Deep-Blue and Narrowband-Emitting Carbon Dots from a Sustainable Precursor for Random Lasing

Deep-blue (DB) emitters that feature high photoluminescence quantum yield (PLQY) and narrow spectral bandwidth are desired for a variety of optoelectronic applications, particularly for lighting, illumination, and lasing. Currently favored DB emitters constitute quantum dots comprising cadmium or lead and organic compounds derived from petroleum, but they suffer from toxicity and sustainability issues. Here, we report the solvothermal synthesis of DB-emitting carbon dots (DB-CDs) using bioderivable phloroglucinol as the sole starting material, which exhibit a peak emission wavelength of 403 nm, narrow spectral full width at half-maximum of 35 nm, and high PLQY of 61% in ethanol. The DB-CDs with a planar structure are demonstrated to comprise distinct graphene segments in a polyether-cross-link network, with the former functioning as the fluorophore. The application merit of the DB-CDs is exemplified by their implementation as the gain medium in a random laser device, which exhibits a threshold optical power density of 40.5 kW cm^-2. This study thus demonstrates a path toward efficient and sustainable deep-blue emitters, which can be exploited in practical applications.