The enzyme activity of PE-GA/Pt was determined by analyzing the remaining starch by the Na2S2O3/I2 titration method. GA activity is defined as the amount of glucose generated by 1 mg of GA per hour in the presence of excess starch. In a typical assay, 10 mg of PE-GA/Pt or 0.033 mg of GA in 0.3 ml of DI water was added into 0.2 ml of sodium acetate buffer [0.05 M (pH 4.6)], and then, the reaction solution was incubated in a water bath at 25 or 45°C. Starch (2 wt %; 0.5 ml) in DI water, which was preheated in the water bath at the same temperature, was added into the reaction solution. After 30 min, 80 μl of sodium hydroxide (0.5 M) was added to terminate the reaction, and then, 0.4 ml of triiodide anion [I3, 0.1 M, a mix of I2 (13 mg/ml) and KI (35 mg/ml)] and 0.6 ml of sodium hydroxide (0.1 M) were added into the reaction solution to oxidize the generated glucose. After 15 min, 0.08 ml of sulfuric acid (2 M) was added to stop the reaction, and the remaining I3 in the reaction solution was measured by Na2S2O3 titration. The amount of generated glucose by the enzymes was calculated according to titrated Na2S2O3.

In the assay under NIR irradiation, the reaction was performed at room temperature. The mix of PE-GA/Pt and starch was irradiated by an NIR laser at 3.8 W cm−2 for 30 min, and then, the same procedure was conducted as described above.

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