Effect of Chromium Doping on Visible Light Absorption of Nanosized Titania Sol-Gel

Abstract

Visible light absorption of TiO2 can be induced by the addition of transition metal impurities. However, many dissimilar results have been reported about this subject and there are various interpretations about the origin of these absorption features. In this work, samples of chromium-doped titania (TiO2-Cr) with different dopant contents (0.1, 0.5, 1.0 and 5.0 wt. %) were prepared by a sol-gel method. Their particle size was determined by dynamic light scattering and it was on the nanometer scale (18 nm). X-ray powder diffraction and Raman spectroscopy showed only the presence of anatase phase in all samples. X-ray photoelectron spectroscopy reveals that the oxidation state of chromium in the prepared materials is different than in the dopant precursor. This change can be associated to the oxidative gelling conditions used in the materials preparation. UV VIS diffuse reflectance spectroscopy showed that the chromium doping, until 1.0 wt. %, did not effectively narrow the TiO2 band-gap but it induces the visible light absorption probably through the formation of color centers.

Marimo-Bead-Supported Core–Shell Nanocomposites of Titanium Nitride and Chromium-Doped Titanium Dioxide as a Highly Efficient Water-Floatable Green Photocatalyst

“…Raman peaks are very sensitive to the local environment, and substitutional doping can significantly influence the phonon vibrations. Therefore, the Cr-TiO 2 shows broad Raman peaks compared to the TiO 2 due to the substitutional doping of Ti 4+ with Cr 3+ . − The Raman spectra of TiN NPs (Figure S6, SI) show the characteristic peaks at 235, 439, and 607 cm –1 , which can be assigned to acoustic and optical modes of TiN . The Raman peaks of TiN at 235 and 439 cm –1 shift to 258 and 406 cm –1 for TSCT, respectively.…”

Noble metal-modified octahedral anatase titania particles with enhanced activity for decomposition of chemical and microbiological pollutants

“…Metallic deposits under UV irradiation work as an electron sink that inhibits the recombination of charge carriers. Under visible light irradiation, either narrowing of the band-gap [42] , [43] , [44] or energy/electron transfer from the modifier to titania [45] , [46] , [47] causes a visible light response. Recently, modification of titania with NPs of noble metals that have a visible light absorption property due to localized surface plasmon resonance (LSPR) has been extensively studied, and such materials obtained are called plasmonic photocatalysts.…”

Screening of factors influencing the photocatalytic activity of TiO2:Ln (Ln=La, Ce, Pr, Nd, Sm, Eu and Gd) in the degradation of dyes

“…The band gap energy (E g ) was estimated from the spectra in percent reflectance mode by means of the Kubelka-Munk function: F(R) = (1ÀR) 2 /2R, where R is the diffuse reflectance, through the corresponding Tauc plots: (F(R) Â E) 1/2 and E is the energy of absorbed light, by extrapolation of the straight line to the abscissa [21][22][23]. The visible light absorption (VLA) was calculated from the spectra of absorbance mode by numerical integration in the range of 400-700 nm [24,25]. All Table 1 It shows the experimental design with related factors and responses.…”