Temperature-sensitive lanthanide-doped core-multishell nanocrystals with excitation-wavelength-dependent bimodal luminescence thermo-behaviors and their application in dynamic anticounterfeiting

Abstract

Herein, we constructed a sort of particular lanthanide-doped core-multishell nanocrystals, NaErF4:0.5%Tm@NaYF4 @NaYF4:50%Yb,2%Ho@NaYF4:50%Yb (CSSS-UCNPs), which first integrated bimodal temperature-dependent UC emissions and orthogonal luminescence triggered by dual NIR lasers. Specifically, CSSS-UCNPs respectively presented strong yellowish green (Ho3++Er3+) and red luminescence (Er3+) under 980 nm and 1550 nm excitations via regulating constructional parameters. Moreover, the photoluminescence of CSSS-UCNPs showed remarkable temperature dependence, and luminescence thermo-behaviors changed with excitation wavelengths: thermo-enhanced Ho3+ green luminescence under 980 nm irradiation, and thermo-quenched Er3+ red luminescence under 1550 nm excitation. The unexpected thermal intensification of Ho3+ luminescence in CSSS-UCNPs of such large dimension (>>50 nm) violated the available literature involving size-dependent thermal enhancement. It’s discovered that the heat-induced vibration attenuation of oleate ligands mainly contributed to 980 nm-excited thermal intensification, which had never been reported before. Thanks to their unique excitation/temperature-responsive luminescence, the printed patterns by CSSS-UCNPs displayed noticeable changes in brightness and chromaticity under NIR excitations when raising the temperature. Briefly, this work affords a promising candidate for high-security-level anticounterfeiting, and, more importantly, supplies new perspectives on anomalous thermal enhancement in large-sized Yb3+-sensitized UCNPs.