A signal amplifying MOF-based probe:on-site and ultrasensitive dual-channel portable detection of Hg2+ in groundwater through a fluorimetrically and RGB-based sensing assay.

Mercury (II) ions (Hg²⁺) are a significant source of heavy metal contamination in groundwater, posing a serious threat to human health and the environment. Therefore, there is an urgent need for the development of a new detection technique with high sensitivity for monitoring Hg²⁺ in contaminated groundwater. Here, we developed a signal amplifying MOF-based probe (NXS@ZIF-8) for on-site and ultrasensitive dual-channel portable detection of Hg²⁺ in groundwater. The successful grafting of the fluorescent probe (NXS) onto ZIF-8 effectively enhanced the enrichment of the NXS probe, thereby amplifying the detection signal for Hg²⁺. Upon exposure to Hg²⁺, NXS@ZIF-8 quickly emits fluorescent signals, which can be easily detected using portable laser-induced fluorescence spectrometers (LIFs) with a low detection limit of 0.30 ppb. Importantly, the platform enables on-site detection of Hg²⁺ in groundwater samples and direct on-site and in-situ detection of Hg²⁺ in contaminated groundwater, achieving acceptable results. Furthermore, NXS@ZIF-8 was fabricated as a paper-based sensor and integrated into a portable smartphone device for visual detection of Hg²⁺ in contaminated groundwater. This work presents an approach for on-site, in-situ and highly sensitive portable detection of heavy metals in contaminated groundwater, eliminating the need for access to specialized laboratory equipment.