Electroanalytical Applications Research Articles

Electrochemistry probed one molecule at a time

Probing electrochemical reactions at the single-reaction level is the ultimate goal for electroanalytical chemistry. The development of electrical approaches and optical methods has enabled addressing the electrochemistry of individual molecules in various systems such as scanning probe microscopy, fixed nanogaps, nanopores, single-molecule fluorescence microscopy, and single-molecule electrochemiluminescence microscopy, which can bring new views on fundamental electrochemistry, electroanalytical applications, and electrochemical cells. We conclude with potential directions for further improving the spatial and temporal resolution and developing new techniques towards meeting the requirements for achieving the outlined goals.

Anion engineering guided MOF-to-hollow nickel phosphate transformation enabling robust electrochemical platforms for detection of hydrogen peroxide and hydrazine

Rationally designing of transition metal phosphate (TMP) with charming structure and exploiting their electroanalytic functionalities are of great potential and challenging. Herein, in-situ adoption of MOF as the framework and skillfully regulation of the evolution process through the mass ratios of sodium phosphate (namely as both etchants and reactants) and Ni-MOFs led to the configuration of a series of nickel phosphate (NiP) counterparts with well-defined structures and definable compositions, and further their bifunctional sensing performance for H2O2 and N2H4 were investigated, where the ratio of 4:3 prepared NiP, with pure ingredient, amorphous states and 2D scaly nanosheets uniformly decorated 3D hollow scaffolds, collectively reveals rich electrocatalytic sites, shorten ion transfer/diffusion channels and excellent electrical conductivity, thus affording an significant enhancement for its electrochemical behaviors, especially its low detection limit (27.9 nM and 45.1 nM) and wide measurable range (0.001–2.6 mM and 0.005–4.5 mM) for H2O2 and N2H4, respectively. Additionally, its powerful anti-interference and recognition for H2O2 and N2H4 in water samples verify the practicality of our electrochemical platforms. Our design establishes the promising strategy for engineering of new class MOF-derived diversified functionally materials for electroanalytical application and beyond.

A Sensor for Selective Dopamine Determination Based on Overoxidized Poly‐1,5‐Diaminonaphthalene on Graphene Nanosheets

AbstractAn effective nanocomposite sensor for selective electroanalytical dopamine (DA) determination using overoxidized conducting polymer of poly‐1,5‐diaminonaphthalene (OPoly‐1,5‐DAN) functionalized graphene nanosheets (GNS) was achieved. The OPoly‐1,5‐DAN/GNS nanocomposite polymer was prepared via an electropolymerization of 1,5‐DAN on GNS/GCE after 7 cycles of potential scan (−0.2 V to +0.9 V), followed by an electrooveroxidation of the nanocomposite Poly‐1,5‐DAN/GNS by the potential cycle (0.0 V to +1.8 V) for 2 scans. The OPoly‐1,5‐DAN was effectively designed by GNS as a uniformly distribution of nanocomposite that caused more accumulations of analyte due to large electrocatalytic active positions created on electrode surface. The high specific and sensitive performance of the OPoly‐1,5‐DAN/GNS nanocomposite polymer was conducted to greater effective electrons transferring behavior for DA with copresent of vitamin C (VC). The stable and suitable formation of OPoly‐1,5‐DAN/GNS nanocomposite polymer showed rapid charge transport voltammogram and obvious electrocatalytic activity to DA and eliminated VC response. Moreover, the OPoly‐1,5‐DAN/GNS displays an excellent responses to DA determination with wide linear range (LR) 1.0–150 μM and lower detection limit (DL) 8.82±0.1 nM as comparing with other studies. Additionally, the excellent reproducibility of OPoly‐1,5‐DAN/GNS as well as long‐term stability indicated that it is an excellent and effective electrochemical DA sensor. Finally, the electroanalytical application of the OPoly‐1,5‐DAN/GNS nanocomposite polymer was employed for the electroanalysis of DA in human urine.

Stochastic Collision Electrochemistry from Single Pt Nanoparticles: Electrocatalytic Amplification and MicroRNA Sensing.

Single-particle collisions have made many achievements in basic research, but challenges still exist due to their low collision frequency and selectivity in complex samples. In this work, we developed an "on-off-on" strategy based on Pt nanoparticles (PtNPs) that catalyze N2H4 collision signals on the surface of carbon ultramicroelectrodes and established a new method for the detection of miRNA21 with high selectivity and sensitivity. PtNPs catalyze the reduction of N2H4 on the surface of carbon ultramicroelectrodes to generate a stepped collision signal, which is in the "on" state. The single-stranded DNA paired with miRNA21 is coupled with PtNPs to form the complex DNA/PtNPs. Because PtNPs are covered by DNA, the electrocatalytic collision of N2H4 oxidation is inhibited. At this time, the signal is in the "off" state. When miRNA21 is added, the strong complementary pairing between miRNA21 and DNA destroys the electrostatic adsorption of DNA/PtNP conjugates and restores the electrocatalytic performance of PtNPs, and the signal is in the "on" state again. Based on this, a new method for detecting miRNA21 was established. It provides a new way for small-molecule sensing and has a wide range of applications in electroanalysis, electrocatalysis, and biosensing.

Zinc Oxide Nanostructured-Based Sensors for Anodic Stripping Voltammetric Determination of Darifenacin

Herein for the first time, the construction and the electroanalytical applications of novel darifenacin (DFC) voltammetric sensors were described. Zinc oxide nanostructures act as a proper redox mediator and exhibit efficient catalytic activity towards the electrooxidation of the DFC molecule. At the optimum measuring conditions, DFC exhibited an irreversible anodic oxidation peak at 0.880 V with an assumed adsorption-reaction mechanism at the electrode surface. Based on the effect of the pH and the scan rate studies, electrooxidation of DFC takes place through the oxidation of the nitrogen atom (N12) in the five-membered ring of the darifenacin molecule with the participation of one electron and one proton in agreement with the molecular orbital calculations. Calibration curves were linear within the DFC concentration ranging from 0.33 to 6.54 × 10−6 mol l−1 with a limit of detection (LOD) and limit of quantification (LOQ) values of 0.08 and 0.23 × 10−6 mol l−1. The proposed sensors exhibited enhanced performance with high measurement reproducibility and prolonged lifetime. The presented voltammetric approach was utilized for precise determination of darifenacin in biological samples and pharmaceutical formulations with acceptable recoveries compared with the traditional spectrophotometric methods.

3D-printed electrochemical platform with multi-purpose carbon black sensing electrodes.

The 3D printing is described of a complete and portable system comprising a batch injection analysis (BIA) cell and an electrochemical platform with eight sensing electrodes. Both BIA and electrochemical cells were printed within 3.4 h using a multimaterial printer equipped with insulating, flexible, and conductive filaments at cost of ca. ~ U$ 1.2 per unit, and their integration was based on a threadable assembling without commercial component requirements. Printed electrodes were exposed to electrochemical/Fenton pre-treatments to improve the sensitivity. Scanning electron microscopy and electrochemical impedance spectroscopy measurements upon printed materials revealed high-fidelity 3D features (90 to 98%) and fast heterogeneous rate constants ((1.5 ± 0.1) × 10−3 cm s−1). Operational parameters of BIA cell were optimized using a redox probe composed of [Fe(CN)6]4−/3− under stirring and the best analytical performance was achieved using a dispensing rate of 9.0 µL s−1 and an injection volume of 2.0 µL. The proof of concept of the printed device for bioanalytical applications was evaluated using adrenaline (ADR) as target analyte and its redox activities were carefully evaluated through different voltammetric techniques upon multiple 3D-printed electrodes. The coupling of BIA system with amperometric detection ensured fast responses with well-defined peak width related to the oxidation of ADR applying a potential of 0.4 V vs Ag. The fully 3D-printed system provided suitable analytical performance in terms of repeatability and reproducibility (RSD ≤ 6%), linear concentration range (5 to 40 µmol L−1; R2 = 0.99), limit of detection (0.61 µmol L−1), and high analytical frequency (494 ± 13 h−1). Lastly, artificial urine samples were spiked with ADR solutions at three different concentration levels and the obtained recovery values ranged from 87 to 118%, thus demonstrating potentiality for biological fluid analysis. Based on the analytical performance, the complete device fully printed through additive manufacturing technology emerges as powerful, inexpensive, and portable tool for electroanalytical applications involving biologically relevant compounds.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-022-05323-4.

A Size-Controlled Graphene Oxide Materials Obtained by One-Step Electrochemical Exfoliation of Carbon Fiber Cloth for Applications to In Situ Gold Nanoparticle Formation and Electrochemical Sensors-A Preliminary Study.

A simple, one-step and facile method has been introduced to prepare fluorescent and electrochemically active carbon nanoparticles with single-size distribution and good long-term stability by electrochemical exfoliation of polyacrylonitrile-based carbon fibers in an alkaline solution-phase condition. The preparation condition was systematically optimized by studying the effect of temperature and electrolytes. It has been found that an electrochemical exfoliation reaction carried out at an applied potential of 2 V vs. Ag/AgCl in a phosphate-ion-containing alkaline solution at a temperature of 40 °C is an ideal condition for the preparation of 14 ± 4 nm-sized carbon nanoparticles. Unlike the literature protocols, there are no filtration and membrane dialysis-based off-line sample pretreatments adopted in this work. The as-prepared carbon nanoparticles were characterized by fluorescence, Raman spectrum, transmission electron microscope, and X-ray photoelectron spectroscopic characterization methods. It was found that the carbon–oxygen functional group rich in graphene–oxide quantum dots (GOQDs) such as carbon nanoparticles were formed in this work. A preliminary study relating to simultaneous electrochemical oxidation and the sensing of uric acid and ascorbic acid with well-resolved peaks was demonstrated as a model system to extend the new carbon material for electroanalytical applications. Furthermore, in situ synthesis of 2 nm-sized gold nanoparticles stabilized by GOQDs was presented. The carbon nanoparticles prepared by the direct method in this work have shown good stability over 6 months when stored at room temperature. The electrochemical exfoliation reaction has been found to be highly reproducible and suitable for bulk synthesis of luminescence-effective carbon nanoparticles to facilitate fundamental studies and practical applications.

Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications

Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.

A metal free nanosensor based on nanocellulose-polypyrrole matrix and single-walled carbon nanotube: Experimental study and electroanalytical application for determination of paracetamol and ciprofloxacin

In the present work, a highly selective and metal-free electrochemical sensor was fabricated from the fusion of nanocellulose and polypyrrole (NNC-PPY), incorporated with single-walled carbon nanotubes (SWCNTs) via drop-casting method for the simultaneous determination of paracetamol (PCM) and ciprofloxacin (CPR). The screen printed electrode (SPE) modified with NNC-PPY/SWCNTs shows outstanding electrocatalytic performance towards the redox reaction of PCM and oxidation of CPR. The nanocomposite was investigated by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and Brunauer-Emmett-Teller (BET) analysis, while the electrochemical performances were investigated by cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). The molecular interactions and binding energy of the prepared NNC-PPY/SWCNTs nanocomposite with PCM and CPR were studied by molecular dynamic simulation (MDs). The fabricated NNC-PPY/SWCNTs/SPE sensor showed dynamic linear range of 0.05–40.0 µM and 1–50 µM for PCM and CPR and a limit of detection (LOD) of 0.072 nM and 0.196 nM, with high sensitivity of 50.341 µA µM−1 cm−2 and 18.610 µA µM−1 cm−2, for PCM and CPR respectively. Furthermore, this fabricated sensor was implemented successfully for the simultaneous determination of PCM and CPR from water samples, biological fluids and pharmaceutical preparations.

Electroanalysis based on Carbon Nanomaterials

This Special Issue illustrates these fast-growing research topics, via selected examples based on either simple or more sophisticated carbon-based nanomaterials used for electroanalytical purposes. It includes 19 original papers and 5 reviews related to recent achievements in the design (e.g. machine learning), synthesis and electroanalytical applications (e.g. enzymatic biosensor, immunoassay, aptasensor, wearable sensor, gas detection, stripping analysis of heavy metal ions) of carbon nanomaterials. We believe this Special Issue throws new light on electroanalysis based on carbon nanomaterials and will advance relevant research. We hope the readers will benefit from this state-of-the-art in such a field.

Recent electroanalytical applications of boron-doped diamond electrodes

This review overviews recent reports on the electroanalytical applications of boron-doped diamond (BDD) electrodes. Because BDD electrodes have excellent features for electroanalysis, such as wide potential window, low background current, electrochemical stability, and fouling resistance, they can be useful for sensitive and stable detection of various substances, including drugs, bio-related substances, metal ions, and organic pollutants. Many articles have reported high-sensitivity detection of real samples, demonstrating that this electrode material is practically applicable. Surface modification of the BDD electrodes using metal nanoparticles, nanocarbons, and polymers can increase the sensitivity of the electrochemical detection. Furthermore, research on the electroanalytical device equipped with BDD electrodes will be expanded by combining peripheral technologies related to the device fabrication.

Enhanced stability of electrochemical performance of few-layer black phosphorus electrodes by noncovalent adsorption of 1,4-diamine-9,10-anthraquinone

In this paper, the novel noncovalent functionalisation strategy of few-layer black phosphorus by 1,4-diamine-9,10-anthraquinone electrode was proposed and studied. The degradation of few-layer black phosphorus under exposure to oxygen and water is a significant obstacle to its use as an electroanalytical electrode. The anthraquinone compound adsorbed at black phosphorus flakes results in improved prevention of the phosphorus surface against degradation and electrode decomposition. Furthermore, a large concentration of amino group present in 1,4-diamine-9,10-anthraquinone enhances the electrochemical performance of electrode revealed by a faster rate of heterogeneous electron transfer observed in cyclic voltammetry studies. The designed electrode exhibits stable redox peaks over 100 cycles with separation between the peaks of 79 ± 2 mV and the formal redox potential reaching 257 ± 3 mV. The differential pulse voltammetry was utilised for the detection of ascorbic acid, revealing a limit of detection equal to 3.29 ppm (18.68 µM) and a limit of quantification of 9.98 ppm (56.66 µM). The linear range of 1–20 ppm was achieved, allowing for the detection of ascorbic acid in real conditions. Thus, anthraquinone-modified few-layer black phosphorus may be an attractive novel electrode material for sensitive electroanalytical applications.

A portable electrochemical platform based on graphene nanosheets by metal intercalation engineering for anticancer drug pemetrexed sensing

Tuning of the electronic and surface properties of the graphene via novel strategy is highly desirable issue for the fabrication of multifunctional materials in potential sensing applications. In this study, we synthesized the extremely pure graphene nanosheets (M−GRNs) by metal intercalation approach in a bulk form, and followed by the fabrication of a portable electrochemical sensing platform prepared on screen-printed carbon electrode (SPCE). The superiority of M−GRNs in terms of the electrocatalytic performance has been confirmed by the comparison with graphene nanosheets synthesized via conventional chemical reduction route. Raman, XPS and TEM techniques were utilized to verify the structure and morphology of the prepared graphene samples. The electrochemical performance of the fabricated M−GRNs/SPCE was evaluated by various voltammetric techniques towards the anticancer agent pemetrexed (PMX) as a model target analyte. The results reveal that M−GRNs/SPCE exhibited an outstanding electrochemical performance with a linear working range of 0.05–2.2 µM (R2=0.9915) and challenging detection limit of 9.7 nM towards the electro-oxidation of PMX. The detection of PMX in human serum samples was successfully analyzed at M−GRNs/SPCE with satisfactory recoveries. The possible interaction mechanism of PMX with double-stranded DNA on M−GRNs/SPCE has been also discussed. This proposed strategy could be an alternative to produce the sensitive graphene-based platforms for electroanalytical applications in clinical samples.

Electrochemical Impedance Spectroscopy in the Characterisation and Application of Modified Electrodes for Electrochemical Sensors and Biosensors.

Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.

Dual electroactive AgM (M=Ru, Pt) NPs for double electroanalysis of HER2 and EpCAM

Parallel multiple detections of tumor markers is of significant for the efficient and accurate early monitoring of related cancers. Electrochemical aptasensors possess excellent selectivity and sensitive quantitative detection while maintaining multiple detection ability. The study of high and different electrochemical beacons is urgent to achieve multiple-level parallel detection. In this work, electroactive AgRu NPs and AgPt NPs were explored to exhibit electrooxidation peaks at 0.8 V and − 0.7 V, respectively. Plasmonic AgRu NPs and AgPt NPs harvested light energy and exhibited amplified electrooxidation activity under local surface plasmon resonance (LSPR) excitation. Plasmon-enhanced electrooxidation principle was proposed for AgM (M=Ru, Pt) NPs owing to the distinct imaginary part of dielectric constants between Ag and platinum group metals (PGM). The strong and non-interference electrooxidation peaks at 0.8 V and − 0.7 V enabled AgRu NPs and AgPt NPs to be different electroactive beacons for the sensitive and reliable quantitative dual detection of human epidermal growth factor receptor-2 (HER2) and epithelial cell adhesion molecule (EpCAM). The LODs were 0.3 pg mL−1 (7.5 amol mL−1) for EpCAM and 0.6 pg mL−1 (3.2 amol mL−1) for HER2. The proposed plasmon-promoted electrooxidation principle provides a novel route for the design of multiple electroactive plasmonic metal-PGM composite electrochemical beacons for simultaneous electroanalysis applications.

Development and Characterization of Novel Flow Injection, Thin-Layer, and Batch Cells for Electroanalytical Applications Using Screen-Printed Electrodes.

In the present paper, the design, fabrication, and analytical applications of three novel cells for flow injection, thin-layer, and batch electrochemical measurements using screen-printed electrode chips (SPECs) are described. Each cell consisted of an acrylic base and a transparent acrylic cover. The essential construction feature of each cell base was a cavity to accommodate the SPEC, whereas the construction features of the clear acrylic cover determined the cell shape and its function. The presented cells offered several common advantages, which include (i) convenient electrical connection of the SPEC to any potentiostat without the need for special cables, (ii) the SPEC was completely contained within the cell body, which eliminated the risk of its breakage, (iii) suitable for use with a large number of commercially available SPECs, and (iv) excellent SPEC sealing. The flow cell offered additional advantages of convenient customization of the cell dead volume and convenient visual inspection of the surface and the vicinity of SPEs. The presented thin-layer cell is the first report on a dedicated cell which realized a near-ideal thin-layer steady-state voltammetry using SPECs. The universal batch cell (UBC) offered extreme versatility and proved suitable for all batch applications in sample volumes ranging from 25 μL to 40 mL with an optional controlled temperature and atmosphere. Moreover, a novel way to achieve stirred-solution chronoamperometry and hydrodynamic voltammetry using SPECs (with superior signal-to-noise ratios) using the UBC is described. Electrochemical measurements to demonstrate the merits and the applicability of all cells are also presented.

Cost-Effective 3D-Printed-Enabled Fluidic Electrochemical Sensing Platform for Quantitative Electroanalytical Applications

3D-printing is an open access manufacturing technology that facilitates prototyping of economical devices for scientific purposes. Coupled with the emergence of commercially available cost-efficient screen-printed electrodes (SPEs), 3D-printing has enabled the fabrication of cost-effective fluidic sensing platforms with removable/disposable electrodes. However, quantitative electrochemical detection of analytes in 3D-printed flow-cells integrated with SPEs is yet to be achieved. In this work, the successful implementation of a cost-effective 3D-printed-enabled fluidic electrochemical sensing platform (3DP-FESP) for the quantitative detection of dopamine (DA) in the presence of uric acid (UA), and ascorbic acid (AA) is demonstrated. The 3DP-FESP consists of a reversibly sealed 3D-printed flow-cell integrated with removable SPEs electrochemically activated to increase sensitivity towards DA. The flow-cell was fabricated through fused deposition modeling (FDM) 3D-printing and Embedded SCAffold RemovinG Open Technology (ESCARGOT). The 3DP-FESP was characterized to determine its optimal flow rate and ensure enhancement of the quantitative performance of the SPEs under flow conditions. As a result, the performance of our 3DP-FESP (flow conditions) was better than only activated SPEs (stagnant conditions) for DA detection in the presence of interferents with LODs of 0.05 μM and 0.16 μM, respectively. This demonstrates the potential of our cost-effective 3DP-FESP for enhanced quantitative electroanalytical applications.

AuPt NPs with enhanced electrochemical oxidization activity for ratiometric electrochemical aptasensor

Strong and stable electrochemical beacons are critical for the achievement of sensitive and reliable electroanalysis applications. In this work, the electrochemical oxidation performance of AuPt NPs was studied and firstly found to be largely enhanced under light illumination. Plasmonic AuPt NPs collected light energy after local surface plasmon resonance (LSPR) excitation and generated much more holes to participate in the electrochemical oxidation process of Pt0 in AuPt NPs. AuPt NPs with the electrochemical oxidation peak at around −0.7 V were utilized as detection probes for the fabrication of ratiometric electrochemical aptasensor, by introducing Co-MOF/Fe3O4/Ag nanosheets (NSs) with the electrochemical oxidation peak at 0.1 V as reference beacons. The aptamers of epithelial cell adhesion molecule (EpCAM) modified AuPt NPs were assembled with Co-MOF/Fe3O4/Ag NSs, which generated strong detection and reference signals at −0.7 V and 0.1 V, respectively. The high affinity between EpCAM and aptamers induced the separation of AuPt NPs from Co-MOF/Fe3O4/Ag NSs, resulting in the decrease of detection signal at −0.7 V and unchanged reference signal at 0.1 V. A ratiometric electrochemical aptasensor was achieved for the sensitive and reliable quantification of EpCAM in the range from 100 pg/mL to 100 ng/mL. The limit of detection (LOD) was calculated to be 13.8 pg/mL for EpCAM. Plasmon-driven electrochemical oxidation enhancement principle provides the possibility for the design and fabrication of more strong and anti-interference electroactive plasmonic metal-Pt composite nanostructures for the electroanalysis applications.

Laser‐induced Graphene in Facts, Numbers, and Notes in View of Electroanalytical Applications: A Review

AbstractIn this review, laser‐induced graphene (LIG) ‐based electrodes are discussed by covering such essential areas, as a characterization of LIG material properties necessary for electroanalysis, including data on LIG sheet resistance, wettability, spatial resolution, electrochemical characteristics, as well as correlations of “process” ‐ “properties” ‐ “electroanalytical characteristics”of LIG‐electrodes. Moreover, typical and innovative LIG‐based electrodes designs for electroanalytical applications, including combined multi‐analyte multimodal wearable sensors, interdigitated electrodes, are shown. The essential data related to LIG in electroanalysis are summarized in tables. The authors also discussed recent LIG‐based electroanalytical applications. Close attention has been paid to LIG glucose sensors and biosensors.

Au25 Nanoclusters Exhibit Superhigh Catalytic Activity in Electrochemical Detection of As(III).

An atomic-level Au nanocluster, as an excellent photocatalyst, is generally not considered as an efficient electrocatalyst due to its poor stability. Herein, a method is proposed to stabilize abundant Au25 on Fe2O3 nanoplates (Au25/OV-Fe2O3) successfully with oxygen vacancies (OV) created. Au25/OV-Fe2O3 shows superhigh catalysis in the electrochemical reduction toward As(III). The record-breaking sensitivity (161.42 μA ppb-1) is two orders of magnitude higher than currently reported, where an ultratrace limit of detection (9 ppt) is obtained, suggesting promising applications in the analysis of organic and bioactive substances. The stability of Au25 is attributed to the Au-Fe bond formed after loading Au25 nanoclusters on Fe2O3 nanoplates through "electron compensation" and bond length (Au-S) shortening. Moreover, the ligand S atoms in Au25 nanoclusters significantly contribute to the reduction of As(III). The fantastic stability and superior catalytic ability of Au25/OV-Fe2O3 provide guidelines to stabilize Au nanoclusters on metal oxides, indicating their potential electroanalytical applications.