scholarly journals Cholate Adsorption Behavior at Carbon Electrode Interface and Its Promotional Effect in Laccase Direct Bioelectrocatalysis

2018 ◽  
Vol 2 (3) ◽  
pp. 33
Author(s):  
Masato Tominaga ◽  
Motofumi Tsutsui ◽  
Takuya Takatori
Keyword(s):  
Indium Tin Oxide ◽  
Electrode Materials ◽  
Catalytic Reduction ◽  
Pyrolytic Graphite ◽  
Sodium Cholate ◽  
Carbon Surface ◽  
Promotional Effect ◽  
Defect Sites ◽  
Electrode Interface ◽  
Walled Carbon Nanotubes

Fast electron transfer between laccase (Lac) and single-walled carbon nanotubes (SWCNTs) can be achieved at a cholate-modified SWCNT interface. Furthermore, the catalytic reduction of O2 starts at a high potential, close to the equilibrium redox potential of the O2/H2O couple. A sodium cholate (SC)-modified electrode interface provides suitable conditions for Lac direct bioelectrocatalysis. In the present study, the SC promotional effect in Lac direct bioelectrocatalysis was investigated using various types of electrode materials. The fully hydrophilic surface of indium tin oxide and an Au electrode surface did not show a SC promotional effect, because SC did not bind to these surfaces. A carbon surface with a large number of defects was unsuitable for SC binding because of hydrophilic functional groups at the defect sites. Carbon surfaces with few defects, for example, basal-plane highly oriented pyrolytic graphite (HOPG), gave a SC promotional effect.

Scattering of Low-Energy (5-12 eV) C2D4•+ Ions from Room-Temperature Carbon Surfaces

2008 ◽  
Vol 73 (6-7) ◽  
pp. 755-770 ◽  
Author(s):  
Andriy Pysanenko ◽  
Ján Žabka ◽  
Zdeněk Herman
Keyword(s):  
Survival Probability ◽  
Room Temperature ◽  
Incident Angle ◽  
Pyrolytic Graphite ◽  
Carbon Surface ◽  
Translational Energy ◽  
Energy Distributions ◽  
Surface Mass ◽  
Fragment Ions ◽  
Product Ions

The scattering of the hydrocarbon radical cation C2D4•+ from room-temperature carbon (highly oriented pyrolytic graphite, HOPG) surface was investigated at low incident energies of 6-12 eV. Mass spectra, angular and translational energy distributions of product ions were measured. From these data, information on processes at surfaces, absolute ion survival probability, and kinematics of the collision was obtained. The projectile ion showed both inelastic, dissociative and reactive scattering, namely the occurrence of H-atom transfer reaction with hydrocarbons present on the room-temperature carbon surface. The absolute survival probability of the ions for the incident angle of 30° (with respect to the surface) decreased from about 1.0% (16 eV) towards zero at incident energies below 10 eV. Estimation of the effective surface mass involved in the collision process led to m(S)eff of about 57 a.m.u. for inelastic non-dissociative collisions of C2D4•+ and of about 115 a.m.u. for fragment ions (C2D3+, C2D2•+) and ions formed in reactive surface collisions (C2D4H+, C2D2H+, contributions to C2D3+ and C2D2•+). This suggested a rather complex interaction between the projectile ion and the hydrocarbon-covered surface during the collision.

scholarly journals A Facile and Efficient Bromination of Multi-Walled Carbon Nanotubes

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3161
Author(s):  
Sandra Zarska ◽  
Damian Kulawik ◽  
Volodymyr Pavlyuk ◽  
Piotr Tomasik ◽  
Alicja Bachmatiuk ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Room Temperature ◽  
Covalent Attachment ◽  
Closed Vessel ◽  
Dangling Bonds ◽  
Magnetic Stirrer ◽  
Defect Sites ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Covalently Bound

The bromination of multi-walled carbon nanotubes (MWCNT) was performed with vapor bromine in a closed vessel, and they were subjected to intensive stirring with a magnetic stirrer for up to 14 days. The efficiency of bromination was compared depending upon duration. The structure and surface of the crude and purified products were characterized by detailed physicochemical analyses, such as SEM/EDS, TEM, XRD, TGA, Raman, and XPS spectroscopies. The studies confirmed the presence of bromine covalently bound with nanotubes as well as the formation of inclusion MWCNT–Br2 complexes. It was confirmed that Br2 molecules are absorbed on the surface of nanotubes (forming the CNT-Br2 complex), while they can dissociate close to dangling bonds at CNT defect sites with the formation of covalent C−Br bonds. Thus, any covalent attachment of bromine to the graphitic surface achieved around room temperature is likely related to the defects in the MWCNTs. The best results, i.e., the highest amount of attached Br2, were obtained for brominated nanotubes brominated for 10 days, with the content of covalently bound bromine being 0.68 at% (by XPS).

Electrospinning to Prepare Nanostructured Photocatalysts and Photoelectrodes

2018 ◽  
Vol MA2018-01 (31) ◽  
pp. 1905-1905
Author(s):  
Marcus Einert ◽  
André Bloesser ◽  
Roland Marschall
Keyword(s):  
Charge Carrier ◽  
Metal Oxide ◽  
Water Splitting ◽  
Indium Tin Oxide ◽  
Layered Perovskite ◽  
Fast Method ◽  
Photoelectrochemical Performance ◽  
Electrospinning Technique ◽  
Solar Water Splitting ◽  
Defect Sites

Electrospinning is a well-known, simple and fast method to prepare polymer fibers with diameters of 100-500 nm and lengths up to several micrometers.[1] Since for many semiconductor materials the charge carrier diffusion length is a critical parameter restricting photocatalytic or photoelectrochemical performance, we use the electrospinning approach to prepare nanostructured metal oxide nanofibers.[2] Directly after electrospinning, such nanofibers still contain spinning polymer, after calcination crystalline metal oxide nanofibers with diameter of 100-200 nm can be prepared.[3] Using the electrospinning technique, it is also possible to prepare fibrous photoelectrodes directly onto conducting substrates in a one step process.[4,5] Nanofibers of the (111)-layered perovskite materials Ba5Ta4O15 are built up from small single crystals, and are able to generate hydrogen without any co-catalyst in photocatalytic reformation of methanol. After photodeposition of Rh-Cr2O3 co-catalysts, the nanofibers show better activity in overall water splitting compared to sol–gel-derived powders.[3] Hollow a-Fe2O3 nanofibers and core–shell-like a-Fe2O3/indium-tin oxide (ITO) nanofiber composites were utilized as a photoanode for solar water splitting, the latter showing a doubled photocurrent compared to the hollow fiber photoanodes. This can be most likely be attributed to fast interfacial charge carrier exchange between the highly conductive ITO nanoparticles and a-Fe2O3, thus inhibiting the recombination of the electron–hole pairs in the semiconductor by spatial separation.[4] CuO photocathodes were directly prepared via electrospinning onto FTO, and calcination studies were performed to systematically characterize their crystallographic and structural evolution.[5] The higher the annealing temperature, the more developed are the crystalline domains of the nanofibers, which results in better conductivity and less defect sites serving as trap states for the photo-excited charge carriers. Hence, the CuO nanofiber photocathodes annealed at 800 °C showed the highest photoresponse and stability. No decrease in the photocurrent density after prolonged operation in aqueous electrolyte was observed. References [1] A. Greiner, J. H. Wendorff, Angew. Chem. Int. Ed. 2007, 46, 5670-5703. [2] R. Ostermann, J. Cravillon, C. Weidmann, M. Wiebcke, B. M. Smarsly, Chem. Commun. 2011, 47, 442-444. [3] N. C. Hildebrandt, J. Soldat, R. Marschall, Small 2015, 11, 2051–2057. [4] M. Einert, R. Ostermann, T. Weller, S. Zellmer, G. Garnweitner, B. M. Smarsly, R. Marschall, J. Mater. Chem. A 2016, 4, 18444-18456. [5] M. Einert, T. Weller, T. Leichtweiss, B. M. Smarsly, R. Marschall, Chem. Photo. Chem. 2017, 1, 326-340. Figure 1

SEMICONDUCTING CARBON NANOTUBE PHOTOVOLTAIC PHOTODETECTORS

2011 ◽  
Vol 20 (03) ◽  
pp. 687-695 ◽  
Author(s):  
DOMINICK J. BINDL ◽  
MICHAEL S. ARNOLD
Keyword(s):  
Carbon Nanotubes ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Near Infrared ◽  
Series Resistance ◽  
Single Walled Carbon Nanotubes ◽  
Infrared Band ◽  
Device Architecture ◽  
Heterojunction Device ◽  
Walled Carbon Nanotubes

A photovoltaic photodetector harnessing near infrared band gap absorption by thin films of post-synthetically sorted semiconducting single walled carbon nanotubes ( s -SWCNTs) is described. Peak specific detectivity of 6×1011 Jones at -0.1 V bias at 1210 nm is achieved using a heterojunction device architecture: indium tin oxide/ ca. 5 nm s -SWCNT / 120 nm C60 / 10 nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) / Ag. The photodiodes are characterized by a series resistance of 2.9 Ω cm2 and a rectification ratio of 104 at ±1V. These results are expected to guide the exploration of new classes of solution-processable, mechanically flexible, integrable, thin film photovoltaic photodetectors with tunable sensitivity in the visible and infrared spectra based on semiconducting carbon nanotubes.

scholarly journals Electroless Deposition of Cu-SWCNT Composites

2019 ◽  
Vol 5 (4) ◽  
pp. 61 ◽  
Author(s):  
Raja ◽  
Esquenazi ◽  
Jones ◽  
Li ◽  
Brinson ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electroless Deposition ◽  
Reaction Times ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
Copper Surfaces ◽  
X Ray ◽  
Dispersing Agent ◽  
Defect Sites ◽  
Walled Carbon Nanotubes

In this work, as-received HiPCO single walled carbon nanotubes (SWCNTs) are incorporated in a controllable manner at various concentrations into Cu-SWCNT composites via electroless plating, by varying the related reaction times, with polyethylene glycol (PEG) used as a dispersing agent. The resultant samples were analyzed using scanning electron microscopy (SEM) for morphology assessment, energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) for elemental analysis, X-ray diffraction (XRD) for the assessment of crystal phase identification, and Raman spectroscopy for the confirmation of the presence of the incorporated SWCNTs. The Cu-SWCNT composites were found to contain carbon, catalytic iron (associated with the raw, as-received SWCNTs), oxygen, and copper; the latter was found to be inversely proportional to carbon and iron contents. The oxygen (associated with both the SWCNT defect sites and oxidized copper surfaces) remained more or less constant regardless of the proportion of SWCNTs in the composites. The Raman IG:ID ratio remains within the experimental error constant, indicating that the electroless deposition does not have a deleterious effect on the SWCNTs. At short deposition times, SEM revealed a relatively dense structure comprising a distinctive fibrous morphology, suggestive of an underlying SWCNT substrate coated with copper; however, with increasing deposition, a more porous morphology is observed. The size of the granular particles increases up until 10 min of reaction, after which time it remains unchanged.

scholarly journals Optimizing the neuron-electrode interface for chronic bioelectronic interfacing

2020 ◽  
Vol 49 (1) ◽  
pp. E7
Author(s):  
Conor Keogh
Keyword(s):  
Electrode Materials ◽  
Neurological Diseases ◽  
Tissue Reaction ◽  
Biological Interactions ◽  
Implanted Electrodes ◽  
Tissue Integration ◽  
Closed Loop Systems ◽  
Electrode Interface ◽  
Neural Interfacing

Engineering approaches have vast potential to improve the treatment of disease. Brain-machine interfaces have become a well-established means of treating some otherwise medically refractory neurological diseases, and they have shown promise in many more areas. More widespread use of implanted stimulating and recording electrodes for long-term intervention is, however, limited by the difficulty in maintaining a stable interface between implanted electrodes and the local tissue for reliable recording and stimulation.This loss of performance at the neuron-electrode interface is due to a combination of inflammation and glial scar formation in response to the implanted material, as well as electrical factors contributing to a reduction in function over time. An increasing understanding of the factors at play at the neural interface has led to greater focus on the optimization of this neuron-electrode interface in order to maintain long-term implant viability.A wide variety of approaches to improving device interfacing have emerged, targeting the mechanical, electrical, and biological interactions between implanted electrodes and the neural tissue. These approaches are aimed at reducing the initial trauma and long-term tissue reaction through device coatings, optimization of mechanical characteristics for maximal biocompatibility, and implantation techniques. Improved electrode features, optimized stimulation parameters, and novel electrode materials further aim to stabilize the electrical interface, while the integration of biological interventions to reduce inflammation and improve tissue integration has also shown promise.Optimization of the neuron-electrode interface allows the use of long-term, high-resolution stimulation and recording, opening the door to responsive closed-loop systems with highly selective modulation. These new approaches and technologies offer a broad range of options for neural interfacing, representing the possibility of developing specific implant technologies tailor-made to a given task, allowing truly personalized, optimized implant technology for chronic neural interfacing.

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