The Experts below are selected from a list of 11244 Experts worldwide ranked by ideXlab platform
Dimitrios Berk - One of the best experts on this subject based on the ideXlab platform.
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Generation and functionalization of pure graphene flake structures in thermal plasma reactors
2012 Abstracts IEEE International Conference on Plasma Science, 2012Co-Authors: Jean-luc Meunier, N.-y. Mendoza-gonzalez, R. Pristavita, Dustin Binny, Dimitrios BerkAbstract:Summary form only given. This project relates to the creation of a specific Carbon structure for the replacement of Pt catalyst by a non-noble metal such as Fe functionalized on the Carbon support [Proietti, E., et al., 2011]. Pt-Nanoparticles are typically used as catalyst materials in a large series of applications, for example in the development of polymer electrolyte membrane fuel cells (PEM-FC) as electrical energy sources for the car industry. One main limiting factor in the demand scale up is the availability and increasing price of Pt. Iron atoms dispersed at the atomic level directly on Carbon Nanoparticles using nitrogen coordination mimicking the blood structure proved recently to have activities that can rival Pt-based catalyst; the stability of this complex however is lacking and high crystallinity of the support structure proved to strongly improve this parameter. The high temperatures attained for Carbon Nanoparticle nucleation in thermal plasma reactors enable increased crystallinity, however the control, reproducibility and purity are often lacking in such devices. These are addressed in the present research. Modeling and experimental results related to the design of the flow/energy/ nucleation fields in an IC-Thermal Plasma reactor for the nucleation of Carbon nanomaterials, and their specific functionalization is presented. A “properly” designed conical geometry of the reactor enables a fine adjustment of the nucleation zone that minimizes the condensation process and essentially eliminates coagulation of the particles. Very good control over purity and reproducibility are attained through the elimination of recirculation fields. The local high temperature enables the nucleation of pure graphene flakes having between 5-16 atomic planes, and planar structures of typically 50nm×100nm [Pristavita, R., et al., 2011]. The nucleation zone of Carbon Nanoparticles is modeled, this zone being very stable under varying process conditions and leads to a robust process under parametric fluctuations. Nucleation zones and functionalization zones being separated, nitrogen functionalization on specific pyridinic sites is attained downstream of the nanoflake nucleation. Tests made on this non-noble catalyst in PEM-FC operation highlighted the strong improvement in stability of the catalyst, while increased activities from increased levels of functional sites are still required.
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Carbon Nanoparticle production by inductively coupled thermal plasmas: Controlling the thermal history of particle nucleation
Plasma Chemistry and Plasma Processing, 2011Co-Authors: R. Pristavita, N.-y. Mendoza-gonzalez, Jean-luc Meunier, Dimitrios BerkAbstract:The process control for reproducibility, uniformity, and achievement of desired structures for Carbon black generated in thermal plasma devices is studied in this paper through modeling, and correlated with experimental results. A numerical simulation of the flow and energy fields, stream function lines and the quench rates of the plasma gas in a conical shape reactor at different pressures was made. An argon plasma is used with highly diluted methane (0.6–7%) as the Carbon precursor. The quench rates were studied in order to observe the flow development and hence the thermal history of particle nucleation. Three pressure cases of 20.7, 55.2 and 101.3 kPa and two plasma powers cases of 10 and 20 kW were studied. The modeling results enabled Carbon nanoflakes production in the experimental tests performed on an inductively coupled thermal plasma system. Results indicate a robust process control enabling very little particle morphology variation over this wide range of reactor pressure values and varying plasma power, and a very high reproducibility of the particle morphologies obtained.
Yu Guo Guo - One of the best experts on this subject based on the ideXlab platform.
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Wet Chemistry Synthesis of Multidimensional NanoCarbon-Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium-Sulfur Batteries
ACS Applied Materials and Interfaces, 2016Co-Authors: Wen Cheng Du, Ya Xia Yin, Xian Xiang Zeng, Shuai Feng Zhang, Ji Lei Shi, Li Jun Wan, Yu Guo GuoAbstract:An optimized nanoCarbon–sulfur cathode material with ultrahigh sulfur loading of up to 90 wt % is realized in the form of sulfur nanolayer-coated three-dimensional (3D) conducting network. This 3D nanoCarbon–sulfur network combines three different nanoCarbons, as follows: zero-dimensional Carbon Nanoparticle, one-dimensional Carbon nanotube, and two-dimensional graphene. This 3D nanoCarbon–sulfur network is synthesized by using a method based on soluble chemistry of elemental sulfur and three types of nanoCarbons in well-chosen solvents. The resultant sulfur–Carbon material shows a high specific capacity of 1115 mA h g–1 at 0.02C and good rate performance of 551 mA h g–1 at 1C based on the mass of sulfur–Carbon composite. Good battery performance can be attributed to the homogeneous compositing of sulfur with the 3D hierarchical hybrid nanoCarbon networks at nanometer scale, which provides efficient multidimensional transport pathways for electrons and ions. Wet chemical method developed here provides an ...
Frank Marken - One of the best experts on this subject based on the ideXlab platform.
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Voltammetric Chloride Sensing Based on Trace-Level Mercury Impregnation Into Amine-Functionalized Carbon Nanoparticle Films
IEEE Sensors Journal, 2017Co-Authors: Haneie Salehniya, Mandana Amiri, Frank MarkenAbstract:A voltammetric sensor for the determination of chloride ions is proposed. At trace level, Hg(II) ions (ca. 15 × 10-12 mol or only approximately 3 Hg2+ cations per Carbon Nanoparticle) are adsorbed at the surface of amine-functionalized Carbon Nanoparticles in a film supported on a glassy Carbon electrode. With this redox-active film, voltammetric chloride determination is possible without loss of mercury/signal in repeatable measurements and over a very wide chloride concentration range. The sensor mechanism is based on the shift of the voltammetric peak potential for the Hg/Hg2Cl2 redox transformation in the presence of chloride anions. Only trace-level mercury is employed, so that problems associated with traditional bulk mercury electrodes are not encountered. Differential pulse voltammograms were recorded over a wide range of chloride concentrations resulting in two regimes (from 5 × 10-5 to 1 M and from 1 to 3 M) with linear peak potential shift with a chloride concentration of -63.2 ± 0.09 mV/pCl and -109.1 ± 0.4 mV/pCl, respectively (at 25 °C). The sensor performance is promising in real samples, such as lake water, sea water, and table salt.
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Functionalized Carbon Nanoparticles, blacks and soots as electron-transfer building blocks and conduits
Chemistry-an Asian Journal, 2014Co-Authors: Kate Lawrence, Tony D James, Steven D Bull, Marcin Opallo, Charlotte L. Baker, Ruth Lawrence, John M. Mitchels, Omotayo A. Arotiba, Kenneth I. Ozoemena, Frank MarkenAbstract:Functionalized Carbon Nanoparticles (or blacks) have promise as novel active high-surface-area electrode materials, as conduits for electrons to enzymes or connections through lipid films, or as nano-building blocks in electroanalysis. With previous applications of bare nanoblacks and composites mainly in electrochemical charge storage and as substrates in fuel cell devices, the full range of benefits of bare and functionalized Carbon Nanoparticles in assemblies and composite (bio)electrodes is still emerging. Carbon Nanoparticles are readily surface-modified, functionalized, embedded, or assembled into nanostructures, employed in bioelectrochemical systems, and incorporated into novel electrochemical sensing devices. This focus review summarizes aspects of a rapidly growing field and some of the recent developments in Carbon Nanoparticle functionalization with potential applications in (bio)electrochemical, photoelectrochemical, and electroanalytical processes.
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Carbon Nanoparticle surface electrochemistry high density covalent immobilisation and pore reactivity of 9 10 anthraquinone
Electroanalysis, 2011Co-Authors: John D Watkins, Kate Lawrence, James E Taylor, Tony D James, Steven D Bull, Frank MarkenAbstract:2-Bromomethyl-9,10-anthraquinone is covalently bound to Carbon Nanoparticle surfaces (Emperor 2000, Cabot Corp., with sulphonamide groups, ca. 9 to 18 nm diameter) with a coverage of ca. 250 anthraquinone molecules per particle (ca. 180 angstrom(2) per anthraquinone). The resulting hydrophobic Carbon particles are dispersed in ethanol and coated onto glassy Carbon electrodes. Electrochemical experiments are reported demonstrating the effect of surface coverage, scan rate, and pH. A linear shift in reversible potential of ca. 59 mV per pH unit from pH 2 to 12 is observed consistent with the reversible 2-electron 2-proton reduction of anthraquinone. High density of anthraquinone in Carbon Nanoparticle aggregates causes buffer capacity effects. Binding of hydrophobic tetraphenylborate anions into Carbon Nanoparticle aggregate pores is demonstrated. Applications in buffer characterisation and pH-sensing are discussed.
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Introducing hydrophilic Carbon Nanoparticles into hydrophilic sol-gel film electrodes
Journal of Solid State Electrochemistry, 2007Co-Authors: Stuart M. Macdonald, Frank Marken, Katarzyna Szot, Joanna Niedziolka, Marcin OpalloAbstract:A hydrophilic Carbon Nanoparticle–sol-gel electrode with good electrical conductivity within the sol-gel matrix is prepared. Sulfonated Carbon Nanoparticles with high hydrophilicity and of 10–20 nm diameter (Emperor 2000) are co-deposited onto tin-doped indium oxide substrates employing a sol-gel technique. The resulting Carbon Nanoparticle-sol-gel composite electrodes are characterized as a function of composition and salt (KCl) additive. Scanning electron microscopy and voltammetry in the absence and in the presence of a solution redox system suggest that the composite electrode films can be made electrically conducting and highly porous to promote electron transport and transfer. The effect of the presence of hydrophilic Carbon Nanoparticles is explored for the following processes: (1) double layer charging, (2) diffusion and adsorption of the electrochemically reversible solution redox system 1,1′-ferrocenedimethanol, (3) electron transfer to the electrochemically irreversible redox system hydrogen peroxide, and (4) electron transfer to the redox liquid tert-butylferrocene deposited into the porous composite electrode film. The extended electrochemically active hydrophilic surface area is beneficial in particular for surface sensitive processes (1) and (3), and it provides an extended solid|organic liquid|aqueous solution boundary for reaction (4). The Carbon Nanoparticle–sol-gel composite electrodes are optimized to provide good electrical conductivity and to remain stable during electrochemical investigation.
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Ultrathin Carbon Nanoparticle composite film electrodes: Distinguishing dopamine and ascorbate
Electroanalysis, 2007Co-Authors: Mandana Amiri, Saeed Shahrokhian, Frank MarkenAbstract:Ultrathin Carbon Nanoparticle-poly(diallyldimethylammonium chloride) films (CNP-PDDAC films) are formed on tin-doped indium oxide (ITO) electrodes in a layer-by-layer electrostatic deposition process employing 9-18 nm diameter Carbon particles. Transparent and strongly adhering films of high electrical conductivity are formed and characterized in terms of their electrochemical reactivity. When immersed in aqueous 0.1 M phosphate buffer pH 7, each layer of CNP-PDDAC (of ca. 5 - 6 nm average thickness) is adding an interfacial capacitance of ca. 10 mu F cm(-2). Absorption into the CNP-PDDAC nanocomposite film is dominated by the sites in the PDDAC cationomer and therefore anionic molecules such as indigo carmine are strongly bound and retained within the film (cationic binding sites per layer ca. 150 pmol cm(-2)). In contrast, cationic redox systems such as ferrocenylmethyltrimethyl-ammonium(+) fail to bind. For solution phase redox systems such as hydroquinone, the rate of electron transfer is dramatically affected by the CNP-PDDAC film and switched from completely irreversible to highly reversible even with a single layer of Carbon Nanoparticles. For the mixed redox system ascorbate - dopamine in 0.1 M phosphate buffer pH 7 cyclic voltammograms suggest a rapid and selective temporary poisoning process which causes the ascorbate oxidation to be suppressed in the second potential cycle. This effect is exploited for the detection of micromolar concentrations of dopamine in the presence of millimolar ascorbate.
Wenjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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a recyclable Carbon Nanoparticle based fluorescent probe for highly selective and sensitive detection of mercapto biomolecules
Journal of Materials Chemistry B, 2015Co-Authors: Jinfeng Zhang, Yingsan Chui, Peng Wang, Xianfeng Chen, Hui Wang, Qingdan Yang, Jiechao Ge, Wenjun ZhangAbstract:Carbon Nanoparticles (CNPs) with strong blue emission are synthesized using a microwave-assisted hydrothermal method. The fluorescence of the CNPs can be completely quenched by Hg2+ through an effective electron or energy transfer process due to the synergetic strong electrostatic interaction and metal–ligand coordination. Based on this, a system containing Hg2+-quenched CNPs (CNP-Hg2+) is designed to be a sensitive and selective turn-on fluorescent probe towards cysteine (a type of mercapto biomolecule) with a detection limit of 15 nM. The fluorescence of CNP-Hg2+ aqueous solution can be repeatedly turned on and off for over 10 times by alternative addition of cysteine and Hg2+, respectively. After 10 cycles, the fluorescence intensity could be recovered to as high as 85% of the original value of CNPs. Remarkably, the sensing process is able to be observed by the naked eye under UV irradiation. Furthermore, the sensing is specific to biothiols and the sensor is able to work in living cells.
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Carbon Nanoparticle based ratiometric fluorescent sensor for detecting mercury ions in aqueous media and living cells
ACS Applied Materials & Interfaces, 2014Co-Authors: Jinfeng Zhang, Yingsan Chui, Peng Wang, Xianfeng Chen, Hoilun Kwong, Wenjun ZhangAbstract:A novel nanohybrid ratiometric fluorescence sensor is developed for selective detection of mercuric ions (Hg2+), and the application has been successfully demonstrated in HEPES buffer solution, lake water, and living cells. The sensor comprises water-soluble fluorescent Carbon Nanoparticles (CNPs) and Rhodamine B (RhB) and exhibits their corresponding dual emissions peaked at 437 and 575 nm, respectively, under a single excitation wavelength (350 nm). The photoluminescence of the CNPs in the nanohybrid system can be completely quenched by Hg2+ through effective electron or energy transfer process due to synergetic strong electrostatic interaction and metal–ligand coordination between the surface functional group of CNPs and Hg2+, while that of the RhB remains constant. This results in an obviously distinguishable fluorescence color variation (from violet to orange) of the nanohybrid solution. This novel sensor can effectively identify Hg2+ from other metal ions with relatively low background interference ...
R. Pristavita - One of the best experts on this subject based on the ideXlab platform.
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Generation and functionalization of pure graphene flake structures in thermal plasma reactors
2012 Abstracts IEEE International Conference on Plasma Science, 2012Co-Authors: Jean-luc Meunier, N.-y. Mendoza-gonzalez, R. Pristavita, Dustin Binny, Dimitrios BerkAbstract:Summary form only given. This project relates to the creation of a specific Carbon structure for the replacement of Pt catalyst by a non-noble metal such as Fe functionalized on the Carbon support [Proietti, E., et al., 2011]. Pt-Nanoparticles are typically used as catalyst materials in a large series of applications, for example in the development of polymer electrolyte membrane fuel cells (PEM-FC) as electrical energy sources for the car industry. One main limiting factor in the demand scale up is the availability and increasing price of Pt. Iron atoms dispersed at the atomic level directly on Carbon Nanoparticles using nitrogen coordination mimicking the blood structure proved recently to have activities that can rival Pt-based catalyst; the stability of this complex however is lacking and high crystallinity of the support structure proved to strongly improve this parameter. The high temperatures attained for Carbon Nanoparticle nucleation in thermal plasma reactors enable increased crystallinity, however the control, reproducibility and purity are often lacking in such devices. These are addressed in the present research. Modeling and experimental results related to the design of the flow/energy/ nucleation fields in an IC-Thermal Plasma reactor for the nucleation of Carbon nanomaterials, and their specific functionalization is presented. A “properly” designed conical geometry of the reactor enables a fine adjustment of the nucleation zone that minimizes the condensation process and essentially eliminates coagulation of the particles. Very good control over purity and reproducibility are attained through the elimination of recirculation fields. The local high temperature enables the nucleation of pure graphene flakes having between 5-16 atomic planes, and planar structures of typically 50nm×100nm [Pristavita, R., et al., 2011]. The nucleation zone of Carbon Nanoparticles is modeled, this zone being very stable under varying process conditions and leads to a robust process under parametric fluctuations. Nucleation zones and functionalization zones being separated, nitrogen functionalization on specific pyridinic sites is attained downstream of the nanoflake nucleation. Tests made on this non-noble catalyst in PEM-FC operation highlighted the strong improvement in stability of the catalyst, while increased activities from increased levels of functional sites are still required.
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Carbon Nanoparticle production by inductively coupled thermal plasmas: Controlling the thermal history of particle nucleation
Plasma Chemistry and Plasma Processing, 2011Co-Authors: R. Pristavita, N.-y. Mendoza-gonzalez, Jean-luc Meunier, Dimitrios BerkAbstract:The process control for reproducibility, uniformity, and achievement of desired structures for Carbon black generated in thermal plasma devices is studied in this paper through modeling, and correlated with experimental results. A numerical simulation of the flow and energy fields, stream function lines and the quench rates of the plasma gas in a conical shape reactor at different pressures was made. An argon plasma is used with highly diluted methane (0.6–7%) as the Carbon precursor. The quench rates were studied in order to observe the flow development and hence the thermal history of particle nucleation. Three pressure cases of 20.7, 55.2 and 101.3 kPa and two plasma powers cases of 10 and 20 kW were studied. The modeling results enabled Carbon nanoflakes production in the experimental tests performed on an inductively coupled thermal plasma system. Results indicate a robust process control enabling very little particle morphology variation over this wide range of reactor pressure values and varying plasma power, and a very high reproducibility of the particle morphologies obtained.