Davide Mattia

Magnetically assembled carbon nanotube tipped pipettes

The authors have developed a biological probe at the nanoscale with a magnetic carbon nanotube (mCNT) tip that has the ability to transfer fluids. Fabrication is performed by injection of mCNTs into micropipettes, which are then positioned as probe tips via magnetophoresis, and affixed with polymeric adhesive. In this letter the authors discuss the magnetic fabrication process and demonstrate the versatility of this probe.

Flow enhancement in nanotubes of different materials and lengths

The high water flow rates observed in carbon nanotubes (CNTs) have previously been attributed to the unfavorable energetic interaction between the liquid and the graphitic walls of the CNTs. This paper reports molecular dynamics simulations of water flow in carbon, boron nitride, and silicon carbide nanotubes that show the effect of the solid-liquid interactions on the fluid flow. Alongside an analytical model, these results show that the flow enhancement depends on the tubes geometric characteristics and the solid-liquid interactions.

Induction and measurement of minute flow rates through nanopipes

A simple technique to simultaneously induce fluid flow through an individual nanopipe and measure the flow rate and the pressure difference across the pipe is described. Two liquid drops of different sizes are positioned at the two ends of the nanopipe. Due to the higher capillary pressure of the smaller drop, flow is driven from the smaller drop to the bigger drop. The instantaneous pressures of the two drops are estimated from the drops’ shapes and sizes. The flow rate is estimated by monitoring the sizes of the drops as functions of time with a microscope and a video camera. A theory that correlates the drops’ sizes and the flow rate is derived. Measurements are carried out with an ionic salt and glycerin to estimate the effective tube radius of the nanopipes with diameters ranging from 200 to 300nm. The tubes’ diameters are independently measured with a scanning electron microscope. The method is also verified by tracking the motion of fluorescent particles through the nanopipe. The paper provides a s...

Soft, Oxidative Stripping of Alkyl Thiolate Ligands from Hydroxyapatite‐Supported Gold Nanoclusters for Oxidation Reactions

A strategy for the mild deprotection of alkyl-thiolated (6-mercaptohexanoic acid, MHA, and 3-mercaptopropanoic acid, MPA) gold nanoclusters (Au NCs) supported on hydroxyapatite (HAP) has been developed by employing a peroxide (tert-butyl hydroperoxide, TBHP, or hydrogen peroxide, H2O2) as an oxidant. The thiol ligands on the supported Au NCs were removed after oxidation, and the size and integrity of the supported clusters were well-preserved. The bare gold clusters on HAP after removal of the ligands were catalytically effective for the epoxidation of styrene and the aerobic oxidation of benzyl alcohol. These two reactions were also investigated on calcined Au NCs that were supported on HAP for comparison, and the resulting Au NCs that were prepared by using this new strategy showed superior catalytic activity.

Multifunctional carbon nanotubes with nanoparticles embedded in their walls

Controlled amounts of nanoparticles ranging in size and composition were embedded in the walls of carbon nanotubes during a template-assisted chemical vapour deposition (CVD) process. The encapsulation of gold nanoparticles enabled surface enhanced Raman spectroscopy (SERS) detection of glycine inside the cavity of the nanotubes. Iron oxide particles are partially reduced to metallic iron during the CVD process giving the nanotubes ferromagnetic behaviour. At high nanoparticle concentrations, particle agglomerates can form. These agglomerates or larger particles, which are only partially embedded in the walls of the nanotubes, are covered by additional carbon layers inside the hollow cavity of the tube producing hillocks inside the nanotubes, with sizes comparable to the bore of the tube.

High CO2 and CO conversion to hydrocarbons using bridged Fe nanoparticles on carbon nanotubes

An aerosol assisted chemical vapour deposition method has been used to generate a carbon nanotube (CNT) based iron catalyst for the conversion of CO and CO2 to longer chain hydrocarbons. The same formed iron nanoparticles (NPs) used to catalyse the growth of the CNTs were activated in-line to act as catalysts for the CO and CO2 reduction. This methodology negates the multiple steps associated with the purification and subsequent tethering of metal catalyst nanoparticles to CNT supports common in the literature. Results show superior CO and CO2 conversion and selectivity to higher-order hydrocarbons when compared with a traditional system where iron NPs have been deposited onto CNTs from a solution.

Cobalt catalysts for the conversion of CO2 to light hydrocarbons at atmospheric pressure

A series of cobalt heterogeneous catalysts have been developed that are effective for the conversion of CO2 to hydrocarbons. The effect of the promoter and loadings have been investigated.

Towards Carbon-Neutral CO2 Conversion to Hydrocarbons

With fossil fuels still predicted to contribute close to 80 % of the primary energy consumption by 2040, methods to limit further CO2 emissions in the atmosphere are urgently needed to avoid the catastrophic scenarios associated with global warming. In parallel with improvements in energy efficiency and CO2 storage, the conversion of CO2 has emerged as a complementary route with significant potential. In this work we present the direct thermo-catalytic conversion of CO2 to hydrocarbons using a novel iron nanoparticle-carbon nanotube (Fe@CNT) catalyst. We adopted a holistic and systematic approach to CO2 conversion by integrating process optimization-identifying reaction conditions to maximize conversion and selectivity towards long chain hydrocarbons and/or short olefins-with catalyst optimization through the addition of promoters. The result is the production of valuable hydrocarbons in a manner that can approach carbon neutrality under realistic industrial process conditions.

Field controlled nematic-to-isotropic phase transition in liquid crystal-carbon nanotube composites

A nematic-to-isotropic transition has been observed in suspensions of carbon nanotubes (CNTs) and a cyanobiphenyl-based liquid crystal (LC) confined within an indium tin oxide glass sandwich cell. Upon the application of electric field, CNTs rotate out of plane short-circuiting the electrodes and producing a current flow through the CNTs. The resulting Joule heating leads to a local increase in temperature of the LC-CNT medium. Hence, starting from a metastable nematic phase, a complete transition to the isotropic phase is observed. On removal of the electric field, the transition is reversed with the LC-CNT medium returning to the nematic phase.

Hierarchical 3D ZnO nanowire structures via fast anodization of zinc

ZnO nanowire structures are used today in a variety of applications, from gas/chemical sensing to photocatalysis, photovoltaics and piezoelectric actuation. Electrochemical anodization of zinc foil allows rapid formation of high aspect ratio ZnO nanowires under mild reaction conditions compared to more common fabrication methods. In this study we demonstrate, for the first time, how 3D hierarchical ZnO nanowire structures can be fabricated by controlling the type of electrolyte and anodization voltage, temperature and time. Optimization of the reaction conditions yields growth rates of up to 3.2 μm min−1 and the controlled formation of aligned arrays of nanowires, flower-like nanostructures, and hierarchical, fractal nanowire structures. Annealing of the nanowires produces high surface area (55 m2 g−1) nanowires with slit-type pores perpendicular to the nanowire axis. In depth analysis of the anodization process allows us to propose the likely growth mechanisms at work during anodization. The findings presented here not only contribute to our knowledge of the interesting area of zinc anodization, but also enable researchers to design complex hierarchical structures for use in areas such as photovoltaics, photocatalysis and sensing.