Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

Biogenic and Non-Biogenic Waste Utilization in the Synthesis of 2D Materials (Graphene, h-BN, g-C2N) and Their Applications

There is a significant amount of waste generated which creates a huge environmental issue for humanity/earth and a tremendous number of varieties of resources of a different kind are needed globally. In this context, nanoscience technology has shown its potential ability to solve the above issues and provides realistic applications and devices. The beauty of nanotechnology is its multidisciplinary approach, in which green nanotechnology has been translated to focus on waste materials. Waste materials are generally generated from biogenic (rice husk, dead leaves, waste food, etc.) and non-biogenic (several types of plastics waste, lard oil, etc.) materials produced from municipal or industrial waste. Currently, a large number of efforts have been made to utilize the waste materials for the synthesis of 2D materials in a greener way. This green synthetic approach has two advantages 1) it reduces the cost of synthesis and 2) includes minimal use of hazardous chemicals. Biogenic wastes (contains biomolecules) contain several significant constituents such as co-enzymes, enzymes, proteins, terpenoids, etc. These constituents or biomolecules are known to play an energetic role in the formation of a different variety of 2D materials and hence control the protocols of green synthesis of 2D materials. This review focuses on the exploration of the current understanding of 2D-layered material synthesis methods using waste material produce from biogenic and non-biogenic waste. It also investigates the applications of various 2D-layered materials in perspective with synthesis from waste and future challenges along with their limitations to industrial-scale synthesis.

Single-step growth of graphene and graphene-based nanostructures by plasma-enhanced chemical vapor deposition

The realization of many promising technological applications of graphene and graphene-based nanostructures depends on the availability of reliable, scalable, high-yield and low-cost synthesis methods. Plasma enhanced chemical vapor deposition (PECVD) has been a versatile technique for synthesizing many carbon-based materials, because PECVD provides a rich chemical environment, including a mixture of radicals, molecules and ions from hydrocarbon precursors, which enables graphene growth on a variety of material surfaces at lower temperatures and faster growth than typical thermal chemical vapor deposition. Here we review recent advances in the PECVD techniques for synthesis of various graphene and graphene-based nanostructures, including horizontal growth of monolayer and multilayer graphene sheets, vertical growth of graphene nanostructures such as graphene nanostripes with large aspect ratios, direct and selective deposition of monolayer and multi-layer graphene on nanostructured substrates, and growth of multi-wall carbon nanotubes. By properly controlling the gas environment of the plasma, it is found that no active heating is necessary for the PECVD growth processes, and that high-yield growth can take place in a single step on a variety of surfaces, including metallic, semiconducting and insulating materials. Phenomenological understanding of the growth mechanisms are described. Finally, challenges and promising outlook for further development in the PECVD techniques for graphene-based applications are discussed.