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Figure 1. 

(a), (b) Images of Ag₃PO₄ NPs captured by FE-SEM at various magnifications. (c) Particle size distribution of Ag₃PO₄ NPs.

Figure 2. 

(a) Visual images and the spectra of absorption for various reaction solutions. Sample 1: 2,4-DP; Sample 2: phenol; Sample 3: 3-aminophenol; Sample 4: 2-nitroresorcinol; Sample 5: catechol. (b) Color variation of the mixture containing 4-AAP, 2,4-DP, and Ag₃PO₄ NPs in Air- or N₂-saturated buffers. (c) EPR spectra of O₂^·− generated by Ag₃PO₄ NPs.

Figure 3. 

(a) Impact of temperature on catalytic activity of Ag₃PO₄ NPs, and laccase. (b) Influence of NaCl concentration on laccase-mimicking catalytic activity of Ag₃PO₄ NPs. (c) Ethanol tolerance of Ag₃PO₄ NPs, and laccase. (d) Effect of long-term storage on catalytic activity of Ag₃PO₄ NPs and laccase.

Figure 4. 

Illustration of BPA detection using laccase-mimicking activity of Ag₃PO₄ NPs.

Figure 5. 

(a) Visual representation and absorption spectrum profiles of solutions containing varied substances. Sample 1: Ag₃PO₄ NPs + 0.2 mg·mL⁻¹ BPA + 4-AAP; Sample 2: Ag₃PO₄ NPs + 0.02 mg·mL⁻¹ BPA + 4-AAP; Sample 3: Ag₃PO₄ NPs + 0.002 mg·mL⁻¹ BPA + 4-AAP; Sample 4: Ag₃PO₄ NPs + 4-AAP. (b) Visual image and absorption spectra of the solution containing different substances. Sample 1: Ag₃PO₄ NPs; Sample 2: 0.2 mg·mL⁻¹ BPA; Sample 3: 4-AAP; Sample 4: Ag₃PO₄ NPs + 0.2 mg·mL⁻¹ BPA; Sample 5: 0.2 mg·mL⁻¹ BPA + 4-AAP.

Figure 6. 

Effect of (a) pH, (b) HEPES buffer concentration, (c) 4-AAP concentration, (d) Ag₃PO₄ NPs concentration on ΔA.

Figure 7. 

(a) BPA sensitivity absorption spectrum. (b) Visual image and ΔA at 508 nm of the laccase-mimicking catalytic system added with different quantities of BPA.

Figure 8. 

(a), (b) Visual image and ΔA at 508 nm of the laccase-mimicking catalytic system added with 0.2 mg·mL⁻¹ of BPA and different competitive substances. (c) Schematic illustration of the coordination between BPA and Ag₃PO₄ NPs.

Figure 9. 

The recyclability of Ag₃PO₄ NPs. The activity of 100% is set where absorbance is highest and the relative activities of other samples are calculated based on this standard. The Ag₃PO₄ NPs are recovered through centrifugation at 10,000 rpm for 10 min, washed with double-distilled water, and then re-disperse.