Screen-printed Electrodes Research Articles

Electrochemical characterization of carbon black in different redox probes and their application in electrochemical sensing

Carbon black - materials rich in carbon nanostructures - have been successfully applied as modifiers of electrochemical transducers, rivalling other carbon nanomaterials for cost and ease-of-use. Despite the remarkable promise of this nanomaterial, no study has yet comparatively characterised a wide range of different grades of carbon black for their utility in electrochemical sensors. Here, we explore several commonly-studied carbon black grades (N220, N234, N326, N330, N339, N375, N550, N660 and Lamp Black-101), alongside relatively newer grades (Printex®-200, Printex® G, Printex® XE-2B, and Printex® Zeta) for their application in electrochemical sensors. The effects of coating glassy carbon electrodes with carbon black on electrode performance were studied by cyclic voltammetry using three redox probes: ferri-/ferrocyanide (anionic probe molecules), ferrocenemethanol (neutral) and hexaammineruthenium (cationic). Raman Spectroscopy characterisation of the different grades associated a lower degree of graphitisation with superior electrode modifiers. Generally, modification increased the anodic peak current for ferri-/ferrocyanide probes; and lowered anodic potential for ferri-/ferrocyanide and hexaammineruthenium probes. Increases in peak current and potential observed at ferrocenemethanol are consistent with the increased tendency for this probe to adsorb to the surface of modified electrodes. N330 and Printex® XE-2B displayed the best electrocatalytic properties in terms of enhanced peak currents and lowered anodic overpotentials for the redox probes. CB grades were used to modify screen-printed carbon electrodes and the obtained sensors examined for anodic detection of reduced nicotinamide adenine dinucleotide (NADH) cofactor by cyclic voltammetry. Printex® XE-2B significantly improved the detection of NADH and was further used for chronoamperometric detection of NADH at low overpotentials. Grades N220, N375, N550 and P-G showed their suitability as enzyme scaffolds for sensor fabrication, as determined by their preservation of the activity of a NAD-dependent aldehyde dehydrogenase.

Electrochemical sensor for glutathione reductase based on screen-printed electrodes coated with 3,5-dinitrobenzoic acid-modified carbon nanotubes.

The preparation of a hybrid nanomaterial is reportedby covalently attaching 3,5-dinitrobenzoic acid groups to the surface of oxidized multi-walled carbon nanotubes using 1,6-diaminohexane as cross-linking agent. This nanomaterial, modified with the redox mediator, was used as transduction element to construct an amperometric sensor for the efficient indirect determination of glutathione reductase at a low working potential of - 0.05V, through the oxidation of unconsumed nicotinamide adenine dinucleotide phosphate (NADPH) in the enzymatic reaction. The sensor exhibited an excellent linear response in the range 1.6 to 174 µU/µL, with high reproducibility and selectivity. The developed device was successfully validated in real samples, accurately determining the active enzyme in diluted human serum, making it a promising alternative for the determination of glutathione reductase and other related NADPH-dependent enzymes with relevance in clinical analysis.

Copper oxide–modified screen-printed carbon electrodes for the detection of mycobacterium tuberculosis infection treating drug: Isoniazid

Copper oxide–modified screen-printed carbon electrodes for the detection of mycobacterium tuberculosis infection treating drug: Isoniazid

Signal-Boosted Electrochemical Lateral Flow Immunoassay for Early Point-of-Care Detection of Liver Cancer Biomarker.

The early diagnosis of cancer in a point-of-need manner is of great significance, yet it remains challenging to achieve the necessary sensitivity and speed. Traditional lateral flow immunoassay (LFIA) methods are limited in accuracy and quantification, restricting their suitability for home-based applications. Thus, we explored a new and user-friendly electrochemical LFIA (e-LFIA) test strip to detect α-fetoprotein (AFP), a diagnostic marker for liver cancer. The specific electrochemical immunoprobe utilized in this e-LFIA test strip is characterized by significant signal boosting, resulted from the loading Ag shell into a gold nanoparticle (AuNP)-coated dendritic mesoporous silica nanoscaffold (DMSN). Leveraging the distinct electrochemical characteristics of Ag anodic stripping and the high volume-to-surface area ratio of DMSNs, the developed DMSNs/AuNPs@Ag-based e-LFIA test strip is capable of detecting AFP at a low concentration of 0.85 ng/mL within a rapid 20 min timespan, both of these values are smaller than those in current clinical testing. Furthermore, we utilized homemade screen-printed electrodes in this sensing prototype and demonstrated the high versatility and reliability of this e-LFIA device. We envision that this DMSNs/AuNPs@Ag-based e-LFIA holds substantial potential for the early diagnosis of liver cancer and household health monitoring.

Determination of silver ions in distilled water by stripping voltammetry at a Nafion-coated gold electrode in combination with quartz crystal microbalance and electrochemical impedance spectroscopy

Here, we propose a stripping voltammetric method for Ag+ ion determination in distilled water utilizing screen-printed Au electrodes coated with Nafion (Nafion/Au screen-printed electrodes). The concentration of Ag+ in pure water was determined by linear sweep voltammetry (LSV) after silver deposition on the Nafion/Au electrode. The anodic stripping peak current increased linearly with the concentration of Ag+ ion in the range from 1 ppm to 22 ppm. The LSV oxidative peak current was increased by extending the silver deposition time from 300 s to 500 s. Repetitive LSV measurements revealed satisfactory reproducibility of the Nafion/Au screen-printed electrodes. The detection mechanism was elucidated by recording mass changes of the Nafion/Au electrode with a quartz crystal microbalance (QCM), and by determining changes in the low-frequency capacitance of the Nafion/Au electrode by electrochemical impedance spectroscopy (EIS). The observed changes in mass and capacitance confirmed Ag+ accumulation and release processes at the Nafion/Au electrodes, in good agreement with stripping voltammetry. The combination of stripping voltammetry, QCM and EIS allowed a detailed characterization of the ion transfer, deposition and stripping processes at the Nafion/Au electrodes in presence of Ag+ ions. The Nafion/Au screen-printed electrode enabled voltammetric determination of low Ag+ concentrations in distilled water, without any sample pretreatment nor addition of supporting electrolyte.

Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM−1, and linear range of 180–2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

Developing dual detection platforms for the electrochemical quantification of homocysteine in biological samples

This study presents a novel dual electrochemical sensor developed using simple electropolymerization technique to detect and measure homocysteine (HC). The developed electrode modification was confirmed using FTIR, XRD, and SEM-EDX examinations. The poly(N-phenylanthranilic acid) modification of the glassy carbon electrode (GCE) and Screen-printed electrode (SPE) significantly enhanced the response for HC, surpassing the findings of previous studies. The improvement can be credited to the exceptional catalytic efficiency of the electro-polymer in electro-oxidizing HC. The electrochemical investigations were conducted utilizing analytical methods such as cyclic voltammetry and differential pulse voltammetry, with a 0.1 M phosphate buffer solution employed as the supporting medium. The poly-NPAA/GCE and poly-NPAA/SPE sensor has demonstrated exceptional sensing properties such as excellent selectivity, sensitivity, reproducibility and and repeatability. It is highly effective in identifying and quantifying HC. The exhibited linear range of both poly-NPAA/GCE and poly-NPAA/SPE are the widest, ranging from 1.0 to 2300.0 μM for poly-NPAA/GCE and from 3.0 to 3000.0 μM for poly-NPAA/SPE, making it the most remarkable result ever reported. The detection limit (LOD) of poly-NPAA/GCE was determined to be 0.165 µM while that of poly-NPAA/SPE was obtained as 0.618 µM. Furthermore, real-sample analysis was performed using biological fluids at the advanced sensor. Therefore, the fabricated poly-NPAA/GCE and poly-NPAA/SPE exhibited exceptional electrocatalytic capabilities for HC sensing, rendering it appropriate for continuous monitoring.

Voltammetric determination of uric acid using a miniaturized platform based on screen-printed electrodes modified with platinum nanoparticles

Disposable and sensitive screen-printed carbon electrodes (SPCE) modified with multi-walled carbon nanotubes (MWCNT) and platinum nanoparticles (PtNPs) were constructed to analyse uric acid (UA) in biological samples using a miniaturized smartphone potentiostat system. Combining the nanomaterials with Nafion® yielded a stable dispersion that could be successfully used as an electroactive layer. Transmission electron microscopy (TEM) and energy dispersive scanning (EDS) were used to characterize the morphology of PtNPs. These revealed approximately spherical shapes with emission lines characteristics of platinum. Furthermore, PtNPs/MWCNT/SPCE film was characterized by scanning electron microscopy (SEM), which demonstrated the tubular characteristic of MWCNT distributed and covered by carbon black (CB) spheres present in the screen-printed ink. An enhanced current response was observed for UA voltammetric analysis, especially due to the synergism effect of PtNPs and MWCNT, which reduced the Rct value. The values of Dapp (1.6 × 10−6 cm−2 s−1) and kcat (2.76 × 103 mol−1 L/s) were determined for UA using the proposed sensor. The sensor displayed linear response for UA in the range from 5.0 × 10−6 mol/L to 6.9 × 10−4 mol/L, with a detection limit of 4.9 × 10−7 mol/L. Along with detectability, excellent performances were verified in terms of repeatability, anti-interference features, and analysis of UA in the biological samples.

Design of an electrochemical hydrogel nanocomposite immunosensor for the detection of hemoglobin in blood

A novel hybrid hydrogel nanocomposite immunosensor was developed for the electrochemical detection of hemoglobin in blood. The transducing element was based on carbon black (CB)-nanomodified screen-printed electrodes (SPEs) on which a poly(ethylene glycol)-diacrylate hydrogel (PEGDA) doped with gold nanoparticles (AuNPs) was photopolymerized in situ. The fabricated PEGDA-AuNPs/CB-SPEs were then functionalized with oriented anti-hemoglobin antibodies. The immunosensor was analyzed by Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) at different modification steps, while its morphology was evaluated by Scanning Electron Microscopy (SEM). The analytical performances of the resulting PEGDA-AuNPs/CB-SPE immunosensor were assessed by DPV analysis, demonstrating the ability of the proposed system to detect hemoglobin in both standard solution and serum samples with a limit of detection (LOD) of 0.005 mg/mL within a dynamic response in a concentration range from 0.005 to 0.1 mg/mL. Slight interference was observed in the presence of glucose and ascorbic acid at concentrations much higher than those physiologically present in the blood. Moreover, any matrix effect was evidenced in serum samples, with a good recovery value of 107 ± 4 % obtained for a hemoglobin concentration of 0.025 mg/mL.

One-pot bioinspired synthesis of PbO/CuO/FeO trimetallic oxide nanocomposite using Vitis vinifera fruit juice for highly sensitive electrochemical detection of 4-Nitrotoluene

The determination of explosive nitroaromatic chemicals has prompted concerns about human safety around the world. In this work, we demonstrate an electrochemical sensor based on trimetallic oxide nanocomposites modified screen-printed carbon electrode (SPCE) for the detection of nitroaromatic compounds. Trimetallic oxide nanocomposites are multiphase materials containing ternary metal oxides. Because of their high specific surface area, superior electron transport capabilities, and favourable catalytic behaviour, they are frequently employed as antibacterial materials, catalysts, and sensors. In order to combat the problems associated with high manufacturing costs, low selectivity, and low sensitivity of conventional sensors, this paper reports on the construction of an electrochemical sensor for 4-nitrotoluene (4-NT) using a trimetallic oxide nano-sensor. The nano-sensor is composed of transition metal oxides copper and iron combined with post-transition lead metal oxide. In this study, we prepared a PbO/CuO/FeO TMO NCs sample with different individual metal oxides synthesized by a green reduction method using Vitis vinifera fruit juice. SEM was used to observe and validate structural and morphological variations brought on by various metal compositions. The four bio-synthesized materials comprise dispersed multiphase matrices containing varying shapes of nanoparticles with different morphologies. The elemental and phase arrangements of the synthesized samples were investigated employing UV, FT-IR, XRD, and EDAX approaches. The findings of the electrochemical measurements indicate that the SPCE modified with PbO/CuO/FeO TMO NCs has enhanced sensing capabilities over CuO, FeO, and PbO NPs for 4-NT; the limit of detection is 4.512 nM and sensitivity is −0.531 μA nM−1 for the developed sensor. Notably, recovery values (99.2–101.7 %) in water samples showed that evaluating interfering species from different contaminants had no effect on the sensing of 4-NT. All of these findings show that the newly developed sensor performs well in terms of reproducibility, selectivity, and sensitivity for the detection of 4-NT

Synthesis of Thioglycolic Acid-Modified Molybdenum Disulfide Nanosheets for Electrochemical Sensing and Its Application in Molnupiravir Detection

In the modern world, population growth, industrialization, and lifestyle changes have led to a rise in existing and new diseases, increasing global drug consumption. Proper pharmaceutical dosage is vital since drugs are only effective within specific concentration ranges. Therefore, developing reliable analytical methods for drug analysis in pharmaceuticals and biological samples is essential. Electroanalytical methods are particularly advantageous due to their low cost, ease of use, and rapid response. This study introduces a highly sensitive electrochemical sensor based on thioglycolic acid (TA)-decorated metallic phase molybdenum disulfide (MP-MoS2) nanosheets for the selective detection of molnupiravir (MOL), an antiviral drug used in Covid-19 treatment. The TA@MP-MoS2 nanomaterial was characterized using FTIR, TEM, and EIS. Screen-printed carbon electrodes (SPCE) were modified with TA@MP-MoS2 nanosheets to evaluate their electro-chemical and catalytic behaviours towards MOL by cyclic voltammetry (CV) and square wave voltammetry (SWV). The sensor displayed a well-defined electro-oxidation signal for MOL at 0.534 V, with the linear responses in two concentration ranges: 0.50–3.40 μM and 3.40–9.55 μM, and a low detection limit of 22.6 nM. The proposed design that has promising results could be an alternative strategy to fabricate the sensitive sensor for the detection of antiviral agents in real samples.

Layered double hydroxide nanozyme (LDHzyme)-assisted high-performance electrochemical analysis of organ transplant therapeutic drug concentration

The variability in mycophenolic acid (MPA) exposure levels among organ transplant patients is substantial and directly influences the drug’s therapeutic efficacy. Therefore, precise monitoring of MPA blood concentrations is imperative to devise personalized diagnostic and treatment plans tailored to individual patient profiles. In this study, we developed a screen-printed carbon electrode (SPCE) incorporating Layered Double Hydroxide-based nanozymes (LDHzymes) and multi-walled carbon nanotubes (MWCNT) to achieve high-sensitivity and stable determination of MPA in blood samples. We synthesized three distinct LDHzymes via a straightforward co-precipitation method, selecting CuMn-LDHzyme for its superior electrochemical properties and laccase activity in the context of MPA detection. The sensor’s performance was enhanced by the amalgamation of CuMn-LDHzyme with MWCNT, leveraging the laccase-like activity of CuMn-LDHzyme and the exceptional conductivity of MWCNT to amplify the oxidation current response to MPA. This integration significantly bolstered the sensor’s detection capabilities. The developed electrochemical sensor exhibited remarkable characteristics, including high selectivity, stability, repeatability, and reproducibility. It demonstrated a notable sensitivity with a detection range of 0.5 µM to 200 µM for MPA, and a detection limit of 0.1 µM, effectively detecting MPA in mouse blood samples. These attributes underscore the sensors as promising tool for clinical drug detection, ensuring fast and precise monitoring of MPA levels in organ transplant patients. This innovative approach holds significant promise for advancing personalized medical care and improving therapeutic outcomes.

Non-enzymatic cholesterol biosensor: Electrochemical sensing based on peptide-polylactic acid thin film

Cholesterol is a fundamental lipid prevalent in eukaryotic cell membranes and circulating in the bloodstream bound to lipoproteins. It serves as a precursor to steroid hormones and is regarded as a biomarker for cardiovascular disease and other metabolic disorders. Numerous cholesterol detection methods predominantly rely on enzymes, which suffer from instability, leading to non-cost-effective biosensors with low sensitivity and poor reusability. Therefore, monitoring cholesterol levels with a feasible, rapid, and stable biosensor is critical for diagnosing and treating various disorders. This study aimed to develop a non-enzymatic cholesterol biosensor based on a selected cholesterol recognition peptide as the detection element. Screen-printed carbon electrodes (SPEs) modified with biocompatible poly-L-lactic acid (PLLA) porous nanomembranes (NMs) were utilized as support for the covalent immobilization of the peptide. Data obtained from electrochemical impedance spectroscopy (EIS) demonstrated the peptide's effective binding affinity towards cholesterol, paving the way for its implementation. The determination of cholesterol with the proposed biosensor exhibited a low limit of detection of 6.31 μM with linear responses ranging from 2–15 μM and 20–40 μM. These findings present an alternative method for cholesterol sensing by integrating novel peptides as biorecognition motifs with biocompatible polymeric materials, potentially useful as biocompatible and future point-of-care sensors.

Voltammetric-based immunosensing of Newcastle disease virus on polyethylene glycol-containing self-assembled monolayer modified gold electrode

A voltammetric immunosensor for the detection of Newcastle disease virus (NDV) has been developed by employing polyclonal antibody targeting NDV (anti-NDV) as a bioreceptor. Anti-NDV was immobilized on polyethylene glycol (PEG)-containing self-assembled monolayer (SAM) which was activated with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (EDC) and N-hydroxy succinimide (NHS) coupling on screen-printed gold electrode (SPGE). The introduction of PEG-containing SAM on the SPGE allowed the bioreceptor to covalently bound to the electrode surface whilst still providing a hydrophilic layer on the electrode which is important to greatly reduce non-specific bindings. The bioreceptor functionalized electrode was then allowed to be incubated with NDV-spiked samples. The electrode surface modification with PEG-containing SAM, immobilization of anti-NDV as bioreceptor, up to the detection of NDV were characterized electrochemically through differential pulse voltammetry (DPV) analysis in [Fe(CN)6]3- as the redox probe. Decrement of anodic current peak (Ipa) of [Fe(CN)6]3- was seen as the concentration of NDV increased from 0.156 to 20 HA μL-1 with the limit of detection (LoD) of 1.50 HA μL-1 at 3σ m-1. The detection of NDV in HA μL-1 unit in this study would ease interlaboratory interpretation as it was the same unit used in hemagglutination (HA) assay of conventional NDV diagnosis. The specificity of anti-NDV used as bioreceptor towards NDV was confirmed through western blot analysis, whilst the selectivity of the bioreceptor-functionalized electrode has been tested with allantoic fluid as the negative control in which no apparent changes of anodic peak (Ipa) has been seen. This simple, fast, and less laborious electrochemical detection method could become an alternative to the conventional method for NDV detection.

Charged Microdroplets Deposition for Nanostructured-Based Electrode Surface Modification

Accelerated synthesis of gold nanoparticles (AuNPs) in charged microdroplets produced by electrospray ionization (ESI) was exploited to modify the surface of graphite screen-printed electrodes (GSPEs). The deposited AuNPs were then functionalized by the charged microdroplets deposition of 6-ferrocenyl-hexanethiol (6Fc-ht) solutions that act as reducing and stabilizing agents and provide electrochemical properties for the modified electrodes. The morphology and composition of the AuNPs were characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrodes. The results showed that the ESI microdroplets deposition technique produces uniform and well-dispersed AuNPs on GSPE, and optimal conditions for deposition were identified, enhancing GSPE electrocatalytic performance. Further functionalization by ESI microdroplets of AuNPs with 6Fc-ht demonstrated improved redox properties compared with the conventional self-assembled monolayer (SAM) method, highlighting the technique’s potential for the easy and fast functionalization of electrochemical sensors.

Label free electrochemical detection of 2-aminoindane

This study describes a label-free voltammetric detection of 2-aminoindane (2-AI), a novel psychoactive substance, using graphite screen-printed electrode modified with an electrochemically oxidized cobalt bis(dicarbollide) derivative (CoK/G/SPE). Morphological, structural and electrochemical characterization is assessed by using a computational approach, scanning electron microscopy, infrared spectrometry and electrochemical techniques. The binding/recognition of 2-AI (as a primary analyte) and 2,5-dimethoxy-4-iodoamphetamine (DOI, as interferent from category amphetamines) is compared, with CoK as a monomer as well as electrochemically deposited on the G/SPE surface. The mechanism of selectivity is proposed. The experimental findings show that these two stimulants compete for the binding/recognition sites on the modified electrode surface, with the adsorption constant values of (2.62 ± 0.67) x 105 and (6.10 ± 1.32) x 105, a linear range of 19.9 – 119 μmol L–1 and 9.97 – 235 μmol L–1, and the limit of detection 7.2 μmol L–1 and 2.37 μmol L–1 for 2-AI and DOI, respectively. An important point considering the analytical applicability and significance of CoK/G/SPE for forensic analysis is the possibility to distinguish 2-AI from an amphetamine derivative in a two-component mixture. The CoK/G/SPE electrodes are successfully applied to determine 19.9 μmol L–1 2-AI in spiked model samples with recovery values of 85.3–94.8 % and relative standard deviations 10–21 %. Such reproducibility is satisfactory considering the low cost of the electrode fabrication route.

Screen-printed Carbon Electrode from Coconut Shell Activated Carbon Modified with Ferrocene for Cobalt Detection

This research aims to fabricate a screen-printed carbon electrode (SPCE) from coconut shell charcoal. The charcoal was activated with NaOH to produce activated carbon (Ac). It was mixed with acetylene black (AB) and poly (vinylidene) Fluoride (PVDF) at the mass ratio of 7:2:1 for the Ac, AB, and PVDF, respectively, followed by a dispersing with N-Methyl-2-Pyrrolidinone (NMP) producing carbon slurry that was painted on a SPCE template. To increase electrochemical sensitivity, ferrocene, Fc was dropped onto the working electrode part at 10%, 20%, and 30% of the total SPCE mass. The results show that Ac is amorphous with a porous chip-like morphology containing 61.7% carbon. Ac shows vibrations of O–H, C=O, C=C, C–O, and Si–O with surface area and average pore size of 154.612 m<sup>2 </sup>g<sup>-1</sup> and 1.42 nm, respectively. The cyclic voltammetry analysis found that 10% Fc on SPCE provides the highest current density compared to 20% and 30%. Meanwhile, the 2 mV s<sup>-1</sup> scanning rate reveals a more defined anodic and cathodic peak than 3 mV s<sup>-1</sup> and 5 mV s<sup>‑1</sup>. Furthermore, the SPCE with 10% Fc shows a good sensitivity to Co (II) ions, proven by a low detection limit (LoD) of 0.224 mmol L<sup>-1</sup>

Covalently linked 4-Aminopyridine on reduced graphene oxide for high performance electrochemical supercapacitor electrode material

The portability of electrical devices requires the demanding but essential task of improving supercapacitor energy density while preserving stability. Introducing an amine heterocyclic compound on a reduced graphene oxide (rGO) layer can enhance its capacity for energy storage. Here, we employed Catharanthus roseus flower extract as a green reducing agent to prepare rGO for the first time. A stable covalently linked 4-AP-rGO was produced through combining of 4-Aminopyridine on the rGO layer via nucleophilic substitution reaction process. The synthesized materials were systematically characterized by FT-IR, UV–visible, Raman, powder XRD, XPS, SEM, and TEM. Furthermore, the screen-printed carbon electrode (SPCE) was modified with 4AP-rGO (4AP-rGO/SPCE) to evaluate the electrochemical properties using CV, GCD, and EIS in 1 M H2SO4. The electrochemical performance of the 4AP-rGO/SPCE modified electrode was compared with unfunctionalized rGO. The pseudocapacitive efficacy of the 4AP-rGO was exceptional as evidenced by its high energy density (12.27 × 10−4 Wh kg−1), high power density (350.6 × 10−3 W kg−1), and high specific capacitance of (180.3 × 10−3 F g−1) at 1 A g-1. Over 10,000 cycles at 1 A g-1, it maintained 98.8 % capacitance, exhibiting exceptional cycling stability. The energy density of 4-AP-rGO is 2.1 times higher than that of rGO, indicating that it is a suitable candidate for energy storage applications.

Electrochemical sensors for sensitive and selective detection of nitrite based on flexible gold microneedle like nanodendrites modified electrode

In this study, we present a new approach utilizing Au nanodendrites (Au NDs) to modify flexible screen-printed carbon electrodes (FSPCEs), offering an efficient platform for voltammetric sensing of nitrite ions in food samples. The FSPCEs are created with gold leaf-like nanodendrites through a simple, one-step electrochemical deposition process. The direct growth of these Au NDs occurs efficiently on the carbon-paste electrode, eliminating the need for binders or additional reducing agents and organic solvents, owing to the aforementioned matrix. The modified electrodes serve as promising sensing platforms for nitrite detection. The outcomes demonstrated that a significant amount of AuNPs with dendritic morphologies were dispersed throughout the FSPCE.These novel flexible electrodes act as effective electrocatalyst for NO2− oxidation due to their large electrochemical active surface area (ECSA), well-dispersed Au nanostructures, and high electrical conductivity. The optimized sensor exhibits a wide linear response range from 0.02 to 5.8 µM, with 1.0 nM limit of detection, an impressive sensitivity of 52.529 µA µM−1 cm−2 and a quick current response time (< 3 s) towards nitrite ions. Additionally, the suggested sensor demonstrates high selectivity, reproducibility, and stability. Furthermore, the FSPCEs are evaluated for their ability to selectively detect nitrite ions in various food samples such as tap water, drinking water, milk, and fruit juices, comparing the results with standard methods in real sample analysis. The fabricated sensors show promising potential for practical applications in food and environmental analysis. Consequently, Au NDs@FSPCE electrode emerged to be a novel platform for NO2− electrochemical detection. Because of their great affinity for analytical substances in solutions, gold nanodendrites supported on flexible screen-printed carbon electrodes (FSPCEs) are very useful for electrode modifications. Their increased effective surface area, which greatly raises the electrode's sensitivity and specificity for a range of analytical applications, is responsible for their high affinity.

Smartphone-based portable sensor with Bi-MOF nanocomposite for Cd (II) in vegetable samples

The accumulation of heavy metal cadmium (Cd) in the food chain poses a serious threat to human health, necessitating the development of rapid, on-site, and portable detection methods for Cd (II). Herein, we developed a smartphone-based electrochemical sensor for portable determination of Cd (II) in vegetables using a bismuth metal–organic framework (Bi-MOF) nanocomposite. Prismatic rod-like Bi-MOF was hydrothermally synthesized using trimesic acid as organic ligands, and subsequently, carboxyl-functionalized multi-walled carbon nanotubes (COOH-MWCNTs) were incorporated to form Bi-MOF nanocomposite network. The smartphone-based electrochemical sensor enables rapid, sensitive, and portable detection of Cd (II) in vegetable samples using Bi-MOF/COOH-MWCNTs-modified screen-printed carbon electrodes (SPCE). A comparative analysis of traditional electrochemical sensors coupled with desktop computer for linear voltametric responses for Cd (II) in the range of 0.2–500 ng/mL with a limit of detection (LOD) of 0.07 ng/mL using Bi-MOF/COOH-MWCNTs-modified glassy carbon electrodes (GCE), the portable sensor demonstrated good linear range in 0.7–350 ng/mL with a LOD of 0.22 ng/mL. This work introduces a novel approach for on-site and portable detection of Cd (II) in agricultural products.