Hierarchical micro-nanostructures from polyoxometalates and polydopamine: Characterization, electrochemical and intrinsic peroxidase-like properties

Hybrid composite materials with hierarchical structures have attracted continuing attention for their enhanced features and various applications. The new hybrid composites XW9@PDA (XW9 means Na8H[α-PW9O34], Na10[α-SiW9O34] and Na10[α-GeW9O34]; PDA means polydopamine) have been synthesized for potential sensing applications. The effect of polyoxometalates on the formation of the hybrid composites was investigated. Scanning electron microscopy (SEM) supported the obtained XW9@PDA were hierarchical microsphere. By monitoring the reaction of classical peroxidase substrate o-phenylenediamine (OPD) to form yellow 2, 3-diaminophenazine (DAB) in the presence of H2O2, the peroxidase-like activity of XW9@PDA was calculated. The results showed that XW9@PDA still keep the peroxidase-like activity and have 505.98%, 208.58% and 582.78% enhancement in intrinsic catalytic activity for PW9@PDA, SiW9@PDA and GeW9@PDA. Among the three composites, PW9@PDA showed the highest peroxidase-like activity. Therefore, PW9@PDA was applicable to the colorimetric and electrochemical sensing for H2O2.