Morphological Control of Tapered and Multi‐Junctioned Carbon Tubular Structures

Bhimarasetti, Gopinath; Sunkara, Mahendra; Graham, Uschi M.; Davis, Brynmor J.; Suh, Changwon; Rajan, Krishna Prasad

doi:10.1002/adma.200305400

Cited by 28 publications

(24 citation statements)

References 21 publications

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“…The CMT synthesis procedure and the structure have been described in detail elsewhere. [28][29][30] Although the present technique of using trimethyl gallium is expensive, this process presents a route of using Ga as a catalyst in the presence of methyl radical species for the inexpensive large-area synthesis of CMTs. The SEM image in Figure 1a shows a large area of the as-synthesized CMTs that are several micrometers in length.…”

Section: Resultsmentioning

confidence: 99%

“…27 Later, thin-walled CMT synthesis with control over the conical angles and microtube diameters was demonstrated. 28,29 Another study showed that these CMTs can be synthesized during thermal decomposition of a Ga precursor. 30 Recently, Sn particles encapsulated in porous multichannel carbon microtubes have shown a capacity retention of ∼650 mAh g -1 after 140 cycles.…”

Section: Introductionmentioning

confidence: 99%

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Thin-Walled Carbon Microtubes as High-Capacity and High-Rate Anodes in Lithium-Ion Batteries

et al. 2010

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In this article, we present a large-area synthesis of carbon microtubes (CMTs) with internal diameters of ∼1.5 µm and wall thicknesses on the order of 50 nm and their lithium ion intercalation and deintercalation properties for the first time. The results show that CMTs exhibit a good capacity retention of 443 mAh g -1 after 20 cycles, higher than the theoretical capacity of graphite and ∼1.5 times higher than the capacity of multi-walled carbon nanotubes at similar conditions. The high capacity retention is attributed mostly to the presence of nanodomains of graphite in the thin walls of the microtubes providing multiple pathways for lithium ion intercalation and the open ends of the CMTs providing additional surface area for intercalation. The CMTs show good rate capability with a capacity retention of 135 mAh g -1 at a current density of 1.5 A g -1

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thin-Walled Carbon Microtubes as High-Capacity and High-Rate Anodes in Lithium-Ion Batteries

et al. 2010

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“…Based on the growth mechanism described in Figure 5, the conical angle of the evolving morphology can be related to the contact angle between gallium and the carbon wall by the following relationship. In our synthesis method, 13,14 we change the contact angle, , by varying the gas phase chemistry, allowing us to successfully control the conical angles of the carbon tubular structures. Under CH 4 /H 2 gas phase chemistries gallium does not wet carbon readily due to its high surface energy.…”

Section: (B) Carbon Microtubesmentioning

confidence: 99%

“…Recently, we reported a synthesis technique to synthesize carbon tubular structures with larger inner diameters, tunable morphologies and with no internal obstructions so as to enable micro/nanofluidic applications. 13,14 In this paper, we present the synthesis and applications of two new forms of graphite at the nanoscale: carbon nanopipettes and carbon microtubes with controllable morphologies. The synthesis methods and the corresponding growth mechanisms involved for both types of structures will be discussed.…”

Section: Introductionmentioning

confidence: 99%

Carbon nanopipettes and microtubes for electrochemical sensing and microfluidics

Mani

Bhimarasetti

Lowe

et al. 2004

Nanosensing: Materials and Devices

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We present the synthesis of two novel morphologies for carbon tubular structures: Nanopipettes and Micropipes. The synthesis procedures for both these structures are both unique and different from each other and the conventional methods used for carbon nanotubes.Carbon nanopipettes, open at both ends, are made up of a central nanotube (~10-20 nm) surrounded by helical sheets of graphite. Thus nanopipettes have an outer conical structure, with a base size of about a micron, that narrows down to about 10-20 nm at the tip. Due to their unique morphology, the outer walls of the nanopipettes continuously expose edge planes of graphite, giving a very stable and reversible electrochemical response for detecting neurological compounds such as dopamine. The synthesis of carbon nanopipettes is based on high temperature nucleation and growth of carbon nanotubes under conditions of hydrogen etching during growth.Carbon micropipes, on the other hand, are tubular structures whose internal diameters range from a few nanometers to a few microns with a constant wall thickness of 10-20 nm. In addition to tuning the internal diameters, the conical angles of these structures could also be changed during synthesis. Due to their larger inner diameters and thin walls, both the straight and conical micro-tubular structures are suitable for microfluidic devices such as throttle valves, micro-reactors, and distribution channels. The synthesis of carbon micro-tubular structures is based on the wetting behavior of gallium with carbon during growth. The contact angle between gallium and the carbon wall determines the conical angle of the structure. By varying the contact angle, one can alter the conical angles from 40 0 to -15 0 , and synthesize straight tubes using different N 2 /O 2 dosing compositions. An 'n-step' dosing sequence at various stages of growth resulted in 'n-staged' morphologies for carbon micro-tubular structures such as funnels, tube-on-cone, Yjunctions and dumbbells.

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“…These properties make gallium an important element for chemical vapor synthesis of nanomaterials [18].…”

Section: General Background On Galliummentioning

confidence: 99%

Near room temperature self-assembly of nanostructures by reaction of gallium with metal thin films.

Yazdanpanah¹,

Mehdi²

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Yazdanpanah, Mehdi M. 1975-, "Near room temperature self-assembly of nanostructures by reaction of gallium with metal thin films." (2006) Liquid gallium (Ga) spontaneously alloys with thin films of metals such as Ag, Au, Pt AI, and Cu at near or even below room temperature resulting in rapid self-assembly of nanostructures. In this dissertation, studies of the formation of these nanostructures are reported together with application of the processes towards device fabrication.Ag2Ga needles, CoGa3 rods, and G~Pt plates self-assemble at room temperature at the interface of Ga and thin films of Ag Co, and Pt. The Ag 2 Ga needles orient nearly vertical to the interface which suggests that an individual needle can be directed to grow in a desired direction by drawing a silver-coated surface from the Ga droplet. Needles from 25 nm to microns in diameter and up to 33 microns long were grown by this method.Needle-tipped cantilevers have been used to perform atomic force microscopy ( Networks of Au-Ga nanowires form when a liquid Ga drop spreads and reacts on 10-to 100-nm-thick Au thin film at temperatures between 310 °C and 400 °C. Au suspended nanowires were fabricated by etching these networks in HCI followed by anisotropic etching of the Si substrate. Suspended nanowires as long as 6 f..lm and as narrow as 35 nm diameters have been produced.Superporous Au and Pt thin films with feature size as small as 5 nm are formed after HCI etching of metal thin films that have been reacted with gallium. Superporous Pt formed on a set of microelectrodes was evaluated for electrochemical sensing. These electrodes showed a 6 fold improvement in its limit of detection for H202 over the nonporous Pt electrodes.Vll

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Morphological Control of Tapered and Multi‐Junctioned Carbon Tubular Structures

Cited by 28 publications

References 21 publications

Thin-Walled Carbon Microtubes as High-Capacity and High-Rate Anodes in Lithium-Ion Batteries

Thin-Walled Carbon Microtubes as High-Capacity and High-Rate Anodes in Lithium-Ion Batteries

Carbon nanopipettes and microtubes for electrochemical sensing and microfluidics

Near room temperature self-assembly of nanostructures by reaction of gallium with metal thin films.

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