Pumping‐controlled multicolor modulation of upconversion emission for dual‐mode dynamic anti‐counterfeiting
Xiaoru Dai, Ke Wang, Lei Lei, Shiqing Xu, Yao Cheng, Yuansheng Wang
Abstract
Abstract Lanthanide up‐conversion features stepwise multi‐photon processes, where the difference in photon number that is required for specific up‐conversion process usually leads to significant variance in pumping‐related processes/properties. In this work, a pumping‐controlled dual‐mode anti‐counterfeiting strategy is conceived by taking advantage of the combination of up‐conversion processes with different photon numbers. The combination of Er 3+ and Tm 3+ , which are spatially separated within a designed core/triple‐shell nano‐architecture, is taken as an example to illustrate such idea. Upon infrared excitation, the emission color of a designed pattern can be switched from red to purple by increasing the excitation power density from 5 to 11 W/cm 2 , while a bright luminescent trajectory including red, white and blue‐green color with different length is observed when rotating the pattern above 600 rpm. In addition, the relative up‐conversion emission intensities of the Er 3+ and Tm 3+ ions can be manipulated through tailoring interfacial or inner defects in the core/triple‐shell nano‐crystals, which enable an ultrahigh sensitivity for the pumping‐controlled emission color variation to be observed under excitation power well below 11 W/cm 2 .