Ferrocenecarboxylic Acid Research Articles

Engineering of Molecular Bridge on Buried Interface via Ferrocene Carboxylic Acid for High Performance Perovskite Light‐Emitting Devices

AbstractQuasi‐two‐dimensional (Quasi2D) perovskite materials gained widespread attention due to whose unique and highly desirable luminescence properties. However, the behavior of perovskite lightemitting diodes (PeLEDs) is prejudiced by inefficient cascading energy transfer of perovskite film and unbalanced charges injection. Here, ferrocene carboxylic acid (FcAd) is employed between hole transport layer (HTL) and perovskite layer as a molecular bridge to solve the current problems of PeLEDs. Ferrocene units can bond with [PbBr6]4−, forming one‐dimensional (1D) intermediate phases of FcPbBr3 at the interface, which can manipulate the growth kinetics of perovskite and reconstruct the phase distribution. Therefore, due to the suppression of low dimensional phase content, not only is the cascaded energy transfer of PEA2(CsPbBr3)2PbBr4 films effectively achieved, but also the quasi‐2D perovskite's work function is reduced. Additionally, Pb2+ coordinated with the carboxyl group of FcAd, inducing an electric dipole effect that leads to an further upward shift of the perovskite energy level. Eventually, the synergy achieves a significant tailoring between the perovskite and HTL energy exhibits the most excellent external quantum efficiency (EQE) exceeds 27% and optimal brightness exceeds 240000 cd m−2. Therefore, the preparation method will provide an effective strategy to widen the color gamut of next‐generation displays.

Ferrocene carboxylic acid-doped copper MOFs as a nanozyme with high peroxidase-mimicking activity for catalytic dye degradation

A ferrocene carboxylic acid-doped copper–p-phthalic acid metal–organic framework material (Fc–Cu PTA) as a nanozyme exhibited high peroxidase-mimicking activity for catalytic dye degradation, while Cu PTA showed nearly no peroxidase-mimicking activity.

A NiMOF integrated with conductive materials for efficient bifunctional electrocatalysis of urea oxidation and oxygen evolution reactions.

The development of urea oxidation reaction (UOR) and oxygen evolution reaction (OER) bifunctional electrocatalysts has dual significance in promoting hydrogen energy production and urea-rich wastewater treatment. Herein, a carboxylated multi-walled carbon nanotube (MWCNT-COOH)-ferrocene carboxylic acid (Fc-COOH) modulated NiMOF hybrid material (MWCNT-NiMOF(Fc)) has been synthesized for dual electrocatalysis of the UOR and OER. The material characterization results indicated that MWCNT-COOH and Fc-COOH were integrated into the framework structure of the NiMOF. The direct interaction between the NiMOF and MWCNT/Fc facilitated electron transfer in the hybrid material and led to lattice strain, which improved the charge transfer kinetics, promoted the exposure of more unsaturated Ni sites, and increased the electrochemically active surface area. These factors together enhanced the electrocatalytic activity of MWCNT-NiMOF(Fc) towards the UOR and OER. Using a glassy carbon electrode as the substrate, MWCNT-NiMOF(Fc) exhibited low potential requirements, low Tafel slopes, and high stability. In overall urea and water splitting electrolysis cells, the excellent UOR and OER dual functional catalytic ability and enormous practical application potential of the MWCNT-NiMOF(Fc) modified foam nickel electrode were further demonstrated. On the basis of the above research, the influence of a KOH environment on urea electrolysis was further studied, and the urea electrolysis products were analyzed, promoting a more comprehensive understanding of the catalytic performance of MWCNT-NiMOF(Fc) for urea oxidation. This study provides a new approach for developing high-performance NiMOF-based electrocatalysts for challenging bifunctional UOR/OER applications, and has potential application value in hydrogen production from urea-containing wastewater electrolysis.

Fe-doped carbon dots: a novel fluorescent nanoprobe for cellular hypochlorous acid imaging.

Real-time monitoring of hypochlorous acid (HClO) in biological systems is of great significance for exploring and regulating its pathological functions because abnormal production of HClO is closely related with many diseases, such as atherosclerosis, rheumatoid arthritis, and cancer. Herein, we developed a reliable fluorescent Fe-doped carbon dots (Fe-CDs) for the sensitive and selective detection of biological HClO using ferrocenecarboxylic acid and m-phenylenediamine as precursors through a one-step solvothermal procedure. The Fe-CDs exhibited excellent a wide HClO detection range from 20nmol/L to 1000nmol/L with corresponding limits of detection at7.8nmol/L. The sensing mechanism is based on the chemical oxidation of the hydroxyl groups on the surface of Fe-CDs by HClO. In addition, Fe-CDs also displayed high photoluminescence yield, excitation-independence emission, as well as good biocompatibility, enabling the successful imaging of endogenous and exogenous HClO in HeLa cells. These results revealed that Fe-CDs holds great promise as a robust fluorescent probe for investigating HClO-mediated biological events.

Ratiometric antifouling electrochemical biosensors based on designed Y-shaped peptide and MXene loaded with Au@ZIF-67 and methylene blue.

Based on the designed inverted Y-shaped peptide and MXene nanocomposite (MXene-Au@ZIF-67), a ratiometric anti-pollution electrochemical biosensor was designed and applied to the detection of biomarkers in serum. Au@ZIF-67 inserted into the interior of MXene can not only prevent the accumulation of MXene but also provide a large amounts of binding sites for capturing biomolecules. A designed multifunctional Y-shaped peptide containing anchoring, antifouling, and recognition sequences was anchored onto MXene-Au@ZIF-67 through Au-S bonds. Electrochemical signal molecules, ferrocenecarboxylic acid (Fc) and methylene blue (MB), were modified to another end of multifunctional peptide and interior of MXene-Au@ZIF-67, respectively, to produce aratiometric electrochemical signal. We selected prostate specific antigen (PSA) as the modelcompound. PSA specifically recognizes and cleaves the recognition segment in the Y-shaped peptide, and the signal of Fc is reduced, while the signal of MB remains unchanged. The ratiometric strategy endows the present biosensorhigh accuracy and sensitivity with adetection limit of 0.85pg/mL. In addition, the sensing surface has good antifouling ability due to the antifouling sequence of the two branching parts of the Y-shaped peptide. More importantly, by replacing the recognition segment of peptides alsoother targetsare accessible, indicating the potential application of the universal detection strategy tothe detection of various biomarkers in clinical diagnosis.

Sandwich-type immunosensor based on aminated 3D-rGOF-NH2 and CMK-3-Fc-MgAl-LDH multilayer nanocomposites for detection of CA125

Cancer antigen 125 (CA125)11Cancer antigen 125 (CA125). is the most important biological screening indicator used to monitor epithelial ovarian cancers, and it plays a vital role in distinguishing ovarian cancers from benign diseases. Biosensors show great potential in the analysis and detection of disease markers. In this study, we designed electrochemical sensors based on three-dimensional amino-functionalized reduced graphene oxide (3D-rGOF-NH2),22three-dimensional amino-functionalized reduced graphene oxide (3D-rGOF-NH2). MgAl layered double hydroxide nanocomposites containing ordered mesoporous carbon (CMK-3),33ordered mesoporous carbon (CMK-3). and ferrocene carboxylic acids（Fc-COOH）44ferrocene carboxylic acids（Fc-COOH）.for the detection of CA125. 3D-rGOF-NH2 possesses good conductivity, a large surface area, and high porosity, enabling more immobilized nanoparticles to be deposited on its surface with excellent stability. CMK-3@Fc@MgAl-LDH nanocomposite was used as a carrier to enhance the immobilization of antibodies and the loading of Fc, conductors to enhance conductivity, and enhancers to gradually amplify the signal of Fc.The surface morphology, elemental composition, and surface groups of the materials were characterized using scanning electron microscopy (SEM),55scanning electron microscopy (SEM). transmission electron microscopy (TEM),66transmission electron microscopy (TEM). and X-ray diffraction (XRD)77X-ray diffraction (XRD). techniques. The response signal of the electrochemical sensor was measured by DPV. Under the optimal conditions, the electrochemical sensor obtained a linear detection range of 0.01 U/mL-100 U/mL with a detection limit of 0.00417 U/mL.

Ratiometric electrochemical lateral flow immunoassay for the detection of Streptococcus suis serotype 2

An electrochemical lateral flow immunoassay (eLFIA) strip with high reproducibility was developed to rapidly and accurately detect Streptococcus suis serotype 2. This proposed strip was fabricated by integrating ratiometric electrochemical detection and LFIA (R-eLFIA). The R-eLFIA exhibited excellent reproducibility, which was improved by 3.8 times compared to a single electrode. A dual-working screen-printed graphene electrode (SPGE) was designed by tuning the working electrode with electroactive species in the biosensing system. Ferrocene carboxylic acid (Fc) was used as a signal probe, and sunset yellow (SY) at one working electrode was used as an internal reference signal to provide a built-in correction for reducing the effects of inherent background current. S. suis serotype 2-specific antibodies were immobilized on a nitrocellulose membrane of LFIA, which is located on the position of Fc-SPGE. In the presence of the analyte, an immunocomplex formed on the region of Fc-SPGE, causing a decrease in Fc current while SY current remained constant. The current ratio's decrease was proportional to S. suis serotype 2's concentration. Under optimization, this biosensor showed good linearity in the range of 102–1010 CFU/mL with a limit of detection of 10 CFU/mL and achieved a rapid detection time (15 min). Moreover, the R-eLFIA biosensor exhibited excellent reproducibility and high selectivity and was applied in human serum samples. Thus, this study successfully matched the advantages of the ratiometric strategy and LFIA and has great potential to be used as an effective tool for rapidly detecting S. suis serotype 2 in clinical samples.

Redox-active polyphenol nanoparticles deprive endogenous glutathione of electrons for ROS generation and tumor chemodynamic therapy

Chemodynamic therapy (CDT) based on generating reactive oxygen species (ROS) is promising for cancer treatment. However, the intrinsic H2O2 is deficient for CDT, and glutathione (GSH) eliminates ROS to protect tumor cells from ROS cytotoxicity. Herein, we propose a strategy to switch the electron flow direction of GSH for O2 reduction and ROS generation rather than ROS clearance by using P(DA-Fc) nanoparticles, which are polymerized from ferrocenecarboxylic acid (Fc) coupled dopamine. P(DA-Fc) NPs with phenol-quinone conversion ability mimic NOX enzyme to deprive electrons from GSH to reduce O2 for H2O2 generation; the following •OH release can be triggered by Fc. Semiquinone radicals in P(DA-Fc) are significantly enhanced after GSH treatment, further demonstrated with strong single-electron reduction ability by calculation. In vitro and in vivo experiments indicate that P(DA-Fc) can consume intrinsic GSH to produce endogenous ROS; ROS generation strongly depends on GSH/pH level and eventually causes tumor cell death. Our work makes the first attempt to reverse the function of GSH from ROS scavenger to ROS producer, explores new roles of PDA-based nanomaterials in CDT beyond photothermal reagents and drug carriers, and provides a new strategy to improve the efficiency of CDT. Statement of SignificanceP(DA-Fc) nanoparticles performing tumor microenvironment response capacity and tumor reductive power utilize ability were fabricated for CDT tumor suppression. After endocytosis by tumor cells, P(DA-Fc) deprived GSH of electrons for H2O2 and •OH release, mimicking the intrinsic ROS production conducted by NADPH, further inducing tumor cell necrosis and apoptosis. Our work makes the first attempt to reverse the function of GSH from ROS scavenger to producer, explores new functions of PDA-based nanomaterials in CDT beyond photothermal reagents and drug carriers, and provides a new strategy to improve CDT efficiency.

Defect Engineered Metal–Organic Framework with Accelerated Structural Transformation for Efficient Oxygen Evolution Reaction

AbstractMetal–organic frameworks (MOFs) have been increasingly applied in oxygen evolution reaction (OER), and the surface of MOFs usually undergoes structural transformation to form metal oxyhydroxides to serve as catalytically active sites. However, the controllable regulation of the reconstruction process of MOFs remains as a great challenge. Here we report a defect engineering strategy to facilitate the structural transformation of MOFs to metal oxyhydroxides during OER with enhanced activity. Defective MOFs (denoted as NiFc′xFc1‐x) with abundant unsaturated metal sites are constructed by mixing ligands of 1,1′‐ferrocene dicarboxylic acid (Fc′) and defective ferrocene carboxylic acid (Fc). NiFc′xFc1‐x series are more prone to be transformed to metal oxyhydroxides compared with the non‐defective MOFs (NiFc′). Moreover, the as‐formed metal oxyhydroxides derived from defective MOFs contain more oxygen vacancies. NiFc′Fc grown on nickel foam exhibits excellent OER catalytic activity with an overpotential of 213 mV at the current density of 100 mA cm−2, superior to that of undefective NiFc′. Experimental results and theoretical calculations suggest that the abundant oxygen vacancies in the derived metal oxyhydroxides facilitate the adsorption of oxygen‐containing intermediates on active centers, thus significantly improving the OER activity.

Defect Engineered Metal-Organic Framework with Accelerated Structural Transformation for Efficient Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) have been increasingly applied in oxygen evolution reaction (OER), and the surface of MOFs usually undergoes structural transformation to form metal oxyhydroxides to serve as catalytically active sites. However, the controllable regulation of the reconstruction process of MOFs remains as a great challenge. Here we report a defect engineering strategy to facilitate the structural transformation of MOFs to metal oxyhydroxides during OER with enhanced activity. Defective MOFs (denoted as NiFc'x Fc1-x ) with abundant unsaturated metal sites are constructed by mixing ligands of 1,1'-ferrocene dicarboxylic acid (Fc') and defective ferrocene carboxylic acid (Fc). NiFc'x Fc1-x series are more prone to be transformed to metal oxyhydroxides compared with the non-defective MOFs (NiFc'). Moreover, the as-formed metal oxyhydroxides derived from defective MOFs contain more oxygen vacancies. NiFc'Fc grown on nickel foam exhibits excellent OER catalytic activity with an overpotential of 213 mV at the current density of 100 mA cm-2 , superior to that of undefective NiFc'. Experimental results and theoretical calculations suggest that the abundant oxygen vacancies in the derived metal oxyhydroxides facilitate the adsorption of oxygen-containing intermediates on active centers, thus significantly improving the OER activity.

Rapid electrochemical lateral flow device for the detection of Δ9-tetrahydrocannabinol

Cannabis is a plant that is harmful and beneficial because it contains more than 400 bioactive compounds, and the main compounds are Δ9 tetrahydrocannabinol (THC) and cannabidiol (CBD). Currently, cannabis extracts are used in medicine, but the amount of THC as a main psychoactive component is strictly regulated. Therefore, the ability to rapidly and accurately detect THC is important. Herein, we developed a sensitive electrochemical method combining a rapid lateral flow assay (LFA) to detect THC rapidly. An electrochemical LFA device was constructed by attaching a screen-printed electrode inside a lateral-flow device to exploit the remarkable binding of THC to the cannabinoid type 2 (CB2) receptor in the test zone. The ferrocene carboxylic acid attached to the monoclonal THC antibody acts as an electroactive species when it binds to the THC in the sample before it flows continuously to the CB2 receptor region on the electrode. Under optimal conditions, the detection time is within 6 min and the devise shows excellent performance with a detection limit of 1.30 ng/mL. Additionally, the device could be applied to detect THC in hemp extract samples. The results obtained from this sensor are similar to the standard method (HPLC) for detecting THC. Therefore, this proposed device is useful as an alternative device for the on-site determination of THC because it is inexpensive, portable, and exhibits high sensitivity.

Flips: Fluidic Integration of Printed Sensors

As NASA’s manned exploration programs advance toward more challenging missions including Martian spaceflight and long-term space habitation, novel technologies must be adapted for astronaut health monitoring and diagnostics. Among the technologies currently under development, In-Space Manufacturing (ISM) is an attractive approach because it mitigates the need to include multiple prefabricated sensors in spaceflight payloads instead allowing production of sensors on an as-needed basis by additive manufacturing techniques such as 3D-printing and inkjet printing. Several examples of ISM sensors have been demonstrated recently. However, liquid sample handling in microgravity environments produces several challenges, and consequently all liquid handling must be contained in a closed environment to prevent sample loss and contamination of crew quarters. Here we demonstrate the development of an ISM-compatible manifold for the fluidic integration of printed sensors (FLIPS). Our approach to the development of the FLIPS manifold is to identify components that cannot be manufactured using ISM techniques, and to fabricate all other components using flight-heritage 3D-printing and CNC cutting. FLIPS includes a mounted peristaltic pump and switch valve with measurements performed on off-the-shelf screen-printed carbon electrodes. We demonstrate the performance of the manifold with a model redox species (ferrocene carboxylic acid). Finally, we show the potential application as an integrated healthcare diagnostic system by detection of a renal health biomarker, alkaline phosphatase.This capability is necessary to ensure the success of ISM sensors for liquid samples and allows further customization of sensor architectures. The FLIPS platform demonstrates the applicability of ISM to complex fluid handling that will be adopted in future NASA missions.

Mono-coordinated defect toward metal-organic framework anode with remarkable electrochemical performance

The ultrahigh porosity and ligand tunability features of Metal organic frameworks (MOFs) make them excellent platforms for energy conversion and storage. Nevertheless, the practical applications of these materials are restricted due to their low conductivity and insufficient redox sites. Herein, a mono-coordinated ferrocenecarboxylic acid (Fc) was incorporated into MIL-53(Al) via a straightforward hydrothermal process to regulate the local coordination structure. In comparison to the MIL-53(Al) with a capacity of only 113 mAh/g, the MIL-53(Al)-Fc anode delivered an ultrahigh reversible capacity of 823 mAh/g over 700 cycles at 1 A·g−1. Furthermore, the developed MIL-53(Al)-Fc anode can exhibit a super high rate capacity of 489 mAh/g at 2 A/g. Importantly, it is discovered that the incorporation of Fc-doped MIL-53(Al) leads to a sustained increase in capacity throughout the process of charge/discharge cycling. Through a combination of experimental analysis and theoretical calculations, it has been demonstrated that the presence of unsaturated coordination metal sites into Fc-doped MIL-53(Al) not only improve its conductivity and the kinetics of Li+ storage, but also expose more reaction sites for Li+ facile desorption. This, in turn, facilitate the order–disorder transition during cycles. Meanwhile, the 1D nanorods morphologies can provide superior interaction between the active sites and electrolyte. Thus, this work will pave a new way to engineer advanced MOFs electrode materials for practical utilization of ultrahigh performance LIBs.

Formulation of DOX-dimer with bi-functionalized chitooligosaccharide for tumor-specific self-boosted drug release and synergistic chemo/chemodynamic therapy

The toxic side effects and possible drug resistance of the chemotherapeutics hinder their antitumor efficacy. Here, a pH/reactive oxygen species (ROS) dual-triggered nanodrug was developed for the tumor-specific self-boosted drug release and synergistic chemo/chemodynamic therapy, by formulating ROS-cleavable doxorubicin (DOX)-based dimer (DOX-TK-DOX) with bi-functionalized chitooligosaccharide (COS-Fc-TK) with ferrocenecarboxylic acid (Fc) and thioketal (TK). The resultant DOX-TK-DOX/COS-Fc-TK nanoparticles with a high DOX content of 39.70 % showed tumor-specific self-boosted drug release, which was triggered by highly toxic OH generated via Fc-catalyzed Fenton reaction of the endogenous H2O2 in tumor intracellular microenvironment. As a result, a synergistic chemo/chemodynamic therapy with combination index (CI) of 0.94 was achieved for selective treatment of tumors.

The Development and Evaluation of Reagentless Glucose Biosensors Using Dendritic Gold Nanostructures as a Promising Sensing Platform.

Reagentless electrochemical glucose biosensors were developed and investigated. A graphite rod (GR) electrode modified with electrochemically synthesized dendritic gold nanostructures (DGNs) and redox mediators (Med) such as ferrocenecarboxylic acid (FCA), 1,10-phenathroline-5,6-dione (PD), N,N,N',N'-tetramethylbenzidine (TMB) or tetrathiafulvalene (TTF) in combination with glucose oxidase (GOx) (GR/DGNs/FCA/GOx, GR/DGNs/PD/GOx, GR/DGNs/TMB/GOx, or GR/DGNs/TTF/GOx) were developed and electrochemically investigated. A biosensor based on threefold-layer-by-layer-deposited PD and GOx (GR/DGNs/(PD/GOx)3) was found to be the most suitable for the determination of glucose. To improve the performance of the developed biosensor, the surface of the GR/DGNs/(PD/GOx)3 electrode was modified with polypyrrole (Ppy) for 5 h. A glucose biosensor based on a GR/DGNs/(PD/GOx)3/Ppy(5 h) electrode was characterized using a wide linear dynamic range of up to 39.0 mmol L-1 of glucose, sensitivity of 3.03 µA mM-1 cm-2, limit of detection of 0.683 mmol L-1, and repeatability of 9.03% for a 29.4 mmol L-1 glucose concentration. The Ppy-based glucose biosensor was characterized by a good storage stability (τ1/2 = 9.0 days). Additionally, the performance of the developed biosensor in blood serum was investigated.

A label-free electrochemical aptasensor for low-density lipoprotein detection using MoS2-Au-Fc nanosheets as a high-performance redox indicator

Low-density lipoprotein (LDL) is a key biomarker involved in cardiovascular disease (CVD) risk assessment. Early-stage diagnosis of CVD complications by monitoring LDL levels could be a significant clinical tool and the first step toward adopting efficient therapy. Herein, a novel label-free electrochemical aptasensor for LDL detection was developed via the molybdenum disulfide-gold nanoparticle- ferrocene-carboxylic acid nanosheets (MoS2-Au-Fc NSs) enhanced signal amplification strategy. The MoS2-Au-Fc NSs were used not only as the biocompatible substrate for LDL aptamer (LDLapt) stabilization due to the increasing electrical conductivity and effective surface area, but also as a redox probe for monitoring the changes of the electrochemical signal because of good electroactive properties of Fc. The aptasensor fabrication steps were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). When LDL was captured onto the sensor via the specific affinity of the LDLapt, the formed LDLapt-LDL complexes shed from the electrode and enhanced the electron transfer rate on the electrode surface, resulting in an increase of the peak current. Thus, LDL can be easily detected by measuring the changes of peak current. Under ideal circumstances, the aptasensor was linearly correlated with logarithm LDL concentration from 0.001 to 100.0 μg/mL with R2 of 0.9914, and a low detection limit of 0.42 ng/mL. Furthermore, the LDL detected by aptasensor in actual serum samples with good actual errors (0.73%–5.00%) and satisfactory relative standard deviations (RSDs) (0.04%–0.84%). This study provides a new analytical method for measuring the level of LDL which is specifically up-regulated in CVD patients at an early stage.

Synthesis, crystal structure, and thermal behavior of Pt-based heterometallics [PtPy4](FcCOO)2 and trans-[PtPy2(FcCOO)2

Novel square-planar Pt-based heterometallic complexes with ferrocenecarboxylic acid were prepared in two steps from (tetrapyridine)platinum diacetate [PtPy4](OAc)2. The crystal structure of [PtPy4](FcCOO)2 and [PtPy2(FcCOO)2] was established by single crystal X-ray diffraction. Subsequent thermal transformation of a trinuclear compound [PtPy2(FcCOO)2] to a bimetallic Pt–Fe phase was studied by XAFS techniques.

Introducing non-bridging ligand in metal-organic framework-based electrocatalyst enabling reinforced oxygen evolution in seawater

Using seawater as the replacement of freshwater for electrolysis, with the integration of renewable energy, is deemed as an attractive manner to harvest green hydrogen. However, the complexity of seawater puts forward stricter requirement to the electrocatalyst to alleviate the chlorine electrochemistry and corrosion. Herein, a nanosheet array of NiFe-MOF@Ni2P/Ni(OH)2 is devised by partially substituting terephthalic acid (H2BDC) ligand by ferrocenecarboxylic acid (FcCA). Tailoring the active site into an under-coordinated fashion affords NiFe-MOF@Ni2P/Ni(OH)2 excellent performance towards oxygen evolution reaction (OER), only requiring the overpotentials of 302 mV and 394 mV in alkaline seawater to drive the current densities of 100 and 1000 mA cm−2, respectively. Moreover, the as-obtained electrocatalyst showed robust durability for operating more than 120 h at 500 mA cm−2 under harsh condition (6 M KOH + 1.5 M NaCl, 60 ℃). Density functional theory (DFT) calculations confirmed that tuning the coordination environment of Ni in NiFe-MOF by incorporating the non-bridging FcCA ligands could boost the formation of more active catalytic sites, which can simultaneously enhance the electronic conductivity and accelerate OER kinetics. This work provides beneficial enlightenment of combining MOF-based electrocatalyst with direct electrolysis of seawater.

Electrochemical lateral-flow device for rapid COVID-19 antigen-diagnostic testing

Antigen test kits (ATK) are extensively utilized for screening and diagnosing COVID-19 because they are easy to operate. However, ATKs exhibit poor sensitivity and cannot detect low concentrations of SARS-CoV-2. Herein, we present a new, highly sensitive, and selective device obtained by combining the principle of ATKs with electrochemical detection for COVID-19 diagnosis, which can be quantitatively assessed using a smartphone. An electrochemical test strip (E-test strip) was constructed by attaching a screen-printed electrode inside a lateral-flow device to exploit the remarkable binding affinity of SARS-CoV-2 antigen to ACE2. The ferrocene carboxylic acid attached to SARS-CoV-2 antibody acts as an electroactive species when it binds to SARS-CoV-2 antigen in the sample before it flows continuously to the ACE2-immobilization region on the electrode. Electrochemical-assay signal intensity on smartphones increased proportionally to the concentration of SARS-CoV-2 antigen (LOD = 2.98 pg/mL, under 12 min). Additionally, the application of the single-step E-test strip for COVID-19 screening was demonstrated using nasopharyngeal samples, and the results were consistent with those obtained using the gold standard (RT-PCR). Therefore, the sensor demonstrated excellent performance in assessing and screening COVID-19, and it can be used professionally to accurately verify diagnostic data while remaining rapid, simple, and inexpensive.

Dual-label vertical flow-based electrochemical immunosensor for rapid and simultaneous detection of hepatitis B surface and e virus antigens

The detection of hepatitis B virus (HBV)-associated biomarkers, especially hepatitis B surface (HBsAg) and hepatitis B e (HBeAg) antigens, is of critical significance for the early diagnosis and monitoring of disease progression. However, the detection of these biomarkers has seldom been reported. Herein, we first present a dual-label electrochemical vertical flow-based immunosensor (DL-eVFIS) for the simultaneous detection of HBsAg and HBeAg. DL-eVFIS was engineered to integrate multiple time-sequenced detection procedures into a single device, thus considerably shortening the overall assaying time to 6 min. To enable simultaneous determination, thionine (Th) and ferrocenecarboxylic acid (Fc) were employed as signal tags, as they demonstrate nonoverlapping specific reduction peaks. The appearance of target antigens resulted in a substantial increase in the electrochemical signal response of the redox tags. While requiring only a miniscule sample volume (5 µL), superior performance was achieved in terms of their limits of detection (LODs) at 1.66 pg/mL for HBsAg and 5.32 pg/mL for HBeAg. DL-eVFIS further demonstrates excellent specificity and selectivity in clinical sample analysis compared with the conventional method. This study contributes to next-generation point-of-care (POC) testing devices for HBV diagnosis and a wide range of biosensing applications.