Water pollution originating from heavy metals has shown great impacts on the ecological environment and human health due to their extremely low biodegradability. Hexavalent chromium Cr(VI), as one harmful heavy metal with strong oxidation, high biological permeability, and high carcinogenicity, is becoming an increasingly serious threat to human health. Therefore, conveniently but accurately, monitoring the Cr(VI) level in water to maintain its normal level and ensuring the stability of the ecosystem and human health become very valuable. However, most of these heavy metal sensors reported are turn-off type single-emission sensors. In this work, a ratiometric fluorescence/colorimetry/smartphone triple-mode turn-on optical sensor for Cr(VI) was developed based on a multifunctional metal–organic framework platform. The detection limits for these three mutual verification modes were only 1.28, 4.89, and 68.4 nM, respectively. Additionally, the color changes of the detection system under sunlight can also be observed directly by the naked eye. The accuracy and practicability of this multimode sensor were further proved by the detection of Cr(VI) in actual water and seawater samples, and the recovery rate ranged from 97.308 to 104.041%.

中文翻译：

---

用于选择性、灵敏检测淡水和海水中有害重金属 Cr(VI) 的多模光学传感器

重金属水污染由于其极低的生物降解性，对生态环境和人类健康造成了巨大影响。六价铬Cr(VI)作为一种氧化性强、生物渗透性高、致癌性强的有害重金属，日益严重威胁人类健康。因此，方便而准确地监测水中Cr(VI)含量以维持其正常水平，确保生态系统的稳定和人类健康变得非常有价值。然而，报道的这些重金属传感器大多数是关断型单发射传感器。在这项工作中，基于多功能金属有机框架平台，开发了一种用于 Cr(VI) 的比率荧光/比色/智能手机三模式开启光学传感器。这三种相互验证模式的检测限分别仅为1.28、4.89和68.4 nM。另外，检测系统在阳光下的颜色变化也可以通过肉眼直接观察到。通过对实际水和海水样品中Cr(VI)的检测进一步证明了该多模式传感器的准确性和实用性，回收率在97.308%~104.041%之间。