Precise regulation of the multicolor spectrum of carbon dots based on the bionic leaf vein ultrasonic microreactor

Carbon dots (CDs) are a fascinating new type of fluorescent carbon nanomaterial with excellent photoelectric properties. However, preparing long-wavelength and multicolor-emitting CDs has been challenging, limiting their large-scale applications. Fortunately, a new efficient method has been proposed to co-regulate CDs' multicolor spectra using an ultrasonic microreactor. Inspired by plant leaves, a bionic vein microchannel was designed with good fluidity and high energy transfer efficiency. The optimal microchannel structural parameters were determined after investigating the effects of fractal angle, depth-to-width ratio, and inlet angle on the flow uniformity of the microchannel using numerical simulations. The efficiency of ultrasonic energy transfer was improved by directly coupling the microreactor and the sandwich transducer to fabricate the ultrasonic microreactor. Simulation results showed that the ultrasonic microreactor's vibration resonated along the longitudinal direction, and the ultrasonic intensity of the microreactor was maximal and uniform. A high-efficiency and controllable ultrasonic microreactor system was built to synthesize the CDs in situ. The influence of the ultrasound field intensity on CDs' preparation in a microreactor was simultaneously investigated to verify the ultrasound enhancement, and the PLQY of the high-performance CDs was found to be 83.1%. The CDs' multicolor spectra from the blue to the red region can be precisely tuned by adjusting key reaction parameters such as reaction temperature, flow rate, and precursor concentration. This new method shows promising applications in lighting, display, and other fields, making CDs a versatile and exciting new material to explore.