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The orientation and rearrangement of water on a gold electrode significantly influences its physicochemical heterogeneous performance. Despite numerous experimental and theoretical studies aimed at uncovering the structural characteristics of interfacial water, the orientational behavior resulting from electrode-induced rearrangements remains a subject of ongoing debate. Here, we employed molecular dynamics simulations to investigate the adaptive structure and dynamics properties of interfacial water on Au(111) and Au(100) surfaces by considering a polarizable model for Au atoms in comparison with the non-polarizable model. Compared to the nonpolarizable systems, the polarization effect can enhance the interaction between water molecules and the gold surface. Unexpectedly, the rotational dynamics directly associated with the orientational behavior of water adjacent to the gold surface is accelerated, thereby reducing the hydrogen bond lifetime. The underlying mechanism for this anomalous phenomenon originates from the polarization effect, which induces the attraction of the positive hydrogen atoms to the surface by the negative image charge. This leads to a change in orientation that disrupts the hydrogen bonds in the first water layer and subsequently accelerates reorientation dynamics of water molecules adjacent to the gold surface. These results shed light on the intricate interplay between polarization effects and water molecule dynamics on metal surfaces, establishing the foundation for the rational regulation of the orientation of interfacial water. [ABSTRACT FROM AUTHOR]

Non-equilibrium Green's function (NEGF) and density functional theory (DFT) calculations are used to explore the impact of doping on the electron transport properties in a single tetracene molecule linked to gold electrodes using isocyanide anchoring groups. Boron (B) and Nitrogen (N) atoms are used for doping and co-doping (BN) of the carbon atoms placed at the edge of the tetracene molecule. It was found that the chemical doping of tetracene molecules mainly impacts the rectification trends compared to non-doped molecules. Our findings indicate that B doping significantly improves the rectification ratio compared to other dopants because of a greater difference between the current values under positive and negative biases as a result of asymmetric I-V characteristics. These inferences have also been assessed in terms of MPSH and transmission spectra. In addition, novel characteristic of negative differential resistance (NDR) is attained in single dopant molecular junctions. [ABSTRACT FROM AUTHOR]

The significance of easily detecting rare earth elements (REEs) has increased due to the growing demand for REEs. Addressing this need, we present an innovative electrochemical biosensor, focusing on cerium as a model REE. This biosensor utilizes a modified EF‐hand loop peptide sequence, incorporating cysteine for covalent attachment to a gold working electrode and tyrosine as an electrochemically active amino acid. The sensor was designed such that binding to cerium induces a conformational change in the peptide, affecting tyrosine's proximity to the electrode surface, modulating the current. A calibration curve was generated from cyclic voltammetry current peaks at ~0.55–0.65 V versus a silver pseudo‐reference electrode, with cerium concentrations ranging from 0 to 67 μM in artificial urine. The sensor exhibited a biologically relevant limit of detection of 35 μM and a sensitivity of −0.0024 ± 0.002 (μA μM)−1. These findings offer insights into designing peptide sequences for electrochemical biosensing. [ABSTRACT FROM AUTHOR]

The increasing demand for eco-friendly fuel options, driven by a rising petition for cleaner energy and heightened awareness of environmental issues, has captured global attention. In the present work, platinum and gold electrodes were modified with a cobalt 2,2’-[1,4-phenylenebis(methanylylidene-azanylylidene)]dibenzoic acid metal-organic framework (Co-MOF). The catalytic effectiveness of the MOF was investigated. Surface morphology analysis was carried out using scanning electron microscopy, while X-ray diffraction and FT-IR spectroscopy were employed to characterize crystallinity and identify functional groups. Electrochemical studies included cyclic voltammetry, electrochemical impedance spectroscopy, Tafel plot analysis, and chronoamperometry. The platinum electrode, after modification, exhibited the highest current value (7.39 mA cm−2) in the presence of 0.5 M methanol in 1 M NaOH, with a Tafel slope of 138 mV dec−1. Similarly, the modified gold electrode demonstrated its highest current value (7.92 mA cm−2) at 2 M methanol in 1 M NaOH, with a Tafel slope of 190 mV dec−1. [ABSTRACT FROM AUTHOR]

In this study, multiple particle binding-liposomes (MPB-Lips), encapsulating the luminophore tris(2′,2-bipyridyl)ruthenium (II) complex ([Ru(bpy)3]2+), were developed as an electrochemiluminescence (ECL) signal amplifier and were applied to detect the model analyte streptavidin (SA) using the indirect competitive ECL method. The MPB-Lips were prepared by mixing various ratios of two different liposomes—one containing a phospholipid with a primary amine group and a biotinyl group (BIO/NH2-Lip) and one containing a phospholipid with an N-hydroxysuccinimide group (NHS-Lip) to allow binding between particles via amide bonds. Quartz crystal microbalance analysis using SA-modified gold-coated quartz crystals showed that the frequency shift values of MPB-Lips gradually decreased in the order BIO/NH2-Lip:NHS-Lip = 1:0 < 1:1 < 1:3 < 1:5. This indicated that MPB-Lips were successfully formed. The indirect competitive ECL method using SA-modified gold electrodes showed that the 1:5-Lip system had greater sensitivity than the 1:0-Lip system—the limit of detection and quantification values for the systems were 1.84 and 6.30 μg mL−1 for 1:0-Lip, and 1.20 and 1.74 μg mL−1 for 1:5-Lip. Finally, the recovery of SA spiked in fetal bovine serum samples using the 1:5-Lip system showed good accuracy and precision with a recovery rate of 83–106% and relative standard deviation of 4–14%. Our study demonstrated that the MPB-Lips system was an effective and useful ECL amplifier and the ECL method using MPB-Lips could be applied to detect an analyte in a real sample. [ABSTRACT FROM AUTHOR]

Sulfuric acid is commonly used to electrochemically activate gold electrodes in a variety of electrochemical applications. This work provides the first evaluations of the electrochemical behaviors and a 3D image of an activated screen-printed gold electrode (SPGE, purchased commercially) through electrochemical and imaging analyses. The activated SPGE surface appears rougher than the unactivated SPGE surface when viewed through microtopography images using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Nevertheless, the roughened microscopy structure does not exhibit any substantial changes in roughness factor for the activated SPGE, as indicated by capacitive current analyses. The significant improvement in electrochemical responsiveness of the activated SPGE is mainly attributed to the presence of surface pores created in the microscopic structure as a result of gold oxide layer formation. The presence of surface pores on the activated surface has significantly improved its conductivity by 10-fold. As a result, electron transfer kinetics and mass transports of the activated SPGE are greatly improved. The results presented in this work indicate that the surface of the activated SPGE greatly increased its intrinsic surface pores, and conductivity of the electrode surface and uncovered the electrocatalytic active sites. This significantly improves the activated SPGE's performance in electrochemical applications such as oxygen reduction reaction (ORR). An activated SPGE considerably enhanced limiting current density as well as ∼172 mV versus Ag shifted onset potential to more positive potentials compared to unactivated SPGE. [ABSTRACT FROM AUTHOR]

Lead ions (Pb2+) are classified as highly toxic heavy metals that pose substantial threats to both human health and environmental integrity. Consequently, the sensitive detection of Pb2+, particularly at low concentrations, is imperative for the purposes of environmental surveillance and safeguarding public health. Here, we introduce a Co/Pt/Si Schottky heterostructure for a rapid, portable Pb2+ detection sensor. One electrode of the heterojunction serves as a Pb2+ probe, and sensor processing circuits are integrated. The Co/Pt thin films were deposited via magnetron sputtering on a Si(100) substrate, followed by heterojunction fabrication using semiconductor process technology. The sensor is functionalized with a glutathione‐modified gold electrode, leveraging the sulfur‐donor properties of cysteine in glutathione and the electron‐acceptor behavior of Pb2+. This interaction modulates the surface potential of the gold electrode, altering the current‐voltage rectification of the Co/Pt/Si heterojunction. A two‐terminal configuration enables current signal readout without reference electrodes. The sensor demonstrates a linear response to Pb2+ concentrations ranging from 1×10−8 to 1×10−3 mol/L, with high selectivity attributed to the affinity of glutathione for Pb2+. The key benefits are the simplicity of its fabrication process and its portability, which are enhanced by the integration of measurement circuitry. This makes the sensor a promising candidate for rapid, on‐site detection of heavy metal ions in applications related to health and environmental monitoring. [ABSTRACT FROM AUTHOR]

Electrode fabrication in microfluidic devices is often avoided due to the smaller footprint of the platform, associated complexity in the process, and absence of a well-established method. In this article a glass microchip with chemically modified and vapor deposited gold internal electrode was fabricated and used for biomolecule immobilization and electrochemical applications. The silanol (-OH) on glass surface of the microdevice was modified with (3-mercaptopropyl)trimethoxysilane prior to gold deposition to achieve a strong attachment of the metal film using the gold-thiol binding. The practical utility of the microdevice with gold surface was demonstrated by performing quantitative enzyme linked immunosorbent assay (ELISA) of human interferon gamma (IFN-γ) antigen, yielding a limit of detection (LOD) of 0.15 pg/mL compared to 4 pg/mL in the microplate assay. Additionally, the functionality of the internal electrode was established by performing cyclic voltammetry (CV) and linear sweep voltammetry (LSV) of potassium ferricyanide (III) in potassium chloride (KCl) solution using the proposed gold patterned electrode in the microchip, offering limits of detection of 0.14 and 0.11 mM for CV and LSV respectively. Both the ELISA and electrochemical assays were validated by generating calibration curves and using a control sample for the electroanalytical sensing applications. The measurements yielded experimental results that agreed with control concentration with 7% relative standard deviation (RSD). The promising reproducibility of the electrode in fabrication with no/minimum failure rate and its outstanding performance in immunosensor applications as well as an electron exchange surface makes our technique of gold electrode fabrication in microchips a state of the art. [ABSTRACT FROM AUTHOR]

This paper presents a study on the impedance spectroscopy methods applied to 2-electrode and 3-electrode biosensors. While 3-electrode electrochemical biosensors have been extensively studied and applied in various applications, the 2-electrode configuration of electrochemical biosensors still lacks comprehensive investigation for real-world applications. In particular, the miniaturization of the 3-electrode configuration for integration into microfluidic devices has been explored due to the relatively limited number of previous studies. A commercial screen-printed gold electrode was employed to develop immunosensors for bovine serum albumin (BSA) detection. The comparisons were performed on non-Faradaic and Faradic immunosensors corresponding to 2-electrode and 3-electrode configurations through impedance measurements. The results show the performance of both types of sensors in detecting BSA protein. While the 2-electrode configuration-based sensor can detect the BSA protein with a sensitivity of 12 Ω/µM, the 3-electrode configuration-based sensor shows superior results with a sensitivity of 7.2 kΩ/µM. Besides, the results also indicate that the 2-electrode configuration-based sensor can easily be miniaturized to integrate into a microfluidic channel to develop lab-on-a-chip systems. Although the 3-electrode configuration demonstrates advancements compared to the 2-electrode configuration, the 2-electrode system based on non-Faradaic processes still shows high potential for future applications. [ABSTRACT FROM AUTHOR]

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2)‐ and magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2)‐based electrolytes, each with and without MgCl2, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM−D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)4]2‐based electrolytes, highly efficient and interphase‐free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so‐called initial conditioning process. With the more reactive Mg(TFSI)2‐based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode. [ABSTRACT FROM AUTHOR]

This study presents the electrochemical reduction of graphene oxide (GO) to reduced graphene oxide (rGO) directly onto flexible interdigitated gold electrodes and its application as a strain sensor. GO reduction is achieved using cyclic voltammetry (CV). Remarkably, only a single CV cycle transformed GO into rGO to obtain low‐resistance (≈100 Ω) devices. The reduction of GO is confirmed using Raman spectroscopy and electrical measurements. rGO on flexible interdigitated gold electrodes exhibits graphene‐like characteristics when used as electrolyte‐gated field‐effect transistors. The fabricated devices display a gauge factor (GF) of ≈3.7 in the 0–794 με range. This value represents a substantial improvement, ≈60% higher than traditional metallic strain sensors, which have a GF of ≈2.1. Most importantly, the rGO strain sensor exhibits fast response (1.1 s) and recovery (0.92 s) times. The rGO sensor is mounted on a clamp with an adjustable diameter, which reveals exceptional flexibility and bendability without damage or degradation. These results highlight the potential of rGO for advancing strain‐sensing applications, offering promising opportunities for the future of this technology. [ABSTRACT FROM AUTHOR]

Microorganisms capable of direct or mediated extracellular electron transfer (EET) have garnered significant attention for their various biotechnological applications, such as bioremediation, metal recovery, wastewater treatment, energy generation in microbial fuel cells, and microbial or enzymatic electrosynthesis. One microorganism of particular interest is the organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1, known for its ability to reductively dehalogenate toxic and persistent halogenated organic compounds through organohalide respiration (OHR), using halogenated organics as terminal electron acceptors. A membrane-bound OHR protein complex couples electron transfer to proton translocation across the membrane, generating a proton motive force, which enables metabolism and proliferation. In this study we show that the halogenated compounds can be replaced with redox mediators that can putatively shuttle electrons between the OHR complex and the anode, coupling D. mccartyi cells to an electrode via mediated EET. We identified cobalt-containing metal complexes, referred to as cobalt chelates, as promising mediators using a photometric high throughput methyl viologen-based enzyme activity assay. Through various biochemical approaches, we show that cobalt chelates are specifically reduced by CBDB1 cells, putatively by the reductive dehalogenase subunit (RdhA) of the OHR complex. Using cyclic voltammetry, we also demonstrate that cobalt chelates exchange electrons with a gold electrode, making them promising candidates for bioelectrochemical cultivation. Furthermore, using the AlphaFold 2-calculated RdhA structure and molecular docking, we found that one of the identified cobalt chelates exhibits favorable binding to RdhA, with a binding energy of approximately −28 kJ mol−1. Taken together, our results indicate that bioelectrochemical cultivation of D. mccartyi with cobalt chelates as anode mediators, instead of toxic halogenated compounds, is feasible, which opens new perspectives for bioremediation and other biotechnological applications of strain CBDB1. [ABSTRACT FROM AUTHOR]

In this study, the effect of halide anions on the selectivity of the CO2 reduction reaction to CO was investigated in choline‐based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO2RR was studied using silver (Ag) and gold (Au) electrodes in a compact H‐cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride‐containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CO2RR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl− ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion‐induced surface restructuring of Ag and Au electrodes during CO2RR, and its consequences on the reduction performance on such surfaces in non‐aqueous electrolytes. [ABSTRACT FROM AUTHOR]

Label-free electrochemical biosensors show great potential for the development of point-of-care devices (POCDs) for environmental and clinical applications. These sensors operate with shorter analysis times and are more economic than the labelled ones. Here, four completely label-free biosensors without electron transfer mediators were developed for hepatitis B virus (HBV) detection. The approach consisted in (i) the modification of gold surfaces with cysteamine (CT) or cysteine (CS) linkers, (ii) the subsequent antibody (Ab) immobilization, either directly by hydrogen bonding (HB) interactions or by covalent bonds (CB) using additional reagents, and (iii) measuring the biosensor response by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The electrode surfaces at each stage of the modification process were characterised by X-ray photo-electron spectroscopy (XPS) and atomic force microscopy (AFM). The combination of Ab immobilization by HB with the DPV analysis displayed improved repeatability, lower interference to serum matrix and similar limits of detection and quantification than the traditional biosensors that immobilize the Ab via CB and use EIS as readout technique. The Ab immobilization by HB is shown as a simple, efficient and low-cost alternative to CB ones, while DPV was faster and showed better performance than EIS. The CT-HB biosensor displayed the lowest limits of detection and quantification of 0.14 and 0.46 ng/mL, respectively, a 0.46–12.5 ng/mL linear analytical range, and 100% of recovery for 1/10 human serum media during HBV surface antigen detection by DPV. Even, it preserved the initial sensing capability after 7 days of its fabrication. [ABSTRACT FROM AUTHOR]

A low-cost, lab-made polytetrafluoroethylene micro-cell, equipped with three electrodes, wasd eveloped for the impedimetric detection of SARS-CoV-2. The gold working electrode was modified with a double-ended thiolated poly-adenine probe, which was conjugated with magnetic Fe₃O₄@Au nanoparticles (Fe3O4@Au-(S-polyA-S)-Au). After the loop-mediated isothermal amplification (LAMP) of viral RNA, the single-guide RNA (sgRNA), specifically bound to the SARS-CoV-2 target sequence, activates Cas12a. Cas12a then cleaved the immobilized probe. As a result, the magnetic Fe3O4@Au nanoparticles were released and adsorbed onto the gold electrode surface, using an external magnet. This process increased the physical surface area of the gold electrode, facilitating redox ion ([FeIII/II(CN)6]3−/4−) electron transfer. The decrease in the charge transfer resistance was utilized for SARS-CoV-2 detection. Our LAMP-CRISPR/Cas12a-based impedimetric biosensor, powered by Fe3O4@Au-(S-polyA-S)-Au, demonstrated impressive capabilities, including a remarkable detection limit of 0.8 aM (0.48 copies/µL) and a linear range of 0.01 to 36.06 fM. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is a significant opportunistic pathogen highly prevalent in the environment, requiring early detection methods to prevent infections in vulnerable individuals. The most specific aptamer for P. aeruginosa, F23, has been used for the development of various assays and sensors for early diagnosis and monitoring. In this study, a novel F23-based electrochemical aptasensor was designed using disposal gold screen-printed electrodes (Au-SPEs) with high reproducibility. Methylene blue (MB) was used as an exogenous indicator, which significantly amplified the electrochemical signal and improved the sensitivity of detection. The aptasensor explored a limit of detection (LOD) of 8 CFU·mL−1 and high selectivity for P. aeruginosa over other interfering bacteria. Furthermore, it showed potential to detect P. aeruginosa in tap water samples, offering a point-of-care tool for rapidly controlling the growth of this bacterium in various applications. [ABSTRACT FROM AUTHOR]

One‐dimensional scanning optical beam‐induced current (OBIC) measurements have been carried out on polymer bulk heterojunction (BHJ) photovoltaic cells with a planar, or lateral configuration. The planar P3HT:PCBM cells have parallel aluminum or gold electrodes that are 390 to 560 micrometers apart. When a focused laser beam is scanned across the electrode gap, photocurrent or photovoltage is recorded as a function of beam position along with the transmission of the excitation beam. Despite the large electrode gap size, cells with symmetric Al/Al electrodes exhibit significant photocurrent and photovoltage which are the highest at the electrode interfaces and null at the cell center. The OBIC in these large planar polymer BHJ cells is attributed to the metal/BHJ blend Schottky junction. The larger Schottky barrier of the Al/BHJ junction gives rise to a stronger OBIC response than the Au/BHJ junction. The photocurrent and photovoltage always have opposite signs and are antisymmetric about the cell center. In asymmetric Al/Au cells, the electrode work function difference contributes an additional built‐in field/potential drop and significantly modifies the photocurrent and photovoltage profiles. The depletion width of the Al/BHJ Schottky junction is 110–120 μm, while the minority electron diffusion length is determined to be 43.8 μm. [ABSTRACT FROM AUTHOR]

The electrochemical performance of gold electrode in sulfuric acid was studied with addition of different concentrations of dissolved fullerenol-d with C60(OH)24 chemical formula. Based on the cyclic voltammetry data, the conclusion of surface complexation of Au(III) with fullerenol was made. The scheme was suggested to describe the electrode process, based on catalysis of anodic Au dissolution by fullerenol molecules. The technique was suggested to detect fullerenol-d (C60(OH)24) in concentration range from 2.6·10–9 M to 2.0·10–7 M by means of cyclic voltammetry of gold in aqueous sulfuric acid solution. [ABSTRACT FROM AUTHOR]

The quest for stretchable properties is at the forefront of research dedicated to on‐skin light–emitting devices. Inspired by the natural wonders of bioluminescence, electrochemiluminescent devices (ECLDs) are distinguished by straightforward design and reduced operating voltage, marking a departure from traditional current‐driven electroluminescent devices (ACELDs). The primary challenge of fully‐stretchable ECLDs lies in crafting electrodes that simultaneously satisfy the demands for conductivity, transparency, stretchability, oxidation resistance, and interface stability. This research introduces a groundbreaking wrinkled polymer‐gold composite electrode. It extends to 50% stretchability, offers outstanding conductivity at 10 Ω sq−1, achieves transparency above 60%, and withstands over 10 000 stretching cycles. Employing this material, alongside stretchable electrospinning fiber luminescent layers, enabled the creation of fully‐stretchable ECLDs. These devices not only shine brightly at 30 Cd m−2 but also retain more than 90% of luminosity when stretched up to 50%. Furthermore, this work has engineered stretchable devices featuring singular patterns and multi‐dot arrays. They exhibit consistent luminescent output under bending, twisting, and stretching when applied to skin. These findings not only highlight the potential of polymer‐gold composite electrodes in overcoming challenges faced by stretchable electronic devices but also provide new ideas for wearable technology that seamlessly integrates with human body. [ABSTRACT FROM AUTHOR]

Sunset Yellow (SY) is an azo dye used in various food and pharmaceutical industries that deserves special attention because of its allergic and carcinogenic properties. Recently, electrochemical techniques have come to the spotlight because of their high sensitivity, simplicity and rapidity as compared to other techniques. In this work, we have developed a cost‐effective and stable electrochemical sensor by a simple method using Vitamin B12‐derived cobalt oxide coupled with g‐C3N4 (V12‐CoO/gCN) modified Au electrode. The composite prepared for the sensor was characterized using techniques such as FTIR, Powder XRD, SEM analysis, EDAX, and mapping. For electrochemical sensing of the dye Sunset Yellow, CV, DPV, and LSV techniques have been used, out of which DPV shows a better detection limit of 1.39 nM followed by LSV and CV that displayed detection limits of 3.3 nM and 4.14 nM respectively. When 5 real samples obtained from the local market are analyzed using the DPV technique, the detection limit is obtained in the range between 2.1 nM and 6.9 nM. This method leads to the development of an electrochemical sensor for the detection of Sunset Yellow to get a lower detection limit that can be used in food toxicology and related fields. [ABSTRACT FROM AUTHOR]

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The current study develops the first and novel gold nanoparticle‐ionic liquid nanostructure modified microbial biosensor based on Pleurotus ostreatus for the sensitive determination of Bisphenol A. In the construction of the microbial biosensor, lyophilized P.ostreatus cells were modified with ionic liquid‐cysteamine mixture on a gold electrode which was modified with 1,6‐hexanedithiol and gold nanoparticle. The measurement principle of the biosensor is based on the detection of changes in current in a phosphate buffer system (pH 7.5, 50 mM and containing 5.0 mM K3[Fe(CN)6]) in the potential range of −0.2 to +0.6 V depending on the BPA concentration. In the optimization studies of the microbial biosensor; the most suitable ionic liquid‐cysteamin ratio was 1 : 2 (v/v) and the incubation time of 1,6‐hexanedithiol on the gold electrode was 6 hours. Optimum working conditions were determined to be pH:7.5, 100 mM potassium phosphate buffer, and 35°C. In the characterization studies of the microbial biosensor, parameters such as linearity, interference effects of some substances on the microbial biosensor responses, repeatability, reproducibility and storage stability of the microbial biosensor were determined. The linear range of the biosensor was obtained 10–250 μM. Limit of detection was determined to be 1.57 μM and the response time was obtained 20 seconds. Real sample analysis was carried out by water samples that kept in plastic bottles for 6 months by using both the microbial biosensor and HPLC method. [ABSTRACT FROM AUTHOR]

By means of the first-principles method, the bias effect on the magnetism of polyacene (n-acene) connected to gold electrodes is investigated. A magnetic to nonmagnetic transition for the polyacene (n > 6) is observed when the bias exceeds a critical value. The mechanism is explored as the bias-induced variation of electronic localization, which leads to the exchange of dominant mechanism for molecular magnetism from Columbic interaction between electrons to electron hopping rate. A significant enhancement of the differential conductance and suppression of current spin polarization for the molecular device are also obtained accompanied by the transition of molecular magnetism. This work proposes a feasible way to manipulate the magnetism of polyacene via electric method and reveals the relation between molecular magnetism and its conductance. [ABSTRACT FROM AUTHOR]

The formation of an electric double‐layer (EDL) is an important phenomenon for many research areas, including energy storage technology. Although EDL is well‐known in electrochemistry, most of the studies involve the characterization of liquid electrolyte/electrode interfaces, and only a limited number of studies in solid‐solid contacts, such as solid electrolyte/electrode interface are available. This paper employed electrochemical impedance spectroscopy (EIS) to systematically investigate the influence of experimental factors in the interfacial capacitance arising from the electrode polarization in a lithium disilicate glass/gold electrode interface. It analyzed the influence of a.c. input voltage amplitude, samples' roughness (mechanical and chemomechanical polishing) and thickness, range of applied frequency and temperature, and the number of impedance cycles. In short, it was found that an input voltage range of 15–60 mV is indicated to minimize potential electrochemical processes during electrode polarization, where the data is reproducible from the second measurement cycle onward. Smoother surfaces closely approximated ideal electrode spike behavior, with surface treatment exhibiting influence on interfacial capacitance values. Moreover, as expected, we observed an increase in relative permittivity values with increasing thickness, accompanied by decreased capacitance values. Finally, by employing optimal experimental conditions and analyzing the inflection frequency (finflection${{f}_{inflection}}$) of the ε′$\varepsilon ^{\prime}$ versus log(f$f$) curve, we determined that the ratio between effective charge carriers (ne${{n}_e}$) and the total number of charge carriers (nt${{n}_t}$) nent$\frac{{{{n}_e}}}{{{{n}_t}}}$ falls within the range of 5–12% between 130°C and 280°C. [ABSTRACT FROM AUTHOR]

In this research, we describe the first aptasensor for the detection of the Rift Valley Fever virus (RVFV). The process involved the selection of aptamers through the systematic evolution of ligands by the exponential enrichment (SELEX) technique. After 12 rounds of selection, 6 aptamers were selected and the corresponding binding affinities were assessed using fluorescence binding assays, revealing dissociation constants ranging from 15.45 to 40.98 nM. Notably, among the aptamers, RV2 and RV3 exhibited the highest binding affinities toward RVFV, with dissociation constants of 15.45 and 18.62 nM, respectively. Thiol-modified aptamers were subsequently immobilized onto screen-printed gold electrodes, facilitating the label-free detection of RVFV through square wave voltammetry. The voltammetric aptasensor demonstrated an excellent sensitivity, with a detection limit of 0.015 ng/mL. In addition, cross-reactivity assessments were conducted, where negligible response was obtained when the aptasensor was exposed to non-specific proteins. [ABSTRACT FROM AUTHOR]

The electrochemical deposition of iron hexacyanoruthenate (Fe−HCR) on gold electrodes was studied in electrolytes prepared with light and heavy water. Cyclic voltammetry of the material during preparation and after transfer to a precursor‐free solution exhibits two reductions peaks in H2O‐based electrolytes but only one reduction peak in D2O‐based electrolytes. The voltammetric behavior changes reversibly upon transfer of the material between D2O‐based and H2O‐based 1 mol L−1 KCl solutions. No clear structural differences between samples prepared in D2O and H2O were detected by means of X‐ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection absorption spectroscopy (PM IRRAS). We noted a relatively slow exchange of coordinated water and a fast exchange of zeolitic water. Using voltammetric experiments we could rule out simple effects of solution conductivity for K+, participation of H+/D+ in the charge compensation and surface effects on the observed dependence of the peak splitting on the isotopic composition of the solvent. The most likely reason for the observed behavior is the different structure of the H‐bonded water network of coordinated H2O and zeolitic H2O/D2O which is supported by the PM IRRAS data. [ABSTRACT FROM AUTHOR]

In this study, we explore the efficacy of gold (Au) as a selective electrocatalyst for the reduction of nitrate to hydroxylamine, a valuable nitrogen-based chemical, while also evaluating the by-product formation of ammonia. We systematically optimized various experimental parameters including nitrate concentration, pH, and applied potential. We found that at an applied potential of −0.7 V vs. RHE in 0.1 M HNO3, Au achieves a 230.1 ± 19 μmol NH2OH h−1 cm−2 yield, with a 34.2 ± 2.8% faradaic efficiency. This study underscores the potential of Au as an efficient and selective electrocatalyst for generating value-added nitrogen products through an electrochemical pathway. [ABSTRACT FROM AUTHOR]

In this work, a simple and cost-effective integrated electrode system consisting of aptamermodified inkjet-printed (IJP) gold working electrode and unmodified IJP gold as counter electrode (both printed on polyethylene naphthalate substrate) has been developed for low-cost detection of cadmium (II) ion in water. The technique uses a Cd2+ (Cd-4) aptamer, a singlestranded DNA with 31 nucleotides trapped on the working electrode using the self-assembly monolayer (SAM) technique. The electrochemical detection of Cd2+ is based on the change in redox peaks of [Fe(CN)6]3-/4- as a redox probe in cyclic voltammetry. The change in peak current is caused by a difference in electron transfer rate before and after binding the aptamer with the target ion (Cd2+). The electrochemical properties were further characterized using electrochemical impedance spectroscopy under optimal conditions, revealing changes in the charge transfer resistance upon binding the Cd2+ ion with the aptamer on gold. Detection by CV, the anodic peak currents (Ipa) varied linearly with Cd2+ concentration from 0.1-10 ng/mL. Saturation of the working electrode's active surface area was achieved with 10 ng/mL. The regression coefficient was 0.9977, whereas for the Cd2+ aptasensor, the limit of detection (LOD) was 0.5 ng/mL. The developed electrochemical aptasensor showed good sensitivity with a value of 1.94 μA/ng/mL and was partially selective in the presence of interfering divalent ions (Cu2+, Hg2+, Ni2+, and Zn2+). The RSD within the linear detection range (0.1-10 ppb) is 0.28%. The IJP aptasensor has simple and cost-effective compositions, consuming only 0.5 mg of Au loading of ink during the inkjet-printing process. Minimal chemical waste is also produced because the sample volume requirement for the analysis is only 50 μL. The IJP aptasensor has promising potential for rapid and on-site detection of Cd2+ in water samples using a portable CV system. Keywords: aptamer, cadmium ions, field-ready, gold electrode, inkjet-printed, voltammetric detectionIn this work, a simple and cost-effective integrated electrode system consisting of aptamermodified inkjet-printed (IJP) gold working electrode and unmodified IJP gold as counter electrode (both printed on polyethylene naphthalate substrate) has been developed for low-cost detection of cadmium (II) ion in water. The technique uses a Cd2+ (Cd-4) aptamer, a singlestranded DNA with 31 nucleotides trapped on the working electrode using the self-assembly monolayer (SAM) technique. The electrochemical detection of Cd2+ is based on the change in redox peaks of [Fe(CN)6]3-/4- as a redox probe in cyclic voltammetry. The change in peak current is caused by a difference in electron transfer rate before and after binding the aptamer with the target ion (Cd2+). The electrochemical properties were further characterized using electrochemical impedance spectroscopy under optimal conditions, revealing changes in the charge transfer resistance upon binding the Cd2+ ion with the aptamer on gold. Detection by CV, the anodic peak currents (Ipa) varied linearly with Cd2+ concentration from 0.1-10 ng/mL. Saturation of the working electrode's active surface area was achieved with 10 ng/mL. The regression coefficient was 0.9977, whereas for the Cd2+ aptasensor, the limit of detection (LOD) was 0.5 ng/mL. The developed electrochemical aptasensor showed good sensitivity with a value of 1.94 μA/ng/mL and was partially selective in the presence of interfering divalent ions (Cu2+, Hg2+, Ni2+, and Zn2+). The RSD within the linear detection range (0.1-10 ppb) is 0.28%. The IJP aptasensor has simple and cost-effective compositions, consuming only 0.5 mg of Au loading of ink during the inkjet-printing process. Minimal chemical waste is also produced because the sample volume requirement for the analysis is only 50 μL. The IJP aptasensor has promising potential for rapid and on-site detection of Cd2+ in water samples using a portable CV system. [ABSTRACT FROM AUTHOR]

Phenolic compounds impact human health and the environment in both beneficial and undesirable manners. While some phenols are known to be antioxidants, others function as hormones or neurotransmitters, some are significant environmental contaminants, and others have the potential to cause cancer or disturb the endocrine system. To track the amount of toxicity, it is essential to identify and measure these phenols in food, the environment, and human samples. A novel phenol sensing amperometric enzymatic biosensor with a gold electrode was fabricated based on covalent immobilisation of synthesised laccase nanoparticles (LacNPs). The process of synthesising laccase nanoparticles was examined using UV–visible spectrophotometry, FTIR, transmission electron microscopy, zeta potential, and dynamic light scattering techniques. For analysis of electrode fabrication (LacNPs-AuE), scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectra including Nyquist plots and Bode's plot were examined. Optimisation and evaluation of fabricated biosensor were investigated using cyclic voltammetry studies. The LacNPs-AuE biosensor's overall characteristics were enhanced by the direct immobilisation of laccase nanoparticles, enabling the analysis at a lower detection limit (0.3 μM), wider linear range (0.1–100 μM and 100 to 600 μM), faster response time (3 s), and high recovery (92–98%). Tea, alcohol, and pharmaceutical samples were tested for total phenolic content using the biosensor; the results were compared with spectrophotometric data. [ABSTRACT FROM AUTHOR]

Polystyrene (PS), a polymer material renowned for its notable optical and mechanical properties, as well as low cost and ease of processing, stands as one of optimal candidate for flexible electrode substrate materials. However, prevalent modification techniques such as lithography, electron beam evaporation, and plasma etching all entail the requirement for specialized equipment and precise operation, thereby significantly elevating the technical barrier. In this study, we introduce a chemical plating method to fabricate a gold film electrode, coupled with prussian blue (PB) and glucose oxidase (GOx), for the development of a glucose electrochemical biosensor. This process offers simplicity, cost‐effectiveness, and feasibility under regular experimental conditions. The electrode surface is covered with numerous gold nanoparticles, effectively augmenting the actual electrode area and enhancing electron transfer efficiency. Remarkably, without the addition of sensitizing agents, the biosensor achieves highly sensitive glucose detection. The proposed biosensor exhibits a broad linear relationship in the concentration range of 0.005–1 mM, with a detection limit of 4.4 μM. Moreover, it exhibits favorable performance in detecting glucose levels in sweat samples, showcasing promising prospects for personal healthcare diagnostics. [ABSTRACT FROM AUTHOR]

Nanoporous gold electrodes are of great interest in electroanalytical chemistry, because of their unusual activity and large surface area. The electrochemical activity can be further improved by coating with molecular catalysts such as the tetraruthenated cobalt‐tetrapyridylporphyrazines investigated in this work. The plasmonic enhancement of the scattered light at the nanoholes and borders modifies the electrode's optical characteristics, improving the transmission through the surface‐enhanced Raman scattering (SERS) effect. When monitored by hyperspectral dark‐field and confocal Raman microscopy, this effect allows probing of the porphyrazine species at the plasmonic nanholes, improving the understanding of the chemically modified gold electrodes. [ABSTRACT FROM AUTHOR]

A novel electrochemiluminescence (ECL) method was developed for determination of protein kinase A (PKA) ultra-sensitively based on amidated nano-titanium (NH2-TiO2) embellished carbon dots (Mg@N-CDs) fluorescent probe, which integrated the target recognition and ECL signal enhancement. The Cys-labeled kemptides were employed to build a serine-rich synthetic substrate-heptapeptide (Cys-kemptide) on the Au-electrode surface. Then, the PKA-induced biosensor was triggered as a signal switch to introduce the large amounts of TiO2 decorated Mg@N-CD nanohybrid (Ti@NMg-CDs) into AuE/Cys-phosphopeptides for signal output. In particular, the presence of PKA could induce the formation of Cys-phosphopeptides by the catalytic reaction between specific substrate (kemptide) and PKA, which acts as an initiator to link the Ti@NMg-CDs according to the bridge interactions Ti–O-P. In this way, multiple Cys-phosphopeptides were adsorbed onto a single Ti@NMg-CDs, and the Ti@NMg-CDs not only provided high specific selectivity but also large surface area, as well as unprecedented high ECL efficiency. Using this PKA-induced enhanced sensor, the limit of detection of the PKA was 4.89 × 10−4 U/mL (S/N = 3). The proposed ECL biosensor was also universally applicable for the screening of PKA inhibitors and determining of other kinases activity. Our sensing system has excellent performance of specificity and the screening of kinase inhibitors, as well as it will inspire future effort in clinical diagnostics and new drug discovery. [ABSTRACT FROM AUTHOR]

A unique method for determining chlorophyll content in microalgae is devised employing a gold interdigitated electrode (G-IDE) with a 10-µm gap, augmented by a nano-molecularly imprinted polymer (nano-MIP) and a titanium dioxide/multiwalled carbon nanotube (TiO2/MWCNT) nanocomposite. The nano-MIP, produced using chlorophyll template voids, successfully trapped chlorophyll, while the TiO2/MWCNT nanocomposite, synthesized by the sol–gel technique, exhibited a consistent distribution and anatase crystalline structure. The rebinding of procured chlorophyll powder, which was used as a template for nano-MIP synthesis, was identified with a high determination coefficient (R2 = 0.9857). By combining the TiO2/MWCNT nanocomposite with nano-MIP, the G-IDE sensing method achieved a slightly better R2 value of 0.9892 for detecting chlorophyll in microalgae. The presented G-IDE sensor showed a significant threefold enhancement in chlorophyll detection compared with commercially available chlorophyll powder. It had a detection limit of 0.917 mL (v/v) and a linear range that spanned from 10-6 to 1 mL. The effectiveness of the sensor in detecting chlorophyll in microalgae was confirmed through validation of its repeatability and reusability. [ABSTRACT FROM AUTHOR]

Uracil (U) in DNA plays an important role in numerous biological processes. It can be introduced through two primary mechanisms, cytosine deamidation and misincorporation of dUMP during DNA replication. The misincorporation of U in DNA is associated with various diseases, especially cancer. Here, we developed an electrochemical method utilizing a modified electrode with self-assembled gold nanoparticles on covalent organic frameworks (COF-V-AuNPs) for the direct detection of U. The COF-V-AuNP composite offers numerous advantages, such as exceptional stability, abundant π-functional sites, excellent conductivity, a high specific surface area, a porous structure, and a strong non-covalent affinity, all of which facilitate sensitive detection of U. This electrochemical method achieves a detection limit of 1.92 μM for U. Furthermore, the method was successfully applied to the detection of U using human serum samples as matrices, indicating its potential for clinical applications. [ABSTRACT FROM AUTHOR]

Molten CaCl2–CaO system is a suitable electrolyte medium for reducing metal oxides to metal by in-situ electro-generated calcium metal. The graphite anode, which acts as a reactive anode in this melt, leads to several parasitic reactions and decreases the current efficiency. The present study investigates the usage of platinum anode towards the direct oxide electrochemical reduction of ThO2 and NiO by electro-generated calcium in CaCl2–1 wt % CaO melt at 900 °C. Primarily, the anodic behavior of platinum electrode was investigated using electrochemical techniques such as linear sweep voltammetry, potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic voltammetry and potentiostatic electrolysis in CaCl2–CaO melt. Platinum exhibited the most anodic polarization potential, positive corrosion potential, and highest oxidation resistance compared to nickel and gold. It also showed a clearly demarcated potential window for oxygen evolution and much better physico-chemical stability compared to gold electrode. Electro-calciothermic reduction experiments conducted with ThO2 and NiO cathodes using platinum anode demonstrated the feasibility of metallization, and platinum's mass loss rate in these experiments was found to be much less (in the order of ~ 0.016 g cm−2 h−1). The study showed that platinum could be used as an anode in the electrochemical reduction of solid metal oxides in CaCl2–1 wt % CaO melt with minimal mass loss. [ABSTRACT FROM AUTHOR]

Autonomously self‐healing, reversible, and soft adhesive microarchitectures and structured electric elements could be important features in stable and versatile bioelectronic devices adhere to complex surfaces of the human body (rough, dry, wet, and vulnerable). In this study, we propose an autonomous self‐healing multi‐layered adhesive patch inspired by the octopus, which possess self‐healing and robust adhesion properties in dry/underwater conditions. To implement autonomously self‐healing octopus‐inspired architectures, a dynamic polymer reflow model based on structural and material design suggests criteria for three‐dimensional patterning self‐healing elastomers. In addition, self‐healing multi‐layered microstructures with different moduli endows efficient self‐healing ability, human‐friendly reversible bio‐adhesion, and stable mechanical deformability. Through programmed molecular behavior of microlevel hybrid multiscale architectures, the bioinspired adhesive patch exhibited robust adhesion against rough skin surface under both dry and underwater conditions while enabling autonomous adhesion restoring performance after damaged (over 95% healing efficiency under both conditions for 24 h at 30°C). Finally, we developed a self‐healing skin‐mountable adhesive electronics with repeated attachment and minimal skin irritation by laminating thin gold electrodes on octopus‐like structures. Based on the robust adhesion and intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damaged conditions. [ABSTRACT FROM AUTHOR]

The integration of advanced materials and signaling cascade strategies is a promising and highly relevant topic for enhancing the performance of bioanalysis. In this study, a three-stage cascade amplification electrochemical bioanalysis (TCAE-bioanalysis) was developed and evaluated for the detection of zearalenone (ZEN). This method couples immunoreaction with a glucose–Fenton–hydroquinone (HQ) system on bimetallic–ZIF (B-ZIF)@CNP nanocomposites. The B-ZIF@CNP-modified gold electrode (AuE) was prepared, offering high conductivity and an excellent reaction interface. The immunoreaction introduced glucose oxidase (GOx) into the glucose–Fenton–HQ system, generating an abundant electron signal. The method achieved an ultrasensitive limit of detection (LOD) as low as 0.87 pg/mL, with an IC50 value of 30.8 pg/mL, representing a 229-fold enhancement in sensitivity compared to ELISA using the same monoclonal antibody (McAb). The specificity, reliability, and practicality of this approach were thoroughly demonstrated for agricultural product samples. Additionally, the TCAE-bioanalysis offers several advantages, including simplified preparation for advanced B-ZIF@CNP, a convenient detection system, and the use of common and environmentally friendly reagents. This study presents a comprehensive approach to improving electrochemical bioanalysis and may also expand the application of signaling cascades and environmentally friendly techniques in other biosensing or diagnostic contexts. [ABSTRACT FROM AUTHOR]

Electrochemical sensors based on self‐assembled monolayer (SAM) were synthesized using metal‐organic frameworks (MOFs), quantum dots (QDs) and their composite (QDs@MOFs) to modify gold electrode (AuE) that was used as electrochemical sensors for bisphenol A detection. The molecular layer was assembled on the surface of the gold electrode by adsorption and provide a highly flexible method to tailor the interfaces between analyte and the electrode. Single crystal X‐ray of the MOF revealed a six‐coordinate copper(II) ion that bidentately coordinate two molecules of p‐anisic acid and two molecules of 1H‐benzimidazole to form a distorted octahedral geometry around the copper(II) ion. Electrochemical studies revealed that under optimal conditions, the modified gold electrode sensors show excellent sensing of bisphenol A, however, QDs@MOFs modified electrode is the best sensor with the highest oxidation peak current of 8.43E‐05 μA and the lowest charge transfer resistance of 19.4 Ω within a wide concentration range of 0.1–1 μM and a limit of detection (LOD) of 0.252 μM. This could be attributed to the electrocatalytic activity of the composite (QDs@MOFs) modified sensor, and the synergistic effect of the MOFs and QDs in the composite. The LOD is comparable to other electrochemical methods of sensing BPA which indicates that QDs@MOFs modified gold electrode could be develop as sensor for BPA. [ABSTRACT FROM AUTHOR]

Despite the direct, redox-free and simple detection non-faradaic impedimetric biosensors offer, considerable optimizations are required to enhance their performance for the detection of various biomarkers. Non-faradaic EIS sensors' performance depends on the interfacial capacitance between a polarized biosensor surface and the tested sample solution. Careful engineering and design of the interfacial capacitance is encouraged to magnify the redout signal upon bioreceptor–antigen interactions. One of the methods to achieve this goal is by optimizing the self-assembled monolayer concentration, which has not been reported for non-faradaic impedimetric sensors. Here, the impact of alkanethiolate (cysteamine) concentration on the performance of gold (Au) interdigitated electrode (Au-IDE) biosensors is reported. Six sets of biosensors were prepared, each with a different cysteamine concentration: 100 nM, 1 μM, 10 μM, 100 μM, 1 mM, and 10 mM. The biosensors were prepared for the direct detection of LDL cholesterol by attaching LDL antibodies on top of the cysteamine via a glutaraldehyde cross-linker. As the concentration of cysteamine increased from 100 nM to 100 μM, the sensitivity of the biosensor increased from 6.7 to 16.2 nF/ln (ng/mL). As the cysteamine concentration increased from 100 μM to 10 mM, the sensitivity deteriorated. The limit of detection (LoD) of the biosensor improved as the cysteamine increased from 100 nM to 100 μM (i.e., 400 ng/mL to 59 pg/mL). However, the LoD started to increase to 67 pg/mL and 16 ng/mL for 1 mM and 10 mM cysteamine concentrations, respectively. This shows that the cysteamine concentration has a detrimental effect on redox-free biosensors. The cysteamine layer has to be as thin as possible and uniformly cover the electrode surfaces to maximize positive readout signals and reduce negative signals, significantly improving both sensitivity and LoD. [ABSTRACT FROM AUTHOR]

Single molecule junctions based on selected 4,4′-biphenyldithiol and 4,4′-dicyanobiphenyl derivatives bonded to gold electrodes are analyzed from a dynamical point of view. A fully quantum mechanical description of the internal rotation of the biphenyl moiety is carried out in terms of the nuclear wavepacket dynamics obtained by the solution of the time-dependent Schrödinger equation expressed in terms of the torsion angle between the phenyl rings. The required potential energy surfaces are computed using ab initio electronic structure methods. The nature and positions of the substituents on the phenyl rings determine the features of the potential energy surfaces. The effect of the initial conditions on the time propagation of the nuclear wavepackets and, as a consequence, on the evolution of the conformational distribution is also analyzed. In addition, the conductances at zero bias for the nanojunctions were computed for different conformations of the biphenyl fragments. Weighted by the wavepacket amplitudes, non-stationary conductance expectation values, and time-averaged torsion angles and conductances for the entire simulation are obtained. The consequences of using the time-averaged values to perform a linear regression between the conductance and the square of the cosine of the dihedral angle between the phenyl rings are analyzed and compared to the usual static approach based only on the information for equilibrium geometries. The study of the time dependent conformational variations of the biphenyl moieties in the nanojunctions allows for a better understanding of the quantum chemical phenomena that affect their transport properties. [ABSTRACT FROM AUTHOR]

[Display omitted] Strong molecule-electrode coupling originating from orbit hybridization between gold and the delocalized molecular wires in single-molecule junctions facilitates facile transport towards smart molecular devices. In this paper, we report ultra-highly conductive single-molecule circuits based on highly delocalized nickel bis(dithiolene) (NiS 4) molecular junctions using scanning tunneling microscope break junction technique. Single-molecule charge transport measurement of both NiS 4 reveals they exhibits high conductance of 10−1.49 G 0 and 10−1.51 G 0 , respectively. Moreover, under intervention of high bias voltage the molecular conductance could be further improved to approximately 10−1.00 G 0 , the highest value reported to date with similar molecular lengths. Theoretical calculations suggest that the strong hybridization of the π-channels and the gold electrodes in both junctions exists and it further extends from molecule-electrode interfaces to metal electrodes as visualized by the isosurface plots of the transmitting eigenstate, which lead to not only a distinct energy shift of the dominated LUMO peaks toward Fermi level, but also broad peaks in the LUMO resonance in the transmission functions. In addition, the both molecular junctions show remarkable photoconductance of approximately 10−1.00 G 0 under resonant light excitation, due to possible exciton binding in these junctions. Interestingly, the conductance switching of both molecular junctions under optoelectronic modulation is highly reversible, forming a multi-stimulus responsive molecular switch. This work not only provides a building block for fabricating highly conducting molecular wires with strong molecule-electrode coupling, but also lays a foundation for designing optoelectronic modulated functional molecule-scale devices. [ABSTRACT FROM AUTHOR]

Understanding the electric double layer (EDL) of the metal electrode–electrolyte interface is essential to electrochemistry and relevant disciplines. In this study, potential-dependent electrode Sum Frequency Generation (SFG) intensities of polycrystalline gold electrodes in HClO4 and H2SO4 electrolytes were thoroughly analyzed. The potential of zero charges (PZC) of the electrodes was −0.06 and 0.38 V in HClO4 and H2SO4, respectively, determined from differential capacity curves. Without specific adsorption, the total SFG intensity was dominated by the contribution from the Au surface and increased similar to that of the visible (VIS) wavelength scanning, which pushed the SFG process closer to the double resonant condition in HClO4. However, the EDL contributed about 30% SFG signal with specific adsorption in H2SO4. Below PZC, the total SFG intensity was dominated by the Au surface contribution and increased with potential at a similar slope in these two electrolytes. Around PZC, as the EDL structure became less ordered and the electric field changed direction, there would be no EDL SFG contribution. Above PZC, the total SFG intensity increased much more rapidly with potential in H2SO4 than in HClO4, which suggested that the EDL SFG contribution kept increasing with more specific adsorbed surface ions from H2SO4. [ABSTRACT FROM AUTHOR]

Fast and sensitive detectors for weak light are crucial in various fields like real‐time monitoring, medical diagnosis, and astronomy. However, photodetectors using 2D materials face challenges in achieving both a low detection limit for weak light and fast response. Here, a vertical vdW graphene/indium selenide (InSe)/hexagonal boron nitride (h‐BN) heterostructure on a gold electrode is provided, demonstrating an ultra‐low detection limit of 47.4 nW cm−2 and an ultra‐fast response speed of 327 ns. Vertical photodetectors feature nanoscale channel length, thus reducing scattering and recombination of carriers. The high potential barrier of multilayer h‐BN effectively blocks carrier transport, resulting in ultra‐low dark current and minimal power dissipation. Additionally, enhanced light absorption in InSe by the metal‐insulator‐semiconductor structure improves the sensitivity to weak light detection. More importantly, the built‐in field at the graphene/InSe interface can promote the separation of photo‐generated carriers to improve the collection efficiency. These factors jointly reduce the detection limit and response time simultaneously for weak light. This vertical vdW heterostructure comprising a 2D semiconductor/h‐BN offers a solution to make the majority of 2D semiconductors applicable in ultra‐fast weak light detectors. [ABSTRACT FROM AUTHOR]

In this work, we comprehensively studied the cathodic corrosion of Au electrodes as a function of the identity of alkali metal hydroxides at different concentrations and various negative potentials. We reveal that the ratio of free water and water bound in hydration shells controls the overall cathodic corrosion behavior, alongside the specific adsorption of alkali metal cations. Moreover, we highlight the crucial role of electrolyte cleanliness, particularly regarding the presence of trace metal impurities. Interestingly, the presence of trace amounts of nickel and iron in as‐received CsOH suppresses cathodic corrosion by their deposition onto Au surfaces. In contrast, after purification the polarization of Au surfaces in 10 M CsOH leads to the formation of nanoporous surfaces with high electrochemically active surface area, in which the degree of porosity can be tuned by varying the polarization time at −1.6 V vs. RHE. [ABSTRACT FROM AUTHOR]

Enzyme‐modified electrodes are core components of electrochemical biosensors for diagnostic and environmental analytics and have promising applications in bioelectrocatalysis. Despite huge research efforts spanning decades, design of enzyme electrodes for superior performance remains challenging. Nanoporous gold (npAu) represents advanced electrode material due to high surface‐to‐volume ratio, tunable porosity, and intrinsic redox activity, yet its coupling with enzyme catalysis is complex. Here, the study reports a flexible‐modular approach to modify npAu with functional enzymes by combined material and protein engineering and use a tailored assortment of surface and in‐solution methodologies for characterization. Self‐assembled monolayer (SAM) of mercaptoethanesulfonic acid primes the npAu surface for electrostatic adsorption of the target enzyme (flavocytochrome P450 BM3; CYT102A1) that is specially equipped with a cationic protein module for directed binding to anionic surfaces. Modulation of the SAM surface charge is achieved by electrochemistry. The electrode‐adsorbed enzyme retains well the activity (33%) and selectivity (complete) from in‐solution. Electrochemically triggered nanoscale stirring in the internal porous network of npAu‐SAM enhances speed (2.5‐fold) and yield (3.0‐fold) of the enzyme immobilization. Biocatalytic reaction is fueled from the electrode via regeneration of its reduced coenzyme (NADPH). Collectively, the study presents a modular design of npAu‐based enzyme electrode that can support flexible bioelectrochemistry applications. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) including the superoxide anion (O2•−) are typically studied in cell cultures using fluorescent dyes, which provide only discrete single-point measurements. These methods lack the capabilities for assessing O2•− kinetics and release in a quantitative manner over long monitoring times. Herein, we present the fabrication and application of an electrochemical biosensor that enables real-time continuous monitoring of O2•− release in cell cultures for extended periods (> 8 h) using an O2•− specific microelectrode. To achieve the sensitivity and selectivity requirements for cellular sensing, we developed a biohybrid system consisting of superoxide dismutase (SOD) and Ti3C2Tx MXenes, deposited on a gold microwire electrode (AuME) as O2•− specific materials with catalytic amplification through the synergistic action of the enzyme and the biomimetic MXenes-based structure. The biosensor demonstrated a sensitivity of 18.35 nA/μM with a linear range from 147 to 930 nM in a cell culture medium. To demonstrate its robustness and practicality, we applied the biosensor to monitor O2•− levels in human leukemia monocytic THP-1 cells upon stimulation with lipopolysaccharide (LPS). Using this strategy, we successfully monitored LPS-induced O2•− in THP-1 cells, as well as the quenching effect induced by the ROS scavenger N-acetyl-l-cysteine (NAC). The biosensor is generally useful for exploring the role of oxidative stress and longitudinally monitoring O2•− release in cell cultures, enabling studies of biochemical processes and associated oxidative stress mechanisms in cellular and other biological environments. [ABSTRACT FROM AUTHOR]

Nanorod structures exhibit a high surface-to-volume ratio, enhancing the accessibility of electrolyte ions to the electrode surface and providing an abundance of active sites for improved electrochemical sensing performance. In this study, tetragonal α-MnO2 with a large K+-embedded tunnel structure, directly grown on microfibrous carbon paper to form densely packed nanorod arrays, is investigated as an electrocatalytic material for non-enzymatic glucose sensing. The MnO2 nanorods electrode demonstrates outstanding catalytic activity for glucose oxidation, showcasing a high sensitivity of 143.82 µA cm−2 mM−1 within the linear range from 0.01 to 15 mM, with a limit of detection (LOD) of 0.282 mM specifically for glucose molecules. Importantly, the MnO2 nanorods electrode exhibits excellent selectivity towards glucose over ascorbic acid and uric acid, which is crucial for accurate glucose detection in complex samples. For comparison, a gold electrode shows a lower sensitivity of 52.48 µA cm−2 mM−1 within a linear range from 1 to 10 mM. These findings underscore the superior performance of the MnO2 nanorods electrode in both sensitivity and selectivity, offering significant potential for advancing electrochemical sensors and bioanalytical techniques for glucose monitoring in physiological and clinical settings. [ABSTRACT FROM AUTHOR]

Neuropeptide Y (NPY) plays a central role in a variety of emotional and physiological functions in humans, such as forming a part of the body′s response to stress and anxiety. This work compares the impact of MCH and PEG spacer molecules on the performance of a potentiometric NPY sensor. An NPY‐specific DNA aptamer with thiol termination was immobilized onto a gold electrode surface. The performance of the sensor is compared when either an MCH‐ or PEG‐based self‐assembled monolayer is formed following aptamer immobilization. Backfilling the surface with alkanethiol spacer molecules like these is key for proper conformational folding of aptamer‐target binding. Non‐specific adhesion of NPY to the MCH‐based sensor surface was observed via surface plasmon resonance (SPR), and then confirmed via potentiometry. It is then shown that PEG improves the sensor′s sensitivity to NPY compared to the surfaces with an MCH‐based SAM. We achieve the detection of picomolar range NPY levels in buffer with a sensitivity of 36.1 mV/decade for the aptamer and PEG‐based sensor surface, thus demonstrating the promise of potentiometric sensing of NPY for future wearable deployment. The sensor′s selectivity was also studied via exposure to cortisol, a different stress marker, resulting in a 13x smaller differential voltage (aptamer‐specific) response compared to that of NPY. [ABSTRACT FROM AUTHOR]