以无水柠檬酸和邻苯二胺为碳源,采用一步溶剂热法制备出了溶剂依赖发光的碳纳米点,通过原子力显微镜对所制备的碳点进行形貌及结构表征,发现碳量子点高度在1.5 nm左右,其是由2~3层类石墨烯片层堆叠而成的。通过荧光光谱(PL)和紫外-可见(UV-Vis)吸收光谱对碳量子点的光学性质进行测定,发现碳量子点的吸收主要与内部碳核和表面态有关,最大吸收对应的波长分别为285 nm和430 nm。有机溶剂中最大发射波长为表面缺陷态发光波长,荧光峰位在515 nm处。随着体系中水含量的增加,最大发射峰强度降低,发射峰的位置发生红移,水含量(体积百分数)为10%~100%时,荧光信号强度与水含量呈线性关系,最优条件下水含量的检测极限为0.1%。实验结果证实,该碳量子点有望成为实时定量检测有机溶剂中水含量的荧光探针和传感器。研究结论不仅拓宽了碳纳米点的应用范围,还提供了一种简单有效检测有机溶剂水含量的方法。

With anhydrous citric acid and o-phenylenediamine as carbon sources, solvent-dependent emitting carbon nanodots are prepared by the one-step solvothermal method. The morphology and structure of the prepared carbon dots are characterized using atomic force microscope. It is found that the carbon quantum dots have a uniform height around 1.5 nm, and are mainly consist of few layers of graphene. The optical features of as-prepared carbon quantum dots are further confirmed by photoluminescence (PL) spectra and UV-visible (UV-Vis) absorption spectroscopy. It is found that the main absorbance is attributed to the carbon core and the surface states, and the maximum absorption occurs at wavelengths of 285 nm and 430 nm. In addition, the fluorescent emission in organic solvents peaks at 515 nm and its corresponding emission wavelength is the luminescence wavelength of surface defect state. With the increase of water content in the system, the emission peak red-shifts and the maximum emission intensity gradually decreases. When the water content (volume fraction) is in the range from 10% to 100%, the fluorescence signal intensity is linearly proportional to water content, and the detection limit of water content is 0.1% under the optimal condition. The experimental results confirm that these novel carbon quantum dots have a potential application as a probe and a sensor for the real-time quantitative detection of water content in various organic solvents. The results obtained here not only broaden the application range of carbon nanodots, but also provide a simple and effective method to detect water content in organic solvents.