Fig. 4. Dependence of initial rate on volume of GOx injected into a 4 mL solution in a UV-Vis cuvette, keeping nanosheet, glucose and MES buffer concentrations fixed (nanosheet concentration using the absorbance, [glucose] = 0.5 mM, [MES] = 100 mM, [GOx] = 7.5 mg mL⁻¹ concentrate before injection). (a) Absorbance at 384 nm vs. time for various volumes of GOx injected. GOx is injected at the 30 s mark and stirred. The label for each data set indicates volume (μL) of GOx solution injected. (b) Initial reaction rate vs. volume of GOx injected; the plot in (b) is obtained using data shown in (a), data translated to start at the same absorbance for clarity. (c) Initial reaction rate vs. MnO₂ absorbance and a linear fit.