Carbon dots (CDs) are carbon‐based fluorescent nanoparticles that can exhibit excitation‐dependent photoluminescence (PL) “tunable” throughout the entire visible range, interesting for optoelectronic and imaging applications. The mechanism underlying this tunable emission remains largely debated, most prominently being ascribed to dot‐to‐dot variations that ultimately lead to excitation‐dependent ensemble properties. Here, single‐dot spectroscopy is used to elucidate the origin of the excitation‐dependent PL of CDs. It is demonstrated that already single CDs exhibit excitation‐dependent PL spectra, similar to those of the CD ensemble. The single dots, produced by a facile one‐step synthesis from chloroform and diethylamine, exhibit emission spectra with several characteristic peaks differing in emission peak position and spectral width and shape, indicating the presence of distinct emission sites on the CDs. Based on previous work, these emission sites are related to the sp² subregions in the carbon core, as well as the functional groups on the surface. These results confirm that it is possible to integrate and engineer different types of electronic transitions at the nanoscale on a single CD, making these CDs even more versatile than organic dyes or inorganic quantum dots and opening up new routes toward light‐emission engineering.

中文翻译：

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单碳点的激发相关光致发光

碳点（CD）是基于碳的荧光纳米粒子，在整个可见光范围内都可以表现出与激发有关的光致发光（PL）“可调”，这对于光电和成像应用而言非常有趣。可调发射的基本机制仍然存在争议，最主要的是归因于点到点的变化，这些变化最终导致依赖于激发的整体性能。在这里，单点光谱法用于阐明CD的依赖于激发的PL的起源。事实证明，已经存在的单个CD表现出与激发有关的PL光谱，类似于CD集合中的激发光谱。由氯仿和二乙胺轻松一步合成得到的单个点显示的发射光谱具有几个特征峰，这些特征峰的发射峰位置，光谱宽度和形状各不相同，表明CD上存在明显的发射点。根据以前的工作，这些排放位点与碳核中的²个子区域以及表面上的官能团。这些结果证实，可以在一张CD上集成和工程化纳米尺度上不同类型的电子跃迁，从而使这些CD比有机染料或无机量子点具有更多的用途，并开辟了通往发光工程的新途径。