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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.

No MeSH data available.


Related in: MedlinePlus

Dopant concentration, representative TEM micrographs and corresponding size distribution of the particles. (a) XRD spectra at different methane flow rates (A anatase, R rutile) and particle size distributions at (b) 0.8 lpm, (c) 1.2 lpm methane flow rates for 3-wt.% Cu-TiO2 nanoparticles (test 2).
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Figure 7: Dopant concentration, representative TEM micrographs and corresponding size distribution of the particles. (a) XRD spectra at different methane flow rates (A anatase, R rutile) and particle size distributions at (b) 0.8 lpm, (c) 1.2 lpm methane flow rates for 3-wt.% Cu-TiO2 nanoparticles (test 2).

Mentions: The functionality of the nanomaterials depends on their properties such as particle size, crystal phase, morphology, and agglomeration [38,40]. A recent study by Braydich-Stolle et al. [42] showed that cytotoxicity in the cells is both size and crystal structure dependent. They demonstrated that mechanism of cell death varied with different crystal structure; the anatase phase of TiO2 being more toxic than the rutile phase. To understand the role of crystal phase of the doped nanomaterials on its functionality, it is important to independently control the crystal phase without varying the other material properties such as size. Previous studies have demonstrated that crystal phase of the TiO2 nanoparticle can be controlled by varying the temperature in the flame (changing the methane flow rates) and quenching rate downstream of the flame [25,26]. A similar methodology was adopted to control the crystal phase of the Cu-doped TiO2 materials. The dopant concentration was kept constant at 3 wt.% and methane flow was varied from 0.8 to 1.8 lpm (test 2, Figure 7a). The anatase phase varied from 39% to 95%, when the methane flow was increased from 0.8 to 1.2 lpm, whereas the primary particle sizes for all the cases were similar. The representative TEM micrographs and corresponding size distribution of the particles synthesized at 0.8 and 1.8 lpm are shown in Figure 7b, c. The geometric mean size of 31.5 and 32.3 nm were nearly the same for the two flow rate conditions. The size remained similar due to the balance between temperature profile and residence time in the flame at different methane flow rates. For a fixed flame operating parameters, increasing the methane flow rate increases the flame temperature but at the same time reduces the residence time in the flame. For lower methane flow rate the temperature decreases and residence time increases. Thus the crystal phase of the Cu-doped TiO2 nanoparticles was independently varied while keeping the primary particle size the same. These well-controlled Cu-doped TiO2 samples will be of significant importance in biological studies to elucidate the role of crystal phases without interferences from the other particle properties such as size.


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

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

Dopant concentration, representative TEM micrographs and corresponding size distribution of the particles. (a) XRD spectra at different methane flow rates (A anatase, R rutile) and particle size distributions at (b) 0.8 lpm, (c) 1.2 lpm methane flow rates for 3-wt.% Cu-TiO2 nanoparticles (test 2).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Dopant concentration, representative TEM micrographs and corresponding size distribution of the particles. (a) XRD spectra at different methane flow rates (A anatase, R rutile) and particle size distributions at (b) 0.8 lpm, (c) 1.2 lpm methane flow rates for 3-wt.% Cu-TiO2 nanoparticles (test 2).
Mentions: The functionality of the nanomaterials depends on their properties such as particle size, crystal phase, morphology, and agglomeration [38,40]. A recent study by Braydich-Stolle et al. [42] showed that cytotoxicity in the cells is both size and crystal structure dependent. They demonstrated that mechanism of cell death varied with different crystal structure; the anatase phase of TiO2 being more toxic than the rutile phase. To understand the role of crystal phase of the doped nanomaterials on its functionality, it is important to independently control the crystal phase without varying the other material properties such as size. Previous studies have demonstrated that crystal phase of the TiO2 nanoparticle can be controlled by varying the temperature in the flame (changing the methane flow rates) and quenching rate downstream of the flame [25,26]. A similar methodology was adopted to control the crystal phase of the Cu-doped TiO2 materials. The dopant concentration was kept constant at 3 wt.% and methane flow was varied from 0.8 to 1.8 lpm (test 2, Figure 7a). The anatase phase varied from 39% to 95%, when the methane flow was increased from 0.8 to 1.2 lpm, whereas the primary particle sizes for all the cases were similar. The representative TEM micrographs and corresponding size distribution of the particles synthesized at 0.8 and 1.8 lpm are shown in Figure 7b, c. The geometric mean size of 31.5 and 32.3 nm were nearly the same for the two flow rate conditions. The size remained similar due to the balance between temperature profile and residence time in the flame at different methane flow rates. For a fixed flame operating parameters, increasing the methane flow rate increases the flame temperature but at the same time reduces the residence time in the flame. For lower methane flow rate the temperature decreases and residence time increases. Thus the crystal phase of the Cu-doped TiO2 nanoparticles was independently varied while keeping the primary particle size the same. These well-controlled Cu-doped TiO2 samples will be of significant importance in biological studies to elucidate the role of crystal phases without interferences from the other particle properties such as size.

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