Voltammetric Sensor Research Articles

Smart E-Tongue Based on Polypyrrole Sensor Array as Tool for Rapid Analysis of Coffees from Different Varieties

Due to the lucrative coffee market, this product is often subject to adulteration, as inferior or non-coffee materials or varieties are mixed in, negatively affecting its quality. Traditional sensory evaluations by expert tasters and chemical analysis methods, although effective, are time-consuming, costly, and require skilled personnel. The aim of this work was to evaluate the capacity of a smart electronic tongue (e-tongue) based on a polypyrrole sensor array as a tool for the rapid analysis of coffees elaborated from beans of different varieties. The smart e-tongue device was developed with a polypyrrole-based voltammetric sensor array and portable multi-potentiostat operated via smartphone. The sensor array comprised seven electrodes, each doped with distinct counterions to enhance cross-selectivity. The smart e-tongue was tested on five Arabica coffee varieties (Typica, Bourbon, Maragogype, Tabi, and Caturra). The resulting voltammetric signals were analyzed using principal component analysis assisted by neural networks (PCNN) and cluster analysis (CA), enabling clear discrimination among the coffee samples. The results demonstrate that the polypyrrole sensors can generate distinct electrochemical patterns, serving as “fingerprints” for each coffee variety. This study highlights the potential of polypyrrole-based smart e-tongues as a rapid, cost-effective, and portable alternative for coffee quality assessment and adulteration detection, with broader applications in the food and beverage industry.

Utility of Gold/Multiwalled Carbon Nanocomposite for Electrochemical Determination of Omarigliptin in Tablets and Human Plasma

Abstract An innovative voltammetric sensor was developed to estimate omarigliptin, a novel long-acting anti-diabetic drug. The sensor utilized a carbon paste electrode enhanced with a nanocomposite of carbon nanotubes and electrodeposited gold nanoparticles. The modified electrode was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The modification significantly improved the electrode's sensitivity and electrochemical efficiency and decreased its electron transfer resistance. The surface area of the modified electrode increased by about 2.8-fold compared to the bare electrode. Omarigliptin's oxidation behavior on the modified electrode was pH-dependent and irreversible, resulting in a peak current 4 times higher than the unmodified electrode. The modified electrode revealed good reproducibility, reusability, and stability. It allows for sensitive voltammetric analysis of omarigliptin over a linear range of 0.4–27 µM (LOD=0.12 µM) and good applicability in tablets and plasma. The recovery percentages are 98.47–101.27% in tablets and 95.86–105.02% in plasma. The modified electrode exhibits good selectivity towards OMR without interference from tablet excipients, endogenous plasma components, and co-administered drugs. The comparison with the reported methods reveals the superiority of the proposed method in terms of sensitivity, selectivity, applicability, and eco-friendliness. Finally, the proposed method demonstrates excellent environmental profiles based on recent assessment metrics.

Producing Activated Biochar from the Reuse of Discarded Coffee Grounds with Enhanced Adsorptive Features Explored Towards the Stripping Voltammetric Sensing of Copper (II)

AbstractThis work aims to allocate coffee grounds waste to the production of biochar from pyrolysis under different temperatures (350 °C and 500 °C), to add value to it. The resulting materials were characterized by immediate, elemental, thermogravimetric analysis, SEM, FT‐IR, XRD and Raman spectroscopy. Additionally, the need to activate the biochar produced for the desired use was evaluated. The obtained biochars were applied in electroanalysis in the manufacture of modified carbon paste electrodes. This choice was made due to the possibility of reaching a high sensitivity towards the determination of Cu2+ ions. The differential pulse adsorptive anodic stripping voltammetry technique was applied to perform the Cu2+ determination and, in this case, several parameters were optimized, including biochar’ percentage, pH of pre‐accumulation step and reduction/stripping step, pre‐accumulation time, potential and time of reduction of adsorbed‐Cu2+. From this, the proposed modified electrode showed a linear voltammetric response towards Cu2+ in the range of 66.1 to 3997.3 ppb, with a limit of detection of 31.8 ppb, in addition to having been satisfactorily applied in the analysis of water samples (recoveries close to 100 %). Thus, demonstrating the potential for reuse of discarded coffee grounds for the preparation of activated biochar with outstanding electrochemical performance.

Molecular imprinting sensor based on zeolitic imidazolate framework derived Co, N-doped carbon loaded on reduced graphene oxide toward the determination of dopamine.

Anovel voltammetric sensor designed for dopamine(DA) detectionis presented utilizing a combination of zeolitic imidazolate framework (ZIF-67) derived cobalt and nitrogen-doped carbon on reduced graphene oxide (Co-N-C/rGO). ZIF-67 cubic crystals were synthesized in situ and deposited onto the graphene oxide (GO) surface through room-temperature reactions. High-temperature calcination resulted in partially collapsed cubic and spherical carbon, while simultaneously reducing GO to rGO. A molecular imprinting resorcinol polymer (MIP) membrane was also in situ applied to the Co-N-C/rGO/glassy carbon electrode (GCE) via electropolymerization. Analyses using cyclic voltammetry, electrochemical impedance, and pulse voltammetry reveal that the modified MIP/Co-N-C/rGO/GCE electrodes show improved electroconductivity and notable electrochemical reactivity towards dopamine. After optimizing detection parameters, the sensor demonstrates a wide linear detection range of 0.01-0.5 and 0.5-100μmol/L, with a limit of detection (LOD) of 3.33nmol/L (S/N = 3). Additionally, the sensor displays strong robustness, including excellent selectivity, significant resistance to interference, and long-term stability. It also shows satisfactory recovery in detecting spiked real samples.

PolyCitrulline Modified Glassy Carbon Electrode as a Voltammetric Sensor for the Simultaneous Determination of Metabolic Syndrome Biomarkers-Uric Acid and Tyramine

Abstract This article describes the development of a simple and sensitive voltammetric sensor for the simultaneous determination of Uric acid (UA) and Tyramine (TYM), which act as metabolic syndrome (Mts) biomarkers. The electropolymer of the naturally occurring amino acid citrulline (Cit) has been employed as the electrode modifier in this sensor. Glassy carbon electrode modified with poly citrulline has been characterized with the aid of techniques such as scanning electron microscopy (SEM) and SEM-energy dispersive X-ray analysis, surface area calculations and electrochemical impedance spectroscopy. Studies were carried out to optimize parameters like the cycles of polymerisation, supporting electrolyte and its pH. The sensor which offers fast determination of the analytes using square wave voltammetry possesses a limit of detection 1.32×10-8 M and 4.20×10-8 M for UA and TYM, respectively. The applicability of the sensor in body fluids has been proved through spike recovery analysis in artificial blood serum and urine samples. Interference on the voltammetric signals created by some dominant coexisting species of the analytes was found to be tolerable.

Voltammetric and electro-kinetic assessment of prucalopride at MnO2-rGO fabricated pencil graphite electrode

Development and design of rGO-based nanocomposite-modified carbon-based electrodes are necessary to enhance the selectivity and desired selectivity of the voltammetric sensors. In this work, a manganese dioxide-reduced graphene oxide (MnO2-rGO) fabricated pencil graphite electrode is described for the detection of prucalopride (PRU), which is used to treat chronic idiopathic constipation. A simple cost effective hydrothermal method was used to synthesize the needle-shaped MnO2. The MnO2-rGO nanocomposite was characterized using XRD, SEM, and FTIR spectroscopy to examine its microstructure and morphology. The results revealed that MnO2 needles are distributed on the flakes of the rGO, thereby enhancing the electro-catalytic activity of MnO2-rGO/PGE. The electrochemical performance of the developed MnO2-rGO/PGE was examined using CV, chronocoulometry, SWSV, and DPSV methods. The diffusion-controlled oxidation of the PRU at the MnO2-rGO/PGE produces an irreversible peak in all the voltammograms which were used to calculate several electro-kinetic parameters like electron transfer coefficient (α = 0.598), diffusion coefficient (Do = 1.62 × 10−5 cm2s−1), surface coverage (Γo = 1.55 × 10−9 molcm−2), and effective surface area. Furthermore, advanced SWSV and DPSV methods are proposed for the accurate, selective, and sensitive detection of the PRU in pharmaceutical samples. The reported values of detection limit (LOD) for the proposed SWSV and DPSV methods are 20.39 μM and 14.53 μM, respectively, which make them eco-friendly and affordable alternative tools for the quantification of the PRU in pharmaceutical samples.

Proton conductive 2D MXene-derived potassium titanate nanoribbons fabricated electrochemical platform for trace detection of enrofloxacin

In recent years, due to exceptional properties like broad interlayered spacing and low working potential, MXene-derived titanate nanoribbons have been established as promising electrode materials. Herein, the electrocatalytic activity of MXene-derived potassium titanate nanoribbon was employed to develop a voltammetric sensor for the detection of enrofloxacin. The sensor's significance is to provide a sustainable solution to quantify the presence of enrofloxacin regarding food safety and environmental monitoring. Moreover, to achieve the United Nations' Sustainable Development Goals by preventing antimicrobial resistance to accomplish the One Health approach. Potassium titanate nanoribbons were synthesized using 2D Ti3C2 MXene as an active precursor material, while X-ray diffraction spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction pattern, elemental mapping, and energy-dispersive X-ray spectroscopy were used to characterize the crystallinity, surface and layered morphology of synthesized nanoribbons. The Brunauer-Emmett-Teller (BET) technique was applied to calculate the specific surface area of the synthesized materials. The materials underwent electrochemical characterization using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Later on, the nanoribbons were fabricated on the surface of a glassy carbon electrode, and the electro-oxidative behaviour of enrofloxacin was studied by CV, DPV, square wave voltammetry (SWV) in 0.1 M phosphate buffer (optimized pH 8). The developed sensor depicts a significantly lower limit of quantification of 0.007 μM (≈2.5 μg/L), and an upper limit of quantification of 18 μM (≈6.5 mg/L) along with a limit of detection (LOD) of 0.00279, 0.00803, 0.00881 μM obtained from CV, DPV, and SWV respectively. Furthermore, the developed electrodes show a reliable selectivity to be examined in real complex matrices, i.e. marine water, river water, agricultural soil, organic fertilizer, milk, honey, and poultry egg.

Novel and simple electrochemical sensing platform based on polypyrrole nanotubes/ZIF-67 nanocomposite/screen printed graphite electrode for sensitive determination of metronidazole

Here, a simple, fast, and sensitive voltammetric sensor based on screen printed graphite electrode (SPGE) modified with polypyrrole nanotubes/zeolitic imidazolate framework-67 (PPy NTs/ZIF-67) nanocomposite is introduced for the metronidazole (MNZ) determination. The PPy NTs/ZIF-67 nanocomposite was synthesized and characterized by using X-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The developed sensor based on PPy NTs-ZIF-67 nanocomposite modified SPGE shows an obvious reduction peak at −650 mV for MNZ, mainly due to the synergistic effects of the ZIF-67 and PPy NTs. Differential pulse voltammetry (DPV) was found to be the most suitable method for MNZ detection, showing a linear dynamic range of 0.01 to 500.0 µM and a low limit of detection (LOD) of 0.004 µM. In investigating the practicability, the PPy NTs/ZIF-67/SPGE sensor demonstrated efficient practicability with satisfactory recoveries (97.1 % to 103.5 %) and low relative standard deviation (RSD) values of 1.8–3.6 % for MNZ determination in MNZ tablets and urine samples.

A voltammetric sensor based on CuCo2O4 nanorods and ionic liquid for determination of sunset yellow

In this study, we report the electrochemical detection of sunset yellow (SY) at the surface of a carbon paste electrode (CPE) modified with CuCo2O4 nanorods (NRs) and an ionic liquid (IL). The electrochemical behavior of sunset yellow at the modified electrode was investigated using linear sweep voltammetry, differential pulse voltammetry and chrono­amperometry techniques. The CuCo2O4 NRs/IL/CPE sensor exhibited good performance and favorable electrochemical response for the electrochemical reaction of SY in a 0.1 M phosphate buffer solution at pH 7.0. The results showed a linear electrochemical response to SY within the concentration range of 0.2 to 160.0 μM, with a detection limit of 0.06 μM. In addition, The CuCo2O4 NRs/IL/CPE sensor demonstrated good ability for SY determination in real samples.

Voltammetric sensor for indole-3-lactic acid determination featuring N-doped core-shell Ir@Mo@Ni aerogels on screen printed carbon electrode

The excessive consumption of liquor accounts for 5.3% annual death and indole-3-lactic acid has been identified as a possible biomarker for mentally disorder patients arising from alcohol abuse. A highly sensitive and selective voltammetric sensing platform is proposed composed of N-doped core-shell Ir@Mo@Ni aerogel prepared via a facile in situ spontaneous gelation route using one-step NaBH4 reduction technique anchored on a cost-effective screen-printed carbon electrode (SPCE) for determination of indole-3-lactic acid (ILA) levels in buffer and serum. Prior to the analytical phase, the composite (N-Ir@Mo@Ni/SPCE) was thoroughly characterized, and different methods were used to investigate the electrochemical properties. The combination of tri-metallics resulted in improved sensing capacities in the linear range from 0.01–20µM, with sensitivity and limits of detection of 0.162 μA/μM and 7.2nM, respectively, towards ILA determination. Furthermore, the developed sensing platform was utilized for the analyses of ILA in human normal and alcohol use disorder patients’ serum samples. Liquid chromatography in tandem with mass spectrometry was equally used to quantify ILA levels in the serum samples and the results of both methods were compared.

Voltammetric Sensor Based on Titania Nanoparticles Synthesized with Aloe vera Extract for the Quantification of Dithiophosphates in Industrial and Environmental Samples

In this work, TiO2 spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change in the presence of nanoparticles; however, the surface chemical composition does. The voltammetric response to dicresyl dithiophosphate was higher when the electrode was modified with TiO2 nanoparticles. After an electrochemical response study from pH 1.0 to 12.0, pH 7.0 was selected for the electroanalysis. The electroactive area of the modified sensor was 0.036 cm2, while it was 0.026 cm2 for the bare electrode. The oxidation process showed mixed adsorption-diffusion control. The charge transfer resistance of the modified sensor (530.1 Ω, SD = 4.08 Ω) was much lower than that of the bare electrode (4298 Ω, SD = 8.53 Ω). The linear quantitative range by square wave voltammetry was from 5 to 150 μmol/L, with a limit of detection of 1.89 μmol/L and a limit of quantification of 6.26 μmol/L under optimal pulse parameters of 50 Hz frequency, 1 mV step potential, and 25 mV pulse amplitude. The sensor response was repeatable and reproducible over 30 days. The results on real flotation and synthetically contaminated soil samples were statistically equivalent to those obtained by UV-vis spectrophotometry. A dithiocarbamate showed an interfering effect on the sensor response to dithiophosphate.

The development of a disposable voltammetric sensor based on two-dimensional leaf-like ZIF-L (Zn) modified screen-printed graphite electrode for the simultaneous analysis of uric acid, dopamine and theophylline

The two-dimensional (2D) leaf-like zeolitic imidazolate framework-L (Zn) (ZIF-L (Zn)) was synthesized using a simple method in this study. The ZIF-L (Zn) was characterized using various techniques, such as FE-SEM, XRD, FT-IR, elemental mapping and EDX. The ZIF-L (Zn) was utilized to modify the surface of screen-printed graphite electrode (ZIF-L (Zn)/SPGE) to detect uric acid (UA). The sensor exhibited electrocatalytic behavior for uric acid in phosphate buffer solutions (PBS, 0.1 M), with a linear dependence between the current response and uric acid concentration in the dynamic range from 0.1 μM to 900.0 μM, a low limit of detection (LOD) of 0.04 μM, and good sensitivity of 0.0393 μA/μM under optimized experimental conditions. The ZIF-L (Zn)/SPGE sensor was successfully applied for uric acid determination in the presence of dopamine (DA) and theophylline (Thp) without any interference. The proposed electrode exhibits well-separated oxidation peaks at potentials of 139, 260 and 900 mV for dopamine, uric acid, and theophylline, respectively. In addition, the practical application of the fabricated sensor was demonstrated by detecting dopamine, uric acid, and theophylline in real samples.

Determination of methotrexate using carbon paste electrode modified with ionic liquid/Ni-Co layered double hydroxide nanosheets as a voltammetric sensor.

Methotrexate (MTX) is a widely used anti-cancer drug, but its overuse can lead to significant side effects. Therefore, it is very vital to design simple and sensitive analytical methods for its determination. In this work, an electrochemical sensor was prepared based on an ionic liquid (IL)/Ni-Co layered double hydroxide nanosheets (Ni-Co-LDH)-modified carbon paste electrode IL/Ni-Co-LDH/CPE. Cyclic voltammetry, differential pulse voltammetry, and chronoamperometry methods were applied to evaluate the performance of the designed sensor for MTX determination. The IL/Ni-Co-LDH/CPE sensor exhibits a linear relationship between the peak current of the differential pulse voltammetry and MTX concentrations in the linear dynamic range of 0.02 to 140.0 μM, with a detection limit of 0.006 μM. The IL/Ni-Co-LDH/CPE sensor exhibited relative standard deviation values between 1.7 to 3.7 % for recovery tests on real samples, indicating the precision of the method. The designed sensor with cost-effective and good performance could be valuable for therapeutic drug monitoring and clinical diagnostics.

Phenylalanine: Amino Acid Metal Non-Enzymatic Electrochemical Voltammetric Sensors

This study presents a comparative analysis of non-enzymatic electrochemical voltammetric sensors, utilizing phenylalanine amino acid metal complexes (M: Ni, Zn, and Co) Polyaniline (PANI) nanocomposites (NCs). The PANI: Zn(Phala)2 NCs-based sensor detected dopamine (DA) with a sensitivity of 101.18 μAμM−1 cm−2. The limit of detection (LOD) for the PANI: Zn(Phala)2 NCs-based sensor was calculated as 0.391 μM. This exceptional sensitivity makes the PANI: Zn(Phala)2 NCs-based sensor highly promising for potential integration into biomedical test kits. To gain deeper insights into the structural properties of the PANI NCs, scanning electron microscopy (SEM), artificial-intelligence-based SEM, and Fourier transform infrared spectroscopy (FTIR) were employed for characterization. FTIR characterization provided insights into the functional groups of the NCs. The results of this comparative investigation a significant advancement in the field of PANI-based electrochemical sensors designed for DA sensing. The PANI: Zn(Phala)2 NCs-based sensor show great promise for a range of advanced sensing applications. The Z value of the PANI: Zn(Phala)2 NCs-based sensor is the lowest among the tested materials, indicating that the conductivity of the PANI: Zn(Phala)2 layer is higher than that of other active layers. Consequently, the PANI: Zn(Phala)2 NCs-based sensor achieved higher sensitivity in DA detection.

Resolution of Glycerol, Ethanol and Methanol Employing a Voltammetric Electronic Tongue

This paper reports the use of nanoparticles (NPs)-modified voltammetric sensors for the rapid determination of glycerol in the presence of ethanol and methanol, which are used in the transesterification reaction of biodiesel production. Two different modified electrodes have been prepared to form the electronic tongue (ET): copper hexacyanoferrate NPs obtained by chemical synthesis and mixed into graphite/epoxy (GEC) electrode, and nickel hydroxide NPs electrodeposited in reduced graphene oxide onto a GEC electrode. The response characteristics of these electrodes were first evaluated by building the respective calibration against glycerol, ethanol, and methanol. The electrodes demonstrated good stability during their analytical characterization, while principal component analysis confirmed the differentiated response against the different alcohols. Finally, the quantification of mixtures of these substances was achieved by a genetic algorithm-artificial neural networks (GA-ANNs) model, showing satisfactory agreement between expected and obtained values.

Ruthenium-based microstructures modified by gold particles as composite electrode material for non-enzymatic epinephrine detection

A simple and efficient technique for voltammetric enzymeless detection of epinephrine (EP) was proposed. In this technique, we applied hierarchical Ru-based electrode modified by Au nano- to micro-sized particles that was fabricated using laser-assisted synthesis. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to characterize electrochemical properties of the fabricated electrode material. For EP detection, we obtained two DPV calibration curves that were linear in the range of 0.05–5 μM and 5–500 μM. The highest sensitivity (45.0 μA μM−1 cm−2) and the lowest detection limit (6.4 nM) were observed for the first linear range, whereas the estimated sensitivity and limit of detection for the second linear range were 2.0 μA μM−1 cm−2 and 18.7 nM, respectively. We also demonstrated that the proposed technique can be used for selective EP determination in the presence of such common interfering analytes as ascorbic acid and dopamine. The results of this study can be potentially used for development of low-cost voltammetric sensor platforms for non-enzymatic epinephrine detection.

Electrochemical Determination of Carbofuran Residues using WS2 Modified Electrodes

AbstractTo meet the increasing demands for food production, the utilization of cost‐effective pesticides like carbofuran (CB) becomes essential. CB poses a significant risk to human health due to its high toxicity. Therefore, accurate quantification of CB residue is essential for environmental safety and human health. Electrochemical sensors have proven to be an outstanding choice for the accurate detection and quantification of carbofuran residues. CB is electrochemically inactive and was first hydrolyzed in an alkaline medium to yield an anodically active phenolic derivative carbofuran phenol (CP). This report details the development of a voltammetric sensor for the accurate detection of CB residues utilizing the cyclic voltammetry technique and the electrochemical reactions of CP at WS2 nanosheet‐modified electrodes in phosphate buffer solution (PBS). The constructed sensor has displayed a linear range of carbofuran detection from 10–90 μM, with a limit of detection (LOD) of 0.38 μM and sensitivity of 0.303 μA μM−1 cm−2. Additionally, the developed sensor has been employed to monitor CB residues in real soil and water samples and it shows a recovery greater than 95 %. The developed sensor enables the cost‐effective monitoring of carbofuran in real samples.

Highly sensitive MXene-based voltammetric sensor for nanomolar clozapine detection

Clozapine is vital for managing schizophrenia and other psychiatric disorders. As a potent medication with risks of severe side effects, accurate detection ensures effective treatment monitoring, patient safety, and optimization of therapeutic outcomes. Herein, niobium carbide two-dimensional transition metal carbides (Nb2CTx MXene) was prepared by etching niobium aluminum carbide (Nb2AlC), which was next partially oxidized by a hydrothermal method to niobium oxide (Nb2O5)/Nb2CTx and ultrasonically bound to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH). It was modified onto a glassy carbon electrode for the detection of the antipsychotic drug clozapine ingested by humans. The morphology and electrochemical properties of MXene-based nanocomposite electrode were verified by scanning electron microscopy, X-ray diffractometry, Raman, cyclic voltammetry and electrochemical impedance characterization methods. The results showed that electrode responded well to clozapine solutions, with good linearity (R2 = 0.9979 and 0.9995) of the peak currents with clozapine concentrations (0.01–1.0 μM and 1.0–10.0 μM) and that this sensor had good immunity, repeatability, reproducibility and stability. The limit of detection was 8.38 nM and the recovery was 92.5 % ~ 106.5 % in real serum and urine samples. The MXene-based sensors offer excellent analytical performance and hold promise for cost-effective generalisation to the detection of nanomolar clozapine in a variety of clinical applications.

SWCNT fibers decorated with Au nanoparticles as voltammetric sensors for arsenic (III) determination

We developed a new method to produce fiber electrodes from single-walled carbon nanotube (SWCNT) films, which can be employed as a novel sensing platform for electrochemical investigations and analysis. By assembling SWCNT bundles in the form of a strong free-standing fiber with almost entire surface accessible to an analyte, we are able to avoid the interference of substrate and improve detection efficiency. We examined the influence of physical, chemical and electrochemical pretreatments of the new electrode SWCNT material on its properties. Transmission and scanning electron microscopy, Raman spectroscopy and cyclic voltammetry were used to characterize the SWCNT fibers. The modification of the SWCNT fiber electrode with gold nanoparticles provides the necessary analytical characteristics including high repeatability and sensitivity and low detection limit (1.3 – 2.1 μg L-1) for arsenic determination by anodic stripping voltammetry. Arsenic detection parameters such as deposition potential, deposition time and scan rate were optimized. Linear responses were found in concentration ranges from 3 to 210 μg L-1 and 7 to 125 μg L-1 for gold modified SWCNT fiber sensors (the SWCNTs were synthesized using CO or ethanol as precursors) at a relatively low deposition time of 60 s. The developed Au-SWCNT sensors allow rapid As determination in real samples and exhibit high durability and long service life.

Design and optimization of an electrochemical sensor based on carbon nanotubes for the reliable voltammetric detection of serotonin in complex biological fluids

Serotonin concentration in peripherical biological fluids is correlated with the insurgence of several pathologies and represents valuable information on the human physical and mental state of health. Rapid, portable, and reliable electrochemical sensors can mine this useful information in real-time and in situ. However, the main challenge that hampers their implementation is the poor operational stability in biological fluids rich in bio-macromolecules, which can induce the fouling of the electrode altering or invalidating the analytical performance of the sensor. Herein, we propose the design of a reliable and robust voltammetric sensor for detecting serotonin in plasma. The sensor is based on multiwall carbon nanotubes modified with ligand-free gold nanoparticles obtained by metal vapor synthesis, which can efficiently catalyze the oxidation of serotonin. A thin layer of molecular imprinted polymer is added to provide selectivity and antifouling properties to the sensor. By applying a design of the experiment, to optimize the experimental condition of the differential pulsed voltammetry, and adsorptive stripping to selectively pre-accumulate serotonin in the artificial receptor, we achieved serotonin detection in plasma with sensitivity (6.7 μA μmol L−1 cm−2) and limits of detection (1.0 μmol L−1) comparable to those registered in phosphate buffer solution.