超声化学制备荧光/磷光双重发光碳量子点及其在生物成像中应用研究

Fluorescent carbon nanodots hold great application potential in areas of bioimaging, drug delivery, catalysis, and electronic devices due to their excellent optical properties, great biocompatibility, and ease to achieve surface functionalization. Different fabrication approaches can lead to the formation of carbon nanodots with dramatically different optical properties and structures. Meanwhile, although the fluorescent properties of carbon nanodots have been extensively and intensively explored, it is still rare to incorporate room temperature phosphorescence into carbon nanodots. This proposal aims to develop sonochemical method for the controlled synthesis of fluorescent carbon nanodots by taking advantage of the unique high temperature and high pressure conditions generated during bubble collapse under ultrasound irradiation. We would also want to use various characterization techniques to obtain detailed understanding of the physical properties as well as optical properties of such prepared carbon nanodots for future application purpose. Inspired by the spin-orbit coupling principle, current proposal also try to prepare fluorescent carbon nanodots with additional room temperature phosphorescence to achieve single-component, dual emissive probes which is very useful for the detection of reactive oxygen molecules in tumors. In order to obtain carbon nanodots with tunable fluorescent/phosphorescent properties, we will perform detailed study on how to use heavy-atom substitution method to influence the energy levels of singlet and triplet states and subsequently to modulate the relative intensities of fluorescence and phosphorescence. It is expected that such prepared dual emissive luminescent probes can be developed for the sensing of oxygen molecules in tumors which is a key component in this proposed research. Based on the understanding of fundamental physical and chemical processes associated with sonochemical synthesis of carbon nanodots, it is also expected to provide new concepts and examples of how sonochemistry can control chemical reactions, design functional nanomaterials, and benefit the further development of sonochemistry.

荧光碳点由于其具有良好的生物相容性和优异的发光性能，而且易于实现表面功能化，在生物成像、药物输运、催化和光电子器件等研究领域具有很好的应用潜力。通过不同制备方法得到荧光碳点的光学性质和结构不尽相同，虽然碳点的荧光性质已经被广泛深入地研究，但是在荧光碳点的基础上构造具有荧光-室温磷光双重发光性质的碳点还缺少相应的研究。本项目拟发展充分挖掘和利用超声化学中产生的坍缩气泡内部高温高压的物理化学环境，发展可控、高效的荧光碳点的超声化学制备方法，应用丰富的表征手段对荧光碳点进行结构和光学性质上的表征。探索超声化学制备荧光碳点过程中的物理化学问题，在此基础上通过自旋-耦合效应来构造室温磷光，并深入探究所获得体系中单线态和三线态之间的能级调控规律，从而获得强度可控的具有双重发光性质的碳点，并研究将其应用于肿瘤组织中氧气分布检测。

碳点作为新兴的发光材料，在生物成像、传感、催化以及电子器件等领域有着非常重要的应用前景，本项目利用声空化现象产生的坍缩气泡内部高温高压物理化学环境，采用合适的前驱体碳材料制备荧光碳点。经过一些列的实验研究与条件筛选，尝试荧光碳点前驱体组合与前驱体浓度，我们得到荧光量子效率高达77.3%的碳点，通过对比，我们验证这种通过超声化学方式得到的碳点在光学稳定性上也要比普通的荧光染料好很多，未来在生物成像领域有很好应用前景。我们也探索了通过引入重原子到碳前驱体结构中，采用自旋-耦合效应来构造室温磷光的设想，初步研究结果表明这个方案是切实可行的，可以构造室温荧光与磷光双重发光碳点，但是对具体的合成与机理研究需进一步深入探索。我们的研究也进一步证实通过超声化学方式制备荧光碳点的机理主要为含有非挥发性物质的液体纳米液滴可以通过毛细波作用，微喷射或气泡聚结注入到塌陷的气泡中，一旦纳米液滴进入坍塌的气泡的热的内部，溶剂蒸发，并且在气相中的化学反应发生类似于火焰热解中的过程。这个制备机理有望为未来发展更多的新型碳材料奠定实验与理论基础。