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A chemical-chemical redox cycling amplification strategy was introduced into a photocathodic immunosensing system. To prove the applicability of the method, a novel self-powered photochemical system by integrating the photoanode and photocathode was designed for protein analysis.

A novel chemiluminescence (CL) immunosensor using functionalized tungsten disulfide nanosheets (WS2 NSs)–gold nanoparticles (Au NPs)–horseradish peroxidase (WS2–Au–HRP) as multiple signal amplification probe was developed for prostate specific antigen (PSA) analysis. The WS2–Au nanocomposites were synthesized by in situ growth of Au NPs on the surface of WS2 NSs. HRP and antibody for recognizing the target were subsequently functionalized on WS2–Au. Owing to the large loading capacity of the WS2 NSs, the WS2–Au–HRP nanoprobe exhibits synergistic enhancement to the luminol–H2O2 CL system. The kinetics and spectra of CL from the luminol–H2O2–WS2–Au–HRP system were studied and the CL mechanism is discussed. Exemplified by PSA as target, the ultrasensitive CL immunoassay of PSA was achieved owing to the multiple signal amplification of the WS2–Au–HRP nanoprobe. The detection limit is 3.0 × 10−14 g mL−1 with a linear range of 1.0 × 10−13 to 1.0 × 10−8 g mL−1. Furthermore, the method was applied to human serum sample analysis with high selectivity and reproducibility. The method provides a novel ultrasensitive CL detection tool for biomarkers in real samples.

Fluorescent adenine (A)-rich DNA-templated gold nanoclusters were demonstrated to be a novel probe for determination of biothiols (including cysteine, glutathione, and homocysteine). Fluorescence intensity of adenine-rich DNA-templated gold nanoclusters could be greatly quenched by Hg(II) ions through the formation of a gold nanoclusters-Hg(II) system. When biothiols (cysteine as the model) were introduced into the system, the fluorescence intensity recovered due to the formation of a more stable Hg(II)-thiol coordination complex using Hg-S metal-ligand bonds, which inhibited the Hg(II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters. Based on this fluorescence phenomenon, an on-off-on fluorescence strategy was designed for the sensitive determination of biothiols. The method allowed sensitive detection of cysteine with a linear detection range from 100 nM to 5 μM and a limit of detection of 30 nM. Additionally, the assay can be applied for detection of biothiol levels in human plasma samples. Therefore, it can provide a simple and rapid fluorescent platform for biothiol detection.

A potentiometric resolved photoelectrochemical (PEC) system based on CdS nanowires and SnNb2O6 nanosheets was developed. To prove the applicability of this system in PEC multi-biomarker analysis, a label free PEC immunosensor for two cardiac biomarkers, myoglobin and cardiac troponin I, was constructed.

A novel nitrogen and sulfur co-doped carbon dots (NS-CDs)-H2O2 chemiluminescence (CL) system was developed to detect carcinoembryonic antigen (CEA) by taking advantage of dual-signal amplification of functional Au@Ag nanoparticles (NPs) nanoprobes. Horseradish peroxidase (HRP) and the complementary DNA were co-immobilized onto Au@Ag NPs surface to shape the functional nanoprobes (HRP-Au@Ag-cDNA) for signal amplification. In this proposal, HRP-Au@Ag-cDNA was specifically hybridized with CEA aptamer-functionalized magnetic beads to form the double-strand hybridization nanocomposites (HRP-Au@Ag-dsDNA-MB). Upon the addition of CEA, the CEA aptamer preferred to bind with CEA instead of double-strand hybridization interaction, thus HRP-Au@Ag-dsDNA-MB was dehybridized and the HRP-Au@Ag-cDNA nanoprobe was released. The synergistic catalytic effects of HRP and Au @Ag NPs endow the nanoprobe producing a dual CL signal amplification in the NS-CDs-H2O2 CL system. The CL intensity of the developed strategy enhanced with CEA concentration increasing in the range of 0.3–80 ng mL−1. Benefiting from the synergistic effect, a detection limit as low as 94 pg mL−1 was obtained. Moreover, successful application of this CL sensing platform was achieved for the determination of CEA in human serum samples, demonstrating the promising prospect in the early tumor warning and therapeutic monitoring.

A rapid and label-free fluorescence sensing strategy has been established for the sensitive determination of melamine (MA) on the basis of poly(adenine) (poly (A))-templated Au nanoclusters (AuNCs). The poly(A)-templated AuNCs possessed excellent luminescence and photo-stability. In the presence of Hg2+, the luminescence of AuNCs was quenched by Hg2+ through the metallophilic interactions between Au+ and Hg2+. When melamine was introduced, the fluorescence intensity of sensing system could be recovered. There was a greater coordination interaction between Hg2+ and melamine, which blocked the Hg2+-mediated fluorescence quenching of AuNCs. The assay allowed sensitive determination of melamine with a linear detection range from 50 nM to 100 μM. The limit of detection was as low as 16.6 nM. Furthermore, the label-free strategy was successfully employed for the detection of melamine concentration in real samples.

The fluorescence intensity of poly(adenine) DNA-templated gold nanoclusters was shown to be significantly quenched by N-acetylcysteine through the formation of the Au-S metal-ligand bonds. On the b...

The energy transfer efficiency, strongly depending on the distance of donor–acceptor pair, is always a crucial factor for the construction of elegant electrochemiluminescence resonance energy transfer (ECL-RET)-based biosensors. In this paper, a novel and efficient ECL-RET in 2D/2D heterostructured g-C3N4/MnO2 was developed using g-C3N4 nanosheets (g-C3N4 NSs) as energy donor and MnO2 nanosheets (MnO2 NSs) as energy acceptor. In this system, MnO2 NSs in-situ grew on g-C3N4 NSs to form the 2D/2D heterostructure, greatly shortening the distance of the donor–acceptor pair (g-C3N4–MnO2) and thus greatly enhancing the RET efficiency. To demonstrate the performance of the system, a signal “off-on” ECL sensor was designed for glutathione (GSH) analysis. In the absence of GSH, MnO2 significantly quenched the ECL intensity of g-C3N4 owing to ECL-RET in this 2D/2D g-C3N4/MnO2 heterostructure (ECL signal “off”). Upon the addition of GSH, MnO2 was reduced to Mn2+ by GSH and g-C3N4 was released from the heterostructured g-C3N4/MnO2, generating a recovery of ECL intensity (ECL signal “on”). Under the optimal conditions, the designed ECL-RET signal “off-on” sensor realized the sensitive detection of GSH ranged from 0.2–100 μM with the detection limit of 0.05 μM. Furthermore, the as-prepared ECL-RET sensor exhibits good performance in the determination of GSH in human serum samples. The ECL-RET in 2D/2D heterostructure provides an ingenious way for the exploitation of novel ECL biosensing systems.

A series of Cu2O crystals with well–controlled cubic (C–Cu2O), star–shaped (S–Cu2O), and octahedral (O–Cu2O) structures were prepared by facile wet chemical method to explore the morphology–dependent electrocatalytic efficiency. When tested for the sensing of 4−aminophenol (4–AP), 4−chlorophenol (4–CP), and 4−nitrophenol (4–NP), it was found that the O–Cu2O exhibited the best current signals, which were mainly because of its more exposed {111} facets and higher surface area. Further, O–Cu2O crystals were homogeneously dispersed on graphene oxide (GO) surface to achieve a hierarchical reinforcement structure. The electrode modified by O–Cu2O@GO showed high electrocatalytic activity toward the oxidation of 4–AP, 4–CP, and 4–NP, and could realize the selective detection of phenolic compounds in ternary electrolyte solutions and industrial wastewater. This work is beneficial to morphology tailoring and provides novel way to improve the electrochemical property of oxide–based catalysts as the promising applications in electrochemical sensors.

Water splitting into hydrogen (H2) to produce clean energy is of great significance for sustainable development. Transition metal phosphides (e.g., Ni12P5 nanoparticles) may be used as non-precious earth-abundant electrocatalysts for the H2 evolution reaction, but their poor electronic conductivity and small surface area hinder efficient catalytic H2 production. In this research, we demonstrate for the first time the facile synthesis of porous carbon/Ni12P5 (C/NiP-C) composites with the dispersion of Ni12P5 nanoparticles onto a conductive porous carbon support in an ionic surfactant hexadecyl trimethyl ammonium bromide (CTAB)-mediated ethanol solution. The CTAB plays dual roles in the synthesis including (1) the introduction of carbon to increase the conductivity of the synthetic materials and (2) the formation of uniform Ni12P5 phosphides through the interaction between the H2PO2− anion, Ni2+, and C19H42N+ cation dissociated from CTAB. The obtained C/NiP-C composites may function as electrocatalysts for the hydrogen evolution reaction (HER) with excellent HER performance (η: 63 mV, η10: 176 mV, Tafel slope: 100 mV dec−1, wherein η represents the onset overpotential and η10 represents the overpotential required for a current density (j) value of −10 mA cm−2) compared with the NixPy composites synthesized in pure ethanol (η: 160 mV, η10: 392 mV, Tafel slope: 154 mV dec−1), the C/NiP-P composites synthesized in a P123-mediated ethanol solution (η: 75 mV, η10: 286 mV, Tafel slope: 210 mV dec−1), and the C/NiP-F composites synthesized in a F127-mediated ethanol solution (η: 80 mV, η10: 302 mV, Tafel slope: 189 mV dec−1). The enhanced HER performance can be attributed to the synergistic effects resulting from the unique structure of the porous C support and the well dispersed Ni12P5 nanoparticles.

The work is mainly to study the thermal stability including the phase stability, microstructure and tribo-mechanical properties of the AlB2-type WB2 and W–B–N (5.6 at.% N) films annealed in vacuum at various temperatures, which are deposited on Si and GY8 substrates by magnetron sputtering. For the WB2 and W–B–N films deposited on Si wafers, as the annealing temperature increases from 700 to 1000 °C, a-WB (700 °C) and Mo2B5-type WB2 (1000 °C) are successively observed in the AlB2-type WB2 films, which show many cracks at the temperature ≥ 800 °C resulting in the performance failure; by contrast, only slight α-WB is observed at 1000 °C in the W–B–N films due to the stabilization effect of a-BN phase, and the hardness increases to 34.1 GPa first due to the improved crystallinity and then decreases to 31.5 GPa ascribed to the formation of α-WB. For the WB2 and the W–B–N films deposited on WC–Co substrates, both the WB2 and W–B–N films react with the YG8 (WC–Co) substrates leading to the formation of CoWB, CoW2B2 and CoW3B3 with the annealing temperature increasing to 900 °C; a large number of linear cracks occur on the surface of these two films annealed at ≥ 800 °C leading to the film failure; after vacuum annealing at 700 °C, the friction performance of the W–B–N films is higher than that of the deposited W–B–N films, while the wear resistance of the WB2 films shows a slight decrease compared with that of the deposited WB2 films.

A novel fluorescence (FL) immunosensor for prostate-specific antigen (PSA) detection was developed based on the Forster resonance energy transfer (FRET) between nitrogen and sulfur co-doped carbon dot functionalized silica nanospheres (Si/NS-CDs) and Au@Ag NPs. The strategy utilized the PSA primary antibody labeled luminescent Si/NS-CDs as donors and PSA secondary antibody labeled Au@Ag NPs as acceptors. In the presence of PSA, the bio-affinity of the antigen and antibody caused the Si/NS-CDs and Au@Ag NPs to approach at a close enough distance for the FL intensity of the Si/NS-CDs to decline owing to the FRET effect. By virtue of the excellent optical properties of the Si/NS-CDs nanoprobe, the quantitative analysis of PSA has been successfully realized using both FL spectroscopy and a naked-eye readout. The fluorometric results present the desirable analytical performance for PSA detection in the range from 5.0 pg mL−1 to 10 ng mL−1 with a detection limit of 0.95 pg mL−1 (S/N = 3). Moreover, satisfactory results for the determination of the PSA target in samples of human serum were obtained, showing the great promise of the method for application in biochemical analysis.

The oxygen evolution reaction (OER) is a key process in water splitting, rechargeable metal–air batteries and fuel cells, and the design of highly efficient, stable and non-noble metal-based electrocatalysts for the OER remains a great challenge so far. Here, we report the rational design and synthesis of hierarchical ultrathin nanosheet-based CoOOH hollow nanospheres with rich oxygen vacancies using a room-temperature self-template strategy with organic–inorganic hybrid Pi-Co-glycerate hollow nanospheres as the templates. The anions (H2PO2−) in the templates enable the proceeding of anion-exchange reaction at room temperature, and the resultant unique structural features (i.e., ultrathin thickness, rich oxygen vacancies and central void space) endow the CoOOH hollow nanospheres with excellent performance in the electrocatalytic OER. The obtained CoOOH hollow nanospheres exhibit a Tafel slope of 49 mV dec−1 and a low overpotential of 275 mV at the current density of 10 mA cm−2, superior to the γ-CoOOH nanosheets with an overpotential of 304 mV and the bare Ni foam with an overpotential of 362 mV at the same current density. Importantly, these CoOOH hollow nanospheres possess the lowest overpotential of 340 mV at the current density of 200 mA cm−2 among the reported Co-based nanomaterials (370–770 mV). This research proposes a new chemical conversion mechanism and provides a new approach for the fabrication of hollow nanomaterials at room temperature, facilitating the development of efficient OER catalysts.

A spatial-resolved electrochemiluminescence (ECL) aptasensing platform for sensitive protein detection was constructed in a double-check mode. CdS-C composites as cathodic ECL emitters and luminol-gold nanoparticles (L-Au NPs) as anodic ECL emitters were immobilized on working electrode 1 (WE1) and working electrode 2 (WE2) of the dual-disk glassy carbon electrodes (DDCE), respectively. The platform was designed by integrating silver-polyamidoamine NCs-labeled biotin-aptamer (Ag-PAMAM-bio-Apt) with the ECL emitters on the DDCE. The in-situ consumption of co-reactants in the ECL system by Ag-PAMAM NCs resulted in the great ECL quenching on both WE1 and WE2. The resonance energy transfer between L-Au NPs and Ag-PAMAM NCs made the ECL on WE2 further decrease. In the presence of carcinoembryonic antigen (CEA), portions of Ag-PAMAM-bio-Apt detached from the DDCE because of the competitive reaction of CEA and cDNA toward to Ag-PAMAM-bio-Apt, generating an enhancement of ECL intensity. This strategy achieves the detection of CEA in a double-check mode with detection limits of 0.39 pg mL−1 for the cathodic assay (WE1) and 0.20 pg mL−1 for the anodic assay (WE2), respectively. Furthermore, the proposed method had been successfully applied to determine CEA in human serum sample with recoveries of 80.0–110.0%, showing great potential in cancer diagnosis.

Here, we report a three-dimensional (3D) network molecularly imprinted polymer (MIP) on electrode surface to achieve an efficient and specific detection of theophylline in foodstuffs, using theophylline as the template molecule, mesoporous silica nanospheres (MSNs) as the signal transducer to shuttle electrons, and both phenyltriethoxysilane and pyrrole as functional monomers. The electron microscope images reveal the presence of well-distributed hierarchically MSNs with a pomegranate-like morphology, topped with MIP uniform layer. Electrochemical characterizations were carried out to monitor the properties of the resulting sensing platform based on the MIP/gate effect employing hexacyanoferrate molecules as the electrochemical probe. The data show that due to the high conductivity and electron transfer ability of the prepared theophylline-imprinted membrane, this method exhibits excellent sensitivity and binding affinity with a linear dynamic concentration range in excess of six orders of magnitude and low detection limit (0.66 nM), meeting the requirements of theophylline trace analysis.

Photoelectrochemical (PEC) immunoassay is a burgeoning and promising bioanalytical method. However, the practical application of PEC still exist some challenges such as the inevitable damage of biomolecules caused by the PEC system and the unsatisfactory sensitivity for biomarkers with low abundance in real sample. To solve the problems, we integrated the cosensitized structure of Ag2S/ZnO nanocomposities as photoelectrode with photogenerated hole-induced chemical redox cycling amplification (CRCA) strategy to develop a split-type PEC immunosensor for cardiac troponin I (cTnI) with high sensitivity. Initially, the immunoreaction was carried out on the 96-well plates in which alkaline phosphatase (ALP) could catalyze ascorbic acid 2-phosphate (AAP) to generate the signal-reporting species ascorbic acid (AA). Subsequently, the AA participated and the tris (2-carboxyethyl) phosphine (TCEP) mediated chemical redox cycling reaction took place on the photoelectrode, thus leading to signal amplification. Under the optimized conditions, the immunosensor demonstrated a detection limit (LOD) of 3.0 × 10−15 g mL−1 with a detection range of 1.0 × 10−14 g mL−1 to 1.0 × 10−9 g mL−1 for cTnI. Impressively, the proposed method could determine the cTnI in human serum samples with high sensitivity and satisfactory accuracy. Considering the virtues of the photoelectrode and the chemical redox cycling strategy, the method would hold great potential for highly sensitive biosensing and bioanalysis.

Photoelectrochemical (PEC) biosensing has received increasing attention due to its great potential in the analysis of biomarkers. The performance of a PEC biosensor depends largely on photosensitive materials. The photoactive materials with excellent properties are of great importance to realize advanced PEC bioassays. Recently, as a special class of nanocomposites, heterostructures consisting of different types of semiconductors with potential applications in PEC systems have witnessed the rapid development to improve the performance of PEC biosensors. In this review, the research progress on the promising heterostructures has been introduced and summarized, and the applications of such heterostructures in PEC bioassays are provided. The future development of heterostructures pertaining to PEC biosensing systems has also been briefly discussed.

A general and practical chemiluminescence (CL) biosensing platform for detection of tumor marker prostate-specific antigen (PSA) as a model analyte was developed for the first time based on the excellent catalytic performance of bimetallic Au-Ag core-shell nanoparticales (Au@Ag NPs) on luminol-K3Fe(CN)6 CL system. The Au@Ag NPs were synthesized by a simple and green aqueous phase successive reduction method. The prepared Au@Ag NPs with remarkable synergistic catalytic activity effect could significantly catalyze luminol-K3Fe(CN)6 CL reaction to produce a great CL enhancement. Based on this synergistic catalytic activity, a luminol-K3Fe(CN)6-Au@Ag NPs CL system combined with immunoassay was designed for the sensitive detection of PSA. In this protocol, the Au@Ag NPs were modified with anti-PSA-antibody (Ab-Au@Ag NPs) to specifically capture target molecules PSA. In the presence of PSA, a non-competitive immunoreaction occurred between Ab-Au@Ag NPs and PSA to form an immnunonanoshperes (PSA-Ab-Au@Ag NPs). The results show that the CL catalytic ability of the immnunonanospheres decreased with the PSA concentration increasing. And the quenching degree of CL signals is proportional to the logarithm of PSA concentration in the range of 0.1 pg mL−1–100.0 ng mL−1. Thanks to the fine performance of the Au@Ag NPs, the detection limit of the method is down to 0.047 pg mL−1 (S/N = 3). Moreover, the applicability of the present method was successfully applied for PSA determination in human serum samples with recoveries of 86.1–112.5%, demonstrating great promise for application in biochemical analysis.

It is valuable to develop a sensing platform for not only detecting a tumor marker in body fluids but also measuring its expression at single cells. In the present study, a simple closed bipolar electrodes-based electrochemiluminescence (BPEs-ECL) imaging strategy was developed for visual immunoassay of prostate specific antigen (PSA) at single cells using functional nanoprobes of heterogeneous Ru(bpy)32+@SiO2/Au nanoparticles. Multiple-assisted ECL signal amplification strategy was introduced into the detection system on the basis of the synergetic amplifying effect of the anodic and cathodic amplification. On the basis of the synergetic amplifying effect, the detection limits of PSA by using photomultiplier tube and charge-coupled device (CCD) imaging are 3.0 and 31 pg/mL, respectively. The obtained immunosensor was employed to evaluate PSA levels in serum samples with a satisfying result. Moreover, the obtained functional nanoprobes were used to visually profile the PSA expression on the surface of sin...

In this study, a facile solution approach was developed for the synthesis of a series of core-shell structured Ag@Cu2O nanocrystals of various shapes including triangles, spheres, and cubes with well-defined stable heterojunctions. The electrooxidation of dopamine (DA), uric acid (UA), guanine (G), and adenine (A) using these hybrids revealed morphology-dependent sensing properties, with activities and accumulation ability following the order, triangular Ag@Cu2O > spherical Ag@Cu2O > cubic Ag@Cu2O. Further, we constructed a novel graphene oxide (GO) nanosheet-reinforced triangular Ag@Cu2O ternary hetero-nanostructure. Such a hybrid with a three-dimensional interconnected hierarchical architecture is suitable for catalysis, since it not only leads to improved interfacial electron transfer, but also readily exposes the highly catalytic Ag@Cu2O to the reactants. Therefore, more enhanced electrochemical activities were observed for the oxidation of DA, UA, G, and A. This study provides an efficient way to synthesize morphology-controlled Ag@Cu2O heterogeneous catalysts for the fabrication of potential biosensors, and also opens up attractive avenues in the design of multifunctional ternary noble metal-semiconductor-carbon hybrids.

This work reports the elegant bridging of enzymatic generation of electron donor with photogenerated hole-induced chemical redox cycling amplification (RCA) for innovative photoelectrochemical (PEC) immunoassay, by the aid of a heterojunction photoelectrode with split-type strategy. Specifically, the system was exemplified by the alkaline phosphatase (ALP) catalytic generation of ascorbic acid (AA), the redox cycling of AA by tris (2-carboxyethyl) phosphine (TCEP) as reductant, and the use of a novel Bi2S3/Bi2Sn2O7 heterojunction and myoglobin (Myo) as the photoelectrode and the target, respectively. After the immunoreaction and ALP-induced production of AA, the subsequent oxidation of AA by the photogenerated holes of the Bi2S3/Bi2Sn2O7 heterojunction could be cycled via the regeneration of AA by TCEP from the oxidized product of dehydroascorbic acid, leading to easy signal amplification for the sensitive immunoassay of Myo in real samples. It is believed that this work provided a basis for further desig...

In this work, a rapid and label-free fluorescent sensing method has been established for tetracycline (TC) detection by using poly(adenine) (poly A) DNA-templated Au nanoclusters (AuNCs) as fluorescence indicator. The obtained AuNCs exhibited excellent fluorescence intensity and good stability. In the presence of tetracycline, the fluorescence intensity of AuNCs was obviously reduced due to the interactions between the tetracycline and the poly A DNA-templated AuNCs. Under the optimum conditions, the strategy permitted sensitive detection of tetracycline in a linear range from 0.1 to 60 μM and with a limit of detection of 20 nM. In addition, the sensor was successfully applied to determinate the tetracycline content in milk samples. More importantly, it could be easily performed within 10 min at room temperature. Thus, it could provide a rapid, convenient, label-free, and high-sensitive fluorescent platform for tetracycline detection.

Dopamine has been shown interact strongly with Cu2+ to form a stable complex and inhibit the formation of polythymine-templated copper nanoclusters. Based on these findings, a label-free sensing strategy has been designed for the detection of dopamine using polythymine-templated copper nanoclusters as fluorescence probes. The fluorescent method exhibits sensitive and selective detection of dopamine with a linear range from 1 nM to 50 µM and a detection limit of 0.5 nM. In addition, the method was successfully applied for the determination of dopamine in dopamine hydrochloride injection samples. Thus, this approach holds considerable potential for the construction of a simple, rapid, and sensitive fluorescent assay for the determination of dopamine.

Owing to the difficulty to find a matched donor/acceptor pair, the development of an accurate and sensitive electrochemiluminescence (ECL) ratiometric sensing strategy based on resonance energy transfer (RET) strategy is still challenging. Herein, RET strategy triggered by the donor/acceptor pair (CdS-C nano-flowers (NFs)/luminol-Au nanoparticles (NPs)) was introduced into the ECL system for the construction of an ECL ratiometric self-calibrated aptasensor. In virtue of the natural absorption cross section and catalytic effect of the Au NPs, the signal quenching of CdS-C NFs and the signal enhancement of luminol could be induced in one potential scan. With this novel ECL-RET strategy, the ratiometric ECL aptasensor self-calibrated by the ratio of anodic ECL signal from luminol-Au NPs to the cathodic ECL signal from CdS-C NFs exhibits excellent analytical performance for carcinoembryonic antigen (CEA) with a range of 0.1 pg/mL–10 ng/mL and a detection limit of 0.033 pg/mL. In addition, the obtained ratiometric sensing platform was employed to quantify the CEA content in human serum samples with a satisfied result. The present ECL ratiometric approach provides a promising platform for detecting tumor markers, showing great potential in cancer diagnosis.

The identification of tumor markers is of great importance for clinical diagnosis but accurate detection with high sensitivity is still a great challenge. In present work, a spatial-resolved dual-signal-output electrochemiluminescent (ECL) ratiometric assay platform was constructed for sensitive detection of prostate specific antigen (PSA) on a dual-disk glassy carbon electrode. To fabricate the platform, flower-like CdS three-dimensional (3D) assemblies and Ru(bpy)32+-conjugated silica nanoparticles (Ru(bpy)32+@RuSi NPs), were immobilized onto the two disks as cathodic and anodic ECL emitters, respectively. After the stepwise modification of the gold nanoparticles, antibody for PSA, and bovine serum albumin onto the two disks respectively, the Ru(bpy)32+@RuSi NPs-based disk were incubated with varied concentration of PSA as working electrode, whereas the flower-like CdS 3D assemblies-based disk with fixed concentration of PSA were taken as internal reference electrode. The label free assay of PSA was realized by the ratio of anodic ECL signal from working electrode to the cathodic ECL signal from the internal reference electrode (ECLanode/ECLcathode). On the basis of the spatial-resolved dual-signal-output ratiometric ECL sensor, the PSA can be detected accurately with a linear range of 0.001 - 50ng/mL at a concentration as low as 0.34pg/mL. Furthermore, the proposed method was applied for PSA determination in human serum samples with satisfying results. Thanks to the same modified process of the two disks, this universal design well avoids environmental errors including the interference caused in the biological recognition process, which effectively reduces the false positive or negative errors, exhibiting a greatly improved accuracy, reliability and sensitivity.

The detection of biomarkers with high sensitivity and accuracy in real biosamples remains challenging. Herein, a universal spatial-resolved photoelectrochemical (PEC) ratiometry for biodetection of prostate-specific antigen (PSA) as model biomarker was designed for the first time based on a dual-electrode array modified by CdS@g-C3N4 heterojunction coupled with CuS quantum dots (QDs) as signal amplification tags. Specifically, a new kind of photoactive material, the CdS@g-C3N4 p–n heterojunction with high photoelectric conversion efficiency and good chemical stability, was synthesized and immobilized on two spatial-resolved electrodes (WE1 and WE2). After immobilizing gold nanoparticles and capturing PSA antibodies on the electrodes, WE1 incubated with various concentrations of PSA was taken as a working electrode, whereas WE2 with a fixed concentration of PSA was used as an internal reference electrode. Next, signal antibodies of PSA-labeled CuS QDs as PEC signal quenchers were immobilized on the electro...

A novel and competitive electrochemiluminescence (ECL) aptasensor for prostate specific antigen (PSA) assay was constructed using gold nanorods functionalized graphene oxide (GO@AuNRs) multilabeled with glucose oxidase (GOD) and streptavidin (SA) toward luminol-based ECL system. A strong initial ECL signal was achieved by electrodeposited gold (DpAu) on the electrode because of gold nanoparticles (AuNPs) motivating the luminol ECL signal. The signal probes prepared by loading GOD and SA-biotin-DNA on GO@AuNRs were used for achieving multiple signal amplification. In the absence of PSA, the signal probes can be attached on the electrode by hybridization reaction between PSA aptamer and biotin-DNA. In this state, the GOD loaded on the probe could catalyze glucose to in situ produce H2O2 and then AuNRs catalyze H2O2 to generate abundant reactive oxygen species (ROSs) in luminol ECL reaction. Both the high-content GOD and AuNRs in the signal probe amplified the ECL signal in the ECL system. Moreover, the combination of SA with biotin-DNA further expands ECL intensity. The integration of such amplifying effects in this protocol endows the aptasensor with high sensitivity and good selectivity for PSA detection. This aptasensor exhibits a linear relation in the range of 0.5pgmL-1 to 5.0ngmL-1 with the detection limit of 0.17pgmL-1 (S/N = 3). Besides, the strategy was successfully applied in determination of human serum samples with recovery of 81.4-116.0%.

An ascorbic acid oxidase (AAO)-ascorbic acid bioevent-based electron donor consumption mode was introduced into the PEC bioassay for the first time. Ternary hybrid bismuth sulfide/silver sulfide/TiO2 nanotube arrays as the photoelectrode coupled with AAO attached to SiO2 as a dual signal quenching strategy were employed for sensitivity enhancement.

A novel and simple photoelectrochemical (PEC) biosensing method for microRNA-21 (miRNA-21) detection is reported based on energy transfer (ET) between CdS:Mn doped structure (CdS:Mn) and Au nanoparticles (AuNPs). In this protocol, TiO 2 -CdS:Mn hybrid structure was used as a sensing platform for hairpin DNA immobilization. In the absence of miRNA-21, the immobilized DNA was in the hairpin form. In this state, the photocurrent of the electrode was greatly depressed, due to the effective ET effect produced by short interparticle distance between CdS:Mn and AuNPs. In the presence of miRNA-21, the hairpin DNA hybridized with miRNA-21 and changed into a more rigid, rodlike double helix, which forced the AuNPs away from the electrode surface, leading to obvious recover of photocurrent because of the vanished damping effect. Integrating the fine PEC performance of TiO 2 -CdS:Mn hybrid structure with the significant ET effect between CdS:Mn and AuNPs, the sensitive detection of miRNA-21 was realized in a linear range of 1.0 fM to 10.0 pM with a low detection limit of 0.5 fM. This method might be aussichtsreich for the detection of miRNAs and other biomarkers.

The cathodic electrochemiluminescence (ECL) behaviour of nontoxic MoS2 quantum dots (QDs) was studied for the first time using potassium peroxydisulfate as the co-reactant. Ag-PAMAM NCs, serving as difunctional tags for quenching and enhancing ECL of MoS2-reduced graphene oxide composites, were introduced into the ECL detection system for signal amplification. By modulating the interparticle distance between MoS2 QDs and Ag-PAMAM NCs, the ECL quenching from resonance energy transfer and the ECL enhancement from surface plasma resonance were realized. Coupling the good ECL performance of MoS2 QDs with the excellent ECL quenching and enhancement effects of Ag-PAMAM NCs, a novel MoS2 QDs-based ECL biosensing platform for sensitive detection of microRNA-21 was achieved with a detection limit of 0.20 fmol L-1 (S/N = 3). This method was successfully applied to the determination of microRNA-21 in human serum samples with recoveries of 90.0-110.0%, suggesting great potential for its applications in biological and chemical analysis.

A label-free photoelectrochemical aptasensor for the sensitive and selective determination of carcinoembryonic antigen was constructed based on a CdS quantum dot sensitized TiO2 nanotube electrode....

A general spatial-resolved photoelectrochemical (PEC) sensing platform for sensitive and high-throughput protein analysis was developed by integrating CdS@g-C3N4 heterojunction modified rotatable electrodes array with signal antibodies labeled Cu2O (Cu2O-Ab2) conjugates. The disk substrate containing eight spatial-resolved working electrodes array was fabricated using acid etching treatment method. After stepwise immobilizing CdS@g-C3N4, capture antibodies (Ab1), varied concentrations of target protein (prostate-specific antigen) and Cu2O-Ab2 conjugates on the corresponding sensing sites, the immunosensor array was prepared completely. Combining the high photoelectric conversion efficiency of the photoactive material with the effective signal probe, the immunosensor exhibits high sensitivity. The proposed spatial-resolved immunosensing platform shows a working range of 1.0 × 10-11 – 5.0 × 10-8 g mL−1 with a detection limit of 5.0 pg mL−1. The method provides a universal paradigm for near-simultaneously detection of multi-batch samples with good specificity and high sensitivity.

Novel exciton–plasmon interactions (EPI) between CdS@g-C3N4 heterojunction and Au@Ag nanoparticles (NPs) was introduced for the first time into the photoelectrochemical (PEC) biosensing system for highly sensitive microRNA-21 detection using duplex-specific nuclease-assisted cycle amplification for sensitivity enhancement. The photoelectrode of CdS@g-C3N4 nanowires could generate a great photocurrent because of the formation of the p–n heterojunction. Due to the natural absorption overlap, the exciton of CdS@g-C3N4 and the plasmon of Au@Ag NPs could be induced simultaneously to form EPI. Specifically, the perfect overlap of the wide absorption spectrum of Au@Ag NPs with the photoluminescence spectrum of CdS@g-C3N4 allows the resonance energy transfer and EPI between CdS@g-C3N4 nanowire and Au@Ag NPs simultaneously. The effective EPI renders the signal change modulated by the interparticle distance significantly. Such a signaling mechanism was then used to construct the PEC biosensor for microRNA-21 detect...

In this study, the effects of graphene oxide (GO) agglomerates on the workability, hydration, microstructure, and compressive strength of cement paste were addressed. The workability of cement paste was reduced because of the presence of GO agglomerates, which entrap a large amount of water. The mini-slump diameter was reduced by 21% with the incorporation of 0.03% by weight GO in cement paste. Hydration of the cement paste was accelerated due to nucleation sites provided by GO agglomerates serving as seeding material in the cement paste. The incorporation of GO refined the pore structure of the cement paste. The incorporation of GO was found to have much greater impact on macropores than on large and small mesopores. At 28 days, the incorporation of 0.04% by weight GO produced a 14% improvement in the compressive strength of cement paste. Below 0.03%, the incorporation of GO had no positive effects on compressive strength.

Herein, a novel photoelectrochemical (PEC) immunosensing platform for highly sensitive detection of prostate specific antigen (PSA) was constructed based on dual-quenching of photocurrent from CdSe sensitized TiO2 electrode by gold nanoparticles decorated dopamine-melanin nanospheres (AuNPs-Dpa-melanin CNSs). In this proposal, CdSe sensitized TiO2 was used as photoelectrochemical matrix and the functional AuNPs-Dpa-melanin CNSs were used as signal quenching element. The dual quenching of the gold nanoparticles decorated Dpa-melanin CNSs to the CdSe sensitized TiO2 was achieved as follows: (i) the strong energy transfer between the CdSe quantum dots (QDs) and Au NPs diminishes the photocurrent signal of CdSe QDs; (ii) the steric hindrance of AuNPs-Dpa-melanin CNSs partly obstructs the diffusion of the electron donor, i.e. ascorbic acid, to the surface of photoelectrode, which make the depleting efficiency of the photogenerated holes decrease, leading to a declined photocurrent intensity. On the basis of the dual quenching effect of AuNPs-Dpa-melanin CNSs, a competitive immunosensing platform for PSA was designed upon the specific binding of anti-PSA to PSA and PSA functionalized AuNPs-Dpa-melanin CNSs conjugates. This proposed immunosensor possesses wide linear range from 1.0×10-11gmL-1 to 1.0×10-7gmL-1 with the detection limit of 2.7pgmL-1. Moreover, the applicability of the present method was demonstrated in the determination of PSA in human serum. The strategy creates new paradigms for PSA and other tumor markers detection and demonstrates high sensitivity, good specificity, and satisfied applicability in complex biological samples.

A signal-switchable electrochemiluminescence (ECL) aptasensor was presented for sensitive prostate specific antigen (PSA) assay using ferrocene-graphene sheets (Fc-GNs) for high-efficiency quenching of ECL from Au nanoparticles functionalized cadmium sulfide flower-like three dimensional (3D) assemblies (Au-CdS flower-like 3D assemblies). Au-CdS flower-like 3D assemblies were synthesized and employed as luminophore, exhibiting strong and stable ECL intensity, and followed by assembling captured DNA (cDNA) and hybridizing it with half of base sequence of PSA aptamer on the Au-CdS flower-like 3D assemblies modified electrode. The remaining part of the non-complementary base of the aptamer could preferentially adsorb GN with the signal switched “off” state. While in the presence of the PSA, the binding of PSA with aptamer caused desorption of aptamer from the surface of Fc-GNs and was then released from electrode surface, thus allowing the ECL signal enhancement. With the transformation of luminescence signal from “off” to “on”, the aptasensor displays high sensitivity for PSA detection with a linear range from 1 pg mL −1 to 25 ng mL −1 and a detection limit of 0.38 pg mL −1 S/N =3). Moreover, this developed method could be successfully applied to the determination of PSA in human serum samples with recoveries of 85.8–104.0%, suggesting great potential applications in biochemical analysis.

The effects of graphene oxide (GO) on the early-age hydration process and mechanical properties of Portland cement paste were experimentally investigated in this study. Based on an isothermal calorimeter measurement, the hydration rate of cement was observed to increase with the increase of GO content by nucleation effect. On the other hand, the electrical resistivity development of GO-cement paste was monitored using a non-contact electrical resistivity device. The result showed that electrical the resistivity of GO-cement paste was evidently higher than that of plain cement paste. However, cement paste with excessive amounts of GO exhibited a decreased electrical resistivity due to the massive ion diffusion caused by GO. Compared to plain cement paste, the GO-cement paste exhibited obviously higher compressive and flexural strengths, but the enhancements in compressive strength began to decline when the GO amount was greater than 0.04%. The microstructure characterization indicated that GO can apparently densify the cement pastes with less porosity and hydrates networking, which is consistent with the results of hydration acceleration and strength enhancement.

A new and simple sandwich-like electrochemiluminescence (ECL) aptasensor for carcinoembryonic antigen (CEA) assay was fabricated based on the dual quenching effect from hemin-graphene (H-rGO) nanosheet and enzymatic biocatalytic precipitation (BCP) on the Au-CdS nanocomposites-based ECL system. In this aptasensor platform, flower-like spherical Au-CdS nanocomposites were used as ECL luminophores and exhibit a strong ECL signal. The rGO nanosheet was used as a supporter to immobilize hemin molecules via π-π stacking interactions. Due to the steric hindrance and quenching effect of rGO, the ECL intensity decreased by the construction of the sandwich “CEA aptamer I (NH2-DNA)-CEA-aptamer II” (H-rGO-aptamer II) mode. In the process of BCP, the ECL intensity further decreased because the hemin with intrinsic peroxidase-like catalytic activity could oxidize the 4-chloro-1-naphthol (4-CN) to produce an insoluble precipitation on the sensor. Using this dual quenching strategy, the prepared aptasensor exhibits a linear range from 0.8 pg/mL to 4 ng/mL and a detection limit of 0.28 pg/mL. This ECL aptasensor has simple design and undemanding in operation and was utilized to determine the content of CEA in complex samples with recoveries of 95.0% to 115.8%. Moreover, no any chemical modification of aptamer was required, suggesting that the proposed ECL aptasensor could be applied for the detection of diverse proteins just by altering the aptamer sequence.

In this study, a simple and label-free colorimetric sensing strategy was reported for rapid and selective detection of dopamine by inhibiting the Cu2+-catalyzed oxidation of a 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system. Similar to natural peroxidase, Cu2+ could catalyze the oxidation of the peroxidase substrate TMB to oxidized TMB (ox TMB) in the presence of H2O2, producing a blue color. However, dopamine could chelate with Cu2+ to form stable dopamine–Cu2+ complexes by strong coordination between Cu2+ and dopamine. It was found that the formation of dopamine–Cu2+ complexes hindered the Cu2+-catalyzed oxidation of the TMB–H2O2 system. As a result, in the presence of dopamine, the solution color changed from blue to colorless with a remarkable decrease of absorbance. Under optimized experimental conditions, the colorimetric sensor exhibited a linear range of 1 μM to 50 μM for dopamine detection, with a detection limit of 1 μM. Furthermore, the proposed method was successfully applied to determine the dopamine content in real samples. Compared with other reported methods, the colorimetric method could be performed within several minutes and did not require any complex or time-consuming preparation and purification process. The results suggested that this strategy would have potential applications in biotechnology and clinical diagnosis.

The authors describe a fluorometric glucose assay that is based on the use of MnO2 nanosheets and copper nanoclusters (CuNCs) acting as nanoprobes. The CuNCs were synthesized by using bovine serum albumin as a template by chemical reduction of copper(II) sulfate. On addition of MnO2 nanosheets to a colloidal solution of CuNCs, the fluorescence of CuNCs (measured at excitation/emission wavelengths of 335/410 nm) is quenched. However, in the presence of enzymatically generated H2O2, the MnO2 nanosheets are reduced to form Mn(II) ions. As a result, fluorescence intensity recovers. The glucose assay is based on the enzymatic conversion of glucose by glucose oxidase to generate H2O2 and glucuronic acid. The calibration plot is linear in the 1 μM to 200 μM glucose concentration range, and the detection limit is 100 nM. The method was successfully applied to the determination of glucose in spiked human serum samples.

A novel spatial-resolved electrochemiluminescent (ECL) ratiometry for cardiac troponin I (cTnI) analysis was developed using resonance energy transfer (RET) and a coreactant consumption strategy for signal amplification. Specifically, the spatial-resolved dual-disk glassy carbon electrodes were modified with CdS nanowires (CdS NWs) and luminol-gold nanoparticles (L-Au NPs) as potential-resolved ECL emitters, respectively. After stepwise immobilization of anti-cTnI and bovine serum albumin on the dual-disk electrodes, the CdS NWs-based electrode, with varied concentrations of cTnI, was used to provide a working signal, whereas the L-Au NPs-based electrode, with a fixed amount of cTnI, was employed to provide the reference signal. To efficiently amplify the working signal on the CdS NWs-based electrode, an anti-cTnI-reduced graphene oxide-gold nanoparticles-catalase probe (anti-cTnI-rGO-Au NPs-CAT) was loaded onto the electrode to form a sandwich immunocomplex. The RET from CdS NWs to Au NPs and the coreactant (i.e. H2O2) consumption by the CAT generate a significant ECL decrease on the CdS NWs-based electrode in the presence of cTnI. This novel and sensitive ratiometric detection mode for cTnI was achieved using the ratio values of the working signal of the CdS NWs-based electrode and the reference signal of the L-Au NPs-based electrode. The integration of RET and coreactant consumption strategy in the designed spatial-resolved ratiometric platform endows the immunosensor with a wide linear range of 5.0 × 10−13 – 1.0 × 10−7 g mL−1 and a low detection limit of 0.10 pg mL−1 for cTnI. Furthermore, the method exhibits high accuracy and sensitivity for cTnI determination in human serum samples.

A novel closed bipolar electrode-based electrochemiluminescence (BPE-ECL) imaging platform for visual detection of cardiac troponin I (cTnI) was constructed using tyramine signal amplification (TSA) strategy and enzyme-catalyzed precipitation techniques (BCP). In this platform, tyramine-HRP repeats formation and the BCP were executed on the cathodic pole in the presence of H2O2, which the ECL from Ru(bpy)32+/TPA system was used as signal reporter on the anodic pole. In the presence of cTnI, a large number of HRP from HRP-Au NPs-Ab compounds and tyramine-HRP repeats catalyze the formation of insoluble precipitation on the cathodic pole of the BPE, resulting in the decreased ECL from Ru(bpy)32+/TPA system on the anodic pole. Thanks to the TSA and BCP on the cathodic pole of the BPE platform, the method for cTnI detection exhibits the detection limits of 5.0 × 10−13 g/mL by a photomultiplier tube and 5.0 × 10-12 g/mL by a charge-coupled device imaging. Furthermore, the content of cTnI in human serum samples was determined and the recovery was between 90.0 % and 112.0 %. This multiple signal amplification strategy provides new perspectives for the BPE-ECL imaging platform in the biochemical analysis of biomarkers with low abundance.

Oxygen evolution reaction (OER) plays important roles in energy storage and conversion technologies, but the sluggish kinetics of OER may result in a large overpotential, and thus there is urgent need for the exploration of new electrocatalysts with a low overpotential and good stability. In this research, we integrate the melamine-assisted alkaline cobalt carbonate (CoCH) nanosheets pyrolysis with high-temperature solid phase fusion to construct the 1-C3N4/Co3O4/Ni foam hybrid electrode with Co3O4 ultrathin porous nanosheets as the host, trace C3N4 as the guest, and Ni foam (NF) as the current collector. Benefiting from the unique structure, the obtained 1-C3N4/Co3O4 hybrid nanosheets can significantly reduce the charge transfer distance between the catalysts to electron collector and improve the electron transportation during the OER process. Moreover, the intimate interaction of Co3O4 with C3N4 can induce a charge redistribution at the interface. Consequently, the 1-C3N4/Co3O4/NF hybrid electrode exhibits an enhanced OER performance (166 mV at 10 mA•cm−2) and good stability, superior to the commercial RuO2 particles and the reported transition metal-based electrocatalysts.

A novel photoelectrochemical (PEC) aptasensor for lead ion (Pb2+) detection was proposed on the basis of the CdSe quantum dots (QDs) co-sensitized ZnO-CdS nanostructure and the specificity of aptamer. The CdSe QDs-capped cDNA, as a signal enhancement element, could hybridize with the aptamer on the sensing platform to generate a CdSe/CdS/ZnO dual co-sensitized structure, realizing a great enhancement in photocurrent response. In the presence of Pb2+, the aptamer on the sensing interface specifically bound with the Pb2+ to form G-quadruplex structures, which greatly inhibit the hybridization between aptamer and CdSe QDs-cDNA, leading to a decrement of the photocurrent signal. As the concentration of Pb2+ increased, the photocurrent response showed a diminishing tendency. Under the optimized conditions, the fabricated PEC aptasensor exhibited a linear response between photocurrent variation and the logarithm of Pb2+ concentration in the scope of 1.0 × 10−9 M to 1.0 × 10−5 M with a detection limit of 3.4 × 10−10 M. Moreover, the aptasensor has been applied in the determination of Pb2+ in environmental water samples with the good selectivity.

A novel chemiluminescence (CL) imaging platform was constructed for prostate specific antigen (PSA) detection in a multiple signal amplifying manner. To construct the platform, the primary antibody for PSA was firstly immobilized on a O-ring area of a glass slide for recognizing the PSA. The horseradish peroxidase (HRP) and the secondary antibody of PSA (Ab2) functionalized Au NPs (HRP-Au NPs-Ab2) were modified on the platform through immunoreaction between PSA and Ab2. The excellent catalytic effect of Au NPs and HRP on the HRP-Au NPs-Ab2 to the luminol-H2O2 CL system provided the dual-signal amplification for PSA detection. To further enhance the sensitivity, tyramine signal amplification (TSA) strategy was introduced: tyramine-HRP conjugates were added into the O-ring reservoir and thus tyramine-HRP repeats formed in the presence of H2O2, generating a multiple signal amplification because of the large amounts of HRP on the sensing interface. The excellent performance of HRP-Au NPs-Ab2 and TSA strategy endows the CL platform with high sensitivity. The PSA was detected with a photomultiplier tube (PMT) and visually analyzed by a charge coupled device (CCD), respectively. The linear ranges of PMT and CCD for PSA are 0.1–100.0 ng mL-1 with a detection limit of 0.05 pg mL-1 and 0.5 – 100.0 ng mL-1 with a detection limit of 0.1 pg mL-1, respectively. The levels of PSA in several human serum samples were determined and the recoveries are ranged from 82.5% – 117.0%. This CL immunosensing platform holds great potential for bioactive molecules detection visually and sensitively.

A novel competitive electrochemiluminescence (ECL) aptasensor based on CdSe/ZnS quantum dots (QDs) functionalized MoS 2 modified electrode was developed for sensitive immunoglobulin E (IgE) detection using horseradish peroxidase (HRP) catalyzed biocatalytic precipitation (BCP) for signal quenching. MoS 2 was introduced to load QDs using PDDA as a bridge to form the MoS 2 -QDs composites which were employed as matrix for the immobilization of the complementary DNA (cDNA) of IgE aptamer, then HRP functionalized gold nanoparticles (AuNPs) labeled aptamer (aptamer-AuNPs-HRP) was designed as the signal probe for the aptasensor, the presence of HRP would stimulate the BCP onto the electrode surface for its insulating effect on ECL signal, thereby impairing the ECL emission. In the presence of IgE, the signal probe would capture IgE to form conjugation, released from the electrode accompanying decrease of HRP and increase of ECL intensity. Improved sensitivity is achieved through using the signal probe. This fabricated aptasensor displays a liner range from 0.5 pM to 0.5 nM with a detection limit of 0.18 pM ( S/N = 3). Moreover, eight human sera samples were analyzed with recoveries of 85.0–107.5%. The present strategy provides a promising method for the future development of ECL aptasensor for advanced biochemical analysis.

A sensitive capillary electrophoresis (CE) system coupled with electrochemiluminescence (ECL) of tris(2,2′-bipyridyl) ruthenium(II) is described for the detection of propranolol (Pro) and acebutolol (Ace). AuNPs were added to the end column luminescent reagents solution to enhance the sensitivity of the CE-ECL system. Experimental conditions of separation and detection as well as the amount of AuNPs were optimized. Under the optimum conditions, the linear range of Pro is 0.01 to 100 μmol L−1 with the LOD of 3.6 × 10−9 mol L−1 (S/N = 3) and with the LOQ of 1.1 × 10−7 mol L−1 in human urine samples (S/N = 10). For Ace, the linear range is 0.02 to 100 μmol L−1 with the LOD of 5.0 × 10−9 mol L−1 (S/N = 3) and with the LOQ of 9.5 × 10−8 mol L−1 in human urine samples (S/N = 10). RSDs (n = 3) of the migration time for Pro and Ace are from 1.9 to 2.4% intraday and from 2.9 to 3.8% interday. RSDs of the peak area for Pro and Ace are from 3.2 to 3.7% intraday and from 4.3 to 4.6% interday, respectively. The developed method was successfully used to determine two analytes in human urine samples. In addition, the interaction between Pro as a model analyte and human serum albumin (HSA) was investigated; the number of binding site and the binding constant of Pro with HSA are 1.0 and 2.3 × 104 L mol−1, respectively.

A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment. The CS@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity, which was further mechanically protected by graphene oxide (GO) nanolayers to fabricate intriguing configuration, which was beneficial for efficiently preventing the aggregation and oxidation of AgNPs and improving the electrical conductivity through intimate contact. By immobilizing this special material on electrode surface, the CS@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The tailored structure, fast electron transfer ability and facile preparation of CS@Ag@GO made it a promising electrode material for practical applications in phenols sensing.

A novel competitive electrochemiluminescence (ECL) aptasensor was designed for the detection of carcinoembryonic antigen (CEA) using carbon-coated petalous CdS nanopaticles (CdS–C petalous nanoparticles) as an ECL emitter and DNAzyme/Au nanorods–complementary DNA as a quenching probe. The quenching probe was firstly prepared by assembling guanine (G)-rich ssDNA and cDNA on Au nanorods and then reacting with hemin to form hemin/G-quadruplex DNAzyme units. CdS–C nanoparticles were synthesized and employed as the matrix for the construction of the CdS–C/Chit/aptamer platform. In the absence of CEA, the DNAzyme/Au nanorods as the quenching probe can be introduced by hybridization with aptamer on the surface of the sensing platform. In this state, DNAzyme immobilized on the probe catalyzes the reduction of H2O2, producing a decreased ECL emission. Upon both CEA and quenching probe addition, competitive reaction of the quenching probe and CEA with capture aptamer immobilized on the electrode occurred and thus resulted in the decreased amount of quenching probe on the electrode, which decreased the consumption of H2O2, producing an increased ECL signal. Based on this strategy, the aptasensor enables the sensitive detection of CEA in a range of 0.1 pg mL−1 to 0.5 ng mL−1 with a detection limit of 0.036 pg mL−1. The limit of quantification in human serum samples was experimentally found to be 0.21 pg mL−1. Moreover, the application of the aptasensor was demonstrated in the analysis of CEA in human serum samples with recoveries of 88.2–106%. The proposed method holds great promise in the highly sensitive and selective detection of CEA in biological samples.

In this paper, we report a facile route to synthesize yolk–shell structured copper oxide@silica oxide (CuO@SiO2) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030–10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues.