Modified Screen Printed Carbon Electrode Research Articles

A Unique Oligonucleotide Probe Hybrid on Graphene Decorated Gold Nanoparticles Modified Screen-Printed Carbon Electrode for Pork Meat Adulteration

A Unique Oligonucleotide Probe Hybrid on Graphene Decorated Gold Nanoparticles Modified Screen-Printed Carbon Electrode for Pork Meat Adulteration

The development of disposable electrochemical sensor based on MoSe2-rGO nanocomposite modified screen printed carbon electrode for amitriptyline determination in the presence of carbamazepine, application in biological and water samples

The present attempt developed a simple sensing system based on the modification of screen-printed carbon electrode (SPCE) with MoSe2/reduced graphene oxide (rGO) nanocomposite (MoSe2-rGO/SPCE) to voltammetrically co-detect amitriptyline and carbamazepine. Different techniques such as field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize MoSe2-rGO nanocomposite morphology and structure. Moreover, chronoamperometry, differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV) were utilized to explore the electrochemical oxidation of amitriptyline. Data revealed a great current sensitivity for the MoSe2-rGO/SPCE towards amitriptyline. The peak currents of amitriptyline oxidation on the MoSe2-rGO/SPCE had linear dynamic range (0.02–380.0 μM) and a narrow limit of detection (0.007 μM). The MoSe2-rGO/SPCE was successful in sensing carbamazepine and amitriptyline in real specimens, with appreciable recovery rates.

Non-enzymatic Electrochemical Sensing of 3-Hydroxybutyric Acid by Incorporating Manganese Oxide Modified Electrode and Nitroprusside Electrolyte

The development of 3-hydroxybutyric acid (3-HB) biosensors via electrochemical method is commonly based on the use of enzymes that usually display inherent instability. Here, a novel non-enzymatic 3-HB electrochemical sensor platform by incorporating manganese oxide nanoparticles (Mn2O3 NPs) modified screen printed carbon electrode (SPCE) and sodium nitroprusside (SNP) electrolyte was reported for the first time. The mechanism of this sensor based on the formation of electroactive SNP-HB species with assistance of Mn2O3 catalyst. By the enhanced electroactivity of the complex, 3-HB can be quantitatively measured based on the increased peak current and shifted peak potential in cyclic voltammograms of SNP reduction. SNP concentration and Mn2O3 loading were optimized for maximum current response. The sensitivity of as-prepared sensor system was examined under different pH values (6.4–7.4) in the range of 0–10 mM 3-HB. The highest sensitivity of 39.07 μA·mM−1·cm−2 and 5.84 mV·mM−1 with LOD of 0.5 mM was achieved at pH 7.4 of electrolyte solution. The proposed sensor provided favorable stability and selectivity against various interferents. In addition, the ability to quantitatively detect 3-HB in artificial urine was also demonstrated, suggesting that our sensor can be a promising candidate for practical applications.

Fabrication of Nitrogen-Doped Reduced Graphene Oxide Modified Screen Printed Carbon Electrode (N-rGO/SPCE) as Hydrogen Peroxide Sensor.

In recent years, the electrochemical sensing approach has attracted electrochemists because of its excellent detection process, simplicity, high sensitivity, cost-effectiveness, and high selectivity. In this study, we prepared nitrogen doped reduced graphene oxide (N-rGO) and characterized it using various advanced techniques such as XRD, SEM, EDX, Raman, and XPS. Furthermore, we modified the active surface of a screen printed carbon electrode (SPCE) via the drop-casting of N-rGO. This modified electrode (N-rGO/SPCE) exhibited an excellent detection limit (LOD) of 0.83 µM with a decent sensitivity of 4.34 µAµM−1cm−2 for the detection of hydrogen peroxide (H2O2). In addition, N-rGO/SPCE also showed excellent selectivity, repeatability, and stability for the sensing of H2O2. Real sample investigations were also carried out that showed decent recovery.

The correlation of haptenation of gold nanoparticles and cysteine modified screen printed carbon electrode by impedance technique with local lymph node assay data

Skin sensitization occurs when a skin sensitizer binds covalently to skin proteins through the haptenation process. The objective of this study was to correlate the electrochemical impedance spectroscopy (EIS) data of a screen printed carbon electrode (SPCE) modified with cysteine and gold nanoparticles (AuNPs) with local lymph node assay (LLNA) data as a potential skin sensitizer biosensor. The EIS was used to quantify variations in charge transfer resistance of skin sensitizers (ΔRCTskin sensitizer) due to different binding rates of skin sensitizers to cysteine. SPCE was modified through electrodeposition of AuNPs/thiourea/self–assembly of AuNPs/cysteine (assigned as ETSC) for the detection of skin sensitizers. Surface analysis of modified SPCEs using FESEM and EDX revealed a smooth surface with an uneven distribution of cysteine with AuNPs molecules. The ETSC modified SPCE showed a significant skin sensitizer biosensor since the ΔRCTskin sensitizer readings were increased proportionally to the strength of the skin sensitizers, with strong/extreme skin sensitizers displaying higher ΔRCTskin sensitizer readings compared to moderate and weak/non–skin sensitizers. The skin sensitization analysis from this work was compared to LLNA (animal study), human cell line activation (h–CLAT), direct peptide reactivity assay (DPRA), and KeratinoSens™, surface plasmon resonance (SPR) matched the categorization of LLNA in the following descending order: 96%, 92%, 82%, 70%, 70%, and 12%. With just an 8% mismatch with LLNA data, the EIS approach used in this study could be used as a screening tool for skin sensitizers.

Porous graphene oxide based disposable non-enzymatic electrochemical sensor for the determination of nicotinamide adenine dinucleotide

Electrochemical detection of β-nicotinamide adenine dinucleotide (NADH) has fascinated the scientific community due to its significance in pharmaceuticals, food supplements as well as in various biological reactions and pathways. Herein, a facile and low-cost disposable non-enzymatic electrochemical sensor for the selective and sensitive determination of NADH was developed using porous graphene oxide (PGO) modified screen printed carbon electrode (SPE). PGO has received growing attention owing to its high internal porosity, improved conductivity, large surface area, excellent stability, improved active sites, and hence expected to show excellent electrocatalytic activity than graphene and other derivatives of carbon. Firstly, graphene oxide (GO) sheets were synthesized, after which pores were created on these GO sheets through simple base reduction and acid treatment and the pore formation was confirmed using different characterization techniques. The PGO was directly dropcasted on the surface of SPE to form PGO/SPE and the fabricated electrode demonstrated eminent electrocatalytic activity towards NADH oxidation. Further, the fabricated sensor has shown significant response over a broad-range of concentration from 30 to 1071 μM with a good sensitivity of 21.83 μA mM −1 cm −2 and a low detection limit of 8.6 μM. Moreover, the fabricated PGO/SPE has advantages like cost-effectiveness, robustness, disposability, ease of fabrication, high stability, and excellent reproducibility. • Porous graphene oxide was synthesized via base reduction and acidification. • Fabricated a disposable electrochemical sensor by dropcasting PGO on SPE (PGO/SPE) • PGO/SPE effectively utilized for the electrocatalytic oxidation of NADH. • Compared to GO/SPE and ERGO/SPE, PGO/SPE showed superior analytical performance. • PGO/SPE exhibits good selectivity for NADH with excellent stability and sensitivity.

Highly Sensitive Electrochemical Detection of Tyramine Using a Poly(Toluidine Blue)-Modified Carbon Screen-Printed Electrode

Tyramine (4-hydroxyphenethylamine) is a biogenic amine commonly found in alcoholic beverages or fermented and dried foods. A healthy person can consume about 200–800 mg per single oral intake. Increased tyramine consumption can lead to serious health problems, especially in people with food allergies. Therefore, measurements of tyramine levels are an immediate concern. In this study, the electroactive dye polymer toluidine blue was used as a new sensor material for the rapid determination of tyramine, for which it was immobilized on carbon screen printing electrodes (SPEs). Toluidine blue (TB) 0.5 mM was electrochemically polymerized on the screen-printed electrode surface by the cyclic voltammetric method. Under optimal conditions, the poly-TB modified carbon SPE showed the tyramine oxidation peak at 0.67 V, while the bare carbon SPE showed the same tyramine oxidation peak at 0.9 V. With the modified one, tyramine can be detected over a wide linear range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.02~ \mu \text{M}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$270.5~ \mu \text{M}$ </tex-math></inline-formula> , with a low detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.007~ \mu \text{M}$ </tex-math></inline-formula> (S/N = 3) and a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.78~ \mu \text{A}$ </tex-math></inline-formula> nM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> found. A tyramine concentration of at least <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.02~ \mu \text{M}$ </tex-math></inline-formula> is recommended for real sample analysis. Our developed sensor showed good selectivity to tyramine in the presence of other biogenic amines such as dopamine (DA), L-cystine (L-CY), putrescine (PU), and histamine (HIS), which are commonly found in real samples. The sensor described offers unique advantages such as low manufacturing cost, ease of use, reusability, good sensitivity and high selectivity over other biogenic amines.

Haptenation of skin sensitizers with cysteine and gold nanoparticles modified screen printed carbon electrode analyzed using impedance technique

Skin sensitization is defined as an allergic response to a skin sensitizer upon contact with the skin. Skin sensitization is induced through covalent binding of a skin sensitizer to skin proteins (haptenation process). In this research work, the working electrodes of screen printed carbon electrodes (SPCEs) were modified by electrodepositing gold nanoparticles (AuNPs), addition of thiourea and then followed by self–assembly of AuNPs and cysteine (designated as ETSC). The main purpose of this research was to study the interaction of skin sensitizers with the cysteine and gold nanoparticles modified screen printed carbon electrode (SPCE) analyzed using impedance technique. The interaction of maleic anhydride (as extreme/strong skin sensitizer) with the cysteine modified SPCE was found to result in high changes in the value of charge transfer resistance of skin sensitizer (ΔRCTskinsensitizer) compared to moderate sensitizer (isoeugenol) and weak/non skin sensitizer (glycerol). The ETSC modified SPCE with skin sensitizers were characterised using Fourier–Transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The presence of skin sensitizers on the working electrode of ETSC modified electrode was detected by FTIR–ATR. AFM images indicated different patterns with different surface roughness for extreme/strong, moderate and weak/non skin sensitizers. Using EIS, the estimation for fractional surface coverage (θIS) of ETSC modified SPCE when contacted with maleic anhydride was higher than isoeugenol and glycerol. Other than that, the active site radius (ra), and the distance between two adjacent sites (2rb) for ETSC modified SPCE when contacted with maleic anhydride were shorter than the ra and 2rb obtained for isoeugenol and glycerol, indicating higher surface average roughness for ETSC modified SPCE that was contacted with maleic anhydride. Data obtained from EIS agreed with images obtained using AFM. The adsorption kinetic studies for ETSC modified SPCE with skin sensitizers showed that the skin sensitizers displayed Langmuir isotherm adsorption. This work showed that the ETSC modified SPCE has the potential to be employed for the screening of potential skin sensitizers during the early stage of cosmetic and personal care products development.

Silver nanoparticles decorated functionalized multiwalled carbon nanotubes modified screen printed sensor for the voltammetric determination of butorphanol

The present study aimed at describing silver nanoparticles based functionalized multiwalled carbon nanotubes modified screen printed carbon electrode (Ag/CNT/SPE) for an effective determination of an opioid analgesic drug butorphanol (BTR). The suspension of Ag/CNT prepared was drop casted onto the surface of SPE. The surface morphology of the nanocomposite was studied using XRD, FESEM, EDX, FT-IR, and UV-Vis. Ag/CNT/SPE showed a remarkable enhancement in the peak current values in cyclic and square wave voltammograms when compared with that of the CNT/SPE, Ag/SPE and bare carbon SPE. The anodic phenomenon of BTR occurring at Ag/CNTs/SPE was found to be a function of pH of the medium, concentration and scan rate of BTR. The oxidation peak current was found proportional to the BTR concentration within the linear range of 1.05-10.45 µM, with a detection limit of 2.15 µM (LOD) and the quantification limit of 7.18 µM (LOQ). The redox mechanism of BTR at the modified electrode was evaluated after optimizing the electrode dynamic parameters. The sensor was further scrutinized for the successful quantification of BTR in the pharmaceutical formulation.

Biosensing of catechol via amperometry using laccase immobilized nickel oxide/graphite modified screen-printed electrodes

In the present work, we have developed a modified screen-printed carbon electrode (SPE) based biosensor to detect catechol using nickel oxide/graphite (NiO/G) immobilized with laccase as bio-nanocomposite coating. The laccase immobilized NiO/G composite increased the effective Randles-Sevcik surface area from 0.034 cm2 to 0.083 cm2 compared to bare SPE, resulting in improved electrochemical activity and enhanced reversible catechol oxidation process. Impedance spectroscopic data for the modified SPE (MSPE) showed faster electron transfer than the bare counterpart suggesting the successful immobilization of the bio-nanocomposite onto the electrode surface. Consequently, the cyclic-voltammograms of laccase MSPE exhibited a sharp decrease in the peak-to-peak separation potential and an increase in the current responsiveness. We further, utilized the chronoamperometric method to quantify the catechol detection under optimal conditions, and found a linear biosensor response over the concentration region of 1–100 µM. The sensor's lower detection limit, response time, and sensitivity towards catechol were found to be 65 nM, 3 s, and 1.51 µAµM-1cm−2, respectively. These results suggest that the laccase immobilized NiO/G MSPE as one of the most promising customized electrodes for catechol biosensing.

Graphene Decorated Gold Nanoparticles Modified Screen-Printed Carbon Electrode for Detection of Pork Adulteration

Graphene Decorated Gold Nanoparticles Modified Screen-Printed Carbon Electrode for Detection of Pork Adulteration

Noble-metal-free Fe3O4/Co3S4 nanosheets with oxygen vacancies as an efficient electrocatalyst for highly sensitive electrochemical detection of As(III)

The electrochemical method for highly sensitive determination of arsenic(III) in real water samples with noble-metal-free nanomaterials is still a difficult but significant task. Here, an electrochemical sensor driven by noble-metal-free layered porous Fe3O4/Co3S4 nanosheets was successfully employed for As(III) analysis, which was prepared via a facile two-step method involves a hydrothermal treatment and a subsequent sulfurization process. As expected, the electrochemical detection of As(III) in 0.1 M HAc-NaAc (pH 6.0) by square wave anodic stripping voltammetry (SWASV) with a considerable sensitivity of 4.359 μA/μg·L−1 was obtained, which is better than the commonly used noble metals modified electrodes. Experimental and characterization results elucidate the enhancement of As(III) electrochemical performance could be attributed to its nano-porous structure, the presence of oxygen vacancies and strong synergetic coupling effects between Fe3O4 and Co3S4 species. Besides, the Fe3O4/Co3S4 modified screen printed carbon electrode (Fe3O4/Co3S4-SPCE) shows remarkable stability and repeatability, valuable anti-interference ability and could be used for detection in real water samples. Consequently, the results confirm that as-prepared porous Fe3O4/Co3S4 nanosheets is identified as a promising modifier to detect As(III) in real sample analysis.

Highly selective voltammetric detection of antipsychotic drug thioridazine hydrochloride based on NiO@Gd2O3 modified screen printed carbon electrode

• NiO@Gd 2 O 3 was synthesized via the facile co-precipitation method. • Modified sensor were studied by CV and DPV techniques for TRH detection. • NiO@Gd 2 O 3 electrode displayed WLR, low LOD, and excellent sensitivity. • The fabricated sensor shows good selectivity in MT, DA, UA, and CPZ towards TRH. The construction of mixed metal oxides matrix acts as highly active electrode materials in the field of an electrochemical sensor, owing to high conductivity, a large number of active sites, fast kinetics, and superior sensing activity. In this study, the spherical-like NiO@Gd 2 O 3 (NGO) microstructures were successfully synthesized by a simple co-precipitation method and employed for the selective electrochemical detection of thioridazine hydrochloride (TRH). The as-prepared NGO-500 material was confirmed with suitable spectrometric techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy, Brunauer–Emmett–Teller (BET) method, field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS) analyses. The electrocatalytic performance of TRH on modified screen-printed carbon electrode (NGO-500/SPCE) was investigated through cyclic voltammetric (CV), and differential pulse voltammetric (DPV) methods. As a result, the proposed electrode demonstrated a wide linear response of 0.04–151.6 µM, a low detection limit of 0.004 µM with an excellent sensitivity of 3.09 µA µM −1 cm −2 . Besides, the modified electrode establishes outstanding selectivity in the presence of the various interfering compounds towards TRH detection. The fabricated electrode displayed notable repeatability, reproducibility, acceptable cyclic and storage stability. The feasibility of the NGO-500 electrode was used to sense TRH in urine and serum samples with satisfactory results.

Detection of circulating prostate cancer cells via prostate specific membrane antigen by chronoimpedimetric aptasensor

Abstract Objectives Sensitive and accurate techniques for early detection of prostate cancer, which has a good chance for successful treatment if detected early, are of utmost value. Our aim is to develop a sensitive chronoimpedimetric biosensor for detection of circulating prostatic tumor cells (CTCs) with an aptamer selective for prostate specific membrane antigen (PSMA). Methods Thiolated PSMA-specific aptamer was immobilized on the gold nanoparticle modified carbon screen-printed electrodes. After characterization with cyclic voltammetry and electrochemical impedance spectrometry, scanning electron microscopy and atomic force microscopy studies were conducted to confirm the modifications. LNCaP cells (androgen-sensitive human prostate adenocarcinoma cells), were then added to the serum samples and chronoimpedimetric detection of CTCs in samples were performed. Results Our study showed one cell detection capability in real serum samples with a linear range from 1 to 40 cells/mL. The incubation time was 130 s. LOD was found to be 0.62 cells/mL and relative standard deviations were lower than 2% RSD. Reproducibility tests indicated a regression coefficient as R2 = 0.9963 ± 0.0178. Conclusions This new biosensor enables rapid, accurate, precise, reproducible and highly sensitive detection of PSMA on CTCs in prostate cancer and paves the way to new diagnostic applications and research-based studies.

A Redox Cu(II)-Graphene Oxide Modified Screen Printed Carbon Electrode as a Cost-Effective and Versatile Sensing Platform for Electrochemical Label-Free Immunosensor and Non-enzymatic Glucose Sensor.

A novel copper (II) ions [Cu(II)]-graphene oxide (GO) nanocomplex-modified screen-printed carbon electrode (SPCE) is successfully developed as a versatile electrochemical platform for construction of sensors without an additionally external redox probe. A simple strategy to prepare the redox GO-modified SPCE is described. Such redox GO based on adsorbed Cu(II) is prepared by incubation of GO-modified SPCE in the Cu(II) solution. This work demonstrates the fabrications of two kinds of electrochemical sensors, i.e., a new label-free electrochemical immunosensor and non-enzymatic sensor for detections of immunoglobulin G (IgG) and glucose, respectively. Our immunosensor based on square-wave voltammetry (SWV) of the redox GO-modified electrode shows the linearity in a dynamic range of 1.0–500 pg.mL−1 with a limit of detection (LOD) of 0.20 pg.mL−1 for the detection of IgG while non-enzymatic sensor reveals two dynamic ranges of 0.10–1.00 mM (sensitivity = 36.31 μA.mM−1.cm−2) and 1.00–12.50 mM (sensitivity = 3.85 μA.mM−1.cm−2) with a LOD value of 0.12 mM. The novel redox Cu(II)-GO composite electrode is a promising candidate for clinical research and diagnosis.

Disposable Electrochemical Sensor for Food Colorants Detection by Reduced Graphene Oxide and Methionine Film Modified Screen Printed Carbon Electrode.

A facile synthesis of reduced graphene oxide (rGO) and methionine film modified screen printed carbon electrode (rGO-methionine/SPCE) was proposed as a disposable sensor for determination of food colorants including amaranth, tartrazine, sunset yellow, and carminic acid. The fabrication process can be achieved in only 2 steps including drop-casting of rGO and electropolymerization of poly(L-methionine) film on SPCE. Surface morphology of modified electrode was studied by scanning electron microscopy (SEM). This work showed a successfully developed novel disposable sensor for detection of all 4 dyes as food colorants. The electrochemical behavior of all 4 food colorants were investigated on modified electrodes. The rGO-methionine/SPCE significantly enhanced catalytic activity of all 4 dyes. The pH value and accumulation time were optimized to obtain optimal condition of each colorant. Differential pulse voltammetry (DPV) was used for determination, and two linear detection ranges were observed for each dye. Linear detection ranges were found from 1 to 10 and 10 to 100 µM for amaranth, 1 to 10 and 10 to 85 µM for tartrazine, 1 to 10 and 10 to 50 µM for sunset yellow, and 1 to 20 and 20 to 60 µM for carminic acid. The limit of detection (LOD) was calculated at 57, 41, 48, and 36 nM for amaranth, tartrazine, sunset yellow, and carminic acid, respectively. In addition, the modified sensor also demonstrated high tolerance to interference substances, good repeatability, and high performance for real sample analysis.

An expedition of WBiVO4 blended f-MWCNTs nanocomposite for enhanced electrochemical detection of non-steroidal anti-inflammatory drug acetaminophenol

The fabrication of modifier nanocomposite are evidently important, because it delivers a highly sensitive and selective methodology for the electrochemical determination of drugs. Herein, we introduce a novel modifier WBiVO4/f-MWCNTs- nanocomposites electrochemical sensor for the detection of Acetoaminophenol (ACP), which were synthesized using a facile hydrothermal method. We have scrutinized the structural, optical, morphological, and functional structures using various techniques, such as XRD, FTIR, Raman, TEM, FESEM, and XPS spectra. The resistive and the conductive natures also studied using EIS. We investigated the electrochemical behavior of the modified Screen Printed Carbon Electrode (SPCE) by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). In which WBiVO4/f-MWCNT proved to be highly sensitive and selective towards the detection of ACP. Sensitive electro-oxidation peak potential at 0.39 mV from the DPV technique was observed for ACP. The double linear response over the range of 0.5–36.5 μM and 48.5–158.5 μM and the lower detection limits (LoD) of 0.0822 µM were recorded for ACP. The applicability of the WBiVO4/f-MWCNT/SPCE investigated towards the detection of the ACP in commercial drug sample.

Electrochemical Detection of Ascorbic acid in Orange on Iron(III) Oxide Nanoparticles Modified Screen Printed Carbon Electrode

This study reports the electrochemical detection of ascorbic acid (AA) at screen printed carbon electrode (SPCE) modified with iron(III) oxide nanoparticle. Iron(III) nanoparticle was synthesized from Callistemon viminalis leaf extract (CV-Fe3O4NP). SPCE/CV-Fe3O4NP electrode showed faster electron transport in terms of the current response to AA oxidation compare to bare SPCE, which is due to the presence of CV-Fe3O4NP. The dynamic range for the detection of AA was from 10 to 100 μM. Limit of detection for AA on modified SPCE/CV-Fe3O4NP electrode was 15.7 μM which compared favorably with other electrodes investigated. The selectivity of the modified SPCE/CV-Fe3O4NP electrode was also determined. The designed sensor showed good selectivity to AA in the presence of interfering specie DA of same concentration (0.1 mM). Real sample analysis was carried out to establish the practical feasibility of the developed sensor (SPCE/CV-Fe3O4NP).

Haptenation of Skin Sensitizers with Cysteine and Gold Nanoparticles Modified Screen Printed Carbon Electrode Analyzed Using Impedance Technique

Skin sensitization is defined as an allergic response to a skin sensitizer upon contact with the skin. Skin sensitization is induced through covalent binding of a skin sensitizer to skin proteins (haptenation process). In this research work, screen printed carbon electrodes (SPCEs) were modified by electrodepositing gold nanoparticles (AuNPs), addition of thiourea and then followed by self–assembly of AuNPs and cysteine (designated as ETSC). The main purpose of this research was to study the interaction of skin sensitizers with the cysteine and gold nanoparticles modified screen printed carbon electrode (SPCE) analyzed using impedance technique. The interaction of maleic anhydride (as extreme/strong skin sensitizer) with the cysteine modified SPCE was found to result in high changes in the value of charge transfer resistance of skin sensitizer (ΔRskin sensitizer] compared to moderate sensitizer (isoeugenol) and weak/non skin sensitizer (glycerol). The ETSC modified SPCE with skin sensitizers were characterized using atomic force microscopy (AFM), Fourier–Transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR), and electrochemical impedance spectroscopy (EIS). Using EIS, the estimation for fractional surface coverage (θIS) of ETSC modified SPCE when contacted with maleic anhydride was higher than isoeugenol and glycerol. Other than that, the active site radius (ra), and the distance between two adjacent sites (2rb) for ETSC modified SPCE when contacted with maleic anhydride were shorter than the ra and 2rb obtained for isoeugenol and glycerol, indicating higher surface average roughness for ETSC modified SPCE that was contacted with maleic anhydride. AFM images agreed with the calculated values of surface roughness, indicating different patterns for extreme/strong, moderate and weak/non skin sensitizers. The adsorption kinetic studies for ETSC modified SPCE with skin sensitizers showed that the skin sensitizers displayed Langmuir isotherm adsorption. This work showed that the ETSC modified SPCE has the potential to be employed for the screening of potential skin sensitizers during the early stage of cosmetic and personal care products development.

Voltammetric Determination of Trace Methyl Parathion Using Electrochemically Reduced Graphene Oxide Modified Carbon Screen-Printed Electrodes

Voltammetric Determination of Trace Methyl Parathion Using Electrochemically Reduced Graphene Oxide Modified Carbon Screen-Printed Electrodes