Photoinduced electron transfer of poly(o-phenylenediamine)–Rhodamine B copolymer dots: application in ultrasensitive detection of nitrite in vivo

We demonstrate a new semiconducting polymer dot: the poly(o-phenylenediamine)–Rhodamine B copolymer dot (Pp–RhB dot), which emits in the red wavelength range. The Pp–RhB dots can be used as an ultrasensitive fluorescence probe for NO2−in vivo and show high selectivity and ultrasensitivity (detection limit: 2.0 × 10−11 M) for NO2−. The fluorescence of Pp–RhB dots is decreased (φ = 0.014) as a result of fast photoinduced electron transfer (PET) between the modulator (poly(o-phenylenediamine)) and the transducer (RhB), but the N–NO2 bonding mode prevents PET, causing the fluorescence emission to be enhanced (φ = 0.92). This probe effectively avoids the influence of auto-fluorescence in biological systems and gave positive results when tested in both aqueous solution and living cells.