Carbon dots (CDs) or CDs/polymer composites have been applied in numerous fields. Here, novel CDs were synthesized by carbonization of egg yolk, and characterized by TEM, FTIR, XPS and photoluminescence spectra. The CDs were found to be approximate sphere in shape with an average size of 4.46 ± 1.17 nm, and emitted bright blue photoluminescence under UV irradiation. The photoluminescence of CDs was found selectively quenched by Fe³⁺ in a linear manner in the range of 0.05–0.45 mM, meaning they could be applied for Fe³⁺ detection in solution. Moreover, the CDs could be uptaken by HepG2 cells to exhibit bright blue photoluminescence. The intensity could reflect the level of intracellular Fe³⁺, indicating they could be further used for cell imaging and intracellular Fe³⁺ monitoring. Next, dopamine was polymerized on the surface of CDs to obtain the polydopamine (PDA)-coated CDs (CDs@PDA). We found PDA coating could quench the photoluminescence of CDs via inner filter effect, and the degree of quenching was linearly related to the logarithm of DA concentration (Log C_DA). Also, the selectivity experiment indicated the method had a high selectivity for DA over a number of possible interfering species. This indicated the CDs in combination with Tris buffer could be potentially applied as the assay kit of dopamine. At last, the CDs@PDA exhibited excellent photothermal conversion capability, and they could efficiently kill HepG2 cells under NIR laser irradiation. Overall, the CDs and CDs@PDA in this work exhibited many excellent advantages, and could be potentially used for multi-applications, such as Fe³⁺ sensor in solution and cellular, cell imaging, dopamine assay kit, as well as photothermal agents for cancer therapy.

碳点（CD）或CD/聚合物复合材料已应用于许多领域。在此，通过蛋黄碳化合成了新型 CD，并通过 TEM、FTIR、XPS 和光致发光光谱进行了表征。CDs呈近似球形，平均尺寸为4.46±1.17 nm，在紫外照射下发出亮蓝色光致发光。^{发现 CD 的光致发光在 0.05–0.45 mM 范围内被 Fe 3+}以线性方式选择性猝灭，这意味着它们可用于溶液中的Fe ^3+检测。此外，CD 可以被 HepG2 细胞摄取，呈现亮蓝色光致发光。^{其强度可以反映细胞内Fe 3+}的水平，表明它们可以进一步用于细胞成像和细胞内 Fe ³⁺监测。接下来，将多巴胺聚合在CD的表面上以获得聚多巴胺(PDA)涂覆的CD(CDs@PDA)。我们发现PDA涂层可以通过内滤效应猝灭CD的光致发光，并且猝灭程度与DA浓度的对数（Log C _DA）。此外，选择性实验表明该方法对 DA 对许多可能的干扰物质具有较高的选择性。这表明CDs与Tris缓冲液的组合有可能用作多巴胺的检测试剂盒。最后，CDs@PDA表现出优异的光热转换能力，在近红外激光照射下可以有效杀死HepG2细胞。总体而言，本工作中的CD和CDs@PDA表现出许多优异的优点，并且具有潜在的多种应用潜力，例如溶液和细胞中的Fe 3+^传感器、细胞成像、多巴胺测定试剂盒以及光热试剂癌症治疗。