Oxidation Peak Potential Research Articles

A Wearable Electrochemical Sensor Based on Single-Atom Pt Anchored on Activated NiCo-LDH/Ti3C2Tx for Real-Time Monitoring of Glucose.

Wearable, noninvasive sweat sensors enable real-time monitoring of metabolites in human health management. However, the commercial enzyme-based and currently nonenzymatic glucose sensor represents sluggish glucose oxidation kinetics and a narrow sensing range. Rational design of sensitive materials is significant yet faces a huge challenge. Herein, we construct a single-atom Pt supported on NiCo-LDH/Ti3C2Tx heterostructures (Pt1-NiCo-LDH/Ti3C2Tx) as the nonenzymatic electrochemical glucose sensor sensitive materials for selective detection of glucose level in human sweat. The obtained Pt1-NiCo-LDH/Ti3C2Tx with improved structural stability and enhanced charge transfer efficiency shows a low oxidation peak potential of 0.49 V, high sensitivity of 506.6 μA mM-1 cm-2, a low detection limit of 0.035 μM, and long-term stability toward the glucose detection. The wearable sensor, coupled with a wireless transmission module and a signal processing chip, is used for real-time perspiration glucose monitoring during outdoor exercise. The result is comparable to that of high-performance liquid chromatography (HPLC). This research provides a new paradigm for designing a wearable nonenzymatic electrochemical glucose sensor, enabling noninvasive real-time monitoring of glucose concentrations in human sweat.

Simultaneous detection of moxifloxacin and gatifloxacin by Cu-TCPP/rGO electrochemical sensor

Moxifloxacin (MOX) and gatifloxacin (GAT) are structurally similar and possess close oxidation peak potentials, making it difficult for simultaneous detection by electrochemical methods. To address this, an electrochemical sensor was constructed with reduced graphene oxide (rGO) and copper porphyrin complex (Cu-TCPP), achieving signal amplification and simultaneous detection of MOX and GAT. The linear relation range from 5.00 to 600.00 μmol·L−1 for MOX (LOD is 1.34 μmol·L−1) and 10 to 300 μmol·L−1 for GAT (LOD is 0.59 μmol·L−1). When applied to water samples, it achieved recoveries of 100.09–112.02 % with a relative standard deviation (RSD) of less than 6 % for MOX, and 97.27–110.72 % with an RSD of less than 4 % for GAT. Further calculations indicated that the electro-oxidation of GAT involved two protons and two electrons.

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion.

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Oxidation Potential of 2,6-Dimethyl-1,4-dihydropyridine Derivatives Estimated by Structure Descriptors

Linear relationships, expressing the electrochemical properties of molecules as functions of structure, give insight into the associated electrochemical process and are a tool for prediction. Many biological activities rely on water-based dissociation, making electrochemical properties a bridge between structure and activity. Motivated by a previous study, a replica is made here on a different dataset in order to validate/invalidate the previously reported results. There are several methods for obtaining structure-based descriptors. Some of the methods have been devised to account for molecular topology, some to account for molecular geometry, and others to account for both. Two methods are involved here to derive structure-based descriptors and further obtain structure–property relationships (FMPI and ChPE). In order to express structure descriptors, both FMPI and ChPE express first the topology of the molecule, using the heavy atoms identity matrix and the heavy atoms adjacency matrix, both square symmetric matrices in the belief that symmetry is one major factor of molecular stability. A set of 2,6-dimethyl-1,4-dihydropyridine derivatives with oxidation peak potentials and coulometrically determined number of electrons experimental data is subjected to the search for structure–activity relationships. Even if the 2,6-dimethyl-1,4-dihydropyridine is a symmetric compound (of Cs point group), their derivatives are generally not symmetric (9 out of 24 are asymmetric). The dataset is subjected to descriptive and inferential statistics in order to filter out the most relevant structure–activity relationship. The geometry is built using three levels of theory (one from molecular mechanics and two others from density functionals, of which one accounts for the interaction with water as solvent). One challenge of picking one out of two reported measured values is dealt with by calculating the likelihood associated with the two choices. Relevant structure–activity models are extracted and discussed. The use of in vivo (in water, SM8 model) models in geometry optimization (from MMFF94 and B3LYP and to M06 + Water SM8) results in a precision gain, but this is, in most of the cases, not statistically significant, and this can be considered a negative result.

Design of high-performance electrochemical sensor based on SnS2 nanoplates and ionic liquid-modified carbon paste electrode for determination of hydrazine in water samples

Designing effective and accurate analytical techniques to determine hydrazine is essential for preserving the environment. Herein, an electrochemical sensor based on a carbon paste electrode (CPE) modified with SnS2 nanoplates (SnS2NPs) and ionic liquid (IL) was presented for determination of hydrazine in water samples. The SnS2NPs were synthesized using the hydrothermal method and characterized through field emission scanning electron microscope, Fourier transform infrared spectrometer and energy dispersive spectroscopy. The use of cyclic voltammetry in electrochemical investigations has shown that incorporating IL and SnS2NPs in an electrochemical sensor significantly improves its efficiency. These results in a considerable increase in the oxidation peak current and a decrease in the oxidation peak potential of hydrazine compared to an unmodified CPE. The method of differential pulse voltammetry was utilized to accurately measure the quantity of hydrazine. The SnS2NPs/ILCPE showed improved sensing capabilities, resulting in a noticeable sensitivity of 0.0747 µA/µM and a low limit of detection of 0.05 µM for a broad linear range of hydrazine concentration from 0.08 µM to 450.0 µM. In addition, the SnS2NPs/ILCPE sensor was successfully utilized to measure the amount of hydrazine present in water samples, with a recovery range of 96.0 to 104.4 %. The relative standard deviation was found to be lower than 3.6 % (n = 5), indicating that the developed sensor is suitable for accurately determining hydrazine in water samples with high sensitivity.

Surface functionalization of graphene electrode using flavin AuNps for a realtime sensing of asparagine

Asparagine (ASN) is one of the major non-essential amino acids and helps to breakdown the toxic ammonia within the cell. The electrochemical detection of asparagine was performed by the surface functionalized screen-printed carbon (MSPEC) and screen-printed graphene electrodes (MSPEG) through flavin (Quercetin) based gold nanoparticles (AuNps). Cyclic voltammetry (CV) and Differential Pulse Voltammetry (DPV) were performed through MSPEC and MSPEG at single drop of analyte via DROPSENS. SEM and Electrochemical Impedance (EIS) examined for the surface characteristics, enhancement, and functionality of electrodes modified with flavin AuNps. The surface functionalized electrodes revealed excellent electrochemical sensor with high stability, selectivity, repeatability, and have a low limit detection of 0.001 nM. Also, sensors progression was found to occur through adsorption-controlled phenomena. The oxidation peak potential for asparagine in CV and DPV was well-expressed by the MSPEC and MSPEG, with potentials of +0.0881 V and +0.3141 V, respectively. Hence the flavin based AuNps is a new sensing platform for the consistent asparagine real-time sensor and the selective electrochemical detection of asparagine with an exceptionally low detection limit at one drop.

Development of novel electrochemical sensor based on Co-Fe layered double hydroxide for simultaneous determination of Hydroquinone, Catechol, and Resorcinol

In this work, a novel electrochemical sensor was developed using a glassy carbon electrode modified with Co-Fe-layered double hydroxides (Co/Fe-LDH/GCE) for the detection of dihydroxybenzene isomers (Hydroquinone (HQ), Catechol (CC), and Resorcinol (RS) due to the large active surface area, facile electronic transport, and high electrocatalytic activity features of LDH. X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDX), and scanning electron microscopy (SEM) techniques were used to characterize the modifier. Under the optimized conditions, the differential pulse voltammetry (DPV) method was used as a sensitive and efficient method to measure dihydroxybenzene isomers. Well-separated oxidation peak potentials corresponding to HQ, CC, and RS were observed at 0.04 V, 0.150 V, and 0.560 V, respectively. The linear range was 2.5 × 10−9 to 1.2 × 10−5 M for hydroquinone and catechol and 7.5 × 10−9 to 4.2 × 10−6 M for resorcinol, with a detection limit of 0.001, 0.001, and 0.005 µM (S/N=3) for hydroquinone, catechol, and resorcinol, respectively. The Co/Fe-LDH sensor demonstrated a fast response, high sensitivity, excellent stability, and satisfactory repeatability. The modified electrode was successfully applied to the direct determination of DBIs in river water, providing reliable recovery data.

Electrochemical Quantification of Enkephalin Peptides Using Fast-Scan Cyclic Voltammetry.

Endogenous opioid neuropeptides serve as important chemical signaling molecules in both the central and peripheral nervous systems, but there are few analytical tools for directly monitoring these molecules in situ. The opioid peptides share the amino acid motif, Tyr-Gly-Gly-Phe-, at the N-terminus. Met-enkephalin is a small opioid peptide comprised of only five amino acids with methionine (Met) incorporated at the C-terminus. Tyrosine (Tyr) and Met are electroactive, and their distinct electrochemical signatures can be utilized for quantitative molecular monitoring. This work encompasses a thorough voltammetric characterization of Tyr and Met redox chemistry as individual amino acids and when incorporated into small peptide fragments containing the shared Tyr-Gly-Gly-Phe- motif. NMR spectroscopy was used to determine the structure and conformation at near-physiological conditions. Voltammetric data demonstrate how the peak oxidation potential and the rate of electron transfer are dependent on the local chemical environment. Both the proximity of the electroactive residue to the C- or N-terminus and the hydrophobicity of the additional nonelectroactive amino acids profoundly affect sensitivity. Finally, the work uses the electrochemical signal for individual amino acids in a "training set", with a combination of principal component analysis and least-squares regression to accurately predict the voltammetric signal for short peptides comprising different combinations of those amino acids. Overall, this study demonstrates how fast-scan cyclic voltammetry can be utilized to discriminate between peptides with small differences in the chemical structure, thus establishing a framework for reliable quantification of small peptides in a complex signal, broadly speaking.

Simultaneous voltammetric detection of acetaminophen and levofloxacin based on barley leaves derived carbon decorated with gold nanoparticles

In this study, barley leaves were used as biomass precursor to prepare the ZnCl2 activated barley leaves derived carbon by the carbonization under N2 atmosphere at high temperature (ZnAC). The gold nanoparticles were synthesized in situ on the surface of ZnAC (AuNPs/ZnAC). The as-prepared AuNPs/ZnAC composite was characterized by SEM, Raman spectroscopy, XRD et. al. The AuNPs/ZnAC composite was drop-cast onto the surface of a glassy carbon electrode to fabricate an electrochemical sensing platform for the simultaneous determination of acetaminophen (AC) and levofloxacin (LEV). The results of electrochemical experiments showed that ZnAC and AuNPs had a synergetic electrocatalytic effect on the oxidation of AC and LEV. The oxidation peak potentials of AC and LEV were at 0.57 and 1.02 V, respectively. The proposed sensor allowed the simultaneous quantification of AC and LEV two linear intervals: in the ranges of 0.1–15 and 15–300 μM for AC and 0.1–20 and 20–300 μM for LEV with the detection limits of 0.02 and 0.03 μM, respectively. In addition, the sensor has the advantages of low cost, high sensitivity, simple preparation and environmental friendliness, as well as good selectivity, stability and reproducibility. We measured AC and LEV in artificial urine, tap water, and lake water, and the recoveries were between 93 % and 109 %, indicating that the sensor has good application prospects in biomedicine and environmental protection.

Magnesium(II) Porphyrazine with Thiophenylmethylene Groups-Synthesis, Electrochemical Characterization, UV-Visible Titration with Palladium Ions, and Density Functional Theory Calculations.

The presented studies aimed to evaluate the peripheral coordinating properties of a novel porphyrinoid family representative preceded by its synthesis for potential sensing purposes. Two synthetic pathways were employed to a obtain maleonitrile derivative, further used as a starting material in the cyclotetramerization reaction. In the first one, DAMN was used in sequential double-reductive alkylation with 2-thiophene-carboxyaldehyde and sodium borohydride. In the second, DAMN was used in a one-pot reaction with 2-thiophene-carboxyaldehyde in the presence of a 5-ethyl-2-methylpyridine borane complex in methanol and acetic acid. Following the Linstead approach, the cyclization reaction led to a novel symmetrical magnesium(II) octaaminoporphyrazine with methyl(2-thiophenylmethylene) substituents. The macrocycle's electrochemical properties were assessed by cyclic and differential pulse voltammetries revealing one reduction and two oxidation peak potentials. The additional spectroelectrochemical measurements showed formation of a cationic form of the macrocycle at an applied potential of 0.6 V. The coordinating properties due to the palladium ion of novel porphyrazines were measured with the use of titration combined with UV-vis spectrometry. The titration of Pd2+ revealed the good sensing activity of porphyrazine in the range of 0.1 to 5 palladium molar equivalents. In addition, Pd2+ ions coordination was also assessed by electrochemical studies, indicating the peak potential shift of 0.1 V in the presence of metal cations. DFT calculations showed the good agreement between theoretical and experimental data in the UV-vis and 1H NMR studies.

Conducting Nickel Hydroxide Thin Film on Molybdenum Disulfide – Reduced Graphene Oxide Composite Electrode for Simultaneous Detection of Uric Acid, Dopamine and Ascorbic Acid

AbstractHerein we report the fabrication of a simple electrochemical sensor based on an electrode containing reduced graphene oxide and molybdenum disulphide (RGO/MoS2) as a conducting film onto the glassy carbon electrode (GCE) via a drop dry method to form GCE‐RGO/MoS2. The surface (GCE‐RGO/MoS2) was further modified with nickel hydroxide thin film using electrodeposition method to form GCE‐RGO/MoS2/Ni(OH)2. The materials and modification steps were thoroughly characterized using microscopy and spectroscopy methods. The composite electrode, GCE‐RGO/MoS2/Ni(OH)2, showed excellent electrocatalytic potential separation for the detection of dopamine, uric acid, and ascorbic acid. The electrocatalytic oxidation peak potentials were at 3 mV, 157 mV and 303 mV for AA, DA and UA, respectively. The composite electrode was also selective towards the determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), and simultaneously in mixture of analytes. The low detection limits for AA, DA and UA were 1.17 μM, 0.15 μM and 1.15 μM, respectively. The composite electrode was applied for the detection of AA, DA and UA in spiked newborn calf serum samples with high percentage recoveries ranging from 96.6–100.8 % for AA, 92.8–104.2 % for DA and 99.4–102.3 % for UA.

Mechanisms Associated with Superoxide Radical Scavenging Reactions Involving Phenolic Compounds Deduced Based on the Correlation between Oxidation Peak Potentials and Second-Order Rate Constants Determined Using Flow-Injection Spin-Trapping EPR Methods.

Flow-injection spin-trapping electron paramagnetic resonance (FI-EPR) methods that involve the use of 5,5-dimethyl-pyrroline-N-oxide (DMPO) as a spin-trapping reagent have been developed for the kinetic study of the O2•- radical scavenging reactions occurring in the presence of various plant-derived and synthetic phenolic antioxidants (Aox), such as flavonoid, pyrogallol, catechol, hydroquinone, resorcinol, and phenol derivatives in aqueous media (pH 7.4 at 25 °C). The systematically estimated second-order rate constants (ks) of these phenolic compounds span a wide range (from 4.5 × 10 to 1.0 × 106 M-1 s-1). The semilogarithm plots presenting the relationship between ks values and oxidation peak potential (Ep) values of phenolic Aox are divided into three groups (A1, A2, and B). The ks-Ep plots of phenolic Aox bearing two or three OH moieties, such as pyrogallol, catechol, and hydroquinone derivatives, belonged to Groups A1 and A2. These molecules are potent O2•- radical scavengers with ks values above 3.8 × 104 (M-1 s-1). The ks-Ep plots of all phenol and resorcinol derivatives, and a few catechol and hydroquinone derivatives containing carboxyl groups adjacent to the OH groups, were categorized into the group poor scavengers (ks < 1.6 × 103 M-1 s-1). The ks values of each group correlated negatively with Ep values, supporting the hypothesis that the O2•- radical scavenging reaction proceeds via one-electron and two-proton processes. The processes were accompanied by the production of hydrogen peroxide at pH 7.4. Furthermore, the correlation between the plots of ks and the OH proton dissociation constant (pKa•) of the intermediate aroxyl radicals (ks-pKa• plots) revealed that the second proton transfer process could potentially be the rate-determining step of the O2•- radical scavenging reaction of phenolic compounds. The ks-Ep plots provide practical information to predict the O2•- radical scavenging activity of plant-derived phenolic compounds based on those molecular structures.

The Effect of the Capping Agents of Nanoparticles on Their Redox Potential.

Engineered metallic nanoparticles, which are found in numerous applications, are usually stabilized by organic ligands influencing their interfacial properties. We found that the ligands affect tremendously the electrochemical peak oxidation potentials of the nanoparticles. In this work, identical gold nanoparticles were ligand-exchanged and carefully analyzed to enable a precise and highly reproducible comparison. The peak potential difference between gold nanoparticles stabilized by various ligands, such as 2- and 4-mercaptobenzoic acid, can be as high as 71 mV, which is substantial in energetic terms. A detailed study supported by density functional theory (DFT) calculations aimed to determine the source of this interesting effect. The DFT simulations of the ligand adsorption modes on Au surfaces were used to calculate the redox potentials through the thermodynamic cycle method. The DFT results of the peak potential shift were in good agreement with the experimental results for a few ligands, but showed some discrepancy, which was attributed to kinetic effects. The kinetic rate constant of the oxidation of Au nanoparticles stabilized by 4-mercaptobenzoic acid was found to be twice as large as that of the Au nanoparticles stabilized by citrate, as calculated from Laviron's theory and the Tafel equation. Finally, these findings could be applied to some novel applications such as determining the distribution of nanoparticle population in a dispersion as well as monitoring the ligand exchange between nanoparticles.

Chiral electrochemical sensing of propranolol enantiomers on D/L-Cys modified gold nanoparticles

The present study aims to explore the interaction mechanisms between propranolol (PRNL) enantiomers and bare and L/D-Cysteine modified gold nanoparticles (L/D-Cys−AuNPs) surfaces, using electrochemical (cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy) and microcalorimetric (isothermal titration calorimetry) techniques. In the absence of a chiral environment, PRNL enantiomers are strongly physisorbed on the AuNPs modified surface, yet no significant difference was recorded in the oxidation peak potential (+0.778 V R(+)-PRNL versus +0.78 V for S(-)-PRNL). Upon decorating AuNPs with l-Cys, an ∼40 mV anodic shift is recorded for S(-)-PRNL due to a more favored orientation of its diastereoisomer on the electrode's surface towards electron transfer. Interestingly, by altering the conformation of the diastereoisomeric chiral selector (replacing l-Cys with d-Cys), the enantioselective nature of the recorded electrochemical signals fades out. Additionally, the potential synergistic effects of a dual chiral system, based on the covalently bound l-/D-Cys−AuNPs and β-cyclodextrin (β-CD), a free, host-guest type chiral selector, added to the electrolyte, has also been studied.

Electrochemical detection of benzenediols using carbon-supported catalysts

A novel implementation of an electrochemical sensors making use of Screen-Printed Electrodes (SPE) has been discussed. SPE's modified with Carbon-supported Platinum (Pt/C) and Gold (Au/C) were used to detect the three benzenediol isomers, Catechol (CC), Hydroquinone (HQ) and Resorcinol (RS) in acidic media using traditional electrochemical analytical methods such as Cyclic Voltammetry (CV), Chronoamperometry (CA) and Differential Pulse Voltammetry (DPV). Detection of each benzenediol in isolation was possible by CV measurements, and peak oxidation potentials for each isomer were noted. Simultaneous detection of more than one, or all analytes in the same solution was also observed through DPV, once again noting the peak oxidation potentials. Quantification limits were observed using CA's across concentration values ranging from close to saturation down to 1 mM for CC and HQ, and 100 nM for RS, until the recorded current values were nearly indistinguishable to a blank 1 M HCl solution containing no analyte(s), and also evaluating the maximum possible linear range of sensing. The analytes were introduced to the sensor elements in controlled amounts and the electrochemical responses of the sensor elements were recorded and processed. Measurements were repeated across two potentiostats to ensure reproducibility. With these results, successful detection of benzenediols in acidic environment was possible using modified SPE's, proving a potential viable mechanism for quick, simple and inexpensive Volatile Toxic Organic Compounds (VTOC) detection and monitoring.

Electrochemical profiling of natural furanocoumarins: DNA interaction dynamics of oxypeucedanin and prantschimgin.

In this study, we present an electrochemical sensor for the detection of oxypeucedanin (Oxyp) and prantschimgin (Pra), two natural furanocoumarin derivatives. The determination of the effects of these molecules on DNA is important to be potential drug candidates. Our research focused on exploring the electrochemical behaviour of these compounds and their interaction with DNA. The electrochemical properties of Oxyp and Pra were systematically analyzed by evaluating their oxidation currents. Changes in the oxidation currents and peak potentials of guanine bases were monitored before and after interaction in the solution phase and at the electrode surface. The limit of detection (LOD) and limit of quantitation (LOQ) for Oxyp were determined to be 1.3 and 4.3 μg/mL, respectively. For Pra, the LOD and LOQ were found to be 20 and 68 μg/mL, respectively. Stability studies demonstrated that the Oxyp solution retained its oxidation capacity for over a month, whereas the Pra solution retained its oxidation capacity for nearly 120 min. Our findings suggest that Oxyp interacts with dsDNA, potentially through electrostatic interactions, showing promise as a potential drug candidate targeting DNA. On the other hand, the interaction of Pra with dsDNA requires further exploration to fully understand its mode of action. The electrochemical sensor developed in this study provides a reliable and efficient method for detecting and analysing the interaction of these natural compounds with dsDNA. Our research contributes to advancing the understanding of the interaction between natural furanocoumarins and dsDNA, laying the groundwork for the design and development of novel and effective DNA-targeted drugs.

Simultaneous Electrochemical Detection of Dopamine and Uric Acid via Au@Cu-Metal Organic Framework.

The incorporation of noble metals with metal-organic frameworks (MOFs) are conducive to the simultaneous electrochemical detection of analytes owing to multiple accessible reaction sites. Herein, Au@Cu-metal organic framework (Au@Cu-MOF) is successfully synthesized and modified as a screen-printed carbon electrode (SPCE), which serves as an excellent electrocatalyst for the oxidation of dopamine (DA) and uric acid (UA). The sensor shows a linear range from 10 μM to 1000 μM, with sensitivity and detection limit of 0.231 μA μM-1 cm-2 and 3.40 μM for DA, and 0.275 μA μM-1 cm-2 and 10.36 μM for UA. Au@Cu-MOF could realize the individual and simultaneous electrochemical sensing of DA and UA, with distinguishable oxidation peak potentials. Moreover, it exhibits reproducibility, repeatability, and stability. Ultimately, the sensor provides an avenue for an ultrasensitive label-free electrochemical detection of DA and UA.

Molybdenum–Based Electrocatalysts for Direct Alcohol Fuel Cells: A Critical Review

&lt;p&gt;Direct alcohol fuel cells (DAFCs) have gained much attention as promising energy conversion devices due to their ability to utilize alcohol as a fuel source. In this regard, Molybdenum-based electrocatalysts (Mo-ECs) have emerged as a substitution for expensive Pt and Ru–based co-catalyst electrode materials in DAFCs, owing to their unique electrochemical properties useful for alcohol oxidation. The catalytic activity of Mo-ECs displays an increase in alcohol oxidation current density by several folds to 1000–2000 mA mg&lt;sub&gt;Pt&lt;/sub&gt;&lt;sup&gt;−1&lt;/sup&gt;, compared to commercial Pt and PtRu catalysts of 10–100 mA mg&lt;sub&gt;Pt&lt;/sub&gt;&lt;sup&gt;−1&lt;/sup&gt;. In addition, the methanol oxidation peak and onset potential have been significantly reduced by 100–200 mV and 0.5–0.6 V, respectively. The performance of Mo-ECs in both acidic and alkaline media has shown the potential to significantly reduce the Pt loading. This review aims to provide a comprehensive overview of the bifunctional mechanism involved in the oxidation of alcohols and factors affecting the electrocatalytic oxidation of alcohol, such as synthesis method, structural properties, and catalytic support materials. Furthermore, the challenges and prospects of Mo-ECs for DAFCs anode materials are discussed. This in-depth review serves as valuable insight toward enhancing the performance and efficiency of DAFC by employing Mo-ECs.&lt;/p&gt;

Integration of Riboflavin-Modified Carbon Fiber Mesh Electrode Systems in a 3D-Printed Catheter Hub.

Catheter line infection is a common complication within clinical environments, and there is a pressing need for technological options to aid in reducing the possibility of sepsis. The early identification of contamination could be pivotal in reducing cases and improving outcomes. A sensing rationale based on a riboflavin-modified electrode system integrated within a modified 3D-printed catheter needle-free connector is proposed, which can monitor changes in pH brought about by bacterial contamination. Riboflavin, vitamin B2, is a biocompatible chemical that possesses a redox-active flavin core that is pH dependent. The oxidation peak potential of the adsorbed riboflavin responds linearly to changes in pH with a near-Nernstian behavior of 63 mV/pH unit and is capable of accurately monitoring the pH of an authentic IV infusate. The proof of principle is demonstrated with an electrode-printed hub design offering a valuable foundation from which to explore bacterial interactions within the catheter lumen with the potential of providing an early warning of contamination.

CO Oxidation Behavior of Pt/RuO2-Sphere Catalyst in Acidic Electrolyte

Polymer electrolyte fuel cells (PEFCs) are one of the candidates for the next-generation power source. PtRu alloy catalyst is used as an anode catalyst because it has high CO poisoning tolerance. It is well known that PtRu alloy has high CO poisoning tolerance because of the bifunctional mechanism and the ligand effects of the Ru atom working as the co-catalyst. However, the Ru atom dissolves during the operation of PEFCs, such as start-up/shut-down, and then the CO poisoning tolerance becomes low. The author reported using ruthenium oxide nanosheet (RuO2ns) acted as high stable co-catalyst [1]. The composition catalyst of traditional Pt/C and RuO2ns (RuO2-Pt/C) showed high CO poisoning tolerance and long life. But the high CO poisoning tolerance site in the RuO2ns-Pt/C catalyst was limited to the very close position of Pt nanoparticles and RuO2ns. Thus, the CO poisoning tolerance was uneven, even within the same catalyst. On the other hand, we reported that new catalyst support with the sphere shape composited by the reduced graphene oxide wall provided high substance diffusion and Pt utilization rate [2]. It is expected that the spherical catalyst support composed from the RuO2ns wall provides complete contact with Pt nanoparticles and not only exquisite CO poisoning tolerance but also high Pt utilization. In this study, the new spherical catalyst support with the RuO2ns wall was synthesized and supported Pt nanoparticles, and its CO oxidation ability was evaluated by CO stripping voltammetry. The spherical catalyst support (RuO2-sphere) was composed of a SiO2 bead as a core and the RuO2ns wall, and its synthesis method was similar to the previous work [2]. Concretely, this study changed the wall material from graphene oxide to RuO2ns. And the Pt complex adsorbing on a RuO2-sphere was reduced by heating reflux with hydrazine at 100°C and 24 hours in ethanol solvent. After water washing, Pt-supported RuO2-sphere (Pt/RuO2-sphere) was obtained. The morphology, crystal structure, and electron state of the Pt/RuO2-sphere were evaluated by SEM, XRD, and XPS, respectively.A three-electrode cell, which is composed of a working electrode, Pt counter, Ag/AgCl reference electrode, and 0.1 M HClO4 electrolyte, was used for the electrochemical measurements, and the measurement temperature was 60°C. This study converted the potentials from Ag/AgCl reference to RHE reference. The CO stripping voltammetry was conducted in the following steps. CO gas was introduced had flowed into the electrolyte for two minutes to adsorb on the metal surface while its potential was kept at 0.05 V. The inert gas purged out excess CO gas in the electrolyte for 30 minutes. And then, the potential was swept to 1.2 V at 10 mV s-1. SEM images of the Pt/RuO2-sphere showed about 500 nm sphere of RuO2-sphere and a few nanometer sizes of Pt particles. Results of XRD and XPS suggested that Pt particles were mainly metallic state and not alloying with Ru. In addition, Ru valence in Pt/RuO2-sphere was predicted at quadrivalent. The cyclic voltammogram of the Pt/RuO2-sphere had characteristic peaks attributed to both Pt and RuO2ns. Specifically, the redox peaks below 0.4 V and at 0.8V-1.2V could be assigned the hydrogen adsorption/desorption and redox of the Pt surface, respectively. In addition, the unique redox peaks of RuO2ns were also observed around 0.6 V. The estimated on-set potential of the CO oxidation peak in the Pt/RuO2-sphere was at 0.36 V, and this value was superior to that of traditional Pt/C and near that of PtRu/C. The CO oxidation peak of the Pt/RuO2-sphere was sharply compared to the composite catalyst of Pt/C and RuO2ns in previous work. This change in peak shape was thought to be attributed to the expansion of the contact sites between the Pt nanoparticles and the RuO2ns surface.Developed Pt/RuO2-sphere catalyst, which had the RuO2ns wall and spherical shape, showed high CO poisoning catalyst as well as PtRu/C.[1] T. Saida, et al., Electrochim. Acta, 55, 857–864 (2010).[2] T. Saida, et al., Energy & Fuels, 36, 1027-1033 (2022).