Determination of Fe3+ upon Special “Upconversion Luminescence” of Dopamine

A promising technique based on the luminescence with long wavelength excitation and short wavelength emission (LExL, λ ex-L > λ em ) is developed. This LExL is different from traditional upconversion luminescence (UCL). The LExL, namely, special "UCL", is realized by a xenon light source of a common spectrofluorometer. In this work, we found that dopamine (DA) has this LExL phenomenon. The LExL of DA is mainly caused by the excitations of second-order diffraction light (λ ex-L /2). The two-photon absorption properties of DA have been calculated employing the density functional response theory. The LExL and Stokes luminescence (SL, λ ex-S < λ em ) of DA both showed static quenching upon the addition of Fe 3+ . Dual-mode luminescence methods upon LExL (λ ex-L /λ em at 565/317 nm) and SL (λ ex-S /λ em at 282/317 nm) of DA were applied for the selective determination of Fe 3+ . The detection limits are 0.30 and 0.52 μmol L -1 for LExL and SL, respectively. In addition, their linear ranges for Fe 3+ determination are both from 0.70 to 30 μmol L -1 . The LExL method of DA not only meets the basic determination criteria for Fe 3+ but also offers additional advantages in resisting more interferences and shows satisfactory feasibility performances.