稀土掺杂上转换发光微纳粒子在防伪识别方面有着巨大的应用前景。 首先采用水热合成法制备了NaYF₄:Yb³⁺/Eu³⁺微纳粒子, 通过X射线衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)对NaYF₄:Yb³⁺/Eu³⁺微纳粒子的尺寸、 形貌和结晶度等方面进行了研究, 同时使用980 nm的泵浦源对NaYF₄:Yb³⁺/Eu³⁺微纳粒子的发光性能进行了分析; 其次将NaYF₄:Yb³⁺/Eu³⁺微纳粒子与酒精按一定比例混合制成丝网印刷剂, 结合网络定制的丝网模版在纸上印制了不同字样的防伪图案, 风干后将字样暴露在980 nm的激光辐照下, 并使用相机对其进行成像研究; 最后将印制的字样分成两部分, 一部分保存在室内25 ℃恒温环境下, 另外一部分保存在冬季一月份室外自然环境下, 保存地点均为西安市, 一周后对不同环境下的字样再次使用完全相同的实验仪器进行成像测试。 实验及测试结果显示, NaYF₄:Yb³⁺/Eu³⁺微纳粒子与NaYF₄标准卡的衍射峰完全一致, 没有其他杂质产生; 实验合成的微纳粒子外形均为六方体, 且平均长度和横截宽度分别为209和175 nm, 微纳晶体表面光滑、 无缺陷、 未弯曲、 结晶度较高、 分散性较好, 电子衍射环与NaYF₄:Yb³⁺/Eu³⁺微纳粒子的312, 300和302晶面相对应; NaYF₄:Yb³⁺/Eu³⁺微纳粒子受掺杂离子的影响, 在不同的能级跃迁下分别产生蓝、 绿、 黄、 红四种可见光, 通过对NaYF₄:Yb³⁺/Eu³⁺微纳粒子荧光光谱分析, Eu³⁺非对称性比率约为1, 表明磁偶极子跃迁与电偶极子跃迁相当; NaYF₄:Yb³⁺/Eu³⁺微纳粒子制成的丝网印刷剂在不同环境下成像结果良好均清晰可见、 容易辨识, 但受存放环境影响, 室内成像结果与最初的成像结果相比变化不大, 室外所有成像字符受到自然环境下水汽的影响, 亮度均略有下降, 但仍能识别。 成像结果表明, 所制备的NaYF₄:Yb³⁺/Eu³⁺微纳粒子在防伪识别方面具有稳定性、 可靠性等特点, 但仍受到影响程度可控的自然环境因素影响。 综合来看, 其在防伪识别方面有着很大的应用前景。

Rare earth doped upconversion luminescent micro-nano particles have great application prospects in anti-counterfeit identification. First of all, in the article NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles prepared by hydrothermal synthesis method, The size, morphology and crystallinity of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles were investigated by X-ray diffraction (XRD)、 scanning electron microscope (SEM) and transmission electron microscope, and the luminescence properties of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles were analyzed using a 980 nm pump source; Secondly, NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles and alcohol were mixed in a certain proportion to make a screen printing agent and combined with a network-customized screen template, different anti-counterfeit patterns were printed on the paper. After air drying, the words were exposed to a 980 nm laser and camera were used to study it. Finally, the printed words were divided into two parts, one was stored indoors at a constant temperature of 25 ℃, and the other was stored in the outdoor natural environment in January in winter. The storage locations are all Xi’an. After one week, in different environments the words were again tested with the same experimental instruments for imaging. The experiment and test results show that the diffraction peak of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles is a completely consistent standard card of NaYF₄, and no other impurities are generated. In this experiment, The synthesized micro-nano particles are all hexagonal in shape, and the average length and cross-sectional width are 209 and 175 nm respectively. The surface of the nanocrystal is smooth, defect-free, unbent, with high crystallinity and good dispersion. The electron diffraction ring corresponds to the 312, 300, and 302 crystal planes of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles. NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles are affected by doped ions, it produces four visible lights of blue, green, yellow and red by different energy level transitions. Through fluorescence spectrum analysis of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles. The asymmetry ratio of Eu³⁺ ion is about 1. This result shows that the magnetic dipole transition is equivalent to the electric dipole transition. Screen printing agent of NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles are good in different environments, the results are clear and easy to identify. However, affected by the storage environment, The results of indoor imaging have not changed much from the original imaging results. All characters of outdoor imaging are affected by moisture in the natural environment, the brightness is slightly reduced, but they can still be recognized. The imaging results show that the prepared NaYF₄:Yb³⁺/Eu³⁺ micro-nano particles have the characteristics of stability and reliability in anti-counterfeiting identification, but they are still affected by natural environmental factors with a controllable degree. On the whole, it has great application prospects in anti-counterfeiting identification.