Although a number of methods to perform assays of tetracyclines using fluorescent probes have been reported, approaches for discriminating and detecting tetracyclines are few. Herein, bright-blue fluorescent carbon dots (CDs) with a quantum yield (QY) of up to ∼27.9% were hydrothermally synthesized using tobacco as the carbon source. Importantly, the as-prepared carbon dots were employed as a fluorescent probe, enabling selective differentiation of three tetracyclines using a test strip and the related quantitative detection. Towards the mechanism, three kinds of tetracyclines showed different interactions with the CDs, leading to variations in their fluorescence emissions. To be specific, the fluorescence of CDs was quenched by tetracycline (TC) without a fluorescence shift (Em = 440 nm), which was caused by an inner filter effect rather than a change in the energy band gap. Moreover, the introduction of chlorotetracycline (CTC) resulted in a blue shift (Em = 415 nm) of the fluorescence of the CD; this phenomenon was induced by the enlarged energy band gap. The CDs also responded to oxytetracycline (OTC), and their corresponding fluorescence experienced a red shift (Em = 500 nm) due to the narrowed band gap. Consequently, a visual detection strategy for three tetracyclines has been proposed based on the quantitative evaluation of TC, OTC, and CTC concentrations in broad range from 6 × 10⁻⁶ to 4 × 10⁻⁹ M, 2 × 10⁻⁶ to 2 × 10⁻⁸ M, and 2 × 10⁻⁷ to 2 × 10⁻⁸ M, respectively. Moreover, we have successfully applied the current CDs for visually distinguishing the three tetracyclines on a test strip on the basis of CDs exhibiting three types of fluorescence (weak-blue, navy-blue, and chartreuse).

中文翻译：

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来自烟草的碳点，用于在视觉上区分和检测三种四环素†

尽管已经报道了使用荧光探针进行四环素测定的多种方法，但是用于区分和检测四环素的方法却很少。本文中，以烟草为碳源水热合成了量子产率（QY）高达〜27.9％的亮蓝色荧光碳点（CDs）。重要的是，将所制备的碳点用作荧光探针，从而可以使用试纸条和相关的定量检测方法选择性区分三种四环素。在机理上，三种四环素与CD的相互作用不同，导致其荧光发射发生变化。具体来说，CD的荧光被四环素（TC）猝灭，没有荧光位移（Em = 440 nm），这是由内部滤波器效应引起的，而不是由能带隙的变化引起的。此外，氯四环素（CTC）的引入导致CD的荧光发生蓝移（Em = 415 nm）。这种现象是由能带隙的扩大引起的。CD也对土霉素（OTC）有反应，由于带隙变窄，它们相应的荧光发生红移（Em = 500 nm）。因此，在定量评估TC，OTC和CTC浓度范围为6×10的基础上，提出了三种四环素的视觉检测策略。CD也对土霉素（OTC）有反应，由于带隙变窄，它们相应的荧光发生红移（Em = 500 nm）。因此，在定量评估TC，OTC和CTC浓度范围为6×10的基础上，提出了三种四环素的视觉检测策略。CD也对土霉素（OTC）有反应，由于带隙变窄，它们相应的荧光发生红移（Em = 500 nm）。因此，在定量评估TC，OTC和CTC浓度范围为6×10的基础上，提出了三种四环素的视觉检测策略。^分别为-6至4×10 ^-9 M，2×10 ^-6至2×10 ^-8 M和2×10 ^-7至2×10 ^-8M。此外，我们已经成功地将当前的CD用于显示三种荧光类型（弱蓝，海军蓝和黄绿色）的CD上，从而在视觉上区分试纸上的三个四环素。