Lavandula multifida as a novel eco-friendly fluorescent-blue material for mercury ions sensing in seawater at femto-molar concentration.

In this paper, we present a novel fluorescent material based on the herbal tea of Lavandula multifida (Lm). The fluorescence properties of Lm aqueous extract were analyzed under various excitation wavelengths in the range of 290-450 nm. The Lm herbal infusion was found to be highly fluorescent, with an emission maximum at 450 nm under excitation at 390 nm. Consequently, it was exploited to develop a fluorescence method for detecting metal ions. Results obtained upon the addition of Hg2+, Na+, K+, Ca2+, Mg2+, Pb2+, Cd2+, Cu2+, Ni2+, Bi3+, Mn2+, Fe3+ and Co2+ ions showed that the fluorescence intensity of the Lm aqueous extract decreased strongly with the presence of mercury ions. A solid-state fluorescent sensor, based on Lm embedded into a Nafion membrane and deposited on a transparent polyethylene terephthalate (PET) sheet, has also been developed for the effective detection of Hg2+ ions. The Lm-Nafion-PET sensor exhibited good stability, high repeatability, and reproducibility. Furthermore, the Lm-Nafion/PET sensor demonstrated remarkable sensitivity to Hg2+ in sea water, with a limit of detection of 0.25 fM. To our knowledge, this is the first study which reports Lavandula multifida plant for making a novel eco-friendly fluorescent solid-state sensor for the detection of mercury ions at femto-molar concentrations in seawater.