Search

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered. [ABSTRACT FROM AUTHOR]

This work reports the construction of screen‐printed electrode (SPE) modified with carbon black (CB) and magnetic Fe3O4 nanoparticles coated with molecularly imprinted polymer (mag@MIP) based on an alternative low‐cost approach. The proposed device was used for the sensitive and selective voltammetric determination of the antibiotic ciprofloxacin. The results obtained from cyclic voltammetry pointed to the improvement of the SPE response toward the irreversible oxidation of ciprofloxacin after the modification of the electrode surface with CB‐based film and the magnetic preconcentration of mag@MIP containing adsorbed ciprofloxacin molecules. Compared to the non‐molecularly imprinted sensor (mag@NIP), the presence of cavities selective for ciprofloxacin recognition in the mag@MIP nanoparticles accounted for the improvement in analytical signal of the molecularly imprinted sensor. The application of differential pulse voltammetry for ciprofloxacin determination yielded a linear response in the concentration range of 0.5 to 7.0 μmol L−1. The repeatability and interference tests results showed that the proposed electrochemical sensor has good measurement accuracy and selectivity. The proposed device was applied for the voltammetric determination of ciprofloxacin in river water and synthetic urine samples, where recovery rates close to 100 % were recorded for all the samples. The quantification data obtained from the application of the proposed voltammetric method were quite consistent with those of the HPLC reference method. [ABSTRACT FROM AUTHOR]

A novel electrochemical method for determination of losartan using a glassy carbon electrode modified with carbon black nanoparticles immobilized within a crosslinked chitosan film is proposed. The electrochemical behavior of losartan was investigated using cyclic voltammetry, which presented an irreversible oxidation peak at a potential of + 1.28 V vs. Ag/AgCl (3.0 mol L−1 KCl). The electroactivity of losartan on the modified electrode was significantly improved in terms of peak potential and peak current intensity comparatively to bare working electrode. Using square-wave voltammetry technique under optimized conditions, the modified electrode showed a linear response in the concentration range of 4.97 to 47.6 μmol L−1 with a limit of detection of 0.479 μmol L−1. The developed electrochemical method was successfully applied for the determination of losartan in pharmaceutical formulation samples, with results consistent with those obtained by a comparative UV-Vis spectrophotometric method at 95% confidence level. In addition, losartan quantification was also achieved at synthetic biological fluid samples. [ABSTRACT FROM AUTHOR]

New aspects related to electrochemical performance of modified carbon paste electrodes (CPE) of high analytical performance are presented in this work. We studied whether the functionalisation of graphite powder with oxygenated functional groups (graphite oxide, GrO) could affect the electrochemical features of a classical CPE. By introducing oxygen termination over the graphite surface, a remarkable improvement in electrochemical performance was verified, including enhancement of analytical signals and charge transfer kinetics, as demonstrated from electrochemical characterisation assays conducted by cyclic voltammetry and electrochemical impedance spectroscopy towards the potassium hexa-cyanoferrate (II/III) probe. In addition, a positive effect was noted from the anchoring of Au nanoparticles on GrOPE. In analytical terms, two biologically relevant molecules were simultaneously determined using the proposed modified electrode based on GrO and AuNPs: epinephrine (EP) and uric acid (UA). Using differential pulse voltammetry (DPV), wide linear concentration ranges were founded for the analytical curves of EP and UA, and the limits of detection of 1.0×10−7 mol L−1 (EP) and 5.0×10−8 mol L−1 (UA) were predicted, respectively. The designed electrochemical sensor showed excellent precision of measurement and appropriate applicability for the analysis of biological fluids. [ABSTRACT FROM AUTHOR]

The application of nanodiamond (ND) in the preparation of an electrochemical sensor for the determination of pyrazinamide (PZA), one of the most consumed antibiotics for the treatment of tuberculosis, is proposed. The electrochemical sensor was constructed by the modification of a glassy carbon electrode (GCE) with an aqueous ND dispersion. The morphological characterization of the obtained ND film was carried out by scanning and transmission electron microscopy (SEM and TEM), and the electrochemical characterization assays were performed for the bare GCE and modified ND-GCE using potassium ferricyanide as redox probe. This redox probe showed an enhanced response on the ND-GCE, a higher electroactive surface area and a higher heterogeneous electron transfer rate constant ( k 0 ). The ND-GCE was employed in the PZA determination using square-wave voltammetry, and the obtained analytical curve was linear from 7.9 × 10 −7 to 4.9 × 10 −5 mol L −1 , with a limit of detection of 2.2 × 10 −7 mol L −1 . The proposed voltammetric method was successfully applied in the PZA determination in biological samples, with excellent recovery percentages. The proposed sensor architecture was notable for its simplicity of preparation and sensitivity towards the PZA drug, representing an interesting achievement in the preparation of nanodiamond-based electrochemical sensors. [ABSTRACT FROM AUTHOR]

Advances in analysis are required for rapid and reliable clinical diagnosis. Graphene is a 2D material that has been extensively used in the development of devices for the medical proposes due to properties such as an elevated surface area and excellent electrical conductivity. On the other hand, architectures have been designed with the incorporation of different biological recognition elements such as antibodies/antigens and DNA probes for the proposition of immunosensors and genosensors. This field presents a great progress in the last few years, which have opened up a wide range of applications. Here, we highlight a rather comprehensive overview of the interesting properties of graphene for in vitro , in vivo, and point-of-care electrochemical biosensing. In the course of the paper, we first introduce graphene, electroanalytical methods (potentiometry, voltammetry, amperometry and electrochemical impedance spectroscopy) followed by an overview of the prospects and possible applications of this material in electrochemical biosensors. In this context, we discuss some relevant trends including the monitoring of multiple biomarkers for cancer diagnostic, implantable devices for in vivo sensing and, development of point-of-care devices to real-time diagnostics. [ABSTRACT FROM AUTHOR]

New insights into the design of highly sensitive, carbon-based electrochemical sensors are presented in this work by exploring the interesting properties of graphene oxide (GO) and ionic liquids (ILs). An electrochemical sensor based on the carbon paste electrode (CPE) modified with GO and IL was developed for the sensitive detection of ofloxacin using square-wave adsorptive anodic stripping voltammetry (SWAdASV). GO sheets were obtained from the acid treatment of graphene and characterized by scanning and transmission electronic microscopy (SEM and TEM) and selected area electron diffraction (SAED), and the electrochemical behavior of the modified GO-IL/CPE was explored by electrochemical impedance spectroscopy studies. The CPE modification with GO and IL allowed an 8.2 fold increase in the analytical sensitivity for ofloxacin sensing compared to the unmodified CPE. Under the optimized experimental conditions using the SWAdASV technique, the GO-IL/CPE sensor provided an analytical curve for ofloxacin in the concentration range of 7.0×10 −9 to 7.0×10 −7 mol L −1 , with a sensitivity of 7.7×10 6 μA L mol −1 and limit of detection of 2.8×10 −10 mol L −1 (0.28 nmol L −1 ). The proposed sensor was successfully applied for the ofloxacin determination in human urine and ophthalmic samples, with recoveries near 100%. The results were similar those obtained by a spectrophotometric comparative method. [ABSTRACT FROM AUTHOR]

A sensitive way to determine levofloxacin using a sensor based on vertical aligned carbon nanotubes is described. The morphology and the electrochemical performance of the electrodes were characterised by atomic force microscopy, cyclic voltammetry and square wave voltammetry. A scan-rate study and electrochemical impedance spectroscopy showed that the levofloxacin oxidation product is adsorbed on the electrode surface. Differential pulse voltammetry in phosphate-buffer solution allowed the development of a method to determine levofloxacin levels in the range of 1.0-10.0 µmol L−1, with a detection limit of 75.2 nmol L−1. The proposed sensor was successfully applied in the determination of levofloxacin in urine, and the obtained results were in full agreement with those from the HPLC procedure. [ABSTRACT FROM AUTHOR]

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate and carbon black (CB) nanoparticles were incorporated within a crosslinked chitosan film over the surface of a glassy carbon electrode, and the obtained architecture explored to the sensitive voltammetric sensing of Allura red colorant in soft drinking powders. The different electrodic surfaces were morphologically and electrochemically characterized. From the modification of glassy carbon electrode with IL and CB, a significantly enhanced voltammetric response was achieved toward the Allura red irreversible oxidation reaction. The type and amount of IL employed in the electrode modification step as well as all the others experimental parameters affecting the sensor response by square-wave adsorptive anodic stripping voltammetry (SWAdASV) were systematically optimized. Under the optimum experimental conditions, the proposed SWAdASV procedure provided a linear analytical curve in the concentration range of 3.98 × 10−8 to 9.09 × 10−7 mol L−1 and a low limit of detection of 9.1 × 10−10 mol L−1 (0.91 nmol L−1). The proposed sensor presented good precision and no matrice effects as shown from repeatability tests, concomitant studies and addition/recovery assays. The developed SWAdASV procedure was applied successfully in the determination of Allura red content in commercial soft drink powder samples, and the results were in close agreement with those obtained using a comparative spectrophotometric method at a confidence level of 95%. Image 1 • Nanostructured sensor based on carbon black nanoparticles and ionic liquid. • Synergism of carbon black and ionic liquid as electrode modifiers. • Electrochemical sensing of allura red at nanomolar levels. • Food analysis by electroanalytical tools. [ABSTRACT FROM AUTHOR]

Carbon nanomaterials thin films have been attracted considerable attention in the last years due to relative low cost and excellent electrical conductivity features. We report here on novel sensor architecture consisted of a glassy carbon surface modified with manioc starch and nanodiamonds nanoparticles. Structural and morphological properties of this thin film were investigated by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies. By using square-wave voltammetry as electroanalytical tool, the widely used herbicide diquat (DQ) was determined in environmental samples. The modified electrode presented a linear response to DQ in the concentration range of 5.0 × 10−7 to 4.6 × 10−5 mol L−1 with a limit of detection of 1.1 × 10−7 mol L−1. This novel sensor proved to be efficient to determine if DQ is present in rivers and drinking water samples. Unlabelled Image • Films based on nanodiamonds confined in biodegradable manioc starch are reported. • Diquat herbicide is determined by square-wave voltammetry. • Sub-micromolar detection of diquat is achieved by exploring the novel nanodiamonds based sensor. • The developed nanostructured sensor is efficiently applied for diquat quantification in environmental samples. [ABSTRACT FROM AUTHOR]

Abstract A glassy carbon electrode (GCE) modified with single-walled carbon nanohorns (SWCNH) and zein (ZE), a prolamin type-protein find in maize, for the differential pulse adsorptive cathodic stripping voltammetric determination of fenitrothion (FT) is proposed. The proposed film was characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Regarding the electrochemical characterization, comparing the results obtained by cyclic voltammetry and electrochemical impedance spectroscopy, the modified electrode (SWCNH-ZE/GCE) showed an electroactive surface area 3 times higher and faster electron transfer kinetic than bare GCE. By using differential pulse adsorptive cathodic stripping voltammetry and SWCNH-ZE/GCE the analytical curve exhibited a linear response ranging of 9.9 × 10−7 to 1.2 × 10−5 mol L−1, with a limit of detection of 1.2 × 10−8 mol L−1. The proposed sensor was successfully applied for the determination of FT pesticide in natural water and orange juice samples. Moreover, the electrochemical sensor showed good repeatability and reproducibility arising from the excellent film stability, suggesting that the proposed architecture has broad potential for applications in sensing and biosensing. Graphical abstract Unlabelled Image Highlights • Zein is a protein that can be used for thin film preparation. • Single-walled carbon nanohorns were applied in electrochemical sensors. • A voltammetric sensor for fenitrothion determination is proposed. • Fenitrothion is successfully quantified in orange juice and water samples. [ABSTRACT FROM AUTHOR]

Porous boron-doped diamond (p-BDD) electrodes were prepared and explored as a potential electrochemical sensor for applications in flow-injection analysis (FIA) coupled to amperometric detection systems. Porous BDD films were grown by Hot Filament Chemical Vapor Deposition (HFCVD) over oxygen plasma functionalized carbon nanotubes and, morphological and chemical characterizations of the obtained composite material were carried out by Field Emission Gun Scanning Electron Microscopy (FEG-SEM) and Raman spectroscopy. The analytical performance of the designed p-BDD electrode under FIA conditions was investigated using two model electroactive analytes, epinephrine (EP, an important neurotransmitter) and acetaminophen (AC, a commonly consumed analgesic). All experimental parameters, such as applied potential, flow-rate and injection volume for both analytes were optimized. Under the best experimental conditions, the analytical curves for EP and AC were linear from 0.60 to 30.0 μmol L − 1 (EP) and from 0.80 to 70.0 μmol L − 1 (AC), with detection limits of 0.50 μmol L − 1 and 0.70 μmol L − 1 for EP and AC, respectively. Measurement precision was demonstrated from a number of amperometric measurements performed for successive injections of standard AC and EP solutions. In addition, the applicability of the developed FIA procedure was reported for the AC and EP determination in human serum fluid. [ABSTRACT FROM AUTHOR]

We report a solvothermal synthesis of ultrasmall platinum nanoparticles (USPtNPs) with an average size of 0.204 (± 0.008) nm using reline deep eutectic solvent (DES) as a stabilizing medium at a temperature of 80 ºC. SEM and EDS were used to morphologically characterize the USPtNPs. These revealed approximately spherical shapes with emission lines characteristic of platinum. DES was characterized by FT-IR and NMR, which indicated its formation through hydrogen bonds between the precursors. DSC was also used to characterize the precursors and the formed DES. Furthermore, an electrochemical sensor for determining riboflavin (RB) in commercial energy drinks and biological fluids was developed using the USPtNPs together with multiwalled carbon nanotubes (MWCNT). The USPtNPs-DES/MWCNT/GCE film was characterized by SEM, which demonstrated the characteristic tubular morphology of MWCNT. The RB voltammetric response was studied, and a significant enhanced on the current response was observed, especially due to the USPtNPs. This sensor displayed a linear response for RB in the range of 0.02–1.2µmol L−1, with a limit of detection of 1.8 nmol L−1. Besides detectability at nanomolar range, excellent performance was verified for repeatability and anti-interference features. The sensor based on extraordinary USPtNPs synthesized in DES in a simpler and environmentally friendly way was successfully applied to determine RB in different matrices. • First synthesis of USPtNPs using deep eutectic solvent as stabilizing medium. • USPtNPs with an average size of 0.208 nm obtained in a solvothermal synthesis. • First sensor based on USPtNPs and MWCNTs to detect RB in biological and food samples. [ABSTRACT FROM AUTHOR]

The outstanding electronic properties of carbon black (CB) and its economic advantages have fueled its application as nanostructured electrode material for the development of new electrochemical sensors and biosensors. CB-based electrochemical sensing devices have been found to exhibit high surface area, fast charge transfer kinetics, and excellent functionalization. In the present work, we set forth a comprehensive review of the recent advances made in the development and application of CB-based electrochemical devices for pharmaceutical and biomedical analyses – from quantitative monitoring of drug formulations to clinical diagnoses - and the underlying challenges and constraints that need to be overcome. We also present a thorough discussion about the strategies and techniques employed in the development of new electrochemical sensing platforms and in the enhancement of their analytical properties and biocompatibility for anchoring active biomolecules, as well as the combination of these sensing devices with other materials aiming at boosting the performance and efficiency of the sensors. • Carbon black as an inexpensive and high-performance electrochemical material. • Last advances on carbon black-modified electrodes for pharmaceutical and biomedical analyses. • Electrochemical sensing and biosensing approaches have been discussed. • Perspectives and challenges on carbon-black based (bio)sensors are highlighted. [ABSTRACT FROM AUTHOR]

In this work, an electrochemical sensor based on vertically oriented carbon nanotubes (voMWCNT), electrically wired via connection upon a copper plate, for the detection of tadalafil (TD) is reported. The voMWCNT is easily prepared via microwave plasma reactor with no additional post-treatment. The voMWCNT was characterized by scanning and transmission electron microscopy in addition to electrochemical characterization with cyclic voltammetry. Once TD is of easy access and used in the treatment of erectile dysfunction and related diseases, the quality control of this drug is of high importance. Using linear sweep voltammetry, the detection of TD was found to be possible from 0.85 to 8.9 μmol L−1, with an R2 of 0.992 with a limit of detection found to correspond to 78 nmol L−1. The quantification of TD in different pharmaceutical drugs, as well as the device stability, indicates that the voMWCNT has potential for the routine sensing of TD. Unlabelled Image [ABSTRACT FROM AUTHOR]

A low-cost and disposable microcell was constructed with a screen-printed electrode for the non-enzymatic electrochemical determination of creatinine. The working electrode was modified with carbon black and maintained in contact with paper-adsorbed iron (III) ions. A small sample volume of 3 μL was required for the device operation. Then, iron (III) ions were complexed in the presence of creatinine in a chemical step, followed by an electrochemical reduction of non-complexed metallic ions in excess. Cyclic voltammetry and differential-pulse voltammetry experiments were employed for the electrochemical characterizations and analytical performance evaluation of the microcell. The working electrode modification with carbon black provided a significant increase of analytical signal. The sensor presented a linear response for creatinine concentrations ranging from 0.10 to 6.5 mmol L−1, with a limit of detection of 0.043 mmol L−1. Experiments for creatinine determination in real samples were successful performed through of standard recovery in urine. Image 1 • Creatinine was determinate by a non-enzymatic, low-cost, and disposable microcell. • A small urine sample volume of 3 μL was required for the operation of the device. • The working electrode modification with carbon black provided a significant increase of analytical signal. [ABSTRACT FROM AUTHOR]