生物窗口激发-发射窄带系长余辉发光材料设计、合成及应用

The phosphors emitting long persistent phosphorescence in biologically transparent window have important potential used in the research field of bio-imaging today. The past few years have witnessed great progress in the development of synthetic technique, material kinds and afterglow mechanism of these long phosphorescent phosphors (LPPs). However, the afterglow excitation bands of LPPs have received little attention in the previous works. Almost all of most effective afterglow excitation bands of LPPs locate in the ultraviolet region, which not satisfy the requirements of repeatability and recyclability. Therefore, it is urgent to develop efficient long phosphorescent phosphors with the emission and excitation bands in biologically transparent window. In this project, we suggest an idea of element substitution to design and prepare the long phosphorescent phosphors with the emission and excitation bands in biologically transparent window of live animals through the selection of hosts and co-dopants. We try to reveal the relationship between band gaps of hosts and excitation bands, persistent duration and traps distribution, as well as emission bands and emission centers via the theoretical simulation and the spectroscopic technique. We also propose the practical design-methods of low bandgap LPPs under the excitation of VIS-NIR light. We further investigate the effects on valence state of emission center, microstructures of defects, as well as formation, migration, capture, store, release and recombination dynamics of the carriers by using the multidisciplinary characterization, then establish the theoretical afterglow models. At last, we anticipate studying the nanocrystallization of LPPs and exploring surface modification technique to improve the biological activity of the bio-labels with long persistent phosphorescence. To reach the goal of dual mode monitoring and therapy, we synthesize the photothermal effect and targeted imaging-conjugated bio-labels and discuss the possibility of functional long phosphorescent phosphor as the bio-labels applied in in vivo bio-imaging and cancer therapy.

生物窗口长余辉材料在活体成像等领域具有重要应用前景，并在合成技术、材料组成及发光机理等方面取得部分成果。但是以往研究集中于余辉发射带，激发带研究尚未得到重视。绝大多数材料的长余辉最强激发带处于紫外区域，不利于标记物反复激活和循环使用。为解决这一重要议题，迫切需要将余辉最有效激发带延伸至生物窗口。本项目结合理论模拟计算，通过基质、发光中心选择设计激发-发射带均位于生物窗口的长余辉生物标记物；从能带结构与激发波段、陷阱分布与余辉衰减、离子能级与发射波段间相互关系入手，建立生物窗口激发下窄带系长余辉材料设计准则；采用多方位表征技术对发光中心离子价态、缺陷微型态和载流子形成-迁移-捕获-存储-释放-复合过程动力学进行表征，构建长余辉发光唯象模型；探索长余辉材料纳米化及功能化生物标记物表面包覆技术，通过靶向识别和光热疗功能耦联，实现长期监测+药物治疗双功能，研究其在生物成像及癌症治疗等领域潜在应用

近红外长余辉材料已经成为当今的研究热点。本项目共计包含发表SCI论文12篇，其中SCI一区论文3篇（Chemical Engineering Journal. 2017, 322. 314-327；Advanced Optical Materials. 2018, 6, 1701161；Nanoscale. 2019, 11, 12742-12754；），二区论文6篇。申请发明专利14项，授权发明专利4项。代表性研究成果如下：.开发了能够在可见光-近红外光激发下得到的长余辉材料CaSnO3：Bi2+，这种长余辉材料可以被650-750纳米的近红外激发并发出持续1小时的800纳米近红外长余辉。该成果已经投稿至Advanced Materials。.开发了SrAl12O19：Cr3+长余辉材料。这种材料具有600-800纳米和800-1200纳米的双波段发射特性，能较为全面的覆盖生物窗口区域。这样就能更加广泛的利用生物窗口的宽度以便于提高活体成像的分辨率和清晰度。相关研究成果以封面论文的形式发表于Adv. Opt. Mater. 2019, 10,17203上。.开发了一种具有生物降解能力的 CaS:Tm3+@SiO2核壳近红外长余辉纳米材料，这种长余辉材料具有优良的水溶性，可以在水中自由分解。从而不会造成活体内的累积伤害。在这个基础上我们可以提高长余辉纳米颗粒的尺寸以增强长余辉。.Fe3+离子是一种荧光猝灭离子，通常不作为发光中心使用、但是在我们合成的SrAl12O19: Fe3+近红外长纳米材料中，这种材料不但具有811纳米的荧光发射，还具有811纳米长余辉发光。进一步通过用APTES修饰实现了近红外长余辉纳米材料在溶液中的长期稳定性。这里我们需要强调的是，APTES是一种亲和力较强的大分子，这种表面修饰剂可以最大限度的提高水动力学特性。.碳氧化物是一种生物友好材料，这种长余辉材料具有良好的形貌演变特性，可以实现从棒状到竹状的转变。我们合成的这种材料便具有这样的优良特性。此外我们合成的La2O2CO3: Eu3+, Ho3+长余辉材料还具有过氧化氢探测的能力，可以实现基于长余辉的体外检测。