常压微等离子体辅助电化学反应制备荧光碳点和石墨烯量子点的实验和理论研究

Atmospheric pressure microplasma assisted electrochemistry is a newly developed technique for nanoparticles synthesis and engineering with many advantages including environmental friendly, fast, scalability, possible integration of synthesis and application. Carbon dots (C-dots) and graphene quantum dots (GQDs) recently emerge as “Next Big Small Thing” because of their excellent photostability, biocompatibility, excitation dependent highly tunable luminescence property, exceptional multi-photon excitation (up-conversion) property, have gained tremendous attention for their enormous potential for biomedical applications, photocatalysis and display technologies, etc. This project investigates the synthesis of C-dots and GQDs by using atmospheric pressure microplasma assisted electrochemistry based on our first achievement in fast synthesis of luminescent C-dots by using atmospheric pressure microplasma assisted electrochemisty. The spatial-temporal evolution of plasma parameters such as plasma density, electron energy distribution, etc. and their variation with discharge parameters are investigated experimentally by ICCD, time-space-resolved optical emission spectroscopy together with voltage-current characteristics and also studied numerically based on the model with flow field and electromagnetic field being coupled. The influence of plasma state on synthesis of C-dots and GQD is investigated in real time with the plasma state being diagnosed by in situ optical method and electrical method and the synthesis of C-dots and GQD being monitored by in situ UV-Vis absorption spectra and fluorescence spectra simultaneously. The mechanism of luminescence of C-dots and GQDs is unraveled by studying the influence of the functional group, size and crystal phase of the synthesized C-dots and GQDs that characterized by FTIR、XPS、TEM、Raman etc. on the luminescence of C-dots and GQDs that characterized by TIFS、TRFS. By studying the influence of plasma parameters such as plasma density, electron energy distribution, etc. on synthesis and luminescence of C-dots and GQDs, the project shed light on the controllable synthesis of C-dots and GQD by using atmospheric pressure microplasma assisted electrochemistry, and also provide reference for application of luminescent C-dots and GQDs.

常压微等离子体辅助电化学反应技术是近年发展起来的一种环境友好的纳米颗粒合成、修饰技术。碳点和石墨烯量子点具有独特的光学性质和生物相容性，在生命科学等领域体现出重要应用潜力。本项目拟在我们首次实现等离子体辅助电化学反应快速合成荧光碳点的基础上，对等离子体辅助电化学反应制备荧光碳点和石墨烯量子点进行实验和理论研究。通过高速相机瞬时成像、时空分辨光谱、常规电学测量结合数值模拟，研究常压微等离子体状态包括等离子体密度、电子能量分布等等离子体参量的时空演化和随放电参数的演变；对溶液的在线光吸收和荧光测量结合对等离子体的在线光学和电学诊断，实时无干扰考察等离子体状态对样品合成的影响；多手段多角度表征样品，研究样品表面基团、尺寸、晶相等与发光之间的内在联系；研究等离子体状态对样品合成、发光的影响，以指导荧光碳点和石墨烯量子点的等离子体辅助电化学反应合成，也为荧光碳点和石墨烯量子点的应用提供参考。

碳量子点，作为一种新型的碳基纳米材料，具有生物相容性好，可调谐光致发光，水溶性高，光热稳定性好，易于表面修饰等一系列优点，碳量子点的出现为进一步拓展纳米材料的应用领域提供了广泛的前景，其中常压微等离子体，因其无需真空环境、等离子体密度高、非热平衡特性、可用于处理溶液，更为碳量子点合成提供了崭新的机遇。.项目系统研究常压微等离子体特性随放电参量的演变。提出一种基于等离子体图像诊断开放环境中等离子体电子密度和尺寸的方法，研究表明该图像法既能突破Stark展宽法受到测量下限的限制，还能够克服电流电压法难以确定等离子体形状及受气体成分影响的问题，是一种针对开放环境等离子体密度的有效诊断技术；重点研究占空比对脉冲放电常压微等离子体特性的影响。实验结果表明占空比下降，等离子体放电体积的缩小，进而导致等离子体在脉冲工作期间内的时间平均电子密度的增加；由于脉冲间歇期的延长，前一次放电结束后的残余电子密度的变小，导致脉冲初期的电子温度以更快的速度达到更高的幅值，这部分发生在较短的脉冲宽度内的瞬态的超高电子温度，使得等离子体在脉冲工作期间内的时间平均电子温度的增加。.项目制备得到叶酸受体靶向的石墨烯量子点，该量子点不仅荧光量子效率高达77%、光热稳定性好，还具备叶酸受体肿瘤靶向功能。研究表明，叶酸分子中蝶呤环（Pterin）结构裂解产生的氨基基团能够有效的抑制激发态FR-GQDs的非辐射跃迁，促使其拥有较高的荧光量子效率；FR-GQDs惰性的碳骨架、较低的活性氧产率和表面羟基（OH）官能团对活性氧扩散的抑制作用使其具有良好的光稳定性；而石墨烯量子点表面的源自叶酸的有机分子官能团，使得FR-GQDs具备叶酸受体肿瘤靶向生物功能。制备酸性敏感碳量子点（Acid sensitive carbon dots, AS-CDs）碳量子点，该碳点可单/双光子激发，且具有长波长荧光发光特性的。研究结果表明，在中性条件下，芳环结构连接的氨基基团及氨基吩嗪聚合物结构共同参与了碳量子点的光致荧光发射过程。在酸性条件下，由于氨基的质子化，碳量子点能隙变窄，导致碳量子点单/双光子荧光波长红移。.该项目为常压微等离子体在碳量子点合成和修饰中的应用、碳量子点在生物医药领域中的应用，提供了理论和实验基础。