SERS and fluorescence-based ultrasensitive detection of mercury in water

The development of reliable and ultrasensitive detection marker for mercury ions (Hg²⁺) in drinking water is of great interest for toxicology assessment, environmental protection and human health. Although many Hg²⁺ detection methods have been developed, only few offer sensitivities below 1pM. Herein, we describe a simple histidine (H) conjugated perylene diimide (PDI) bolaamphiphile (HPH) as a dual-responsive optical marker to develop highly selective and sensitive probe as visible (sol-to-gel transformation), fluorescence and SERS-based Hg²⁺sensor platform in the water. Remarkably, HPH as a SERS marker supported on Au deposited monodispersed nanospheres monolayers (Au-MNM) of polystyrene offers an unprecedented selectivity and the best ever reported detection limit (LOD) of 60 attomolar (aM, 0.01 parts-per-quadrillion (ppq)) for Hg²⁺ in water. This is ten orders of magnitude lower than the United States Environmental Protection Agency (USEPA) tolerance limit of Hg²⁺ in drinking water (10nM, 2 ppb). This simple and effective design principle of host-guest interactions driven fluorescence and SERS-based detection may inspire the future molecular engineering strategies for the development of ultrasensitive toxic analyte sensor platforms.