In this work hollow Pd nanospheres were successfully synthesized by using galvanic replacement of facile synthesized Cu2O nanospheres with palladium for the first time. The SEM showed the hollow structure of Pd nanospheres and the XRD analysis proved the successful preparation of Pd. This method is surfactant-free, and well-dispersed hollow Pd nanospheres can be obtained through this route. It was found that the hollow Pd nanospheres showed good electrochemical properties and could be used as catalysts in DEFCs. From cyclic voltammograms, the onset potential of hollow Pd nanospheres shifted negatively by 100mV and the peak current of hollow Pd nanospheres was about two times higher than that of solid Pd nanospheres.

An enzymeless glucose biosensor based on polypyrrole nanofibers-supporting Au nanoparticles (Au/PPyNFs) was investigated in this study. The Au/PPyNFs heterogeneous composite materials were synthesized in-situ via hydrogen bonding interactions for the assembly of polyethyleneimine (PEI) on the surface of polypyrrole nanofibers (PPyNFs). By changing the molar ratio of PPy to HAuCl4, Au/PPyNFs with different Au loadings were obtained. The morphology and composition of Au/PPyNFs were characterized using SEM, TEM, FTIR, XRD and XPS, respectively. The hybrids exhibited a high electrocatalytic activity toward glucose oxidation, which is prerequisite for the catalysts to be applied in amperometric glucose sensors. By using the nonenzymatic glucose sensor based on Au/PPyNFs, 0.2–13 mM glucose can be detected with a sensitivity of 1.003 μA cm−2 mM−1 and a good linearity (R2=0.9993) between current density and glucose concentration. The proposed glucose sensor provides a promising strategy to construct fast, sensitive, and anti-interfering amperometric sensors for early diagnosis and prevention of diabetes.

Au@Pd core–shell nanoparticles (NPs) were synthesized using seed-mediated method, and three samples with different shell structures were obtained by tuning the Au core size. The shape-dependent catalytic activities of Au@Pd core–shell NPs toward ethanol oxidation in alkaline electrolytes were systematically explored. The electrochemical experiments showed that the Au@Pd-2 core–shell NPs (with Au core size of 9.8nm and loose Pd shell) exhibited a distinctly higher activity and poison-resistance for the ethanol oxidation than other core–shell structures. Based on the Au@Pd-2 core–shell NPs and Pd NPs, two amperometric ethanol gas sensors were fabricated. During the sensor tests, the ethanol sensor based on Au@Pd-2 NPs showed good performance for ethanol in the range of 50–600ppm with sensitivity of 178.5nAppm−1 and less than 5% signal loss in 60 days.

Gold nanoparticles supported on multi-walled carbon nanotubes (Au/MWCNTs) were prepared as electrocatalysts for an electrochemical sensor of acetylene. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical experiments showed that the catalysts exhibited a distinctly higher activity for the acetylene electro-oxidation than Au-NPs and Au/C catalysts. In typical cyclic voltammograms, the onset potential of Au/MWCNTs for the acetylene oxidation is 0.73V, which is 0.19V more negative than that of Au-NPs. The acetylene sensor test showed good linear response towards acetylene concentration in a wide range from 10ppm to 50ppm with a steady response current for 300s, good sensitivity of 80nA/ppm and fast 90% response time (t90) of 25s to 50ppm acetylene. All the results indicate a good potential application of this sensor in the detection of acetylene.

An enzymeless biosensor based on CuxO/Cu electrode was investigated in this study. The XRD analysis confirmed that CuxO nanostructured material was composed of Cu2O and CuO. The FESEM images showed that the catalysts were flower-like with large surface area. From cyclic voltammograms, the peak current of CuxO/Cu electrode was 6, 6.3 and 1.7 times higher than that of the Cu foil, Cu2O/GCE and CuO/GCE electrodes, respectively. The biosensor based on CuxO/Cu exhibited excellent performance for glucose detection, giving a linear dependence between current and glucose concentration (R=0.996), with a low detection limit (0.049 mM) and high sensitivity (1.62 mA cm(-2) mM(-1)). Finally, the CuxO/Cu sensor was applied and checked in the glucose determination in blood serum samples.