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.

Self-powered photoelectrochemical aptasensor for fumonisin B1 detection based on a Z-scheme ZnIn2S4/WO3 photoanode.

The incidence of esophageal cancer is positively associated with fumonisin contamination. It is necessary to develop methods for the rapid detection of fumonisins. In this work, a self-powered photoelectrochemical aptamer sensor based on ZnIn2S4/WO3 photoanode and Au@W-Co3O4 photocathode is proposed for the sensitive detection of fumonisin B1 (FB1). Among them, under visible light irradiation, the Z-type heterostructure of ZnIn2S4/WO3 acts as a photoanode to improve the electron transfer rate, which contributes to the enhancement of the photocathode signal and lays the foundation for a wider detection range. The Au@W-Co3O4 photocathode as a sensing interface reduces the probability of false positives (comparison of anode sensing platforms). The PEC sensor has a good working performance in the detection range (10 pg/mL-1000 ng/mL) with a detection limit of 2.7 pg/mL (S/N = 3). In addition, the sensor offers good selectivity, stability and excellent recoveries in real sample analysis. This work is expected to play a role in the field of analyzing environmental toxins.

Phosphorus-rich CoP4@N-C nanoarrays for efficient nitrate-to-ammonia electroreduction.

The electrochemical nitrate reduction reaction (NO3-RR) is a novel green method for ammonia synthesis. However, the lack of sufficient catalysts has hindered the development of the NO3-RR. This research develops a transformation of porous CoP@N-C/CC into porous phosphorus-rich CoP4@N-C/CC through high-temperature calcination. Due to its unique phosphating-rich structure, CoP4@N-C/CC exhibits an excellent Faraday efficiency (FE: 92.3%) and NH3 yield (610.2 µmol h-1 cm-2). Such a catalyst with more P-P bonds can provide more active sites, effectively enhancing the adsorption and reaction processes of reactant molecules. In addition, the catalyst has good durability and catalytic stability, which provides a possibility for the future application of electrocatalytic ammonia production.

A sensitive immunosensor via Pd@Au0.85Pd0.15 in situ electrocatalysis generating H2O2 for quenching electrochemiluminescence of Ir(pbi)2(acac)@Ti3C2Tx MXene-PVA.

The establishment of rapid target analysis methods for cytokeratin fragment antigen 21-1 (CYFRA 21-1) is urgently needed. [Ir(pbi)2(acac)] (pbi = 2-(4-bromophenyl)-1-hydrogen -benzimidazole, acac = acetylacetonate) as traditional electrochemiluminescence (ECL) luminophores has been confined due to its non-negligible dark toxicity and poor water solubility leading to poor biocompatibility and electrical conductivity as an organic molecule. Hence, to overcome this limitation, [Ir(pbi)2(acac)] can be effectively loaded on the polyvinyl alcohol hydrogel modified Ti3C2Tx MXene surface (Ir@Ti3C2Tx-PVA) as sensing platform which can emit high ECL signals. Then, a quenching strategy was proposed to fabricate an ECL sandwich immunosensor using H2O2 as quencher molecules which can generated by Pd@Au0.85Pd0.15. Especially, the generation of O2 to H2O2 can be achieved through a two-electron (2e-) reaction pathway by Pd@Au0.85Pd0.15, to overcome the restriction that the H2O2 was virtually impossible to label or immobilize on the non-enzyme nanomaterials. The proposed ECL assay achieves a response to CYFRA 21-1 within the range of 0.1 pg/mL-100 ng/mL, with a detection limit of 8.9 fg/mL (S/N = 3). This work provided a feasible tactic to seek superior-performance ECL luminophore and quencher consequently set up a novel means to makeup ultrasensitive ECL biosensor, which extended the utilization potential of Ir(pbi)2(acac) in ECL assays.

Confinement-enhanced electrochemiluminescence by Ru(dcbpy)32+-functionalized γ-CD-MOF@COF-LZU1 porous hybrid material as micro-reactor for CYFRA 21-1 detection.

The improvement of electrochemiluminescence (ECL) performance relies on the electron transfer efficiency between luminophore and coreactant. An ultrasensitive ECL micro-reactor with confinement-enhanced performance was prepared by using the covalent organic framework-LZU1-functionalized metal-organic framework (MOF@COF-LZU1) as a platform to assemble enormous N,N-dibutyl-2-hydroxyethylamine (DBAE) and tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) [Ru(dcbpy)32+] into its pore channels. Compared to individual substances of γ-CD-MOF and COF-LZU1, the synergistic effects can conduce to the enhancement of the intensity, durability and sensitivity of the micro-reactor. Besides, COF-LZU1 can provide a mild environment to accommodate a certain amount of DBAE by concentrating them from the aqueous solution into its hydrophobic cavities and boost the oxidation efficiency of DBAE to generate more DBAE●+ and profited the survival of DBAE●, leading to an improved reaction efficiency with the Ru(dcbpy)32+ intermediate. Thanks to the confinement-enhanced strategy, engineered as high-functioning luminescent materials, Ru@γ-CD-MOF@COF-LZU1 micro-reactors decorated with Au NPs can facilitate electron transfer and capture primary antibodies (Ab1). Moreover, Au-Pd-Pt noble metal aerogels (NMAs) functionalized MoS2 NFs (Au-Pd-Pt NMAs@MoS2 NFs) were chosen as base material due to its large specific surface areas, high porosity, and excellent electrical conductivity. Based on above merits, the sensor demonstrated a sensitive response to CYFRA 21-1 detection in a linear concentration gradient from 10 fg/mL to 50 ng/mL with a detection limit of 0.0055 pg/mL (S/N = 3). The COF-LZU1 decorated ECL micro-reactors were constructed based on the signal amplification strategies to realize accurate CYFRA 21-1 detection.

Sulfur defect-engineered Bi2S3-x/In2S3-y mediated signal enhancement of photoelectrochemical sensor for lead ions detection.

Lead ions (Pb2+) are heavy metal ions that are harmful to living organisms and ecosystems. It is important to realize sensitive detection of Pb2+ in the environment. In this study, a signal enhancement photoelectrochemical (PEC) sensor with high sensitivity was constructed for the detection of Pb2+. Firstly, to obtain excellent electron transfer performance, sulfur defect-engineered Bi2S3-x/In2S3-y mediated signal enhancement formed by Bi2S3 and In2S3 with well-matched structure in terms of energy level as the substrate materials. In this case, the introduction of sulfur vacancies further affects the electronic structure of the material, which significantly improves the electrical conductivity and effectively increases the electron transfer rate. In addition, the as-synthesized Cu@Cu2O nanosphere is chosen as the marker to accelerate the electron transfer through the surface plasmon resonance effect of Cu. The constructed sensor was able to detect Pb2+ in the range of 1 ng mL-1-100 µg mL-1 with a limit of detection of 19.2 pg mL-1. The sensor exhibits good reproducibility, specificity, and stability, indicating such PEC sensor can achieve the sensitive detection of Pb2+ in the environment. This work paves a new way for the construction of PEC sensors and the specific PEC detection of Pb2+ in environmental waters.

A Co-Reactive Immunosensor Based on Ti3C2Tx MXene@TiO2-MoS2 Hybrids Promoting luminol@Au@Ni-Co NCs Electrochemiluminescence for CYFRA 21-1 Detection.

The construction of assays is capable of accurately detecting cytokeratin-19 (CYFRA 21-1), which is critical for the rapid diagnosis of nonsmall cell lung cancer. In this work, a novel electrochemiluminescence (ECL) immunosensor based on the co-reaction promotion of luminol@Au@Ni-Co nanocages (NCs) as ECL probe by Ti3C2Tx MXene@TiO2-MoS2 hybrids as co-reaction accelerator was proposed to detect CYFRA 21-1. Ni-Co NCs, as a derivative of Prussian blue analogs, can be loaded with large quantities of Au NPs, luminol, and CYFRA 21-1 secondary antibodies due to their high specific surface area. To further improve the sensitivity of the developed ECL immunosensor, Ti3C2Tx MXene@TiO2-MoS2 hybrids were prepared by in situ growth of TiO2 nanosheets on highly conductive Ti3C2Tx MXene, and MoS2 was homogeneously grown on Ti3C2Tx MXene@TiO2 surfaces by the hydrothermal method. Ti3C2Tx MXene@TiO2-MoS2 hybrids possess excellent catalytic performance on the electro-redox of H2O2 generating more O2·- and obtaining optimal ECL intensity of the luminol/H2O2 system. Under the appropriate experimental conditions, the quantitative detection range of CYFRA 21-1 was from 0.1 pg mL-1 to 100 ng mL-1, and the limit of detection (LOD) was 0.046 pg mL-1. The present sensor has a lower LOD with a wider linear range, which provides a new analytical assay for the early diagnosis of small-cell-type lung cancer labels.

Oxygen vacancies-driven signal enhanced photoelectrochemical sensor for mercury ions detection.

Mercury ion (Hg2+) poses a serious threat to human health due to its high toxicity. In this study, a smartphone-based photoelectrochemical sensor based on oxygen vacancies (OVs) driven signal enhancement for mercury ion detection was designed. BiVO4-x/Bi2S3/AuNPs were combined with T-Hg2+-T recognition mode to construct a multi-sandwich photoelectrochemical sensor. On the one hand, the OVs can increase the adsorption of light by the materials and enhance the photocurrent response as well as the superconductivity of Au NPs to accelerate the charge transfer at the electrode interface. On the other hand, the multi-sandwich structure was exploited to increase the binding site of Hg2+, as well as the T-Hg2+-T structure for sensitive recognition of Hg2+ and signal amplification. The sensor showed good linearity for Hg2+ concentration in the range of 0.1 nM-1.0 µM with a detection limit of 4.8 pM (S/N = 3). Eventually the smartphone-based real-time detection sensor is expected to contribute to the future analysis of heavy metal ions.

Europium Metal-Organic Framework with a Tetraphenylethylene-Based Ligand: A Dual-Mechanism Quenching Immunosensor for Enhanced Electrochemiluminescence via the Coordination Trigger.

The effective applications of electrochemiluminescence (ECL) across various fields necessitate ongoing research into novel luminophores and ECL strategies. In this study, self-luminous flower-like nanocomposites (Eu-tcbpe-MOF) were prepared by coordination self-assembly using the aggregation-induced emission material 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene (H4TCBPE) and Eu(III) ions as the precursors. Compared with the monomers and aggregates of H4TCBPE, Eu-tcbpe-MOF exhibits stronger ECL emission. Such enhanced electrochemiluminescence is due to coordination as the coordination-triggered electrochemiluminescence (CT-ECL) enhancement effect. In this study, a cubic-structured nanocomposite (Co9S8@Au@MoS2) was used as an efficient quencher, and a more sensitive ECL detection platform was achieved by two quenching mechanisms: resonance energy transfer and competitive consumption of coreactants. N,N-Diethylethanolamine (DBAE) was used as a coreactant, and DBAE has a faster electron transfer rate and stronger energy supply efficiency than the traditional anodoluminescent coreactant tripropylamine, which effectively improves the ECL signal intensity of Eu-tcbpe-MOF. Hence, a sandwich-type ECL immunosensor was prepared by employing a dual-quenching mechanism, utilizing Eu-tcbpe-MOF as the detection probe and Co9S8@Au@MoS2 as the quencher, achieving precise detection of carcinoembryonic antigen from 0.1 pg·mL-1 to 100 ng·mL-1 with a detection limit of 35.1 fg·mL-1.