一步法合成特异性pH响应碳量子点及其发光机理研究

本研究利用溶剂热反应, 以柠檬酸为碳源, 甲酰胺和水为混合溶剂, 一步合成氮掺杂碳量子点。研究表明, 所制备的氮掺杂碳量子点具有良好的水溶性和明亮的蓝光发射, 以及典型的依赖于激发光的荧光发射特性。特别的是, 该碳量子点显示出不同于普通碳量子点的、独特的pH响应行为, 除了具有传统的荧光强度随着pH变化的响应行为外, 还表现出在碱性条件下, 产生新的不依赖于激发光的红光发射的性能。通过系统研究碳量子点在不同碱性环境和不同羟基含量溶液中的荧光特性, 结合拉曼光谱、红外、XPS等表征, 分析其化学组成与表面态分子, 探讨了其发光机制, 证实这种特异性pH响应行为是由于在强碱性环境中含有的大量氢氧根结合在碳量子点表面, 从而改变碳量子点的表面状态, 形成新的稳定的发光中心。最后, 通过细胞毒性实验及细胞成像分析表明, 所获得的碳量子点具有低细胞毒性, 并可作为荧光探针应用于细胞成像, 显示其在生物成像领域的潜在应用价值。

One-step Synthesis of Specific pH-responsive Carbon Quantum Dots and Their Luminescence Mechanism

Nitrogen-doped carbon quantum dots (CDs) were synthesized via a facile one-step solvothermal reaction using citric acid, formamide and water. Subsequent characterizations indicate that the nitrogen-doped CDs are featured by good water solubility, bright blue emission and typical excitation-dependent emission. However, unlike from conventional pH response of most CDs, the as-prepared CDs possess unique pH response. Apart from that fluorescence intensity varies with the pH value, the prepared CDs can generate excitation-independent red emission in alkaline conditions. Through scientific research towards fluorescent property of prepared CDs in different alkaline environments as well as solution with different hydroxyl content, combined with chemical composition and surface states based on Raman spectrum, FT-IR and XPS, the fluorescent mechanism of the unique pH response are attributed to a large number of hydroxyl groups in strong alkaline environment bonded to the surface of CDs, thus changing the surface states of CDs, further forming a new stable luminescence center. Finally, cytotoxicity tests and cell imaging experiments showed that the prepared CDs have low cytotoxicity, and can be used as fluorescent probe for cell imaging, indicating their potential application in the field of biological imaging.