A fluorescent nanoprobe based on nitrogen-doped carbon dots (N-CDs) with green fluorescent emission have been fabricated through a facile one-step hydrothermal treatment using catechol and triethylene tetramine as precursors. The obtained N-CDs with excellent luminescent properties and superior biocompatibility have been applied for the development of a bifunctional sensor for the detection of Fe³⁺ and ascorbic acid (AA). Fe³⁺ that are tightly chelating the surface of N-CDs can induce fluorescence (FL) quenching of N-CDs through photo-induced electron transfer (PET). Meanwhile, the addition of AA serves to shelter the CDs effectively from being quenched by Fe³⁺ due to AA, as an antioxidant, enable easy-conversion of Fe³⁺ to reduced states (i.e. Fe³⁺ and Fe²⁺). The N-CDs are used as a facile and label-free “on-off-on” fluorescent nanoprobe for the determination of Fe³⁺ and AA with detection limits of 58.82 nM and 0.236 µM with the corresponding linear ranges of 25–200 µM and 25–300 µM, respectively. According to this phenomenon, an “AND” logic gate based on the novel N-CDs has been constructed. As-prepared N-CDs with negligible toxicity and perfect biocompatibility were expanded for cellular imaging and sensing Fe³⁺ and AA in living cell, which enlarges the application range of the N-CDs. Most importantly, the as-constructed fluorescent sensing system was successfully applied to detection of Fe³⁺ in tap water and the analyses of AA in fresh fruits with satisfactory results.

通过以儿茶酚和三亚乙基四胺为前体的一步式水热处理，制备了基于氮掺杂碳点（N-CD）和绿色荧光发射的荧光纳米探针。所获得的具有优异发光性能和优异生物相容性的N-CD已被用于开发用于检测Fe ³⁺和抗坏血酸（AA）的双功能传感器。紧密螯合N-CD表面的Fe ³⁺可以通过光致电子转移（PET）诱导N-CD的荧光（FL）猝灭。同时，添加AA可以有效防止CD受到Fe ^3+的淬灭，因为AA是一种抗氧化剂，使Fe ³⁺易于转化还原态（即Fe ³⁺和Fe ²⁺）。N-CD用作简便，无标签的“开-关-开”荧光纳米探针，用于检测Fe ³⁺和AA，检测限为58.82 nM和0.236 µM，相应的线性范围为25–200 µM和25–300 µM。根据该现象，已经构造了基于新型N-CD的“与”逻辑门。制备的具有可忽略的毒性和完美的生物相容性的N-CDs被扩展用于细胞成像和传感活细胞中的Fe ³⁺和AA，从而扩大了N-CDs的应用范围。最重要的是，如此构造的荧光传感系统已成功应用于检测Fe ³⁺ 在自来水中进行分析以及对新鲜水果中的AA进行分析，结果令人满意。