Yolk-shell nanostructured Fe 3 O 4 @C magnetic nanoparticles with enhanced peroxidase-like activity for label-free colorimetric detection of H 2 O 2 and glucose.

Herein, we have developed a simple and facile method to synthesize yolk-shell nanostructured Fe3 O4 @C nanoparticles (NPs) as a multifunctional biosensing platform for the label-free colorimetric detection of H2 O2 and glucose. It was demonstrated that Fe3 O4 @C yolk-shell nanostructures (YSNs) retained the magnetic properties that can be used for separation and concentration. Also importantly, the Fe3 O4 @C YSNs exhibited an intrinsic peroxidase-like activity that could quickly catalyze the enzyme substrate in the presence of H2 O2 and produce a blue color. Compared to other similar ferric oxide-based NPs with different structures, Fe3 O4 @C YSNs exhibited greatly enhanced catalytic activities due to their unique structural features. Moreover, steady-state kinetics indicated the catalytic behaviors in agreement with the classic Michaelis-Menten models. Taking advantage of the high catalytic activity, Fe3 O4 @C YSNs were employed as novel peroxidase mimetics for label-free, rapid, sensitive, and specific colorimetric sensing of H2 O2 and glucose, suggesting that Fe3 O4 @C YSNs have the potential for construction of portable sensors in the application of point-of-care (POC) diagnosis and on-site tests.