In this study, the hexagonal NaYF₄:Yb³⁺/Ho³⁺/Ce³⁺ microcrystals were synthesized controllably, and upconversion luminescence excited at 940 nm and its application in temperature-responsive anti-counterfeiting are reported. It is clarified that the Ln³⁺ (Ln = Y + Yb + Ho + Ce) density ratio of bottom plane to side plane in the unit cell can be regulated by Ce³⁺ doping. It is also proved that the energy transfer of Yb³⁺ to Ho³⁺ is responsible for the activation of Ho³⁺ under 940 nm excitation, while the cross relaxation between Ho³⁺ and Ce³⁺ participates in the redistribution of electron population of ⁵S₂/⁵F₄ and ⁵F₅ levels. Both theory and experiment confirm that the intensity ratio of red to green emission (I_R/I_G) as a function of temperature as an independent variable has good linear characteristics in the temperature range of 300–500 K. Due to the good responsiveness of multicolor luminescence to temperature, the hexagonal NaYF₄:Yb³⁺/Ho³⁺/Ce³⁺ with tunable morphology is a promising candidate for advanced temperature-responsive upconversion anti-counterfeiting. Our results provide a new pathway for the controllable synthesis of hexagonal NaYF₄ microcrystals as well as the regulation of upconversion luminescence that is excited by wavelengths other than 980 nm and its application in anti-counterfeiting.

本研究可控合成了六方NaYF ₄ :Yb ³⁺ /Ho ³⁺ /Ce ³⁺微晶，报道了在940 nm激发的上转换发光及其在温度响应防伪中的应用。阐明了晶胞中底面与侧面的Ln ^{3+ (Ln = Y + Yb + Ho + Ce)密度比可以通过Ce 3+}掺杂来调节。也证明了Yb ³⁺到Ho ^{3+的能量转移是Ho 3+}在940 nm激发下活化的原因，而Ho ³⁺和Ce ³⁺之间的交叉弛豫^参与5 S ₂ / ⁵ F ₄和⁵ F ₅能级电子布居的再分布。理论和实验都证实，红绿发射强度比（I _R / I _G）作为温度的函数作为自变量在300-500 K的温度范围内具有良好的线性特性。由于良好的响应性多色发光温度，六方NaYF ₄ :Yb ³⁺ /Ho ³⁺ /Ce ³⁺具有可调形态是先进的温度响应上转换防伪的有希望的候选者。_{我们的研究结果为六方NaYF 4}微晶的可控合成、980 nm以外波长激发的上转换发光调控及其在防伪中的应用提供了新途径。