Contiguous Petal-like Carbon Nanosheet Outgrowths from Graphite Fibers by Plasma CVD

Carbon nanomaterials are advantageous as electrodes for neurotransmitter detection, but the difficulty of nanomaterials deposition on electrode substrates limits the reproducibility and future applications. In this study, we used plasma enhanced chemical vapor deposition (PECVD) to directly grow a thin layer of carbon nanospikes (CNS) on cylindrical metal substrates. No catalyst is required and the CNS surface coverage is uniform over the cylindrical metal substrate. The CNS growth was characterized on several metallic substrates including tantalum, niobium, palladium, and nickel wires. Using fast-scan cyclic voltammetry (FSCV), bare metal wires could not detect 1 μM dopamine while carbon nanospike coated wires could. The highest sensitivity and optimized S/N ratio was recorded from carbon nanospike-tantalum (CNS-Ta) microwires grown for 7.5 minutes, which had a LOD of 8 ± 2 nM for dopamine with FSCV. CNS-Ta microelectrodes were more reversible and had a smaller ΔEp for dopamine than carbon-fiber microelectrodes, suggesting faster electron transfer kinetics. The kinetics of dopamine redox were adsorption controlled at CNS-Ta microelectrodes and repeated electrochemical measurements displayed stability for up to ten hours in vitro and over a ten day period as well. The oxidation potential was significantly different for ascorbic acid and uric acid compared to dopamine. Growing carbon nanospikes on metal wires is a promising method to produce uniformly-coated, carbon nanostructured cylindrical microelectrodes for sensitive dopamine detection.

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“…However, the CNS growth on metal substrates is relatively edge-plane rich compared to the multilayer graphene sheets reported previously. 25 …”

Section: Resultsmentioning

confidence: 99%

Carbon nanospikes grown on metal wires as microelectrode sensors for dopamine

Zestos

Yang

Jacobs

et al. 2015

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“…The sample size was approximately 10 mm × 5 mm in area with a thickness of 2 mm. A catalyst-free petal growth process was performed in a SEKI AX5200S microwave plasma chemical vapor deposition system utilizing H2 and CH4 feed gases in conditions described previously (Bhuvana et al, 2010;McMullen, 2010;Vander Laan, 2011). The sample was placed atop a 2.5 cm ceramic post in order to promote coupling of the plasma to the sample.…”

Section: Experimental Methods Graphitic and C X (Bn) Petal Fabricationmentioning

confidence: 99%

Work Function Characterization of Potassium-Intercalated, Boron Nitride Doped Graphitic Petals

et al. 2017

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This paper reports on characterization techniques for electron emission from potassiumintercalated boron nitride-modified graphitic petals (GPs). Carbon-based materials offer potentially good performance in electron emission applications owing to high thermal stability and a wide range of nanostructures that increase emission current via field enhancement. Furthermore, potassium adsorption and intercalation of carbon-based nanoscale emitters decreases work functions from approximately 4.6 eV to as low as 2.0 eV. In this study, boron nitride modifications of GPs were performed. Hexagonal boron nitride is a planar structure akin to graphene and has demonstrated useful chemical and electrical properties when embedded in graphitic layers. Photoemission induced by simulated solar excitation was employed to characterize the emitter electron energy distributions, and changes in the electron emission characteristics with respect to temperature identified annealing temperature limits. After several heating cycles, a single stable emission peak with work function of 2.8 eV was present for the intercalated GP sample up to 1,000 K. Up to 600 K, the potassium-intercalated boron nitride modified sample exhibited improved retention of potassium in the form of multiple emission peaks (1.8, 2.5, and 3.3 eV) resulting in a large net electron emission relative to the unmodified graphitic sample. However, upon further heating to 1,000 K, the unmodified GP sample demonstrated better stability and higher emission current than the boron nitride modified sample. Both samples deintercalated above 1,000 K.

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“…Growth of petals does not require any supplemental heating. The growth substrate couples strongly with the plasma and which is sufficient to locally heat the substrate up to about 1000 1C [24,25,19,26]. Fig.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

“…On the other hand, two-dimensional carbon nanopetals can be synthesized under growth conditions similar to those of CNTs [19]. Unlike graphite intercalated compounds such as exfoliated graphene, carbon nano-petals are made without the use of impurity metals, atomically thin, and free-standing.…”

Section: Introductionmentioning

confidence: 99%