A Ratiometric Multimode Optical Sensor for Highly Selective and Sensitive Detection of Harmful Heavy Metal Hg ²⁺ in Freshwater and Seawater

Heavy metal pollution has become one of the major threats to water environment security and human health, due to its extremely high toxicity and low biodegradability. The exploration of efficient recognition methods for accurate but convenient monitoring of one of the most widely distributed heavy metal Hg²⁺, level in water has attracted widespread attention all over the world. In this work, a novel ratiometric fluorometry/ratiometric absorbance-based colorimetry/ratiometric smartphone-based RGB analysis platform Al-TCPP@RBH, for Hg²⁺ detection was conveniently constructed based on a multifunctional MOF platform. This type of multimode ratiometric sensing platform for convenient but accurate Hg²⁺ sensing with a multimode optical ratiometric signal has not been exploited so far. The detection limits of these three mutually corroborated sensing modes were 9.9 nM, 30 nM, and 27 nM, respectively. In addition, the practicability and accuracy of this multimode sensor were further verified by the detection of Hg²⁺ in a series of actual water samples, including complex seawater samples, and the recoveries with different modes ranged only from 97.7% to 103.7%.