Electrochemical sensor based on polyoxometalate immobilized using a layer-by-layer assembly process to detect 2,4-dinitrophenylhydrazine

Abstract

To develop an excellent electrochemical sensor for the detection of 2,4-dinitrophenylhydrazine (2,4-DNPH), which has become a primary organic pollutant in the environment and is greatly poisonous, four polyoxometalates (POMs) with different structures (H₃PW₁₂O₄₀: PW₁₂, K₆P₂W₁₈O₆₂: P₂W₁₈, K_12.5Na_l.5[NaP₅W₃₀O₁₁₀]·15H₂O: P₅W₃₀, K₂₈Li₅H₇P₈W₄₈·92H₂O: P₈W₄₈) were chosen to investigate their sensing performance in solution and composite films towards the detection of 2,4-DNPH. The results indicated that the composite film containing P₈W₄₈ exhibited the best performance among the four POMs. The study focused on the effect of the layer number and solution pH on the sensing performance of the composite film containing P₈W₄₈, proving that the composite film with seven layers of P₈W₄₈ in pH 7 solution showed the optimal electrocatalytic activity for the reduction of 2,4-DNPH. Further, under the optimized conditions, the sensing performance of the P₈W₄₈-based composite film was evaluated by CV and i–t curves, giving a linear concentration range of 1 to 700 μM with a low detection limit of 0.012 μM. Moreover, the selectivity, stability, reproducibility and repeatability were examined, confirming that the developed sensor has good potential for determining 2,4-DNPH in the environment.