AbstractCarbon quantum dots (CQDs) doped with phosphorus and nitrogen were prepared via a hydrothermal method starting from citric acid, urea and phosphoric acid in dimethylformamide solution. The size, morphology, surface composition, energy levels, and optical properties of the CQDs were characterized. They show both green down-conversion and up-conversion fluorescence. Ferric ions (Fe3+) are found to quench the fluorescence. Cyclic voltammetry was used to identify the HOMO and LUMO levels of the doped CQDs. The quenching mechanism, as confirmed by energy level calculations and absorption spectra, can be attributed to the selective coordination of Fe3+ by the surface functional groups on the CQDs. This facilitates the photo-induced electron transfer from the CQDs to the d orbitals of Fe3+. The CQDs are shown to be viable fluorescent probes for determination of Fe3+ with high selectivity and sensitivity. The assay has a linear response in the 0.1 μM to 0.9 μM Fe3+ concentration range and a 50 nM as limit of detection (at a S/N ratio of 3). Graphical abstractFluorescence probe for determination of ferric ions based on carbon quantum dot quenching via chelation facilitate photo-electron transfer.

中文翻译：

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磷和氮掺杂的碳量子点的溶剂热合成作为铁（III）的荧光探针

摘要 以柠檬酸、尿素和磷酸为原料，在二甲基甲酰胺溶液中采用水热法制备了磷和氮掺杂的碳量子点（CQDs）。表征了 CQD 的尺寸、形态、表面组成、能级和光学性质。它们显示绿色下转换和上转换荧光。发现铁离子 (Fe3+) 可以淬灭荧光。循环伏安法用于鉴定掺杂 CQD 的 HOMO 和 LUMO 能级。通过能级计算和吸收光谱证实，淬灭机制可归因于 CQD 表面官能团对 Fe3+ 的选择性配位。这有助于光诱导电子从 CQD 转移到 Fe3+ 的 d 轨道。CQD 被证明是一种可行的荧光探针，可用于以高选择性和灵敏度测定 Fe3+。该测定在 0.1 μM 至 0.9 μM Fe3+ 浓度范围内具有线性响应，检测限为 50 nM（S/N 比为 3）。基于碳量子点猝灭通过螯合促进光电子转移的用于测定三价铁离子的图形摘要荧光探针。