Carbon quantum dot/carbon dot (CD) exhibiting sustained photoluminescence at longer wavelengths in aqueous solution is difficult to prepare, but has enormous potential in biomedical applications. For the first time, we report the magnesium(II) selective fluorescence enhancement of a red-light emitting anthrarufin and boric acid-derived CD in aqueous solution for direct evaluation of creatine kinase (CK) enzyme activity. The CD displayed visually detectable, intense red fluorescence only in the presence of magnesium ion (Mg²⁺) at physiological pH value when irradiated with an ultraviolet (UV) source. Concurrently, a significant increase in steady-state fluorescence intensity and fluorescence lifetime was documented. A time-dependent density functional theory (TD-DFT) analysis displayed a bathochromic shift in UV-visible (vis) absorption, and increased oscillator strength of transition resulting from the selective chelation of Mg²⁺ with β-hydroxy keto functionality on the surface of the CD. The CD-Mg²⁺ assembly was subsequently used to conceptualize the detection of CK directly through the exploration of the differential binding affinity of Mg²⁺ with adenosine triphosphate (ATP), adenosine diphophate (ADP), and CD that is otherwise not possible with commercially available kits as of today. Thus, the report delineated here usher grandeur potential of CD for biological explorations related to Mg²⁺ or ATP sensing and monitoring of Mg²⁺-dependent enzymatic activity through a clear understanding of the chemistry.

碳量子点/碳点（CD）在水溶液中在较长波长下表现出持续的光致发光是很难制备的，但在生物医学应用中具有巨大的潜力。首次，我们报道了水溶液中用于直接评估肌酸激酶（CK）酶活性的镁（II）选择性荧光增强的红光发射蒽醌和硼酸衍生的CD。CD仅在镁离子（Mg ²⁺）在用紫外线（UV）光源照射时处于生理pH值。同时，记录了稳态荧光强度和荧光寿命的显着增加。随时间变化的密度泛函理论（TD-DFT）分析显示UV-可见光（vis）吸收发生红移，并且由于Mg ²⁺与表面上的β-羟基酮官能团的选择性螯合而增加了跃迁的振荡强度CD。随后，通过探索Mg ²⁺的差异结合亲和力，将CD-Mg ²⁺组件直接用于概念化CK的检测。与三磷酸腺苷（ATP），二磷酸腺苷（ADP）和CD结合使用，目前为止，使用市售套件无法实现。因此，在此描述的报告通过清晰地了解化学原理，将CD引入与Mg ²⁺或ATP感应和监测Mg ²⁺依赖的酶活性有关的生物学探索方面具有更大的潜力。