Nanostructured TiO₂ Films with 2 eV Optical Gap

Abstract

product, yielding phenylene-modified hybrid mesoporous ethenylenesilica (Ph-HME). The Ph-HME was then sulfonated by heating at 80 C for 3 days in concentrated H 2 SO 4 . The solid was recovered and washed in water at 80 C for 6 h. The washing treatment was repeated twice, and the final product was dried at room temperature to afford Ph±SO 3 H HME.Acid-Catalyzed Reaction: The esterification of acetic acid and pinacol±pinacolone rearrangement were employed as test reactions to examine the acid properties of the prepared samples. Esterification of acetic acid was examined in the liquid phase as follows: 0.20 g of the catalyst was evacuated at 423 K for 1 h and then added to a mixture of acetic acid (0.10 mol) and ethanol (1.0 mol). The reaction was carried out at 343 K in an Ar atmosphere, and the liquid phase was analyzed using gas chromatography with capillary columns. Pinacol± pinacolone rearrangement was performed in the liquid phase as follows: 0.20 g of the catalyst was evacuated at 423 K for 1 h and then added to pinacol (42.3 mol) without the addition of solvent. The reaction was carried out at 403 K in an Ar atmosphere, and the liquid phase was analyzed using gas chromatography with capillary columns.Measurement: Nitrogen adsorption±desorption isotherms were measured at 77 K using a Micrometrics Coulter SA-3100 system. Prior to measurement, the samples were pretreated at 423 K for 3 h under vacuum to a final pressure of 1 10 ±5 torr (1 torr = 133 Pa). The Brunauer±Emmett±Teller (BET) surface area was estimated over a relative pressure (P/P 0 ) range of 0.05±0.30. The pore size distribution was obtained from an analysis of the adsorption branch of the isotherms using the Barrett±Joyner±Halenda (BJH) method. Solid-state 13 C and 29 Si CP-MAS NMR measurements were acquired on Bruker ASX200 and ASX400 spectrometers, respectively. The Larmor frequencies for 13 C and 29 Si were 50.3 and 79.5 MHz, respectively. The experimental parameters were as follows.13 C CP-MAS NMR: 4.0 kHz spin rate, 5 s recycle delay, 2 ms contact time, and 4.0 ls p/2 pulse width.29 Si CP-MAS NMR experiment: 4.0 kHz spin rate, 5 s recycle delay, 5 ms contact time, 5.9 ls p/2 pulse width. The chemical shifts of 13 C and 29 Si spectra were expressed with respect to neat tetramethylsilane.

Influence of doping on the photoactive properties of magnetron-sputtered titania coatings: Experimental and theoretical study

“…18,19 The nature of C-induced changes to the TiO 2 electronic band structure is controversial. Both band gap narrowing 20 and the formation of localized midgap states 21 have been proposed to account for the red shift of the optical absorption edge. The codoping of TiO 2 with C and N by Chen et al 22 using the sol-gel technique was also found to further enhance the photo-activity of TiO 2 towards visible light.…”

Density functional theory studies of doping in titania

“…However, the nature of C-induced modifications to the TiO 2 electronic band structure is controversial. Both band gap narrowing [27] and the formation of localized mid-gap states [28] have been proposed for the red-shift of the optical absorption edge. In addition, Sn-doped TiO 2 has also attracted much attention, with Sn-doped rutile TiO 2 reported to lead to a red-shift of the optical absorption edge [29], while other results indicate blue-shifting in Sn-doped anatase [30]; these experimental observations have been confirmed by our previous theoretical studies [31].…”

C ion-implanted TiO2 thin film for photocatalytic applications

“…16 C-doped TiO 2 , synthesized by flame pyrolysis of Ti sheets in a natural gas flame, displayed a lower band-gap than titania (2.32 versus 3.00 eV). 17 Even if there are several works in the literature focused on C-doped titania, [17][18][19][20] and on doped TiO 2 by the ion-implantation process, 2,6,10,11,14 there is not, to our knowledge, any study on the effects of C doping by ion implantation. The advantage of the ion-implantation process is the outstanding control and repeatability of the implanted fluence and energy.…”