The remarkable electrical, thermal, mechanical, and optical properties of graphene and its derivative grapheme oxide have recently gained great importance, along with the large surface area and single-atoms thickness. In this respect, several techniques of synthesis such as chemical exfoliation, mechanical exfoliation, or chemical synthesis have been discovered. However, the development of graphene with fewer defects and on a large scale poses major challenges; therefore, it is increasingly necessary to produce it in large proportions with high quality. This paper reviews the top-down synthesis approach of graphene and its well-known derivative graphene oxide. Furthermore, characterization of graphene oxide nanomaterial is a critical component of the analysis. The characterization techniques employed to determine the quality, defects intensity, number of layers, and structures for graphene oxide nanomaterial at the atomic scale. This article focuses on the different involved characterization methodology for graphene oxide with their percentage utilization for the past 11 years. Additionally, reviewing all of the characterization literature for the last 11 years would be a difficult task. Therefore, the aim is to outline the existing state of graphene oxide by different characterization techniques and provide a comparative analysis based on their percentage utilization.

    Abstract
    1 Introduction
    2 Graphene: sp2-hybridization
    3 Properties of graphene nanomaterial
    4 Synthesis of graphene nanomaterial
    5 Top–down process
        5.1 Mechanical exfoliation
        5.2 Chemical exfoliation
        5.3 Chemical synthesis
    6 Advantages and limitation of top–down approach
    7 GO structures
    8 GO characterization techniques
        8.1 SEM technique
        8.2 TEM technique
        8.3 AFM technique
        8.4 Optical microscope imaging technique
        8.5 Fluorescence quenching microscopy (FQM) technique
        8.6 XRD technique
        8.7 Raman spectroscopy technique
        8.8 Thermogravimetric analysis (TGA)
        8.9 FTIR technique
        8.10 XPS technique
        8.11 NMR Spectroscopy Technique
    9 Summary of GO characterization methods
    10 Conclusion
    11 Future prospects
    Acknowledgements 
    References

• Abdullah Anwar(Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, Department of Civil Engineering, Integral University)
• Ta‑Peng Chang(Department of Civil and Construction Engineering, National Taiwan University of Science and Technology)
• Chun‑Tao Chen(Department of Civil and Construction Engineering, National Taiwan University of Science and Technology)