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• A sandwich-type signal off PEC sensor was constructed for PCT detection. • The photoactive matrix was Au NPs/BiOI NSs/B-TiO 2 NPs. • PbS/Co 3 O 4 was as a quenching signal label for signal amplification. • The PEC sensor exhibited a low detection limit of 0.02 pg/mL. A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO 2 nanoparticles (Au NPs/BiOI NSs/B-TiO 2 NPs) as photoactive matrix and PbS quantum dots/Co 3 O 4 polyhedron (PbS/Co 3 O 4) as a quenching signal label for signal amplification. Concretely, BiOI NSs was fabricated by successive ionic layer absorption and reaction (SILAR) and formed the interlaced flake-like structure. Then Au NPs dropped on the BiOI NSs/B-TiO 2 NPs electrode forming Au NPs/BiOI NSs/B-TiO 2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co 3 O 4 , an effective dual suppression signal quencher, was proposed for signal-off PEC immunosensor to weaken the photocurrent response because of the steric impedance, competitive absorption of light and competing consumption of electron donor. In this proposal, PCT was chosen to measure the performance of the suggested PEC immunosensor. Consequently, the fabricated PEC immunosensor showed a widely detection ranged from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.02 pg/mL (S/N = 3). What is more, the proposed PEC immunosensor possessed satisfactory selectivity, stability and reproducibility. [ABSTRACT FROM AUTHOR]

• MOFs precursors were prepared via microwave irradiation and used as self-sacrificing template. • Fe, Co bimetal embedded nanoporous carbon (Fe-Co/NPC) was prepared by a rapid and scalable strategy. • Fe-Co/NPC composites showed excellent electrochemical performance as ideal electrocatalyst for OER. The development of highly efficient, stable, and low-cost non-noble-metal electrocatalysts for oxygen evolution reactions (OER) is a major challenge for facilitate the efficiency of green energy storage. Bimetallic oxides are considered promising candidates as the electrocatalysts for OER because of their remarkable electrocatalytic activity, good stability, and low cost. In this work, ZIF-67 precursors were prepared via microwave irradiation and used as a self-sacrificing template. We proposed a rapid and scalable strategy to prepare Fe, Co bimetal embedded nanoporous carbon (Fe-Co/NPC) polyhedron composites by thermal decomposition of Fe species incorporated ZIF-67 precursor. Benefiting from the distinctive 3D polyhedron structural and compositional advantages, Fe-Co/NPC with hierarchical porous structure showed excellent electrochemical performance as ideal electrode material for OER. The resulting Fe-Co/NPC displayed outstanding electrocatalytic activity for OER with appreciable onset potential (1.59 V (vs. RHE)), small Tafel slope (53.55 mV dec−1), low over-potential (396 mV) to reach 10 mA cm−2, and excellent durability with negligible loss in current density after 1000 cycles. The current work demonstrated new insight into the design and construction of 3D structured Fe-Co/NPC polyhedron catalysts with highly electrocatalytic activity and good stability for electrocatalysis applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Facile synthesis of ZnCo-ZIFs-derived Zn x Co 3−x O 4 hollow polyhedron for efficient oxygen evolution reduction. Abstract The construction of highly active and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER) is a crucial requirement for green energy utilization. Herein, we report a novel hybrid nanostructure of Zn/Co bimetallic oxide (Zn x Co 3−x O 4) hollow polyhedron through a pyrolysis−oxidation strategy derived from bimetallic Zn, Co-zeolitic imidazolate frameworks (ZnCo-ZIFs) rhombic polyhedral. Benefiting from the synergistic effects between highly active metal oxide and the unique polyhedron structure, the Zn x Co 3−x O 4 hollow polyhedron hybrid displayed outstanding electrocatalytic performances in alkaline media. When the Zn x Co 3 − x O 4 polyhedron was employed as electrocatalysts for OER, a potential as low as 1.66 V (vs. RHE) was required to deliver the current density of 10 mA cm−2 in 1 M KOH, and Zn x Co 3−x O 4 still presented superior activity after continuously working for cyclic voltammetric scanning of 1000 cycles. [ABSTRACT FROM AUTHOR]

A signal-off type photoelectrochemical (PEC) immunosensor based on Ru(bpy) 3 2+ and Bi 2 S 3 co-sensitized ZnTiO 3 /TiO 2 polyhedra as matrix and SiO 2 /PDA-Au as the label of second antibody was proposed for the ultrasensitive detection of procalcitonin (PCT). The hollow ZnTiO 3 /TiO 2 polyhedra called zinc titanium composite hollow structures (ZTCHS) was prepared by hydrothermal method to enhance the utilization of visible light comparing with pure ZnTiO 3 or TiO 2. The unique structure endowed large specific surface areas and satisfying load capacity to ZTCHS. Ru(bpy) 3 2+ and Bi 2 S 3 were utilized to co-sensitize ZTCHS to further strengthen the PEC performance of ZTCHS. It was interesting that the dual-inhibition effects of SiO 2 /PDA-Au further enhanced the sensitivity of proposed PEC immunosensor. On the one hand, the steric hindrance of SiO 2 /PDA effectively restricted electron transfer. On the other hand, Au nanoparticles could absorb visible light to compete with the matrix material. Based on the above aspects, the proposed signal-off type PEC immunosensor possessed a wide linear range from 0.0001 ng mL−1 to 100 ng mL−1 and low detection limit (about 0.03 pg mL−1, S/N = 3), demonstrating the promising application of PEC immunosensor in analysis fields. ► Novel Ru (bpy) 3 2+ and Bi 2 S 3 sensitized ZTCHS polyhedra shows excellent PEC activity. ► The dual-inhibition effects of SiO 2 /PDA-Au reduce distinctly the photocurrent. ► A signal-off type PEC sensor achieves the ultrasensitive detection of procalcitonin. [ABSTRACT FROM AUTHOR]