The widespread demand for multifunctional materials that can be used for anticounterfeiting purposes, as dual-mode phosphors, or as optical nanothermometers has inspired us to synthesize Yb³⁺/Tm³⁺/Ln³⁺ (Ln = Eu, Tb)-doped LaPO₄ nanoparticles (NPs) and, based on these, luminescent fibers that utilize and extend the properties of the NPs. They show intense dual-mode color-tunable emission and temperature-dependent up-conversion (UC) luminescence, which makes them multifunctional and of a high potential applicability. The nanomaterials were obtained by a simple and fast coprecipitation method, yielding pure-phase monoclinic products. The products were used as luminescence activators in cellulose fibers, showing their potential applications for security purposes. They can emit strong UC and down-conversion luminescence within one particle, under excitation of commercially available near-infrared (NIR) and ultraviolet (UV) excitation sources. The pure red and green emissions under UV irradiation resulted from the presence of Eu³⁺ or Tb³⁺ ions in the structure of the products, whereas violet-blue emission was obtained under NIR excitation because of Yb³⁺ and Tm³⁺ codopants. After simultaneous UV/NIR double-laser excitation, they obtained NPs that show a complex luminescence resulting from Tm³⁺ (after energy transfer from Yb³⁺), Tb³⁺, or Eu³⁺. The obtained UC emission can be tuned, giving a huge color shift (from orange or green to blue). What is more, thanks to the presence of thermalized levels of Tm³⁺ ions, these materials can act as promising temperature nanosensors in a wide range of temperatures from 293 to 679 K. Using the fluorescence intensity ratio technique, relatively high thermal sensitivity (S_r) was obtained, 0.024 and 0.022 K^–1 for 293 K for the Yb³⁺/Tm³⁺/Eu³⁺ and Yb³⁺/Tm³⁺/Tb³⁺ samples, respectively.

中文翻译：

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紫外和近红外可激发LaPO ₄：Yb ³⁺ / Tm ³⁺ / Ln ³⁺（Ln = Eu，Tb）纳米纤维，用于发光纤维和光学温度计

对可用于防伪目的的多功能材料的广泛需求，如双模荧光粉或光学纳米温度计，促使我们合成了掺Yb ³⁺ / Tm ³⁺ / Ln ³⁺（Ln = Eu，Tb）的LaPO ₄纳米颗粒（NPs），并基于这些颗粒发光纤维，这些发光纤维利用并扩展了NPs的特性。它们显示出强烈的双模色彩可调发射和与温度有关的上转换（UC）发光，这使其具有多功能性并具有很高的潜在适用性。通过简单，快速的共沉淀方法获得纳米材料，得到纯相单斜晶产物。该产品在纤维素纤维中用作发光活化剂，显示出其在安全方面的潜在用途。在市售的近红外（NIR）和紫外（UV）激发源的激发下，它们可以在一个粒子内发出强UC和下转换发光。Eu ³⁺或Tb的存在导致紫外线辐射下的纯红色和绿色发射产物的结构中有³⁺离子，而由于Yb ³⁺和Tm ^3+的共掺杂物，在NIR激发下获得了紫蓝色发射。在同时进行UV / NIR双激光激发后，他们获得了由Tm ³⁺（从Yb ³⁺转移能量），Tb ³⁺或Eu ³⁺产生的复杂发光的NP 。可以调整获得的UC发射，从而产生巨大的颜色偏移（从橙色或绿色到蓝色）。而且，由于存在Tm ³⁺离子，这些材料可以在293至679 K的广泛温度范围内充当有希望的温度纳米传感器。使用荧光强度比技术，可获得相对较高的热敏性（S _r），对于293 K，其热敏度为0.024和0.022 K ^–1。 Yb ³⁺ / Tm ³⁺ / Eu ³⁺和Yb ³⁺ / Tm ³⁺ / Tb ³⁺样品。