Modified Electrode Material Research Articles

Bifunctional SnO2/NiO/rGO nanocomposite electrode for hydrogen evolution reaction and detection of winter wheat cold-resistant RNA.

Aconvenient, non-toxic, and low-cost tin dioxide (SnO2)/nickel oxide (NiO)/reduced graphene oxide (rGO) nanocatalytic electrode was investigated, which can effectively promote the hydrogen evolution reaction and can also be used to construct a sensitive winter wheat cold-tolerant RNA sensor. Due to the good synergy and photocurrent generation between SnO2 and NiO, which accelerates the electron transfer and catalyzes the hydrolysis reaction, the resultant data for the hydrogen evolution reaction in alkaline environment of this material are very impressive, with cathodic current densities of up to 10mAcm-2. The marvelous heterostructures and photovoltaic properties form a signal amplification system, which enables the nanocomposites to have an excellent linear sensitivity in low-concentration RNA solutions. The single-stranded complementary RNA of the target RNA was immobilized on the surface of the nanocomposites, which enabled the materials to recognize the target RNA under enzyme-free conditions. The test results showed that the modified electrode materials had good single detection performance in a wide linear range from 0.1nM to 2mM, with the limit of detection (LOD) of 0.078nM. The developed nanocomposite electrode has good performance in hydrogen evolution and winter wheat cold-resistant RNA detection, and is a bifunctional device with superior performance.

A nickel porphyrin-based covalent organic framework modified electrode for the electrochemical detection of acetaminophen.

Covalent organic frameworks (COFs) can be rationally designed with functional organic ligands to improve the electrochemical responsiveness of the electrode toward certain medicinal compounds. In this study, we synthesized a COF-Ni electrocatalyst material, which is formed by covalent coupling of electron-rich 2,3,6,7-tetrakis (4-formylphenyl) tetrakis (4-imidazolyl) (TTF-4CHO) and hole-rich 5,10,15,20-tetrakis (4-aminophenyl) porphyrin nickel(II) (TAPP-Ni). The reasonable electron transfer path design, the large specific surface area of the COF and the physical properties of ordered nanopores, as well as the Ni-N4 bond as a highly active catalytic center, allow the COF-Ni material modified electrode to exhibit excellent sensing performance for acetaminophen (ACOP). The detection limit for ACOP is as low as 47.6 nM, with a linear range of 1-1500 μM, which is better than for most of the reported sensors. With superior interference resistance and good stability performance, COF-Ni is a highly suited electrode modification material for real-world sample detection, which provided a new perspective for application of COF materials in drug analysis.

Electrochemical detection of quercetin at a Pt nanoaggregate-decorated Ti3C2-modified electrode

The surface chemical state of the electrode modification material, particularly crystal defects, significantly affects electrochemical detection properties. In this study, Ti3C2 decorated by Pt nanoaggregates (Pt NAs-Ti3C2) with enhanced crystal defect was developed for quercetin detection, where Pt nanoaggregates on Ti3C2 exhibit improved dispersibility and smaller particle size, generating a more favorable environment for interfacial catalytic reactions. A large specific surface area, the Pt NAs-Ti3C2 composite is beneficial for the adsorption and transfer of quercetin on the electrode surface. In comparison to Pt nanoaggregates with complete crystals, the Pt NA-Ti3C2-modified glassy carbon electrode (Pt NA-Ti3C2/GCE) demonstrates superior quercetin detection capabilities, achieving a detection sensitivity of 72.3 μA μM−1 and an outstanding detection linear region of 0.1–1500 nM. Besides, the electrode showcases excellent reproducibility with RSD of 2.41 %, repeatability with RSD of 1.08 %, and long-term stability with 92.3 % of the original signal retained, and resistance to interference, achieving accurately and selectively quercetin detection even in the presence of other ions and compounds. In addition, the Pt NA-Ti3C2/GCE allows for precise quercetin detection in real-life samples. Our findings establish a theoretical guideline and furnish the material foundation for the development of high-performance electrochemical sensors.

Bimetallic ions modified 2‐methylimidazolium functionalized polypyrrole/graphene oxide for the improved supercapacitor

AbstractThin films with two‐dimensional (2D) nanostructures possess good environmental stability, thinner thickness and large surface area, which are widely used as a promising modified electrode material in the field of energy storage, supercapacitors, electrochemical sensors and biosensors. Herein, unique bimetallic ions modified polypyrrole/graphene oxide (PPy/GO) nanosheets, including Co2+‐Zr4+/(2‐MeIm)x@PPy/GO and Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4), are prepared by using 2‐methylimidazolium (2‐MeIm) as the linkers between PPy/GO and metal ions. The obtained electrodes constructed by Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4) and Co2+‐Zr4+/(2‐MeIm)x@PPy/GO exhibit improved capacitor electrochemical properties due to the reversible redox reaction, the large specific surface area and the high theoretical specific capacitance value of the metal ions compared to the unmodified PPy/GO. Especially, the specific capacitance value of Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4) electrode reaches 321.78 F g−1 at a current density of 1 A g−1 and the capacitance retention rate is achieved to 100% in the long cycle charge/discharge test after 10 000 cycles (10 A g−1). It will provide a practical experience for the design and preparation of supercapacitors based on bimetallic ions modified PPy/GO.

Electrochemical detection of the cardiac biomarker cardiac troponin I

AbstractAcute myocardial infarction (AMI) is a major cause of cardiovascular disease‐related death. It is essential for patients with cardiovascular disease to receive an early diagnosis of AMI. The most popular technique for the early detection of AMI is the use of biosensors to monitor the concentration of pertinent biomarkers, such as cardiac troponin I (cTnI), in the blood. The electrochemical detection methods hold great promise because of their simplicity, miniaturization, ease of integration, high sensitivity, and rapid response. The prime motive of this review is to present a comprehensive understanding of the pros and cons of methodologies employed for the electrochemical approaches toward the detection of cTnI. A detailed summary is provided for the immunosensors, aptamer sensors, molecular imprinting sensors, and peptide sensors based on various affinity elements. We enumerate the modified electrode materials for electrochemical sensors as well as popular detection techniques. Furthermore, this paper reviews some recent significant advances in point‐of‐care assays for rapid, accurate detection of cTnI as a smart integrated device for home monitoring. The accumulation of knowledge about these functions will lead to new insights into and concepts for the design of portable miniature sensors for cardiovascular patients at risk of AMI. It is anticipated that the interdisciplinary collaboration can bring more enlightenment to the progress of cardiac biomarkers sensor in the future.

Structural Modification Strategy for Enhancing Electrochemical Performance of Electrodes Under High Current Cycling and First Principle Computational Research for Electrode Materials

Recently, there has been significant interest in advancing lithium-ion battery technology due to its widespread use in various applications. Our research delves into this domain, focusing on enhancing the electrochemical properties of batteries through structural modification of electrode materials. Our work demonstrates the significant enhancements of electrochemical performance under high current cycling using structurally modified electrode materials . In first work, crumpled graphene oxide anode proves to be an effective strategy for enhancing its electrochemical properties, attributed to its advantageous crumpled morphology. This morphology allows for improved electrode stability and easier access for lithium ions, enabling them to interact with its larger specific surface area. In second work, we describe enhanced the drawback of reduced electrochemical performance during high-rate cycles by synthesizing multidimensional LFP-based carbon composite. The lithium ion diffusivity and electrode stability of the prepared composite are significantly improved in charging and discharging cycles by introducing graphene quantum dots alongside CNTs, exhibiting superior electrochemical properties even at high current densities. In third work, density functional theory simulation is employed for demonstrating the enhanced electrochemical properties of prepared electrodes by exploring their properties. Our research provides insights into electrode material design as an effective approach to enhancing the electrochemical properties of lithium-ion batteries.Acknowledgement:This work was supported by the National Research Foundation of Korea (NRF-2021R1A2C1008272). This work was supported by Ministry of Trade, Industry and Energy, KEIT, under the project title"International standard development of evaluation methods for nano-carbon-based high-performance supercapacitors for electric vehicles" (project # 20016144).

Orientation-dependent electronic structure of Li2WO4 films epitaxial grown on LiCoO2 by spontaneous lithiation

Understanding and modulating the properties of materials requires a deep knowledge of their electronic structures. However, analysis of the electronic structure of a single material can be challenging, particularly for modified electrode materials, due to the complexity of mixed interface structures. In this study, we employ pulsed laser deposition (PLD) to epitaxially synthesize Li₂WO₄ (LWO) films on LiCoO₂ (LCO) layers with different orientations. Based on a series of high-resolution synchrotron-based techniques including X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), the electronic structure of LWO is carefully scrutinized where a higher main energy level of W5d(eg)-O2p orbitals hybridization in LWO/LCO(104) as compared to LWO/LCO(003) has been observed. This experimental finding is further validated by a comprehensive set of density of states calculations. Furthermore, detailed polarized XAS characterization unveils distinct anisotropy between the two oriented LWO configurations. This comprehensive scientific investigation, harnessing the capabilities of synchrotron-based techniques, provides invaluable insights for future studies, offering guidance for the optimized utilization of LWO as a solid-state electrolyte or modification layer for LCO cathodes in high-powered Li-ion batteries.

Bipyridine-functionalized covalent-organic-framework-modified screen-printed electrode for ultrasensitive electrochemical determination of arsenic (III)

The high toxicity of the arsenic ion (As3+) and its proliferation as a contaminant make it a significant threat to the environment as well as to human beings. Therefore, recent years have witnessed the development of novel strategies for the ultrasensitive detection of As3+. In this study, we design a covalent organic framework (COF) to modify a screen-printed electrode for the ultrasensitive electrochemical determination of As3+ via square wave anodic stripping voltammetry (SWASV). As a proof of concept, we propose a novel bipyridine-containing COF, namely BPTB, which is a screen-printed electrode modification material with a large Brunauer–Emmett–Teller (BET) surface area, high selectivity, and good anti-interference properties. The extremely selective As3+ receptors are the nitrogen-based sites, and the bipyridine-group skeleton serves as a signal transducer. The COF-modified screen-printed electrode exhibits an ultralow detection limit of 38.09 nmol/L and a wide linear response range of 0.1–80 μmol/L for As3+ determination under optimal conditions. In addition, the electrochemical properties of the COF-modified screen-printed electrode are characterized via cyclic voltammetry and electrochemical impedance spectroscopy. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis confirms the existence of a strong interaction between the bipyridine sites of BPTB and As3+, which influences the stripping current intensity of the modified screen-printed electrode. In summary, this study not only highlights the application potential of COFs for the electrochemical determination of As3+ but also demonstrates a novel, convenient approach for constructing COFs by creatively introducing chelating sites for toxic metals.

Construction of a microfluidic electrochemical sensor based on screen printing electrode for the detection of fluoxetine

Fluoxetine (FLX) is a widely-used antidepressant, and monitoring its blood drug concentration is crucial to ensure treatment effectiveness and prevent drug-related adverse reactions. This study constructed a microfluidic electrochemical sensor (COFTpTt@c-MWCNTs/SPCE) for the detection FLX in microliter-scale samples. Firstly, polydimethylsiloxane (PDMS) to construct microfluidic chip, the internal microchannels and structures significantly reduced the necessary sample volume for detection. Subsequently, the covalent organic framework material (COFTpTt) was synthesized by the solvothermal reaction of 1,3,5-triformylphloroglucinol (Tp) and melamine (Tt). This material was then combined with carboxylated multi-walled carbon nanotubes (c-MWCNTs) to form COFTpTt@c-MWCNTs, serving as the electrode modification material. COFTpTt with strong loading capacity and a large specific surface area, forming hydrogen bonds with FLX molecules and enhanced sensor selectivity. c-MWCNTs have excellent electron transfer capability. COFTpTt@c-MWCNTs were drop-coated onto the screen-printed carbon electrode (SPCE), integrated with the chip, forming the sensor. The inherent electrochemical activity of FLX enabled label-free detection. After optimizing the COFTpTt and c-MWCNTs ratio, the amount of COFTpTt@c-MWCNTs modification, and FLX solution pH, differential pulse voltammetry (DPV) was used to detect FLX solutions. The sensor showed a good linear relationship of FLX in the range 62.5–2000 ng mL−1 with a low limit of detection (LOD) of 24.3 ng mL−1 (S/N = 3) and good reproducibility and selectivity. This sensor had been successfully used for FLX detection in spiked rat serum samples, offering the potential for point-of-care testing of FLX.

Sensitive detection of cardiac glycoside digoxin based on sheet like structured cerium manganese oxide electrocatalyst

Digoxin (DGN), a widely used cardiac glycoside steroid for treating heart diseases. The prescription dosage range of digoxin is 0.5 – 2.0 ng/mL and concentration above 2 ng/mL can lead to intoxication. To monitor and detect digoxin in blood level is essential to minimize the endanger toxicity of human health. Addressing this concern, here we prepare a cerium manganese oxide (CMO) catalyst by a simple chemical coprecipitation method followed by heat treatment. The CMO morphological and structural characteristics were investigated by various spectroscopic techniques. The electrochemical properties of CMO catalyst were evaluated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques, which also determined its electrochemical performance. Due to the high conductivity and large surface area with abundant active sites, CMO catalyst was used as a modified electrode material for detecting DGN in biological samples. The CMO sensor exhibits excellent electrocatalytic performance, with a dynamic linear range of 7.81 ×10–6 pg/L to 430 ×10–6 pg/L. The limit of detection and limit of quantification (LOD and LOQ) were found to be 1.99 ×10–6 pg/L and 6.05 ×10–6 pg/L, respectively. Furthermore, the sensor’s efficiency was validated through selectivity test and analysis of biological samples such as human blood and urine.

Electrochemical Performance of Polyaniline‐Polyvanadate‐Copper Nanomaterials for the Detection of Benzoic Acid

AbstractThe introduction of nanomaterials as modified electrode materials into the field of electrochemical sensing is expected to improve the reliability, sensitivity, selectivity and repeatability of electrochemical sensors in detecting pollutants in the water environment. In this study, copper vanadate nanomaterials (Cu3V2O7(OH)2·2H2O, referred to as CVO) and Cu3V2O7(OH)2·2H2O/polyyaniline (PANI) composite nanomaterials (referred to as CVO/PANI) are successfully prepared and characterized by Fourier transform infrared spectrum (FTIR), X‐ray traveling‐action (XRD), scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HR‐TEM). The modified glassy carbon electrodes (GCE) with these two materials are used for the detection of benzoic acid (BA) and exhibit excellent electrochemical sensing performance. The results show that two pairs of semi‐reversible redox peaks exist in both CVO and CVO/PANI modified glassy carbon electrode (GCE) in BA solution. The linear range of CVO and CVO/PANI nanomaterials‐modified GCE is 0.01–2 mm and 0.001–2 mm, and the limits of detection are 2.16 and 0.41 µm, respectively. PANI plays important role in the electrochemical responses of BA at CVO/PANI modified GCE. PANI enhances the intensities of CV peaks and electrochemical determination ability for BA.

Electrochemical aptasensor based on CRISPR/Cas12a-mediated and DNAzyme-assisted cascade dual-enzyme transformation strategy for zearalenone detection

The combination of the CRISPR/Cas system and biosensing is of profound significance in small molecule diagnostics. Herein, we report a cascade dual-enzyme transformation strategy for ultrasensitive analysis of zearalenone (ZEN) by utilizing the CRISPR/Cas12a trans-cleavage activity and DNAzyme amplification. NH2-MnO2/Pd@Au NBs nanocomposites are greatly promising electrode modification material for improving electrode sensing performance. PtPd@Fe3O4 nanocomposites are synthesized as signal label materials to load the electroactive molecule methylene blue (MB). The recognition of ZEN target and aptamer is converted into DNA signal to regulate the trans-cleavage activity of the CRISPR/Cas12a on Mg2+-DNAzyme probes. After that, in the presence of DNAzyme probes and Mg2+, the MB signal changes caused by Mg2+dependent DNAzyme-assisted catalytic cleavage of signal labels on the electrode surface are evaluated. The quantitative detection of ZEN is ultimately achieved. Under optimal conditions, the as-prepared electrochemical aptasensor shows a wide linear detection range of 1 × 10-5 to 10 ng·mL−1, and the detection limit is 6.27 × 10-6 ng·mL−1. Moreover, the constructed aptasensor exhibits satisfactory selectivity, stability and repeatability, which also has a wide application prospect in the real sample analysis.

Facilely prepared Co-based MOF functionalized N, S-doped reduced graphene oxide for electrochemical non-enzymatic glucose sensing

Rational design of modified electrode materials is critical for electrochemical sensors. Metal-organic frameworks (MOFs), a novel sort of substance with porosity, has received widespread attention owing to various superior characteristics such as adjustable pore sizes, great surface area and controllable structures. Nevertheless, the poor charge transfer capability of MOFs leads to a general suppression of their electrochemical sensing performance. To solve this issue, compositing conductive substance with MOFs have been demonstrated to be an effective strategy. Herein, Co-based MOF (ZIF-67) functionalized N, S-doped reduced graphene oxide (N, S-RGO) heterostructure (ZIF-67/N, S-RGO) was fabricated through an in-situ synthesis method. The composite material was used in the modification of an electrode to construct a sensing platform for non-enzymatic glucose testing. The synergistic interaction of ZIF-67 and N, S-RGO not only provided more efficient active sites and larger surface areas, but also improved the electron transport efficiency and electrocatalytic performance. Under optimized conditions, the ZIF-67/N, S-RGO/GCE had a dynamic linear range of 1–3200 μM, with a detection limit of 0.33 μM (S/N = 3) for glucose detection. The sensing platform also provided excellent reproducibility, selectivity, and stability (70 % activity retained after 12 days). Furthermore, the sensor had the potential to apply for glucose determination in human serum. This work presented a novel strategy to the field of non-enzymatic glucose sensing and may provide effective coaching for optimizing the electrochemical sensing performance of other series of MOFs.

An electrochemical aptasensor based on MOF-derived bimetallic carbon nanocomposites Au@Cu-C for ultrasensitive detection of homocysteine on portable potentiostat

Homocysteine (Hcy), a metabolic intermediate of methionine, is a biomarker for neurological, cardiovascular and cerebrovascular diseases. Timely measurement of Hcy acts as a significant role in disease prevention and diagnosis. Given the fast response of the electrochemical sensing method, herein, a sensitive electrochemical aptasensor was proposed for the detection of Hcy. The aptasensor was constructed by utilizing the MOF-derived bimetallic carbon nanocomposites (Au@Cu-C) plus multi-walled carbon nanotubes (MWCNTs) as electrode modification materials and methylene blue (MB) as the signal marker. The Au@Cu-C was synthesized through hydrothermal methods, calcination and simple galvanic replacement reactions. The prepared Au@Cu-C enhance the electrical signal due to the synergistic effect of bimetallic alloy, while the specific morphology facilitated the immobilization of the aptamer. MB, served as the signal marker, can reflect the current changes of the aptasensor caused by the conformational change of aptamer before and after binding Hcy. As a result, the constructed electrochemical aptasensor exhibited a high sensitivity of 0.415 μA μM−1, a low detection limit of 0.017 μM and an excellent recovery rate in the detection of human serum samples. Besides, the detection was performed on the portable potentiostat which demonstrated the potential application of the aptasensor in medical diagnosis and on-site analysis.

A novel electrochemical aptasensor based on AgPdNPs/PEI-GO and hollow nanobox-like Pt@Ni-CoHNBs for procymidone detection

Herein, an aptasensor based on a signal amplification strategy was developed for the sensitive detection of procymidone (PCM). AgPd nanoparticles/Polenimine Graphite oxide (AgPdNPs/PEI-GO) was weaned as electrode modification material to facilitate electron transport and increase the active sites on the electrode surface. Besides, Pt@Ni-Co nanoboxes (Pt@Ni-CoHNBs) were utilized to be carriers for signaling tags, after hollowing ZIF-67 and growing Pt, the resulting Pt@Ni-CoHNBs has a tremendous amounts of folds occurred on the surface, enables it to carry a larger quantity of thionine, thus amplify the detectable electrochemical signal. In the presence of PCM, the binding of PCM to the signal probe would trigger a change in electrical signal. The aptasensor was demonstrated with excellent sensitivity and a low detection limit of 0.98 pg·mL−1, along with a wide linear range of 1 μg·mL−1 to 1 pg·mL−1. Meanwhile, the specificity, stability and reproducibility of the constructed aptasensor were proved to be satisfactory.

Conductive Metal-Organic Framework Grown on the Nickel-Based Hydroxide to Realize High-Performance Electrochemical Glucose Sensing.

Glucose holds significant importance in disease diagnosis as well as beverage quality monitoring. The high-efficiency electrochemical sensor plays a crucial role in the electrochemical conversion technology. Ni(OH)2 nanosheets are provided with high specific surface area and redox activity that are widely used in electrochemistry. Conductive metal-organic frameworks (cMOFs) perfectly combine the structural controllability of organic materials with the long-range ordering of inorganic materials that possess the characteristic of high electron mobility. Based on the above considerations, the combination of Ni(OH)2 and Ni-HHTP (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene) as an electrode modification material is designed to enhance electrochemical performance. In this work, to improve glucose detection, a sequence of Ni(OH)2@NiCo-HHTP and NiM-LDH@Ni-HHTP (M=Co2+, Mn2+, Cu2+, LDH=layered double hydroxide) are successfully synthesised by doping metals into Ni-HHTP and Ni(OH)2, respectively. As a result, NiCu-LDH@Ni-HHTP showed the best excellent glucose detection sensitivity.

Surface-Activated Ti3C2Tx Adsorption of Acetylene Black Coupled with Polyaniline as a Signal Tag for the Detection of the ESAT-6 Antigen of Mycobacterium tuberculosis.

Early secretory antigenic target-6 (ESAT-6) is regarded as the most immunogenic protein produced by Mycobacterium tuberculosis, whose detection is of great clinical significance for tuberculosis diagnosis. However, the detection of the ESAT-6 antigen has been hampered by the expensive cost and complex experimental procedures, resulting in low sensitivity. Herein, we developed a titanium carbide (Ti3C2Tx)-based aptasensor for ESAT-6 detection utilizing a triple-signal amplification strategy. First, acetylene black (AB) was immobilized on Ti3C2Tx through a cross-linking reaction to form the Ti3C2Tx-AB-PAn nanocomposite. Meanwhile, AB served as a conductive bridge, and Ti3C2Tx can synergistically promote the electron transfer of PAn. Ti3C2Tx-AB-PAn exhibited outstanding conductivity, high electrochemical signals, and abundant sites for the loading of ESAT-6 binding aptamer II (EBA II) to form a novel signal tag. Second, N-CNTs were adsorbed on NiMn layered double hydride (NiMn LDH) nanoflowers to obtain NiMn LDH/N-CNTs, exhibiting excellent conductivity and preeminent stability to be used as electrode modification materials. Third, the biotinylated EBA (EBA I) was immobilized onto a streptavidin-coated sensing interface, forming an amplification platform for further signal enhancement. More importantly, as a result of the synergistic effect of the triple-signal amplification platform, the aptasensor exhibited a wide detection linear range from 10 fg mL-1 to 100 ng mL-1 and a detection limit of 4.07 fg mL-1 for ESAT-6. We envision that our aptasensor provides a way for the detection of ESAT-6 to assist in the diagnosis of tuberculosis.

Regulation of triazine-COF and CoAl-LDH substrates in composites for high-performance neurofilament-light chains electrochemical immunosensors

Early diagnosis of Alzheimer’s disease (AD) can be achieved through the detection of neurofilament light chain (NfL) biomarker, which can slow down the progress of AD and improve quality of life for patients. In this paper, polyvalent Tb-metal organic frameworks (Tb-MOF) and CoAl-layered double hydroxides (CoAl-LDH) are directly acceded to the synthesis system of triazine-covalent organic frameworks (triazine-COF) using one-pot synthesis to obtain the COF-based composite (COF/MOF-LDH). Similarly, the composite of LDH-based (LDH/MOF-COF) is acquired by integrating Tb-MOF and triazine-COF into the synthesis system of CoAl-LDH via hydrothermal procedure. COF/MOF-LDH and LDH/MOF-COF are used as electrode modification materials to construct label-free electrochemical immunosensors for anchoring and detecting NfL. Under optimal conditions for detecting NfL, both modified sensors exhibit high degree of selectivity, stability and reproducibility. However, the COF/MOF-LDH sensor displays a wider linear concentration range (0.05 pg/mL - 100 ng/mL) with lower limit detection of 0.017 pg/mL (S/N=3), and high sensitivity of 130.8 μA·ng−1·mL·cm−2, attributing to large conjugation system of triazine-COF used for substrate modulation and the immobilisation of the anti-NfL through strong π-π* affect and hydrogen bonding. Likely, the incorporation of polyvalent Tb-MOF and CoAl-LDH in COF/MOF-LDH considerably enhance sensitivity via improving active sites and response signals. Furthermore, the morphology, pore size and specific surface area differences of the composites are a reflection of the results of the substrate material control strategy. Especially, the N2 adsorption/desorption tests indicate the larger mesoporous structure of COF/MOF-LDH which facilitate the electron transfer and anti-NfL immobilization. Taken together, the immunosensor based on COF/MOF-LDH shows excellent detection performance which provides a pathway for early screening of AD.

A novel electrochemical immunosensor for sensitive detection of depression marker Apo-A4 based on bipyridine-functionalized covalent organic frameworks.

Anovel electrochemical immunosensor for detecting potential depression biomarker Apolipoprotein A4 (Apo-A4) was developed using a multi-signal amplification approach. Firstly, the sensor utilized a modified electrode material, NG-PEI-COF, combining bipyridine-functionalized covalent organic framework (COF) and polyethyleneimine-functionalized nitrogen-doped graphene (NG-PEI), providing high surface area and excellent electron transfer capability for the first-stage amplification in electrical signal conduction. Subsequently, gold nanoparticles (AuNPs) were further electrodeposited onto the electrode, providing good biocompatibility and abundant binding sites for immobilizing the target antigen, thus achieving the second-stage amplification in target recognition and binding. To address the lack of redox properties of the antigen, a tracer probe was formed by loading AuNPs, anti-Apo-A4, and toluidine blue (TB) successively onto COF, leading to the third-stage amplification in signal conversion. The constructed electrochemical immunosensor TB/Ab/AuNPs/COF-Apo-A4/AuNPs/NG-PEI-COF/GCE exhibited excellent detection performance against Apo-A4 with a linear range of 0.01 to 300 ng mL-1 and had a low detection limit of 2.16 pg mL-1 (S/N = 3). In addition, the biosensor had good reproducibility (RSD = 2.31%), stability, and significant anti-interference performance toward other depression biomarkers. The sensor hasbeen successfully used for the quantitative detection of Apo-A4 in serum, providing potential applications for detecting Apo-A4 in the clinic and serving as a reference for constructing sensing methods based on COF.

Electrochemically Mediated Lithium Extraction for Energy and Environmental Sustainability

AbstractThe demand for lithium resources is growing rapidly due to the continuous development of the lithium‐ion battery, which plays an important part in the renewable energy industry. Global sources of lithium are ores and brine, of which 59% are distributed in saline brine. However, the significant lithium resources in saline brine have not been fully utilized. The electrochemical deintercalation method (EDM) for lithium extraction from saline brine is a promising technique because of its environmental friendliness, high selectivity, and cost‐effectiveness. Nevertheless, the application of EDM is greatly limited by the easy dissolution of electrode materials like LiMn2O4 and the cost of mass production. Also, there are a few existing review articles on the EDM for lithium extraction. To address this gap, this review provides a comprehensive overview of the current methods for lithium extraction from saline brine, systematically summarizes the technical status of the EDM, and pays special attention to the preparation method and modification of electrode materials. This review gives new insight into the mechanism of EDM and provides a new design strategy for the evaluation methods of EDM.