Simultaneous and sensitive determination of ascorbic acid, dopamine, uric acid, and tryptophan with silver nanoparticles-decorated reduced graphene oxide modified electrode.
TL;DR: The synthesis of silver nanoparticle-decorated reduced graphene oxide composite (AgNPs/rGO) by heating the mixture of graphene oxide and silver nitrate aqueous solution in the presence of sodium hydroxide is reported.
About: This article is published in Colloids and Surfaces B: Biointerfaces.The article was published on 2013-11-01. It has received 233 citations till now. The article focuses on the topics: Ascorbic acid & Silver nitrate.
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TL;DR: This review article gives a brief overview of 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.
Abstract: 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.
393 citations
TL;DR: In this paper, the authors reviewed the materials that have been extensively used to fabricate modified electrode surfaces for detection of dopamine in real samples and discussed the characteristics of these materials that improve the electrocatalytic activity of the modified surfaces.
Abstract: Dopamine (DA) is an important neurotransmitter and its abnormal concentrations are associated with different diseases. Electrochemical detection of DA in real samples is challenging because of the presence of high concentrations of electroactive interferents such as uric acid (UA) and ascorbic acid (AA). Chemically modified electrodes have been widely used to counter the problems of poor sensitivity and selectivity faced at bare electrodes. We have briefly reviewed the materials that have been extensively used to fabricate modified electrode surfaces for detection of DA. The characteristics of the materials that improve the electrocatalytic activity of the modified surfaces are discussed. The boundary of search was limited to the electrochemical methods dealing with the simultaneous detection of DA, UA, and AA levels or detection of only DA in the presence of UA and AA. Challenges associated with the quantitative determination of dopamine in real samples are critically reviewed and the possible solutions are described.
277 citations
TL;DR: In this paper, a review of graphene-based composite modified electrodes with their improved sensing performance towards dopamine (DA) along with several interfering species is presented, and some important strategies to improve the selectivity and sensitivity towards DA with graphene based composites are also described.
Abstract: Dopamine (DA) is an important catecholamine neurotransmitter in the mammalian central nervous system that influences several physiological functions. The impact of DA levels within the human body significantly affects the body functions. Maintaining DA level is essential and the electrochemical detection methods are often used to detect the DA level to regulate the body function. In this review, graphene (functionalized graphene and N-doped graphene) and its composites (metal, metal oxide, polymer, carbonaceous materials, clay, zeolite, and metal–organic framework based graphene composites) modified electrodes with their improved sensing performance towards DA along with several interfering species are described. Further, recent developments on the fabrication of various graphene based composite modified electrodes are also presented. Some important strategies to improve the selectivity and sensitivity towards DA with graphene based composite modified electrodes are also described.
251 citations
TL;DR: In this article, a comprehensive overview of the field apart from providing intensive information of the fabrication, properties, characterization and EC applications of graphene and its nanocomposites is provided, along with two key challenges, the lack of international regulatory guidelines for nanotoxicity analysis and potential mass production of analytical devices.
192 citations
TL;DR: A new type of tryptophan-functionalized graphene nanocomposite (Trp-GR) was synthesized by utilizing a facile ultrasonic method via π-π conjugate action between graphene (GR) and tryPTophan ( Trp) molecule to have well dispersivity in water and better conductivity than pure GR.
157 citations
References
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26,456 citations
Book•
01 Jan 1980
TL;DR: In this paper, the authors present a comprehensive overview of electrode processes and their application in the field of chemical simulation, including potential sweep and potential sweep methods, coupled homogeneous chemical reactions, double-layer structure and adsorption.
Abstract: Major Symbols. Standard Abbreviations. Introduction and Overview of Electrode Processes. Potentials and Thermodynamics of Cells. Kinetics of Electrode Reactions. Mass Transfer by Migration and Diffusion. Basic Potential Step Methods. Potential Sweep Methods. Polarography and Pulse Voltammetry. Controlled--Current Techniques. Method Involving Forced Convention--Hydrodynamic Methods. Techniques Based on Concepts of Impedance. Bulk Electrolysis Methods. Electrode Reactions with Coupled Homogeneous Chemical Reactions. Double--Layer Structure and Adsorption. Electroactive Layers and Modified Electrodes. Electrochemical Instrumentation. Scanning Probe Techniques. Spectroelectrochemistry and Other Coupled Characterization Methods. Photoelectrochemistry and Electrogenerated Chemiluminescence. Appendix A: Mathematical Methods. Appendix B: Digital Simulations of Electrochemical Problems. Appendix C: Reference Tables. Index.
20,533 citations
TL;DR: It is reported that chemically converted graphene sheets obtained from graphite can readily form stable aqueous colloids through electrostatic stabilization, making it possible to process graphene materials using low-cost solution processing techniques, opening up enormous opportunities to use this unique carbon nanostructure for many technological applications.
Abstract: Graphene sheets offer extraordinary electronic, thermal and mechanical properties and are expected to find a variety of applications. A prerequisite for exploiting most proposed applications for graphene is the availability of processable graphene sheets in large quantities. The direct dispersion of hydrophobic graphite or graphene sheets in water without the assistance of dispersing agents has generally been considered to be an insurmountable challenge. Here we report that chemically converted graphene sheets obtained from graphite can readily form stable aqueous colloids through electrostatic stabilization. This discovery has enabled us to develop a facile approach to large-scale production of aqueous graphene dispersions without the need for polymeric or surfactant stabilizers. Our findings make it possible to process graphene materials using low-cost solution processing techniques, opening up enormous opportunities to use this unique carbon nanostructure for many technological applications.
8,534 citations
TL;DR: In this review, experimental results for the D, D' and G' bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed.
Abstract: Raman spectroscopy has historically played an important role in the structural characterization of graphitic materials, in particular providing valuable information about defects, stacking of the graphene layers and the finite sizes of the crystallites parallel and perpendicular to the hexagonal axis Here we review the defect-induced Raman spectra of graphitic materials from both experimental and theoretical standpoints and we present recent Raman results on nanographites and graphenes The disorder-induced D and D′ Raman features, as well as the G′-band (the overtone of the D-band which is always observed in defect-free samples), are discussed in terms of the double-resonance (DR) Raman process, involving phonons within the interior of the 1st Brillouin zone of graphite and defects In this review, experimental results for the D, D′ and G′ bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed We also present recent advances that made possible the development of Raman scattering as a tool for very accurate structural analysis of nano-graphite, with the establishment of an empirical formula for the in- and out-of-plane crystalline size and even fancier Raman-based information, such as for the atomic structure at graphite edges, and the identification of single versus multi-graphene layers Once established, this knowledge provides a powerful machinery to understand newer forms of sp2 carbon materials, such as the recently developed pitch-based graphitic foams Results for the calculated Raman intensity of the disorder-induced D-band in graphitic materials as a function of both the excitation laser energy (Elaser) and the in-plane size (La) of nano-graphites are presented and compared with experimental results The status of this research area is assessed, and opportunities for future work are identified
3,601 citations
TL;DR: In this article, a detailed analysis of the thermal expansion mechanism of graphite oxide to produce functionalized graphene sheets is provided, where it is shown that the decomposition rate of the epoxy and hydroxyl sites exceeds the diffusion rate of evolved gases, yielding pressures that exceed the van der Waals forces holding the graphene sheets together.
Abstract: A detailed analysis of the thermal expansion mechanism of graphite oxide to produce functionalized graphene sheets is provided. Exfoliation takes place when the decomposition rate of the epoxy and hydroxyl sites of graphite oxide exceeds the diffusion rate of the evolved gases, thus yielding pressures that exceed the van der Waals forces holding the graphene sheets together. A comparison of the Arrhenius dependence of the reaction rate against the calculated diffusion coefficient based on Knudsen diffusion suggests a critical temperature of 550 °C which must be exceeded for exfoliation to occur. As a result of their wrinkled nature, the functionalized and defective graphene sheets do not collapse back to graphite oxide but are highly agglomerated. After dispersion by ultrasonication in appropriate solvents, statistical analysis by atomic force microscopy shows that 80% of the observed flakes are single sheets.
3,340 citations