Graphene quantum dots (GQDs) are emerging luminescent nanomaterials for energy, bioimaging, and optoelectronic applications. However, unlike conventional fluorophores, GQDs contain multiple emissive centers that result in a complex interaction with external electromagnetic fields. Here we utilize core–shell plasmonic nanoparticles to simultaneously enhance and modulate the photoluminescence (PL) intensities and spectral profiles of GQDs. By analyzing the spectral profiles, we show that the emissive centers are highly influenced by the proximity to the metal particles. Under optimal spacer thickness of 25 nm, the overall PL displays a four-fold enhancement compared with a pristine GQD. However, detailed lifetime measurements indicate the presence of midgap states that act as the bottleneck for further enhancement. Our results offer new perspectives for fundamental understanding and new design of functional luminescent materials (e.g., GQDs, graphene oxide, carbon dots) for imaging, sensing, and light harvesting.

中文翻译：

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核-壳等离子纳米粒子对石墨烯量子点中多个发射中心的增强效率的调节

石墨烯量子点（GQD）是新兴的发光纳米材料，用于能源，生物成像和光电应用。但是，与常规的荧光团不同，GQD包含多个发射中心，这些发射中心导致与外部电磁场的复杂相互作用。在这里，我们利用核-壳等离激元纳米粒子同时增强和调节GQD的光致发光（PL）强度和光谱轮廓。通过分析光谱轮廓，我们表明，发射中心受与金属颗粒的接近程度的影响很大。在25 nm的最佳隔离层厚度下，与原始GQD相比，整个PL表现出四倍的增强。但是，详细的寿命测量表明存在中间能隙状态，它们是进一步增强的瓶颈。