Wet Chemical Synthesis of Molybdenum-Doped Amorphous TiO₂ Nanoparticles and Studies on Their Photochromic Properties

ABSTRACT

Undoped and (0.5–5 at%) molybdenum-doped TiO₂ nanoparticles were synthesized by a simple and scalable wet chemical method. The as-synthesized materials were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, electron paramagnetic resistance (EPR), and ultraviolet-visible (UV-Vis) spectroscopy techniques. XRD studies showed the formation of crystalline anatase phase of undoped TiO₂, whereas Mo-doped samples showed the formation of an amorphous phase. AFM studies showed the formation of spherical-shaped particles with a particle diameter of ∼23 nm in all samples. The photochromic behavior of these materials was studied by making their films in alkyd resin. Films of these materials showed a reversible photochromic color change from beige to brown on exposure to UV light. The coloration and bleaching process was recorded using UV-Vis diffuse reflectance spectroscopy. The maximum color change was observed in 2 at% Mo⁺⁶-doped nano-TiO₂. The photochromic mechanism of molybdenum-doped nano-TiO₂ was also examined using EPR spectroscopy.

KEYWORDS:

• amorphous molybdenum-doped nano-TiO₂
• wet chemical method
• photochromism

Acknowledgments

The authors thank Dr. R. P. Pant, Sc.E., NPL, Delhi, for help in EPR characterization and highly useful discussions. The authors also thank Amit Sadh, Sc.C., for his help in Raman characterization of samples.