Environment‐Friendly <i>N</i> ‐Doped Carbon Dots for Fingerprint and High Color‐Rendering White Light‐Emitting Diode

Abstract To achieve innovative applications of carbon dots (CDs) in white light‐emitting diode (WLED) and fingerprint imprinting fields, developing luminescent stable CDs‐based solid materials is of great significance. In this study, urea was used as the nitrogen source and citric acid as the carbon source to prepare blue‐emitting CDs (b‐CDs) and green‐emitting CDs (g‐CDs) via two energy‐efficient and environment‐friendly methods: hydrothermal synthesis and microwave‐assisted synthesis. Additionally, b‐CDs and g‐CDs were combined with starch, a low‐cost, easily accessible, and eco‐friendly material, through surface hydrogen bonding to fabricate b‐CDs‐starch composites (b‐CDs@St) and g‐CDs‐starch composites (g‐CDs@St). This process effectively prevented the aggregation of CDs. The obtained composites exhibited good stability and delicate texture, holding promise as solid fluorescent materials for fingerprint imprinting. Furthermore, WLED developed using these composites demonstrate excellent color purity and luminescent performance, with a correlated color temperature (CCT) of 5033 K, color coordinates of (0.34, 0.34), and a color rendering index (CRI) of 91. This work broadens the synthetic strategies and potential applications of CDs in solid‐state fluorescent materials.