Highly selective and sensitive twin-cyano-stilbene-based two-photon fluorescent probe for mercury (ii) in aqueous solution with large two-photon absorption cross-section

The fluorophore derived from stilbene with two cyano groups in a single aromatic ring shows reasonably large two-photon absorption cross-section and emits strong two-photon fluorescence. A water-soluble two-photon sensor composed of the fluorophore containing bis[2-(2-hydroxyethylsulfanyl)ethyl]amino group (ionophore) has a very high sensitivity and selectivity for Hg2+ in water. It can be used to detect trace Hg2+ in near neutral aqueous solution (pH > 6.5), and its binding constant (log K) for Hg2+ is as high as 5.72 ± 0.03. Nitrogen atom property and the sulfur atom number on the ionophore are believed to be responsible for the unique selectivity of probe 1 for Hg2+.