Carbon nanohorns/poly(glycine) modified glassy carbon electrode: Preparation, characterization and simultaneous electrochemical determination of uric acid, dopamine and ascorbic acid

Electrochemical sensor for effective detection of methyl parathion applying multidimensional MXene/CNHs/PPy nanocomposite to synergistically immobilize acetylcholinesterase

In this study, a novel acetylcholinesterase (AChE)-based electrochemical sensor was successfully constructed using two-dimensional MXene, carbon nanohorns (CNHs) and polypyrrole (PPy) as the substrate material for the detection of methyl parathion (MP) residue. The multidimensional MXene/CNHs composite, formed through electrostatic self-assembly, provided a high specific surface area and excellent conductivity. With an active surface area of 0.1062 cm2, the composite provided numerous electroactive sites for AChE immobilization and facilitated electron diffusion at the sensing interface, amplifying the electrochemical signals. Additionally, polypyrrole (PPy) improved AChE adhesion on the electrode surface, further enhancing the stability of the sensor. The proposed sensor exhibited a wide linear range (0.002-346 ng mL-1) and low detection limit (0.00021 ng mL-1) for MP. This study offers an innovative strategy to detect MP, showcasing the potential of two-dimensional materials in electrochemical sensing.

Electrochemically Grown Hole-Rich NiO(OH) Thin Films toward Hole-Mediated Very Fast and Selective Enzyme-Free Electrochemical Sensing of Dopamine under Simulated Environment

This work aimed to develop an enzyme-free semiconductor-assisted electrochemical technique for the selective detection of the neurotransmitter dopamine. In this case, electrochemically grown nickel oxyhydroxide [NiO(OH)] thin films were chosen to fabricate the sensing platform, i.e., the electrodes. Chronoamperometry was used to deposit the films on indium tin oxide (ITO) coated glass substrates. The films were thoroughly characterized to establish their structure, composition, phase purity, and electrochemical attributes. Electrochemical sensing characteristics were investigated by means of cyclic and differential pulse voltammetry, steady-state amperometry, and electrochemical impedance spectroscopy. The effects of several interfering agents like glucose, sodium chloride, methanol, hydrogen peroxide, and paracetamol were also studied on the detection attributes of dopamine. Significantly high value of sensitivity (11.87 μA μM-1 cm-2) was obtained for dopamine sensing that was associated with a limit of detection (LoD) of 0.22 μM of dopamine. However, the sensitivity (2.51 μA μM-1 cm-2) and LoD (1.20 μM) obtained for serotonin were inferior compared to those of dopamine. The performance of the electrode toward dopamine sensing was not compromised either in the presence of only serotonin or a series of other electroactive interfering agents, which makes the electrode very much dopamine selective. The dopamine response time was 200 ms, which is notably fast. Extensive studies on the effect of temperature, pH and scan rate on the detection of dopamine by the developed electrode material have also been carried out. The developed electrodes were also found to be notably stable for dopamine detection with a decay of only 6.6% in oxidation peak current density after the 50th cycle. Real-life application of the developed electrode material was checked with urine samples from adult male humans and yielded encouraging results.

Simultaneous Determination of Xanthine and Hypoxanthine Using Polyglycine/rGO-Modified Glassy Carbon Electrode

A novel electrochemical sensor was developed for selective and sensitive determination of xanthine (XT) and hypoxanthine (HX) based on polyglycine (p-Gly) and reduced graphene oxide (rGO) modified glassy carbon electrode (GCE). A mixed dispersion of 7 μL of 5 mM glycine and 1 mg/mL GO was dropped on GCE for the fabrication of p-Gly/rGO/GCE, followed by cyclic voltammetric sweeping in 0.1 M phosphate buffer solution within -0.45~1.85 V at a scanning rate of 100 mV·s^-1. The morphological and electrochemical features of p-Gly/rGO/GCE were investigated by scanning electron microscopy and cyclic voltammetry. Under optimal conditions, the linear relationship was acquired for the simultaneous determination of XT and HX in 1-100 μM. The preparation of the electrode was simple and efficient. Additionally, the sensor combined the excellent conductivity of rGO and the polymerization of Gly, demonstrating satisfying simultaneous sensing performance to both XT and HX.

Graphene and Carbon Nanotube-based Electrochemical Sensing Platforms for Dopamine

Dopamine (DA) is an important neurotransmitter, which is created and released from the central nervous system. It plays a crucial role in human activities, like cognition, emotions, and response to anything. Maladjustment of DA in human blood serum results in different neural diseases, like Parkinson's and Schizophrenia. Consequently, researchers have started working on DA detection in blood serum, which is undoubtedly a hot research area. Electrochemical sensing techniques are more promising to detect DA in real samples. However, utilizing conventional electrodes for selective determination of DA encounters numerous problems due to the coexistence of other materials, such as uric acid and ascorbic acid, which have an oxidation potential close to DA. To overcome such problems, researchers have put their focus on the modification of bare electrodes. The aim of this review is to present recent advances in modifications of most used bare electrodes with carbonaceous materials, especially graphene, its derivatives, and carbon nanotubes, for electrochemical detection of DA. A brief discussion about the mechanistic phenomena at the electrode interface has also been included in this review.

Gold Nanoparticles/Carbon Nanotubes and Gold Nanoporous as Novel Electrochemical Platforms for L-Ascorbic Acid Detection: Comparative Performance and Application

Herein, the effects of nanostructured modifications of a gold electrode surface in the development of electrochemical sensors for L-ascorbic acid detection have been investigated. In particular, a bare gold electrode has been modified by electrodeposition of gold single-walled carbon nanotubes (Au/SWCNTs) and by the formation of a highly nanoporous gold (h-nPG) film. The procedure has been realized by sweeping the potential between +0.8 V and 0 V vs. Ag/AgCl for 25 scans in a suspension containing 5 mg/mL of SWCNTs in 10 mM HAuCl4 and 2.5 M NH4Cl solution for Au/SWCNTs modified gold electrode. A similar procedure was applied for a h-nPG electrode in a 10 mM HAuCl4 solution containing 2.5 M NH4Cl, followed by applying a fixed potential of −4 V vs. Ag/AgCl for 60 s. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the properties of the modified electrodes. The developed sensors showed strong electrocatalytic activity towards ascorbic acid oxidation with enhanced sensitivities of 1.7 × 10−2 μA μM−1cm−2 and 2.5 × 10−2 μA μM−1cm−2 for Au/SWCNTs and h-nPG modified electrode, respectively, compared to bare gold electrode (1.0 × 10−2 μA μM−1cm−2). The detection limits were estimated to be 3.1 and 1.8 μM, respectively. The h-nPG electrode was successfully used to determine ascorbic acid in human urine with no significant interference and with satisfactory recovery levels.

An electrochemical method for determination of amaranth in drinks using functionalized graphene oxide/chitosan/ionic liquid nanocomposite supported nanoporous gold

An electrochemical sensor was fabricated by modifying nanoporous gold (NPG)-coated glassy carbon electrode (NPG/GCE) with functionalized graphene oxide /chitosan/ionic liquid nanocomposites (fGO/CS/IL). The introduction of ionic liquid (IL) and chitosan (CS) induced higher dispersibility of functionalized graphene oxide (fGO), and was beneficial for the combination of fGO/CS/IL with NPG/GCE. As a result of the synergistic effect of NPG and fGO/CS/IL, the resulted functionalized graphene oxide/chitosan/ionic liquid nanocomposites/nanoporous gold /glassy carbon electrode (fGO/CS/IL/NPG/GCE) showed the highest redox peak current response signal of Amaranth (E123) due to ultrahigh surface area, electronic conductivity as well as the improvement of the surface structure. Under optimized conditions, the enhanced peak currents represented excellent analytical performance for detection of Amaranth in the concentration range from 8.0 to 1200.0 nM. Meanwhile, the fGO/CS/IL/NPG/GCE presented satisfactory sensitivity and selectivity, excellent reproducibility, and long-time stability. For practical applications, the fGO/CS/IL/NPG/GCE was validated for the determination of Amaranth in three types of drinks with satisfactory results.

Experimental and theoretical study on the hydrogen bond interactions between ascorbic acid and glycine

Cyclic voltammetry, 1H nuclear magnetic resonance and quantum chemistry calculations were applied to explore the hydrogen bond interactions between ascorbic acid (AA) and glycine. The experimental results demonstrate the existence of hydrogen bonds in AA-glycine system, which has a significant effect on the oxidation peak potentials and currents of AA and the chemical shifts of glycine. The formation of hydrogen bonds between AA and glycine were further confirmed by the density functional theory, quantum theory of atoms in molecules and natural bond orbital analyses.

Structure, synthesis, and sensing applications of single-walled carbon nanohorns

Single-walled carbon nanohorns (SWCNHs), a type of tapered carbon nanomaterials, are generally prepared by laser ablation method, arc method, and Joule heating method without the addition of metal catalysts, which makes them pure and environmentally friendly. The obtained aggregates of SWCNHs mainly have three different types of structure, dahlia-like, bud-like, and seed-like. Over the past few decades, they have been widely used in the fields of energy, medicine, chemistry, and sensing. The SWCNHs-based sensors have shown high sensitivity, rapid response, and excellent stability, which are mainly attributed to the excellent electrical conductivity, large electrochemical window, large specific surface area, and mechanical strength of SWCNHs. In this review, we systematically summarizes the structures, synthesis methods, and sensing applications of SWCNHs, including electrochemical sensors, photoelectrochemical sensors, electrochemiluminescence sensors, fluorescent sensors, and resistive sensors. Moreover, the development prospects of SWCNHs in this field are also discussed.

Opening the internal structure for transport of ions: improvement of the structural and chemical properties of single-walled carbon nanohorns for supercapacitor electrodes

We investigated the electrochemical performance of single-walled carbon nanohorns (SWCNHs) for use as supercapacitor electrodes. For the first time, we used acid-treatment for oxidation of SWCNHs and hole creation in their structure. A detailed study was performed on the correlation between the oxidation of SWCNHs via acid treatment and variable acid treatment times, the structural properties of the oxidized carbon nanostructures, and the specific capacitance of the SWCNH electrodes. We showed that simple functionalization of carbon nanostructures under controlled conditions leads to an almost 3-fold increase in their specific capacitance (from 65 to 180 F g⁻¹ in 0.1 M H₂SO₄). This phenomenon indicates higher accessibility of the surface area of the electrodes by electrolyte ions as a result of gradual opening of the SWCNH internal channels.

The correlation between the oxidation of single-walled carbon nanohorns (SWCNHs) via acid treatment and the electrochemical properties of the SWCNH electrodes is presented.

Carbonaceous Nanomaterials Employed in the Development of Electrochemical Sensors Based on Screen-Printing Technique—A Review

This paper aims to revise research on carbonaceous nanomaterials used in developing sensors. In general, nanomaterials are known to be useful in developing high-performance sensors due to their unique physical and chemical properties. Thus, descriptions were made for various structural features, properties, and manner of functionalization of carbon-based nanomaterials used in electrochemical sensors. Of the commonly used technologies in manufacturing electrochemical sensors, the screen-printing technique was described, highlighting the advantages of this type of device. In addition, an analysis was performed in point of the various applications of carbon-based nanomaterial sensors to detect analytes of interest in different sample types.

In situ polymerization and FT-IR characterization of poly-glycine on pencil graphite electrode for sensitive determination of anti-emetic drug, granisetron in injections and human plasma

In situ polymerization is a simple and efficient technique for modification and fabrication of modified electrodes in voltammetry. An efficient and highly sensitive square wave voltammetric (SWV) method was developed for analysis of a 5-HT₃ antagonist granisetron (GRN) using in situ polymerized glycine on pencil graphite electrode surface. It was found that the fabricated polymer enhanced the sensitivity by more than two times and enhanced the surface activity by more than three times. Surface area measurements showed that poly-Gly/PGE have large surface area of 44.3 mm², when compared to that of bare PEG (12.1 mm²). Several methods as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques were used to characterize the modified surface. Further, FT-IR spectroscopic study was used to predict the way of glycine polymerization on electrode surface and the possible interaction mechanism with GRN. After optimization, the proposed method showed a linear response of GRN concentrations in the range from 0.08 to 3.00 μmol L⁻¹ with a limit of detection (LOD) of 26.2 nmol L⁻¹ (9.14 ng mL⁻¹). The method was utilized for GRN determination in ampoules and in real human plasma samples.

In situ polymerization is a simple and efficient technique for modification and fabrication of modified electrodes in voltammetry.

Poly(glycine)/graphene oxide modified glassy carbon electrode: Preparation, characterization and simultaneous electrochemical determination of dopamine, uric acid, guanine and adenine

A novel poly(glycine) (p-GLY)/graphene oxide (GO) composite based sensor (p-GLY/GO) was successfully prepared on glassy carbon electrode by simple electropolymerization. Electrochemical responses of analytes on p-GLY/GO modified electrode were studied by cyclic voltammetry and differential pulse voltammetry. The results demonstrated that p-GLY/GO modified electrode showed a favorable application for the simultaneous determination of dopamine (DA), uric acid (UA), guanine (GU) and adenine (AD). Owing to the synergistic effect of p-GLY and GO, the oxidation peaks of four analytes separated well from each other, and the potential separations of oxidation peaks of DA-UA, UA-GU and GU-AD were large up to 170, 350 and 300 mV, respectively. As-prepared p-GLY/GO modified electrode offered wide linear responses for DA, UA, GU and AD over the ranges of 0.20-62, 0.10-105, 0.15-48 and 0.090-103 μM with detection limits of 0.011, 0.061, 0.026 and 0.030 μM (S/N = 3), respectively. Moreover, p-GLY/GO modified electrode presented favorable selectivity, stability and reproducibility, which was a promising candidate as an electrochemical sensor for the simultaneous determination of DA, UA, GU and AD.

Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.

Fabrication of nitrogen-doped carbon dots for screening the purine metabolic disorder in human fluids

Fabrication of nitrogen-doped carbon dots (N-CDs) electrode for the screening of purine metabolic disorder was described in this paper. Peroxynitrite is a short-lived oxidant species that is a potent inducer of cell death. Uric acid (UA) can scavenge the peroxynitrite to avoid the formation of nitrotyrosine, which is formed from the reaction between peroxynitrite and tyrosine (Try). Scavenging the peroxynitrite avoids the inactivation of cellular enzymes and modification of the cytoskeleton. Reduced level of UA decreases the ability of the body from preventing the peroxynitrite toxicity. On the other hand, the abnormal level of UA leads to gout and hyperuricemia. Allopurinol (AP) is administered in UA lowering therapy. Thus, the simultaneous determination of UA, Try and AP using N-CDs modified glassy carbon (GC) electrode was demonstrated for the first time. Initially, N-CDs were prepared from L-asparagine by pyrolysis and characterized by different spectroscopic and microscopic techniques. The HR-TEM image shows that the average size of the prepared N-CDs was 1.8±0.03nm. Further, the N-CDs were directly attached on GC electrode by simple immersion, follows Micheal's nucleophilic addition. XPS of N-CDs shows a peak at 285.3eV corresponds to the formation of C-N bond. The GC/N-CDs electrode shows higher electrocatalytic activity towards UA, Tyr and AP by not only shifting their oxidation potentials toward less positive potential but also enhanced their oxidation currents in contrast to bare GC electrode. The GC/N-CDs electrode shows the limit of detection of 13×10^-10M (S/N=3) and the sensitivity of 924μAmM^-1cm^-2 towards the determination of UA. Finally, the N-CDs modified electrode was utilized for the determination of UA, Tyr and AP in human blood serum and urine samples.

Plasmonic and photo-electrochemical enhancements of the AuAg@Au/RGO–C3N4 nanocomposite for the detection of DA

Plasmonic photocatalyst has attracted significant attention due to its valuable theoretical study and promising practical applications in solar cells, functional composites, and sensors.

A glassy carbon electrode modified with γ-Ce2S3-decorated CNT nanocomposites for uric acid sensor development: a real sample analysis

γ-Ce₂S₃-decorated multi-walled carbon nanotube nanocomposite (Ce₂S₃-CNT NC) was synthesized by a wet chemical method in basic media.