超声法制备碳量子点过程简单, 成本低廉, 不易产生二次污染, 应用前景广泛。 为优化超声法制备碳量子点的各工艺参数, 制备了关键工艺参数不同的碳量子点样品, 测试其发射与激发光谱, 分析了量子点浓度, 溶剂种类, 辅助剂种类、 浓度, 超声功率、 时间等参数对碳量子点发光性能影响。 结果表明超声法制备的碳量子点具有激发光波长依赖性, 发射峰位置随激发波长的变化而发生明显改变; 碳量子点浓度增加, 发光强度由于非辐射能量传递和团聚作用, 先增大后减小; 由于溶剂效应, 碳量子点在乙醇中比在水中发光强度更强, 波长更短, 且浓度越大时波峰移动越明显; 相比盐酸, 以NaOH为辅助剂制备的碳量子点表面钝化程度高, 发光强度强; 增加辅助剂NaOH浓度可提高量子点表面钝化程度, 增大发光强度; 同等时间下增加超声功率或同等功率下适量增加超声时间, 可制备更多的碳量子点样品, 但超声时间过长, 碳量子点容易发生团聚猝灭现象。 以上影响因素分析为超声法制备碳量子点的工艺参数优化提供了理论基础, 有利于碳量子点大规模低成本的生产应用。

Ultrasonic synthesis of carbon dots has broad application prospects because of its simple process, low cost and less secondary pollution. To optimize the technological parameters of ultrasonic synthesis, carbon dots samples were prepared with different critical process parameters. Emission and excitation spectra were measured, and the effects of quantum dot concentration, types of solvent, auxiliary agent type and concentration, and ultrasonic power and time on luminescence properties of carbon dots were analyzed. The results showed that carbon dots prepared by ultrasonic had a excitation wavelength dependence, and their emission peaks significantly changed with the excitation wavelengths. When carbon dots concentrations increased, their Luminous intensities first increased and then decreased because of the radiation energy transfers and quantum dots reunion. Due to solvent effect, luminous intensities of carbon dots in ethanol were stronger than that in water, and wavelengths of carbon dots in ethanol were shorter than that in water. And the greater the concentrations of carbon dots were, the more obvious the wavelengths of emission spectra moved. Compared with hydrochloric acid, carbon dots prepared with sodium hydroxide as adjuvant had a better surface passivation and stronger luminous intensities. Besides, surface passivation of carbon dots could be improved by increasing the NaOH concentration, and much more carbon dots could be obtained by increasing ultrasonic power or time appropriately, but if the ultrasonic time was too long, carbon dots were prone to reunite quenching. The above analysis of influencing factors provides a theoretical basis for parameter optimization of carbon quantum dots prepared by ultrasonic, which is conducive to the mass production and application of carbon quantum dots at a low cost.