Abstract This study presents a novel and high-level anticounterfeiting strategy based on Ce/Yb/Ho triply-doped NaGdF4 nanocrystals with temperature-responsive multicolor emission. A critical factor leading to the multicolor emission is confirmed by comparing the luminescence thermal behaviors of nanocrystals in various atmospheres. Through analyzing the temperature-dependent lifetimes of Yb3+ ions in air, we demonstrate that thermally-induced multicolor emission mainly originates from the gradually-attenuated H2O quenching effect. Because the cross-relaxations between Ce3+ and Ho3+ ions and the nonradiative transitions of Yb3+ ions create plenty of phonon heat, the multicolor emission of nanocrystals can be achieved under 975 nm excitation at a relatively low power density. This recognition method is efficient and convenient for security authentication. The as-synthesized core nanocrystals can be directly used to fabricate anticounterfeiting ink without further processing (e.g. core/shell or hybrid). Therefore, the small-sized β-NaGdF4:Yb/Ce/Ho nanocrystals are promising candidate for security application.

中文翻译：

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用于防伪应用的单个 NaGdF4:Yb/Ce/Ho 上转换纳米晶体的热响应多色发射

摘要 本研究提出了一种基于具有温度响应多色发射的 Ce/Yb/Ho 三重掺杂 NaGdF4 纳米晶体的新型高级防伪策略。通过比较纳米晶体在各种气氛中的发光热行为，确认了导致多色发射的关键因素。通过分析空气中 Yb3+ 离子的温度依赖性寿命，我们证明热致多色发射主要源于逐渐衰减的 H2O 猝灭效应。由于 Ce3+ 和 Ho3+ 离子之间的交叉弛豫以及 Yb3+ 离子的非辐射跃迁产生大量声子热，因此可以在 975 nm 激发下以相对较低的功率密度实现纳米晶体的多色发射。这种识别方法对于安全认证来说是高效且方便的。合成后的核纳米晶体可直接用于制造防伪油墨而无需进一步加工（例如核/壳或混合）。因此，小尺寸的 β-NaGdF4:Yb/Ce/Ho 纳米晶体是安全应用的有希望的候选者。