In this work, hydrothermal methods and deep eutectic solvents were combined for the first time to prepare tungsten trioxide nanoparticles in an easy and green manner improving their optical and photochromic
properties. Characterization of the synthesized nanoparticles was performed via Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet visible spectroscopy, scanning electron microscopy, energy dispersive X-ray, transform electron microscopy, dynamic light scattering, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The average size of the spherical nanoparticles was ca. 1.83 nm as shown by TEM, and the nanoparticles exhibited high thermostability at least until 900 1C, and photostability and photosensitivity when they were exposed to UV light. Additionally, synthesized tungsten trioxide nanoparticles were found to be nontoxic with maximum cell viability observed even at 100 mg mL1, making them potential candidates for biomedical applications.
