The fluorescence properties of nitrogen-doped carbon dots by microwave green approaches

Carbon dots (CDs), as a class of zero-dimensional carbon nanomaterials, have exceptional fluorescence performance and a broad spectrum of applications. Everyone knows that heteroatom doping is advantageous for regulating electronic states and transition channels in carbon dot systems. Thus, CDs exhibit different properties under different experimental methods or doped conditions. To clarify the role of extrinsic factors, doped carbon dots with excellent fluorescence properties are synthesized in this paper, and the effects of pH level and microwave heating time on doped CDs' photoluminescence (PL) are thoroughly investigated. Utilizing a pyrolysis mixture of Ascorbic acid and NH3H2O, the nitrogen-doped carbon dots (N-CDs) linked by N elements are synthesized. The impact of surface functions on these nanomaterials' optical characteristics is examined using XPS and PL spectroscopic techniques. The research found that when the duration of microwave heating increases, the tiny molecules become too dehydrated and carbonized at elevated temperatures. Simultaneously, reducing oxygen-containing functional groups on the surface of carbon dots causes the weakening of fluorescence intensity. Furthermore, with the increase of pH value, the accumulation of excessive -OH in the solution leads to the fluorescence weakening of N-CDs, leading to a steady rise and then a decrease in the luminescence intensity. This research has particular scientific significance for the fluorescence regulation of N-CDs and its application.