Field electron emission enhancement of graphenated MWCNTs emitters following their decoration with Au nanoparticles by a pulsed laser ablation process

Abstract

A plasma-enhanced chemical vapor deposition (PECVD) process was adapted to alter the growth of multiwall carbon nanotubes (MWCNTs) so that graphene sheets grow out of their tips. Gold nanoparticle (Au-NP) decoration of graphenated MWCNTs (g-MWCNTs) was obtained by subsequent decoration by a pulsed laser deposition (PLD) process. By varying the number of laser ablation pulses (N(Lp)) in the PLD process, we were able to control the size of the gold nanoparticles and the surface coverage of the decorated g-MWCNTs. The presence of Au-NPs, preferentially located at the tip of the g-MWCNTs emitters, is shown to significantly improve the field electron emission (FEE) properties of the global g-MWCNT/Au-NP nanohybrid films. Indeed, the electric field needed to extract a current density of 0.1 μA cm(-)(2) from the g-MWCNT/Au-NP films was decreased from 2.68 V μm(-1) to a value as low as 0.96 V μm(-1). On the other hand, UV photoelectron spectroscopy (UPS) characterization revealed a decrease in the global work function of the Au-decorated g-MWCNT nanohybrids compared to that of bare g-MWCNT emitters. Surprisingly, the work function of g-MWCNT was found to decrease from 4.9 to 4.7 eV with the addition of Au-NPs-a value lower than the work function of both materials worth 5.2 and 4.9 eV for gold and g-MWCNT, respectively. Our results show that the N(Lp) dependence of the FEE characteristics of the g-MWCNT/Au-NP emitters correlates well with their work function changes. Fowler-Nordheim-theory-based calculations suggest that the significant FEE enhancement of the emitters is also caused by the Au-NPs acting as nanoscale electric field enhancers.

Synergistic Enhancement of Electrocatalytic CO2 Reduction with Gold Nanoparticles Embedded in Functional Graphene Nanoribbon Composite Electrodes

“…52,53,[56][57][58] Lower work function materials promote charge migration across the semicon-ductor-NP interface towards the high work function AuNPs, increasing electron density at the metal surface and shifting the catalytic onset. 31,42,[44][45][82][83][84][85][86][87] Theory and experiment indicate that the semiconducting GNRs employed here, and particularly cove-type GNRs, feature appreciably lower work functions than other carbon supports like graphene or Cblack, consistent with the positively shifted onset potentials observed (Table 1). 37,[46][47]86,[88][89][90][91][92] One hour controlled potential electrolysis experiments over a potential range from -0.87 V to -0.37 V underline the synergy between AuNPs and GNRs.…”

“…31,42,[44][45][82][83][84][85][86][87] Theory and experiment indicate that the semiconducting GNRs employed here, and particularly cove-type GNRs, feature appreciably lower work functions than other carbon supports like graphene or Cblack, consistent with the positively shifted onset potentials observed (Table 1). 37,[46][47]86,[88][89][90][91][92] One hour controlled potential electrolysis experiments over a potential range from -0.87 V to -0.37 V underline the synergy between AuNPs and GNRs. Both Faraday efficiency (FECO, Figure 4E) and partial current (jCO, Figure 4F) for CO2 reduction to CO by GNR-AuNP composites dramatically exceed those of Cblack-AuNP across a broad potential window.…”

Field Emission of Wet Transferred Suspended Graphene Fabricated on Interdigitated Electrodes

“…It indicates that the emission efficiency becomes higher along with the increased field. This phenomenon was reported in the studies of single-layer graphene, graphenated carbon nanotubes, or multilayer graphene composites on nanostructured substrates . J. C. She et al assumed that the classical FN equation is not enough to describe these experimental results, and the quantum effect should be considered when discussing the field emission from 2D graphene membrane.…”

Ag nanoparticle-decorated single wall carbon nanotube films for photovoltaic applications

“…PLD is a synthesis method known to produce clean and uniform NPs over a surface, without the risk of chemical contamination that arises from chemical methods. It has been employed to decorate CNTs in several applications, including field effect emission [22] and optoelectronics [23,24]. We show that the PLD method yields clean nanohybrids (NHs) and that the SWCNTs films are left structurally intact after the deposition process.…”