الفهرس 
Synthesis of Graphene-based MaterialsOnly 14 pages are availabe for public view
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Abstract
This dissertation embarks upon a groundbreaking expedition to investigate the frontiers of two-dimensional nanomaterials derived from graphene then integrated with novels structure of metal oxide to obtain nano composite for the purpose of environmental remediation.
The inaugural chapter focuses on this thesis, an exhaustive examination is conducted on the multifaceted challenges posed by water pollution, encompassing both organic and inorganic contaminants such as synthetic dyes and carcinogenic hexavalent chromium. This discourse sets the stage for an in-depth exploration of nano materials, particularly focusing on the dimensional intricacies and the unparalleled superiority of graphene within the realm of two-dimensional (2D) materials. A meticulous analysis of various synthesis methods for graphene and its derivatives is presented, elucidating the nuanced differences between them. Subsequently, emphasis is placed on the pivotal role of integrating graphene with metal oxides, highlighting the significant enhancements in activity and characteristic properties thereby achieved. The chapter culminates with a comprehensive literature survey, shedding light on recent advancements in the synthesis methodologies employed for nano composites comprising zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) with reduced graphene oxide (rGO). Furthermore, notable applications of these nano composites in photocatalytic domains are thoroughly examined, providing invaluable insights into their potential contributions to environmental remediation.
The second chapter of this thesis, meticulous attention is directed towards the experimental endeavors undertaken. The chapter commences with a detailed exposition of the methodologies employed in the preparation of graphene-based materials, including graphene oxide (GO), graphene oxide quantum dots (GOQDs), and the distinctive dendritic shapes of GOQDs denoted as F-GOQDs. Furthermore, the synthesis pathways for zinc, copper, and nickel precursors are meticulously elucidated, serving as pivotal intermediate stages in the production of metal oxide nanoparticles (NPs) such as ZnO, NiO, and CuO. Subsequently, a comprehensive exposition is provided regarding the integration of metal oxides with graphene sheets via ultrasound irradiation, which enables the efficient synthesis of nano composites.
The discussion extends to encompass the operational methodologies and instrumentation utilized in the experimental analyses, encompassing infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FESEM), and scanning transmission electron microscopy (STEM). Additionally, meticulous scrutiny is directed towards the techniques employed for the photolytic applications of these nano composites, particularly their efficacy in the degradation of dyes and detoxification of hexavalent chromium, thereby highlighting their pivotal role in advancing environmental remediation strategies.
In the culminating section of this scholarly endeavor, the Third chapter undertakes a comprehensive exploration of results and discussions pertaining to four distinct sections. Each section meticulously delves into the full characterization and application nuances of graphene oxide quantum dots (GOQDs), zinc oxide-reduced graphene oxide (ZnO-rGO), copper oxide-reduced graphene oxide (CuO-rGO), and nickel oxide-reduced graphene oxide (NiO-rGO) composites, respectively.
In the First Section the meticulous bottom-up self-assembly process employed in fabricating zero-dimensional graphene oxide quantum dots (GOQDs) through freeze-drying technique yielded intricately ordered, multi-dimensional dendritic nanostructures. The investigative journey traced the transformative stages from graphite precursor to graphene oxide, GOQDs, and the distinctive graphene oxide dendritic shape (F-GOQDs), scrutinizing their stepping function groups via Fourier transform infrared (FT-IR) and UV-visible spectroscopy. Raman spectroscopy unveiled notable enhancements in the frequencies and intensity of the D and G bands as the size of GOQDs increased, alongside intensified and well-defined higher-order modes. XRD analysis confirmed average crystallite sizes of 2.3nm for GOQDs and 5.5nm for F-GOQDs, consistent with TEM findings. FESEM and STEM images vividly illustrated the amorphous stacking of GOQDs pre-lyophilization and the symmetrical dendritic growth post-lyophilization. Additionally, density-functional theory (DFT) calculations provided insights into the molecular-level origins behind the increased dipole moment, electrostatic potential, and decreased bandgap energy of F-GOQDs motifs resulting from dendrite void coupling.
The Second section explores the synthesis and characterization of modified ZnO nanoparticles and ZnO-rGO nanocomposites for environmental remediation applications. A facile solid-state decomposition method and an ultrasonication-assisted approach were employed for ZnO and ZnO-rGO synthesis, respectively. The synthesized ZnO nanoparticles exhibited exceptional photocatalytic activity against both cationic and anionic azo dyes, demonstrating potential for treating dye-contaminated industrial wastewater. Comprehensive characterization using advanced techniques confirmed the formation of hexagonal 2D-ZnO nanoparticles with a reduced bandgap compared to bulk ZnO. Photocatalytic degradation experiments revealed excellent performance by ZnO, achieving complete degradation of model pollutants (Fluorescein and Rhodamine B) under UV irradiation. While ZnO-rGO composites showed lower degradation rates, their photocatalytic capabilities suggest promise for further exploration in dye wastewater treatment.
The Third section Nano-sized copper oxide CuO and GO exhibit promising characteristic properties. A composite of CuO and reduced graphene oxide rGO nanosheets, CuO/rGO, was synthesized through probe sonication at 600 W. The synthesized compounds underwent comprehensive characterization using XRD, FESEM, and HRTEM to study structural parameters including lattice constant, crystallite size, and strain. Both CuO and rGO were observed to form nanosheets, as revealed by electron microscopy. The optical bandgap of CuO and CuO/rGO composite was determined. Additionally, a composite of 2D rGO/CuO nanosheets was synthesized and characterized by various techniques, with particular emphasis on the inclusion of rGO into CuO. XRD and XPS studies highlighted the influence of rGO on the surface morphology of CuO nanosheets. The composite exhibited promising photocatalytic activity in the reduction of Cr(IV) to non-toxic Cr(III). Given the impact of rGO on surface morphology and charge transport, further investigation of its potential in sensing applications is warranted. The photocatalytic reduction of toxic Cr(VI) to Cr(III) by CuO/rGO nanocomposite was investigated, demonstrating a photo-reduction efficiency of up to 75% with the addition of rGO to CuO. A mechanism for the photoreduction process was proposed.
The fourth section unveils a novel synthesis method for the fabrication of a NiO/rGO nanocomposite, achieved through the in-situ transformation of a Ni2O3 thin layer in conjunction with NiO quasi-sphere nanoparticles. This innovative approach harnesses a green solvo-thermal method during precursor synthesis, followed by a meticulously orchestrated calcination process and ultrasonic irradiation to attain the desired nanocomposite structure. Remarkably, the composite exhibits superior photocatalytic efficiency by 81 % in the degradation of fluorescein dye under UV light, owing to the enhanced electron-hole separation facilitated by the rGO matrix. Employing a suite of comprehensive characterization techniques including FTIR, XRD, and XPS, the intricate interaction mechanisms and the pivotal role of the Ni2O3 to NiO transformation in augmenting photocatalytic activity are elucidated. The study underscores the immense potential of the NiO/rGO nanocomposite as a robust material for environmental remediation applications, particularly in dye degradation.