The synthesis, characterization, investigation, and utilization of nanomaterials are the main topics in nanotechnologies. A "marvel substance," graphene is indeed the world's strongest, thinnest, and sternest material but also an efficient heat and electrical conductor. Graphene, a monolayer carbon, is the fundamental constituent of all other significant allotropes. Because of its low price, easy accessibility, and ubiquitous ability to convert to graphene, graphene oxide or GO is a critical nanomaterial.
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Properties of Graphene Oxide
GO’s size as a synthesized monoatomic layer of carbon is around 1 nm, while the longitudinal length of a Graphene Oxide sheet, on either hand, could reach micrometers. The suppleness of GO can also be seen from a structural analysis standpoint: most substances, even those that are brittle in nature, may soften and become malleable once their aspect ratio is greater.
As well as this, GO's wide range of soft material qualities is indicated from its chemical composition.
Synthesis Techniques of GO
Graphene oxide has been extensively studied as a standalone substance for creating a range of instruments, as an additive for boosting the effectiveness of materials, and as a precursor for the various chemical and physical reductions of graphene. Since 1855, numerous techniques for synthesizing GO have already been developed, the most renowned of which being Hummers' technique, which combines KMnO4 potassium permanganate and (NaNO3) sodium nitrate.
The Hummers process, for instance, is used to oxidize and exfoliate pure graphite to produce GO chemically.
There are numerous oxygen-containing compounds on the carbon surface of 3 GO, including hydroxyl, carboxylic, and epoxide structural features, though the precise structure and composition of chemically synthesized Graphene Oxide are still debated.
Innovations in different Graphene Oxide production processes have been researched for years to develop better, safer, and more efficient alternatives. Even though the existing Hummers method for extracting graphene is among the oldest, it has become one of the most efficient ways to mass-produce graphene. The carbon per oxygen ratio of the graphene formed may be used to assess the efficiency of this oxidation reaction.
Innovations and Monolithic Crystalline Synthesis Approaches
The Tour group has made improvements to Hummers' method. The method excludes NaNO3 to avoid toxic gas production, utilizing ice rather than liquid water to prevent rising temperatures. It can enhance easier and better process control, escalate the degree and yield of oxidation, and boost the retention of carbon rings inside the basal plane by utilizing phosphoric acid (H3PO4) to the reaction.
The method by Tour group's called Improved Synthesis of Graphene Oxide received the enthusiasm of the scientific community, demonstrating the method's relevance and simplicity.
Lu's " monolithic crystalline swelling " approach is another unique approach for synthesizing graphene oxide, relating to the simplicity with which the GO produced may be washed. However, a group of researchers found that products were not homogenous and contained a significant number of black particles after following experimental conditions. Apparently, this technique was ineffective because the one-step procedure and the lack of agitation resulted in a non - homogeneous reaction media, and consequently, a non - homogeneous product.
Pre-Treatment Procedures
Well-known enhanced techniques for synthesizing GO contain some parameter variations and a necessary pre-treatment procedure for further enhancement. The pre-treatment technique makes it simple to expand graphite chemically before oxidizing it with piranha solution.
Numerous studies have found that employing extended graphite (EG) as a precursor material can assist in agglomerating the graphitic layers, boost the exposed specific surface area (SSA), and reduce the intense oxidation that occurs as the sheets progress from the margins to the center.
Simulating self-assembly and dispersion of graphene oxide in polymers
Video Credit: Wiley/YouTube.com
Ecologically-Friendly Procedures
One synthesis technique of Graphene oxide is a one-step, ecologically friendly method that does not require high temperatures or the use of any complicated instruments. Furthermore, this procedure does not require any washing or drying and simply involves easy stirring and resting the graphite in a cold piranha solution.
The following oxidation reaction, which took place at a lower temperature (35 °C rather than 50 °C) and over a shorter period of time (approximately six hours instead of ten hours), produced GO with a higher degree of oxidation, bigger sheets, and fewer impurities.
Industrial Relevancy of Graphene Oxide
The adsorption ability of GO against metal ions is outstanding due to its large surface area and a considerable number of oxygen-functional molecules. GO also has various physicochemical characteristics, such as nanoscale size, large surface area, and electrostatic charge.
Considering these properties, it is unsurprising that Graphene Oxide is a vital substance utilized in cancer therapy, drug development, and molecular imaging in biotech and medicine. Solar cells, battery packs, bioelectronics, device applications films, ultracapacitors, and multifunctional substances are just a few other industrial examples of GO.
However, demand is directly proportional to graphene manufacturing. The increasing desire for renewable, lighter weight, flexible, and long-lasting substances has kept graphene in high demand, propelling the graphene oxide market internationally. As such, the Graphene Oxide market is likely to grow, increasing the relevancy of nanotechnology in a broad range of sectors for years to come.
Continue reading: Applications of Anodic Aluminum Oxide based Nanomaterials.
References and Further Reading
Benzait, Z., Chen, P. and Trabzon, L., (2021) Enhanced synthesis method of graphene oxide. Nanoscale Advances, 3(1), pp.223-230. Available at: https://doi.org/10.1039/D0NA00706D
Dideikin, A. and Vul', A., (2019) Graphene Oxide and Derivatives: The Place in Graphene Family. Frontiers in Physics, 6. Available at: https://doi.org/10.3389/fphy.2018.00149
Rhazouani, A., Gamrani, H., El Achaby, M., Aziz, K., Gebrati, L., Uddin, M. and AZIZ, F., (2021) Synthesis and Toxicity of Graphene Oxide Nanoparticles: A Literature Review of In Vitro and In Vivo Studies. BioMed Research International, 2021, pp.1-19. Available at: https://doi.org/10.1155/2021/5518999
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