镓酸盐长余辉纳米材料的高效激发与温度传感特性研究

Fluorescent temperature probes based on long persistent materials without real-time external excitation are immune to heating effects and autofluorescence, and thus can achieve accurate temperature measurement, which have the potential to substitute conventional ones with real-time excitation and play a pivotal role in the areas of cell temperature imaging and thermal therapy of tumor. This project is dedicated to exploiting long persistent temperature probe in the near infrared II region, which has merits of deep tissue penetration and not been reported so far. Ni2+ doped gallates are selected as study objects due to their persistent luminescence located in the near infrared II region. However, there are several great challenges for Ni2+ doped gallate nanocrystals, such as controllable synthesis of nanocrystals, efficient excitation and improvement of thermal sensitivity. In view of the above problems, the research contents are as follows. The controllable preparation of gallate nanocrystals with core-shell structure will be investigated. For effective excitation of Ni2+ afterglow in the biological window, the energy transfer channels between rare earth and Ni2+ ions will be constructed and discussed in details. Aiming at improvement of thermal sensitivity, the influences and manipulations of trap depth will be studied. The relationship between thermal sensitivity and trap depth will be systematically analyzed. Meanwhile, the mechanisms of temperature sensing for long persistent materials will be elaborated. Finally, the long persistent temperature probes are obtained in the near infrared II region, whose thermal sensitivity and persistent time are more than 5% K-1 (in the physiological temperature range) and 2 h, respectively.

免实时激发的长余辉材料作为荧光温度探针，可避免热效应的影响、排除生物自发荧光的干扰，极大地提高温度测量的准确性，有望替代传统实时激发的荧光温度探针，在细胞温度成像与肿瘤热治疗领域发挥巨大作用。本项目致力于研发具有深层组织探测优势的近红外二区长余辉温度探针（尚未见报道），选取余辉发光在近红外二区的Ni2+掺杂镓酸盐材料为研究对象，但Ni2+掺杂镓酸盐纳米晶在可控制备、高效激发以及测温灵敏度提高方面存在巨大挑战。针对以上问题，本项目拟开展如下研究：探索核壳结构镓酸盐纳米晶的可控制备；构建高效的稀土与Ni2+离子能量传递通道，探索在生物窗口有效激发Ni2+余辉发光；以提高测温灵敏度为目标，围绕陷阱深度的影响与调控开展研究，阐明陷阱深度与测温灵敏度的关系，揭示长余辉材料温度传感机理。最终研发出在生理温区测温灵敏度大于5% K-1、余辉时间大于2小时的近红外二区长余辉温度探针。

本项目围绕镓酸盐长余辉纳米晶的可控制备，高效激发等开展研究，以提升其余辉性能为目标，并探索在余辉温度探针方面的应用。分别采用盐微乳液法制备Y3Al2Ga3O12:Ce3+/Cr3+/Nd3+纳米晶，与介孔模板法制备mSiO2@Zn0.6Ca0.4Ga2O4:Cr3+/Yb3+纳米晶。通过对合成工艺与反应条件优化，实现纳米晶形貌、尺寸同步调控，突破了镓酸盐纳米晶的可控制备技术。构建能量传递通道，结合陷阱密度与深度调控，解决了Nd3+/Yb3+近红外二区余辉发光低效的难题。研究发现Nd3+离子（1063 nm）余辉时间可达60分钟，余辉穿透深度为3.9毫米；Yb3+离子（1000 nm）余辉时间达10分钟，余辉穿透深度为2.8毫米。研究结果表明镓酸盐长余辉纳米材料在生物成像领域展现出巨大的应用潜力。镓酸盐长余辉纳米材料有望作为荧光温度探针，但余辉强度弱，导致信噪比与测量精度差。余辉强度随时间推移不断衰减，为确保其测温稳定性，适用于余辉温度探针的测温方法有待进一步探索。除以上研究外，为提高灵敏度我们还开展了如下研究工作：一是通过双波长激发，促使稀土离子发光叠加增强，并从理论上阐明灵敏度叠加提高的可行性与必要条件。二是利用晶体负热膨胀特性，设计了兼具热猝灭与负热猝灭特性的高灵敏度荧光温度探针。本项目研究成果为设计高灵敏度荧光温度探针提供理论依据及指导。该项目执行期间发表论文5篇，分别发表于Optics Letters, Physica Status Solidi - Rapid Research Letters, Nanoscale, Journal of Materials Chemistry B, Journal of luminescence等期刊。

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