Fig. 2.

Enzyme-like properties of the Pd nanocrystals. Oxidase-like properties of the Pd nanocrystals. Time-dependent absorbance spectra of the AA species catalyzed by a the Pd cubes and b the Pd octahedrons with the characteristic absorption maximum of AA at 250 nm. c The concentration of H₂O₂ generated in the catalytic system: AA alone and AA with the different Pd nanocrystals. The data indicate the means and SD from three parallel experiments. P-values were calculated by the Student’s test: **p < 0.01. Peroxidase-like properties of the Pd nanocrystals. Time-dependent absorbance spectra of TMB in different reaction systems: d Pd cubes + H₂O₂ + TMB and e Pd octahedrons + H₂O₂ + TMB, where the maximum absorbance values for the TMB⁺ intermediate (responsible for the characteristic blue color) are at 370 nm and 652 nm, respectively. The inserted images (tubes) represent the visual color changes of TMB in different reaction systems: 1, H₂O₂ + TMB; 2, Pd nanocrystals + TMB; 3, Pd nanocrystals + H₂O₂ + TMB. f The fluorescence spectra for detection of hydroxyl radicals from the different reaction systems. Here, the intermediate fluorescence product, 2-hydroxy terephthalic acid (TAOH), presents a maximum emission wavelength at 435 nm