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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]

One-dimensional ZnO@In 2 O 3 core@shell nanofibers (CSNFs) were synthesized via a facile coaxial electrospinning method followed by high-temperature pyrolysis treatment. The obtained nanofibers have a well-defined core@shell structure with ZnO as the core and In 2 O 3 as the shell. Compared with the pure ZnO nanofibers and pure In 2 O 3 nanofibers, the ZnO@In 2 O 3 CSNFs based sensor presents the highest response to ethanol (31.87 at 100 ppm) at an operating temperature of 225 °C, which can be ascribed to the formation of a completely electron depletion layer in In 2 O 3 shell. Moreover, the ZnO@In 2 O 3 CSNFs based sensor also demonstrates outstanding selectivity, excellent stability and low detection limitation (∼5 ppm) to ethanol vapor. The ultraviolet photoelectron spectroscopy confirms a type-II heterojunction formed at the interface of ZnO core and In 2 O 3 shell. The main mechanism for the enhanced performance of ZnO@In 2 O 3 CSNFs gas sensor is the depletion modulating of In 2 O 3 shell layer in electron transfer. These results are valuable for the practical application of ZnO@In 2 O 3 CSNFs in ethanol detection. [ABSTRACT FROM AUTHOR]

• The signal indicator and matrix, Fe 3 S 4 -Pd, displayed excellent electrocatalytic activity for H 2 O 2 redox reaction. • Magnetic glassy carbon electrode was used to firmly immobilized the magnetic Fe 3 S 4 -Pd to achieve satisfied stability. • PBG nanomaterial played a role as the electron blocking label that realized a sensitive variation of current signal. • The signal-off sensing platform was successfully constructed, with a low detection limit of 130 fg/mL. Herein, a sandwich-type electrochemical (EC) immunosensor is proposed based on a special signal-off mode for the sensitive detection of procalcitonin (PCT) by utilizing Fe 3 S 4 loaded with Pd nanoparticles (Fe 3 S 4 -Pd) as a signal indicator and matrix and functionalized pineal mesoporous bioactive glass (PBG) as the label for signal amplification. Fe 3 S 4 -Pd not only shows excellent electrocatalytic activity for the H 2 O 2 redox reaction but is also firmly immobilized on a magnetic glassy carbon electrode due to its excellent magnetic properties; because of the above features, this immunosensor exhibits excellent sensitivity and stability, respectively. Glutaraldehyde is used as a cross-linking agent to bond the secondary antibodies (Ab 2) with PBG. It is worth mentioning that the electron transfer rate between the electrolyte and electrode is decreased significantly by PBG-Ab 2 ; thus, a sensitive variation in the current signal is observed, and a further improvement in the sensitivity of the immunosensor is realized. More importantly, the proposed signal-off sensing system has a wide linear detection range of 500 fg/mL to 50 ng/mL for PCT and a low detection limit of 130 fg/mL, which promotes it as a promising detection method for the sensitive detection of other biomarkers. [ABSTRACT FROM AUTHOR]

• A PEC aptamer sensor for 17β-estradiol detection was introduced. • The Mo doped porous BiVO 4 nanoarray/Bi 2 S 3 as sensing platform for immobilization of aptamer. • The Mo-p BiVO 4 /Bi 2 S 3 presented a high PEC signal by supplying additional free electrons. • The nanoarray structure provided large specific surface area and large number of binding sites. • The PEC aptamer sensor exhibited a low detection limit of 3.2 × 10−4 pM. A new porous nanoarray is constructed as sensing platform of photoelectrochemical (PEC) biosensor for detection of 17β-estradiol (E2) by using aptamer. The molybdenum (Mo) ions doped into porous bismuth vanadate (Mo-p BiVO 4) nanoarray by electrodeposition of BiOI nanoarray. Then, the bismuth sulfide (Bi 2 S 3) nanoparticles are grown in-situ on the surface of Mo-p BiVO 4 by the self-sacrificial synthesis method to form novel Mo-p BiVO 4 /Bi 2 S 3 heterojunction. Herein, the Mo-p BiVO 4 /Bi 2 S 3 heterojunction presents a high PEC signal because of Mo-p BiVO 4 could increase electron-hole separation yield by supplying additional free electrons, furthermore the heterojunction of Mo-p BiVO 4 /Bi 2 S 3 could promote ultrafast transfer of charge and inhibit the recombination of e−/h+ pairs by presenting cascade band-edge levels under irradiation of the visible light. Moreover, the nanoarray structure has large specific surface area, which could accelerate electron transfer and provide large number of binding sites to immobilize aptamer. This PEC aptamer sensor exhibits high sensitivity with a detection limit 3.2 × 10-4 pM and a good photocurrent response toward target E2 in the range of 1 × 10-3 - 5 × 102 pM. Good specificity and stability are acquired for analysis of E2 in human urine. Importantly, this designed sensor platform of Mo-p BiVO 4 /Bi 2 S 3 heterojunction provides a new promising application for other environmental estrogen analysis. [ABSTRACT FROM AUTHOR]

• A sandwich-type immunosensor for detection of PCT was designed. • CeO 2 -CuO-Au as platform can promote electron transfer. • Au@Ag-Th as signal labels can further effectually amplify the current signal. • The immunosensor presents prominent performance for PCT detection. Procalcitonin (PCT) is a kind of protein exists in the human blood. If the human bodies are infected with bacteria, fungi or parasites, the value of PCT in blood will be significantly raised. Thereby, we report an electrochemical immunosensor for measurement of PCT using gold nanoparticle (Au NP) decorated CeO 2 -CuO (CeO 2 -CuO-Au) as the platform and thionine modified Au@Ag heterojunction nanorods (Au@Ag-Th) as signal labels. Au NP decorated CeO 2 -CuO exhibits high surface area, high activity and good biocompatibility, which can immobilize more primary antibodies and promote electron transfer. The Au@Ag-Th provides good active sites to link secondary antibodies, further effectually amplify the current signal. This immunosensor exhibits a well-pleasing response with a limit detection of 0.17 pg mL−1 and linear detection between 0.5 pg mL−1 and 50 ng mL−1. Meanwhile, the high sensitivity, excellent specificity and acceptable human serum samples testing results of this method lead to potential applications in diagnosis of bacterial infections. [ABSTRACT FROM AUTHOR]