Fig. 2 UV-vis spectra of different combinations after 10 min of reaction
at room temperature.
The impact of various factors, including pH, temperature, catalyst
concentration and reaction time. On the catalytic abilities of R12-AgNPs
was further explored using UV-Vis absorption spectra. To determine the
optimal pH value, absorption spectra were recorded across a pH range
from 3 to 8 (Fig. 3A). It was observed that the absorption peak at 652
nm was absent at pH 8, whereas the highest absorbance at this peak was
attained at pH 4. Therefore, the optimum reaction pH of R12-AgNPs was
determined to be pH=4, consistent with the previous report [43]. In
addition, the absorbance values increased with rising temperature and
reached peaked at 50 ℃ (Fig. 3B). However, a decline in the
concentration of ox-TMB was noticed at higher temperature (60 ℃), which
may be attributed to the reduced thermal stability of
H2O2 in an acidic environment [20].
The effect of catalyst concentration was analyzed by adding AgNPs in the
range of 0-100 μL to the solution. The results in Fig. 3C indicated that
the catalytic activity of TMB oxidation increased with a higher catalyst
concentration, with the highest absorbance at the 652 nm peak occurred
at 100 μL of R12-AgNPs solution was used. Finally, the changes in
catalytic activity over to the course of the reaction time were
demonstrated in Fig. 3D, revealing the maximum catalytic activity was
achieved within 10 min. Consequently, the optimal conditions for maximum
catalytic activity in the oxidation of TMB were discovered to be at a pH
of 4, a temperature of 50 ℃, 100 μL of AgNPs, and a reaction time of 10
min.