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Abstract In this work, by using amorphous bimetallic sulfides of CoSnS x Pd as signal amplifier and magnetic material of Fe 3 O 4 @PPy Au as the substrate, we fabricated an electrochemical immunoassay for N terminal prohormone of brain natriuretic peptide (NT pro BNP). CoSnS x was used as the signal amplifier of the immunosensor for the first time, which was synthesized by fast stoichiometric co-precipitation method. The binary sulfide was identified as an amorphous structure and performed apparent electrochemical behavior. The excellent performance of signal marker was induced by the synergistic effect between SnS 2 and cobalt, as well as the loaded Pd nanoparticles (NPs). Both CoSnS x and Pd NPs presented excellent electrocatalytic activity toward H 2 O 2 oxidation. Moreover, the magnetic nanocomposite of Fe 3 O 4 @PPy Au was firmly immobilized on the magnetic glassy carbon electrode (MGCE) by the magnetic force. The magnetic substrate not only performed good electron conductivity, but also improved the stability of the fabricated electrochemical immunosensor. The developed immunosensor for the NT pro BNP detection exhibited a wide linear response (0.1 pg/mL to 50 ng/mL), and low detection limit of 31.5 fg/mL. In addition, the immunosensor held an excellent analysis capability and broad fascinating application for the detection of other biomarkers in medical diagnosis and treatment. Graphical abstract An electrochemical immunosensor based on amorphous bimetallic sulfides of CoSnS x Pd as signal amplifier and magnetic material of Fe 3 O 4 @PPy Au as the substrate for the NT pro BNP detection. fx1 Highlights • A novel electrochemical immunosensor was designed for detecting NT pro BNP. • CoSnS x was first used as the signal amplifier of the immunosensor and performed apparent electrochemical behavior. • The Fe 3 O 4 @PPy Au as matrix was firmly immobilized on the MGCE by the magnetic force. • It achieved an excellent result in human serum sample analysis. [ABSTRACT FROM AUTHOR]

Abstract An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag 2 S sensitized SnO 2 /SnS 2 nanocomposites. Specifically, SnO 2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS 2 , which brought about the sensitization of SnO 2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag 2 S was in-situ growth on the surface of SnO 2 /SnS 2 , which further enhanced the photocurrent response significantly. Therefore, SnO 2 /SnS 2 /Ag 2 S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5 pg mL−1 to 100 ng mL−1, with low limit of detection (0.17 pg mL−1) and limit of quantification (0.56 pg mL−1). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields. Highlights • A label-free PEC immunosensor was developed based on SnO 2 /SnS 2 /Ag 2 S nanocomposites. • SnO 2 /SnS 2 /Ag 2 S nanocomposites exhibited excellent photoelectrochemical performance. • The PEC immunosensor displayed highly sensitive detection toward amyloid β-protein. [ABSTRACT FROM AUTHOR]

In this study, a sensitive sandwich-type electrochemical immunosensor was fabricated for the detection of alpha fetoprotein (AFP) based on Co 3 O 4 @MnO 2 -thionine (Co 3 O 4 @MnO 2 -Th) and the screen printing technique. Meanwhile, the pseudo enzyme-linked immunosorbent assay (pseudo-ELISA) method was applied in fabricating the immunosensor. Screen-printed carbon electrode (SPCE) was applied for achieving the detection of AFP. Simultaneously, the amino functionalized Co 3 O 4 @MnO 2 -Th was employed as secondary label and could greatly improve the electrochemical response signal, which was beneficial for detecting AFP. Differential pulse voltammetry (DPV) was applied for the detection of AFP and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal conditions, the immunosensor exhibited a linear response toward AFP in the range of 0.001–100 ng/mL, with a low detection limit of 0.33 pg/mL. Simultaneously, the proposed immunosensor displayed acceptable selectivity, excellent stability and well reproducibility. Furthermore, this proposed strategy may open up new ideas and find many potential applications in the detection of other tumor markers. [ABSTRACT FROM AUTHOR]

In this work, a highly-efficient competitive method-based electrochemiluminescence (ECL) immunosensor was proposed based on {[Ru(bpy) 3 ][Cu 2x Ni 2(1−x) (ox) 3 ]} n (Cu/Ni/Ru) as luminophor to efficiently detect aflatoxins B1 (AFB1). Cu/Ni/Ru exhibited excellent ECL behavior. While polyethyleneimine capped silicon dioxide (PEI@SiO 2 ) could decrease the ECL performance of Cu/Ni/Ru due that PEI could destroy the structure of Cu/Ni/Ru via producing the complex between PEI and metal ions (Cu(II)/Ni(II)), inducing the release of Ru(bpy) 3 2+ . Since Au nanoparticles can directly combine with antibody and antigen, the Cu/Ni/Ru and PEI@SiO 2 was functionalized by Au nanoparticles. The quantitative detection of AFB1 was based on the competitive binding between AFB1-bovine serum albumin labeled Au-PEI@SiO 2 (Au-PEI@SiO 2 -AFB1-BSA) and free AFB1 with antibody-AFB1 which immobilized on Au-Cu/Ni/Ru. The ECL signal increased with augmenting the concentrations of the free AFB1 due to less Au-PEI@SiO 2 -AFB1-BSA combining with antibodies. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 ng mL −1 to 100 ng mL −1 with a detection limit of 0.0039 ng mL −1 (S/N = 3). The proposed immunosensor also provides a promising approach for ultrasensitive detection of other mycotoxins. [ABSTRACT FROM AUTHOR]

An electrochemiluminescence (ECL) biosensor was developed for detection of Concanavalin A (Con A). Chitosan/Ru(bpy) 3 2+ /silica/Fe 3 O 4 nanomaterials (CRuSi-Fe 3 O 4 ) were synthesized through W/O microemulsion route. The added Fe 3 O 4 nanoparticles can simplify the prepared process and enhance the conductivity of nanomaterials which can increase the ECL intensity of luminophor CRuSi-Fe 3 O 4 . In addition, the layered structure of CRuSi-Fe 3 O 4 can immobilize lots of Con A using glutaraldehyde as the coupling agent which can improve the sensitivity of the biosensor. Then the quenching probe glucose functionalized NiCo 2 S 4 nanoparticles-grown on carboxylic graphene (NiCo 2 S 4 -COOH-rGO@Glu) was anchored on the modified-electrode via the specific carbohydrate-Con A interaction. Here, NiCo 2 S 4 was used to quench the ECL of CRuSi-Fe 3 O 4 , graphene was used to grow NiCo 2 S 4 nanoparticles as carrier materials and glucose was served as the recognition element for bounding Con A. Therefore, a desirable quenching ECL signal was measured with S 2 O 8 2- as the coreactant of CRuSi-Fe 3 O 4 . Under the optimization of determination conditions, a linear response range for Con A from 0.5 pg mL −1 to 100 ng mL −1 was obtained, and the detection limit was calculated to be 0.18 pg mL −1 (S/N=3). [ABSTRACT FROM AUTHOR]

In this work, a novel electrochemical aptasensor was developed for sensitive and specific detection of Hg 2+ based on thymine-Hg 2+ -thymine (T-Hg 2+ -T) structure via application of thionine (Th) as indicator signal. For the fabrication of the aptasensor, streptavidin modified magnetic beads (Fe 3 O 4 -SA) was firmly immobilized onto the magnetic glassy carbon electrode (MGCE) benefited from its magnetic character. Then biotin labeled T-riched single stranded DNA (Bio-ssDNA) connected with Fe 3 O 4 -SA specifically and steadily because of the specific binding capacity between streptavidin and biotin. The stable structure of T-Hg 2+ -T formed in the present of Hg 2+ provided convenience for the intercalation of Th. The detection of Hg 2+ was achieved by recording the differential pulse voltammetry (DPV) signal of Th. Under optimal experimental conditions, the linear range of the fabricated electrochemical aptasensor was 1–200 nmol/L, with a detection limit of 0.33 nmol/L. Furthermore, the proposed aptasensor may find a potential application for the detection of Hg 2+ in real water sample analysis. [ABSTRACT FROM AUTHOR]

In this work, an ultrasensitive electrochemical aptasensor for the detection of thrombin was developed based on Au nanoparticles decorated graphene sheet (Au@GS) and CoPd binary nanoparticles (CoPd NPs). A sulfydryl-labeled thrombin capture probe (Apt1) and a biotin-labeled thrombin reporter probe (Apt2) were designed to achieve a sandwich-type strategy. Au@GS was used as a sensing platform for the facile immobilization of Apt1 through Au–S bond, forming a sensing interface for thrombin. The specific recognition of thrombin induced the attachment of Apt2–CoPd NPs to the electrode. The labeled CoPd NPs showed good catalytic properties toward the reduction of H 2 O 2 , resulting in an amperometric signal. The amperometric response was correlated to the thrombin concentration in sample solutions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the aptasensor. A linear response to thrombin in the range of 0.01–2.00 ng mL −1 with a low detection limit (5 pg mL −1 ) was achieved. The proposed aptasensor showed good selectivity, good reproducibility and acceptable stability. This proposed strategy may find many potential applications in the detection of other biomolecules. [ABSTRACT FROM AUTHOR]

Abstract A sandwich-type electrochemical immunosensor for prostate-specific antigen (PSA) detection was constructed. In this sensing platform, palladium nanoparticles (Pd NPs) loaded electroactive amino-zeolitic imidazolate framework-67 (Pd/NH 2 -ZIF-67) nanocomposite is utilized as a novel redox mediator. Pd NPs, as the labeling signal molecule, owns good biocompatibility and excellent catalytic performance. Meanwhile, the electroactive ZIF-67 with lamellar structures serves not only as a carrier of Pd NPs but also as a synergistic catalyst of palladium to decompose H 2 O 2. Amperometric method is used to determine the current signal generated on the electrode surface, which is conducive to achieve the quantitative determination of PSA. Under optimum conditions, the proposed immunosensor shows a wide detection range from 100 fg mL–1 to 50 ng mL–1 with a low detection limit of 0.03 pg mL–1, featuring favorable selectivity, repeatability and stability. This proposed immunosensor is expected to be a powerful tool for realizing quantitative detection of PSA and other biomarkers in actural sample analysis. Highlights • Electrochemical immunoassay is proposed for detection of PSA based on Pd/NH 2 -ZIF-67. • The response signal is amplified by the synergetic effect between Pd and Co2+/3+. • The immunosensor exhibits a low detection limit of 0.03 pg mL-1 for PSA detection. [ABSTRACT FROM AUTHOR]

Abstract In this study, we propose a SnO 2 /CdCO 3 /CdS-based label-free photoelectrochemical (PEC) immunosensor for the sensitive quantification of amyloid β-protein (Aβ) which plays a critical role in the early diagnosis of Alzheimer's disease. Under specific pH conditions, SnO 2 /CdCO 3 /CdS was first designed and successfully synthesized with simple one-pot method. The synthesis of SnO 2 /CdCO 3 /CdS circumvents the trouble of traditional composite materials to be gradually compounded, saving a lot of time and energy. The synthesis mechanism of SnO 2 /CdCO 3 /CdS nanocomposite was also deeply explored. Moreover, thanks to the matched energy levels of its three components, SnO 2 /CdCO 3 /CdS nanocomposite exhibited enhanced photocurrent intensity, which is dozens of times bigger than any of its components, thus making it an excellent photoactive matrix for PEC immunosensor. Under optimal conditions, the as-constructed PEC immunosensor manifested a broad linear range (0.1 pg mL−1 to 100 ng mL−1) with a low detection limit (LOD, 0.05 pg mL−1, S/N = 3). High selectivity, coupled with good stability, allowed the developed PEC immunosensor to be applied in the clinical detection of Aβ or other biomarkers in human serum. Highlights • SnO 2 /CdCO 3 /CdS was first synthesized by a simple one-pot approach. • The mechanism of SnO 2 /CdCO 3 /CdS formation was discussed. • A label-free photoelectrochemical immunosensor was fabricated to detect Aβ. • The photoelectrochemical immunosensor reveals good stability and high sensitivity. [ABSTRACT FROM AUTHOR]

Abstract This work reported curcumin quenched electrochemiluminescence (ECL) behavior of luminol with H 2 O 2 as coreactant. To achieve excellent ECL signal, luminol was anchored on Au functionalized MoS 2 /Bi 2 S 3 nanorods (Luminol-Au@MoS 2 /Bi 2 S 3), which not only exhibited super catalysis for H 2 O 2 decomposition to enhance the ECL intensity of luminol/H 2 O 2 system, but also offered a satisfying substrate material for grafting more Au nanoparticles via Au-S binding which was used to adsorb luminol and primary antibodies. As an antioxidant, the hydrophobicity of curcumin limited its bioavailability. Herein, curcumin was conjugated with ZnO nanomaterials (ZnO-CR) to increase its dispersity in water which can make it more bioavailable. Moreover, the possible quenching mechanism between luminol/H 2 O 2 system and ZnO-CR was ascribed to the consumption of superoxide radical (O 2 •−) and energy transfer. The consumption amount of O 2 •− was calculated to be 1.2092 μM/mL through superoxide anion free radical detection kit. Besides, polydopamine was self-polymerized on the surface of ZnO-CR (PDA@ZnO-CR) to anchor secondary antibodies. In optimum parameter, the ECL immunosensor exhibited excellent performance for amyloid-β(Aβ) proteins detection with a wide detection range from 0.05 pg mL−1 to 10 ng mL−1 and a low detection limit of 21 fg mL−1 (S/N = 3). Highlights • Curcumin quenched ECL behavior of luminol with H 2 O 2 as coreactant. • Luminol was anchored on Au functionalized MoS 2 /Bi 2 S 3 nanorods through Au–NH 2 bond. • Curcumin conjugated with ZnO nanomaterials to increase its dispersity in water. • The quenching mechanism was ascribed to consumption of O 2 −• and energy transfer. • The sandwich ECL immunosensor was used to detect amyloid-β proteins. [ABSTRACT FROM AUTHOR]

Abstract In this work, 3,4,9,10-perylenetetracar-boxylic acid (PTCA) as luminophor was grafted on the surface of graphene oxide (PTCA-GO) directly. GO exhibited large specific surface area and excellent electrical conductivity which can immobilize large amounts of PTCA to improve the electrochemiluminescence (ECL) efficiency. Moreover, gold nanoparticles (Au NPs) were anchored on the surface of PTCA-GO to immobilize primary antibodies (Ab 1) via Au-NH 2 bond and enhance the electron transport of PTCA-GO. CuS was used as a novel co-reaction accelerator in PTCA-K 2 S 2 O 8 system to label secondary antibodies (Ab 2), which can react with the coreactant (K 2 S 2 O 8) to produce more SO 4 •-. SiO 2 nanospheres with large specific surface area were used to load a mass of CuS and Au NPs, which can directly combine with Ab 2 and accelerate the ECL emission remarkably. Therefore, a novel sandwich-type ECL immunosensor was fabricated successfully for amyloid-β protein (Aβ) detection. Under the optimal condition, a wide detection range from 50 fg/mL to 25 ng/mL and a low detection limit of 18 fg/mL (S/N = 3) were obtained. Featuring favorable specificity, stability and reproducibility, the strategy can be a powerful analytical tool in sensitive trace detection of biomolecules in clinical analysis. Highlights • PTCA was grafted on Au@GO which improved the ECL behavior. • CuS acted as co-reaction accelerator to amplify the ECL signal. • CuS reacted with the coreactant (S 2 O 8 2-) to produce more SO 4 •-. • Amyloid-β protein was ultrasensitively detected. [ABSTRACT FROM AUTHOR]

A new, photoelectrochemical immunosensor was proposed on the basis of the La-CdS/3D ZnIn 2 S 4 /Au@ZnO sensitization structure for detection of aminoterminal pro-brain natriuretic peptides (NT-proBNP). The Au@ZnO-modified electrode was first assembled with 3D ZnIn 2 S 4 , and then further deposited with lanthanum doped cadmium sulfide (La-CdS) via successive ionic layer adsorption and reaction strategy. The Au@ZnO has excellent photoelectric activity and electrical conductivity. The ZnIn 2 S 4 with 3D architectures not only exhibit high photocurrent intensity under visible-light irradiation but also have large surface for the La-CdS deposition. Meanwhile, the La-CdS doped structure could depress the charge recombination, which effectively promotes separation of the generated electron-hole (e - /h + ) pairs and consequently enhances the photocurrent conversion efficiency. The polydopamine (PDA) was used not only as a cross-linker reagent for the immobilization of the anti-NT-proBNP but also as an electron donor for promoting the photo-generated e - /h + separation of the semiconductors. Under optimal conditions, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 0.32 pg mL −1 and a wide linear range from 0.8 pg mL −1 to 45 ng mL −1 for target NT-proBNP detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising strategy for the detection of other important tumor markers. [ABSTRACT FROM AUTHOR]

A novel electrochemiluminescence (ECL) signal-off strategy based on CuS in situ grown on reduced graphene oxide (CuS-rGO) quenching luminol/H 2 O 2 system was firstly proposed. Luminol was grafted on the surface of Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 nanoflowers (Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 ) which exhibited excellent catalytic effect towards the reduction of H 2 O 2 to enhance the ECL intensity of luminol. Cu 3 (PO 4 ) 2 nanoflowers showed large surface area which can immobilize more Fe 3 O 4 and Au nanoparticles. The quenching mechanism of CuS-rGO was due to ECL resonance energy transfer (RET). The spectral overlap between fluorescence spectrum of Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 and UV–vis absorption spectrum of CuS-rGO revealed that resonance energy transfer was possible. Au nanoparticles were immobilized on the surface of CuS-rGO to capture secondary antibodies. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed. Under the optimal conditions, the immunosensor showed excellent performance for N-terminal pro-brain natriuretic peptide (NT-proBNP) detection with a wide detection range from 0.5 pg mL −1 to 20 ng mL −1 and a low detection limit of 0.12 pg mL −1 (S/N = 3). The prepared NT-proBNP immunosensor displayed high sensitivity, excellent stability and good specificity. [ABSTRACT FROM AUTHOR]

An ultrasensitive sandwich-type photoelectrochemical (PEC) immunosensor was constructed for the detection of prostate specific antigen (PSA). In this work, Au-nanoparticle-loaded tungsten oxide (WO 3 -Au) hybrid composites was applied as PEC sensing platform, while Ca ions doped CdSe equipped on the conducting framework of reduced graphene oxide (rGO-Ca:CdSe) nanocomposites were employed as the signal amplification probe. As for WO 3 -Au, massive Au nanoparticles were formed on the surface of WO 3 without any additional reducing agent, providing a novel nanocarriers for anchoring plenty of the primary antibodies due to the large specific surface area and good biocompatibility by chemical bonding between Au nanoparticles and -NH 2 of antibodies. Besides, the incorporation of the rGO and the doping of Ca ions could improve the conductivity and hinder the recombination of electron-hole pairs of CdSe nanoparticles effectively, thereby enhancing the photocurrent conversion efficiency. Based on the sandwich immunoreaction, the primary antibody was immobilized onto WO 3 -Au substrate, after the formed rGO-Ca:CdSe labels were captured onto the electrode surface via the specific antibody-antigen interaction, the photocurrent intensity could be further enhanced due to the sensitization effect. Under the optimal conditions, the proposed PEC immunosensor shows a linear relationship between photocurrent variation and the logarithm of PSA concentration in the wide range of 5 pg mL −1 to 50 ng mL −1 with a low detection limit of 2.6 pg mL −1 (S/N=3). Moreover, it also presented good stability and acceptable specificity, indicating the potential applications in clinical diagnostics. [ABSTRACT FROM AUTHOR]

In this work, an ultrasensitive electrochemical sensor was developed for detection of Hg 2+ . Gold nanoparticles decorated bovine serum albumin reduction of graphene oxide (AuNP-BSA-rGO) were used as subsurface material for the immobilization of triple-helix DNA. The triple-helix DNA containing a thiol labelled single-stranded DNA (sDNA) and a thymine-rich DNA (T-rich DNA), which could be unwinded in the present of Hg 2+ to form more stable thymine–Hg 2+ –thymine (T–Hg 2+ –T) complex. T–Hg 2+ –T complex was then removed and the sDNA was left on the electrode. At this time, gold nanoparticle carrying thiol labelled cytosine-rich complementary DNA (cDNA-AuNP) could bind with the free sDNA. Meanwhile, the other free cDNA on AuNP could bind with each other in the present of Ag + to form the stable cytosine–Ag + –cytosine (C–Ag + –C) complex and circle amplification. Plenty of C–Ag + –C could form silver nanoclusters by electrochemical reduction and the striping signal of Ag could be measured for purpose of the final electrochemical detection of Hg 2+ . This sensor could detect Hg 2+ over a wide concentration range from 0.1 to 130 nM with a detection limit of 0.03 nM. [ABSTRACT FROM AUTHOR]

An ultrasensitive photoelectrochemical (PEC) aptasensor based on a novel signal amplification strategy was developed for the quantitative determination of microRNA (miR)-155. CH 3 NH 3 PbI 3 quantum dots (QDs) functionalized ZnO nanosheets (NSs) were employed as the light harvester. Owing to the synergetic effect between CH 3 NH 3 PbI 3 QDs and ZnO NSs, ZnO@CH 3 NH 3 PbI 3 can provide an obviously increasing PEC signal by forming the heterojunction. Due to the larger steric hindrance, the sensitive decrease of the PEC signal can be achieved by the specific recognition between the primers and ssDNA of miR-155. In this sense, this developed aptasensor can achieve a high sensitivity (especially in the presence of the low concentrations of miR-155) and a wide detection range (0.01 fmol/L to 20,000 pmol/L). Under the optimal conditions, the proposed aptasensor offered an ultrasensitive and specific determination of miR-155 down to 0.005 fmol/L. This aptassay method would open up a new promising platform at ultralow levels for early diagnose of different miRNA. [ABSTRACT FROM AUTHOR]

The preparation of highly efficient electrochemiluminescence (ECL) illuminants is an effective method to improve the sensitivity and repeatability of ECL immunoassay. In this study, we prepared an ECL immunoassay for efficient and sensitive detection of neuron-specific enolase (NSE) by linking carboxylated Ru(bpy) 3 2+ to an iron-based metal-organic framework (NH 2 -MIL-88 (Fe)) via an amide bond as an ECL signal probe. NH 2 -MIL-88 (Fe) possesses a large number of amino groups that can catalyze the co-reactant S 2 O 8 2−, which generates abundant reaction intermediates SO 4 •- around Ru(dcbpy) 3 2+, reduces the loss of material transport and energy transfer between SO 4 •- and Ru(dcbpy) 3 2+, and significantly enhances the ECL signal. We used polyaniline-intercalating vanadium oxide (PVO) nanosheets as the substrates to capture NSE owing to the large specific surface area and extraordinary conductivity of the nanosheets. Similarly, PVO nanosheets also possess abundant amino groups, which can act as co-reaction promoters to catalyze the reaction of S 2 O 8 2− to SO 4 •-, enhancing the ECL signal of the immunoassay. Therefore, we constructed a dual-enhanced ECL immunoassay with Ru(dcbpy) 3 2+/NH 2 -MIL-88 (Fe) and PVO as the signal probe and substrate, respectively, which exhibited excellent sensitivity and selectivity for detecting NSE. This study offers an effective strategy for ultrasensitive detection of trace proteins using ECL immunoassays. [Display omitted] • Nanocomposites prepared by the synergistic effect of R and N show excellent ECL response. • PVO and NH2-MIL-88 (Fe) can catalyze co-reactants and enhance ECL response. • Polyaniline intercalating vanadium oxide (PVO) with catalytic properties were used to capture the primary antibody. • A novel double enhanced effect-based sandwich ECL immunosensor was developed for high sensitivity NSE detection. [ABSTRACT FROM AUTHOR]

An efficient strategy for the sensitive detection of Cd 2+ and Cu 2+ on the same sensing platform was first developed based on the photocurrents generated from the electrodeposited Zn doped CdS (CdZnS) film. The enhancement of the photocurrents, which was directly obtained from the in situ electrodeposited CdZnS on ITO with the gradual addition of Cd 2+ , was used an indicator for the content of Cd 2+ with theoretical and technical simplicity. Moreover, the electrodeposited CdZnS was further applied to sensing of Cu 2+ based on the interaction between Cu 2+ and S 2− by immersing the hetero-structural film electrode into a Cu 2+ -containing sample for an appropriate time, leading to decrease the photocurrent of CdZnS. The decrease extent of photocurrent was depended on the concentration of Cu 2+ in the sample solution. Due to the sensitivity of the photoelectrochemical (PEC) sensor was enhanced obviously through the doping of Zn, the present electrodeposited PEC method demonstrated acceptable linear range of 10 −9 –10 −2 M and 10 −8 –10 −4 M, with low detection limit down to 0.35 nM and 3 nM for Cd 2+ and Cu 2+ respectively, which were lower than the Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines. The proposed CdZnS-based PEC strategy achieved two metal ions detection on the same sensing platform, which had positive and significant effect on solving the common problems, such as time-consuming, high cost, complex operation and high detection limit in the detection of metal ions. In addition, the proposed PEC device was further successfully applied to an assay of Cd 2+ and Cu 2+ in water sample. [ABSTRACT FROM AUTHOR]