Highly efficient regulation strategy of fluorescence emission wavelength via designing the structure of carbon dots

Multicolor carbon dots (CDs) possess tremendous potential applications, especially in optoelectronic devices. However, further applications of multicolor light-emitting diode (LED) have been constrained due to the very limited researches concerning the wavelength control mechanism of multicolor CDs. In this work, through theoretical calculation and experimental verification, the regulatory effects of sp2 conjugated domain on the fluorescence wavelength of CDs were explored. Through the regulation of the structure size and the introduction of amide bonds, four kinds of structures were designed in density functional theory (DFT) calculation to explore the influence of sp2 conjugated domain on the fluorescence wavelength of CDs. Using thiourea and p-phenylenediamine as the precursors and regulating the reaction solvents, multicolor CDs with blue, green, and red fluorescence emission were prepared to experimentally verify the emission mechanism. It was confirmed that the increasing structure size and the introduction of amide bond would induce an increasing size of the sp2 conjugated domain, leading to the red shift of the CDs fluorescence wavelength. Furtherly, in order to suppress the self-quenching performance, the CDs@polyvinylpyrrolidone (CDs@PVP) fluorescent film possessing bright solid-state fluorescence was constructed for a better application in light-emitting diodes. The approach provided an effective strategy to realize the programmed regulation on the fluorescence wavelength of CDs, offering us wide potential applications of CDs in the photoelectric device fields.