MoO 2 is a promising material for efficient and cost-effective electrocatalytic water splitting, particularly for the oxygen evolution reaction (OER) in alkaline media. Modifying the morphology, composition, or oxidation state of MoO 2 can enhance its active surface area and performance. In this study, Mo-coated carbon paper was used as a substrate to synthesize well-organized MoO 2 nanowires and nanosheets via a one-step CVD method without any catalyst. The nanosheets and nanowires grow perpendicularly to the substrate. MoO 2 nanowire arrays exhibit superior OER performance, characterized by a lower onset potential (1.54 V), a smaller Tafel slope, and enhanced durability compared to nanosheets. This improvement is likely attributed to the increased number of exposed active sites, reduced presence of oxidized Mo 4+ , and smaller crystalline size. Graphical abstract Here, well-organized MoO 2 nanowires and nanosheets have been fabricated on carbon paper using a one-step CVD method by reducing MoO 3 with Mo powder to investigate the intrinsic relationship between morphology, elemental composition and state, and their electrocatalytic properties. The obtained nanosheets presented as a flower-like structure, while nanowires formed into well-aligned arrays. MoO 2 nanowires contained higher amounts of Mo 4+ , were composed of smaller crystal grains, and possessed a lower onset potential for OER (oxygen evolution reaction) at about 1.54 V, a smaller Tafel slope at about 110 mV/dec, and better durability when compared to MoO 2 nanosheets.
In this work, a sandwich-type electrochemical immunosensor was fabricated to the effective detection of hepatitis B surface antigen (HBsAg). The designed electrochemical immunosensor was based on Au core and Pd shell nanodendrites loaded on amino functionalized molybdenum dioxide nanosheets (Au@Pd NDS/NH 2 –MoO 2 NSs) as the secondary antibody (Ab 2 ) label and silver nanoparticles were loaded by electrodeposited (D-Ag NPs) on the surface of electrode as the platform. Because of the synergistic effect and abundant catalytic activity sites provided by surface dendrite structure, Au@Pd NDs were more effective than single gold and palladium nanoparticles in catalytic reduction of hydrogen peroxide (H 2 O 2 ). MoO 2 had the good catalytic capacity for reduction of H 2 O 2 and favourable electrical conductivity . Hence, the obtained Au@Pd NDS/NH 2 –MoO 2 NSs were more effective than Au@Pd NDs and NH 2 –MoO 2 NSs in catalytic reduction of hydrogen peroxide attribute to a synergistic effect. Also, Ag NPs with admirable electrical conductivity and biocompatibility were used as sensing platforms and primary antibodies (Ab 1 ) carriers, which can accelerate the electron transfer and improve the sensitivity of the immunosensor. Here, the proposed electrochemical immunosensor offered a wide linear interval from 10 fg mL −1 to 100 ng mL −1 and the lower limit of detection of 3.3 fg mL −1 (S/N = 3) for detection of HBsAg under optimal experimental conditions. Furthermore, the accuracy of the actual serum sample analysis was satisfactory, which showed that the electrochemical immunosensor possessed a good application prospect in clinical detection.
Li Xu,Pingyue Hu,Liwen Tan,Junchun Guo,Sheng Li,Xiaoli Xiong
Dopamine (DA) is a key neurotransmitter in the central nervous system, and abnormal concentrations are associated with a variety of diseases. In this study, a novel electrochemical sensor is constructed based on ultrathin P-doped MoS2/MoO2 nanosheets supported on bowl-shaped N-doped carbon hemispheres (N-BCH@P-MoS2/MoO2). The unique hierarchical structure combines the high specific surface area of N-BCH with the enhanced electrocatalytic activity of P-doped MoS2/MoO2, resulting in significant improvements in the performance for DA detection. The electronic structure of the catalyst is further modulated by the codoping of N and P, which increases the electrical conductivity and the number of active centers. The results show that the N-BCH@P-MoS2/MoO2 exhibits excellent sensitivity and selectivity for DA detection, capable of achieving a detection limit as low as 0.12 μM within a broad concentration range (3–100 μM) (S/N = 3). Furthermore, electrocatalysts have been employed in the detection of DA in human serum, indicating significant promise for clinical diagnosis.
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