Green synthesis of titanium dioxide nanoparticles using green tea ( <i>Camellia sinensis</i> ) extract: Characteristics and applications

Abstract Titanium dioxide (TiO 2 ) nanoparticles were successfully synthesized using titanium isopropoxide as a substrate and green tea extract as a reducing agent in the synthesis process. The structural characteristics of TiO 2 were analyzed using advanced techniques such as scanning electron microscope, energy dispersive X-ray, X-ray diffraction analysis, and N 2 adsorption/desorption isotherm. TiO 2 nanoparticles with a crystal size of 21.04 nm were calculated using the Debye–Scherer equation, indicating a dominant anatase structure. The synthesized TiO 2 nanomaterial exhibited a spherical shape and formed aggregates, with a surface area of 18.33 m 2 ·g −1 . Additionally, the antibacterial activity of TiO 2 nanoparticles was evaluated using the disk diffusion method, and the minimum inhibitory concentration against gram-positive bacteria Staphylococcus aureus and gram-negative bacteria Escherichia coli was found to be 7.5 and 11.25 mg·mL −1 , respectively. In addition, the photocatalytic degradation of TiO 2 activates and generates free radicals such as ˙OH and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mi>˙</m:mi> <m:msubsup> <m:mrow> <m:mtext>O</m:mtext> </m:mrow> <m:mrow> <m:mn>2</m:mn> </m:mrow> <m:mrow> <m:mo>−</m:mo> </m:mrow> </m:msubsup> </m:math> \textdotaccent {\text{O}}_{2}^{-} , which have strong oxidizing abilities. These radicals break down the molecular structure and remove approximately 76% of tetracycline antibiotics. Incorporating TiO 2 in facial wash formulations significantly enhances the sun protection factor. Green synthesis of TiO 2 nanoparticles using Camellia sinensis extract is not only suitable for sustainable activities but also becomes a versatile material with great application potential in fields such as cosmetics, medicine, and environmental remediation.