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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]

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]

The behavior of Praja1 (PJA1) interacting with alpha-synuclein (α-Syn) on a gold electrode was investigated using electrochemical methods, where both PJA1 and α-Syn are intrinsically disordered proteins. From the electrode reaction of ferricyanide ions added as probe, it was suggested that PJA1 interacts with α-Syn even when adsorbed on gold substrate and that the state of PJA1 on gold electrodes can be classified into four categories depending on the α-Syn concentration. [ABSTRACT FROM AUTHOR]

The conductance of a tunneling electron through a π-conjugated molecule may be affected by the presence of different pathways in the orbital structure of the molecule, resulting in the constructive or destructive interference of the molecular wave function. This quantum interference (QI) directly translates into enhancement or suppression of conductance and offers the possibility of controlling this phenomenon through tailored synthesis. Hence, we set up synthetic methodologies to access a series of thiophene-fused helicenes with a well-defined positioning of the sulfur atoms, which control the occurrence of conducting, linearly conjugated as well as disrupted, cross-conjugated pathways. We describe these synthetic strategies and relate the expected electronic transport through our molecules to three key variables: a) the exo-/endo-topology of the S atom within the ring; b) the parity (odd/even) of the overall number of rings conforming to the helicene; and c) the size of the circuit. This series ranks from [7] to [11] fused rings, having both exo-, endo-, or mixed exo-endo-topology. Comparison of homologous dithiahelicenes with size-tunable highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energies allows us to isolate the key variable of the bond topology from other electronic properties and face the study of QI in helically conjugated molecules. Understanding and tuning the conductance in such molecular solenoids is the main purpose of this work. [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]

In this study, we synthesized four bifunctional compounds containing two alkoxy groups, at which reactive thiol groups were introduced. Among these compounds, a compound with four and five methylene units in each alkyl chain did not exhibit a liquid crystalline phase. The other three compounds exhibit one or two liquid crystalline phases, and the number of liquid crystalline phases depends on the number of methylene units in their alkyl chains. These liquid crystalline compounds were oriented in one direction using a rubbed alignment film, and the oriented compounds were transferred onto a gold substrate. Using these gold substrates as working electrodes, cyclic voltammetry (CV) was performed with potassium ferricyanide as the redox probe. As the deposition time increased, the current intensities of a pair of redox waves gradually decreased. This trend suggests that with longer deposition times, a larger amount of the liquid crystalline compound was transferred to the gold substrate surface. These findings shed light on the relationship among the structures of bifunctional compounds, their liquid crystalline behavior, and their alignment properties on gold substrates, thereby offering valuable insights for potential applications in nanotechnology and materials science. [ABSTRACT FROM AUTHOR]

Abstract 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.

In this work, the diamine oxidase (DAO) produced from pea seedlings was partially purified using ammonium sulphate precipitation, dialysis, and gel filtration chromatography. Partially purified DAO was immobilized covalently with the help of a cross-linker glutaraldehyde onto the chitosan- modified gold electrode. The properties of immobilized enzyme were evaluated by optimum pH, optimum temperature, activity recovery, and recyclability using putrescine dihydrochloride as substrate. After immobilization of DAO, optimum pH ranges from 6.0 to 7.0 did not change and optimum temperature of enzyme changed from 34 to 38°C in comparison to free DAO. The immobilized DAO preserved 81% activity of free DAO and permitted increased stability and reusability of the enzyme than its native form. After 15 cycles of usage, the immobilized DAO maintained around 51% of its original activity, and this activity prolonged for 30 days at 4°C. [ABSTRACT FROM AUTHOR]

This paper was aimed to modify gold electrode surface with a BODIPY derivative and to examine its electrochemical behavior on the modified surface. Firstly, a BODIPY derivative including azido terminal was synthesized and characterized with several techniques such as NMR, FT-IR, element analysis and melting point. For the electrochemical studies, a triple electrode system was applied, with Gold electrode, Ag/AgCl (in aqueous medium) or Ag/Ag+ (in non-aqueous medium) and a Pt wire. The modified surface has been characterized using different electrochemical techniques. Then, the morphologies of the bare and modified electrode surfaces were evaluated with Scanning Electron Microscopy and Atomic Force Microscope. The metal adsorption property of the modified surface was investigated by using a copper solution. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of bio‐based 5‐hydroxymethylfurfural (HMF) results in 2,5‐furandicarboxylic acid (FDCA), which is a renewable and environmentally friendly alternative to terephthalic acid. Using a gold electrode, we compare the electrochemical oxidation of the aldehyde and alcohol functionality in HMF to the isolated functionalities represented by ethanol and acetaldehyde. Thereby, we investigate the effect of the inert furan ring on the electrochemical reaction. The linear sweep voltammogram (LSV) of HMF in a weakly adsorbing electrolyte differs only marginally from the superposition of LSVs obtained in ethanol and acetaldehyde containing electrolytes. However, in the presence of strong adsorbates, only the kinetics of ethanol and acetaldehyde oxidation but not of HMF oxidation are hampered. We assign this to a stronger adsorption of HMF through the furan ring than through the alcohol and carbonyl functionality of ethanol and acetaldehyde. Hence, HMF is better equipped to compete for adsorption sites than aliphatic compounds. [ABSTRACT FROM AUTHOR]

Abstract The electrochemical oxidation of bio‐based 5‐hydroxymethylfurfural (HMF) results in 2,5‐furandicarboxylic acid (FDCA), which is a renewable and environmentally friendly alternative to terephthalic acid. Using a gold electrode, we compare the electrochemical oxidation of the aldehyde and alcohol functionality in HMF to the isolated functionalities represented by ethanol and acetaldehyde. Thereby, we investigate the effect of the inert furan ring on the electrochemical reaction. The linear sweep voltammogram (LSV) of HMF in a weakly adsorbing electrolyte differs only marginally from the superposition of LSVs obtained in ethanol and acetaldehyde containing electrolytes. However, in the presence of strong adsorbates, only the kinetics of ethanol and acetaldehyde oxidation but not of HMF oxidation are hampered. We assign this to a stronger adsorption of HMF through the furan ring than through the alcohol and carbonyl functionality of ethanol and acetaldehyde. Hence, HMF is better equipped to compete for adsorption sites than aliphatic compounds.

This paper describes the first application of a covalently attached carbon nanotube film to the nanostructured gold electrode for the electrochemical detection of hydrogen peroxide. The electrodes were made by diazonium salt grafting to the gold surface with the subsequent attachment of carbon nanotubes using a low-temperature synthesis method. The introduction of properly aligned carbon nanotubes significantly increased the electroactive surface area and the current response. Covalent bonding of the nanotubes to gold resulted in a very high stability of the signal under the oxidative conditions. After 540 h of exposure to a high oxidative potential, the current response remained stable, having negligible deviations between the runs. Hydrogen peroxide detection involves an indirect enzyme-free oxidation mechanism, allowing for analysis at low potentials. The use of such a mechanism allows for classifying the system as a fourth-generation H2O2 sensor. Because of the low working potential, a 20-fold excess of fructose, creatinine, dopamine, uric acid, citric acid, and ascorbic acid did not interfere with hydrogen peroxide detection. The presence of functional groups on the carbon nanotube surface provides possibilities for simple functionalization. As an example, the fabricated electrodes were successfully modified with glucose oxidase for glucose quantification. [ABSTRACT FROM AUTHOR]

Redox-active polymers have garnered significant attention as promising materials for redox capacitors, which are energy-storage devices that rely on reversible redox reactions to store and deliver electrical energy. Our focus was on optimizing the electrochemical performance in the design and synthesis of redox-active polymer electrodes. In this study, a redox-active polymer was prepared through step-by-step synthesis on a gold electrode. To achieve this, we designed an automatic sequential polymerization equipment that minimizes human intervention and enables a stepwise polymerization reaction. The electrochemical properties of the polymer gold electrodes were investigated. The degree of polymerization of the polymer grown on the gold electrode can be controlled by adjusting the cycle of the sequential operation. As the number of cycles increases, the amount of accumulated charge increases proportionally, indicating the potential for enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disease with only late-stage detection; thus, diagnosis is made when it is no longer possible to treat the disease, only its symptoms. Consequently, this often leads to caregivers who are the patient's relatives, which adversely impacts the workforce along with severely diminishing the quality of life for all involved. It is, therefore, highly desirable to develop a fast, effective and reliable sensor to enable early-stage detection in an attempt to reverse disease progression. This research validates the detection of amyloid-beta 42 (Aβ42) using a Silicon Carbide (SiC) electrode, a fact that is unprecedented in the literature. Aβ42 is considered a reliable biomarker for AD detection, as reported in previous studies. To validate the detection with a SiC-based electrochemical sensor, a gold (Au) electrode-based electrochemical sensor was used as a control. The same cleaning, functionalization and Aβ1–28 antibody immobilization steps were used on both electrodes. Sensor validation was carried out by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) aiming to detect an 0.5 µg·mL−1 Aβ42 concentration in 0.1 M buffer solution as a proof of concept. A repeatable peak directly related to the presence of Aβ42 was observed, indicating that a fast SiC-based electrochemical sensor was constructed and may prove to be a useful approach for the early detection of AD. [ABSTRACT FROM AUTHOR]

Chloride and bromide are two of the most abundant anions found in seawater, and knowledge of their concentrations is essential for environmental monitoring. However, the analysis of chloride and bromide in seawater is challenging due to the complex nature of the seawater matrix. From an electrochemical perspective, we investigate the suitability of three types of electrode (Au, glassy carbon and Pt) for the analysis of Cl− and/or Br− in seawater. With the understanding of their electrochemical behaviours in artificial seawater (ASW), optimal voltammetric procedures for their detection are developed. The results show that the Au electrode is unsuitable for use as a Cl− and/or Br− sensor due to its dissolution and passivation in ASW. The use of glassy carbon resulted in poorly defined chloride and bromide signals. Finally, platinum was found to be a good candidate for chloride detection in artificial seawater using square wave voltammetry, and the results obtained in natural seawater via electrochemical measurement were in good agreement with those obtained via ion chromatography. Platinum electrodes are also recommended for bromide analysis. [ABSTRACT FROM AUTHOR]

Cancer is considered one of the most burdensome diseases affecting lives and, hence, the economy. Breast cancer is one of the most common types of cancer. Patients with breast cancer are divided into two groups: one group responds to the chemotherapy, and the other group resists the chemotherapy. Unfortunately, the group which resists the chemotherapy is still suffering the pain associated with the severe side effects of the chemotherapy. Therefore, there is a critical need for a method to differentiate between both groups before the administration of the chemotherapy. Exosomes, the recently discovered nano-vesicles, are often used as cancer diagnostic biomarkers as their unique composition allows them to represent their parental cells, which makes them promising indicators for tumor prognosis. Exosomes contain proteins, lipids, and RNA that exist in most body fluids and are expelled by multiple cell types, including cancer cells. Furthermore, exosomal RNA has been significantly used as a promising biomarker for tumor prognosis. Herein, we have developed an electrochemical system that could successfully differentiate between MCF7 and MCF7/ADR depending on the exosomal RNA. The high sensitivity of the proposed electrochemical assay opens the door for further investigation that will address the other type of cancer cells. [ABSTRACT FROM AUTHOR]

A hydrogen fuel cell is a highly promising alternative to fossil fuel sources owing to the emission of harmless byproducts. However, the operation of hydrogen fuel cells requires a constant supply of highly pure hydrogen gas. The scarcity of sustainable methods of producing such clean hydrogen hinders its global availability. In this work, a noble Au-atom-decorated glassy carbon electrode (Au/GCE) was prepared via a conventional electrodeposition technique and used to investigate the generation of hydrogen from acetic acid (AA) in a neutral electrolyte using 0.1 M KCl as the supporting electrolyte. Electrochemical impedance spectroscopy (EIS), open circuit potential measurement, cyclic voltammetry (CV), and rotating disk electrode voltammetry (RDE) were performed for the characterization and investigation of the catalytic properties. The constructed catalyst was able to produce hydrogen from acetic acid at a potential of approximately −0.2 V vs. RHE, which is much lower than a bare GCE surface. According to estimates, the Tafel slope and exchange current density are 178 mV dec−1 and 7.90 × 10 − 6 A cm−2, respectively. Furthermore, it was revealed that the hydrogen evolution reaction from acetic acid has a turnover frequency (TOF) of approximately 0.11 s−1. [ABSTRACT FROM AUTHOR]

The present research article describes a newly designed sensing method for determining folic acid levels. Folic acid is a B vitamin that helps the body makes healthy new cells. It is also known as vitamin B9 or folic acid. A new folic acid biosensor was constructed based on dihydrofolic acid reductase (DHFR) immobilized on c-MWCNT/TiO2NPs modified gold electrode. Prepared titanium dioxide nanoparticles have been characterized by Transmission electron microscope (TEM), X-Ray Diffractometer (XRD), and Fourier Transform Infrared spectroscopy (FTIR). Fabricated working gold electrode (i.e. DHFR/c-MWCNTs/TiO2NPs/AuE) was characterized at various stages of its construction by Scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), FTIR, and cyclic voltammetry to confirm its fabrication. The biosensor showed an optimum response at pH 7.5 and 35 ℃ temperature. The maximum current of the constructed folic acid biosensor was due to electrons generated at 0.125 V against Ag/AgCl electrode. The proposed biosensor showed a low detection limit (11.48 nM), a wide linear range (5 nM-50 nM), a sensitivity of 0.42 μA/nM/cm², and good storage stability. Folic acid biosensor was evaluated and utilized for folic acid level quantification in serum samples of pregnant women. [ABSTRACT FROM AUTHOR]

The present research article describes a newly designed sensing method for determining folic acid levels. Folic acid is a B vitamin that helps the body makes healthy new cells. It is also known as vitamin B9 or folic acid. A new folic acid biosensor was constructed based on dihydrofolic acid reductase (DHFR) immobilized on c-MWCNT/TiO2NPs modified gold electrode. Prepared titanium dioxide nanoparticles have been characterized by Transmission electron microscope (TEM), X-Ray Diffractometer (XRD), and Fourier Transform Infrared spectroscopy (FTIR). Fabricated working gold electrode (i.e. DHFR/c-MWCNTs/TiO2NPs/AuE) was characterized at various stages of its construction by Scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), FTIR, and cyclic voltammetry to confirm its fabrication. The biosensor showed an optimum response at pH 7.5 and 35 ​°C temperature. The maximum current of the constructed folic acid biosensor was due to electrons generated at 0.125 ​V against Ag/AgCl electrode. The proposed biosensor showed a low detection limit (11.48 ​nM), a wide linear range (5 ​nM–50 ​nM), a sensitivity of 0.42 ​μA/nM/cm2, and good storage stability. Folic acid biosensor was evaluated and utilized for folic acid level quantification in serum samples of pregnant women.

Epirubicin is prescribed as an essential drug for treating breast, prostate, uterine, and gastrointestinal cancers. It has many side effects, such as heart failure, mouth inflammation, abdominal pain, fever, and shortness of breath. Its measurement is necessary by straightforward and cheap methods. The application of aptamer-based electrochemical sensors is accounted as a selective option for measuring different compounds. In this work, a thiol-modified aptamer was self-assembled on the surface of the gold electrode (AuE) boosted with carbon nano-onions (CNOs), and coupled with methylene blue (MB) as an electroactive tracker to achieve a sensitive and selective aptasensor. In the absence of the epirubicin, CNOs binds to the aptamer through a π-π interaction enhancing the MB electrochemical signal. When epirubicin binds to the aptamer, the adsorption of CNOs and MB to the aptamer is not well established, so the electrochemical signal is reduced, consequently, the epirubicin value can be measured. The prepared aptasensor demonstrated an excellent sensitivity with a curve slope of 0.36 μI/nM, and 3 nM limit of detection in the linear concentration range of 1–75 nM. The prepared aptasensor was accurately capable of measuring epirubicin in blood serum samples. [ABSTRACT FROM AUTHOR]

The present paper describes the effect of the concentration of two graphene oxides (with different oxygen content) in the modifier layer on the electrochemical and structural properties of noble metal disk electrodes used as working electrodes in voltammetry. The chemistry of graphene oxides was tested using EDS, FTIR, UV–Vis spectroscopy, and combustion analysis. The structural properties of the obtained modifier layers were examined by means of scanning electron and atomic force microscopy. Cyclic voltammetry was employed for comparative electrochemical studies. [ABSTRACT FROM AUTHOR]

In this study, the effect of halide anions on the selectivity of the CO 2 reduction reaction to CO was investigated in choline-based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO 2 RR 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 CO 2 RR 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 CO 2 RR, and its consequences on the reduction performance on such surfaces in non-aqueous electrolytes., (© 2024 The Authors. ChemistryOpen published by Wiley-VCH GmbH.)

A CA19-9 electrochemical immunosensor was constructed using a hybrid self-assembled membrane modified with a gold electrode and applied to detect real samples. Hybrid self-assembled membranes were selected for electrode modification and used to detect antigens. First, the pretreated working electrodes were placed in a 3-mercaptopropionic acid (MPA)/β-mercaptoethanol (ME) mixture for 24 h for self-assembly. The electrodes were then placed in an EDC/NHS mixture for 1 h. Layer modification was performed by stepwise dropwise addition of CA19-9 antibody, BSA, and antigen. Differential pulse voltammetry was used to characterize this immunosensor preparation process. The assembled electrochemical immunosensor enables linear detection in the concentration range of 0.05–500 U/mL of CA19-9, and the detection limit was calculated as 0.01 U/mL. The results of the specificity measurement test showed that the signal change of the interfering substance was much lower than the response value of the detected antigen, indicating that the sensor has good specificity and strong anti-interference ability. The repeatability test results showed that the relative standard deviations were less than 5%, showing good accuracy and precision. The CA19-9 electrochemical immunosensor was used for the actual sample detection, and the experimental results of the standard serum addition method showed that the RSD values of the test concentrations were all less than 10%. The recoveries were 102.4–115.0%, indicating that the assay has high precision, good accuracy, and high potential application value. [ABSTRACT FROM AUTHOR]

A gold nanoparticles transparent electrode was realized by chemical reduction. This work aims to compare the transparent gold nanoparticles electrode with a more commonly utilized gold-film-coated electrode in order to investigate its potential use as counter-electrode (CE) in dye-sensitized solar cells (DSSCs). A series of DSSC devices, utilizing I−/I3− and Co(III)/(II) polypyridine redox mediators [Co(dtb)3]3+/2+; dtb = 4,4′ditert-butyl-2,2′-bipyridine)], were evaluated. The investigation focused firstly on the structural characterization of the deposited gold layers and then on the electrochemical study. The novelty of the work is the realization of a gold nanoparticles CE that reached 80% of average visible transmittance. We finally examined the performance of the transparent gold nanoparticles CE in DSSC devices. A maximum power conversion efficiency (PCE) of 4.56% was obtained with a commercial I−/I3−-based electrolyte, while a maximum 3.1% of PCE was obtained with the homemade Co-based electrolyte. [ABSTRACT FROM AUTHOR]

Alzheimer’s disease (AD) is a neurodegenerative disease with only late-stage detection; thus, diagnosis is made when it is no longer possible to treat the disease, only its symptoms. Consequently, this often leads to caregivers who are the patient’s relatives, which adversely impacts the workforce along with severely diminishing the quality of life for all involved. It is, therefore, highly desirable to develop a fast, effective and reliable sensor to enable early-stage detection in an attempt to reverse disease progression. This research validates the detection of amyloid-beta 42 (Aβ42) using a Silicon Carbide (SiC) electrode, a fact that is unprecedented in the literature. Aβ42 is considered a reliable biomarker for AD detection, as reported in previous studies. To validate the detection with a SiC-based electrochemical sensor, a gold (Au) electrode-based electrochemical sensor was used as a control. The same cleaning, functionalization and Aβ1–28 antibody immobilization steps were used on both electrodes. Sensor validation was carried out by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) aiming to detect an 0.5 µg·mL−1 Aβ42 concentration in 0.1 M buffer solution as a proof of concept. A repeatable peak directly related to the presence of Aβ42 was observed, indicating that a fast SiC-based electrochemical sensor was constructed and may prove to be a useful approach for the early detection of AD.

• Sulfur-functionalized graphene (S-Graph) were prepared through non-thermal plasma process. • S-Graph is a novel hydrophilic graphene-based material with sulfur entities at the edge sheets. • Novel electrochemical method for simultaneous detection of TBHQ and BPA was developed. • The high affinity of gold electrode and S-Graph (strong Au−S covalent bound) made the sensor very stable. • Low-cost strategy for the quantification of BPA and TBHQ simultaneously. Electrochemical sensors based on graphene have proven to be powerful tools for detecting bisphenol A (BPA) and tert-butylhydroquinone (TBHQ) individually. There are currently no reports of these analytes being detected simultaneously. By assembling graphene-based materials on gold surfaces, it is possible to improve the charge transfer of both analytes. This study utilized non-thermal plasma-assisted synthesis with a sulfur-containing precursor to functionalize graphene (S-Graph), resulting in the fabrication of an ultrasensitive electrochemical sensor that can detect both BPA and TBHQ, simultaneously. Compared with native graphene or a traditional surface of gold electrode, S-Graph/Au retained superior electrochemical activity for both analytes that showed significantly enhanced sensing performance, including a wide linear range, with a detection limit of 13 and 54 nmol L−1 for TBHQ and BPA, respectively. The enhanced long-term storage stability, as well as reproducibility showed that S-Graph is a promising strategy for promoting the application of novel graphene-based materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Chloride and bromide are two of the most abundant anions found in seawater, and knowledge of their concentrations is essential for environmental monitoring. However, the analysis of chloride and bromide in seawater is challenging due to the complex nature of the seawater matrix. From an electrochemical perspective, we investigate the suitability of three types of electrode (Au, glassy carbon and Pt) for the analysis of Cl− and/or Br− in seawater. With the understanding of their electrochemical behaviours in artificial seawater (ASW), optimal voltammetric procedures for their detection are developed. The results show that the Au electrode is unsuitable for use as a Cl− and/or Br− sensor due to its dissolution and passivation in ASW. The use of glassy carbon resulted in poorly defined chloride and bromide signals. Finally, platinum was found to be a good candidate for chloride detection in artificial seawater using square wave voltammetry, and the results obtained in natural seawater via electrochemical measurement were in good agreement with those obtained via ion chromatography. Platinum electrodes are also recommended for bromide analysis.

[Display omitted] • First comparative report on the electrochemical behavior of NAR using unmodified electrodes. • Selective and sustainable electroanalytical method for detecting NAR. • Linear range of 1.36 to 19.1 mg L-1 (LOD 0.11 mg L-1) for GCE. • Electronic structure of NAR probed using B3LYP/Def2-TZVPPD calculations alongside Fukui and dual descriptor analyses. • Cost-effective strategy for electroanalysis of pharmaceutical formulations. Naringenin (NAR) is a versatile herbal flavonoid known for its broad pharmacological benefits, including antioxidant, anti-inflammatory, and anticancer properties. These properties underscore its potential and necessity for industrial applications within the pharmaceutical sector, making its detection and quantification crucial for ensuring the quality and efficacy of pharmaceutical products. Addressing the imperative for a sensitive and sustainable screening approach, this research leverages electrochemical analysis techniques including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). Complementary to experimental investigations, the electronic structure of NAR was probed using B3LYP/Def2-TZVPPD calculations alongside Fukui and dual descriptor analyses. Our findings delineate the dissociation kinetics of the hydroxyl groups within NAR, with particular emphasis on the phenolic group's proton as the primary dissociation site, elucidating pivotal insights into the oxidation mechanism of NAR. Noteworthy is the irreversibility of the electrochemical oxidation process observed on both non-modified glassy carbon electrode (GCE) and gold electrode (GE), indicating a one-electron-one-proton mechanism. Utilizing the external calibration method and GCE, a linear range from 1.36 to 19.1 mg L-1 in Britton-Robinson (BR) supporting electrolyte was established, exhibiting a limit of detection (LOD) of 0.11 mg L-1 (R2 = 0.9945). For GE, the standard addition calibration approach revealed one linear range, from 0.27 to 0.48 mg L-1 (LOD of 0.04 mg L-1, R2 = 0.9960). Importantly, the proposed methodologies demonstrate satisfactory selectivity against potential interferences, with intra- and inter-day precision exhibiting low relative standard deviation (RSD) values. This study introduces a simple, sensitive, stable, selective, and sustainable electroanalytical method for the detection of NAR in pharmaceutical formulations, harnessing the advantages of unmodified electrodes and rigorous experimental validation. [ABSTRACT FROM AUTHOR]

The electrochemical corrosion of a gold anode in a weakly basic aqueous solution of triethylenetetramine was studied. Scanning and transmission electron microscopy revealed the formation of a compact gold deposit on the cathode and gold nanoparticles in the electrolyte. The kinetics and mechanism of the corrosion of the gold anode were studied by gravimetry and cyclic voltammetry. The formation of colloidal gold particles in solution was established by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Herein, a series of Co III corroles with different meso -substituents were successfully functionalized on gold electrodes through self-assembled axial coordination with 4-(methylthio)pyridine (MTP) and 4-(4-methylthiobenzo)pyridine (MTPP). The surface modified gold electrode performed enhanced and tunable electrochemically catalyzed hydrogen evolution behaviors that demonstrates the tunable surface molecular engineering of CoIIIcorroles via self-assembled monolayer is an effective strategy for energy related small molecule activations. Additionally, the CoIIIcorrole with electron-withdrawing meso -substituents axially coordinated with expanded conjugation system, 4-(4-methylthiobenzo)pyridine (MTPP), has the best performance of electrochemically catalyzed hydrogen evolutions. • CoIIIcorroles were successfully functionalized on gold electrodes through axially coordinated with pyridine ligands. • 4-(Methylthio)pyridine (MTP) and 4-(4-methylthiobenzo)pyridine (MTPP) with different conjugated system were tested. • The surface modified gold electrode performed enhanced and tunable electrocatalyzed hydrogen evolution behaviors. • The tunable surface molecular engineering of CoIIIcorroles via self-assembled monolayer is an effective strategy for HERs. • The CoIIIcorrole with EWG-substituents axially coordinated with expanded MTPP has the best performance of HERs. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) on Au electrode in perchloric acid and NaOH solutions were studied using an inverted rotating disc electrode (IRDE). IRDE enables investigations of gas evolution reactions in a large potential and current window. In this configuration, the electrode is not obstructed by the product gas bubbles. Potentiodynamic polarization data were acquired at various concentrations of HClO 4 and NaOH, and at a few electrode rotational speeds. At large over-potentials, diffusion-limited currents were observed in HClO 4 solutions. In the case of HER on Au in acidic media, the Volmer-Heyrovsky-Tafel (VHT) mechanism best describes the polarization results. The fractional surface area covered by adsorbed hydrogen and the rate of reaction for individual steps were estimated using the model. At low H+ concentrations, HER proceeds mainly by the Volmer-Tafel (VT) pathway while at high H+ concentrations, Heyrovsky and Tafel pathways are equally important. In the alkaline media, HER rate was found to be independent of NaOH concentration and electrode rotational speed, and the reaction mechanism could not be identified unambiguously. The results illustrate the importance of analyzing data acquired at several reactant concentrations and at a wide potential range, to identify the reaction mechanism. [Display omitted] • Inverted rotating disc electrode to study HER in large potential/current window. • HER in HClO 4 solutions limited by mass transfer of H+ ions. • At low acid concentrations, on Au, Volmer-Tafel is the main HER route. • At high acid concentration, on Au, Heyrovsky step also contributes. • HER in alkaline media independent of NaOH concentration and rotational speed. [ABSTRACT FROM AUTHOR]

This work focused on the development and optimization of an impedimetric label-free immunosensor for detecting deoxynivalenol (DON). A monoclonal antibody for DON detection was immobilized on a modified gold electrode with a cysteamine layer and polyamidoamine (PAMAM) dendrimers. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to monitor the layer-by-layer development of the immunosensor design, while electrochemical impedance spectroscopy and differential pulse voltammetry were employed to investigate the antigen/antibody interaction. The PAMAM dendrimers, allowing to immobilize a large number of monoclonal antibodies, permitted reaching, through the DPV technique, a high sensitivity and a low limit of detection equal to 1 ppb. The evaluation of the possible reuse of the immunosensors highlighted a decrease in the analytical performances of the regenerated immunosensors. After evaluating the matrix effect, the developed immunosensor was used to quantify DON in pasta samples spiked with a known mycotoxin concentration. Taking into consideration the DON extraction procedure used for the pasta samples and the matrix effect related to the sample, the proposed immunosensor showed a limit of detection of 50 ppb, which is lower than the maximum residual limit imposed by European Regulation for DON in dry pasta (750 ppb). [ABSTRACT FROM AUTHOR]

[Display omitted] • Bicarbonate reduction is an important pathway for hydrogen evolution on gold and platinum electrodes. • The rate of bicarbonate reduction is strongly dependent on mass transport. • The rate of bicarbonate reduction is strongly dependent on cations, in different ways for platinum and gold. • Bicarbonate reduction is most likely a direct reduction pathway, not mediated by solution acid-base reaction. Buffers are often employed as electrolytes for their ability to resist to pH changes. Still, they are not just spectators in the electrocatalytic processes, rather they may take a primary role. Here, we attempt to understand the mechanism of the hydrogen evolution reaction (HER) in bicarbonate-containing electrolytes on two distinct materials, Au and Pt. Keeping the bulk pH constant, voltammetric measurements reveal a promotional effect on the HER rate in the presence of bicarbonate buffer, as well as a substantial change in the reaction mechanism with a Tafel Slope in bicarbonate resembling the one in acidic media (ca. 100 and 40 mVdec−1 on Au and Pt, respectively). Nevertheless, because of the increase in surface pH due to the concomitant water reduction (2H 2 O + 2e− → H 2 + 2 OH−), bicarbonate is consumed by acid-base reactions and the bicarbonate branch of HER becomes significant only in the presence of large bulk buffer concentrations. Bicarbonate and water reduction appear intrinsically different, as they exhibit opposite dependence on the cation identity and scale differently with the specific area of the electrode. Through microkinetic modelling, we exclude that HER in bicarbonate can be explained via the generation of a proton by solution acid-base reactions. Rather, we suggest a direct bicarbonate reduction pathway, which, due to the negatively charged reactant, is strongly dependent on the cation concentration. [ABSTRACT FROM AUTHOR]

Monolayer Co(II)phthalocyanine (Co(II)Pc) functionalized gold electrodes through self-assembled axial coordination with 4-(methylthio)pyridine (MTP) and 4-(4-methylthiobenzo)pyridine (MTPP) were prepared. The surface modified gold electrode performed electrochemically catalyzed oxygen reduction in terms of onset-potential, current density, overpotential and Tafel in the order Au < Au/Co(II)Pc < Au/MTP/CoPc(II) < Au/MTPP/Co(II)Pc that demonstrates tunable surface molecular engineering of Co(II)Pc via self-assembled monolayer is an effective strategy for molecular catalysis and device application. [ABSTRACT FROM AUTHOR]

We studied the electrochemical reduction based on gold electrode of a diazonium salt prepared from ethylenediamine. This is the first time where the covalent functionalization on the gold electrode of an alkyldiazonium salt, 2-aminoethane-1-diazonium chloride, is demonstrated. This step requires the preparation beforehand by diazotization of one amine group from ethylenediamine. The resulting electrodeposited ethylamine film was confirmed by spectroscopic characterizations from gold surface modification monitored by electrochemical quartz crystal microbalance (EQCM) coupled to cyclic voltammetry (CV). The development of chemosensors based on such a covalent functionalization of a metal can reduce the chemical threats to human health along with drastically removing contaminants according to the green chemistry principles. [ABSTRACT FROM AUTHOR]

In this study, we investigated the electrochemical modification of a gold electrode using poly(L-phenylalanine) and its applicability for the quantification of resveratrol (RESV). The gold electrode was modified with L-phenylalanine employing cyclic voltammetry (CV) in aqueous solution. The detection of RESV with the modified electrode was investigated by square wave voltammetry (SWV) in a phosphate buffer solution (PBS) (pH = 1.2). The analytical calibration curve for RESV showed a linear response with concentration in the oxidation peak current range from 50 to 1000 µM, with a limit of detection (LOD) of 35.16 µM and limit of quantitation (LOQ) of 105.5 µM. The application of the prepared electrochemical sensor was carried out with a standard addition method in red wine samples.

Multicopper enzymes (MCEs) have attracted significant recent attention for use as biocathodes in enzyme-catalyzed fuel cells, mostly to facilitate the four-electron reduction of oxygen to water. Au is highly biocompatible and does not exhibit a carbon-like tendency for toxicity. Especially, the development of an implant-type enzyme fuel cells with noble electrodes, such as those made of Au, can assist in resolving health issues. In the present research, a direct electron transfer (DET)-type reaction featuring a hyperthermophilic archaeon multicopper enzyme (McoP) and a Trametes sp. laccase (Lac) adsorbed on bare Au electrodes was investigated. Quartz crystal microbalance (QCM) analysis was used to examine the adsorption behavior of McoP and Lac on Au electrodes. The obtained results indicated that the adsorbed McoP on Au exhibited stability against a higher potential electric field (+0.8 V vs. Ag|AgCl) and showed stable bioelectrocatalysis for oxygen reduction (main production of H2O2 with two-electron reaction), compared with Lac. The electron transfer rate of the McoP at the Au electrode interface was evaluated to be 10 s−1. This finding could urgently contribute for developing biocathodes in enzyme-catalyzed fuel cell, especially implant-type enzymatic fuel cells.

Epirubicin is prescribed as an essential drug for treating breast, prostate, uterine, and gastrointestinal cancers. It has many side effects, such as heart failure, mouth inflammation, abdominal pain, fever, and shortness of breath. Its measurement is necessary by straightforward and cheap methods. The application of aptamer-based electrochemical sensors is accounted as a selective option for measuring different compounds. In this work, a thiol-modified aptamer was self-assembled on the surface of the gold electrode (AuE) boosted with carbon nano-onions (CNOs), and coupled with methylene blue (MB) as an electroactive tracker to achieve a sensitive and selective aptasensor. In the absence of the epirubicin, CNOs binds to the aptamer through a π-π interaction enhancing the MB electrochemical signal. When epirubicin binds to the aptamer, the adsorption of CNOs and MB to the aptamer is not well established, so the electrochemical signal is reduced, consequently, the epirubicin value can be measured. The prepared aptasensor demonstrated an excellent sensitivity with a curve slope of 0.36 μI/nM, and 3 nM limit of detection in the linear concentration range of 1–75 nM. The prepared aptasensor was accurately capable of measuring epirubicin in blood serum samples.

Hexavalent chromium is one of the toxic heavy metals found in wastewaters from industries like electroplating, leather tanning, and steel manufacturing. The Cr(VI) removal and quantitative detection are among the major concerns from an environmental toxicity point of view. In the present work, we report an effective electrochemical technique for Cr(VI) monitoring based on the utilization of gold electrode. The technique developed is user-friendly, non-destructive, and provides real-time monitoring of Cr(VI) from wastewaters in contrast to other spectroscopic and optical techniques. The technique developed was applied in monitoring Cr(VI) removal from synthetic Cr(VI) samples using chitosan cross-linked glutaraldehyde (C + G) beads. The parameter optimization for Cr(VI) removal using C + G beads was done. The experimental data of Cr(VI) adsorption on C + G beads obtained using cyclic voltammetry were further used for kinetic and thermodynamic studies. Kinetic and thermodynamic studies found that Cr(VI) adsorption follows pseudo-second-order kinetics and Modified Langmuir isotherm. The maximum adsorption capacity of C + G beads for Cr(VI) was found to be 28.65 mg g−1. These results obtained indicate that the cyclic voltammetric technique using gold electrode can be effectively applied for Cr(VI) analysis from wastewaters. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs), a promising third-generation photovoltaic technology, have drawn considerable attention. Yet, their conventional metal back electrode layer, often composed of gold or silver, presents environmental and stability challenges. In this study, we conducted a lab-scale optimization of perovskite solar cells utilizing gold and carbon electrodes. A cradle-to-gate life cycle assessment (LCA) was performed using primary data from Thailand's National Nanotechnology Center (NANOTEC) and the Sima Pro 9.3.0.2 software with the ReCiPe 2016 impact methodology, consisting of 18 midpoint and three endpoint impact categories. Our analysis reveals that transitioning from gold electrodes (PSC-Au) to carbon electrodes (PSC-CB) fabricated through a low-temperature process not only maintains equivalent power conversion efficiency but also enhances stability, resulting in significantly reduced environmental impacts across all categories, with an impressive 86% reduction in global warming potential (GWP) per 1 kWh of energy produced. Furthermore, sensitivity analysis underscores PSC-CB's superiority in GWP compared to other established renewable energy technologies, provided its operational lifespan extends to 15 years. These findings highlight PSC-CB's substantial potential for commercialization as a sustainable renewable energy technology. • Cradle-to-Gate LCA for the same architecture and performance of PSCs between the Gold electrode and Carbon electrode • Thermal evaporation and gold material loss in the process were indicated as hotspot and commercialization barriers • Carbon electrodes cut environmental impact by over 79% or an average of 93.9% across all categories versus gold electrodes • PSCs with carbon electrodes surpass other renewables in global warming impact when a device lifespan exceeding 15 years [ABSTRACT FROM AUTHOR]

A CA19-9 electrochemical immunosensor was constructed using a hybrid self-assembled membrane modified with a gold electrode and applied to detect real samples. Hybrid self-assembled membranes were selected for electrode modification and used to detect antigens. First, the pretreated working electrodes were placed in a 3-mercaptopropionic acid (MPA)/β-mercaptoethanol (ME) mixture for 24 h for self-assembly. The electrodes were then placed in an EDC/NHS mixture for 1 h. Layer modification was performed by stepwise dropwise addition of CA19-9 antibody, BSA, and antigen. Differential pulse voltammetry was used to characterize this immunosensor preparation process. The assembled electrochemical immunosensor enables linear detection in the concentration range of 0.05–500 U/mL of CA19-9, and the detection limit was calculated as 0.01 U/mL. The results of the specificity measurement test showed that the signal change of the interfering substance was much lower than the response value of the detected antigen, indicating that the sensor has good specificity and strong anti-interference ability. The repeatability test results showed that the relative standard deviations were less than 5%, showing good accuracy and precision. The CA19-9 electrochemical immunosensor was used for the actual sample detection, and the experimental results of the standard serum addition method showed that the RSD values of the test concentrations were all less than 10%. The recoveries were 102.4–115.0%, indicating that the assay has high precision, good accuracy, and high potential application value.

In this study, a molecularly imprinted electrochemical sensor (MIP/DA) was investigated for selective and sensitive determination of dopamine (DA) by electrochemical polymerization of p‐aminothiophenol in the presence of DA on gold electrode. According to electrochemical behaviour of the sensor, gained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), MIP/DA sensor showed distinctive electron transfer characteristics in comparison to the non‐imprinted (NIP/DA) sensor. Besides the MIP/DA sensor showed high selectivity for dopamine through its analyte specific cavities. The sensor had a broad working range of 5.0×10−8–2.0×10−7 M with a limit of detection (LOD) of 1.8×10−8 M and the developed sensor was successfully applied for determination of dopamine in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

A gold nanoparticles transparent electrode was realized by chemical reduction. This work aims to compare the transparent gold nanoparticles electrode with a more commonly utilized gold-film-coated electrode in order to investigate its potential use as counter-electrode (CE) in dye-sensitized solar cells (DSSCs). A series of DSSC devices, utilizing I−/I3− and Co(III)/(II) polypyridine redox mediators [Co(dtb)3]3+/2+; dtb = 4,4′ditert-butyl-2,2′-bipyridine)], were evaluated. The investigation focused firstly on the structural characterization of the deposited gold layers and then on the electrochemical study. The novelty of the work is the realization of a gold nanoparticles CE that reached 80% of average visible transmittance. We finally examined the performance of the transparent gold nanoparticles CE in DSSC devices. A maximum power conversion efficiency (PCE) of 4.56% was obtained with a commercial I−/I3−-based electrolyte, while a maximum 3.1% of PCE was obtained with the homemade Co-based electrolyte.

This work focused on the development and optimization of an impedimetric label-free immunosensor for detecting deoxynivalenol (DON). A monoclonal antibody for DON detection was immobilized on a modified gold electrode with a cysteamine layer and polyamidoamine (PAMAM) dendrimers. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to monitor the layer-by-layer development of the immunosensor design, while electrochemical impedance spectroscopy and differential pulse voltammetry were employed to investigate the antigen/antibody interaction. The PAMAM dendrimers, allowing to immobilize a large number of monoclonal antibodies, permitted reaching, through the DPV technique, a high sensitivity and a low limit of detection equal to 1 ppb. The evaluation of the possible reuse of the immunosensors highlighted a decrease in the analytical performances of the regenerated immunosensors. After evaluating the matrix effect, the developed immunosensor was used to quantify DON in pasta samples spiked with a known mycotoxin concentration. Taking into consideration the DON extraction procedure used for the pasta samples and the matrix effect related to the sample, the proposed immunosensor showed a limit of detection of 50 ppb, which is lower than the maximum residual limit imposed by European Regulation for DON in dry pasta (750 ppb).

A voltammetric technique for electrochemical sensing and quantification of granulocytosis risk inducing metabolite of aminopyrine, 4-Aminoantipyrine (4-AAP) at gold electrode has been developed. The gold electrode shows excellent selectivity and sensitivity towards the oxidation of 4-AAP in phosphate buffer solution (PBS) of pH=3.0. It is observed from the electrochemical studies of scan rate that overall electrode process is diffusion controlled and pH effect suggests involvement of protons in electrochemical oxidation of 4-AAP. A linear current response towards the electrochemical oxidation of 4-AAP in the concentration range of 1.0 × 10-6 - 2.5 × 10-5 M is observed with limit of detection of 3.8 × 10-8 M (S/N = 3). The interference studies have shown that the gold electrode exhibited excellent selectivity in presence of large excess of interferents. The method is employed to recovery study of 4-AAP in spiked urine and serum samples. [ABSTRACT FROM AUTHOR]

The development of highly sensitive and highly selective sensors for non-enzymatic glucose and hydrogen peroxide (H2O2) detection using gold–copper alloy nanoparticles (AuCu alloy NPs) is reported. The AuCu NPs are nanostructures with branches and can be used as an electrochemical catalyst. Series of AuCu alloy NPs with various metal ratios are synthesized through a coreduction reaction. The morphology of AuCu alloy NPs is altered from highly branched structures (nanourchin, nanobramble, nanostar, nanocrystal) to a spherical shape by increasing Au content in the synthesis reaction. Cu-rich AuCu nanobramble and Au-rich AuCu nanostar exhibit selective electrocatalysis behaviors toward electro-oxidation of glucose and electroreduction of H2O2, respectively. The AuCu nanobramble–based sensor holds great potential in glucose detection with a linear working range of 0.25 to 10 mM. The sensor possesses a sensitivity of 339.35 μA mM−1 cm−2, a limit of detection (LOD) of 16.62 μM, which is an acceptable selectivity and good stability. In addition, the AuCu nanostar–based sensor shows excellent electrochemical responses toward H2O2 reduction with good selectivity, reproducibility, and a short response time of about 2–3 s. The linear range for H2O2 determination is 0.05 to 10 mM, with LOD and sensitivity of 10.93 μM and 133.74 μA mM−1 cm−2, respectively. The good sensing performance is a result of the synergistic surface structure and atomic composition effects, which leads AuCu alloys to be a promising nanocatalyst for sensing both glucose and H2O2. [ABSTRACT FROM AUTHOR]