Preparation Of Coal-Based Fluorescent Carbon Dots And Its Performance Tuning

In recent years,the fluorescent carbon dots(CDs)has been widely concerned and studied,because of its most significant advantages in terms of elemental abundance,low toxicity,good biocompatibility,chemical inertness,low cost and so on.However,most of the existing methods of preparation of carbon dots have the disadvantages such as high energy consumption,high pollution,low yield and monotonous emission color.Coal-based raw materials with high carbon content are not only very rich in reserves,but also very good carbon source.Based on this,this paper focuses on the preparation of high-yield fluorescent CDs from coal-based raw materials by green synthesis method,and tuning its optical properties by doping of heterogeneous elements,then further explores its possible application.The contents of the study and the results are mainly reflected in the following two aspects:(1)At room temperature and pressure,the fluorescent carbon dots were prepared by selectively oxidizing and etching coal tar pitch with HCOOH and H2O2 ratio solution.The yield of the obtained fluorescent CDs is not only 49%,but also has a concentration-dependent multicolor-adjustable light-emitting property.As the concentration gradually decreases from 3.0 g/L to 0.03 g/L,the emission color of the CDs gradually changes from red to blue,and its luminous range basically covers the entire visible region.Based on the analysis of CDs,it is proposed that the morphological changes caused by the intermolecular interactions between carbon particles changes the way of carbon radiation recombination,which leads to the concentration-dependent multi-color luminescence phenomenon.In addition,the photocatalytic activity of the obtained fluorescent CDs was also studied.It was found that the samples exhibited strong reducibility under visible light irradiation and could be used as a photoreduction agent in chemical synthesis.(2)The fluorescent carbon dots prepared only by the use of hydrogen peroxide selectively oxidizing and etching anthracite is single in luminous color,which mainly in the blue-green area.In this paper,the coal-based CDs were modified by the method of solvothermal method using diammonium phosphate to obtain the two-color luminescent centers.The two elements of N and P are incorporated into the structure of CDs by composition,structure and other characterization.N,P co-doping leads to the presence of two peak emitting of coal-based CDs in the yellow and red regions,respectively.N,P co-doped coal-based CDs not only has a strong photocatalytic oxidation,but also can act as a fluorescence colorimetric detection probe of pH value.