The green synthesis of inorganic nanoparticles (NPs) using biomaterials has garnered considerable attention in recent years because of its eco-friendly, non-toxic, simple, and low-cost nature. In this study, we synthesized NPs of noble metals, such as Ag and Au using an aqueous extract of a marine seaweed, Ecklonia cava. The formation of AgNPs and AuNPs was confirmed by the presence of surface plasmon resonance peaks in UV-Vis absorption spectra at approximately 430 and 530 nm, respectively. Various properties of the NPs were evaluated using characterization techniques, such as dynamic light scattering, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Phytochemicals in the seaweed extract, such as phlorotannins, acted as both reducing and stabilizing agents for the growth of the NPs. The green-synthesized AgNPs and AuNPs were found to exhibit high catalytic activity for the decomposition of organic dyes, including azo dyes, methylene blue, rhodamine B, and methyl orange.

Abstract
1. Introduction
2. Materials and methods
    2.1. Chemicals and reagents
    2.2. Preparation of EC extract
    2.3. Green synthesis of AgNPs and AuNPs
    2.4. Characterization of EC-AgNPs and EC-AuNPs
    2.5. Catalytic activity of AgNPs and AuNPs
3. Results and Discussion
    3.1. Green synthesis of EC-AgNPs and EC-AuNPsand UV-Vis spectral analysis
    3.2. DLS and HR-TEM analysis
    3.3. XRD analysis
    3.4. FT-IR spectral analysis
    3.5. Catalytic reduction of EC-AgNPs and -AuNPs
4. Conclusion
REFERENCES

• Beomjin Kim(Department of Nano Fusion Technology, Pusan National University, Busan 46241, Korea)
• Woo Chang Song(Department of Nano Fusion Technology, Pusan National University, Busan 46241, Korea)
• Sun Young Park(Bio-IT Fusion Technology Research Institute, Pusan National University, Busan 46241, Korea)
• Geuntae Park(Department of Nano Fusion Technology, Pusan National University, Busan 46241, Korea) Corresponding author