Structural and optical properties of AgCl-sensitized TiO₂ (TiO₂ @AgCl) prepared by a reflux technique under alkaline condition

Propriedades estruturais e ópticas de TiO ₂ sensibilizado com AgCl (TiO ₂ @AgCl) preparado por técnica de refluxo em condição alcalina

Abstract

The AgCl-sensitized TiO₂ (TiO₂@AgCl) has been prepared from the precursor of TiO₂-rutile type which on its surface adsorb chloride anion (Cl^-) and various amounts of silver using AgNO₃ as starting material: AgNO₃/(AgNO₃+TiO₂) mass ratio of 0.00, 1.14, 3.25, 6.38 and 10.32%. Reflux under alkaline condition was the employed technique. All samples were characterized by X-ray diffraction (XRD) and diffuse reflectance UV-vis spectroscopy. The sample without the addition of AgNO₃ was analyzed by scanning electron microscope and surface area analyzer. The morphology of the sample showed a distribution of microspheres of approximately 0.5 to 1.0 µm and the specific surface area was 68 m²/g. XRD patterns indicated that the sample without the addition of AgNO₃ contained two types of TiO₂: rutile (major) and anatase (minor), whereas the samples with the addition of AgNO₃ consisted of one phase of AgCl and two types of TiO₂: rutile and anatase. The bandgaps of the samples were in the range of 2.97 to 3.24 eV, which were very close to the bandgap of intrinsic TiO₂ powder. The presence of 0.8, 2.6 and 4.4 wt% of AgCl in each sample resulted in an additional bandgap in visible light region of 1.90, 1.94 and 2.26 eV, respectively, whereas the presence of 9.4 wt% of AgCl in the sample resulted in two bandgaps in visible light region of 1.98 and 1.88 eV.

Keywords:
TiO₂; anatase; rutile; AgCl; bandgap; alkaline condition