Researchers at the University of Agriculture Faisalabad in Pakistan have turned the leaves of the jamun tree, Syzygium cumini, into a green chemistry tool for making copper-doped zinc oxide nanoparticles, and the resulting particles showed measurable antibacterial and antifungal activity against plant pathogens. The study, published in the journal Bioscience Nanotechnology on 10 August 2026, describes an eco-friendly co-precipitation route in which an aqueous leaf extract acts as the reducing and capping agent, replacing the toxic reagents and organic solvents typical of conventional chemical synthesis.
The team prepared the extract by washing fresh leaves, shade-drying them for a week, grinding them to a powder, and heating the powder in distilled water at 45 to 60 degrees Celsius for 45 to 60 minutes before filtering and storing the liquid at 4 degrees Celsius. For pure zinc oxide nanoparticles, a 0.1 M zinc acetate dihydrate solution was stirred at 70 degrees Celsius while the leaf extract was added dropwise. Adjusting the pH to between 9 and 11 triggered a visible color change from green to brown, signaling nanoparticle formation. The precipitate was centrifuged at 12,000 revolutions per minute for 20 minutes, washed with deionized water, dried at 90 degrees Celsius, and calcined at 600 degrees Celsius for two hours.
To introduce copper, the researchers followed the same green co-precipitation procedure and then added a 5 percent weight-per-volume copper sulfate solution dropwise, turning the mixture a dark chocolate brown. The doped product was centrifuged, washed, dried, and calcined under identical conditions. According to the authors, the phytochemicals in the leaf extract, including polyphenols, flavonoids, tannins, and terpenoids, coordinate with zinc and copper ions, drive reduction and nucleation, and then stabilize the growing particles as natural capping agents, limiting aggregation before the calcination step removes the organic material.
Characterization confirmed the formation and doping of the particles. Ultraviolet-visible spectroscopy showed a sharp absorption peak at 378 nanometers for pure zinc oxide and a slightly red-shifted peak at 383 nanometers for the copper-doped material, a shift the authors attribute to changes in the electronic structure caused by copper incorporation, including impurity levels near the bands and sp-d exchange interactions between conduction band electrons and localized copper d-electrons. Fourier transform infrared spectroscopy identified the phytochemical signatures of the extract, with a broad O-H stretching band at 3429.4 reciprocal centimeters and C-H and C=O bands assigned to terpenoids, fatty acids, flavonoids, and phenolic acids, while strong zinc oxide lattice vibrations appeared between 500 and 600 reciprocal centimeters in both materials.
X-ray diffraction indexed the diffraction peaks of both samples to the hexagonal wurtzite structure of zinc oxide, matching the standard JCPDS card number 36-1451. Pure zinc oxide showed characteristic peaks at 2-theta values of 36.44, 63.03, 68.12, and 69.29 degrees, and the copper-doped sample exhibited slightly shifted peaks at 36.29, 62.89, 67.98, and 69.07 degrees, indicating successful incorporation of copper into the lattice with minor distortion but no change in crystal structure. Using the Debye-Scherrer equation, the team calculated an average crystallite size of about 18.67 nanometers for pure zinc oxide, which fell to about 16.25 nanometers after doping, suggesting that copper incorporation inhibits crystal growth and introduces lattice strain.
Dynamic light scattering measured a mean hydrodynamic diameter of 78 nanometers for pure zinc oxide and 86.07 nanometers for the doped particles, with polydispersity indices of 14.9 percent and 11.2 percent respectively, indicating that doping increased the average size while preserving dispersion uniformity. Zeta potential measurements told a complementary story: pure zinc oxide carried a surface potential of minus 16.98 millivolts with a standard deviation of 0.3 millivolts, while the doped particles were markedly more negative at minus 28.38 millivolts with a standard deviation of 0.9 millivolts, a change the authors link to dopant-induced surface chemistry, possibly through additional oxygen vacancies or altered surface hydroxyl groups.
Atomic force microscopy added a surface-level view. The average particle size measured by AFM was 48.45 nanometers for pure zinc oxide and 13.83 nanometers for the doped material, and the average surface roughness dropped from 2.093 nanometers to 1.824 nanometers with doping. Peak-to-valley height measurements also improved, with the highest peak falling from 148.219 nanometers to 24.572 nanometers and the deepest valley from 22.944 nanometers to 9.378 nanometers. The authors interpret these changes as evidence that copper incorporation disrupted regular crystal growth, yielding smaller, more compact structures with fewer surface irregularities, though they note that scanning or transmission electron microscopy would be needed for a fuller picture of morphology and aggregation.
The antimicrobial evaluation focused on two bacterial phytopathogens, Xanthomonas campestris and Clavibacter michiganensis, and two fungal pathogens, Aspergillus niger and Alternaria alternata, using agar well diffusion with ciprofloxacin and fluconazole as positive controls. At the highest tested concentration of 100 microliters, the copper-doped nanoparticles produced a maximum inhibition zone of 19.99 plus or minus 0.7 millimeters against Xanthomonas campestris and 28.37 plus or minus 0.7 millimeters against Clavibacter michiganensis, larger than the zones produced by the plant extract alone. Against the fungi, the doped nanoparticles achieved inhibition zones of 30.14 plus or minus 0.7 millimeters for Aspergillus niger and 28.12 plus or minus 0.6 millimeters for Alternaria alternata at 100 microliters, again exceeding the extract but remaining below fluconazole, which reached 33.83 plus or minus 0.8 millimeters against Aspergillus niger. Differences among treatments were statistically significant at p below 0.001 by Tukey test.
The authors propose that the enhanced activity of the doped nanoparticles arises from several converging mechanisms. Electrostatic attraction draws the particles to the negatively charged bacterial surface, increasing membrane permeability and disrupting integrity. Photo-induced excitation of zinc oxide in aqueous media generates electrons and holes that react with dissolved oxygen and water to produce reactive oxygen species, inflicting oxidative stress and causing leakage of nucleic acids, ions, proteins, and metabolites. Copper incorporation adds defect sites and oxygen vacancies that boost reactive oxygen production by reducing electron-hole recombination, and released copper and zinc ions can bind thiol groups in enzymes, interfere with DNA phosphate groups, and disrupt respiration and ATP synthesis. Against fungi, the particles adsorb onto the chitin and glycoprotein cell wall, weaken its structure, damage mitochondria, and fragment DNA.
The study’s authors are careful to frame the findings within their limits. The antimicrobial screen covered only two bacterial and two fungal phytopathogens, and advanced elemental and morphological techniques such as energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy were not performed. No in vivo safety or field efficacy data exist yet.
Subject of Research: Green synthesis of copper-doped zinc oxide nanoparticles using Syzygium cumini leaf extract and their antimicrobial activity against plant pathogens
Article Title: Green synthesis of Cu-Doped ZnO nanoparticles using Syzygium cumini leaf extract and their antimicrobial evaluation
Article References: Gulzar, R., Jahan, N., Gulzar, M. W., & Yasir, M. A. (2026). Green synthesis of Cu-Doped ZnO nanoparticles using Syzygium cumini leaf extract and their antimicrobial evaluation. Bioscience Nanotechnology, 2(1), Article 21. https://doi.org/10.1186/s44331-026-00028-4
Image Credits: AI Generated
DOI: 10.1186/s44331-026-00028-4
Keywords: green synthesis, copper-doped zinc oxide, Syzygium cumini, nanoparticles, antimicrobial activity, Xanthomonas campestris, Clavibacter michiganensis, Aspergillus niger, Alternaria alternata, phytochemicals, X-ray diffraction, reactive oxygen species
News Source: Gregory Coleman. (October 29, 2026). Jam Tree Leaf Extract Yields Copper-Doped Zinc Oxide Nanoparticles With Antimicrobial Power. Scienmag.
