A. Jha

Surface modification of amorphous carbon nanotubes with copper phthalocyanine leading to enhanced field emission

Amorphous carbon nanotubes (ACNTs) were synthesized by following a simple chemical route with ammonium chloride and ferrocene taken as starting materials and heating at 250 °C under an open atmosphere. The as-prepared samples were oxidized and chemically activated by simple acid treatment and further functionalized by copper phthalocyanine (CuPc). The attachment of CuPc at the walls of the nanotubes was investigated by Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopy. The field emission properties of ACNTs was found to be greatly enhanced after coating them with CuPc. The effects of inter-electrode distance on the field emission properties of the functionalized samples were also studied.

Edge effect enhanced electron field emission in top assembled reduced graphene oxide assisted by amorphous CNT-coated carbon cloth substrate

In this work a hybrid structure assembly of amorphous carbon nanotubes (a-CNTs) -reduced graphene oxide (RGO) has been fabricated on carbon cloth/PET substrates for enhanced edge effect assisted flexible field emission device application. The carbon nanostructures prepared by chemical processes were finally deposited one over the other by a simple electrophoretic deposition (EPD) method on carbon cloth (CC) fabric. The thin films were then characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscope (HRTEM). Field assisted electron emission measurement was performed on this hybrid structure. It was observed that the hybrid carbon nanostructure showed exceptional field emission properties with outstanding low turn-on and threshold field (Eto∼ 0.26 Vμm−1, Eth ∼ 0.55 Vμm1). These observed results are far better compared to standalone and plasma etched edge enhanced RGO systems due to the bottom layer a-CNTs bed which assisted in significant enhancement of edge effect in RGO sheets.

Synthesis and characterization of water soluble functionalized amorphous carbon nanotube-poly(vinyl alcohol) composite

AbstractA simple low-temperature synthesis method of amorphous carbon nanotubes (a-CNTs) and poly(vinyl alcohol) (PVA) composite thin films has been reported. Initially the a-CNTs have been functionalized by acid treatment for getting better dispersion in water. The functionalized a-CNTs show much enhanced solubility in water. The microstructures of the as-prepared tubes, functionalized tubes, and PVA-a-CNTs composite have been investigated with the help of a field emission scanning electron microscope. A detailed study on the structural, optical, and thermal properties and a hardness test of the composite has revealed that a-CNTs can act as good reinforcement materials such as crystalline CNTs, when composites are made with polymers. Also, it has been shown that the sheet resistance of the PVA-a-CNTs composite monotonically decreases with increasing a-CNTs concentrations in the composites. Optical studies showed a shift in the optical gap indicating the formation of cross-linking into the host matrix. The composite shows a higher crystallinity with increased a-CNTs concentration, compared to pure PVA. The swelling test shows that due to the introduction of the carboxylic group into a-CNTs’ walls, it gradually becomes hydrophilic.

Unique quasi-vertical alignment of RGO sheets under an applied non-uniform DC electric field for enhanced field emission

In this paper, we report unique quasi-vertical alignment of reduced graphene oxide (RGO) sheets under an applied non-uniform high DC electric field deposited on a carbon cloth (CC) substrate, which eventually resulted in enhanced field emission characteristics. Significant improvement in enhancement factor was achieved with major increment in current due to the alignment of thin RGO edges under an applied non-uniform electric field. The non-uniform field was generated by the conical shape of the top electrode (anode). Moreover, the experimental findings have been validated through simulated modeling of the electric field over RGO sheets using the finite element method for both planar and conical top electrode geometrical configurations. This observed phenomenon could have a potential fundamental impact on field emission applications with vertically aligned graphene and RGO based materials in the coming years.