Four-in-One Biomimetic Cascade Nanoreactor Based on Pd@CeO₂ Functionalized Nitrogen-Doped Porous Carbon/Reduced Graphene Oxide for Colorimetric Sensing

Biomimetic cascade nanoreactors propelled by progressive nanozymes have attracted much attention recently in biological detection on account of their great cascade catalytic efficiency and exceptional stability. Here, a novel biomimetic cascade nanoreactor-Pd@CeO2 self-assembled nanospheres functionalized nitrogen-doped porous carbon-reduced graphene oxide (Pd@CeO2/N-PC-rGO) was designed and prepared. Due to the stabilization of small-sized PdNPs by highly stable porous CeO2 nanostructures, the restriction and stabilization of Pd@CeO2 nanospheres by nitrogen-doped porous carbon-reduced graphene oxide (N-PC-rGO) with N-containing functional groups and large surface areas, the sandwich-like structured Pd@CeO2/N-PC-rGO possessed four enzyme-like activities with similar catalytic efficiency and good stability, including oxidase (OXD), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) mimicking properties. Based on the OXD- and POD-mimetic mechanisms of Pd@CeO2/N-PC-rGO, a workable colorimetric platform utilizing the synergistic catalysis and cascade catalytic amplification strategy was put forward for reduced glutathione (GSH) sensing. The established GSH sensor has a broad linear range (0.02-3 mu M and 3-50 mu M) and a high detection sensitivity (20 nM). Hence, the nanoreactor Pd@CeO2/N-PC-rGO with tetraenzyme-mimicking activities revealed huge potential and broad prospects in biosensing and biomedical applications.