Biogenic Synthesis of ZnO-CuO Heterojunction Nanoparticles Using Callistemon Citrinus Plant Extract and Evaluation of Photocatalytic Activity
Keywords:
Nanotechnology, Green synthesis, Heterojunction Nanoparticles, Callistemon citrinus, Photocatalytic activityAbstract
The present study reports the biogenic synthesis of ZnO, CuO, and ZnO–CuO heterojunction nanoparticles using aqueous leaf extract of Callistemon citrinus as a reducing and stabilizing agent. The green synthesis approach was adopted as an environmentally friendly and sustainable alternative to conventional chemical methods. The synthesized nanoparticles were characterized using UV–Visible (UV–Vis) and Fourier Transform Infrared (FTIR) spectroscopy. UV–Vis analysis confirmed the formation of ZnO, CuO, and ZnO–CuO nanoparticles through their characteristic absorption features, while FTIR studies revealed the presence of phytochemical functional groups responsible for nanoparticle stabilization and confirmed the formation of Zn–O and Cu–O bonds. The photocatalytic performance of the synthesized materials was evaluated through the degradation of Methylene Blue (MB) dye under natural sunlight irradiation. Among the investigated photocatalysts, the ZnO–CuO heterojunction nanoparticles exhibited superior photocatalytic activity, achieving a maximum degradation efficiency of 85.87% after 120 min of irradiation, compared to 61.88% and 59.64% for ZnO and CuO nanoparticles, respectively. The enhanced photocatalytic performance of the heterojunction nanocomposite was attributed to improved charge separation, reduced electron–hole recombination, and enhanced visible-light absorption. The results demonstrate that biogenically synthesized ZnO–CuO heterojunction nanoparticles are efficient photocatalysts with significant potential for environmental remediation and wastewater treatment applications.
References
R. Ahmed, et al., “Green synthesis methods for nanoparticles: Principles, biological routes, and physicochemical approaches toward sustainable nanotechnology,” Next Materials, vol. 11, p. 101929, 2026.
S. Malik, K. Muhammad, and Y. Waheed, “Nanotechnology: A revolution in modern industry,” Molecules, vol. 28, no. 2, p. 661, 2023.
I. Hussain, N. B. Singh, A. Singh, H. Singh, and S. C. Singh, “Green synthesis of nanoparticles and its potential application,” Biotechnology Letters, vol. 38, no. 4, pp. 545–560, 2016.
S. Ying, et al., “Green synthesis of nanoparticles: Current developments and limitations,” Environmental Technology & Innovation, vol. 26, p. 102336, 2022.
X. Zhao, et al., “An overview of preparation and applications of stabilized zero-valent iron nanoparticles for soil and groundwater remediation,” Water Research, vol. 100, pp. 245–266, 2016.
Y. Wang, et al., “Synthesis of iron oxide nanoparticles using a freshly-made or recycled imidazolium-based ionic liquid,” Green Chemistry, vol. 9, no. 10, pp. 1051–1056, 2007.
D. Horwat, et al., “Chemistry, phase formation, and catalytic activity of thin palladium-containing oxide films synthesized by plasma-assisted physical vapor deposition,” Surface and Coatings Technology, vol. 205, pp. S171–S177, 2011.
F. K. Alsammarraie, et al., “Green synthesis of silver nanoparticles using turmeric extracts and investigation of their antibacterial activities,” Colloids and Surfaces B: Biointerfaces, vol. 171, pp. 398–405, 2018.
A. A. Firoozi, A. A. Firoozi, and M. R. Maghami, “Transformative impacts of nanotechnology on sustainable construction: A comprehensive review,” Results in Engineering, vol. 26, p. 104973, 2025.
K. Parveen, V. Banse, and L. Ledwani, “Green synthesis of nanoparticles: Their advantages and disadvantages,” in AIP Conference Proceedings, vol. 1724, no. 1. Melville, NY, USA: AIP Publishing, 2016.
S. T. Karam and A. F. Abdulrahman, “Green synthesis and characterization of ZnO nanoparticles by using thyme plant leaf extract,” Photonics, vol. 9, no. 8, p. 594, 2022.
C. Jayaseelan, et al., “Novel microbial route to synthesize ZnO nanoparticles using Aeromonas hydrophila and their activity against pathogenic bacteria and fungi,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 90, pp. 78–84, 2012.
A. F. Abdulrahman, “The effect of different substrate-inclined angles on the characteristic properties of ZnO nanorods for UV photodetectors applications,” Journal of Materials Science: Materials in Electronics, vol. 31, no. 17, pp. 14357–14374, 2020.
R. Dobrucka and J. Długaszewska, “Biosynthesis and antibacterial activity of ZnO nanoparticles using Trifolium pratense flower extract,” Saudi Journal of Biological Sciences, vol. 23, no. 4, pp. 517–523, 2016.
M. Anbuvannan, et al., “Synthesis, characterization and photocatalytic activity of ZnO nanoparticles prepared by biological method,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 143, pp. 304–308, 2015.
A. F. Abdulrahman, “The influence of various reactants in the growth solution on the morphological and structural properties of ZnO nanorods,” Passer Journal of Basic and Applied Sciences, vol. 2, no. 2, pp. 69–75, 2020.
B. Bhushan, et al., “Photodegradation of Methylene Blue dye by powders of Ni–ZnO floweret consisting of petals of ZnO nanorod around Ni-rich core,” Materials Chemistry and Physics, vol. 253, p. 123394, 2020.
A. Chauhan, et al., “Photocatalytic dye degradation and antimicrobial activities of pure and Ag-doped ZnO using Cannabis sativa leaf extract,” Scientific Reports, vol. 10, no. 1, p. 7881, 2020.
R. A. Basit, et al., “Successive photocatalytic degradation of Methylene Blue by ZnO, CuO and ZnO/CuO synthesized from Coriandrum sativum plant extract via green synthesis technique,” Crystals, vol. 13, no. 2, p. 281, 2023.
[20] M. Hafeez, et al., “Populus ciliata mediated synthesis of Copper oxide nanoparticles for potential biological applications,” Materials Research Express, vol. 6, no. 5, p. 055043, 2019.
J. Khan, et al., “In-situ synthesis of CuO nanoparticles in P (NIPAM-co-AAA) microgel, structural characterization, catalytic and biological applications,” Arabian Journal of Chemistry, vol. 11, no. 6, pp. 897–909, 2018.
X. Han, S. Yang, and M. Schröder, “Porous metal–organic frameworks as emerging sorbents for clean air,” Nature Reviews Chemistry, vol. 3, no. 2, pp. 108–118, 2019.
J. Della Rocca, D. Liu, and W. Lin, “Nanoscale metal–organic frameworks for biomedical imaging and drug delivery,” Accounts of Chemical Research, vol. 44, no. 10, pp. 957–968, 2011.
S. N. Vavilapalli, et al., “Green synthesis of CuO nanoparticles using Ixora chinensis leaf extract for photocatalytic decolourisation of Rhodamine B and antibacterial performance,” Next Nanotechnology, vol. 9, p. 100463, 2026.
A. Chakravorty and S. Roy, “A review of photocatalysis, basic principles, processes, and materials,” Sustainable Chemistry for the Environment, vol. 8, p. 100155, 2024.
S. M. Botsa and K. Basavaiah, “Removal of nitrophenols from wastewater by monoclinic CuO/RGO nanocomposite,” Nanotechnology for Environmental Engineering, vol. 4, no. 1, p. 1, 2019.
E. Arulkumar, S. S. Shree, and S. Thanikaikarasan, “Photocatalytic degradation efficiency of Rhodamine-B for CuO/CdO nanosheets attained through simple co-precipitation method,” Results in Chemistry, vol. 6, p. 101169, 2023.
J. A. Rodriguez, et al., “The behavior of mixed-metal oxides: Structural and electronic properties of Ce₁₋ₓCaₓO₂ and Ce₁₋ₓCaₓO₂₋ₓ,” The Journal of Chemical Physics, vol. 119, no. 11, pp. 5659–5669, 2003.
Y. Wang, et al., “Structural and photoelectrocatalytic characteristic of ZnO/ZnWO₄/WO₃ nanocomposites with double heterojunctions,” Physica E: Low-Dimensional Systems and Nanostructures, vol. 43, no. 1, pp. 503–509, 2010.
H. R. Arandiyan and M. Parvari, “Studies on mixed metal oxides solid solutions as heterogeneous catalysts,” Brazilian Journal of Chemical Engineering, vol. 26, no. 1, pp. 63–74, 2009.
C. B. Ong, L. Y. Ng, and A. W. Mohammad, “A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications,” Renewable and Sustainable Energy Reviews, vol. 81, pp. 536–551, 2018.
R. Kumar, et al., “Antimicrobial properties of ZnO nanomaterials: A review,” Ceramics International, vol. 43, no. 5, pp. 3940–3961, 2017.
K. Qi, et al., “Review on the improvement of the photocatalytic and antibacterial activities of ZnO,” Journal of Alloys and Compounds, vol. 727, pp. 792–820, 2017.
K. Ahmad, et al., “Theoretical investigations on Copper-catalyzed C–N cross-coupling reaction between aryl chlorides and amines,” Computational and Theoretical Chemistry, vol. 1134, pp. 1–7, 2018.
A. Dey, “Semiconductor metal oxide gas sensors: A review,” Materials Science and Engineering: B, vol. 229, pp. 206–217, 2018.
J. Singh, G. Kaur, and M. Rawat, “A brief review on synthesis and characterization of Copper oxide nanoparticles and its applications,” Journal of Bioelectronics and Nanotechnology, vol. 1, no. 9, pp. 10–13, 2016.
J. R. Peralta-Videa, et al., “Plant-based green synthesis of metallic nanoparticles: Scientific curiosity or a realistic alternative to chemical synthesis?,” Nanotechnology for Environmental Engineering, vol. 1, no. 1, p. 4, 2016.
Z. Razzaq, et al., “Photocatalytic and antibacterial potency of titanium dioxide nanoparticles: A cost-effective and environmentally friendly media for treatment of air and wastewater,” Catalysts, vol. 11, no. 6, p. 709, 2021.
S. S. Mehta, et al., “RGO/WO₃ hierarchical architectures for improved H₂S sensing and highly efficient solar-driving photo-degradation of RhB dye,” Scientific Reports, vol. 11, no. 1, p. 5023, 2021.
N. Singh, et al., “Dual functional Ta-doped electrospun TiO₂ nanofibers with enhanced photocatalysis and SERS detection for organic compounds,” ACS Applied Materials & Interfaces, vol. 9, no. 34, pp. 28495–28507, 2017.
B. Balasubramaniam, et al., “Engineering of transition metal dichalcogenide-based 2D nanomaterials through doping for environmental applications,” Molecular Systems Design & Engineering, vol. 4, no. 4, pp. 804–827, 2019.
P. Kar, et al., “Interfacial engineering of Fe₂O₃@BOC heterojunction for efficient detoxification of toxic metal and dye under visible light illumination,” Journal of Environmental Chemical Engineering, vol. 7, no. 1, p. 102843, 2019.
P. Kar, et al., “Semiconductor based photocatalysts for detoxification of emerging pharmaceutical pollutants from aquatic systems: A critical review,” Nano Materials Science, vol. 3, no. 1, pp. 25–46, 2021.
Z. S. Gharibvand, et al., “Green synthesis of silver nanoparticles using Callistemon citrinus leaf extract and evaluation of its antibacterial activity,” pp. fa151–fa163, 2022.
E. Ismail, et al., “Comparative study of Callistemon citrinus (bottlebrush) and Punica granatum (pomegranate) extracts for sustainable synthesis of silver nanoparticles and their oral antimicrobial efficacy,” Nanomaterials, vol. 14, no. 11, p. 974, 2024.
D. Hassan, et al., “Biosynthesis of pure hematite phase magnetic iron oxide nanoparticles using floral extracts of Callistemon viminalis (bottlebrush): Their physical properties and novel biological applications,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 46, suppl. 1, pp. 693–707, 2018.
F. Kurul, B. Doruk, and S. N. Topkaya, “Principles of green chemistry: Building a sustainable future,” Discover Chemistry, vol. 2, no. 1, p. 68, 2025.
R. Selvaraj, K. R. Kalimuthu, and V. Kalimuthu, “A type-II MoS₂/ZnO heterostructure with enhanced photocatalytic activity,” Materials Letters, vol. 243, pp. 183–186, 2019.
Z. R. Parekh, et al., “CuO nanoparticles—synthesis by wet precipitation technique and its characterization,” Physica B: Condensed Matter, vol. 610, p. 412950, 2021.
A. Nisar, et al., “Synthesis and characterization of ZnO decorated reduced graphene oxide (ZnO-rGO) and evaluation of its photocatalytic activity toward photodegradation of Methylene Blue,” Environmental Science and Pollution Research, vol. 29, no. 1, pp. 418–430, 2022.
M. Saeed, et al., “Photocatalysis: An effective tool for photodegradation of dyes—A review,” Environmental Science and Pollution Research, vol. 29, no. 1, pp. 293–311, 2022.
M. Saeed, et al., “Synthesis of Ag–Fe₃O₄ nanoparticles for degradation of Methylene Blue in aqueous medium,” Bulletin of the Chemical Society of Ethiopia, vol. 34, no. 1, pp. 123–134, 2020.
P. Dwivedi, I. Jatrana, A. U. Khan, A. A. Khan, H. Satiya, M. Khan, I. S. Moon, and M. Alam, “Photoremediation of methylene blue by biosynthesized ZnO/Fe₃O₄ nanocomposites using Callistemon viminalis leaves aqueous extract: A comparative study,” Nanotechnology Reviews, vol. 10, no. 1, pp. 1912–1925, 2021, doi: 10.1515/ntrev-2021-0117.
A. Fouda, S. M. Alsharif, A. M. Eid, A. S. Albalawi, M. A. Amin, F. A. Alraddadi, A. M. Almutrafy, D. A. Bukhari, N. A. Algamdi, and M. A. Abdel-Rahman, “Photocatalytic activity of green-synthesized semiconductor CuO/ZnO nanocomposites against organic dye: An assessment of antimicrobial and cytotoxicity investigations,” Catalysts, vol. 15, no. 12, Art. no. 1096, 2025, doi: 10.3390/catal15121096.
