Nanohybrids with switchable multicolour emission for anticounterfeiting

Abstract

Dual-mode and multimode excited fluorescent materials have shown huge value in the anti-counterfeiting field. Herein, a mechanical mixing and ball milling method was used to design nanohybrids of Tm/Yb:NaYF₄ upconversion phosphor (UCP) + CsPbX₃ (X = Cl/Br/I) quantum dot (QD) glasses, which display a multimode excitation characteristic. Mechanistic investigation reveals that the multimode excitation characteristic stems from radiation photon reabsorption and the no-radiation Förster resonance energy transfer from the Tm/Yb:NaYF₄ UCP to the CsPbX₃ QDs, in which the upconversion luminescence of the CsPbBr₃ QDs can be sensitized by the Tm/Yb:NaYF₄ UCP. Notably, the red upconversion luminescence of Tm³⁺ ions can be enhanced by CsPbX₃ QDs through the no-radiation Förster resonance energy transfer process. Attractively, the nanohybrids can emit polychromatic luminescence from 417 nm to 696 nm under UV light and emit bluish purple or red luminescence under 980 nm excitation. A practical anti-counterfeiting application was successfully realized based on this material with superior photostability, which proves that the multimode excited nanohybrids have great potential application in the anticounterfeiting field.