Unmodified Screen Printed Carbon Electrode Research Articles

A Disposable Electrochemical Sensing Platform for Acetaminophen Based on Graphene/ZrO2 Nanocomposite Produced via a Facile, Green Synthesis Method

In this paper, a disposable electrochemical sensor was fabricated using graphene/zirconium dioxide (ZrO2)-modified screen printed carbon electrode (SPCE). The implemented synthesis route is simple, cost feasible, and abolish the usage of harsh chemical. A green approach using single step exfoliation of graphite in mild sonochemical ethanol–water treatment and hydrothermal synthesis method were employed to prepare the graphene/ZrO2 nanocomposites. Characterization methods, such as X-ray diffraction, scanning electron microscope (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy dispersive x-ray spectroscopy (EDX), were used to study the crystallinity, surface characteristics, morphology and elemental composition of the synthesized nanocomposites. All the results evidently suggested that pristine graphene was successfully produced without attachment of any undesirable functional groups and ZrO2 nanoparticles of approximately 10.4 nm were homogeneously distributed on the graphene sheet. The electrochemical performance of the graphene/ZrO2/SPCE was assessed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Both tests suggested improved electron transfer kinetic of graphene/ZrO2/SPCE as compared with bare SPCE. Effect of ZrO2 precursor loading was investigated, in which nanocomposites containing different ratios of graphene and ZrO2 precursors were prepared. CV and EIS results indicated that ratio 1:8 (graphene: ZrO2 precursor) was the optimum composition, exhibiting the highest current response and lowest charge transfer resistance. The potential application of graphene/ZrO2/SPCE for electroanalytical purposes was demonstrated with acetaminophen detection. The graphene/ZrO2/SPCE sensor was calibrated with differential pulse voltammetry and demonstrated better electrocatalytic activity toward acetaminophen with lower oxidation potential and higher peak current than the unmodified SPCE. The sensor exhibited a linear range of 10– $100~\mu \text{M}$ , detection limit of 75.5 nM, reproducibility of <5 % relative standard deviation (RSD), repeatability of < 3% RSD, and good selectivity to acetaminophen in the presence of dopamine and ascorbid acid. The graphene/ZrO2/SPCE sensor was applied to determine acetaminophen in pharmaceutical tablets and yielded satisfactory results. The simple, low cost, and green method reported here can be further exploited to provide a biocompatible platform for electrochemical sensing application.

A novel electrochemical biosensor for ultrasensitive detection of serum total bile acids based on enzymatic reaction combined with the double oxidation circular amplification strategy

Serum total bile acids (TBA) level is used as a sensitive and reliable index for hepatobiliary diseases in clinics. Herein, a novel electrochemical biosensor was fabricated using enzymatic reaction coupling with the double oxidation circular amplification strategy for the detection of human serum TBA. With the catalysis of 3α-hydroxysteroid dehydrogenase (3α-HSD), 3α-bile acids reacted specifically with nicotinamide adenine dinucleotide (NAD+). And then, the reduced nicotinamide adenine dinucleotide (NADH) was produced. After that, the NADH reacted with the electron mediator of tris(2,2'-bipyridine) ruthenium(Ⅲ) (Ru(bpy)33+), which was then transformed to Ru(bpy)32+. Ultimately, Ru(bpy)32+ was further oxidized to Ru(bpy)33+ under a certain voltage, which was detected by the chronoamperometry assay. The detection was performed using a disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation. The proposed biosensor showed high sensitivity and accuracy with the linear range from 5.0 to 150.0 pmol/L in 106-fold dilution serum. The established method had a good correlation with the enzymatic cycling method (r = 0.9372, P < 0.001, n = 72) commonly used in clinic. The electrochemical biosensor is simple, ultrasensitive and without sample pretreatment, showing great potential for point-of-care testing (POCT) of serum TBA in clinical samples. In addition, the biosensor is cost-effective with a small volume of samples, especially suitable for those who have difficulties in blood collection, such as infants, children and some small animals.

Electrocatalytic Oxidation and Flow Injection Analysis of Isoniazid Drug Using an Unmodified Screen Printed Carbon Electrode in Neutral pH

AbstractIn this work we report electrocatalytic oxidation and flow injection analysis of tuberculostatic drug isoniazid (INZ) based on a disposable and unmodified screen printed carbon electrode (SPCE). Instead of using chemically modified electrode to increase the sensitivity at low overpotential, the same purpose can be achieved simply by preanodization of a bare SPCE in a suitable electrolyte medium. Surface characterization of the as‐preanodized electrode by X‐ray photoelectron spectroscopy and Raman spectroscopy indicate that both oxygen functionalities and edge/defect sites effectively assist the INZ oxidation. Flow injection analysis extends its applicability with a wide linear range up to 1 mM and an enhanced sensitivity of 100 nA μM−1 with a low detection limit of 2.7 nM (S/N=3). These good analytical features accomplished with disposable and economical devices could make possible the implementation of this methodology for INZ on‐line monitoring in pharmaceuticals.

Direct electrochemical measurement of metanephrines in spot urine samples for the diagnosis of phaeochromocytomas

Metanephrines (MNs) were suggested as a potential first-line biochemical index for the diagnosis of phaeochromocytomas (PHEO). In this study, we developed a simple electrochemical method for the quantitative measurement of MNs in spot urine samples. As MNs contain a hydroxyphenyl group, they could be oxidized at a certain potential to quinines, which could be further detected by the differential pulse voltammetry (DPV) method using unmodified screen-printed carbon electrode (SPCE). Meanwhile, the solid phase extraction (SPE) technique was used to eliminate the matrix effect in the samples. Consequently, free MNs from the extracted urine sample were screened in a linear range from 0.25 mg/L to 12.5 mg/L. The lowest limit of quantification (LLOQ) for MNs was 0.25 mg/L and the limit of detection (LOD) was 0.05 mg/L. Both the precisions and recoveries were sufficient for clinical applications. The urine samples from 22 patients with PHEO and 63 controls were analyzed by the proposed method. The area under the ROC curve was 0.981 (95% CI, 0.958–1.000) with the sensitivity of 95.5% and the specificity of 92.4% at the cut-off value of 0.404 mg/L in these urine samples. Overall, the proposed method provides a cost-effective, rapid and simple tool for clinical diagnosis of PHEO.

Disposable Carbon Dots Modified Screen Printed Carbon Electrode Electrochemical Sensor Strip for Selective Detection of Ferric Ions

A disposable electrochemical sensor strip based on carbon nanodots (C-Dots) modified screen printed carbon electrode (SPCE) was fabricated for selective detection of ferric ions (Fe3+) in aqueous solution. C-Dots of mean diameters within the range of 1–7 nm were synthesized electrochemically from spent battery carbon rods. The analytical performance of this electrochemical sensor strip was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The deposition of C-Dots had enhanced the electron-transfer kinetics and current intensity of the SPCE remarkably by 734% as compared to that of unmodified SPCE. Under optimized conditions, the electrochemical sensor strip exhibited a linear detection range of 0.5 to 25.0 ppm Fe3+ with a limit of detection (LOD) of 0.44±0.04 ppm (at S/N ratio = 3). Validation of results by the electrochemical sensor strip was done by comparing analysis results obtained using an Atomic Absorption Spectrometer (AAS).

Carbon nanoparticle modified screen printed carbon electrode as a disposable electrochemical immunosensor strip for the detection of Japanese encephalitis virus

The authors describe a disposable electrochemical immunosensor strip for the detection of the Japanese encephalitis virus (JEV). The assay is based on the use of a screen printed carbon electrode (SPCE) modified with carbon nanoparticles (CNPs) that were prepared from starch nanoparticles and deposited on the SPCE working electrode whose surface was functionalized with 3-aminopropyl triethoxysilane. Next, antibody of JEV was immobilized on the surfaces of the CNPs. The analytical performance of immunosensor strip was characterized using cyclic voltammetry (with hexacyanoferrate as the redox probe) and electrochemical impedance spectroscopy. The deposition of CNPs enhances the electron transfer kinetics and current intensity of the SPCE by 63% compared to an unmodified SPCE. Under optimized conditions, the calibration plot is linear within the 5–20 ng·mL−1 JEV concentration range, the limit of detection being 2 ng·mL−1 (at an S/N ratio of 3), and the assay time is 20 min. This immunosensor strip was successfully applied to the detection of JEV in human serum samples. It represents a cost-effective alternative to conventional diagnostic tests for JEV.

Development of electrochemical sensor for the determination of palladium ions (Pd2+) using flexible screen printed un-modified carbon electrode

To date, the development of different modified electrodes have received much attention in electrochemistry. The modified electrodes have some drawbacks such as high cost, difficult to handle and not eco friendly. Hence, we report an electrochemical sensor for the determination of palladium ions (Pd2+) using an un-modified screen printed carbon electrode has been developed for the first time, which are characterized and studied via scanning electron microscope and cyclic voltammetry. Prior to determination of Pd2+ ions, the operational conditions of un-modified SPCE was optimized using cyclic voltammetry and showed excellent electro-analytical behavior towards the determination of Pd2+ ions. Electrochemical determination of Pd2+ ions reveal that the un-modified electrode showed lower detection limit of 1.32μM with a linear ranging from 3 to 133.35μM towards the Pd2+ ions concentration via differential pulse voltammetry. The developed sensor also applied to the successfully determination of trace level Pd2+ ions in spiked water samples. In addition, the advantage of this type of electrode is simple, disposable and cost effective in electrochemical sensors.

Development of a Nafion/MWCNT-SPCE-Based Portable Sensor for the Voltammetric Analysis of the Anti-Tuberculosis Drug Ethambutol.

Herein we describe the development, characterization and application of an electrochemical sensor based on the use of Nafion/MWCNT-modified screen-printed carbon electrodes (SPCEs) for the voltammetric detection of the anti-tuberculosis (anti-TB) drug ethambutol (ETB). The electrochemical behaviour of the drug at the surface of the developed Nafion/MWCNT-SPCEs was studied through cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed to characterize the modified surface of the electrodes. Results showed that, compared to both unmodified and MWCNTs-modified SPCEs, negatively charged Nafion/MWCNT-SPCEs remarkably enhanced the electrochemical sensitivity and selectivity for ETB due to the synergistic effect of the electrostatic interaction between cationic ETB molecules and negatively charged Nafion polymer and the inherent electrocatalytic properties of both MWCNTs and Nafion. Nafion/MWCNT-SPCEs provided excellent biocompatibility, good electrical conductivity, low electrochemical interferences and a high signal-to-noise ratio, providing excellent performance towards ETB quantification in microvolumes of human urine and human blood serum samples. The outcomes of this paper confirm that the Nafion/MWCNT-SPCE-based device could be a potential candidate for the development of a low-cost, yet reliable and efficient electrochemical portable sensor for the low-level detection of this antimycobacterial drug in biological samples.

Quantification of ethanol in plasma by electrochemical detection with an unmodified screen printed carbon electrode

Simple, rapid and accurate detection of ethanol concentration in blood is very crucial in the diagnosis and management of potential acute ethanol intoxication patients. A novel electrochemical detection method was developed for the quantification of ethanol in human plasma with disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation procedure. Ethanol was detected indirectly by the reaction product of ethanol dehydrogenase (ADH) and cofactor nicotinamide adenine dinucleotide (NAD+). Method validation indicated good quantitation precisions with intra-day and inter-day relative standard deviations of ≤9.4% and 8.0%, respectively. Ethanol concentration in plasma is linear ranging from 0.10 to 3.20 mg/mL, and the detection limit is 40.0 μg/mL (S/N > 3). The method shows satisfactory correlation with the reference method of headspace gas chromatography in twenty human plasma samples (correlation coefficient 0.9311). The proposed method could be applied to diagnose acute ethanol toxicity or ethanol-related death.

Effective monitoring of the electro-Fenton degradation of phenolic derivatives by differential pulse voltammetry on multi-walled-carbon nanotubes modified screen-printed carbon electrodes

This work illustrates a fast, sensitive and selective electroanalytical methodology for simultaneous determination of phenolic derivatives. Optimization of differential pulse voltammetry (DPV) conditions and electrochemical study by cyclic voltammetry (CV) of phenolics are included. Differential pulse voltammetry at screen-printed carbon electrodes (SPCE) was selected for the sensitive detection of m-Cresol and Tert-butylhydroquinone. The introduction of Multi-walled Carbon-Nanotubes with acid groups, MWCNT-COOH, as modifier on working SPCE enhances the performance of electrode surface with a highly catalytic activity on it, allowing a 5-fold higher sensitive analysis than unmodified SPCE, with a limit of detection as low as about 1μM. This simple and low-cost methodology has been applied, for first time, to monitoring the electro-Fenton degradation of m-Cresol, giving selective information of the reactant loss and products formation. Aromatic intermediates (monohydroxy, polyhydroxy and quinone phenolic derivatives) have been identified and followed during the electrolysis process. The electro-Fenton with iron on activate carbon is 4-fold faster than with other catalyst. The results are validated by chromatographic (HPLC) technique. The electroanalytical methodology described, in conjunction with the use of small SPCE as sensor transducer, can be implemented for continuous monitoring of end-point of the electro-Fenton reaction at industrial level in wastewater remediation plants, indicating the two main stages of electro-Fenton during the electrolysis.

Graphene/polyvinylpyrrolidone/polyaniline nanocomposite-modified electrode for simultaneous determination of parabens by high performance liquid chromatography

A nanocomposite of graphene (G), polyvinylpyrrolidone (PVP) and polyaniline (PANI) modified onto screen-printed carbon electrode (SPCE) using an electrospraying technique was developed for simultaneous determination of five parabens in beverages and cosmetic products by high performance liquid chromatography. PVP and PANI were used as the dispersing agents of graphene, and also for the enhancement of electrochemical conductivity of the electrode. The electrochemical behavior of each paraben was investigated using the G/PVP/PANI nanocomposite-modified SPCE, compared to the unmodified SPCE. Using HPLC along with amperometric detection at a controlled potential of +1.2V vs Ag/AgCl, the chromatogram of five parabens obtained from the modified SPCE exhibits well defined peaks and higher current response than those of its unmodified counterpart. Under the optimal conditions, the calibration curves of five parabens similarly provide a linear range between 0.1 and 30µgmL−1 with the detection limits of 0.01µgmL−1for methyl paraben (MP), ethyl paraben (EP) and propyl paraben (PP), 0.02 and 0.03µgmL−1 for isobutyl paraben (IBP) and butyl paraben (BP), respectively. Furthermore, this proposed method was applied for the simultaneous determination of five parabens in real samples including a soft drink and a cosmetic product with satisfactory results, yielding the recovery in the range of 90.4–105.0%.

An electrochemical sensor based on graphene/polyaniline/polystyrene nanoporous fibers modified electrode for simultaneous determination of lead and cadmium

The development of graphene/polyaniline/polystyrene (G/PANI/PS) nanoporous fiber modified screen-printed carbon electrode (SPCE) using electrospinning fabrication for simultaneous determination of lead (Pb2+) and cadmium (Cd2+) was achieved. Initially, the important factors controlling the electrospun fiber morphology and electrochemical sensitivity (e.g. type of solvent, amount of G loading) were investigated and optimized. Then, the electrospun G/PANI/PS nanoporous fibers were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammetric (CV) measurements using a standard ferri/ferrocyanide [Fe(CN)6]3−/4− redox couple were performed for electrochemical characterization of the modified electrode. Due to the increase of specific surface area of the electrospun G/PANI/PS nanoporous fibers, the electrochemical sensitivity of modified SPCE was enhanced by a factor of three compared to an unmodified SPCE. In terms of application, square-wave anodic stripping voltammetry (SWASV) was employed for the simultaneous determination of Pb2+ and Cd2+ in the presence of bismuth (Bi3+) on G/PANI/PS nanoporous fiber-modified SPCE. Under optimal conditions, a linear relationship between anodic current and metal ion concentration was found in a range of 10–500μgL−1 with the detection limit (S/N=3) of 3.30μgL−1 and 4.43μgL−1 for Pb2+ and Cd2+, respectively. In addition, the effects of common cation and anion interferences commonly found in environmental water were studied, and the satisfied results were obtained. Interestingly, by simple washing step, this described electrode can be reused for more than ten replicates with high reproducibility. Finally, this new electrode system was successfully applied for the simultaneous determination of Pb2+ and Cd2+ in real river water samples, and the results correlated well with conventional inductively coupled plasma optical emission spectroscopy (ICP-OES).

Inkjet-printed graphene-PEDOT:PSS modified screen printed carbon electrode for biochemical sensing

In this work, a novel method for electrode modification based on inkjet-printing of electrochemically synthesized graphene-PEDOT:PSS (GP-PEDOT:PSS) nanocomposite is reported for the first time. GP-PEDOT:PSS dispersed solution is prepared for use as an ink by one-step electrolytic exfoliation from a graphite electrode. GP-PEDOT:PSS layers are then printed on screen printed carbon electrodes (SPCEs) by a commercial inkjet material printer (Dimatrix Inc.) and their electrochemical behaviors towards three common electroactive analytes, including hydrogen peroxide (H2O2), nicotinamide adenine dinucleotide (NAD+/NADH) and ferri/ferro cyanide (Fe(CN)63−/4−) redox couples, are characterized. It is found that the oxidation signals for H2O2, NADH and K2Fe(CN)6 of PEDOT:PSS modified and GP-PEDOT:PSS modified SPCEs are ∼2–4 and ∼3–13 times higher than those of unmodified SPCE, respectively. In addition, excellent analytical features with relatively wide dynamic ranges, high sensitivities and low detection limits have been achieved. Therefore, the inkjet-printed GP-PEDOT:PSS electrode is a promising candidate for advanced electrochemical sensing applications.

Inkjet-printed graphene-poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) modified on screen printed carbon electrode for electrochemical sensing of salbutamol

In this work, a simple and sensitive inkjet-printed graphene-poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (GP-PEDOT:PSS) on screen printed carbon electrode (SPCE) is developed for detection of salbutamol (SAL), a prohibited drug in sport. GP-PEDOT:PSS dispersed solution is prepared for use as an ink by one-step electrolytic exfoliation from a graphite electrode. GP-PEDOT:PSS layers are then printed on SPCEs by dimatrix inkjet material printer and their electrochemical behaviors are characterized. It is found that SAL oxidation peak responses of PEDOT:PSS modified and GP-PEDOT:PSS modified SPCE electrodes are approximately 30 and 150 times higher than that of unmodified SPCE, respectively. In addition, excellent analytical features with a wide dynamic range of 500 μM, a low detection limit (3S/N) of 1.25 μM and low matrices’ interference in pharmaceutical samples have been achieved. Therefore, inkjet-printed GP-PEDOT:PSS SPCE is a promising candidate for advanced electrochemical sensing applications.

A novel poly(3,4-ethylenedioxythiophene)/iron phthalocyanine/multi-wall carbon nanotubes nanocomposite with high electrocatalytic activity for nitrite oxidation

In the present work, the oxidative electrochemistry of nitrite on the poly(3,4-ethylenedioxythiophene)/iron phthalocyanine/multi-wall carbon nanotubes-(PEDOT/FePc/MWCNT) modified screen-printed carbon electrodes (SPCE) has been investigated. The parameters, such as overpotential, current density and rate constant at PEDOT/FePc/MWCNT-modified SPCE, were compared with an un-modified, FePc-, and FePc/MWCNT-modified SPCE for electro-oxidation of nitrite. As compared with the un-modified SPCE, an increase in the anodic peak current density ( J pa) (∼100%) along with a decrease in the anodic peak potential ( E pa) of ∼150 mV for electro-oxidation of nitrite at the FePc-modified SPCE was observed. When an under-layer of MWCNT was introduced onto FePc-modified SPCE, denoted as FePc/MWCNT-modified SPCE, and the number of FePc/MWCNT bilayer was optimized, the heterogeneous electron transfer rate constant ( k) at FePc/MWCNT-modified SPCE was enhanced about 7.8 times as compared with that at FePc-modified SPCE. Moreover, as a layer of PEDOT film was electrodeposited onto the FePc/MWCNT-modified SPCE, denoted as PEDOT/FePc/MWCNT-modified SPCE, a significant increase in current response along with a remarkable decrease in E pa were noticed. This can be attributed to the pre-concentration effect induced by the electrostatic interaction between the negatively charged nitrite and oxidized PEDOT film. On the whole, the PEDOT/FePc/MWCNT-modified SPCE greatly reduces the overpotential of ∼330 mV along with 3.5 times enhanced the peak current density for the electro-oxidation of nitrite as compared with un-modified SPCE. The sensitivity and limit of detection (S/N = 3) for the PEDOT/FePc/MWCNT-modified SPCE were found to be as 638 mA cm −2 M −1 and 71 nM, respectively. Notably, PEDOT/FePc/MWCNT-modified SPCE has a lower sensing potential than compared to several other modified electrodes. The developed sensor was also applied for the determination of nitrite in tap water sample.

A simple and sensitive method for lactose detection based on direct electron transfer between immobilised cellobiose dehydrogenase and screen-printed carbon electrodes

A rapid and simple approach of lactose analysis is proposed based on 3rd generation amperometric biosensors employing cellobiose dehydrogenase (CDH) from Trametes villosa or Phanerochaete sordida immobilised on screen-printed carbon electrodes (SPCEs). After optimisation of the working conditions of the biosensors – pH of the carrier buffer, flow rate and applied potential – the sensors were able to detect lactose in a concentration range between 0.5–200 μM and 0.5–100 μM employing T. villosa and P. sordida CDH, respectively. The limit of detection is 250 nM (90 μg/L) for both. Biosensors based on SPCEs modified with multiwalled carbon nanotubes showed a higher sensitivity than unmodified SPCEs. Cross-linking with glutaraldehyde or poly(ethyleneglycol)diglycidyl ether improved not only the stability but also the analytical response. The developed sensor has been successfully applied for the determination of lactose in dairy (milk with different percentages of fat, lactose-free milk and yogurt) with a good reproducibility (RSD = 1.5–2.2%). No sample preparation except a simple dilution process is needed. The biosensor is easy to make and operate, is inexpensive and reveals a high sensitivity and reliability.