Catalytical growth of carbon nanotubes/fibers from nanocatalysts prepared by laser pulverization of nickel sulfate

Abstract

Dispersed nickel sulfate ͑NiSO 4 ͒ microclusters on Si substrates were fragmented by pulsed excimer laser irradiation to serve as catalysts for carbon nanotube/nanofiber ͑CNT/CNF͒ growth. At proper fluences, NiSO 4 clusters were pulverized into nanoparticles. The sizes of clusters/nanoparticles were found to be dependent on laser fluence and laser pulse number. By increasing the laser fluence from 100 to 300 mJ/ cm 2 , the size of disintegrated particles decreased drastically from several micrometers to several nanometers. It was found that laser-induced disintegration of as-dispersed NiSO 4 clusters was mainly due to physical fragmentation by transient thermal expansion/ contraction. Thermal melting of nanoparticles in a multipulse regime was also suggested. Hot-filament chemical vapor deposition ͑HFCVD͒ was used for growth of CNTs from the pulsed-laser treated catalysts. For samples irradiated at 100 and 200 mJ/ cm 2 , CNFs were dominant products. These CNFs grew radially out of big NiSO 4 clusters, forming dendritic CNF bunches. For samples irradiated at 300 mJ/ cm 2 , dense multiwalled carbon nanotubes ͑MWCNFs͒ with uniform diameters were obtained. It is suggested that elemental Ni was formed through thermal decomposition of NiSO 4 clusters/nanoparticles during HFCVD. The size and the shape of the Ni aggregation, which were determined by the initial size of NiSO 4 clusters/nanoparticles, might affect the preference in the synthesis of CNTs or CNFs.

DNA-Templated Nickel Nanostructures and Protein Assemblies

“…This image demonstrates that our method for fabrication of nickel nanostructures does not cleave or otherwise damage the DNA template, allowing long DNA molecules to be plated with nickel, without loss of their structural integrity. Importantly, linear or two-dimensional assemblies of DNA-templated nickel nanoparticles could form ordered nanoscale magnetic storage units 9 or serve as catalytic seeds for the nanoscale patterned growth of materials such as carbon nanotubes. ,

1 Tapping mode AFM height images of the synthesis of DNA-templated nickel. (A) Surface-aligned λ DNA molecules; Z scale is 3 nm.

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Structurally integrated 3D carbon tube grid–based high-performance filter capacitor

“…To increase the specific surface area and further enhance C A , the 3D-CTs can be modified, as exemplified by filling with much-smaller-diameter CNTs within the vertical and lateral CTs (3D-CNT@CT) by means of the Ni catalyst–assisted CVD method (Fig. 1A) ( 22 ), or surface-treated with KMnO 4 (3D-RCT, i.e., 3D-CT with a rough surface) (fig. S3) ( 23 ).…”