2D MoS2 nanosheets and hematein complexes deposited on screen-printed graphene electrodes as an efficient electrocatalytic sensor for detecting hydrazine

A new strategy to modify screen-printed graphene electrodes (SPGrEs) with two-dimensional molybdenum disulfide (2D-MoS2) nanosheets is described. The nanomaterial confined on the electrode surface is further modified forming a ternary complex with the redox mediator hematein (HM), using Al3+ salts as mordant. The formation of this ternary complex, HM-Al3+-(2D-MoS2), gives rise to new nanostructures that can be visualized by scanning electron microscopy (SEM). The resulting nanostructured platform has been characterized by electrochemical techniques. It exhibits a strong electrocatalytic activity towards hydrazine oxidation mainly due to the presence of quinone/hydroquinone moieties from the hematein and a good stability. The large value calculated for the electrocatalytic kinetic constant, (8.1 +/- 0.1) x10(4) M-1 s(-1), suggests that the presence of 2D-MoS2 nanosheets significantly improves the properties of hematein as an electron donor/acceptor. The catalytic current showed a linear dependence with the hydrazine concentration, which has allowed the development of a hydrazine sensor based on HM-Al3+-(2D-MoS2)/SPGrEs with detection and quantification limits of 1.05 mu M and 3.48 mu M, respectively. The presence of different interfering compounds such as glucose, urea and others did not significantly affect the response of the proposed hydrazine sensor. This sensor has been used for the determination of hydrazine in tap and river waters.