Fig. 1. Schematic diagram of the order of addition of various substances in the study of enzyme activity

Fig. 2. SEM image and EDS energy spectrum of Ag/PANI and Au/PANI nanocomposites with different magnification
(a): 25×10³; (b): 50×10³; (c): 100×10³; (d): 200×10³;(e): EDS energy spectrum of Ag/PANI

Fig. 3. Schematic diagram of TMB oxidation by nanoparticles as peroxidase reacting with H₂O₂

Fig. 4. (a) UV-Visible absorption spectra of different reaction systems; (b) A pH-dependent response curve measured at pH=2.0~8.0
I=I/I₀, and I represents TMB at 1 611 cm^-1 SERS intensity in different buffer solutions, and I₀ represents a TMB intensity at 1 611 cm^-1 in a buffer solution with pH 4.0

Fig. 5. (a) Raman spectroscopy of Ag/PANI as a nanozyme, adding different concentrations of H₂O₂ to oxidize TMB; (b) Line chart of Raman spectral intensities of oxTMB at 1 189, 1 334 and 1 650 cm^-1

Fig. 6. Schematic diagram of nanoparticles as glucose oxidase

Fig. 7. Schematic diagram of the activity principle of Ag/PANI as a tandem enzyme in TMB color reaction
(a): Glucose-like oxidase activity;(b): Peroxidaselike activity

Fig. 8. (a) A pH-dependent reaction curve measured at pH 2.0~8.0, where I=I/I₀, I represents the SERS intensity of TMB at 1 611 cm^-1 in different buffer solutions, and I₀ represents a buffer solution with pH 4.0. The SERS intensity of TMB at 1 611 cm^-1; (b) Ag/PANI as a nanozyme, providing Raman spectroscopy of H₂O₂ oxidation of TMB by adding different concentrations of glucose

Table 1. Type of chemical reagent

Table 2. The components of different reaction systems and corresponding visual photographs