Nanocarbon Electrochemistry and Interface

Resume : Carbon nanostructures are difficult to be synthesized with precisely controlled shapes. A facet-selective-catalytic process was thus proposed to prepare polymer-liked carbon nanostructures with different shapes, covering straight carbon nanofiber, carbon nano Y-junction, carbon nano-hexapus, and carbon nano-octopus. A thermal chemical vapour deposition process was applied to synthesize these multi-branched carbon nanostructures at temperatures lower than 350 oC. Cu nanoparticles were utilized as the catalyst and acetylene as the reaction gas. The growth of those multi-branched nanostructures was realized via the selective growth of polymer-like sheets on certain indexed facets of Cu catalyst. The Vapor-Facet-Solid (VFS) mechanism, a new growth mode, has been proposed to interpret such a growth in the steps of formation, diffusion and coupling of carbon contained oligomers, as well as their final precipitation to form nanostructures on the selective Cu facets.

Resume : Carbon nano-onions(CNOs) were fabricated by electric arc-discharge method with nickel powder as catalyst. The morphology and structure of the obtained samples were characterized by field-emission scanning electron microscope, transmission electron microscopy, Raman spectrum and X-ray diffraction. The results of cyclic voltammograms shows that the current peak value is related to the loading of CNOs on electrode surface. With the loading of CNOs the peak current value increases. Thus, it is estimated that the CNOs could provide accessible external surface area for ion adsorption.

Resume : A simple but sensitive electrochemical method was proposed for simultaneous determination of paracetamol (PCT) and diclofenac (DCF) based on poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene (GR). Although electrochemical impedance analysis revealed that both GR and PDDA-GR modification could obviously facilitate the electron transfer on glassy carbon electrode (GCE), the electrochemical responses of PCT and DCF mixture on two modified electrodes were different. On GR modified electrode, the currents were enhanced while the oxidation peak difference between PCT and DCF was reduced, which led to a difficulty in the simultaneous determination of two drugs. By contrast, PDDA-GR greatly increased the electrochemical currents of both analytes while provided well-separated peak potentials. Thus, the simultaneous determination of PCT and DCF by differential pulse voltammetry was investigated on PDDA-GR. The applicability of the proposed method was verified when it was applied in determination of PCT and DCF in pharmaceuticals and lake water. Good reproducibility and high stability were also achieved.

Resume : Graphene nano platelets (GNPs) or nano graphene platelets (NGPs) are stacks of graphene sheets with an overall thickness ranging from an average of about 5 to about 25 nm. Most of them have "platelet" morphology with a diameter of 0.5 to 25 μm. Their aspect ratios are high and can be range into the thousands. They show similar thermal and mechanical properties to CNTs but their surface areas or aspect ratios are higher. They have therefore different properstes from single or few (up to 5) layered grapheme. They have been more widely applied for various applications, such as electrochemical detections and biochemical sensing. However the properties are expected to be different from. In this presentation, we will show electrochemical deposition of gold-palladium nanoparticles (AuPd NPs) on graphene-nano-platelets (GNPs) and their application for electrocatalytic oxidation of hydrazine. The deposition was conducted using a potentiostatic mode in a mixture of HAuCl4 and H2PdCl4. This composite was characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). AuPd NPs are well-dispersed on the GNP surface with particle diameter of about 30-60 nm. Moreover, they are alloyed and have porous structures. Their application was focused on the voltammetric detection of hydrazine. The chronoamperometric (CA) and cyclic voltammetric (CV) curves proved the catalytic ability of AuPd NPs towards the electrochemical oxidation of hydrazine. Under the optimized conditions, the oxidation current is linear with the concentration of hydrazine in the range of 0.02 - 166.6 μM with a sensitivity of 62.2 μA mM-1 and a detection limit of 5 nM. These results will be compared and discussed as well with those published in literature.

Resume : A novel ionic liquid, 3-{3-[(2-Aminoethyl)amino]propyl}-1-vinylimidazole bromide, was synthesized and used as a functional monomer for the fabrication of a molecularly imprinted sensing interface for myoglobin. Using the as-prepared ionic liquid as functional monomer, myoglobin from skeletal muscle as template, N,N’-Methylenebisacrylamide as crossing linker, and a redox system containing ammonium persulfate and N,N,N’,N’-Tetramethylethylenediamine as initiator, a myoglobin imprinted film was in-suit fabricated on a multiwall carbon nanotubes modified glassy carbon electrode surface at room temperature. Based on the electroactive probes, K3[Fe(CN)6]/K4[Fe(CN)6], the electrochemical sensing performances of the molecularly imprinted film electrode were investigated. The results demonstrated that the molecularly imprinted film possesses good selectivity and high sensitivity. The peak current variation is linearly related to the myoglobin concentration in the range from 6.0 10-8 to 6.0 10-6 mol L-1. The detection limit was calculated to be 9.68 10-9 mol L-1(S/N=3). Acknowledgments The authors gratefully acknowledge the financial supports from National Natural Science Foundation of China (No.21275166), China Scholarship Council (No. 201307780006), and the Natural Science Foundation of Hubei Province (No. 2015CFA092).

Resume : Recently, the development of nanoprobe signal amplification based ultrasensitive electrochemical immunoassay methods has shown a promising perspective in the clinical diagnosis field. Compared with the conventionally used enzymatic signal tags, gold nanoparticle (Au NP) has gained more and more attentions as a ideal nonenzymatic tags due to unique properties. In this work, we sucessfully designed a novel Au NP-functionalized graphene nanoprobe for the signal tracing of immunoassay and thus developing a new ultrasensitive electrochemcial immunoassay method. The nanoprobe was prepared through the in situ deposition of Au NPs on the surface of graphene oxide (GO) which was followed by the hydrothermal reduction to form a reduced graphene oxide (rGO)-Au NPs nanocomposite. After the antibody functionalization, the obtained rGO-Au NPs based nanoprobe was used for the signal tracing for the sandiwich immunoassay at a carbon nanotubes-modified electrode based immunosensor. The high-content Au NP tags on the quantitatively captured rGO-Au NPs nanoprobes via immunoreaction could be coveniently measurment through electrochemical stripping analysis to produce sensitive electrochemcial signal for quantitativel immunoassay. Due to the signal amplificaiton of the nanoprobe and the electron transfer acceleration of the carbon nanotubes modified on the electrode surface, ultrahigh sensitivity for the protein analyte measurement was achieved. As this gold nanoprobe is simple and cheap for preparation, and the Au NPs stripping analysis is convenient for manipulation, this nanoprobe and the developed immunoassay method provide great potentials for practical applications.

Resume : Hydrogen sulfide (H2S), a kind of poisonous gas which can be found in forms of dissolved H2S, HS- and S2- in aqueous medium, is demonstrated to be a potential food preservation gas for prolonging postharvest shelf life of fruits [1] and vegetables [2]. It is necessary to develop fast and effective detection of these forms of H2S (classified as sulfides) that possibly remained in food in case of harm. In this work, we presented a new approach for rapid detection of sulfide using a glassy carbon electrode (GCE) modified with alizarin (Az) and reduced graphene oxide (rGO) nanosheets. The fabricate Az-rGO/GCE sensor exhibited a notable electrocatalytic activity to sulfide oxidation. Amperometric studies showed that the steady currents were related linearly to the concentrations of sulfide in the range of 0.05 to 2.25 mM. The proposed method was successfully applied in sulfide determination of hydrogen sulfide pretreated fruits, and the method was verified with recovery studies with recovery values of 91%-121%. Fig. 1. Amperometric responds to the different concentrations of sulfide on Az-rGO/GCE at applied potential of +0.225 V (vs. Ag/AgCl). Inset: TEM image of reduced graphene oxide. Reference [1] L.Y. Hu, S.L. Hu, J. Wu, Y.H. Li, et al. J. Agric. Food Chem. 2012, 60, 8684−8693 [2] S.P. Li, K.D. Hu, L.Y. Hu, et al. J. Agric. Food Chem. 2014, 62, 1119−1129

Resume : Boron-doped diamond is a promising electrode and electrode support for electrochemical capacitor applications. In this presentation we will show the applications of diamond for electrical double layer capacitor and pseudosupercapacitors. The capacitance of diamond based electrical double layer capacitor only reduced 5% even after 1 000 charge-discharge cycles in 1.0 M sodium sulphate solution at a scan rate of 100 mV/s. To improve the performance of diamond based capacitors, large surface areas of diamond electrodes (for electric double layer capacitors) or diamond based composite films (for pseudosupercapacitor) are required. Carbon nanofibers on diamond electrode surface will be shown for electric double layer capacitor application as well as manganese dioxide coated diamond electrode for pseudosupercapacitor application. Carbon nanofibers were grown using thermal chemical vapour deposition method with aid of copper nanoparticles as the catalysts. Manganese dioxide was electrochemically deposited on diamond electrode at a constant potential. The charge consumed during the deposition was applied to control the amount and the thickness of manganese dioxide on the diamond electrode. The performance of two capacitors will be shown in details. The comparison of carbon nanofibers based double layer capacitor with manganese dioxide based pseudosupercapacitor as well as with those related capacitors shown in literature will be conducted. More regarding the life-time of these capacitors, power and energy densities, etc. will be discussed as well.

Resume : 1,3-di(4-amino-1-pyridinium) propane tetrafluoroborate ionic liquid (DAPPT) was successfully synthesized and characterized by NMR, HPLC-MS. DAPPT was used as a modifier to functionalize reduced graphene oxide (rGO) nanosheets. DAPPT-rGO nanosheets and tyrosinase (Tyr) were thoroughly mixed, and coated to glassy carbon electrode to fabricate a Tyr-DAPPT-rGO/GCE modified electrode, which would be a promising biosensor for phenolic compounds. The as-prepared modified electrodes were characterized with scanning electronic microscopy and electrochemical impedance spectroscopy. Using bisphenol A (BPA) as a target molecule, a number of key factors including the volume of Tyr-DAPPT-rGO solution, the applied potential, pH values and temperature that influence the analytical performance of the biosensor were investigated. The biosensor gave a linear response on the BPA concentration in the range of 1.0 × 10-9 ~ 3.8 × 10-5 molL-1. The detection limits were estimated to be 3.5 × 10-10 molL-1 (S/N=3). Practical application of the biosensor was demonstrated by the determination of BPA leaching from commercial plastic drinking bottles. Results indicated that Gr-DAPPT based interface would be a promising platform for biosensor preparation.

Resume : Active carbon derived from lignite was activated by ZnCl2, which showed high double capacity performance in a three electrode system. The result of SEM and BET refered that the material activated with ZnCl2 has more meso-pore than that activated with NaOH. Electrochemical investigations indicate that the activated carbon shows the maximum specific capacitance of 207.5Fg−1 in 6M KOH electrolytes at 0.5A g−1, respectively. The capacitor use activated carbon as electrode presents good cycle stability during 3,000 cycles at a fair current density of 5 A g−1 and capacity rate can reach 91%, because of its specific surface area of 1024 m2 / g.

Resume : Vertically oriented TiO2 nanotube arrays (TNTAs) were conformally coatedwith an ultrathin nitrogen-doped (N-doped) carbon filmvia the carbonization of a polyimide filmdeposited bymolecular layer deposition and simultaneously hydrogenated, thereby creating a core/shell nanostructure with a precisely controllable shell thickness. The core/shell nanostructure provides a larger heterojunction interface to substantially reduce the recombination of photogenerated electron–hole pairs, and hydrogenation enhances solar absorption of TNTAs. In addition, the N-doped carbon film coating acts as a high catalytic active surface for oxygen evolution reaction, as well as a protective film to prevent hydrogen-treated TiO2 nanotube oxidation by electrolyte or air. As a result, the N-doped carbon film coated TNTAs displayed remarkably improved photocurrent and photostability. The TNTAs with a N-doped carbon film of
1 nm produces a current density of 3.6 mA cm2 at 0 V vs. Ag/AgCl under the illumination of AM 1.5G (100 mW cm2 ), which represents one of the highest values achieved with modified TNTAs. Therefore, we propose that ultrathin N-doped carbon film coating on materials is a viable approach to enhance their PEC water splitting performance.