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 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 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

WS22D nanosheets in 3D nanoflowers

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

Processing and properties of aligned multi-walled carbon nanotube/aluminoborosilicate glass composites made by sol-gel processing

We describe a novel sol-based approach for producing aluminoborosilicate glass composites containing continuous, aligned carbon nanotubes. The process involves the production of aligned carbon nanotubes (ACNT) via aerosol chemical vapour desposition (CVD), followed by infiltration of the ACNT with aluminoborosilicate sol. The advantages of this process are three fold: (1) aerosol CVD is an efficient method of producing clean, aligned arrays of CNTS, (2) sol-gel chemistry provides a simple route to infiltration of the ACNTs, and (3) carbon nanotube (CNT) agglomeration problems associated with CNT composites are circumvented. ACNTs (carpets) with heights of up to 4.4 mm were grown with areas of 10 mm x 20 mm for composite fabrication. The composite showed extensive pull-out of the CNTs on a fracture surface and improved thermal and electrical conductivities of 16 Wm⁻¹K⁻¹ and 5-8 x 10² Sm⁻¹ respectively compared with only 1.2 Wm⁻¹K⁻¹ and 10⁻¹³Sm⁻¹ for the monolithic glass

Spray deposited fluoropolymer/multi-walled carbon nanotube composite films with high dielectric permittivity at low percolation threshold

High performance perfluoro alkoxy (PFA) and chemical vapor deposition-grown multi-walled carbon nanotube (MWCNT) composite films with thicknesses of 30 μm were prepared using a scalable spray deposition technique. A homogeneous distribution of MWCNTs within the PFA matrix was confirmed by electron and optical microscopy. Dielectric permittivity for PFA/MWCNT films at low frequencies, and a very weak dependence of dielectric permittivity on temperature in the range 25-230 °C. Very low percolation threshold volume fractions of ca. 0.0043 and 0.0017 were attained for MWCNTs with two different aspect ratios, which have been explained by an inherent feature of spray route, a microcapacitor model and percolation theory. The combination of PFA/MWCNT composites and the spray deposition route provides a promising approach for the fabrication of industrial scale composite films with well-controlled dielectric properties for micro-electronic and high temperature applications

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