ScholarWorks@숙명여자대학교

초록

In this study, we report the synthesis of red-emissive carbon dots (PCU-CDs) with an emission peak near 650 nm, achieved through the surface functionalization of citric acid/urea-derived carbon cores with polyethylenimine (PEI). In addition to intrinsic oxygen-induced states (OISs), the incorporation of amine-rich PEI significantly enhances long-wavelength emission by forming and stabilizing nitrogen-induced intragap states (NISs), while also introducing a new blue emissive state attributed to PEI-derived surface functionalities. A series of mechanistic investigations, including photoluminescence (PL) spectroscopy, pH-dependent quenching, model compound comparisons, and time-resolved PL were conducted to dissect the origins of the excitation-dependent multicolor emission. The results reveal three distinct emissive states: NISs, OISs, and PEI-related states arising from through-space interactions. Notably, the PCU-CDs exhibited a high PL quantum yield of 71.13 % under 570 nm excitation, primarily governed by NIS-related radiative pathways. Furthermore, the PCU-CDs were successfully incorporated into a freestanding polymer film that demonstrated efficient spectral conversion from blue to red light when excited at 480 nm. The chromaticity coordinates of the resulting emission, (0.613, 0.386), highlight the applicability of PCU-CDs as cadmium-free, environmentally benign alternatives for use in quantum dot-based light-emitting displays and other optoelectronic applications.

키워드