What is it about?
Graphene oxide is a material that has shown great potential in various applications due to its unique properties, including high surface area, good electrical conductivity, and mechanical strength. However, its complex structure with numerous functional groups and holes has made it difficult to fully understand and utilize. In this study, we explored the impact of the epoxidation process on the structure of graphene oxide and the possible pathways for further oxidation. Epoxides are organic compounds that contain an oxygen atom bonded to two adjacent carbon atoms. They are commonly used as intermediates in various industrial processes, including the production of graphene oxide. We found that epoxidation adds more disorder to the already complicated structure of graphene oxide, making it harder to use. We identified 16 different ways that epoxide molecules can be arranged on the graphene surface, and the stability of these arrangements depends on how the molecules are arranged in relation to each other. We also investigated the way the epoxy bonds in graphene oxide break apart when it is further oxidized. We found that the conventional model of the unzipping of the underlying epoxy C-C bond through the cooperativity of strain from three-membered rings and conjugative stabilization from residual sp2 character is incongruous. Instead, we proposed an improved bonding model of epoxide that accounts for the observed variations in C-C bond lengths and energetics of epoxides in different environments. By understanding how the bonds break apart, we hope to facilitate strategic mechanistic control for further oxidation. Overall, this research provides important insights into the structure of graphene oxide and the impact of epoxidation on its properties. By identifying the vulnerabilities of its backbone and the pathways for further oxidation, the researchers hope to advance the understanding and utilization of this material in various applications.
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Why is it important?
This work is important for several reasons. Firstly, graphene oxide is a material with numerous potential applications, including in electronics, energy storage, and biomedical engineering. However, its complex structure has made it difficult to fully understand and utilize. By investigating the impact of the epoxidation process on the structure of graphene oxide, this research provides important insights into how to optimize the material for specific applications. Secondly, the identification of 16 different ways that epoxide molecules can be arranged on the graphene surface is significant because it highlights the importance of understanding the local environment of the functional groups in graphene oxide. This knowledge can inform the design of more effective oxidation strategies that can lead to the formation of graphene oxide with more desirable properties. Thirdly, our proposal of an improved bonding model of epoxide is significant because it provides a more accurate understanding of the breaking apart of epoxy bonds in graphene oxide when it is further oxidized. This model could inform future research in this area and facilitate the development of new oxidation strategies that can be used to control the properties of graphene oxide for specific applications. Overall, this work provides important insights into the structure and properties of graphene oxide and has the potential to inform the development of more effective strategies for the synthesis and functionalization of this material.
Perspectives
This work provides important insights into the structure and properties of graphene oxide, which is a material that has attracted a lot of attention due to its potential applications in various fields. We have used molecules to materials approach to investigate the impact of the epoxidation process on the structure of graphene oxide, which is a critical step in its synthesis and functionalization. Our findings provide important information on how the local environment of the functional groups in graphene oxide can affect its properties, which is important for the development of more effective strategies for its synthesis and functionalization. Furthermore, the proposal of an improved bonding model of epoxide is a significant contribution to the field. The ability to understand how the epoxy bonds break apart in graphene oxide when it is further oxidized is critical for the development of new oxidation strategies that can be used to control the properties of the material for specific applications. Overall, this work has important implications for the development of graphene oxide for various applications. The insights gained from this research can inform the design of new strategies for the synthesis and functionalization of the material, which could have a significant impact on the advancement of various fields.
Gaurav Jhaa
Pondicherry University
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This page is a summary of: Nature of Interactions between Epoxides in Graphene Oxide, The Journal of Physical Chemistry C, December 2019, American Chemical Society (ACS),
DOI: 10.1021/acs.jpcc.9b10262.
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Nature of Interactions between Epoxides in Graphene Oxide
Graphene oxide exhibits extensive disorder with multitudes of functional groups and holes, making its structure an abstract concept. Multiple structural models make it a dark horse and hamper its utility despite its synthetic ease, maneuverability, and promising applications. Here we probe the impact of the epoxidation process, which is arguably the first kinetic step in graphene oxidation, to identify the induced vulnerabilities of its backbone and to cognize possible pathways for further oxidation. Probing the topological and geometrical variations in the distribution of epoxide on the graphene lattice, we find that the conformational entropy, driven by the combinatorial growth of isomers, aid, and abet disorder. Graph theoretical enumeration gives sixteen distinct epoxide environments within symmetrically equivalent epoxides. Their stability is primarily influenced by the steric repulsion between the oxygen lone-pairs and the overlap compatibility of the inter-epoxy C-C bond. Avoiding steric repulsion either by topology or by equatorial splaying of oxygens leads to stability, without which the network is weakened either by elongation of C-C bonds or by axial splaying of oxygens leading to uneven C-O bonds. The proposed unzipping of the underlying epoxy C-C bond through the cooperativity of strain from three-membered rings and conjugative stabilization from residual sp2 character is incongruous. With an improved bonding model of epoxide, we account for the observed variations in C-C bond lengths and energetics of epoxides in different environments that facilitate strategic mechanistic control for further oxidation.
New concept of hybridization based on sp hybrid orbitals in three membered ring
The new model of epoxide bonding is based on sp hybridization, in which the s orbital and the radial p orbital of the epoxide ring are mixed to yield one sp hybrid pointing inwards and another pointing outward. The inward-pointing sp hybrid, along with the p orbital tangential to the epoxide ring, is responsible for the bonding within the epoxide ring while the outward-pointing sp hybrid with the p orbital perpendicular to the epoxide ring is presumed to be involved in the exo-epoxy bonding. This new hybridization model based on FMO theory is similar to the sp hybrid model typically used in polyhedral boranes except that only one of the unhybridized p orbital (tangential to the epoxide ring) is involved in the bonding within the epoxide ring while the unhybridized p orbital perpendicular to the ring is engaged in exo-epoxy bonding.
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