Hexavalent chromium (Cr (VI)) is highly carcinogenic to humans. Ascorbic acid (AA) deficiency can be hazardous to health. And the dual-effect fluorescence detection of them is an important research topic. Carbon dots (CDs) based on cellulose are excellent candidates for the fluorescence probes due to their low cost and environmental friendliness. But most of them exhibit shortwave emission, small Stokes shift and poor fluorescence performance, all of which limit their use. Therefore, there is an urgent need for cellulose CDs with longer emission wavelengths and larger Stokes shifts in dual-effect fluorescence detection of Cr (VI) and AA. Under optimal conditions (180 °C, 12 h), we prepared cellulose-based nitrogen-doped carbon dots (N-CDs) by a simple one-step hydrothermal process, which display longer emission wavelengths (ex: 370 nm, em: 510 nm), larger Stokes shifts (140 nm) and high fluorescence quantum yield (QY: 19.27 %). The continuous “turn-off” and “turn-off-on” fluorescence detection platforms were constructed based on the internal filtering effect (IFE) between Cr and N-CDs, and Cr reduced to Cr by AA at pH = 6. The platform has been successfully simultaneous detect Cr (VI) and AA with a wide range of 0.01–40 μM and 0.1–100 μM. And the lowest limits of detection (LOD) are 0.0303 μM and 0.072 μM, respectively. In the presence of some other metals, non-metal ions and water-soluble acids in the fruits, this fluorescent platform can demonstrate a high level of interference immunity. This represents the first yellow-green cellulose-based N-CDs with large Stokes shift for dual-effect detection of Cr (VI) and AA in real water samples and fresh fruits. The fluorescence detection platform has the advantage of low volume detection. Less than 2 mL of sample is required for testing and results are available in <5 min. This method is rare and supply a novel idea for the quantitative monitoring of Cr (VI) and AA.

中文翻译：

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具有大斯托克斯位移的纤维素基黄绿色发射碳点作为 Cr (VI) 和 AA 双效检测的有效“关闭”荧光平台


六价铬（Cr(VI)）对人类具有高度致癌性。抗坏血酸 (AA) 缺乏可能危害健康。其中它们的双效荧光检测是一个重要的研究课题。基于纤维素的碳点（CD）由于其低成本和环境友好性而成为荧光探针的绝佳候选者。但它们大多表现出短波发射、小斯托克斯位移和较差的荧光性能，这些都限制了它们的应用。因此，在Cr(VI)和AA的双效荧光检测中迫切需要具有更长发射波长和更大斯托克斯位移的纤维素CD。在最佳条件下（180°C，12小时），我们通过简单的一步水热过程制备了基于纤维素的氮掺杂碳点（N-CD），其显示出更长的发射波长（例如：370 nm，em：510） nm）、更大的斯托克斯位移（140 nm）和高荧光量子产率（QY：19.27 %）。基于 Cr 和 N-CD 之间的内部过滤效应 (IFE)，并在 pH = 6 时通过 AA 将 Cr 还原为 Cr，构建了连续“关闭”和“关闭开启”荧光检测平台。已成功同时检测 Cr (VI) 和 AA，检测范围为 0.01–40 μM 和 0.1–100 μM。最低检测限 (LOD) 分别为 0.0303 μM 和 0.072 μM。当水果中存在一些其他金属、非金属离子和水溶性酸时，该荧光平台可以表现出高水平的抗干扰性。这是第一个具有大斯托克斯位移的黄绿色纤维素基 N-CD，可用于实际水样和新鲜水果中 Cr (VI) 和 AA 的双效检测。该荧光检测平台具有低体积检测的优点。 测试所需的样品少于 2 mL，并且 <5 分钟内即可获得结果。该方法罕见，为Cr(VI)和AA的定量监测提供了新思路。