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We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.

Both fullerenes and single-walled carbon nanotubes (SWNTs) exhibit many advantageous properties. Despite the similarities between these two forms of carbon, there have been very few attempts to physically merge them. We have discovered a novel hybrid material that combines fullerenes and SWNTs into a single structure in which the fullerenes are covalently bonded to the outer surface of the SWNTs. These fullerene-functionalized SWNTs, which we have termed NanoBuds, were selectively synthesized in two different one-step continuous methods, during which fullerenes were formed on iron-catalyst particles together with SWNTs during CO disproportionation. The field-emission characteristics of NanoBuds suggest that they may possess advantageous properties compared with single-walled nanotubes or fullerenes alone, or in their non-bonded configurations. [ABSTRACT FROM AUTHOR]

Abstract: We have recently reported that onion-like shell-shaped carbon nanoparticles of high crystallinity could be generated through critical transition in the acetylene flow irradiated by a cw infrared CO2 laser [Choi et al. Advanced Materials 2004;16:1721–25]. This transition appeared as the temperature jump above a threshold value of the laser irradiance. The present paper explains the origin of this recent discovery. The heat balance on the surface of the growing particle is shown to allow the existence of two stable particle temperatures. Then, the temperature jump observed in our recent study is a transition from the low temperature regime to the high temperature regime. Implications of the finding for the processes of the carbon nanoparticle formation from hydrocarbons are also discussed. [Copyright &y& Elsevier]

We show that the conventional consideration of the electron-field emission from nanocarbons cannot explain the experimentally observed results. We suggest a mechanism of the field emission occurrence from nanocarbons that can solve the existing puzzles. This mechanism implies two successive processes: (1) Tunneling through the low-energy barrier from the metallic region into the semiconducting region under the external macroscopic electric field and (2) tunneling through the high-energy barrier from the semiconducting region into a vacuum under the Coulomb field of an additional electron appearing in the first process. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights from the article: Electrodes: High-Performance Solution-Processed Double-Walled Carbon Nanotube Transparent Electrode for Perovskite Solar Cells (Adv. Keywords: double-walled nanotubes; indium free; perovskite solar cells; solution-processed electrodes; transparent electrodes Double-walled nanotubes, indium free, perovskite solar cells, solution-processed electrodes, transparent electrodes.

Abstract: The formation of a novel hybrid material, NanoBuds, single-walled carbon nanotubes (CNTs) with covalently attached fullerenes was investigated in a ferrocene–carbon monoxide system. Fullerenes and CNTs were simultaneously formed by carbon monoxide disproportionation on the surface of iron particles in the presence of etching agents such as H2O and CO2. On the basis of parametric investigations and in situ sampling of the product from different locations in the reactor the mechanisms for NanoBud formation are discussed. [Copyright &y& Elsevier]