▎ 摘　　要

DA and UA, both have definite physiological activity, and several severe diseases of human beings are related to these biomolecules. Through a facile hydrothermal process, nickel-cobalt double hydroxide decorated graphene (CoxNi1_x(OH)2/G) was synthesized for the simultaneous determination of DA and UA. In CoxNi1_x(OH)2, Co (OH)2 creates defect and reduces the charge transfer resistance of Ni(OH)2 electrode, as well as actively par-ticipates in the redox reaction. These defects act as superior active sites and significantly improved the electronic and crystalline structure of CoxNi1_x(OH)2. In CoxNi1_x(OH)2/G, graphene reduces the aggregation of Cox-Ni1_x(OH)2 and increased the electroactive surface area and electrical conductivity of the nanocomposites. As a result, the enzyme-free biosensor showed well defined peak-to-peak separation for the simultaneous determi-nation of DA and UA without interfering with each other. At the optimum conditions, the as-prepared sensor provided wide linear ranges from 0.1 to 750 mu M and from 0.25 to 925 mu M for DA and UA, respectively. The limit of detections was calculated as 43 and 97 nM, with better sensitivities of 343.71 and 132.96 mu A mM_1 cm-2 for DA and UA, respectively. Furthermore, desirable results in urine sample analysis and no significant effect of interfering substances proved CoxNi1_x(OH)2/G as an effective electrochemical sensor.