A target-induced inner-filter effect-based ratiometric sensing platform by fluorescence modulation of persistent luminescent nanoparticles and 2,3-diaminophenazine

A ratiometric fluorescent sensing platform with smartphones was designed for the highly sensitive detection of glutathione (GSH), ascorbic acid (AA), and alkaline phosphatase (ALP) activity by modulating the inner filter effect (IFE) between persistent luminescent nanoparticles (PLNPs) and 2,3-diaminophenazine (DAP). As an oxidase-mimetic nanomaterial, MnO2 nanosheets (MnO2 NSs) could oxidize o-phenylenediamine (OPD) to DAP, which exhibited a yellow fluorescence emission signal at 558 nm, whereas the fluorescence of PLNPs at 475 nm was quenched through IFE. The presence of GSH and AA reduced MnO2 NSs to Mn2+, which inhibited the oxidation of OPD, and effectively preserved the blue fluorescence of PLNPs at 475 nm. Furthermore, ALP can catalytically hydrolyze l-ascorbic acid 2-phosphate trisodium salt (AAP) to yield AA. Therefore, a simple, highly sensitive and reproducible ratiometric fluorescent sensing platform with good selectivity was fabricated to detect GSH, AA and ALP activity by measuring the ratio of the fluorescence intensity of DAP and PLNPs. The linear ranges for GSH, AA and ALP activity were 1-100 mu M, and 1 to 5 mU mL(-1), and the limits of detection were 0.2 mu M, 0.33 mu M and 0.3 mU mL(-1), respectively. Finally, the proposed sensor was utilized in spiked human serum and urine sample detection with satisfactory recoveries. Moreover, the red-green-blue (RGB) intensities of a color image were acquired via scanning measurement analysis with the help of the color-scanning application on smartphones and portable UV lamps, enabling real-time and in situ detection of ALP activity, GSH, and AA.