Dual-mode biosensor using Tb-Cu MOF@Au nanoenzyme to effectively quench the photocurrent of Bi2O3/Bi2S3/AgBiS2 heterojunction and emit fluorescence for neuron-specific enolases detection.

A novel dual-mode biosensor was constructed for the ultrasensitive detection of neuron-specific enolase (NSE), utilizing Tb-Cu MOF@Au nanozyme as the signal label to effectively quench the photoelectrochemical (PEC) signals of Bi2O3/Bi2S3/AgBiS2 composites and initiate fluorescent (FL) signals. First, Bi2O3/Bi2S3/AgBiS2 heterojunction with excellent photoelectric activity was selected as the substrate material to provide a stable photocurrent. The well-matched energy levels significantly enhanced the separation and transfer of photogenerated carriers. Second, a strategy of consuming ascorbic acid (AA) by Tb-Cu MOF@Au nanozyme was introduced to improve the sensitivity of the PEC/FL biosensor. Tb-Cu MOF@Au not only could catalyze the oxidation of AA, but the steric effect further reduced the contact of AA with the substrate. More importantly, in the presence of H2O2, a significant fluorescence was produced from Tb3+ sensitized by the oxidation products of AA. Based on the above strategies, a highly stable and sensitive dual-mode biosensor was proposed for accurate NSE determination. Third, the developed dual-mode biosensor demonstrated excellent performance in detecting NSE. In this study, the PEC method demonstrated a wide detection range from 0.00005 to 200 ng/mL with a low detection limit of 20 fg/mL. The FL method exhibited a linear range from 0.001 to 200 ng/mL with a detection limit of 0.65 pg/mL. The designed biosensor showed potential practical implications in the accurate detection of disease markers.

A novel split PEC sensor based on magneto-optic nanostructure and photocurrent polarity switching strategy.

BACKGROUND: Photoelectrochemical (PEC) sensors have attracted much attention due to their low cost, simple instrumentation and high sensitivity. However, conventional PEC sensors require layer-by-layer modification of the photoelectrode surface, which has the disadvantages of being time-consuming and unstable. In addition, complex interfering substances in real samples may lead to false-positive or false-negative detection results. It was thought that the above drawbacks could be eliminated by the construction of a polarity inversion PEC sensor. In this work, a magnetically separated PEC sensor was constructed for the detection of Carcinoembryonic antigen (CEA). RESULTS: During the experiment, the construction of the sensor was used for sensitive detection of CEA. In the experimental process, Fe3O4@SiO2@CdS, a semiconductor material with magnetic properties, was chosen as the substrate material, and ZnO/CuO was used as the marker on the DNA2 molecule, and a split magnetic separation PEC sensor was constructed, which was used to realize the sensitive detection of CEA. Eventually, the detection range of the sensor for CEA detection is 1-10000 pg/mL, with the detection limit of 0.34 pg/mL. Additionally, the PEC sensor has the advantages of high speed, high efficiency, high sensitivity, good specificity, and high stability. The sensing platform constructed in this work can also be extended to detect other targets, which provides a new idea for PEC sensing platforms. SIGNIFICANCE: In this experiment, we developed a split PEC immunosensor based on magneto-optic nanostructure and photocurrent polarity switching strategy. Specifically, the proposed magnetic nanostructure Fe3O4@SiO2@CdS-DNA1 exhibits good paramagnetism and dispersion ability. By magnetic separation process, the PEC signals of opposite polarity can be obtained.

Development of reusable electrochemiluminescence sensing microchip for detection of vomitoxin.

In this work, a reusable DNA sensing microchip was developed for detection of vomitoxin (deoxynivalenol, DON) in sorghum using Cd-based core-shell CdSe@CdS quantum dots (QDs) as promising electrochemiluminescence (ECL) emitter. The size-adjustable aqueous phase CdSe@CdS QDs were prepared through homogeneous method, exhibiting strong cathodic ECL emission with a central wavelength of 520 nm in S2O82- coreactant. And gold nanoparticles-modified iron cobalt cyanide hydrate (Fe-Co-Au) was introduced as an accelerator to amplify the ECL signal. ECL signal was quenched after the formation of a double-stranded (dsDNA) S1-S2 by generating an electron transfer system between the emitter and ferrocene (Fc), which are modified on the aptamer (ssDNA S1) and its complement sequence (ssDNA S2), respectively. When the target DON is presence, the aptamer ssDNA S1 will bind to the DON and trigger the unbinding of double strands DNA and the release of the ssDNA S2, thus the signal can be generated. This approach offers a feasible method for the detection of DON within the range of 1 ng/mL to 200 ng/mL.

Ultrasensitive Electrochemiluminescence Biosensor Based on Efficient Signal Amplification of Copper Nanoclusters Induced by CaMnO3 for CD44 Trace Detection.

Metal nanoclusters (Me NCs) have become a research hotspot in the field of electrochemiluminescence (ECL) sensing analysis. This is primarily attributed to their excellent luminescent properties and biocompatibility along with their easy synthesis and labeling characteristics. At present, the application of Me NCs in ECL mainly focuses on precious metals, whose high cost, to some extent, limits their widespread application. In this work, Cu NCs with cathode ECL emissions in persulfate (S2O82-) were prepared as signal probes using glutathione as ligands, which exhibited stable luminescence signals and high ECL efficiency. At the same time, CaMnO3 was introduced as a co-reaction promoter to increase the ECL responses of Cu NCs, thereby further expanding their application potential in biochemical analysis. Specifically, the reversible conversion of Mn3+/Mn4+ greatly promoted the generation of sulfate radicals (SO4•-), providing a guarantee for improving the luminescence signals of Cu NCs. Furthermore, a short peptide (NARKFYKGC) was introduced to enable the fixation of antibodies to specific targets, preventing the occupancy of antigen-binding sites (Fab fragments). Therefore, the sensitivity of the biosensor could be significantly enhanced by releasing additional Fab fragments. Considering the approaches discussed above, the constructed biosensor could achieve sensitive detection of CD44 over a broad range (10 fg/mL-100 ng/mL), with an ultralow detection limit of 3.55 fg/mL (S/N = 3), which had valuable implications for the application of nonprecious Me NCs in biosensing analysis.

Rational Control of Near-Infrared Colloidal Thick-Shell Eco-Friendly Quantum Dots for Solar Energy Conversion.

Thick-shell colloidal quantum dots (QDs) are promising building blocks for solar technologies due to their size/composition/shape-tunable properties. However, most well-performed thick-shell QDs suffer from frequent use of toxic metal elements including Pb and Cd, and inadequate light absorption in the visible and near-infrared (NIR) region due to the wide bandgap of the shell. In this work, eco-friendly AgInSe2 /AgInS2 core/shell QDs, which are optically active in the NIR region and are suitable candidates to fabricate devices for solar energy conversion, are developed. Direct synthesis suffers from simultaneously controlling the reactivity of multiple precursors, instead, a template-assisted cation exchange method is used. By modulating the monolayer growth of template QDs, gradient AgInSeS shell layers are incorporated into AgInSe2 /AgInS2 QDs. The resulting AgInSe2 /AgInSeS/AgInS2 exhibits better charge transfer than AgInSe2 /AgInS2 due to their favorable electronic band alignment, as predicted by first-principle calculations and confirmed by transient fluorescence spectroscopy. The photoelectrochemical cells fabricated with AgInSe2 /AgInSeS/AgInS2 QDs present ≈1.5-fold higher current density and better stability compared to AgInSe2 /AgInS2 . The findings define a promising approach toward multinary QDs and pave the way for engineering the QDs' electronic band structures for solar-energy conversion.

Bandgap-Regulated Electrochemiluminescence Enhancement Strategy for Florfenicol Detection Based on ZrCuO3: A Multimodal Luminophore.

The low electrochemiluminescence (ECL) efficiency issue of zirconia (ZrO2) has been a pressing problem since its discovery. In this study, a bandgap-regulated ECL enhancement strategy was developed to improve the ECL efficiency of ZrO2. Specifically, through the calcination of metal-organic frameworks (MOFs), the MOF-derived bimetallic oxide ZrCuO3 was synthesized. Compared to ZrO2, the synthesized ZrCuO3 exhibited a narrower bandgap and higher electron transfer efficiency, leading to enhanced ECL efficiency. Further investigation of the ECL emitter revealed that ZrCuO3 exhibited multimodal ECL emission: annihilation ECL and co-reactant participation ECL (including anodic ECL with tripropylamine as a co-reactant and cathodic ECL with K2S2O8 as a co-reactant). The anodic ECL with the highest efficiency was selected as the main mode for detecting the target in the aptasensor. Annihilation ECL and cathodic ECL served as alternative modes to ensure stability and continuity of the sensing system. Based on the bandgap-regulated strategy of ZrCuO3, a sensing chip with ITO as the working electrode was designed for the sensitive detection of florfenicol (FF). The constructed signal "off-on-off" aptasensor exhibited excellent detection performance for FF in the range of 0.0005-200 ng/mL. The proposed method provided a novel strategy for the analysis of other antibiotics or biomolecules.

A split-type photoelectrochemical immunosensing platform based on atom-efficient cation exchange for physiological monitoring.

Ultrasensitive and accurate physiological monitoring is of great significance for disease diagnosis and treatment. In this project, an efficient photoelectrochemical (PEC) split-type sensor on the basis of controlled release strategy was established with great success. Heterojunction formation between g-C3N4 and Zn-doped CdS improved the visible light absorption efficiency, reduced carrier complexation, improved the PEC signal, and increased the stability of the PEC platform. Compared to the traditional model of immunosensors, the process of antigen-antibody specific binding was done in a 96 microplate, and the sensor separated the immune reaction from the photoelectrochemical conversion process, eliminating mutual interference. Cu2O nanocubes were used to label the second antibody (Ab2), and acid etching using HNO3 released a large amount of divalent copper ions, which exchanged cations with Cd2+ in the substrate material, causing a sharp drop in photocurrent and improving the sensitivity of the sensor. Under the optimized experimental conditions, the PEC sensor based on the controlled release strategy for CYFRA21-1 target detection had a wide concentration linear range of 5 × 10-5 to 100 ng/mL with a low detection limit of 0.0167 pg/mL (S/N = 3). This intelligent response variation pattern could also offer the possibility of additional clinical applications for other target detection.

An electrochemiluminescence insulin sensing platform based on the molecular recognition properties of cucurbit[7]uril.

The establishment of new mechanisms for target identification and signal amplification continues to drive innovation in electrochemiluminescence (ECL) sensing platforms. In this paper, a novel ECL insulin sensing platform was constructed by utilizing the molecular recognition properties of cucurbit[7]uril. Specifically, the macrocyclic host molecule cucurbit[7]uril was immobilized on the surface of the sensing platform as an identification probe, which could selectively capture insulin according to the inherent properties of the protein N-terminal. Introducing the rigid molecule cucurbit[7]uril into the sensing interface could reduce the influence of the environmental parameters on the sensing system, which provides a reliable guarantee for the accurate detection of insulin. Furthermore, gold nanoclusters were modified by utilizing the molecular recognition properties of cucurbit[7]uril, and used as anode signal probes for ECL sensing platform. The macrocyclic molecules cucurbit[7]uril passivated the surface of the nanoclusters, inhibited the non-radiative relaxation and improved the physical stability of the luminophore, leading to a significant increase in the sensitivity and stability of the ECL probe. The ECL sensing platforms exhibited a linear range from 50.00 fg/mL to 100.0 ng/mL, with a detection limit of 5.44 fg/mL. This study revealed the critical role of cucurbit[7]uril in target recognition and signal amplification, extending the scope of supramolecular applications in ECL.

Dual Direct Z-Scheme Heterojunction with Stable Electron Supply to a Au/PANI Photocathode for Ultrasensitive Photoelectrochemical and Electrochromic Visualization Detection of Ofloxacin in a Microfluidic Sensing Platform.

A novel dual-mode microfluidic analytical device integrating self-powered photoelectrochemical (PEC) sensing with electrochromic visualization analysis was developed for ultrasensitive ofloxacin (OFL) detection. First, an advanced dual direct Z-scheme BiVO4@Ni-ZnIn2S4/Bi2S3 (BVZIS) heterojunction was designed as a photoanode matrix to steadily provide electrons. The dual Z-scheme structure formed in photoactive BVZIS composites greatly accelerated the migration of electrons. In addition, the doping of Ni in ZnIn2S4 markedly enhanced the optical absorption and promoted the separation of the photocarrier. Second, electrochromic material polyaniline-modified Au (Au/PANI) was first electrodeposited on the photocathode for immobilizing aptamers and realizing visualized readout. On the one hand, Au/PANI with excellent conductivity could receive electrons from the photoanode without external energy supply. On the other hand, PANI would be rapidly reduced by the received electrons and change its color from blue to green obviously. With the increase in OFL, the increased steric hindrance resulted in the significant decline in the PEC signal and RGBgreen value. Third, wide linear ranges of PEC (0.05 pg/mL to 150 ng/mL) and electrochromic technique (0.1 pg/mL to 100 ng/mL) as well as low detection limits of PEC (18 fg/mL) and electrochromic (30 fg/mL) sensors could achieve the ultrasensitive detection of OFL in milk and river water.

Tunable 0D/2D/2D Nanocomposite Based on Green Zn-Doped CuInS2 Quantum Dots and MoS2/rGO as Photoelectrodes for Solar Hydrogen Production.

Charge separation, transmission, and light absorption properties are critical to determining the performance of photoelectrochemical (PEC) devices. An important strategy to control such properties is based on using heterostructured materials. Herein, a tunable zero-dimensional (0D)/two-dimensional (2D) heterostructure is designed based on quantum dots (QDs) and 2D nanosheets (NSs). Specifically, eco-friendly Zn-doped CuInS2 QDs prepared by hot injection were anchored on hierarchical (2D/2D) MoS2/rGO (MG) NSs through a facile sonication-assisted method to develop a 0D/2D/2D heterojunction-based photoelectrode for solar hydrogen production. The interfacial structure and band alignment between the proposed 0D QDs and 2D/2D MG NSs were engineered by modulating the Zn molar ratio during the QD synthesis. As proof of concept, the optimized 0D/2D/2D photoanode exhibits almost five times higher PEC activity than MG/CuInS2 and MoS2/Zn-CuInS2 NSs due to the enhanced light absorption, efficient charge separation, and transmission. Zn doping and the presence of graphene are essential in enhancing performance in the proposed heterostructure, reducing recombination of charge carriers, and improving sunlight absorption. This work shows how optimal band alignment control and carbon addition can facilitate charge transfer, enabling the development of highly efficient PEC devices based on 0D/2D/2D heterostructure nanocomposites.

Heterostructured Bi2S3/MoS2 Nanoarrays for Efficient Electrocatalytic Nitrate Reduction to Ammonia Under Ambient Conditions.

Developing efficient electrocatalysts to realize the nitrate reduction reaction (eNO3-RR) for ammonia synthesis as an alternative to the traditional Haber-Bosch production process is of great significance. Herein, the heterostructured Bi2S3/MoS2 nanoarrays were successfully synthesized by Bi2S3 nanowires anchored on MoS2 nanosheets. Owing to the interfacial coupling effect, both particular surface area and exposure active sites increase. Density functional theory further uncovered that the excellent activity originates from charge transfer of the interface and a low potential barrier of 0.58 eV for hydrogenation of *NO to *NOH on Bi2S3/MoS2. Compared with pure Bi2S3 and MoS2 catalysts, the heterostructured Bi2S3/MoS2 nanoarrays exhibit a superior NH3 yield of 15.04 × 10-2 mmol·h-1·cm-2 and a Faraday efficiency of 88.4% at -0.8 V versus the reversible hydrogen electrode. This work provides a new avenue to explore advanced electrocatalysts, which is expected to shorten the distance from the practical application of the eNO3-RR technology.

Design of MOF-Derived NiO-Carbon Nanohybrids Photocathodes Sensitized with Quantum Dots for Solar Hydrogen Production.

Nickel oxide (NiO) is a promising p-type material for a wide range of optoelectronic devices, as well as photocathode for photoelectrochemical (PEC) water splitting. However, traditional NiO photoelectrodes exhibit a wide bandgap (3.6 eV), intrinsic poor electrical conductivity, and low surface area, leading to low PEC systems performance. Herein, the authors explore a Ni-based metal-organic framework (MOF) template method to obtain hierarchical hollow spheres of carbon/NiO nanostructure by successive carbonization and oxidation treatments. After sensitization with core and core-shell quantum dots (QDs), the optimized NiO-photocathode exhibits a maximum current density of -93.6 µA cm-2 at 0 V versus RHE (reversible hydrogen electrode) in neutral pH (6.8) and -285 µA cm-2 at -0.4 V versus RHE. Compared to pure NiO and single-core CdSe QDs, a 2.2-fold increase in photocurrent can be obtained. The improvement in the performance of this hybrid is not only due to the high surface area for loading QDs and light scattering, but also to the presence of a highly conductive carbon matrix that promotes fast charge transfer. The proposed MOFs-based NiO/carbon photocathode sensitized with QDs can be an effective strategy to improve the efficiency of metal oxide-based PEC systems for hydrogen generation.

Modulating the 0D/2D Interface of Hybrid Semiconductors for Enhanced Photoelectrochemical Performances.

Photoelectrochemical (PEC) solar-driven hydrogen production is a promising route to convert solar energy into chemical energy using semiconductors as active materials. However, the performance is still far from satisfactory due to a limited absorption range and rapid charge recombination. Compared to 3D semiconductors, 0D/2D nanohybrids may exhibit better PEC performance, due to the formation of an intimate interface between the two semiconductors that can inhibit carrier recombination. Herein, a photoelectrode based on a 0D/2D heterojunction is constructed by 0D metal chalcogenide quantum dots (QDs) and hierarchical 2D Zn-MoS2 nanosheets (NSs). The effect of PbS, CdS, and their composite PbS@CdS QDs is analyzed by depositing them onto Zn-MoS2 NSs using an in situ process. This distinctive heterojunction can leverage the light harvesting capabilities of QDs with the catalytic performance of Zn-MoS2 . Compared to Zn-MoS2 , Zn-MoS2 /PbS, and Zn-MoS2 /CdS, the obtained 0D/2D heterostructure based on the composite Zn-MoS2 /PbS@CdS has a significantly enhanced photocurrent. The synergistic effect between 0D/2D heterojunction, the extended absorption range of QDs, and the strong coupling and band alignment between them lead to superior solar-driven PEC performance. This work can provide a new platform to construct multifunctional 0D/2D nanohybrids for optoelectronic applications, not limited to PEC devices.

AuCu xO-Embedded Mesoporous CeO2 Nanocomposites as a Signal Probe for Electrochemical Sensitive Detection of Amyloid-Beta Protein.

A sandwich-type electrochemical immunosensor for detecting amyloid-beta protein was fabricated based on Au NP-functionalized reduced graphene oxide (Au@rGO) as an effective sensing platform and AuCu xO-embedded mesoporous CeO2 (AuCu xO@m-CeO2) nanocomposites as the catalytic matrix. The AuCu xO@m-CeO2 composites were obtained by adjusting the amount of m-CeO2 in the reaction to expose enormous active sites. Also, AuCu xO@m-CeO2 was applied as a matrix to immobilize antibodies by forming bridged bonds between m-CeO2 and carboxyl functional groups of antibodies without additional agents. Furthermore, AuCu xO with prominent catalytic activities dramatically improved the performance of the fabricated immunosensor. Also, the morphology, structure, and electronic state of the surface were characterized by SEM, XRD, TEM, and XPS. In addition, the immunosensor demonstrated a wide linear range of 100 fg mL-1 to 10 ng mL-1. This study may provide a way for sensitively detecting various biomarkers.

Facile Synthesis of Cu2O@TiO2-PtCu Nanocomposites as a Signal Amplification Strategy for the Insulin Detection.

Novel ultrasensitive sandwich-type electrochemical immunosensor was proposed for the quantitative detection of insulin, a representative biomarker for diabetes. To this end, molybdenum disulfide nanosheet-loaded gold nanoparticles (MoS2/Au NPs) were used as substrates to modify bare glassy carbon electrodes. MoS2/Au NPs not only present superior biocompatible and large specific surface area to enhance the loading capacity of primary antibody (Ab1) but also present good electrical conductivity to accelerate electron transfer rate. Moreover, the amino-functionalized cuprous oxide decorated with titanium dioxide octahedral composites (Cu2O@TiO2-NH2) were prepared to load dendritic platinum-copper nanoparticles (PtCu NPs) to realize signal amplification strategy. The resultant nanocomposites (cuprous oxide decorated with titanium dioxide octahedral loaded dendritic platinum-copper nanoparticles) demonstrate uniform octahedral morphology and size, which effectively increases the catalytically active sites and specific surface area to load the secondary antibody (Ab2), even increases conductivity. Most importantly, the resultant nanocomposites possess superior electrocatalytic activity for hydrogen peroxide (H2O2) reduction, which present the signal amplification strategy. Under the optimal conditions, the proposed immunosensor exhibited a linear relationship between logarithm of insulin antigen concentration and amperometric response within a broad range from 0.1 pg/mL to 100 ng/mL and a limit detection of 0.024 pg/mL. Meanwhile, the immunosensor was employed to detect insulin in human serum with satisfactory results. Furthermore, it also presents good reproducibility, selectivity, and stability, which exhibits broad application prospects in biometric analysis.

An amplification label of core-shell CdSe@CdS QD sensitized GO for a signal-on photoelectrochemical immunosensor for amyloid ß-protein.

In this work, the heterostructures of Au nanoparticles loaded on 3D flower-like α-Fe2O3 (Au NPs/α-Fe2O3) as a platform and core-shell CdSe@CdS quantum dots sensitized graphene oxide (GO/CdSe@CdS QDs) as a signal amplification label were established in an ultrasensitive sandwich-type photoelectrochemical (PEC) immunosensor based on the "signal-on" type amplification method for detection of amyloid ß-protein (Aß). Specifically, the ultrahigh sensitivity of the proposed immunosensor came from two main properties. First, Au NPs/α-Fe2O3 could partially absorb visible-light, which dramatically promotes electron transfer because of the excellent conductivity of Au NPs, and effectively inhibits the electron-hole recombination, thanks to the effect of heterostructures. Second, the signal-on type is based on the signal amplification label of GO/CdSe@CdS QDs which on adequate absorption of visible-light can improve generation of photogenerated electron-hole pairs effectively. Under optimal conditions, the well-prepared PEC immunosensor exhibited a low detection limit of 0.02 pg mL-1 and a wide linear range from 0.06 pg mL-1 to 350 ng mL-1 for Aß detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising pathway for detection of other important biomarkers.

Label-free electrochemical immunosensor for insulin detection by high-efficiency synergy strategy of Pd NPs@3D MoSx towards H2O2.

Here, a novel H2O2-based electrochemical immunosensor utilizing Pd nanoparticles functionalized three-dimensional wrinkly amorphous MoSx composites (Pd NPs@3D MoSx) as the platform was developed for the determination of insulin. In this work, Pd NPs@3D MoSx prepared in the presence of CTAB possessed an excellent catalytic activity for the reduction of H2O2. Furthermore, Pd NPs@3D MoSx with favorable biological compatibility can conjugate a great many antibodies to capture insulin. Attributed to the excellent property, electrochemical signals could be greatly amplified, contributing to improving detection sensitivity. Especially, SEM, TEM, and XPS information further confirmed nanomaterial's surface morphology and amorphous structure. Under the optimal conditions, the proposed immunosensor exhibited a sensitively linear relation with logarithmic insulin concentrations from 0.01 to 100 ng/mL with a low detection limit of 3.0 pg/mL (S/N = 3). Characterized by good reproducibility, specificity, and stability, the fabricated immunosensor may blaze a path for insulin detection in a real sample.

Label-free photoelectrochemical immunosensor for NT-proBNP detection based on La-CdS/3D ZnIn2S4/Au@ZnO sensitization structure.

A new, photoelectrochemical immunosensor was proposed on the basis of the La-CdS/3D ZnIn2S4/Au@ZnO sensitization structure for detection of aminoterminal pro-brain natriuretic peptides (NT-proBNP). The Au@ZnO-modified electrode was first assembled with 3D ZnIn2S4, 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 ZnIn2S4 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.

Facile synthesis of MoS2@Cu2O-Pt nanohybrid as enzyme-mimetic label for the detection of the Hepatitis B surface antigen.

An ultrasensitive sandwich-type electrochemical immunosensor was proposed for quantitative detection of hepatitis B surface antigen, which is a representative biomarker of the Hepatitis B virus. First, the porous graphene oxide/Au composites with good conductive ability were employed to accelerate the electron transfer on the electrode interface. Furthermore, the amino functionalized molybdenum disulfide @ cuprous oxide hybrid with coral morphology was prepared to combine platinum nanoparticles for achieving signal amplification strategy. The resulting nanocomposites (molybdenum disulfide @ cuprous oxide - platinum) demonstrated uniform coral morphology, which effectively improved the specific surface area available for loading the secondary antibody and the number of catalytically active sites, even also increased the electrical conductivity. Based on these advantages, this composite system yielded a superior electrocatalytic current response toward the reduction of hydrogen peroxide. In addition, porous graphene oxide/Au composites were used to modify the glassy carbon electrode, thereby presenting a large surface area and becoming biocompatible, for improving the loading capacity of the primary antibody. Under optimal conditions, we obtained a linear relationship between current signal and hepatitis B surface antigen concentration in the broad range from 0.5pg/mL to 200ng/mL, with a detection limit of 0.15pg/mL (signal-to-noise ratio of 3). These values are promising towards clinical applications.

Ultrasensitive electrochemical immunosensor for quantitative detection of SCCA using Co3O4@CeO2-Au@Pt nanocomposite as enzyme-mimetic labels.

Recently early diagnosis of squamous cell carcinoma antigen (SCCA) as a tumor maker of various cancers has increasingly attracted a lot of attention with heightening of incidence rate of cancer. The SCCA with low concentration in human serum should be diluted before detecting. Thus, an immunoassay with high sensitivity is significant for early detecting SCCA. Therefore, a nonenzymatic sandwich-type electrochemical immunosensor herein was conducted to quantitative detection of squamous cell carcinoma antigen (SCCA). The amino functionalized cobaltosic oxide @ ceric dioxide nanocubes with core-shell morphology were prepared to combine sea-urchin like gold @ platinum nanoparticles (Co3O4@CeO2-Au@Pt), and used as labels to conjugate with secondary antibodies for signal amplification. Due to the synergetic effect, excellent electrochemical property and superior auxiliary catalytic activity of Co3O4@CeO2-Au@Pt, high electrocatalytic current responses toward the reduction of hydrogen peroxide (H2O2) were achieved. Besides, the electrodeposited gold nanoparticles (D-Au NPs) which were modified on glassy carbon electrodes (GCE) were used as antibodies carriers and sensing platforms. With the well cooperation of Co3O4@CeO2-Au@Pt and D-Au NPs, a broad linear range from 100fg/mL to 80ng/mL with a low detection limit of 33 fg/mL for detecting SCCA was achieved. In addition, the immunosensor displayed with good reproducibility, high selectivity and stability. The results are satisfactory when the proposed method has been applied to analyze human serum samples, indicating that the potential application is promising in clinical monitoring of tumor markers.