Oriented Carbon Nanostructures by Plasma Processing: Recent Advances and Future Challenges

Abstract

Carbon, one of the most abundant materials, is very attractive for many applications because it exists in a variety of forms based on dimensions, such as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and-three dimensional (3D). Carbon nanowall (CNW) is a vertically-oriented 2D form of a graphene-like structure with open boundaries, sharp edges, nonstacking morphology, large interlayer spacing, and a huge surface area. Plasma-enhanced chemical vapor deposition (PECVD) is widely used for the large-scale synthesis and functionalization of carbon nanowalls (CNWs) with different types of plasma activation. Plasma-enhanced techniques open up possibilities to improve the structure and morphology of CNWs by controlling the plasma discharge parameters. Plasma-assisted surface treatment on CNWs improves their stability against structural degradation and surface chemistry with enhanced electrical and chemical properties. These advantages broaden the applications of CNWs in electrochemical energy storage devices, catalysis, and electronic devices and sensing devices to extremely thin black body coatings. However, the controlled growth of CNWs for specific applications remains a challenge. In these aspects, this review discusses the growth of CNWs using different plasma activation, the influence of various plasma-discharge parameters, and plasma-assisted surface treatment techniques for tailoring the properties of CNWs. The challenges and possibilities of CNW-related research are also discussed.

N-Graphene Nanowalls via Plasma Nitrogen Incorporation and Substitution: The Experimental Evidence

“…The active N-containing species in NH 3 plasma could react with the defects and incorporate nitrogen to the structure [73]. NEXAFS results propose that the defects formed during plasma treatment are DV (5-8-5) and SV (5)(6)(7)(8)(9). Transformation of DV (5-8-5) to stable DV (555-777) is well known [74,75], can be made by the ion bombardment during the plasma exposure, which is the favourable site for nitrogen incorporation.…”

“…Carbon nanowalls (CNWs) or graphene nanowalls are considered as two-dimensional (2D) graphite sheet nanostructures composed of stacks of graphene sheets with open boundary edges standing vertically on the substrate and widely synthesised using the plasma-enhanced chemical vapour deposition [1][2][3][4][5]. The nucleation and growth of nanosized structures on the substrate are influenced by temperature, plasma power and pressure, which are controlling the thickness of self-aligned nanowalls in the range of few nanometres to a few tens of nanometres with an interlayer spacing of few nanometres [6][7][8][9]. Catalyst-free synthesis, large surface area, sharp edges with open boundaries and ease of functionalisation of CNWs can be suitable for numerous applications such as field emission [10,11], electrochemical and energy storage applications [12][13][14][15][16][17][18] and novel electronic devices [19,20].…”

Oriented Carbon Nanostructures from Plasma Reformed Resorcinol-Formaldehyde Polymer Gels for Gas Sensor Applications

“…During the plasma surface treatment, argon and hydrogen are dissociated and form various species in plasma ( Figure S4 ). H 2 is considered as a critical factor in the nucleation and growth of many carbon-based nanostructures [ 1 , 54 ], while Ar is considered as the amorphous etchant. As seen from the time-dependent changes on the surface morphology ( Figure 2 ), at the initial stage, carbon building blocks are extracted from the top-layer of RF gel due to the ion bombardment and neutral radical interaction and re-form into hexagonal carbon rings, which is considered as the essential elements for the growth of OCNs [ 55 ].…”

“…Carbon nanostructures (CNs) have several unique structural, morphological, and electrical properties [ 1 ]. Owing to their structure, morphology, and preferential orientation, CNs have gained research attention in different fields of electronic, gas sensing, and energy storage applications.…”

Synthesis of Graphene-based Materials for Surface-Enhanced Raman Scattering Applications

“…The nanographite domains are well aligned, and the plane of the CNW sheet is nearly parallel to the [0001] direction of the graphite [104,105]. The height of the CNWs typically ranges from 1 μm to 2 μm [106,107], while their thickness is less than 100 nm [105] to 2 nm [108]. The shape of the individual CNW sheets can vary from wavy to straight depending on the growth conditions [106,109] (Figure 7).…”