Intermolecular naphthylamine cyclization-based synthesis of bandgap-modulated carbon dots for multicolor light-emitting diodes

Owing to their tunable optical properties, N-doped carbon dots (CDs) have a broad scope of optoelectronic applications. However, the difficulty of precisely controlling nitrogen incorporation limits our understanding of its impact on CD electronic structure and emission behavior. To address this gap, N-doped CDs with tunable bandgaps are herein synthesized via the solvothermal carbonization of 1-naphthylamine in the presence of a controlled amount of nitric acid to obtain single-source emitters with two distinct emission wavelengths. The amount of nitric acid determines the extent of nitrogen incorporation through the intermolecular cyclization of 1-naphthylamine and, hence, the proportions of pyrrolic/pyridinic N-heterocycles (red emission, similar to 600 nm) and polycyclic aromatic hydrocarbons (blue emission, similar to 400 nm). For a practical utility demonstration, the prepared N-doped CDs are used to fabricate high-color-purity multicolor light-emitting diodes. By establishing a correlation between nitrogen incorporation modes and photophysical properties, this study paves the way for the rational design of advanced N-doped CDs for next-generation optoelectronic devices.