https://doi.org/10.17113/ftb.63.02.25.8925

Supplement

Green Synthesis and Characterization of Silver Nanoparticles Using Rice (Oryza sativa) and Spent Coffee (Coffea robusta) Grounds from Agricultural Waste

Nithiskanna Nallusamy¹, Nurul Affifah Mohd Kamal Rufadzil¹, Jasvini Bala Murally^1#, Liam Jing Zhi^1#, Wan Nor Dalila Wan Fauzi², Hawa Dalily Mohd Jefri², Amirul Al-Ashraf Abdullah³, Seeram Ramakrisha⁴ and Sevakumaran Vigneswari^1,5*

¹Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia

²Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia

³School of Biological Science, Universiti Sains Malaysia, Pulau Pinang, Malaysia

⁴Center for Nanotechnology and Sustainability, National University of Singapore, 119260 Singapore

⁵Ocular Infections and Antimicrobials Research Group, Singapore Eye Research Institute, Singapore

Copyright © 2024 This is a Diamond Open Access article published under CC-BY licence. Copyright remains with the authors, who grant third parties the unrestricted right to use, copy, distribute and reproduce the article as long as the original author(s) and source are acknowledged.

Article history:

Received: 29 October 2024

Accepted: 30 April 2025

Keywords:

agricultural waste; green synthesis; rice husks; spent coffee grounds; silver nanoparticles  

The content of this publication has not been approved by the United Nations and does not reflect the views of the United Nations or its officials or Member States.

Summary:

Research background. Agricultural waste was utilised to synthesise silver nanoparticles (AgNPs) via green synthesis, a sustainable alternative to traditional synthesis techniques that use hazardous chemicals and extensive processing. AgNPs were produced from spent coffee grounds, Coffea robusta, and rice husks, Oryza sativa, both prevalent agricultural wastes rich in bioactive substances including proteins, flavonoids, and phenolic acids, which act as natural reducing agents.

Experimental approach. The formation and stability of AgNPs were confirmed using various methods. UV-Vis spectroscopy showed surface plasmon resonance (SPR) peaks at 450 nm, indicating the formation of AgNPs, while Fourier transform infrared spectroscopy (FTIR) identified functional groups responsible for the bio-reduction and stabilisation of the nanoparticles. X-ray diffraction spectroscopy (XRD) confirmed the crystalline, face-centred cubic structure. Zeta potential analysis showed a stable dispersion and particle size analysis showed a consistent size distribution. The antibacterial activity of AgNPs was evaluated by testing their effectiveness against both Gram-positive and Gram-negative bacteria.

Results and conclusions. The AgNPs were synthesised using spent coffee grounds and rice husks, which are rich in biomolecules that serve as effective reducing andstabilising agents. FTIR analysis identified functional groups involved in the reduction and stabilisation of nanoparticles, while XRD confirmed their face-centred cubic (FCC) crystalline structure. Zeta potential measurements showed stable dispersions with particle sizes of AgNPs obtained using spent coffee grounds of approx. 187 nm and of AgNPs obtained using rice husks of 198 nm. The synthesised AgNPs also showed strong antibacterial activity against both Gram-positive and Gram-negative bacteria.

Novelty and scientific contribution. AgNPs were obtained by green synthesis using agricultural waste such as spent coffee grounds and rice husks as natural reducing and stabilising agents. This study highlights the innovative use of biomolecule-rich materials to generate stable AgNPs with strong antibacterial properties and provides a sustainable basis for further development of nanotechnological applications.

 
^#Both authors contributed equally.