In a recent article published in Scientific Reports, researchers from the United States of America and Egypt presented a novel approach for the eco-friendly synthesis of multi-wall carbon nanotubes (MWCNTs) over graphite nanosheets using yellow corn seeds.
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This method emphasizes a one-step process that eliminates the need for external catalysts, showcasing the potential of agricultural by-products in producing valuable carbon nanomaterials. The research aims to contribute to sustainable practices in nanotechnology by utilizing renewable resources.
Background
Carbon nanostructures, particularly carbon nanotubes, have garnered significant attention due to their unique properties, including high conductivity and mechanical strength. Traditional synthesis methods often involve complex procedures and the use of catalysts, which can introduce contaminants.
The study highlights the importance of developing greener synthesis techniques that minimize environmental impact while maintaining the quality of the produced nanomaterials. Previous research has explored various renewable carbon sources, with biomass being a prominent candidate for synthesizing carbon nanotubes.
The Current Study
The synthesis of MWCNTs was carried out using a thermal annealing process in a controlled environment. Untreated yellow corn seeds were positioned within the furnace, ensuring that the seeds were evenly distributed to allow for uniform heating. The samples were annealed at 1050 oC to facilitate the pyrolysis of the corn seeds, leading to the decomposition of organic materials and the formation of carbon-rich structures.
Scanning Electron Microscopy (SEM) was employed to visualize the surface morphology of the synthesized MWCNTs. Samples were coated with a thin layer of gold to enhance conductivity and prevent charging during imaging. The SEM images provided insights into the arrangement and distribution of the carbon nanotubes on the corn seed surfaces.
High-Resolution Transmission Electron Microscopy (HRTEM) was utilized to examine the internal structure and crystallinity of the MWCNTs. This technique allowed for the observation of the diameter and wall structure of the nanotubes, providing detailed information about their quality and alignment. Raman spectroscopy was conducted to assess the structural properties of the synthesized carbon materials.
The D and G bands were analyzed to evaluate the degree of graphitization and the presence of defects within the carbon structures. The intensity ratio of the D band to the G band (I_D/I_G) was calculated to quantify the level of disorder in the carbon nanotubes. Fourier-Transform Infrared Spectroscopy (FTIR) analysis was performed to identify functional groups present in the synthesized materials.
This technique provided information on the chemical bonding and the presence of any residual organic compounds that may not have been fully decomposed during the thermal annealing process. X-ray Diffraction (XRD) was employed to determine the crystallographic structure of the synthesized carbon nanomaterials. The diffraction patterns were analyzed to identify the phases present and to calculate the interlayer spacing of the carbon structures, indicative of the degree of graphitization.
Results and Discussion
The successful synthesis of MWCNTs from yellow corn seeds highlights the potential of utilizing agricultural by-products as renewable carbon sources for nanomaterial production. As confirmed by XRD, the crystallinity of the synthesized materials suggests that the thermal treatment effectively promotes the formation of graphitic structures. The sharp diffraction peaks indicate a high degree of order, which is crucial for applications requiring high electrical conductivity and mechanical strength.
SEM images displayed a uniform distribution of carbon nanotubes across the surface of the corn seeds. The low-magnification SEM images illustrated the extensive coverage of the seed surfaces by carbon nanostructures, with a notable preference for growth on the outer shell.
HRTEM images provided further insights into the internal structure of the synthesized MWCNTs. They confirmed the multi-walled nature of the nanotubes, with distinct layers visible in the cross-sectional views. The interlayer spacing measured approximately 0.34 nm, consistent with the typical spacing found in graphite, indicating a high degree of graphitization in the synthesized materials.
The preferential growth of MWCNTs on the outer shell of the corn seeds can be attributed to the higher surface area and the availability of carbon-rich compounds in that region. This observation is significant as it suggests that the morphology of the starting material can influence the growth patterns of carbon nanostructures. The trumpet-like structures observed in the rolled graphene nanosheets may indicate a self-extrusion mechanism during the synthesis, where the carbon material undergoes a transformation that facilitates the formation of these unique shapes.
Conclusion
The study successfully synthesized catalyst-free MWCNTs from yellow corn seeds using a simple and eco-friendly method. The findings highlight the feasibility of utilizing agricultural waste to produce high-quality carbon nanomaterials, paving the way for sustainable practices in nanotechnology.
The research contributes to the understanding of carbon nanostructures and emphasizes the importance of green synthesis techniques in minimizing environmental impact while maximizing the utility of renewable resources. Future research is encouraged to further explore the applications and optimization of these synthesized materials.
Journal Reference
Duraia, Es.M., et al. (2024). Efficient eco-friendly synthesis of carbon nanotubes over graphite nanosheets from yellow corn: a one-step green approach. Scientific Reports. DOI: 10.1038/s41598-024-65893-6