Solid assemblies of carbon quantum dots (CQDs) are important for diverse applications including LEDs, solar cells, and photosensors; their optical and electrical properties have not been explored yet. Herein, we used amphiphilic CQDs synthesized from citric acid and thiourea by a solvothermal method to fabricate CQD solid films. Optical properties of CQDs studied by UV-Vis and photoluminescence spectroscopies indicate that CQDs possess three different emission centers at 425 nm, 525 nm, and 625 nm originating from C sp² states, N-states, and S-states, respectively. In a solid state, π-π stacking quenched the blue emission, while the red emission increased. Importantly, CQD films exhibited excitation independence, which is important to design solid-state lighting applications.

中文翻译：

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碳量子点固体的激发无关发射

碳量子点（CQD）的固体组件对于包括LED，太阳能电池和光电传感器在内的各种应用非常重要。它们的光学和电学性质尚未被探索。在本文中，我们使用由溶剂热法由柠檬酸和硫脲合成的两亲性CQD制备CQD固体膜。通过UV-Vis和光致发光光谱学研究的CQD的光学性质表明，CQD在425 nm，525 nm和625 nm处分别具有三个不同的发射中心，分别来自C sp ²状态，N状态和S状态。在固态π - π堆积使蓝色发射淬灭，而红色发射增加。重要的是，CQD膜具有激发无关性，这对设计固态照明应用很重要。