ached 55 mm (61.1 % inhibition) The antifungal efficiency increased to ~100 % at Cu concentartion of 30 ppm Based on the results in figure 4, ED50 (effective dose for 50 % inhibition) of Cu on N dimidiatum was found to be 20.8 ppm The antifungal effect of AgNPs/chitosan on N dimidiatum in the dragon fruit plants was also investigated by Phan Ngoc et al (2018) with highest inhibitory effect at 10 ppm Ag and 2% chitosan.[24] In addition, Du et al (2015) reported that oligochitosan against N dimidiatum with EC50 = 51.5 ppm.[14] Beside, nSiO2-OC also showed high efficiency in controlling brown spot disease on dragon fruit plants caused by N dimidiatum fungal.[25] Figure 4: The antifungal effect of Cu2O-Cu NPs/alginate on N dimidiatum after days of incubation Dhanasekaran, N Thajuddin and A Panneerselvam), published by Intech, Rijecka, Croatia, 257-278, 2012 CONCLUSION In this study, we have prepared the Cu2O-Cu NPs/alginate colloidal solution with high concentration of 5,000 ppm Cu, the average particle size of 5.4±0.4 nm, the particle size distribution in a narrow range The Cu2O-Cu NPs/alginate product exhibited highly antifungal efficiency (~100 %), for the growth of N dimidiatum causing brown spot disease on dragon fruit plant at 30.0 ppm Cu concentration The results of this study revealed that Cu2O-Cu NPs/alginate is a potential material used as a fungicide in sustanable agriculture production L Xiong, Z.-H Tong, J.-J Chen, L.-L Li, H.-Q Yu Morphology-dependent antimicrobial activity of Cu/Cu O nanoparticles, Ecotoxicology, 2015, 24 (10), 2067-2072 K Giannousi, G Sarafidis, S Mourdikoudis, A Pantazaki, C Dendrinou-Samara Selective synthesis of Cu2O and Cu/Cu2O NPs: antifungal activity to yeast saccharomyces cerevisiae and DNA interaction, Inorg Chem., 2014, 53(18), 9657-9666 N Gu, J Gao, H Li, Y Wu, Y Ma, K Wang Montmorillonite-supported with Cu2O nanoparticles for damage and removal of Microcystis aeruginosa under visible light, Appl Clay Sci., 2016, 132-133, 79-89 Acknowledgments This research is funded by Science and Technology Programme for the Sustainable Development of the Mekong Delta Region under grant number TNB.ĐT/14-19/C38 H Xu, W Wang, W Zhu Shape evolution and size- REFERENCES R D Rusjan, Copper in horticulture, In “Fungicides for Plant and Animal Diseases” (Eds by D controllable synthesis of Cu2O octahedra and their morphology-dependent photocatalytic properties, J Phys Chem B, 2006, 110(28), 13829–13834 Wick, S D Tilley Photovoltaic and photoelectrochemical solar energy conversion with Cu2O, J Phys Chem C, 2015, 119(47), 26243– 26257 © 2019 of Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co KGaA, Weinheim www.vjc.wiley-vch.de 322 khoa luan, tieu luan78 102 Tai lieu, luan van79 of 102 Vietnam Journal of Chemistry Bui Duy Du et al L Kiaune, N Singhasemanon Pesticidal copper (I) 17 P He, X Shen, H Gao Size-controlled preparation oxide: environmental fate and aquatic toxicity, Rev Environ Contam Toxicol., 2011, 213, 1-26 of Cu2O octahedron nanocrystals and studies on their optical absorption, J Colloid Interface Sci., 2005, 284, 510-515 S Huang, L Wang, L Liu, Y Hou, L Li Nanotechnology in agriculture, livestock, and aquaculture in China A review, Agron Sustain Dev., 2015, 35(2), 369–400 J Ren, W Wang, S Sun, L Zhang, L Wang, J Chang Crystallography facet-dependent antibacterial activity: the case of Cu2O, Ind Eng Chem Res., 2011, 50(17), 10366–10369 18 R A Khajouei, J Keramat, N R Hamdami, A.-V Ursu, C Delattre, C Laroche, C Gardarin, D Lecerf, J Desbrières, G Djelveh, P Michaud Extraction and characterization of an alginate from the Iranian brown seaweed Nizimuddinia zanardini, Inter J Biol Macromol., 2018, 118, 1073-1081 19 T A Fenoradosoa, G Ali, C.Delattre, C Laroche, antibacterial activity of cuprous oxide, Chem Commun., 2009, 9, 1076-1078 E Petit, A Wadouachi, P Michaud Extraction and characterization of an alginate from the brown seaweed Sargassum turbinarioides Grunow, J Appl Phycol., 2010, 22, 131-137 11 B D Du, D V Phu, L A Quoc, N Q Hien 20 J Diaz-Visurraga, C Daza, C Pozo A Becerra, C 10 P Huan, F Gao, Q Lu Morphology effect on Synthesis and investigation of antimicrobial activity of Cu2O nanoparticles/zeolite, J Nanoparticles, 2017, Article ID 7056864, 1-6 12 L H Thanh, N K B Tam, V T Nga, H T Thuy, T V Hai, H T Son, N N Quynh, N T H Nga Study on the possibility of using microorganisms as biological agents to control fungal pathogens Neoscytalidium dimidiatum causing disease of brown spots on the dragon fruit, J Viet Env., 2016, 8(1), 41-44 13 D V Phu, V T K Lang, N T K Lan, Ng N Duy, N D Chau, B D Du, B D Cam, N Q Hien Synthesis and antimicrobial effects of colloidal silver nanoparticles in chitosan by γ-irradiation, J Exp Nanosci., 2010, 5(2), 169-179 14 B D Du, L T K Dung, V N D Khoa, N D Thang, L N A Tuan Chitinase-induced resistance against Neoscytalidium dimidiatum on dragon trees: the effect of oligochitosan prepared by the heterogeneous degradation of chitosan with H2O2 under hydrothermal conditions, Vietnam J Chem., 2015, 53(2), 161-165 15 W.Songping, M Shuyuan Preparation of micron size copper powder with chemical reduction method, Mater Lett., 2006, 60, 2438-2442 16 J P Chen, L L Lim Key factors in chemical reduction by hydrazine for recovery of precious metals,Chemosphere, 2002, 49, 363-370 V Plessing, A Garcia Study on antibacterial alginate-stabilized copper nanopar-ticles by FT-IR and 2D-IR correlation spectroscopy, Int J Nanomedicine, 2012, 7, 3597-3612 21 S S Sawant, A D Bhagwat, C M Mahajan Novel facile technique for synthesis of stable cuprous oxide (Cu2O) nanoparticles–an ageing effect, J Nano Elec Phys., 2016, 8(1), 01036-01039 22 S M Badawy, R A El-Khashab, A A Nayl Synthesis, characterization and catalytic activity of Cu/Cu2O nanoparticles prepared in aqueous medium, Bull Chem React Eng Catal., 2015, 10(2), 169174 23 N Jardón-Maximino, M Pérez-Alvarez, R SierraÁvila, C A Ávila-Orta, E Jiménez-Regalado Oxidation of copper nanoparticles protected with different coatings and stored under ambient conditions, J Nanomater., 2018, Article ID 9512768, pages 24 U T Phan Ngoc, D H Nguyen Synergistic antifungal effect of fungicide and chitosan-silver nanoparticles on Neoscytalidium dimidiatum, Green Process Synth., 2018, 7(2), 132-138 25 L N A Tuan, B D Du, L D T Ha, L T K Dzung, D V Phu, N Q Hien Induction of chitinase and brown spot disease resistance by oligochitosan and nanosilica-oligochitosan in dragon fruit plants, Agri Res., 2018, 8(2), 184-190 Corresponding author: Bui Duy Du Institute of Applied Materials Science Vietnam Academy of Science and Technology 1A TL29 Str., Thanh Loc ward District 12, Ho Chi Minh City 700000, Viet Nam E-mail: vina9802@gmail.com khoa luan, tieu luan79 of 102 © 2019 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co KGaA, Weinheim www.vjc.wiley-vch.de 323 ... 363-370 V Plessing, A Garcia Study on antibacterial alginate- stabilized copper nanopar-ticles by FT-IR and 2D-IR correlation spectroscopy, Int J Nanomedicine, 2012, 7, 3597-3612 21 S S Sawant, A... (Cu2O) nanoparticles–an ageing effect, J Nano Elec Phys., 2016, 8(1), 01036-01039 22 S M Badawy, R A El-Khashab, A A Nayl Synthesis, characterization and catalytic activity of Cu/Cu2O nanoparticles... Cam, N Q Hien Synthesis and antimicrobial effects of colloidal silver nanoparticles in chitosan by γ-irradiation, J Exp Nanosci., 2010, 5(2), 169-179 14 B D Du, L T K Dung, V N D Khoa, N D Thang,