A new oligo(N,O-donor)-like ratiometric fluorescent probe with FRET effect for dual-channel recognition of B4O72- ions in practical water samples

B4O72- ions are widely found in various production and living environments, and can cause serious effects on human health. For this reason, it is necessary to develop a high-efficiency method for the detection of B4O72- ions. Here a oligo(N,O-donor)-like dual-channel ratiometric fluorescence probe H3L was designed and synthesized for the detection of B4O72- ions in environmental samples. The recognition of B4O72- is based on the FRET effect by the probe H3L, the naphthalene ring partially serves as an energy donor, benzene ring partially serves as an energy acceptor, and phenolic oxygen acts as a reaction site for B4O72-. The probe H3L mainly displays the blue fluorescence of the donor; the presence of the B4O72- ions turns on the FRET effect, which will lead to yellow fluorescence of the benzene ring acceptor, enabling a ratiometric fluorescence recognition process. The probe has a large Stokes red shift (Δλ = 123 nm), which makes the emission wavelength after red shift more than 500 nm, and the obvious colourless to yellow color change can be observed by naked eyes, which solves the background fluorescence interference problem of short-wavelength fluorescence probe. At the same time, the probe has high selectivity and high sensitivity (low detection limit of 17.3 nM). In addition, we have successfully used this probe to detect B4O72- ions in actual samples. These results showed that the probe has a broad application prospect.