Herein, we prepared dopamine assistant-synthesized nanoflowers (dNFs) and norepinephrine assistant-synthesized nanoflowers (neNFs) as novel nano-biocatalysts with intrinsic and effective peroxidase mimic activities. The NFs dispersed in solution or immobilized on the filter membrane served as the Fenton reagent in the presence of hydrogen peroxide (H2O2) allowing spectrophotometric and colorimetric detection ofm-cresol and dopamine. Due to its high polar surface property and porosity, the neNFs exhibited remarkably high catalytic activity than dNFs in both solution or in immobilized states. The activity performance of neNFs as a function of varied concentrations of neNFs orm-cresol or dopamine or H2O2; and reaction time was also studied. The oxidative reaction of 0.5 mMm-cresol (in the presence of 4-AAP and H2O2) or 0.25 mM dopamine (in the presence of H2O2) catalyzed by the neNFs (1 mg/mL) were visually detected within 10 min in solution. Whereas, after immobilization on filter membrane, the colorimetric detection of the same concentrations ofm-cresol or dopamine was achieved in 30 min using neNFs (2 mg/mL). Furthermore, the effect of repeated use of the neNFs in solution or immobilized states on the catalytic activity was also investigated. We expect that, the NFs formed from non-enzyme molecules possess peroxidase mimic activities that could imply to a study for bioanalytical and biomedical application in the near future.