Thermal control of oxygen-induced emission states in carbon dots for indoor lighting applications

Understanding the role of heteroatoms in carbon dots (CDs) has been recognized as a critical factor for the design and engineering of their optical properties. Oxygen is one of the most prevalent heteroatom defects in CDs; however, its effects on the optical properties are still unclear because it has not been possible to precisely control the degree of oxidation of CDs. Here, we report the synthesis of CDs in a controlled process that allows thermal control of the oxygen content using benzyl alcohol as an oxidizing solvent. The results suggest that oxygen-induced defects reduce the optical band gap of CDs, and their emission is red-shifted from blue (428 nm) to red (628 nm). The photoexcited charge-carrier dynamics of the CDs were thoroughly studied using transient absorption spectroscopy and fluorescence decay measurements. Furthermore, the bright multicolored emission of our CDs renders them suitable for sun-like panchromatic indoor lighting applications. We believe that these new insights into oxygen-induced defects in CDs will result in significant progress in their practical use.