▎ 摘　　要

Procalcitonin (PCT) is an inflammatory marker with significance in the early diagnosis of sepsis. The label-free electrochemical impedance immunosensor has good prospects for the determination of this disease marker due to its cost-effectiveness, high specificity and simple operation. However, developing an immunosensor for procalcitonin faces challenges due to the absence of satisfactory electrodes. Herein, a novel label-free electrochemical impedance immunosensor using the three-dimensional (3D) flower-shaped gold nanoparticle@molybdenum(IV) sulfide/graphene (Au NPs@MoS2/graphene) composite is reported for procalcitonin. Under the optimal conditions, the immunosensor presents a linear response from 10 fg mL(-1) to 50 ng mL(-1) and an ultra-low detection limit of 2.3 fg mL(-1) for for procalcitonin. The excellent performance is due to the unique 3D flower-shape and the synergistic effect of Au NPs@MoS2/graphene, generating a large surface area, high electrical conductivity, and increased immobilization of anti-PCT. Additionally, the immunosensor exhibits suitable specificity, stability, and reproducibility, and was used to determine procalcitonin in serum which may allow clinical screening and diagnosis of sepsis.