Ratiometric Sensing for Alkaline Phosphatase Based on Two Independent Signals from in Situ Formed Nanohybrids of Semiconducting Polymer Nanoparticles and MnO Nanosheets.

Ratiometric sensing systems transduced through independent analyte-sensitive response signals, which are simultaneously obtained from a single material, are highly desired to improve sensing reliability and sensitivity. In this study, a dual-model ratiometric sensing system with fluorescence and second-order light scattering (SOS) as transducing signals has been designed for the ratiometric detection of alkaline phosphatase (ALP). Semiconducting polymer nanoparticles (SPNs) made of poly[(9,9-dioctylfluorenyl-2,7-diyl)--(1,4-benzo-{2,1',3}-thiadiazole)] are prepared and used as reducing and stabilizing agents to prepare MnO nanosheets in situ through the reduction of KMnO. The formed SPNs@MnO nanohybrids exhibit independent fluorescence and SOS response to ALP by using l-ascorbic acid 2-phosphate trisodium salt as the enzyme substrate. Benefiting from the simultaneous availability of fluorescence and SOS signals under the same excitation, a ratiometric probe has been constructed successfully for ALP sensing. Under optimal conditions, the SPNs@MnO nanohybrids for ALP detection show a good linear detection range from 0.1 to 9.0 U L with a detection limit of 0.034 U L. Additionally, a visual and portable sensing device for ALP detection is also constructed based on the fluorescent performances of the SPNs@MnO nanohybrids. We believe the proposed method with the in situ preparation of SPN-based hybrid probes via the reducing ability of SPNs will pave a new way for the construction of multifunctional sensing materials in chemo-/biosensing applications.