Oxygen vacancies modulation Mn3O4 nanozyme with enhanced oxidase-mimicking performance for l-cysteine detection

Mn3O4 nanomaterials exhibit intrinsic molecular oxygen activation properties in biomimetic and environmental catalysis. Modulating the oxygen vacancies (OVs) and identifying the oxygen activation mechanism of Mn3O4 nanomaterials are vital for designing high-performance nanozymes. Herein, the synthesized OV-Mn3O4 Nanoflowers (NFs) possesses different OVs concentrations by regulating oxygen partial pressure. The oxidase-mimicking OV-Mn3O4 NFs showed high catalytic reaction efficiency (kcat/Km) of 1.88 × 10−8 s−1 μM−1, 26.86-fold higher than Mn3O4 with poor-OVs (7.00 × 10-10 s-1 μM-1). The changes of substrates absorption, reactive oxygen species (ROS), and Mn2+/Mn3+/Mn4+ contents are attempted to illustrate clearly with the participation of OVs. Modulation OVs of Mn3O4 nanozymes can enhance the oxygen storage capacity and increase Mn species with lower valence states, which can generate abundant and multifarious ROS for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) substrates. Besides, l-cysteine (l-Cys) is a pivotal amino acid for antiaging and reducing melanin. Colorimetric detection for l-Cys was established based on the enhanced oxidase-like properties of OV-Mn3O4. Compared with Mn3O4 NFs, OV-Mn3O4 NFs are exhibited more sensitive limit of detection (1.31 μM versus 5.69 μM, S/N = 3). Overall, the in-depth mechanism understanding of OVs can provide new perspective to rational design nanozymes and detection sensor with satisfactory property.