Green synthesis of TiO2 nanoparticles using Echinops echinatus plant extract and its potential applications for photocatalytic dye degradation, 4-nitrophenol reduction, and antimicrobial activity

Abstract

Industrial wastewater poses a significant threat to human health and the environment. Numerous treatment methods have been developed to mitigate harmful compounds. The production of multifunctional titanium oxide nanoparticles (TiO₂-NPs) for wastewater treatment through green synthesis is a desirable alternative to conventional methods. This study reports using Echinops echinatus leaves (EES) as an effective bio-reductant for the green synthesis of TiO₂-NPs. A simple and eco-friendly process with low reaction time and temperature was adopted for the EES-mediated synthesis of TiO₂-NPs. Various spectroscopic and microscopic techniques were used to characterize the synthesized nanoparticles. The UV–visible spectrophotometer spectra showed an absorbance peak at 289 nm and a bandgap of 2.91 eV. SEM and XRD revealed the nanoparticles’ crystal nature, size, and spherical morphology. HR-TEM indicated an average particle size of 36 nm with a spherical shape. Energy-dispersive X-ray (EDX) spectra confirmed the presence of titanium. Fourier transform infrared (FTIR) spectroscopy identified the fundamental biomolecules responsible for reducing and stabilizing the TiO₂ nanoparticles. The synthesized nanoparticles were developed as photocatalysts for treating trypan blue dye under visible light irradiation, achieving a rapid decomposition rate with 84% degradation efficiency and catalyst reusability. The radical experiment that was studied identified h⁺ and OH* radicals as the more reactive species. The catalytic potential of EES-TiO₂ NPs was further examined for converting 4-nitrophenol to 4-aminophenol, with a 98% conversion rate in an alkaline medium. UV–vis spectroscopy showed a decrease rate of k = 0.011 min⁻¹ during the catalytic conversion. Additionally, EES-TiO₂ NPs demonstrated significant antibacterial effects on pathogenic bacteria, as measured by the zone of inhibition in the disc diffusion method. The findings suggest that the synthesized EES-TiO₂ nanoparticles hold promise for various environmental and antipathogenic applications.

Graphical Abstract

A schematic representation of the green synthesis of TiO₂ nanoparticles for photocatalysis and antimicrobial activity.