Fig. S4 A displays the amperometric responses of MnO2/PTH/rGO towards sequential addition of MP into 0.1 M PBS at pH 7 by applying the constant potential of +0.50 V. For each addition (10 nM to 1 µM), a sharp rise in the response current was observed and 95% of steady state current was reached within 3s. The linear increase of MP and its responses of increasing peak current, indicates the great electrocatalytic response of the reduction of MP using MnO2/PTH/rGO nanocomposite modified electrode. The concentration dependent linear plot displayed good linearity with the correlation coefficient of R2 = 0.9917 (inset, Fig. S4 B).The limit of detection (LOD) was found to be 5.72 nM and the sensitivity was 0.0498 µA µM-1 cm-2. The important parameters of the sensor, such as LOD and linear range were compared to previously reported different modified electrode using pesticide sensors (Table 2).