▎ 摘　　要

Environmental pollution involves contaminants, pollutants and toxic chemicals that create disturbance in natural environment and is one of the most serious threats for human health. This issue may be resolved by designing an efficient catalyst however it is challenging to design nontoxic catalyst to solve the environmental related issues. In this report we have developed a novel catalyst cerium molybdate (CeM) as a peroxidase mimic with cotyledons type morphology which is not reported yet. GO-cerium molybdate (GO-CeM) nanostructures are also designed first time with enhanced performance as compare to bare CeM for colorimetric detection of dual ions (S2- and Sn2+). GO-CeM nanostructures synthesized with ex-situ approach show high catalytic activity in comparison to pure CeM and GO-CeM (in-situ) catalysts. The value of Michaelis-Menten constant (Km) and maximum initial velocity (Vmax) of pure CeM catalyst for TMB is found to be similar to 0.66 mM and 1.71 x 10(-8) Ms-1 respectively. Km and Vmax value of GO-CeM (in-situ and ex-situ) catalyst was found to be 0.39 mM, 1.78 x 10(-8) Ms-1 and 0.30 mM, 2.5 x 10(-8) Ms-1 respectively that is quite lesser than pure CeM catalyst. Km and Vmax value of GO-CeM (ex-situ) catalyst for H2O2 was also calculated and found to be 0.44 mM and 3.3 x 10(-8) Ms-1 respectively. The catalyst shows high sensitivity and selectivity of S2- and Sn2+ ions among the series of cations and anions. The limit of detection (LOD) of S2- ions has been observed as 11.70 mu M with the linearity range 20-100 mu M, while the limit of detection of Sn2+ ions was observed as 5.58 mu M with linearity range about 10 80 mu M. The present work exhibits the high catalytic activity of GO-CeM (ex-situ) catalyst in terms of good sensitivity and selectivity.