Cascade enzyme-mimicking with spatially separated gold-ceria for dual-mode detection of superoxide anions

Abstract

Metal-semiconductor nanozyme of dumbbell Au-CeO₂ with spatially separated heterostructure has cascade superoxide dismutase (SOD)-like and peroxidase (POD)-like activities for superoxide anions detection. It was synthesized by selective growth of CeO₂ at the ends of Au nanorod (Au NR). Taking advantage of the excellent local surface plasmon resonance (LSPR) effect of Au NR, the spatially separated Au-CeO₂ has a higher photothermal effect than the continuously growing core-shell structure of Au@CeO₂. Meanwhile, the hot electrons of Au NR could transfer to CeO₂ under 808 nm laser irradiation, changing the ratio of Ce³⁺/Ce⁴⁺ redox couples over CeO₂ and facilitating H₂O₂ decomposition thus enhancing POD-like activity. Based on the SOD-like activity of Au-CeO₂, superoxide anion (O₂^·−) can be transformed into hydrogen peroxide (H₂O₂). Dual-mode including absorbance and temperature sensing detection of O₂^·−, with the detection range from nM to μM i.e., 0.1–150 μM and LOD of 0.033 μM (S/N = 3) was achieved through the cascade catalysis and photothermal effect. The as-proposed method was applicable to both cancer and normal cell samples with satisfactory accuracy and recovery.