Nickel contamination analysis at cost-effective silver printed paper-based electrodes based on carbon black dimethylglyoxime ink as electrode modifier

Electrochemical detection of metal cations at paper-based sensors has been suggested as an attractive alternative to current spectroscopic and chromatographic detection techniques due to the ease of fabrication, disposable nature, and low cost. Herein, a novel carbon black (CB), dimethylglyoxime (DMG) ink is designed as an electrode modifier in conjunction with 3-electrode inkjet-printed paper substrates for use in the adsorptive stripping voltammetric electroanalysis of nickel cations in water samples. The developed method provides a novel, low-cost, rapid, and portable adsorptive stripping detection approach towards metal analysis in the absence of the commonly used toxic metallic films. The study demonstrated a novel approach to nickel detection at paper-based sensors and builds on previous work in the field of paper-based metal analysis by limiting the use of toxic metal films. The device sensitivity is improved by increasing the active surface area, electron transfer kinetics, and catalytic effects associated with non-conductive dimethylglyoxime films through CB nanoparticles for the first time and confirmed by electroanalysis. The first use of the CB-DMG ink allows for the selective preconcentration of analyte at the electrode surface without the use of toxic Mercury or Bismuth metallic films. Compared to similarly reported paper-based sensors, improved limits of detection (48 µg L-1), selectivity, and intermetallic interferences were achieved. The method was applied to the detection of nickel in water samples well below World Health Organization (WHO) standards.

Electrodeposited palladium as efficient electrocatalyst for hydrazine and methanol electro-oxidation and detection

Electrodeposited palladium was used as an electrocatalyst for electrochemical oxidation of hydrazine and methanol and the development of a sensitive platform for their detection. The electrochemical behavior of the electrode was evaluated by cyclic voltammetry (CV) while electroanalytical properties were determined by means of differential pulse voltammetry (DPV). The electrodeposited Pd catalyst exhibited good electrocatalytic activity towards the oxidation of hydrazine in neutral solution and methanol oxidation in alkaline solution. Under optimized DPV conditions, the electrodeposited Pd electrode shows good sensing capability in hydrazine and methanol detection.

Tailoring surface properties of functionalized graphene papers aiming to enzyme immobilization

The use of enzymes as catalysts requires recovery and reuse to make the process viable. Enzymatic immobilization changes enzyme stability, activity, and specificity. It is very important to explore new substrates for immobilization with appropriate composition and structure to improve the efficiency of the immobilized enzymes. This work explores the use of two different graphene oxide papers, one produced by oxidation route (GO) and the other by electrochemical synthesis (EG), aiming for β-galactosidase immobilization. The chemical and structural properties of these two papers were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Atomic force microscopy images showed that EG paper ensured more efficient immobilization of the enzymes on the surface of the paper. Cyclic voltammetry was used to monitor the reaction of conversion of lactose to glucose in the free enzyme solution and graphene paper immobilized enzyme solutions. The cyclic voltammetry analysis showed that immobilized enzymes on GO paper showed an improvement in the activity of β-galactose when compared to free enzyme solution, as well as enzyme immobilized on a glassy carbon electrode.

Decolorization of industrial wastewater using electrochemical peroxidation process

In this study, decolorization of wastewater samples taken from the paper industry is investigated using electrochemical peroxidation process. The electrochemical peroxidation process is a part of electrochemical advanced oxidation processes, which is based on the Fenton’s chemical reaction, provided by addition of external H2O2 into reaction cell. In this study, iron is used as anode and graphite as cathode put at the fixed distance of 30 mm in a glass reaction cell. The cell was filled with the solution containing wastewater and sodium chloride as the supporting electrolyte. Factors of the process such as pH, current intensity, hydrogen peroxide concentration, and time of treatment were studied. The results illustrate that all these parameters affect efficiencies of dye removal and chemical oxygen demand (COD) reducing. The maximal removal of wastewater contaminants was achieved under acid (pH 3) condition, with the applied current of 1 A, and hydrogen peroxide concentration of 0.033 M. At these conditions, decolorization process efficiency reached 100 and 83 % of COD removal after 40 minutes of wastewater sample treatment. In addition, the electrical energy consumption for wastewater treatment by electrochemical peroxidation is calculated, showing increase as the current intensity of treatment process was increased. The obtained results suggest that electrochemical peroxidation process can be used for removing dye compounds and chemical oxygen demand (COD) from industrial wastewaters with high removal efficiency.

Modelling the effect of anode particle radius and anode reaction rate constant on capacity fading of Li-ion batteries

This paper investigates the effect of anode particle radius and anode reaction rate constant on the capacity fading of lithium-ion batteries. It is observed through simulation results that capacity fade will be lower when the anode particle size is smaller. Simulation results also show that the reaction rate constant for the anode reaction has a good impact on the capacity loss of a lithium-ion battery. The potential drop across the SEI layer (solid electrolyte interphase) is studied as a function of the anode particle radius and anode reaction rate constant. Modelling results are compared with experimental data and found to compare well.

Electrochemical determination of tramadol using modified screen printed electrode

The detection of tramadol using a screen printed electrode modified with La3+/ZnO nano-flowers and multi-walled carbon nanotubes (La3+/ZnO NFs-MWCNTs/SPE) is reported in this work. In order to examine tramadol electrochemical oxidation, the modified electrode was implemented with the utilization of differential pulse voltammetry, chronoamperometry and cyclic voltammetry as diagnostic techniques. The proposed electrode displays favorable electrocatalytic behavior concerning tramadol oxidation with an approximately 330 mV potential shift to a lesser positive potential. In the 0.5 to 800.0 μM range for tramadol, differential pulse voltammetry displays linear dynamic activity. Tramadol detection limit of 0.08 μM was derived within optimized testing conditions for this simple construction sensor. Lastly, this fabricated sensor was utilized with desirable results to determine tramadol in tramadol samples and urine samples.

Development of highly stable conductive multiwalled carbon nanotube ink using covalent and non-covalent functionalization for electrochemical sensors

The purpose of this work was the fabrication of a conductive carbon nanotube (CNT) ink. The proposed CNT ink remained remarkably stable over several months. The method includes combining the covalent and non-covalent functionalization, resulting in ink that exhibits excellent storage stability. The covalent functionalization was performed in the acid medium using H2SO4 and HNO3, while the non-covalent functionalization used sodium dodecyl sulfate (SDS) and ultrasonication. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), electro­chemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). FTIR and SEM confirmed that at the non-covalent functionalization, SDS was successfully adsorbed on the f-CNT surface, while at the covalent functionalization, the functional groups (-COOH, C=O and -OH) were inserted into the CNT surface. Voltammetry and EIS indicated that SDS in the presence of functional groups facilitates electron transfer by improved electrical conductivity. The final product was a well-dispersed CNT ink with an average ohmic resistance of 18.62 kΩ. This indicates that CNT ink can be used in the fabrication of electrochemical sensors.

Electrochemical studies of lateral flow assay test results for procalcitonin detection

In this study, the lateral flow assay (LFA) has been developed for the detection of bacterial infection (BI) by specific biomarker procalcitonin (PCT), without a need for complicated instrumentations and technical expertise. For the development of the assay, gold nanoparticles (AuNP) and their conjugates with antibodies specific to the model antigen PCT are assessed. Polyclonal antibody (pAb) labelled with gold nanoparticles (AuNP) to obtain the AuNP-pAb complex and the specific monoclonal antibody (mAb) have been dropped at the test zone. This complex is placed over the conjugate line of the LFA strip. In the absence of PCT or the presence of other biomarkers, the test line remained colourless, which revealed the specificity of assay towards PCT among a pool of various analytes. Herein, observations have been made through two different platforms for quantitative and qualitative analysis for the detection of PCT biomarker. The qualitative analysis has been performed on the basis of appearance red color in the test band, while for quantitative analysis, a novel approach has been adopted. Herein, the nitrocellulose membrane (paper strip) is cut out from the LFA strip and used for electrochemical studies under similar solution conditions. Different paper strips presented different cyclic voltammograms (CV) that could be correlated to varying PCT concentrations captured at the test line of the paper strip. The qualitative detection limit for PCT using this LFA was determined to be 2 ng/ml and the quantitative detection limit was 1 ng/ml. The electrochemical response studies of the paper strip by CV technique revealed the sensitivity value of 0.695 mA ng/ml.

Electrochemical nanobiosensors perspectives for COVID 19 pandemic

Early, rapid and ultrasensitive diagnosis of COVID-19 to facilitate high-throughput analysis without a high degree of technical expertise or sophisticated equipment is necessary to expand COVID-19 testing capability. Leveraging interdisciplinary proficiency in analytical chemistry, biomedical instrumentation, molecular biology, microfluidics, and nanotechnology, considerable advances have been made to develop a novel diagnostic tool that assures superior key performances for COVID-19 diagnosis. This review summarizes the nano-enabled systems such as electrochemical nanobiosensor for SARS-CoV-2 virus detection and emphasizes promising diagnostic techniques to extensively facilitate the diagnostic practices during the COVID-19 pandemic. Currently, three main diagnostic methods have been widely used in the COVID-19 pandemic: nucleic acid (NA)-based testing, computed tomography (CT), and serological testing. NA-based detection of SARS-CoV-2 such as Reverse transcription polymerase chain reaction has become the gold standard for COVID-19 diagnosis. This review congregates significant contributions in the electrochemical nanobiosensor research area, which is helpful for further nanobiosensor development. Although many efforts were taken to detect the SARS-CoV-2, the COVID 19 diagnosis still relies on expensive prolonged analysis. A rapid and reliable alternative is the utilization of a low-cost nanobiosensor for SARS-CoV-2 detection that can rapidly diagnose the disease even in asymptomatic conditions with high reliability and sensitivity.

Influence of supporting electrolyte on electrochemical formation of copper nanoparticles and their electrocatalytic properties

Comparative analysis of copper nanoparticles (CuNPs) obtained by electrodeposition on highly oriented pyrolytic graphite (HOPG) substrates from different supporting electrolytes containing sulphate anions, was performed. Voltammetric results indicated that Cu electrodeposition follows a diffusion-controlled nucleation and crystal growth model for three solutions studied (Na2SO4, H2SO4 and Na2SO4+H2SO4). Na2SO4 solution was found to be most effective because the copper reduction occurs at most positive potential value, reaching the highest current density. Analysis of potentiostatic current transients revealed that the process can be described predominantly by a model involving 3D-progressive nucleation mechanism, which was corroborated by scanning electron microscopy (SEM) analysis. SEM images showed high density of hemispherical shaped Cu particles of different sizes (mostly between 80-150 nm), randomly distributed on the HOPG surface for Na2SO4 electrolyte solution. In the presence of H2SO4, the size dispersion decreased, resulting in particles with greater diameters (up to 339 nm). The use of electrolyte solution with Na2SO4+H2SO4 revealed lower particle density with a considerable crystal size dispersion, where very small crystallites are prevailing. Cyclic voltammetry was used to evaluate qualitatively the catalytic activity of CuNPs deposited from three electrolyte solutions towards the nitrate reduction reaction. An enhanced catalytic effect was obtained when copper particles were prepared from either Na2SO4 or H2SO4 supporting electrolytes.