Fused and unzipped carbon nanotubes, electrochemically treated, for selective determination of dopamine and serotonin

Glassy carbon electrodes (GC) were modified with multiwalled carbon nanotubes (MWCNT/GC) and electrochemically treated first by applying an oxidation potential and then a reduction potential. The resulting electrodes were characterized via scanning electron microscopy, Raman spectroscopy, energy dispersive spectroscopy, and electrochemical techniques, particularly cyclic voltammetry using the redox probes Fe(CN)6 3− /4- and Ru(NH3)2+/3+ and electrochemical impedance spectroscopy using Fe(CN)6 3− /4-. These modified electrodes showed an electrochemical determination selective for dopamine (DA) and serotonin (5HT) in the presence of ascorbic acid (AA) and uric acid (UA), simultaneously measured, with a high reproducibility (an RSD of 1.7% for DA and 1.6% for 5HT) and a limit of detection (LOD) of 235 nmol L−1 for DA and 460 nmol L−1 for 5HT. The GC electrodes modified with oxidized MWCNT, subsequently reduced, showed higher selectivity towards the oxidation of DA and 5HT compared with GC bare electrodes or modified with MWCNT or oxidized MWCNT.Fil: Bonetto, Maria Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Muñoz, Fernando Francisco. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Diz, Virginia Emilse. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Sacco, Natalia Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Corton, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Enhanced voltammetric performance of sensors based on oxidized 2D layered black phosphorus

The exceptional properties of 2D layered black phosphorus (BP) make it a promising candidate for electrochemical sensing applications and, even though BP is considered unstable and tends to degrade by the presence of oxygen and moisture, its oxidation can be beneficial in some situations. In this work, we present an unequivocal demonstration that the exposition of BP-based working electrodes to normal ambient conditions can indeed be advantageous, leading to an enhancement of voltammetric sensing applications. This point was proved using a BP modified screen-printed carbon electrode (BP-SPCE) for the voltammetric determination of dopamine (DA) as a model target analyte. Oxidized BP-SPCE (up to 35% of PxOy at the surface) presented an enhanced analytical performance with a 5-fold and 2-fold increase in sensitivity, as compared to bare-SPCE and non-oxidized BP-SPCE stored in anhydrous atmosphere, respectively. Good detection limit, repeatability, reproducibility, stability, selectivity, and accuracy were also achieved. Overall, the results presented herein display the prominent possibilities of preparing and working with BP based-sensors in normal ambient settings and showcase their implementation under physiological conditions

An efficient sensor based on anodic activation of graphene oxide for sensitive and selective determination of dopamine in blood serum

A native graphene oxide (NGO) prepared by Hummers modified method was used as the template materials for the fabrication of electrochemically oxidative graphene oxide (OGO) onto a glassy carbon electrode (GCE). The fabrication of OGO-GCE persuaded via anodic reversible potentiodynamic of NGO base surface materials that increases the concentration of oxygen functionalities. The development of a new aldehyde/alcoholic functional group on OGO-GCE characterized by XPS analysis is a marked signal for oxygen richness surface which provoked on the cost of sp2 hybridized function. The EIS data underline that OGO-GCE promote the electron transfer kinetics much more than NGO-GCE by 9 times as estimated by the rate constant calculation. The XPS and EIS data highlight the influence of anodic treatment on increasing the interlayer spacing distance between the resultant OGO. Differential pulse voltammetry (DPV) results were evident for a promising efficiency of OGO-GCE on the simultaneous determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA). In addition, the selectivity of the proposed sensor for DA quantification in the presence of high concentrations of AA and UA was achieved successfully with a detection limit (DL3s) approach to 12 nM. The analytical performance of OGO-GCE on serum blood revealed its potential application for trace DA quantification

Graphene — A Platform for Sensor and Biosensor Applications

Graphene, mother of all carbon materials, has opened up new era of exploration due to its unique properties. Graphene, one-atom thick, exhibits a unique chemical structure and outstanding electronic, optical, thermal, and mechanical properties that made it compelling for various engineering applications. Graphene and graphene-based materials are promising candidates for fabricating state-of-the-art nano-scale sensors and biosensors. They featured with good conductivity and large specific surface area thereby; graphene-based sensors/biosensors performed well with good accuracy, rapidness, high sensitivity and selectivity, low detection limits, and long-term stability. They are ideally used as gas sensors, electrochemical sensors for heavy metal ions, immunosensors and dihydronicotinamide dinucleotide NADH, DNA, catecholamine neurotransmitters, paracetamol, glucose, H2O2, hemoglobin, and myoglobin biosensors. This chapter reviews the applications of graphene in nanotechnology since it came to the field particularly in sensing and biosensing applications. It updates the reader with the scientific progress of the current use of graphene as sensors and biosensors. There is still much room for the scientific research and application development of graphene-based theory, materials, and devices. Despite the vast amount of research already conducted on graphene for various applications, the field is still growing and many questions remain to be answered

Engineered carbon-nanomaterial-based electrochemical sensors for biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.ope

Optimization of electrochemical detection of L-Ascorbic acid from Plant Food Supplements using screen printed transducers

The importance of Ascorbic acid (vitamin C) in several biological processes, and during the last years as active compounds used in several pesticides (L-Ascorbic acid is used as a fungicide on glasshouse tomato, potato, and field and glasshouse flower bulbs) is a challenge for groups of researchers to develop new, rapid and sensitive method for its detection. Methods for the detection of Ascorbic acid (AA) were developed and optimised using differential pulse voltammetry (DPV) analysis with modified carbon-printed electrodes with cobalt phthalocyanine. There was studied detection of Ascorbic acid in hydrochloric acid 2% as supporting media. Results showed that the method developed for Ascorbic acid analyses can be used to assay different samples as teas and plant food supplements containing different botanicals

Modification of electrodes with N-and S-doped carbon dots. Evaluation of the electrochemical response

Altres ajuts: MdV thanks the support from program ICREA Academia. MBSE thanks to la Secretaria d'Universitats i Recerca del Departament d'Empreses i Coneixement de la Generalitat de Catalunya and to European Social Fund, European Union for a FI fellowship.Nitrogen and sulphur-doped Carbons Dots (N-CDs and S-CDs) were synthesized by a hydrothermal method and incorporated as surface electrode modifiers to evaluate their properties for electrochemical sensing. The first task was to characterize the synthesized materials, for which different spectroscopies, scanning microscopes, mass spectrometry and elementary analysis were performed. Next, a glassy carbon electrode (GCE) was surface-modified with the doped CDs and applied to check the electrochemical signal of different organic compounds corresponding to different families. Water solubility of the doped carbon dots forced us to incorporate them in a graphite-polystyrene ink to complete the modification of electrodes. This modification needed a first activation to obtain a properly conductive surface. The organic compounds examined were salicylic acid, cysteine and ascorbic acid. The modified GCEs exhibited an enhanced sensitivity, probably caused by the increase of active surface, but in addition, signals of salicylic acid were shifted ca. 200 mV to lower potentials, what is a proof of the increase of the heterogeneous electron transfer rate, and a demonstration of an enhanced catalytic response

Construction of Heteroatom-Doped Porous Carbon Architectures for Energy and Sensing Applications

In this chapter, we have concentrated on the main electrocatalytic oxygen processes, oxygen reduction reaction (ORR) and water splitting oxygen evolution reaction (OER), and biosensors based on porous carbon architectures, which are more important areas of research because of the rise in demand for energy management, supply, and disease diagnosis. Heteroatom-doped carbon hollow spheres are very useful because they have a large surface area, mesoporosity, spherical wall thicknesses, edge plane defect sites, catalytic active sites, and fast heterogeneous electron-transfer rates. These properties are very important for making commercial devices. This chapter provides an overview of hollow carbon nanospheres that are doped with single and double heteroatoms, as well as cobalt oxide. These carbon compounds function as dual catalysts for OER and ORR, as well as an effective electrocatalyst for the oxygen reduction process in both acidic and alkaline media. Electrocatalytically, heteroatom-doped carbon sphere-modified electrodes can simultaneously and specifically identify and determine the analytes, while also validating the target species in real samples. N-doped hollow carbon spheres coated-Co3O4 functioned as an efficient dual-function oxygen electrocatalyst for oxygen evolution and oxygen reduction processes and also as a biosensor for highly effective electrochemical sensing of acetaminophen. A symmetric supercapacitor using dual heteroatom-doped and SBA-15 templated porous carbon was also discussed