Electrochemical Quantification Research Articles

In situ continuous electrochemical quantification of bacterial adhesion to electrically polarized metallic surfaces under shear.

Biofouling creates significant human and economic losses through infections, corrosion, and drag losses on ships and in oil and food distribution pipelines. Organisms adhered to these surfaces contend with high shear rates and are actively transported to the surface. The metallic surfaces to which these organisms are adhered also conduct charge at various potentials, and the effects of surface charge on adhesion rates are little addressed in the literature. We demonstrate that mass-transport limiting current, chronoamperometry, and cyclic voltammetry can be combined to provide resulting adhesion rates similar to those in the literature. Furthermore, we demonstrate that rotating disk electrodes can be used to study adhesion of bacteria to electrically polarized metallic surfaces under shear. We study the adhesion of Escherichia coli, Bacillus subtilis, and 1μm silica microspheres over a range of shear stress from 0.15 to 37 dyncm-2 or shear rates of 14.7-3730 s-1. Unlike quartz-crystal microbalance, our methodology measures changes in the area instead of mass, simultaneously providing measurements of the protein binding. Our deposition rates agree with those found using optical systems. However, unlike optical systems, our methods apply to a wider range of materials than on-chip flow devices.

Electrochemical quantification of biomarker myeloperoxidase.

Point of care testing (PoCT) devices permit precise and rapid detection of disease-related biomarkers contributing to an early disease diagnosis and administration of an appropriate treatment. The enzyme myeloperoxidase (MPO) is a relevant biomarker for infection and inflammation events assessment; however its direct electrochemical quantification is hindered by the limited accessibility to the iron atom in its active center. Herein, such hindrance of the MPO biomolecule is overcome using the redox mediator 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The charge involved in the electrochemical reduction of the MPO-oxidized ABTS is correlated with the concentration of MPO. The use of ABTS allowed for the electrochemical assessment of a wide range of MPO concentrations (10-1000nM) including those reported for wound infections, chronic obstructive pulmonary disease and early adverse cardiac events. The developed electroanalytical approach is rapid and inexpensive, and thus suitable for implementation in PoCT devices.

Electrochemical Sensing of the Peptide Drug Exendin-4 Using a Versatile Nucleic Acid Nanostructure.

Although endogenous peptides and peptide-based therapeutics are both highly relevant to human health, there are few approaches for sensitive biosensing of this class of molecules with minimized workflow. In this work, we have further expanded on the generalizability of our recently developed DNA nanostructure architecture by applying it to electrochemical (EC) peptide quantification. While DNA-small molecule conjugates were used in a prior work to make sensors for small molecule and protein analytes, here DNA-peptide conjugates were incorporated into the nanostructure at the electrode surfaces, and antibody displacement permitted rapid peptide sensing. Interestingly, multivalent DNA-peptide conjugates were found to be detrimental to the assay readout, yet these effects could be minimized by solution-phase bioconjugation. The final biosensor was validated for quantifying exendin-4 (4.2 kDa)─a human glucagon-like peptide-1 receptor agonist important in diabetes therapy─for the first time using EC methods with minimal workflow. The sensor was functional in 98% human serum, and the low nanomolar assay range lies between the injected dose concentration and the therapeutic range, boding well for future applications in therapeutic drug monitoring.

Electrochemical Surface Area Quantification, CO2 Reduction Performance, and Stability Studies of Unsupported Three-Dimensional Au Aerogels versus Carbon-Supported Au Nanoparticles.

The efficient scale-up of CO2-reduction technologies is a pivotal step to facilitate intermittent energy storage and for closing the carbon cycle. However, there is a need to minimize the occurrence of undesirable side reactions like H2 evolution and achieve selective production of value-added CO2-reduction products (CO and HCOO–) at as-high-as-possible current densities. Employing novel electrocatalysts such as unsupported metal aerogels, which possess a highly porous three-dimensional nanostructure, offers a plausible approach to realize this. In this study, we first quantify the electrochemical surface area of an Au aerogel (≈5 nm in web thickness) using the surface oxide-reduction and copper underpotential deposition methods. Subsequently, the aerogel is tested for its CO2-reduction performance in an in-house developed, two-compartment electrochemical cell. For comparison purposes, similar measurements are also performed on polycrystalline Au and a commercial catalyst consisting of Au nanoparticles supported on carbon black (Au/C). The Au aerogel exhibits a faradaic efficiency of ≈97% for CO production at ≈−0.48 VRHE, with a suppression of H2 production compared to Au/C that we ascribe to its larger Au-particle size. Finally, identical-location transmission electron microscopy of both nanomaterials before and after CO2-reduction reveals that, unlike Au/C, the aerogel network retains its nanoarchitecture at the potential of peak CO production.

Electrochemical quantification of mancozeb through tungsten oxide/reduced graphene oxide nanocomposite: A potential method for environmental remediation

The extensive use of pesticides for better yield of crops have become major human concern over the decades. Pesticides are widely used in the fields to kill weeds and pests on the vegetable and crops to improve the quality and yield of the food knowing the fact that pesticides residue in food are very lethal for human being. Amongst, the hazardous pesticides, mancozeb is widely applied in the protection of crops. Thus the quantification of mancozeb residue is of great importance. This study reports the electrochemical monitoring of mancozeb through tungsten oxide reduced graphene oxide (WO3/rGO) nanocomposite. The engineered nanocomposite was characterized though different analytical tools such as FTIR, XRD and TEM to examine crystallinity, internal texture and the size. The FTIR result confirm the functionalities of GO and WO3/rGO nanocomposite in finger print and functional group region. Through XRD analysis, the size of the WO3/rGO nanocomposite was calculated as 31.6 nm. While the TEM analysis was also exploited to examine the 2D texture of GO and nanometric size of the WO3/rGO. To ensure the conductive nature of the WO3/rGO nanocomposite, the glassy carbon electrode was modified and exploited for cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the modified sensor showed exceptional response for mancozeb. The linear dynamic range was set from 0.05 to 70 μM in BRB buffer of pH 4. The LOD and LOQ for proposed method was calculated as 0.0038 and 0.0115 μM. The analytical applicability of chemically modified sensor was investigated in real matrix of different vegetable samples and the recovery values were observed in acceptable range. The electrochemical examination of present work reveals that WO3/rGO nanocomposite can be an exceptional aspirant for the determination of mancozeb at commercial level.

Innovative Non-Enzymatic Electrochemical Quantification of Cholesterol.

The use of the Liebermann–Burchard reaction in this study has been explored in the development of a simple, reliable, and robust quantitative electrochemical method to assay cholesterol, and hence provide a good alternative to colorimetric methods. The optimization of batch mode operation for electrochemical oxidation of cholesterol in the Liebermann–Burchard reagents included the applied potential and acidic volume. Tested using chronoamperometry, the developed method showed a high sensitivity (14.959 μA mM−1) and low detection limit (19.78 nM) over a 0.025–3 mM concentration range, with remarkable linearity (R2 = 0.999), proving an analytical performance either higher or comparable to most of the cholesterol sensors discussed in literature. The influence of possible interfering bioactive agents, namely, glucose, uric acid, ascorbic acid, KCl and NaCl, has been evaluated with no or negligible effects on the measurement of cholesterol. Our study was directed at finding a new approach to chemical processing arising from the use of external potential as an additional level of control for chemical reactions and the transfer of electrons between surfaces and molecules. Finally, the optimized method was successfully applied for the determination of cholesterol content in real blood samples.

Electrochemical Analysis of Liposome‐encapsulated Colistimethate Sodium

AbstractIn this study, the neutral and cationic liposomal formulations of Colistimethate sodium (CMS), an antibiotic for multi‐drug resistant gram‐negative bacteria, were prepared and electrochemical quantification of CMS from these liposomes were achieved. This is the first study of the electrochemical detection of CMS released from liposomes. First, the electrochemical properties of CMS were analysed, then the encapsulation efficiency, and the release kinetic of CMS from liposomes were determined with Differential Pulse Voltammetry (DPV) measurements. In addition, Cyclic Voltammetry were applied to determine oxidation signal of CMS. A higher encapsulation efficiency was found in the cationic liposome compared to the neutral liposome. Moreover, CMS was controlled released from liposomes with zero‐order drug release kinetics.

Electrochemical determination of (S)-7-hydroxywarfarin for analysis of CYP2C9 catalytic activity

An electrochemical method for the quantitative determination of (S)-7-hydroxywarfarin as a metabolite of the vitamin K antagonist warfarin has been developed to analyze the catalytic activity of cytochrome P450 2C9 (CYP2C9). The electrochemical properties of (S)-7-hydroxywarfarin were investigated using screen-printed carbon electrodes. We have shown by cyclic voltammetry that irreversible (S)-7-hydroxywarfarin electrochemical oxidation, in contrast to (S)-warfarin, can be registered by an oxidation peak at approximately 0.6 V (vs. Ag pseudo-reference electrode). A linear dependence of the oxidation peak amplitude in the range of 0.57–0.61 V on (S)-7-hydroxywarfarin concentration (in the range of 0.1–1 μM) was shown by the square-wave voltammetry method. The limit of (S)-7-hydroxywarfarin detection and the sensitivity were calculated as 0.091 μM and 0.0075 A/M, respectively. Using an electrochemical system based on recombinant human CYP2C9 immobilized on screen-printed carbon electrodes modified by didodecyldimethylammonium bromide, we have shown the possibility of (S)-7-hydroxywarfarin electrochemical quantification without separation of the enzymatic system component. The (S)-7-hydroxywarfarin quantitative electrochemical determination was used to calculate the kinetic parameters of CYP2C9 immobilized on electrode toward (S)-warfarin: the values of the maximal reaction rate (Vmax) and the Michaelis constant (KM) were calculated as 0.1 ± 0.002 min−1 and 3.03 ± 0.38 μM, respectively. The usage of an enzymatic CYP2C9-containing electrode as a catalyst and an indicator electrode as a sensor for the formation of metabolite allows to effectively register the kinetic parameters of the process. Such a two-electrode system can be applied to assess drug-drug interactions.

Voltammetric and impedimetric determinations of selenium(iv) by an innovative gold-free poly(1-aminoanthraquinone)/multiwall carbon nanotube-modified carbon paste electrode.

Selenite (Se4+), a significant source of water pollution above the permissible limits, is considered a valuable metal by environmentalists. In this study, we described a novel electrochemical sensor that utilized a carbon paste electrode (CPE) that was modified using multiwall carbon nanotubes (MWCNTs) and poly(1-aminoanthraquinone) (p-AAQ) for finding Se4+ in water samples. Electrochemical quantification of Se4+ depends on the formation of a selective complex (piaselenol) with p-AAQ. In this work, we prepared a CPE modified by physical embedding of MWCNTs and 1-aminoanthraquione (AAQ), while the polymer film was formed by anodic polymerization of AAQ by applying a constant potential of 0.75 V in 0.1 M HCl for 20 s followed by cyclic voltammetry (CV) from −0.2 to 1.4 V for 20 cycles. The modified CPE was used for differential pulse voltammetry (DPV) of Se4+ in 0.1 M H2SO4 from 0 to 0.4 V with a characteristic peak at 0.27 V. Further, the proposed sensor was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy (EIS). The analytical conditions regarding the electrode performance and voltammetric measurements were optimized, with the accumulation time and potential, supporting electrolyte, differential-pulse period/time, and amplitude. The EIS results indicated that the p-AAQ/MWCNTs-modified CPE sensor (p-AAQ/MWCNTs/CPE) that also exhibited low charge-transfer resistance (Rct) toward the anodic stripping of Se4+, exhibited good analytical performance toward different concentrations of Se4+ in a linear range of 5–50 μg L−1 Se4+ with a limit of determination (LOD) of 1.5 μg L−1 (3σ). Furthermore, differential-pulse voltammetry was employed to determine different concentrations of Se4+ in a linear range of 1–50 μg L−1 Se4+, and an LOD value of 0.289 μg L−1 was obtained. The proposed sensor demonstrated good precision (relative standard deviation = 4.02%) at a Se4+ concentration of 5 μg L−1. Moreover, the proposed sensor was applied to analyze Se4+ in wastewater samples that were spiked with Se, and it achieved good recovery values.

Electrochemical quantification of sulfamethoxazole antibiotic in environmental water using zeolitic imidazolate framework (ZIF)-derived single-atom cobalt catalyst in nitrogen-doped carbon nanostructures

An electrochemical sensor based on single-atom cobalt-anchored nitrogen-doped carbon catalysts is developed to quantify sulfamethoxazole in environmental water samples.

Triazole-tethered naphthalimide-ferrocenyl-chalcone based voltammetric and potentiometric sensors for selective electrochemical quantification of Copper(II) ions

• A ferrocene based TNFC was synthesized and found sensitive towards Cu 2+ . • UV, fluorescence, DFT, NMR and HRMS studies confirmed binding of TNFC with Cu 2+ . • TNFC exhibited voltammetric response towards Cu 2+ with LOD 0.09 µM. • TNFC -CPE showed a Nernstian slope of 30.0 mV/decade with LOD 0.79 µM. • TNFC -CPE was successfully applied for estimation of Cu 2+ in water and milk products. A triazole-tethered naphthalimide-ferrocenyl-chalcone ( TNFC ) derivative was synthesized and investigated for its electrochemical behavior with subsequent successful application as a receptor for the development of differential pulse voltammetric (DPV) and potentiometric sensors for quantification of Cu 2+ after receiving confirmatory evidences from UV–Vis, Fluorescence and DFT studies. Cyclic voltammogram of TNFC exhibited two redox peaks at +0.51 V and +0.59 V corresponding to ferrocene/ferrocenium ion redox couple in the potential range of 0–1.0 V vs Ag/Ag + . On addition of Cu 2+ , Cyclic voltammogram of TNFC shifted toward more positive potential (anodic shift), indicating the formation of TNFC -Cu 2+ complex. DPV sensor demonstrated a selective response towards Cu 2+ in the concentration range of 0–26 µM with detection limit of 0.09 µM. The TNFC modified carbon paste electrode (CPE) exhibited a selective response for Cu 2+ with Nernstian slope of 30.0 mV/decade in the concentration range of 1.0 × 10 −6 −1.0 × 10 −1 M and detection limit 0.79 µM. High binding constant (3.2 × 10 4 M −1 ) and negative value of Gibbs free energy (−25.69 kJmol −1 ) calculated using Benesi-Hildebrand (BH) equation confirmed the favorable complexation between TNFC and Cu 2+ which was also validated using 1 H NMR and mass spectrometry. The proposed TNFC- CPE was successfully utilized for quantification of Cu 2+ content in real samples of water and milk products.

In situ silver nanoparticle coating of virions for quantification at single virus level.

In situ labelling and encapsulation of biological entities, such as of single viruses, may provide a versatile approach to modulate their functionality and facilitate their detection at single particle level. Here, we introduce a novel virus metallization approach based on in situ coating of viruses in solution with silver nanoparticles (AgNP) in a two-step synthetic process, i.e. surface activation with a tannic acid - Sn(II) coordination complex, which subsequently induces silver ion (I) reduction. The metalic coating on the virus surface opens the opportunity for electrochemical quantification of the AgNP-tagged viruses by nano-impact electrochemistry on a microelectrode with single particle sensitivity, i.e. enable the detection of particles oherwise undetectable. We show that the silver coating of the virus particles impacting the electrode can be oxidized to produce distinct current peaks the frequency of which show a linear correlation with the virus count. The proof of the concept was done with inactivated Influenza A (H3N2) viruses resulting in their quantitation down to the femtomolar concentrations (ca. 5 × 107 particles per mL) using 50 s counting sequences.

Rapid electrochemical quantification of trace Hg2+ using a hairpin DNA probe and quantum dot modified screen-printed gold electrodes.

Rapid, simple, sensitive and specific approaches for mercury(ii) (Hg2+) detection are essential for toxicology assessment, environmental protection, food analysis and human health. In this study, a ratiometric hairpin DNA probe based electrochemical biosensor, which relies on hairpin DNA probes conjugated with water-soluble and carboxyl functionalized quaternary Zn–Ag–In–S quantum dot (QD) on screen-printed gold electrodes (SPGE), referred to as the HP-QDs-SPGE electrochemical biosensor in this study, was developed for Hg2+ detection. Based on the “turn-off” reaction of a hairpin DNA probe binding with a mismatched target and Hg2+ through the formation of T–Hg2+–T coordination, the HP-QDs-SPGE electrochemical biosensor can rapidly quantify trace Hg2+ with high ultrasensitivity, specificity, repeatability and reproducibility. The conformational change of the hairpin DNA probe caused a significant decrease in electrochemical intensity, which could be used for the quantification of Hg2+. The linear dynamic range and high sensitivity of the HP-QDs-SPGE electrochemical biosensor for the detection of Hg2+ was studied in vitro, with a broad linear dynamic range of 10 pM to 1 μM and detection limits of 0.11 pM. In particular, this HP-QDs-SPGE electrochemical biosensor showed excellent selectivity toward Hg2+ ions in the presence of other metal ions. More importantly, this biosensor has been successfully used to detect Hg2+ in deionized water, tap water, groundwater and urine samples with good recovery rate and small relative standard deviations. In summary, the developed HP-QDs-SPGE electrochemical biosensor exhibited promising potential for further applications in on-site analysis.

Synthesis and characterization of graphene nanosheets for electrochemical quantification of chlorpheniramine maleate drugs using a modified glassy carbon electrode

The development of innovative sensors for the detection of analytes at extremely low concentrations with great sensitivity and selectivity has been a major focus of this study. The electrochemical activity of chlorpheniramine maleate (CPRM) in the presence of a graphene modified GCE has been investigated. Cyclic voltammograms (CV) have been obtained in the linear dynamic range 3.5- 156 μM while the optimum pH range and the maximum peak current (IPa) have been measured at pH 7.3. The process on the electrode's surface, diffusion regulated, heterogeneous rate constant, charge transfer coefficient, and the number of electrons transferred among the physicochemical properties have been obtained. Differential pulse voltammetry (DPV) of CPRM at the modified has electrode revealed a good linear calibration curve with a linear range of 10 to 60 μM and limit of detection of 0.062 μM. The suggested sensor has been fabricated and utilized to determine CPRM in medicines as well as serum samples.

NaOH Pretreated Molybdate-Carbon Paste Electrode for the Determination of Phosphate in Seawater by Square Wave Voltammetry with Impedimetric Evaluation

Phosphate (PO4 3−) is an important nutrient for phytoplankton growth and at high loadings can result in water quality deteriorations. Autonomous PO4 3− measurements are required for monitoring purposes, and are best achieved using sensitive, portable and low-cost techniques. Here we describe a new electrochemical sensor for PO4 3− detection in seawater. The electrochemical quantification of PO4 3− typically depends on the reaction between molybdate and PO4 3− under acidic conditions to form a phosphomolybdic complex, which is electrochemically active. In this work, we prepared a carbon paste electrode (CPE) modified with molybdate and pretreated in 0.1 M NaOH using cyclic voltammetry (CV). The modified CPE was employed for the determination of PO4 3− in artificial seawater (35 g l−1 NaCl) acidified with sulfuric acid to pH 0.8. The analytical conditions, including pH, waiting time for complexation, square wave amplitude and frequency, were optimized. An additional cleaning step (cyclic voltammetry (CV)) of 10 cycles in 0.1 M NaOH at −0.5 to 0.5 V was required between PO4 3− determinations to dissolve the phosphomolybdic complex formed on the surface of the working electrode. Electrochemical impedance spectroscopy (EIS) results confirmed that the molybdate-modified CPE (molybdate/CPE) exhibited a low charge-transfer resistance (Rct) toward PO4 3−, and showed an improved analytical performance for different concentrations of PO4 3−. A calibration plot in the range of 0.01–5 μM with a limit of detection (LOD) of 0.003 μM was obtained. The proposed electrode demonstrated good precision (4.3% and 5.8%) for concentrations of 5 μM and 0.2 μM, respectively. The proposed method was employed to analyze PO4 3− in seawater samples on a research cruise in the North Sea, with results in close agreement to those obtained using conventional colorimetric measurements.

A versatile sensing platform based on FeOOH nanorod/expanded graphite for electrochemical quantification of bioanalytes

Quantitative analysis of biologically important compounds plays extraordinary roles in diagnostic studies of human health. In this study, a versatile electrochemical sensing platform is proposed for selective quantification of ascorbic acid (AA), dopamine (DA), uric acid (UA), acetaminophen (AC) and l-tryptophan (Trp). Such a platform is based on a nanocomposite of FeOOH nanorod and expanded graphite (FeOOH nanorod/EG), prepared through a hydrothermal process. The characterization of its morphology and electrochemical properties by means of microscopic methods and electrochemical techniques reveals that this nanocomposite exhibits outstanding electrocatalytic activity and sensing performance toward these bioanalytes. A combined action between EG and FeOOH is confirmed, where the former provides a huge electroactive surface area as well as a fast electron transfer rate, while the latter features strong electrical catalytic ability. This platform exhibits high sensitivity toward voltammetric quantitation of AA, DA, UA, AC and Trp, and their detection limits are 3.28, 0.22, 0.02, 0.0014 and 0.03 μM (S/N = 3), respectively. Beyond that, the proposed FeOOH nanorod/EG electrochemical sensing platform shows good selectivity, high reproducibility and stability in the quantitative analysis of these bioanalytes. The established sensing platform has been also successfully adopted in analyzing these bioanalytes in real biological serum and urine samples or commercial drugs. Consequently, the fabricated FeOOH nanorod/EG nanocomposite is a promising electrode material in the applications of sensing different bioanalytes.

Electrochemically Quantifying the Phase Transition of Cesium Lead Halide Perovskite Quantum Dots in Purification.

A good purification strategy for obtaining high-quality and low-cost perovskite QDs ink requires a complete removal of the impurities but with a minimal phase transition of QDs from the perovskite phases to the nonperovskite δ-phase. This pioneering work reports the electrochemical quantification on the phase transition level of CsPbI3 QDs in purification. Cyclic voltammetry of the purified QDs evidenced the formation of a new product in the purification process, which was demonstrated to be the undesired nonperovskite δ-phase by independent structural analysis. The developed electrochemical methodology further enabled the quantification of the extent of the phase transition of the QDs purified using different strategies by simply analyzing the charge associated with the relevant peaks and allowing optimization of the purification. The latter is of vital importance for commercialization and is an essential step for boosting their device performance.

Nitrogen-Doped Graphdiyne Quantum Dots for Electrochemical Chloramphenicol Quantification in Water

Nitrogen-Doped Graphdiyne Quantum Dots for Electrochemical Chloramphenicol Quantification in Water

Electrochemical Surface Area Quantification, CO2 Reduction Performance and Stability Studies of Au and Au-Cu Aerogels

To boost the valorization of electrochemical CO2 reduction technologies, there is a strong need for active catalysts with minimal side reactions and high specific surface areas. While the latter requirement is usually fulfilled by nanostructured catalysts, it is often realized by using porous carbon supports which improve the dispersion of nanoparticles at the cost of shifting the product selectivity towards undesirable H2.1 This problem could be circumvented by employing unsupported aerogel catalysts, which are tridimensionally interconnected nanodomain networks (e.g., nano-wires or -particles) of highly porous materials with large surface areas.2 With this consideration, and motivated by the high activity and selectivity of Au for converting CO2 to CO3 and the high economic value of CO as a reduction product,4 in the first part of the talk we will present our efforts on employing Au aerogels for CO2 electroreduction. Specifically, Au aerogels with a web thickness of ≈ 5 nm were electrochemically investigated, along with polycrystalline Au and a commercial catalyst consisting of Au nanoparticles supported on a carbon black (20 % Au/C) that provided a benchmark for comparison of our results. The electrochemical surface areas (ECSAs) of these materials were first quantified using the surface oxide reduction method, followed by more accurate copper underpotential deposition (Cu-UPD) measurements in aqueous H2SO4 electrolyte in a rotating disc electrode (RDE) configuration. Further, their CO2 reduction performance was assessed using an in-house developed, two compartment electrochemical cell, coupled to an online gas chromatograph for detection of gaseous products and subsequently subjected to ion chromatography (IC) analysis for liquid product quantification. Finally, to test the structural stability of all Au nanocatalysts during electrochemical conditioning and CO2 electroreduction, identical location transmission electron microscopy (IL-TEM) was employed before and after the electrochemical processes, which were conducted directly on finder TEM grids.5 We show that Au aerogels exhibit a CO faradaic efficiency (FECO) of ≈ 97% at ≈ -0.55 VRHE in 0.1 M NaHCO3, with suppressed H2 production as compared to 20% Au/C across entire potential range.Complementarily, and inspired by the prospects to alter the selectivity trends as a result of surface d-band tuning upon alloying,6 and by reports of enhanced CO2-to-CO conversion observed for Au-Cu materials,7 the second part of the talk focusses on our on-going research on CO2 reduction using Au3Cu and AuCu alloy aerogels. Firstly, the quantification of the electrochemically available surface area was carried out by lead underpotential deposition (Pb-UPD) on Au-Cu aerogels with 4-6 nm web thickness. To establish a benchmark for the ECSA results, polycrystalline Au, Au aerogel and polycrystalline Cu were also subjected to Pb-UPD measurements. Similar to the Au aerogel, the alloys were next assessed for their CO2 reduction performance at various potentials and were compared with the baseline established by Au aerogels. Following this, IL-TEM was used to determine if the alloy aerogel nanostructure undergoes drastic changes during the process of CO2 electroreduction. Au3Cu aerogels show a shift in CO selectivity to lower CO2 reduction overpotentials, with a peak FECO of ≈ 97% at ≈ -0.4 VRHE in 0.5 M KHCO3.In summary, this contribution will present a detailed electrochemical study of the applicability of aerogel catalysts for CO2 reduction, including a comparison with well-documented polycrystalline and commercial catalysts and outlining the effects of alloying on the activity and stability of these materials. References O.A. Baturina et al., ACS Catalysis 2014, 4, 3682.B. Cai et al., Adv. Energy Mater. 2013, 3, 839.Y. Hori et al., Electrochim. Acta 1994, 39, 1833.J. Durst et al., CHIMIA 2015, 69, 769.K. Schlögl et al., J. Electroanal. Chem. 2011, 662, 355.K. Liu et al., ACS applied materials & interfaces, 2019, 11, 16546-16555.D. Kim et al., Nat. comm. 2014, 5, 1-8.

Mesoporous onion-like carbon nanostructures from natural oil for high-performance supercapacitor and electrochemical sensing applications: Insights into the post-synthesis sonochemical treatment on the electrochemical performance

Although onion-like carbon nanostructures (OLCs) are attractive materials for energy storage, their commercialization is hampered by the absence of a simple, cost-effective, large-scale synthesis route and binder-free electrode processing. The present study employs a scalable and straightforward technique to fabricate sonochemically tailored OLCs-based high-performance supercapacitor electrode material. An enhanced supercapacitive performance was demonstrated by the OLCs when sonicated in DMF at 60 °C for 15 min, with a specific capacitance of 647 F/g, capacitance retention of 97% for 5000 cycles, and a charge transfer resistance of 3 Ω. Furthermore, the OLCs were employed in the electrochemical quantification of methylene blue, a potential COVID-19 drug. The sensor demonstrated excellent analytical characteristics, including a linear range of 100 pM to 1000 pM, an ultralow sensitivity of 64.23 pM, and a high selectivity. When used to identify and quantify methylene blue in its pharmaceutical formulation, the sensor demonstrated excellent reproducibility, high stability, and satisfactory recovery.