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Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor.

Sahu M, Biswas P - Nanoscale Res Lett (2011)

Bottom Line: This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region.Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure.Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV) synthesized under the same flame conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St, Louis, St, Louis, MO 63130, USA. pbiswas@wustl.edu.

ABSTRACT
Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV) synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO2 crystal.

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XRD pattern of the annealed Cu-TiO2 nanoparticles. (a) 1-wt.% Cu-TiO2 (b) 15-wt.% Cu-TiO2. A anatase, R rutile. Samples were annealed for 4 h in a furnace at constant temperature (test 3).
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Figure 8: XRD pattern of the annealed Cu-TiO2 nanoparticles. (a) 1-wt.% Cu-TiO2 (b) 15-wt.% Cu-TiO2. A anatase, R rutile. Samples were annealed for 4 h in a furnace at constant temperature (test 3).

Mentions: The morphological and structural transformation of the doped nanoparticles plays important role in photocatalytic activity by modifying the surface chemistry, crystal and electronic structure [43]. Since both amorphous and crystalline phases were observed in HR-TEM images at higher dopant concentration, the as-prepared Cu-doped TiO2 samples were annealed at different temperatures to investigate the effect on crystal structure and morphology. The 1 and 15-wt.% Cu-doped TiO2 samples were annealed at temperatures of 400°C and 600°C for 6 h. No phase transformation was observed at 400°C. At 600°C, the transformation from anatase to rutile phase was observed as shown in Figure 8, which is consistent with other studies [18,44]. The anatase weight fraction decreased from 75% to 21% for the 15-wt.% Cu-doped TiO2 sample. However, the morphology of the particles changed from spherical to hexagonal structure for nanoparticles prepared at both the dopant concentrations. The crystallite size increased with annealing. For 15-wt.% Cu-doped TiO2 sample, the phase related to CuO was observed based on the peaks recorded at Bragg angle of 35.5 and 39 from the XRD pattern (Figure 8). The amorphous CuO present in the outer layers were annealed to form the crystalline phase in the presence of air.


Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor.

Sahu M, Biswas P - Nanoscale Res Lett (2011)

XRD pattern of the annealed Cu-TiO2 nanoparticles. (a) 1-wt.% Cu-TiO2 (b) 15-wt.% Cu-TiO2. A anatase, R rutile. Samples were annealed for 4 h in a furnace at constant temperature (test 3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211860&req=5

Figure 8: XRD pattern of the annealed Cu-TiO2 nanoparticles. (a) 1-wt.% Cu-TiO2 (b) 15-wt.% Cu-TiO2. A anatase, R rutile. Samples were annealed for 4 h in a furnace at constant temperature (test 3).
Mentions: The morphological and structural transformation of the doped nanoparticles plays important role in photocatalytic activity by modifying the surface chemistry, crystal and electronic structure [43]. Since both amorphous and crystalline phases were observed in HR-TEM images at higher dopant concentration, the as-prepared Cu-doped TiO2 samples were annealed at different temperatures to investigate the effect on crystal structure and morphology. The 1 and 15-wt.% Cu-doped TiO2 samples were annealed at temperatures of 400°C and 600°C for 6 h. No phase transformation was observed at 400°C. At 600°C, the transformation from anatase to rutile phase was observed as shown in Figure 8, which is consistent with other studies [18,44]. The anatase weight fraction decreased from 75% to 21% for the 15-wt.% Cu-doped TiO2 sample. However, the morphology of the particles changed from spherical to hexagonal structure for nanoparticles prepared at both the dopant concentrations. The crystallite size increased with annealing. For 15-wt.% Cu-doped TiO2 sample, the phase related to CuO was observed based on the peaks recorded at Bragg angle of 35.5 and 39 from the XRD pattern (Figure 8). The amorphous CuO present in the outer layers were annealed to form the crystalline phase in the presence of air.

Bottom Line: This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region.Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure.Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV) synthesized under the same flame conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St, Louis, St, Louis, MO 63130, USA. pbiswas@wustl.edu.

ABSTRACT
Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV) synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO2 crystal.

No MeSH data available.


Related in: MedlinePlus