Sustained high-temperature fluorescence in bulk carbon nitride enabled by K/Na dual-alkali regulation
摘要
Rare-earth-free carbon nitride luminescent materials that remain bright during prolonged high-temperature operation are highly desirable for harsh-environment optoelectronics, yet their emission is often limited by thermally activated non-radiative pathways and accelerated weathering under ultraviolet (UV) irradiation. Here, we report a K/Na co-regulated carbon nitride (K/Na-CN) prepared via a solid-state route. Temperature-dependent photoluminescence (PL) measurements show a well-preserved emission band with only limited chromaticity deviation over a broad heating window. Under vacuum, K/Na-CN retains ~ 50% of its initial PL intensity at 300 °C and maintains ~ 70% PL intensity after holding at 300 °C for 60 min. During UV aging (0–192h), the powder PL intensity increases to ~ 1.7–1.8 × at 48h, reaches a maximum of ~ 2.4 × at 144h, and remains at ~ 1.5 × after 192h, which indicates robust emissive states despite irradiation-driven defect-state rebalancing. After incorporation of K/Na-CN into PMMA to prepare transparent luminescent plates, at an optimized loading, the composite shows the best dispersion and maintains high optical clarity (visible transmittance > 80% and reflectance < 12%), while providing improved UV service behavior. After UV exposure, the composite emission exhibits a systematic blue shift from ~ 530 nm (0h) to ~ 500 nm (48 h) and ~ 480 nm (96h). Meanwhile, the weak intensity gap is consistent with bulk particle aggregation and inner-filter effects limiting the effective radiative gain. Overall, K/Na-CN combines sustained high-temperature fluorescence with UV-tolerant performance in both powders and transparent polymer composites, offering a practical platform for long-service luminescent components operating under heat and irradiation stress.