded photon harvesting and interfacial energy-transfer (IET) inhibition. By modulating several constructional factors, the power-density-independent red, green, and blue luminescence in high color purity is readily available in the elaborated RGB-UCNPs under 1550, 808, and 980 nm excitations, respectively. Notably, full-color emissions, involving red, yellow, green, cyan, blue, magenta and white, are dynamically implemented in this single architecture through manipulating the excitation power of the combined 1550/808/980 nm lasers. These emission profiles of RGB-UCNPs make them promising in broad photonic applications. As a proof of concept, the viability of the logicalized information encryption strategy and smartphone APP-assisted multimodal luminescent QR code anti-counterfeiting technique is demonstrated, which are both established based on directly useable RGB-UCNPs with assistance of a self-built combined laser system. This work not only opens up a new avenue to gain RGB-switchable UCL and flexible full-color output in a single nanostructure, but also provides enlightenment for developing the application scenarios of multicolor-tunable UCNPs.
危险品化学品经营许可证（带存储）