Real-time detection of mercury ions based on vertically grown ReS2 film

Mercury (Hg2+), one of the most dangerous toxins in water, is a heavy metal that causes organ damage from both short-term and chronic exposure. Conventional methods for detecting mercury such as atomic absorption spectrometry or Raman spectroscopy require bulky equipment with complicated procedures. In this work, we fabricated a highly sensitive, real-time thin-film sensor based on vertically aligned rhenium disulfide (ReS2). Its outstanding large surface area and the unique electronic appearance of its layered architecture make a ReS2 nanosheet a strong contender for such an application. The sensor exhibited a fast response speed (< 2 s) to Hg2+ and an ultralow detection limit of 4 nM, which is significantly less than that of the U.S. Environmental Protection Agency's (U.S. EPA) allowed utmost contamination limit for Hg2+ in drinking water (10 nM). It also exhibited strong selectivity for Hg2+ against other metal ions such as Na+, Zn2+, Fe3+, Cu2+, Ca2+, Ni2+, Ag+, Cd2+, Fe2+, and Pb2+. Because this nanosheet can be replaced with any secondary substrate and possibly patterned into a microscale size, the sensor can be integrated into multiple platforms such as portable devices or sensor nodes in a grid network.