Abstract:

Using coal as a precursor to prepare carbon nanomaterials is of high significance for the clean and resource utilization of coal. Carbon dots show great potential in many application fields owing to their excellent performance. However, current chemical and physical methods for preparation of coal-based carbon dots have some shortcomings, such as the use of chemicals, expensive equipment, and difficult to scale production. Therefore, it is urgent to develop a green and scalable preparation method. Herein, using anthracite as a precursor, hydrodynamic cavitation was first applied for the exfoliation of coal-based carbon dots. The morphological results showed that the carbon dots were quasi-spherical with an average size of 2.1nm and graphitic lattice structure. XPS and FTIR spectra demonstrated the carbon dots mainly compose of C and O elements and had abundant oxygen-containing groups on the surface, which caused good dispersion in aqueous solution. Due to its special core-shell structure, the carbon dots exhibited unique fluorescence properties. It showed two fluorescent peaks of blue and yellow emission under excitation wavelength of 360nm. When the wavelength was less than 360nm, the blue emission was dominant in fluorescence spectrum. Otherwise, the yellow fluorescence was dominant. In addition, as the excitation wavelength increased, the blue peak showed dependent behaviors, while the yellow emission was basically unchanged. The successful preparation of the carbon dots provided a new physical basis for the investigation of the fluorescence mechanism with double emission and the transition and conversion between the two emission peaks. More importantly, the research results would provide new ideas and methods for green, efficient, low-cost, continuous and large-scale preparation of carbon dots, as well as the high-value utilization of coal resources.

Key words: carbon dots, hydrodynamic cavitation, coal, fluorescence

摘要：

以煤为原料制备碳纳米材料，对煤炭的清洁化和资源化利用具有重要意义。纳米碳点以其优异的性能，在许多领域显示出巨大的应用前景。目前，制备煤基碳点的化学和物理方法存在着使用药剂和设备昂贵、难以规模化生产等不足，因此亟需开发一种绿色环保、可规模化的制备方法。以无烟煤为原料，本文首次采用水力空化的方法剥离出碳点。该碳点呈类球形颗粒，平均粒径为2.1nm，具有石墨类晶格结构；主要由C、O元素组成，表面附着丰富的含氧基团，水溶液中分散性良好。由于该碳点特有的核壳结构，展现出独特的荧光性能。在360nm光照射下，显示出蓝色和黄色两个荧光峰；当用小于此波长光激发时，蓝色荧光峰占主导地位，而大于此波长时，黄色荧光峰占主导地位；另外，蓝色荧光峰表现出对激发波长的依赖性，而黄色荧光峰位置基本不变。本碳点的成功制备为研究其荧光机理和双荧光峰之间的过渡与转换提供了新的实物基础。更重要的是，研究成果将为碳点的绿色、高效、低成本、连续和规模化制备，以及煤炭资源的高值化利用提供新思路和新方法。

关键词: 碳点, 水力空化, 煤, 荧光