Citrus Peel Extracts Yield Titanium Dioxide Nanoparticles That Degrade Dye and Curb Bacteria

A new study reports a plant-based route to titanium dioxide nanoparticles: peel extracts from three citrus fruits were used as the reducing agents in the synthesis of TiO2 nanoparticles from titanium (IV) isopropoxide. The work, published open access in Discover Materials, tested extracts of Mandarin (Citrus reticulata), Sweet Orange (Citrus sinensis) and Lime (Citrus aurantifolia) and evaluated the resulting materials both as photocatalysts for dye removal and as antibacterial agents.

Using UV-Vis spectrophotometry to track total flavonoid content, the researchers found that deionized water combined with a three-hour extraction time gave the maximum yield. This simple, solvent-light condition set the stage for the synthesis step.

To make the nanoparticles, varying volumes of each peel extract—1, 5, 10, 15 and 20 milliliters—were reacted with titanium (IV) isopropoxide. Across all three extracts, a 10 milliliter volume proved optimal for successful synthesis. The samples prepared under this condition were labeled TiO2-10-ME for mandarin, TiO2-10-SE for sweet orange and TiO2-10-LE for lime.

The measured crystallite sizes were remarkably small: 1.918 nanometers for the mandarin-derived material, 2.460 nanometers for the sweet orange version and 2.591 nanometers for the lime-derived sample.

Initial Fourier-transform infrared spectroscopy analysis revealed residual organic impurities left over from the plant extracts, so the team turned to calcination to clean the materials. Heating at 350 degrees Celsius removed these impurities, but the time required differed sharply among the three samples: 72 hours for the mandarin-derived nanoparticles, 6 hours for the sweet orange version and 24 hours for the lime-derived material.

Photocatalytic performance was assessed by monitoring the removal of methylene blue, a model dye pollutant, under ultraviolet irradiation. Among all the samples, the lime-derived nanoparticles calcined at 350 degrees Celsius for 24 hours—designated TiO2-10-LE-24 h—performed best, achieving an apparent removal of 92.95 percent of the dye after 50 minutes of UV exposure.

The same lime-derived material also stood out in antibacterial testing. Using the disc diffusion method, the researchers evaluated activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. TiO2-10-LE-24 h produced the largest inhibition zones, measuring 9.95 ± 0.34 millimeters against E. coli and 10.41 ± 0.22 millimeters against S. aureus, demonstrating effective inhibition of both bacterial types in this assay.

The authors suggest that these citrus-mediated nanoparticles highlight a route toward sustainable environmental remediation and potential biomedical applications. Because the study reports apparent dye removal under controlled UV irradiation and inhibition zones from disc diffusion assays, further work would be needed to translate these laboratory results into water-treatment systems or clinical uses. The findings show that citrus peel extracts can serve as reducing agents in nanomaterial synthesis, with the choice of fruit and the calcination schedule tunable levers for controlling purity, crystal size and performance.

Subject of Research: Green synthesis of titanium dioxide nanoparticles from citrus peel extracts for photocatalytic dye removal and antibacterial applications

Article Title: Green synthesis of Titanium (IV) oxide nanoparticles via citrus fruit peel for antibacterial and photocatalytic applications

Article References: Meedech, W., Sakulpeeb, N., Koetniyom, W., Chutipaijit, S., & Wirunchit, S. (2026). Green synthesis of Titanium (IV) oxide nanoparticles via citrus fruit peel for antibacterial and photocatalytic applications. Discover Materials. https://doi.org/10.1007/s43939-026-01050-2

Image Credits: AI Generated

DOI: 10.1007/s43939-026-01050-2

Keywords: green synthesis, titanium dioxide nanoparticles, citrus peel, flavonoids, photocatalysis, methylene blue, antibacterial, anatase, X-ray diffraction, calcination, E. coli, S. aureus