In this study, a novel type of multi-armed polymer (poyltehylene glycol, PEG) magnetic graphene oxide (GO) composite (GO@Fe3O4@6arm-PEG-NH2) has been synthesized as a support for immobilization of horseradish peroxidase (HRP) for the first time. The loading amount of HRP was relatively high (186.34 mg/g) due to the surface of carrier material containing a large amount of amino groups from 6arm-PEG-NH2, but degradation rate of phenols was also much higher (95.4 %), which is attributed to the synergistic effect between the free HRP (45.4 %) and the support material of GO@Fe3O4@6arm-PEG-NH2 (13.6 %). Compared with the free enzyme, thermal, storage and operational stability of the immobilized HRP improved. The immobilized HRP still retained over 68.1 % activity after being reused 8 times. These results suggest that the multi-armed magnetic composite has good application prospect for enzyme immobilization.

In this work, a wide range of pH-sensitive fluorescent probe has been designed by the responsive double hydrophilic block copolymer (DHBCs), which containing the fluorescein (Methacrylic salicylaldoxime, SHMa) and rhodamine (Rhodamine B methacryl hydrazide, RhSAMa) derivatives in the DHBCs. The pH-sensitive fluorescent probe gave blue and red fluorescence emissions at basic pH and acidic pH, respectively. Moreover, the fluorescent probe exhibited changes in fluorescence intensity with an alteration of turbidity of the block copolymer induced by temperature. Furthermore, we have developed a model that combines with the mobile phone for quantitative and qualitative measurement of pH value. The color extract APP for real-time pH measurement in mobile phone was constructed and used to detect the pH of the water samples.