Effect of copper ions concentration on the particle size of alginate-stabilized Cu2O-Cu nanocolloids and its antibacterial activity against rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae)

Doan Thi Bich Ngoc, Du Bui Duy, Le Nghiem Anh Tuan, Bui Dinh Thach, Tran Phuoc Tho and Dang Van Phu

Abstract

In this study, nano Cu₂O-Cu/alginate was synthesised by the chemical reduction of tetra-amminecopper (II) ion complexes soluble using hydrazine as a reducing agent and alginate as a stabiliser. The influence of various copper ion concentrations on particle size and morphology of produced nano Cu₂O-Cu/alginate was investigated. The transmission electron microscopy (TEM) analysis and X-ray diffraction (XRD) measurement revealed that the synthesised nano Cu₂O-Cu/alginate was mostly composed of Cu₂O-Cu in the form of a Cu₂O@Cu core–shell structure with particle sizes of 4.2, 5.3, and 8.4 nm for 60, 80, and 100 mM of copper ion initial concentrations, respectively. The obtained nano Cu₂O-Cu/alginate exhibited high antibacterial activity against Xanthomonas oryzae pv. Oryzae (Xanthomonas OO). The results showed that the nano Cu₂O-Cu/alginate containing 30 mg.l⁻¹ of copper ions completely inhibited the growth of Xanthomonas OO bacteria, which are responsible for the rice leaf blight disease. Nano Cu₂O-Cu/alginate materials can be used as a fungicide to replace toxic agro-chemicals and potentially applied to the development of sustainable agricultural production.