Achieving Narrow‐Band Ultraviolet Emission in Carbon Dots via “sp 2 ‐Domain Inhibitor” Strategy

ABSTRACT Despite the significant attention garnered by carbon dots (CDs) for their exceptional photoluminescence properties, the rational design of ultraviolet (UV)‐emitting CDs with high color purity remains a formidable challenge. Conventional aromatic precursors typically yield yellow to red emissive CDs due to the formation of extended sp 2 ‐domains. Herein, we propose a straightforward yet effective strategy to shift the visible emission into UV region by employing 1,2‐cyclohexanediamine (DCH) as a “ sp 2 ‐domain inhibitor”. Remarkably, by fine‐tuning the DCH content, we suppressed the orange‐colored emission ( λ max = 577 nm) and achieved an over 100‐fold enhancement of the UV emission intensity ( λ max = 295 nm). The resulting CDs exhibit not only fast decay kinetics ( τ = 1.70 ns) but also high color purity (FWHM = 31 nm) across a wide range of media. Mechanistic investigations reveal that DCH functions as a “bridging linker” that introduces sp 3 ‐C into the carbon core. More importantly, these saturated carbon atoms act as structural defects, effectively inhibiting the growth of large, planar sp 2 ‐domains. Finally, these nanoparticles were utilized as implanted UV light‐conversion materials to promote plant growth by regulating the electron transport process. This work provides a simple and effective methodology for developing high‐performance UV‐emitting nanomaterials for optoelectronic applications.