稀土掺杂上转换发光纳米晶与贵金属表面等离子材料的可控复合及发光增强研究

Recently, rare-earth-doped upconversion photoluminescence nanomaterials have drawn numerous research attentions due to their unique properties and wide applications. One of the key scientific question among the research is how to effectively enhance the upconversion efficiency for these prominent photoluminescence nanomaterials. Plasmonic effects have the great potential to enhance the upconversion efficiency with emission band selectivity. However, the state-of-the-art research work on surface-plasmon-enhancement of upconversion emissions is not sufficient and the enhancement mechanism is rather arbitrary. Therefore, to clarify the enhancement mechanism and the structure-property relationship in an upconversion-plasmonic composite structure, it is necessary to modulate both the spectrum coupling as well as the spatial relationship between the two components. This proposal is dedicated to the synthesis of high-quality rare-earth-doped upconversion and noble-metal-based plasmonic nanomaterials and the precisely controlled integration of them through selective surface modification and chemical self-assembly. The upconversion efficiency can be then significantly enhanced and finely tuned by the plasmonic enhancement effect. We will focus on the dependence of the enhancement effect on the morphology, size, and structure of the rare-earth/noble-metal composite. In addition, we can utilize the upconversion nanocrystals as nano-sized optical probes to convert the locally bounded and invisible plasmonic polaritons into visible light emissions for the study on the excitation, distribution, and propagation mechanism of surface plasmonic polaritons. Furthermore, chemical sensors with high selectivity and sensitivity to certain target species can be then fabricated based on these upconversion-plasmonic integrations. In summary, this work can both contribute to the theoretical fundaments and provide building blocks for the researches and applications of surface-plasmon-enhanced upconversion photoluminescence.

近年来，稀土掺杂上转换发光纳米材料得到了广泛的关注与应用。如何有效提高其发光效率是研究的重点科学问题之一。表面等离子共振效应具有显著增强上转换发光的潜力，并可实现对不同波段的选择性调节。然而，现有的研究工作仍不够深入，机理亦不够清晰。精确调节上转换纳米晶与表面等离子共振纳米结构之间的光谱耦合作用与相对位置关系，深入研究其构效关系的工作亟待开展。本项目拟制备高质量上转换发光纳米晶与贵金属纳米材料，通过表面选择性修饰和自主装方法实现二者的可控复合。利用表面等离子共振效应大幅提高上转换纳米晶的发光效率，研究发光增强效应与复合结构各组份的形貌、尺寸和结构之间的关系。利用上转换发光纳米晶作为光学探针，将表面等离子激元信号转化为可见的发光信号，研究其激发、分布及传播行为。并在此基础上制备对特定目标分子具有高选择性、高灵敏度的化学传感器。为表面等离子共振增强上转换发光的深入研究和应用奠定理论和材料基础。

近年来，稀土掺杂上转换发光纳米材料得到了广泛的关注与应用。如何有效提高其发光效率是研究的重点科学问题之一。表面等离子共振效应具有显著增强上转换发光的潜力，并可实现对不同波段的选择性调节。本课题的总体研究目标是以具有表面等离子激元性能的贵金属纳米材料与具有上转换发光性能的稀土纳米颗粒进行可控复合，从而观察、总结表面等离子共振性质对临近发光过程的影响作用及其机理。项目实施期间，合成制备了一系列具有不同形貌、结构与性质的表面等离子共振纳米材料，包括Au纳米球、纳米棒以及Ag纳米线等等。同时，我们还制备了一系列具有不同激发与发射波长的稀土掺杂上转换发光纳米晶，包括Yb/Er，Yb/Tm共掺上转换发光纳米颗粒及其核壳结构等等。在此基础上，我们将表面等离子共振纳米材料与稀土掺杂上转换发光纳米晶进行可控复合，制得一系列复合纳米结构，并对其发光性质进行详细表征，总结其发光过程与机理，取得了一系列研究成果。