Disposable Screen-printed Electrodes Research Articles

Electrical Wiring of Malarial Parasite Intermediate Hematin on a Tailored N-Doped Carbon Nanomaterial Surface and Its Bioelectrocatalytic Hydrogen Peroxide Reduction and Sensing.

Hematin, an iron-containing porphyrin compound, plays a crucial role in various biological processes, including oxygen transport, storage, and functionality of the malarial parasite. Specifically, hematin-Fe interacts with the nitrogen atom of antimalarial drugs, forming an intermediate step crucial for their function. The electron transfer functionality of hematin in biological systems has been scarcely investigated. In this study, we developed a biomimicking electrical wiring of hematin-Fe with a model N-drug system, represented as {hematin-Fe---N-drug}. We achieved this by immobilizing hematin on a multiwalled carbon nanotube (MWCNT)/N-graphene quantum dot (N-GQD) modified electrode (MWCNT/N-GQD@Hemat). N-GQD serves as a model molecular drug system containing nitrogen atoms to mimic the {hematin-Fe---N-drug} interaction. The prepared bioelectrode exhibited a distinct redox peak at a measured potential (E1/2) of -0.410 V vs Ag/AgCl, accompanied by a surface excess value of 3.54 × 10-9 mol cm-2. This observation contrasts significantly with the weak or electroinactive electrochemical responses documented in literature-based hematin systems. We performed a comprehensive set of physicochemical and electrochemical characterizations on the MWCNT/N-GQD@Hemat system, employing techniques including FESEM, TEM, Raman spectroscopy, IR spectroscopy, and AFM. To evaluate the biomimetic electrode's electroactivity, we investigated the selective-mediated reduction of H2O2 as a model system. As an important aspect of our research, we demonstrated the use of scanning electrochemical microscopy to visualize the in situ electron transfer reaction of the biomimicking electrode. In an independent study, we showed enzyme-less electrocatalytic reduction and selective electrocatalytic sensing of H2O2 with a detection limit of 319 nM. We achieved this using a batch injection analysis-coupled disposable screen-printed electrode system in physiological solution.

New methodological approach for deep penetrating geochemistry and environmental studies part 2: field determination of Co(II) /Ni(II) and Pb(II) /Zn(II) of on-site soil extractions by electrochemical stripping techniques

In the framework of deep penetrating geochemistry for mineral exploration, we report a field electroanalytical method using disposable screen-printed working electrodes able to quantify metal pathfinders in partial extracts of soil samples at the nanomolar level on site. Four metal pathfinders (Co, Ni, Pb, Zn) were chosen due to their geological interest and suitability of electrochemical detection. Square Wave Anodic Stripping Voltammetry (SW-ASV) was developed for the simultaneous detection of Pb(II) and Zn(II) providing limits of detection (LODs) of 1.2 nM and 5.3 nM respectively. A linear scan-cathodic stripping voltammetry (LS-CSV) methodology was developed for the joint detection of Co(II) and Ni(II) yielding LODs of 1.8 nM and 3.5 nM respectively. Method validation was carried out on 14 upper B-horizon soil samples during a field survey. Two wet extraction procedures were applied for soil samples - a strong extraction using HNO 3 and a weak extraction with CaCl 2 . Excellent agreement between electroanalytical methods and ICP-MS was found for Pb(II) while a small underestimation was observed for Zn(II). For Co(II) and Ni(II), the LS-CSV measurements in the HNO 3 extractions were impossible due to the change from low pH to pH to 7.15 which induces precipitation of the Fe and Al. For the CaCl 2 extractions, the Co(II)/Ni(II) results obtained by LS-CSV were in excellent agreement with ICP-MS measurements. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7188747

Disposable graphene-oxide screen-printed electrode integrated with portable device for detection of SARS-CoV-2 in clinical samples

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis is the need of the hour, as cases are persistently increasing, and new variants are constantly emerging. The ever-changing nature of the virus leading to multiple variants, has brought an imminent need for early, accurate and rapid detection methods. Herein, we have reported the design and fabrication of Screen-Printed Electrodes (SPEs) with graphene oxide (GO) as working electrode and modified with specific antibodies for SARS-CoV-2 Receptor Binding Domain (RBD). Flexibility of design, and portable nature has made SPEs the superior choice for electrochemical analysis. The developed immunosensor can detect RBD as low as 0.83 fM with long-term storage capacity. The fabricated SPEs immunosensor was tested using a miniaturized portable device and potentiostat on 100 patient nasopharyngeal samples and corroborated with RT-PCR data, displayed 94 % sensitivity. Additionally, the in-house developed polyclonal antibodies detected RBD antigen of the mutated Omicron variant of SARS-CoV-2 successfully. We have not observed any cross-reactivity/binding of the fabricated immunosensor with MERS (cross-reactive antigen) and Influenza A H1N1 (antigen sharing common symptoms). Hence, the developed SPEs sensor may be applied for bedside point-of-care diagnosis of SARS-CoV-2 using miniaturized portable device, in clinical samples.

Sensitive determination of iodide at graphitic carbon nitride-chitosan composite modified screen-printed electrode in urine and salt using cathodic stripping voltammetry

Iodide is an important constituent in various biological processes; hence its determination is important. A simple voltammetric method has been investigated for iodide determination using disposable screen-printed electrode modified with graphitic carbon nitride-chitosan composite (gCN-Chit/SPE). The sensor presented excellent electrocatalytic response towards iodide sensing. The SEM analysis of the modified electrode showed a rough and sheet like morphology. The EDX analysis showed the high content of nitrogen elements in the composite layer of the modified electrode which is crucial for iodide ion sensing. Various parameters such as electrolyte concentration, deposition potential, deposition time etc. were optimized for iodide sensing. The use of low concentration of electrolyte favored the electro-oxidation of iodide. Under the suitable experimental conditions, the gCN-Chit/SPE exhibited good linear performance for iodide in the concentration range from 0.075 to 200 µM with a regression coefficient (R2) of 0.9946 and the limit of detection (LOD) of 0.01 µM. The electrode presented interference free effect for iodide in the presence of relatively high concentration of other substances. The sensor was applied to determine iodide in real samples such as urine, tap water and table salt. In real sample analysis good recoveries in percent was achieved using the developed electrode. Further, the composite layer at the electrode surface provided good mechanical stability and thus could be reused for several determinations. The results confirmed that the design electrochemical sensor could be successfully employed for real sample applications with highly sensitive iodide determination.

Nano-palladium-decorated bismuth sulfide microspheres on a disposable electrode integrated with smartphone-based electrochemical detection of nitrite in food samples

Nitrite (NO2−) is widely used as an additive to extend the shelf life of food products. Excessive nitrite intake not only causes blood-related diseases but also has the potential risk of causing cancers. A disposable screen-printed electrode was modified with nano‑palladium decorated bismuth sulfide microspheres (nanoPd@Bi2S3MS/SPE), and integrated with a smartphone-interfaced potentiostat to develop a portable, electrochemical nitrite sensor. NanoPd@Bi2S3MS was prepared by the hydrothermal reduction of a Bi2S3MS and Pd2+ dispersion and drop cast on the SPE. The nanoPd@Bi2S3MS/SPE was coupled with a smartphone-controlled portable potentiostat and applied to determine nitrite in food samples. The linear range of the sensor was 0.01–500 μM and the limit of detection was 0.0033 μM. The proposed system showed good repeatability, reproducibility, catalytic stability, and immunity to interferences. The proposed electrode material and a smartphone-based small potentiostat created a simple, portable, fast electrochemical sensing system that accurately measured nitrite in food samples.

Development of a new highly sensitive electrochemical sensor to piroxicam anti-inflammatory determination using a disposable screen-printed electrode

Development of a new highly sensitive electrochemical sensor to piroxicam anti-inflammatory determination using a disposable screen-printed electrode

Highly sensitive and disposable screen-printed graphene-based electrochemical sensor coupled with monolithic micro-solid-phase extraction for the determination of 3,4-methylenedioxymethamphetamine in forensic applications

The development of a productive assay to quantify 3,4-methylenedioxymethamphetamine (MDMA) levels in human urine samples is crucial in forensic applications. In this work, we examine the use of a disposable screen-printed graphene electrode coupled with in-tip monolithic micro-solid-phase extraction (µ-SPE) for the highly selective and sensitive determination of MDMA. To satisfy this requirement, we employ a sensor based on graphene nanomaterials integrated into a compact electrochemical device to enhance the sensitivity. In-tip monolithic µ-SPE is a facile and highly effective route for extraction and preconcentration (enrichment factor ∼ 10) to improve the sensitivity. The combination of our µ-SPE and an electrochemical sensor exhibits a remarkable performance in terms of sensitivity and selectivity for MDMA analysis. A wide linear range is observed within 0.10–10.00 µg mL−1, and the lowest limit of detection is calculated to be 0.03 µg mL−1. Moreover, no interference effect from other substances is observed for MDMA detection. The feasibility of the proposed assay is evaluated, and it is successfully used in MDMA determination in human urine samples with high accuracy, precision, reproducibility, stability, and reliability. Therefore, this novel proposed method is well suited as a compact disposable device for MDMA determination in forensic applications and can be employed by relevant government organizations to correctly identify MDMA levels in narcotic addicts.

Deaeration of incubation buffer to minimize electrochemical impedance spectroscopy signal drift on screen-printed gold electrodes and its use for label-free detection of vancomycin

Disposable screen-printed gold electrodes (SPAuEs) are used for the development of numerous immunosensors owing to their ease of modification with biorecognition molecules. A major limitation in the development of SPAuEs based biosensors is the single-use of the electrodes leading to higher costs for sensor development, whereas multiple measurements can affect the sensor stability and reproducibility. Especially, label-free electrochemical impedance spectroscopy (EIS) based SPAuEs sensors are prone to signal drift resulting in false-positive or false-negative data questioning the reliability of the assay. We found that repeated EIS measurements on SPAuEs in ferri- and ferrocyanide solution yielded a significant increase in resistance to charge transfer (Rct) value (positive signal drift) even in a control solution (without the target analyte). The positive signal drift follows the typical pattern of a concentration-dependent calibration curve, rendering repeated measurement error-prone for sensing purposes. In this study, it is shown that the incubation of the SPAuEs in nitrogen purged deaerated phosphate buffered saline (N-PBS) minimized this signal drift in repeated/multiple EIS measurements. This method was then used to develop a peptide-based EIS biosensor for the detection of Vancomycin, a last-line antibiotic used for the treatment of severe multidrug-resistant bacterial infection. This protocol can be followed for the biosensing of other clinically important biomarkers.

An electrochemically synthesized molecularly imprinted polymer for highly selective detection of breast cancer biomarker CA 15-3: a promising point-of-care biosensor.

In this study, a molecularly imprinted polymer film (MIP) was prepared on the surface of a disposable carbon screen-printed electrode (C-SPE) using (3-acrylamidopropyl)trimethylammonium chloride (AMPTMA) as a functional monomer and the cancer biomarker carbohydrate antigen 15-3 (CA 15-3) as a template. The MIP was synthesized by in situ electropolymerization (ELP) of the AMPTMA monomer in the presence of the CA 15-3 protein on the C-SPE surface. The target was subsequently removed from the polymer matrix by the action of proteinase K, resulting in imprinted cavities with a high affinity for CA 15-3. Electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the different phases of the sensor assembly. Chemical and morphological analysis was performed using RAMAN and scanning electron microscopy (SEM). CA 15-3 was successfully detected in a wide working range from 0.001 U mL-1 to 100 U mL-1 with a correlation coefficient (R2) of 0.994 in 20 min. The MIP sensor showed minimal interference with other cancer proteins (CEA and CA 125). Overall, the developed device provides a rapid, sensitive, and cost-effective response in the detection of CA 15-3. Importantly, this comprehensive approach appears suitable for point-of-care (PoC) use, particularly in a clinical context.

Low-Cost Platforms for Point-of-Use Sensors

Electrochemical biosensors are promising for sensing in low-resource settings because they are easy use and low-cost. Disposable screen-printed electrodes are popular for biosensing applications, but the dopants in the ink used for gold electrode production can interfere with electrode modification and sensing. We have developed an alternative disposable electrode made from high-quality gold leaf. We compared the topology and performance of three different disposable gold electrodes: our gold leaf electrodes and two commercial screen-printed versions. Our electrodes consistently outperformed commercial electrodes for biosensing, and we have further expanded these electrodes for the detection of infectious disease. In contrast, carbon screen-printed electrodes tend to be lower cost and higher quality than their gold counterparts. However, chemistry to modify them with biomolecules remains more challenging than self-assembly on gold. We have therefore developed new chemistries to enable the facile modification of these electrodes with biomolecules and have successfully applied these modified electrodes for environmental sensing. Together, these works demonstrate the importance of fundamental advances in platform design to enable improved technologies.

Disposable Molecularly Imprinted Polymer-Modified Screen-Printed Electrodes for Rapid Electrochemical Detection of l-Kynurenine in Human Urine.

l-Kynurenine (l-Kyn) is an endogenous metabolite produced in the catabolic route of l-Tryptophan (l-Trp), and it is a potential biomarker of several immunological disorders. Thus, the development of a fast and cheap technology for the specific detection of l-Kyn in biological fluids is of great relevance, especially considering its recent correlation with SARS-CoV-2 disease progression. Herein, a disposable screen-printed electrode based on a molecularly imprinted polymer (MIP) has been constructed: the o-Phenylenediamine monomer, in the presence of l-Kyn as a template with a molar ratio of monomer/template of 1/4, has been electropolymerized on the surface of a screen-printed carbon electrode (SPCE). The optimized kyn-MIP-SPCE has been characterized via cyclic voltammetry (CV), using [Fe(CN)6)]3-/4- as a redox probe and a scanning electron microscopy (SEM) technique. After the optimization of various experimental parameters, such as the number of CV electropolymerization cycles, urine pretreatment, electrochemical measurement method and incubation period, l-Kyn has been detected in standard solutions via square wave voltammetry (SWV) with a linear range between 10 and 100 μM (R2 = 0.9924). The MIP-SPCE device allowed l-Kyn detection in human urine in a linear range of 10-1000 μM (R2 = 0.9902) with LOD and LOQ values of 1.5 and 5 µM, respectively. Finally, a high selectivity factor α (5.1) was calculated for l-Kyn toward l-Trp. Moreover, the Imprinting Factor obtained for l-Kyn was about seventeen times higher than the IF calculated for l-Trp. The developed disposable sensing system demonstrated its potential application in the biomedical field.

Application of superhydrophobic Ti3C2 Mxene-based screen-printed ion-selective electrode for determination of Ca2+ concentration

Ti3C2 Mxene is a remarkable electrochemical material owing to its high conductivity, large specific surface area, and high electrical capacity. It can be applied in all-solid-state ion-selective electrodes to improve the ion-electron conversion efficiency and reduce the resistance. However, Ti3C2 Mxene is hydrophilic, which will form a water layer between the ion-selective membrane and the substrate, resulting in response potential drift. In this study, Ti3C2 Mxene functionalized with octadecyltrichlorosilane was developed as the ion-electron conversion layer (solid contact layer), and a polymer membrane containing N, N, N', N' -Tetracyclohexyl-3-oxapentanediamide was used as the Ca2+ selective membrane on a screen-printed electrode substrate. An all-solid Ca2+-selective electrode (SPE/SH-Ti3C2/Ca-ISM) was prepared. The results from cyclic voltammetry and electrochemical impedance spectroscopy proved the high capacitance and fast charge transfer ability of the Ti3C2 Mxene modified electrode. In addition, it shows good performance in the water layer test and anti-interference test and improves the response speed and stability of potential. The linear response range of this disposable screen-printed electrode to Ca2+ is 10−6∼10−1 M, the detection limit is 10−6.2 M, and the response time is about 15 s. The electrode can accurately and quickly determine the level of Ca2+ in serum samples of dairy cows.

Designing disposable hand-made screen-printed electrode using conductive ink for electrochemical determination of dopamine

Designing disposable hand-made screen-printed electrode using conductive ink for electrochemical determination of dopamine

Disposable Nanosensor for the Electrochemical Determination of Temozolomide and İts Interaction with Double-Stranded DNA

Novel disposable screen-printed electrodes modified with silicon dioxide nanoparticles were developed for the electrochemical determination of temozolomide and its interaction with DNA. The characterization of silicon dioxide nanoparticles (SiNPs) was conducted by transmission electron microscopy and energy-dispersive x-ray spectroscopy (EDX). The EDX measurements show that the silicon nanoparticles consisted of 53.08% oxygen (O) and 46.92% silicon (Si), confirming their purity. Chemical characterization was conducted using Fourier transform infrared spectroscopy. Surface characterization of SiNPs-modified screen-printed electrodes was performed using atomic force microscopy. SiNP modification was demonstrated to increase the electrode surface area by 2.3-folds, from 0.75 × 10−3 cm2 to 1.75 × 10−3 cm2, resulting in an enhanced signal. The detection limit was 5.6 µg/mL for temozolomide and 7.2 µg/mL for DNA, respectively. The linear concentration range was from 18.6 to 200 µg/mL for temozolomide and 23.9 to 80 µg/mL for DNA.

Disposable nanosensor for the electrochemical determination of the interaction between DNA, and a mycotoxin, patulin

Silicon dioxide nanoparticles were synthesized and disposable screen-printed electrodes were modified with these nanoparticles to electrochemically detect the interaction between DNA and patulin, a mycotoxin. Firstly, the synthesized silicon dioxide nanoparticles were chemically characterized by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Microscopic characterization of the nanoparticles was performed by Transmission Electron Microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDX). The surface of the silicon dioxide nanoparticle-modified screen-printed electrode was characterized by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SiNP modification resulted in a 2-fold increase in surface area and a 2.3-fold enhancement in the signal. The detection limit (LOD) for the electrochemical patulin determination was calculated as 1.15 µg/mL, and the linear concentration range was found to be 3.2–20 µg/mL. The mode of interaction between patulin and dsDNA was determined through a molecular docking study. After the interaction between patulin and dsDNA, approximately 86 % and 23 % decreases were observed in patulin and guanine oxidation signals, respectively. The S % value for patulin was calculated by utilizing the decrease in the guanine signal after the interaction.

Non-Enzymatic Electrochemical Sensors for Accurate and Accessible Uric Acid Detection

Gout arthritis, a painful condition characterized by the accumulation of uric acid (UA) crystals in the joints, necessitates the development of efficient and accessible diagnostic methods. In this study, we present the design and fabrication of non-enzymatic electrochemical sensors based on molecularly imprinted conducting polymer nanostructures for the selective detection and monitoring of UA. To overcome the limitations of current point-of-care (POC) diagnostics, we developed a disposable voltammetric sensor capable of selectively and accurately analyzing UA concentrations at room temperature and pH 7.4. The sensor utilizes a selective polythiophene layer, deposited on disposable screen-printed electrodes, for the reversible binding and recognition of UA. Extensive electrochemical measurements employing electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) demonstrate excellent UA sensing performance in the wider concentration range of 1–500 μM using a standard redox solution with 2.91 μA cm−2·μM−1 sensitivity, 354 nM detection limit, and substantial selectivity over common interferents. The sensor is capable of analyzing complex mixtures such as human saliva with 90.4% recovery of the spiked UA concentration. This highly sensitive and cost-efficient electrochemical sensor offers great promise for POC testing, disease monitoring, and predicting treatment outcomes related to gout arthritis.

EIS and Amperometric Analysis of Gold Nanoparticle Probes on the Immunosensor Surface

[Introduction]Biosensing systems with integrated nanomaterials have revolutionized technological advancements in recent decades. Gold nanoparticles (AuNPs) in particular have been widely used in electrochemical sensors owing to their stability and unique characteristics. Previously, we developed biosensors that utilize the redox activity of AuNPs. Briefly, antibody-modified AuNPs not only hold secondary antibodies to react with antigens and primary antibodies on the electrode but also supply redox signals. We specially call this biosensing method Gold-Linked Electrochemical ImmunoAssay (GLEIA). In recent years, GLEIA has evolved uniquely in combination with other nanomaterials. However, information regarding the optimal electrochemical measurement conditions and the relationship between the electrode surface and AuNPs remain unknown. In this study, we quantitatively determined kinetic parameters such as the diffusion coefficient and electron transfer rate in the redox reaction of AuNPs on disposable screen-printed electrodes. Furthermore, the relationship between the addition of antibodies and the decrease in the determined parameters could be deduced. This is useful for the determination of the fine balance between the sensitivity and specificity.[Experimental]Electrochemical characteristics of AuNPs were performed using the following method, where 2 µL of AuNPs solution was dropped onto the working electrode and allowed to dry spontaneously. The number of AuNPs on each electrode was calculated from the datasheet (2.6 x 1010 particles/mL, O.D. 520 =1.0), and all nanoparticles were assumed to have dried on the working electrode. To characterize the reduction current, the AuNPs on the electrode underwent a pre-oxidation process, followed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) to evaluate the reduction current. The pre-oxidation condition was set at 1.2 V for 40 s, which was considered optimal for immunoassays. To evaluate the concentration response, 2 µL of the AuNPs solution was diluted with ultrapure water and poured and allowed to dry on the working electrode, pre-oxidized in 2 M KCl solution, and DPV measurements were performed. This experiment was also performed on an antibody-modified electrode, and the differences between the modified and unmodified electrodes were established. The same DPV measurements were performed using antibody-modified AuNPs (Ab-AuNPs).For immunoassay, IgA was reacted with a secondary antibody and incubated dropwise on an electrode. After washing, electrochemical measurements were performed[Results and Discussion]We investigated the influence of the DPV parameters and electrode surface conditions on a biosensor for the redox reaction of AuNPs. CV and classical theory were used to investigate the reduction kinetics of the AuNPs’ reduction after oxidation. The diffusion coefficient and electron transfer rate, which are related to sensor performance, were significantly reduced in the presence of antibodies and blocking agents on the electrode surface. This was due to the interaction between proteins and gold ions, and the effect of the electrode surface on sensitivity was evaluated using electrochemical reaction rates. Next, the influence of the biosensor on sensitivity was examined by focusing on the pulse amplitude of the DPV, and the increase in signal current coupled to increase in pulse amplitude was confirmed. The signal of AuNPs relative to the blank sample was of particular interest. Theoretically, changing the pulse potential above 100 mV does not change the current values obtained; however, in this study, a significant difference was observed between 150 mV and 100 mV. This was presumably due to the detection of nonspecific adsorption of antibodies that could not be detected under conventional conditions, suggesting the use of a more sensitive biosensor. This study provides evidence for fabrication of an IgA sensor with an improved Limit of detection (LOD) by optimizing pulse amplitude.Limits of detection (LOD) were obtained as 5.0 fmol/L (M) for AuNPs on a bare electrode, 0.1 pM for AuNPs on an antibody-modified electrodes, and 9.3 pM for AuNPs after immunoassay, allowing discussion of the given principle limits and actual biosensor performance (Figure). Under optimal conditions, the electrochemical biosensor achieved nearly two-fold signal amplification using a reduction current after AuNPs oxidation. These findings will allow the investigation of the kinetics of AuNPs on electrodes consisting of different materials to further elucidate the framework for improved sensitivity. Figure 1

Alkaline Hematin-Based Disposable Electrochemical Sensor for Haemoglobin

Estimating haemoglobin levels in the blood is crucial as it indicates various diseased conditions, including anaemia, cancers, and liver, kidney, and lung diseases. This paper presents the fabrication of an electrochemical biosensor to estimate haemoglobin in alkaline conditions. The rifting of the quaternary structure of the haemoglobin under high alkaline conditions paves the pathway for the formation of alkaline hematin. Graphite-kaolin clay composite electrocatalyst was synthesized and screen printed on a disposable electrode for the direct electrooxidation of alkaline hematin. The sensor exhibited high selectivity, linear responses over a concentration range from 10 to 80 μM, and a sensitivity of 43.26 μA μM−1 cm−2. The performance of the sensor was validated by testing it with whole blood samples. The novelty of the work lies in the direct electrooxidation of alkaline hematin on the disposable screen-printed electrode without any cell separation or cell lysing steps.

Synthesis and characterizations of ZIF-8/GO and ZIF-8/rGO composites for highly sensitive detection of Cu2+ ions

In this paper, we describe the synthesis and characterization of ZIF-8/GO and ZIF-8/rGO composites for electrochemical sensing of Cu2+ ions. To prepare the composites, GO or rGO was dispersed in a solution of Zn(NO3)2·6H2O and 2-methylimidazole in anhydrous methanol. We used several techniques, such as XRD, Raman spectroscopy, and FESEM, to investigate the structural, morphological, and chemical properties of the materials. The composites exhibited peaks corresponding to both ZIF-8 and GO or rGO in the XRD patterns. For the electrochemical analysis of Cu2+ ions, we employed a disposable screen-printed electrode (SPE). The ZIF-8/GO composite-based Cu2+ ion sensor exhibited superior sensitivity of 362.5 mA.µM-1.cm-2 and LOD of 9 µm to Cu2+ ions in a comparison with ZIF-8/rGO (224.28 mA.µM-1.cm-2) and ZIF-8 (102.9 mA.µM-1.cm-2) alone. Our results demonstrate the potential of ZIF-8/GO composites as a promising material for electrochemical sensing applications.

An Electrochemical o-Phthalaldehyde Sensor Using a Modified Disposable Screen-Printed Electrode with Polyacrylate Hydrogel for Concentration Verification of Clinical Disinfectant

The study proposes an o-phthalaldehyde (OPA) sensor for rapid and reliable detection of OPA in healthcare disinfection practices, based on a hydrogel-modified screen-printed carbon electrode strip. The hydrogel film, which contains glycine and N-acetylcysteine, reacts with OPA to produce a reductive isoindole derivative. The derivative is then oxidized for OPA determination using cyclic voltammetry. The proposed sensor achieves an optimal detection time of 20-30 s and requires only a small analyte volume of 5 µL. It exhibits good precision (10%) and sensitivity (3.3 μA/cm2 mM) in a phosphate-buffered solution (pH 7.6), with excellent linearity (R2 > 0.97) and precision (<3%) in the detection range (0.2-0.6%) required for clinical OPA solutions. Moreover, the sensor demonstrates good concentration verification of Cidex-OPA disinfection in healthcare institutes, with high sensitivity (18.28 μA/cm2 mM) and precision around the minimum effective concentration (0.3%). Overall, the proposed sensor offers a promising and practical solution for accurate and reliable OPA detection in clinical disinfection practices.