Abstract Here we report a liquid-phase, bottom-up synthesis of photoluminescent colloidal nitrogen-doped graphene quantum dots (NGQDs) under ambient conditions using atmospheric-pressure microplasmas. The nucleation, growth, and simultaneously N doping of GQDs were achieved using a single plasma-liquid process. The as-synthesized NGQDs showed a 6.39 nm averaged diameter with a narrow size distribution and room-temperature excitation-dependent photoluminescence with a quantum efficiency up to 30%. The stable colloidal NGQDs with polar nitrogen-doping configurations and oxygen-containing functional groups on surfaces exhibited protonation/deprotonation properties under the pH value ranging from 1.25 to 13.56 and can be used for broad-range pH detection. Our study not only provides a simple, scalable, and environmental-friendly method to synthesize NGQD under ambient condition but also the fundamental understanding of pH detection using NGQDs.

中文翻译：

---

用于宽范围荧光 pH 传感器的微等离子体使能的胶体氮掺杂石墨烯量子点

摘要 在这里，我们报告了使用大气压微等离子体在环境条件下液相、自下而上合成光致发光胶体掺氮石墨烯量子点 (NGQD)。GQDs 的成核、生长和同时 N 掺杂是使用单一的等离子体 - 液体工艺实现的。合成后的 NGQD 平均直径为 6.39 nm，具有窄的尺寸分布和室温激发依赖性光致发光，量子效率高达 30%。具有极性氮掺杂构型和表面含氧官能团的稳定胶体 NGQD 在 1.25 至 13.56 的 pH 值范围内表现出质子化/去质子化特性，可用于宽范围的 pH 检测。我们的研究不仅提供了一个简单的、可扩展的、