Morphology--composition correlations in carbon nanotubes synthesised with nitrogen and phosphorus containing precursors.

We have correlated the elemental composition with the structure of multi-wall carbon nanotubes synthesised with nitrogen and phosphorus containing precursors and identified two chemically distinct dominant morphologies. The first type are cone-structured tubes and the second are nanotubes with fewer walls which can accommodate N2 gas along their inner channel and contain up to ten times more nitrogen than the cone-structured nanotubes. Phosphorus was present in the catalyst particles but was not detected within the walls of either type of nanotube. Elemental analysis combined with in situ electrical measurements has allowed us to monitor the evolution of the doped nanotubes when current is passed. The N2 gas becomes bonded immediately when current flows and the gas-containing nanotubes restructure more easily than the cone-structured ones. Since the inclusion of heteroatoms in multi-wall carbon nanotubes is generally inhomogeneous, understanding the distribution of elements across the sample is an important step towards the optimization of devices including gas sensors and components in electrical applications.

Dynamic strain in gold nanoparticle supported graphene induced by focused laser irradiation.

Graphene on noble-metal nanostructures constitutes an attractive nanocomposite with possible applications in sensors or energy conversion. In this work we study the properties of hybrid graphene/gold nanoparticle structures by Raman spectroscopy and scanning probe methods. The nanoparticles (NPs) were prepared by local annealing of gold thin films using a focused laser beam. The method resulted in a patterned surface, with NPs formed at arbitrarily chosen microscale areas. Graphene grown by chemical vapour deposition was transferred onto the prepared, closely spaced gold NPs. While we found that successive higher intensity (6 mW) laser irradiation increased gradually the doping and the defect concentration in SiO2 supported graphene, the same irradiation procedure did not induce such irreversible effects in the graphene supported by gold NPs. Moreover, the laser irradiation induced a dynamic hydrostatic strain in the graphene on Au NPs, which turned out to be completely reversible. These results can have implications in the development of graphene/plasmonic nanoparticle based high temperature sensors operating in dynamic regimes.

Time dependent decomposition of ammonia borane for the controlled production of 2D hexagonal boron nitride.

Ammonia borane (AB) is among the most promising precursors for the large-scale synthesis of hexagonal boron nitride (h-BN) by chemical vapour deposition (CVD). Its non-toxic and non-flammable properties make AB particularly attractive for industry. AB decomposition under CVD conditions, however, is complex and hence has hindered tailored h-BN production and its exploitation. To overcome this challenge, we report in-depth decomposition studies of AB under industrially safe growth conditions. In situ mass spectrometry revealed a time and temperature-dependent release of a plethora of NxBy-containing species and, as a result, significant changes of the N:B ratio during h-BN synthesis. Such fluctuations strongly influence the formation and morphology of 2D h-BN. By means of in situ gas monitoring and regulating the precursor temperature over time we achieve uniform release of volatile chemical species over many hours for the first time, paving the way towards the controlled, industrially viable production of h-BN.

Publisher Correction: Time dependent decomposition of ammonia borane for the controlled production of 2D hexagonal boron nitride.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Rapid epitaxy-free graphene synthesis on silicidated polycrystalline platinum.

Large-area synthesis of high-quality graphene by chemical vapour deposition on metallic substrates requires polishing or substrate grain enlargement followed by a lengthy growth period. Here we demonstrate a novel substrate processing method for facile synthesis of mm-sized, single-crystal graphene by coating polycrystalline platinum foils with a silicon-containing film. The film reacts with platinum on heating, resulting in the formation of a liquid platinum silicide layer that screens the platinum lattice and fills topographic defects. This reduces the dependence on the surface properties of the catalytic substrate, improving the crystallinity, uniformity and size of graphene domains. At elevated temperatures growth rates of more than an order of magnitude higher (120 µm min(-1)) than typically reported are achieved, allowing savings in costs for consumable materials, energy and time. This generic technique paves the way for using a whole new range of eutectic substrates for the large-area synthesis of 2D materials.

WS2 2D nanosheets in 3D nanoflowers.

In this work it has been established that 3D nanoflowers of WS2 synthesised by chemical vapour deposition are composed of few layer WS2 along the edges of the petals. An experimental study in order to understand the evolution of these nanostructures shows the nucleation and growth along with the compositional changes they undergo.

In situ engineering of NanoBud geometries.

NanoBuds exist in a variety of stable structures. Our studies show that engineering NanoBud geometries is indeed possible and we visualise the transformation of one Nanobud geometry to another using in situ aberration corrected imaging techniques. Such NanoBuds are precursors for generating nanotube junctions which could be used in composite and electronic applications.

Controlled growth of Ni nanocrystals on SrTiO(3) and their application in the catalytic synthesis of carbon nanotubes.

Truncated pyramid-shaped Ni nanocrystals were epitaxially grown on SrTiO(3)(001) surfaces and characterised by scanning tunneling microscopy (STM). These nanocrystals were shown to be catalytically active for the synthesis of carbon nanotubes (CNTs). The narrow size distribution of the Ni nanocrystals results in a similar narrow distribution of CNT diameters.

Facile, fast, and inexpensive synthesis of monodisperse amorphous nickel-phosphide nanoparticles of predefined size.

Monodisperse, size-controlled Ni-P nanoparticles were synthesised in a single step process using triphenyl-phosphane (TPP), oleylamine (OA), and Ni(II)acetyl-acetonate. The nanoparticles were amorphous, contained ~30 at% P and their size was controlled between 7-21 nm simply by varying the amount of TPP. They are catalytically active for tailored carbon nanotube growth.

Interconnecting carbon nanotubes with an inorganic metal complex.

Intermolecular carbon nanotube junctions were formed through amide linkage of amino functionalized multiwall carbon nanotubes and [Ru (dcbpy)(bpy)2](PF6)2, an inorganic metal complex. Nanotube interconnects were visualized using atomic force microscopy. Absorption and emission spectroscopy showed significant changes between starting products and the resulting ruthenium nanotube complex, indicative of successful chemical modification.