Integration of noble metals on graphene is renowned for their catalytic and antioxidant prowess. However, utilization of toxic chemicals in the synthesis creates environmental pollution and poisonous nature of chemically synthesized materials. To address this, an economical and eco-friendly method for synthesizing graphene-gold (BRG-Au) nanocomposite by anchoring gold nanoparticles (Au NPs) onto reduced graphene oxide sheets using betel leaf extract as a reducing and stabilizing agent is presented. Comprehensive structural characterizations through UV–Visible, Raman, FT-IR, and XRD analyses confirm the successful formation of the BRG-Au nanocomposite. Morphological assessments utilizing FE-SEM and TEM techniques revealed the presence of transparent, twinkling graphene sheets embellished with 20 to 60 nm of Au NPs in various shapes, including spherical, triangular, pentagonal, circular, and trapezoids. The catalytic and antioxidant activities of the BRG-Au nanocomposite were thoroughly evaluated. In catalytic trials, the nanocomposite exhibited remarkable efficiency in the reduction of 4-nitrophenol to 4-aminophenol, accomplishing this transformation within a mere 30 min during the initial cycle and maintaining stable catalytic performance over three consecutive cycles. Additionally, antioxidant analyses employing Total Antioxidant Activity and 2,2-diphenyl-1-picrylhydrazyl methods demonstrated that BRG-Au nanocomposite possessed equal or superior antioxidant activity than the ascorbic acid standard. This research thus underscores the promising potential of environmentally benign synthesis method for graphene-gold nanocomposite with enhanced catalytic and antioxidant properties.

Evaluation of the catalytic and antioxidant activity of in situ green synthesized graphene-gold nanocomposite
    Abstract
        Graphical Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Betel leaves extract
        2.3 BRG-Au nanocomposite
        2.4 Characterization techniques
        2.5 Catalytic reduction of 4-Nitrophenol
        2.6 Antioxidant activity analysis
    3 Results and discussion
        3.1 FESEM analysis
        3.2 TEM analysis
        3.3 UV–Visible analysis
        3.4 FTIR analysis
        3.5 X-Ray diffraction analysis
        3.6 Raman analysis
        3.7 Mechanism of formation of BRG-Au nanocomposite
        3.8 Catalytic reduction of 4NP to 4AP
        3.9 Antioxidant activity analysis
            3.9.1 Total antioxidant activity
            3.9.2 DPPH radical scavenging activity
    4 Conclusion
    Acknowledgements 
    References

• Syed Akhil(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India)
• Porala Jayanth Kumar(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India)
• Venkata Sai Sriram Mosali(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India, Department of Mechanical Engineering, Colorado State University, 430 N College Ave, Fort Collins, CO 80524, USA)
• V. G. Vasavi Dutt(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India)
• Satish Kasturi(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India)
• Bhanu Mullamuri(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India, Office of Information Technology, Department of Enterprise Technology, University of Alabama, Tuscaloosa, Alabama 35487, USA)
• Nagaprasad Puvvada(Department of Chemistry, VIT-AP University, Amaravathi, Andhra Pradesh 522237, India)
• Pravas Kumar Panigrahi(Department of Basic Sciences, Government College of Engineering, Kalahandi, Odisha 766003, India)
• Rama Krishna Chava(Department of Chemistry, College of Natural Sciences, Yeungnam University, 280 Daehak‑ro, Gyeongsan, Gyeongsangbuk‑do 38541, Republic of Korea)
• Basavaiah Chandu(Department of Nanotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh 522510, India)