We reported Eu(III) functionalized carbon dots (CDs-Eu) as a novel ratiometric fluorescent probe for point-of-care testing (POCT) of dipicolinic acid (DPA), a biomarker of anthrax. The probe was synthesized simply by coordination interaction between Eu(III) ions and the CDs with carboxyl and amino groups. Upon addition of DPA, the intrinsic red luminescence of Eu(III) ions can be sensitized due to the presence of energy transfer when DPA chromophore coordinated with Eu(III) ions. The fluorescence peaking at 530 nm as a reference remained essentially constant, leading to ratiometric fluorescence response toward DPA. This approach exhibited a linearity range from 0.5 nM to 5 μM and a detection limit of 0.8 nM. More Importantly, the combination of probe-based test paper and smartphone provided a convenient approach for visual POCT of DPA with a detection limit of 67 nM, which was lower than other reported test paper for DPA detection. The color of fluorescence gradually changed from green to red as the DPA increases, which can be captured by a smartphone and further quantitatively analyzed with a built-in Color Analyzer App. The satisfactory result of detecting DPA accurately and reliably in real samples by the test paper certified its practicality in POCT of DPA.

我们报告了Eu（III）功能化的碳点（CDs-Eu）作为新型比率荧光探针，用于检测炭疽病的生物标志物二吡啶甲酸（DPA）的即时检验（POCT）。该探针是通过Eu（III）离子与带有羧基和氨基的CD的配位相互作用简单地合成的。添加DPA时，当DPA生色团与Eu（III）离子配位时，由于存在能量转移，因此Eu（III）离子的固有红色发光可以被敏化。作为参考，在530 nm处的荧光峰值保持基本恒定，从而导致对DPA的荧光定量响应。该方法的线性范围为0.5 nM至5μM，检测极限为0.8 nM。更重要的是，基于探针的测试纸和智能手机的结合为DPA的视觉POCT提供了一种便捷的方法，其检测限为67 nM，这低于其他报道的DPA检测的测试纸。随着DPA的增加，荧光的颜色从绿色逐渐变为红色，可以由智能手机捕获，并使用内置的颜色分析器应用程序进一步进行定量分析。试纸准确，可靠地检测出DPA的令人满意的结果证明了其在DPA的POCT中的实用性。