Cu/Mn Double-Doped CeO2 Nanocomposites as Signal Tags and Signal Amplifiers for Sensitive Electrochemical Detection of Procalcitonin

Nanomaterials themselves as redox probes and nanocatalysts have many advantages for electrochemical biosensors. However, most nanomaterials with excellent catalytic activity cannot be directly used as redox probe to construct electrochemical biosensor because the redox signal of these nanomaterials can only be obtained in strong acid or alkali solution at high positive or negative potential, which greatly limits their applications in biologic assay. In this study, Cu/Mn double-doped CeO₂ nanocomposite (CuMn-CeO₂) was synthesized to use as signal tags and signal amplifiers for the construction of electrochemical immunosensor for sensitive assay of procalcitonin (PCT). Herein, CuMn-CeO₂ not only possesses excellent catalytic activity toward H₂O₂ for signal amplification, but also can be directly used as redox probe for electrochemical signal readout achieved in neutral mild buffer solution at low positive potential. Importantly, since doping Cu, Mn into CeO₂ lattice structure can generate extra oxygen vacancies, the redox and catalytic performance of obtained CuMn-CeO₂ was much better than that of pure CeO₂, which improves the performance of proposed immunosensor. Furthermore, CuMn-CeO₂ can be implemented as a matrix for immobilizing amounts of secondary antibody anti-PCT by forming ester-like bridging between carboxylic groups of Ab₂ and CeO₂ without extra chemical modifications, which greatly simplifies the preparative steps. The prepared immunosensor exhibited a wide linear range of 0.1 pg mL^-1 to 36.0 ng mL^-1 with a low detection limit of 0.03 pg mL^-1. This study implements nanomaterial themselves as redox probes and signal amplifiers and paves a new way for constructing electrochemical immunosensor.

Facile preparation of Ag/Ni(OH)2 composites with enhanced catalytic activity for reduction of 4-nitrophenol

Preparation and formation mechanism of Ag/Ni(OH)₂ composites with enhanced catalytic activity for reduction of 4-nitrophenol were systematically studied.

Decoration of Pt on Cu/Co double-doped CeO2 nanospheres and their greatly enhanced catalytic activity

In this paper, we report an efficient strategy for the synthesis of Cu/Co double-doped CeO2 nanospheres (Cu x Co1-x -CeO2-Pt, 0 ≤ x ≤ 1), which were fabricated via a simple water-glycol system. The following in situ surface decoration of Pt nanoparticles make these nanospheres highly active for the catalytic reduction of nitrophenol and CO oxidation. Detailed tests show that their catalytic performance strongly depends on the doping components and ion concentration of Cu and Co ions. The best samples of Cu0.50Co0.50-CeO2-Pt and Cu0.34Co0.66-CeO2-Pt demonstrate an excellent turnover frequency (TOF) of more than 450 h-1 after five cycles and retains about 99% conversion by using NH3BH3 as a reductant to reduce nitrophenol. Moreover, Cu0.50Co0.50-CeO2-Pt possesses a much lower light-off and T100 (the temperature for 100% CO oxidation) temperature compared with the other catalysts.

Galvanic replacement synthesis of Ag x Au1-x @CeO2 (0 ≤ x ≤ 1) core@shell nanospheres with greatly enhanced catalytic performance

A galvanic replacement strategy has been successfully adopted to design Ag x Au1-x @CeO2 core@shell nanospheres derived from Ag@CeO2 ones. After etching using HAuCl4, the Ag core was in situ replaced with Ag x Au1-x alloy nanoframes, and void spaces were left under the CeO2 shell. Among the as-prepared Ag x Au1-x @CeO2 catalysts, Ag0.64Au0.36@CeO2 shows the optimal catalytic performance, whose catalytic efficiency reaches even 2.5 times higher than our previously reported Pt@CeO2 nanospheres in the catalytic reduction of 4-nitrophenol (4-NP) by ammonia borane (AB). Besides, Ag0.64Au0.36@CeO2 also exhibits a much lower 100% conversion temperature of 120 °C for catalytic CO oxidation compared with the other samples.

Strongly Coupled PtNi0.3 Co2.7 O4 Hybrid Nanoflowers with Remarkably Enhanced Catalytic Performance

The nonstoichiometric metal oxide Ni_0.3 Co_2.7 O₄ served as a support for small-sized Pt nanoparticles. The whole synthesis of the hybrid material can be kinetically controlled and no further surface-modification treatment was required. More importantly, the as-obtained strongly coupled PtNi_0.3 Co_2.7 O₄ hybrid nanoflowers exhibit remarkably enhanced catalytic activities compared with PtNiO and PtCo₃ O₄ hybrid samples. This result indicates that it is possible to optimize the catalytic performance of noble metals by using a nonstoichiometric metal oxides as a support instead of a stoichiometric metal oxide.