“…In the ESR spectrum of N−Si(0.2)−TiO 2 measured under the dark and evacuated conditions (Figure a), a small triplet signal (triplet-1) centered on g 1 = 1.999 ( A 1 = 32.2 G) was observed. This triplet signal is due to the N species adsorbed on the surface. , On visible-light irradiation (Figure b), a large triplet signal (triplet-2) centered on g 2 = 2.003 ( A 2 = 32.3 G) appeared. Triplet-2 is assigned to the paramagnetic N species doped in the TiO 2 lattice. − The spectrum observed in the dark (Figure a) was apparently different from those reported previously where both triplet-1 and triplet-2 were observed. , In the present study, the sample was kept in the dark for a relatively long period at room temperature, and therefore triplet-2 had disappeared before the ESR measurement.…”
Section: Resultsmentioning
confidence: 96%
“…This triplet signal is due to the N species adsorbed on the surface. , On visible-light irradiation (Figure b), a large triplet signal (triplet-2) centered on g 2 = 2.003 ( A 2 = 32.3 G) appeared. Triplet-2 is assigned to the paramagnetic N species doped in the TiO 2 lattice. − The spectrum observed in the dark (Figure a) was apparently different from those reported previously where both triplet-1 and triplet-2 were observed. , In the present study, the sample was kept in the dark for a relatively long period at room temperature, and therefore triplet-2 had disappeared before the ESR measurement. 9 ESR spectra of (a and b) N−Si(0.2)−TiO 2 and (c and d) Fe(0.001)−N−Si(0.2)−TiO 2 , measured at 123 K in vacuum under (a and c) a dark condition and (b and d) visible-light irradiation.…”
Nanocrystalline Si-doped titanias synthesized by the thermal reaction of titanium tetraisopropoxide and tetraethyl orthosilicate (glycothermal method) and three TiO 2 without Si modification, i.e., TiO 2 prepared by the glycothermal method, commercially available TiO 2 , P-25, and ST-01, were nitrified by heating in an NH 3 flow at high temperatures followed by annealing in air. Onto these samples, small amounts of Fe were loaded, and their photocatalytic activities for decomposition of acetaldehyde under visible-light irradiation were investigated. The Fe addition to non-nitrified samples gave no visible-light-induced photocatalytic activities. On the contrary, marked improvements were attained for the nitrified catalysts: the addition of small amounts of Fe (Fe/Ti of 0.005-0.7) to N-and Si-codoped titanias caused more than 10 times enhancement of the visible-light-induced photocatalytic activity. The electron spin resonance (ESR) studies of Fe-loaded N-and Si-codoped titanias suggested that Fe(III) species loaded on the nitrified samples accepted the photoexcited electrons and then transferred them to oxygen molecules. These processes facilitate electron-hole charge separation thus suppressing the recombination of the photogenerated electrons and holes and consequently contributed to the improvement in the photocatalytic activity.
“…In the ESR spectrum of N−Si(0.2)−TiO 2 measured under the dark and evacuated conditions (Figure a), a small triplet signal (triplet-1) centered on g 1 = 1.999 ( A 1 = 32.2 G) was observed. This triplet signal is due to the N species adsorbed on the surface. , On visible-light irradiation (Figure b), a large triplet signal (triplet-2) centered on g 2 = 2.003 ( A 2 = 32.3 G) appeared. Triplet-2 is assigned to the paramagnetic N species doped in the TiO 2 lattice. − The spectrum observed in the dark (Figure a) was apparently different from those reported previously where both triplet-1 and triplet-2 were observed. , In the present study, the sample was kept in the dark for a relatively long period at room temperature, and therefore triplet-2 had disappeared before the ESR measurement.…”
Section: Resultsmentioning
confidence: 96%
“…This triplet signal is due to the N species adsorbed on the surface. , On visible-light irradiation (Figure b), a large triplet signal (triplet-2) centered on g 2 = 2.003 ( A 2 = 32.3 G) appeared. Triplet-2 is assigned to the paramagnetic N species doped in the TiO 2 lattice. − The spectrum observed in the dark (Figure a) was apparently different from those reported previously where both triplet-1 and triplet-2 were observed. , In the present study, the sample was kept in the dark for a relatively long period at room temperature, and therefore triplet-2 had disappeared before the ESR measurement. 9 ESR spectra of (a and b) N−Si(0.2)−TiO 2 and (c and d) Fe(0.001)−N−Si(0.2)−TiO 2 , measured at 123 K in vacuum under (a and c) a dark condition and (b and d) visible-light irradiation.…”
Nanocrystalline Si-doped titanias synthesized by the thermal reaction of titanium tetraisopropoxide and tetraethyl orthosilicate (glycothermal method) and three TiO 2 without Si modification, i.e., TiO 2 prepared by the glycothermal method, commercially available TiO 2 , P-25, and ST-01, were nitrified by heating in an NH 3 flow at high temperatures followed by annealing in air. Onto these samples, small amounts of Fe were loaded, and their photocatalytic activities for decomposition of acetaldehyde under visible-light irradiation were investigated. The Fe addition to non-nitrified samples gave no visible-light-induced photocatalytic activities. On the contrary, marked improvements were attained for the nitrified catalysts: the addition of small amounts of Fe (Fe/Ti of 0.005-0.7) to N-and Si-codoped titanias caused more than 10 times enhancement of the visible-light-induced photocatalytic activity. The electron spin resonance (ESR) studies of Fe-loaded N-and Si-codoped titanias suggested that Fe(III) species loaded on the nitrified samples accepted the photoexcited electrons and then transferred them to oxygen molecules. These processes facilitate electron-hole charge separation thus suppressing the recombination of the photogenerated electrons and holes and consequently contributed to the improvement in the photocatalytic activity.
“…Early in 1968, Sancier ascribed the triplet as a solid state defect but did not identify the paramagnetic species [38]. Later, Iyengar et al assigned it to some paramagnetic nitrogen oxides (such as NO, NO 2 , NO 2 − , and NO 2 2− ) [39,40]. Recently, many studies have reported on the similar triplet signal of N-doped TiO 2 .…”
Section: Characteristics Of Relevant Samplesmentioning
“…). 58 In 2005, Prokes et al 10 reported the surface modification of TiO 2 nanostructures to incorporate nitrogen and form visible light absorbing titanium oxynitride centers, ESR performed on these samples identified a resonance at g = 2.0035, which was attributed to an oxygen hole center created near the surface of the nanocolloid. Recently, Giamello et al 59 ).…”
N-doped TiO 2 (anatase) with high visible light photoactivity was obtained by the thermal treatment of nanotube titanic acid (denoted as NTA) in an NH 3 flow and investigated by means of X-ray diffraction (XRD), transmission electronic microscopy (TEM), diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and photoluminescence (PL). With increasing NH 3 treatment temperature at T = 400 to 600 1C, the anatase crystallinity of the N-NTA(400-600) samples was gradually enhanced, while at 700 1C a new phase, TiN, appeared in the N-NTA(700) sample. XPS results show that the doped N atoms incorporated into anatase TiO 2 exist in the form of NO. A revised explanation for the triplet ESR signals obtained from the N-NTA(500-700) samples was put forward, i.e. the g = 2.004 main peak is contributed by single-electron-trapped oxygen vacancies (denoted as V o ), while two weak peaks (g = 2.023, 1.987) are contributed by chemisorbed NO in well-crystallized anatase TiO 2 .The visible light photoactivity is proportional to the height of the g = 2.004 main peak, which suggests that the photoactive centers are V o -NO-Ti. The adsorbed NO molecule can effectively suppress the photoluminescence of V o defects, which facilitates photogenerated charge transfer to the surface reactive centers to conduct redox reactions. The higher the V o -NO-Ti concentration, the better the visible light photoactivity. The highest photoactivity was obtained for the catalyst, NH 3 -treated at 600 1C. But the formation of TiN at T = 700 1C can readily destruct V o -NO-Ti photoactive centers, and thus readily decreases photoactivity efficiency.
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