Role of Synthesis Method and Particle Size of Nanostructured TiO2 on Its Photoactivity

Almquist, Catherine B.; Biswas, Pratim

doi:10.1006/jcat.2002.3783

Cited by 444 publications

(271 citation statements)

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“…Another very important factor is the crystallite size. In this study the best photocatalytic activity was found for a sample with 25 nm of anatase crystallite and this is consistent with the results of Almquist et al (44). They showed that photoactivity increase with particle size and the optimal effective particle size is in the range from 25 to 40 nm.…”

Section: Resultssupporting

confidence: 92%

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Kusiak-Nejman

Wanag

Kowalczyk

et al. 2016

Journal of Advanced Oxidation Technologies

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Abstract:This work investigated the photocatalytic performance of TiO 2 photocatalysts modified with graphitic carbon under visible light with a very small component of UV. The graphitic carbon modification was conducted at 200-500 °C using thermal anthracene decomposition. The increase of calcination temperature leads to typical increase of crystallites size, decrease of the specific surface area and carbon content in modified samples. The characteristic peak for a skeletal in-plane vibrations of the anthracene ring located at 1522 cm -1 as well as the band at 1410 cm -1 assigned to C=C aromatic stretching vibrations mode were possible to observe. The analysis of the morphology using SEM confirmed the presence on new multi-layer carbonaceous flakes decorated with TiO 2 nanoparticles. TEM analysis and Raman studies proved the presence of graphitic structures covering the surface of the prepared TiO 2 /C photocatalysts. The highest photocatalytic activity, calculated on the basis of phenol photodegradation under visible light, was found for the photocatalyst modified with graphitic carbon at 400 °C (TiO 2 /C-400).

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Section: Resultssupporting

confidence: 92%

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Kusiak-Nejman

Wanag

Kowalczyk

et al. 2016

Journal of Advanced Oxidation Technologies

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“…30 nm particles showed the highest activity in terms of ROS species generation at both mass concentrations. This seems to be consistent with the photoactivity results of TiO 2 nanoparticles, where the optimum effective size for TiO 2 photoactivity has been reported to be in the range of 25 -40 nm (Almquist and Biswas 2002). However, no size effect is discernable, as the total surface area is not held constant for all the samples (higher for the smaller sized particles at the same mass concentration).…”

Section: Size Effectsupporting

confidence: 90%

“…Below 10 nm, the ROS generation per unit surface area is also approximately the same (Figure 4c) due to the number of reactive sites being constant per unit surface area. One reason for this could be that particles below 10 nm are synthesized by quenching the particle growth by very rapid dilution (Almquist and Biswas 2002;Jiang et al 2007). Due to this, the number of reactive sites per unit area may not decrease further with decrease in size but remain approximately constant.…”

Section: Discussionmentioning

confidence: 99%

Does nanoparticle activity depend upon size and crystal phase?

et al. 2008

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A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO 2 nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO 2 nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO 2 nanoparticles of 9 different sizes (4 -195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO 2 nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO 2 nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.

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“…3 Photocatalysis studies have spanned well-characterized, single-crystal (usually rutile) surfaces under ultrahigh vacuum (UHV) conditions [4][5][6] to polycrystalline powders under catalysis operational conditions. [7][8][9] The latter have generally involved the catalyst in contact with an aqueous solution or water vapor. It is acknowledged that the presence of water is important for photocatalysis, [10][11] but its exact role in the process is poorly understood.…”

mentioning

confidence: 99%

Apparent Semiconductor Type Reversal in Anatase TiO₂ Nanocrystalline Films

et al. 2007

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The electronic properties of anatase and rutile TiO 2 polycrystalline particle films have been studied using surface photovoltage (SPV) and infrared (IR) spectroscopies. The films were prepared from aqueous suspensions using a range of particle sizes (8-400 nm) and were examined under different ambient conditions. The results show that all of the examined films exhibited the expected n-type semiconductor characteristics in dry nitrogen ambient. Films created from the 30 and 400 nm anatase particles exhibited the largest surface photovoltage and also a broad mid-IR absorption attributed to shallowly trapped electrons. The latter was absent from films made from rutile particles. When examined under as-prepared "wet" conditions, the SPV was reduced in magnitude and the IR signal was absent. Further, the films formed from 8 and 30 nm particles exhibited an apparent p-type behavior in their SPV spectra. Interestingly, small anatase particles are known to exhibit enhanced photocatalytic activity when compared to larger anatase particles. These correlations indicate that water, adsorbed on TiO 2 particles of nanodimensions, induce surface states and enable redistribution of photogenerated charge carriers, which is conducive to photocatalysis.Photocatalysis at semiconductor surfaces has been extensively investigated over recent decades. 1-3 Titanium dioxide has usually been the photocatalyst of choice and Degussa P25, which contains about 80% anatase and 20% rutile, has emerged as the benchmark material. 3 Photocatalysis studies have spanned well-characterized, single-crystal (usually rutile) surfaces under ultrahigh vacuum (UHV) conditions 4-6 to polycrystalline powders under catalysis operational conditions. 7-9 The latter have generally involved the catalyst in contact with an aqueous solution or water vapor. It is acknowledged that the presence of water is important for photocatalysis, 10-11 but its exact role in the process is poorly understood. 12-15 Numerous models 13,[16][17][18][19] have been proposed for the influence of adsorbed water on charge carrier trapping but consensus has still to be reached.Surface photovoltage (SPV) spectroscopy has been used to study both polycrystalline and single crystal (110) rutile TiO 2 . [20][21][22] For both types of material, it was reported that water modified the surface work function of rutile TiO 2 surfaces. There appear to have been no corresponding studies of anatase TiO 2 surfaces. It has been observed that adsorbed water influences a broad mid-infrared spectral absorption between 4000 and 700 cm -1 , which arises when TiO 2 polycrystalline films are irradiated with UV light 13,17,23,24 and that has been assigned to excitation of shallowly trapped electrons. 24 Panyatov and Yates 17 observed that this signal decreases when water is chemisorbed to the surface of a thermally reduced P25 TiO 2 film. They propose that the water depletes conduction band electrons during the formation of Ti-OH groups in the early stages of chemisorption. In this paper, we report the results...

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Role of Synthesis Method and Particle Size of Nanostructured TiO2 on Its Photoactivity

Cited by 444 publications

References 16 publications

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Does nanoparticle activity depend upon size and crystal phase?

Apparent Semiconductor Type Reversal in Anatase TiO₂ Nanocrystalline Films

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Role of Synthesis Method and Particle Size of Nanostructured TiO2 on Its Photoactivity

Cited by 444 publications

References 16 publications

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Does nanoparticle activity depend upon size and crystal phase?

Apparent Semiconductor Type Reversal in Anatase TiO2 Nanocrystalline Films

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Apparent Semiconductor Type Reversal in Anatase TiO₂ Nanocrystalline Films