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Morphology and photoluminescence study of titania nanoparticles.

Memesa M, Lenz S, Emmerling SG, Nett S, Perlich J, Müller-Buschbaum P, Gutmann JS - Colloid Polym Sci (2011)

Bottom Line: The sol-gel components-hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer-are varied to investigate their effect on the resulting titania morphology.The interplay among the sol-gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities.Smaller sized titania particles, (∼13-20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies.

View Article: PubMed Central - PubMed

ABSTRACT
Titania nanoparticles are prepared by sol-gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)-block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol-gel components-hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer-are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol-gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13-20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies.

No MeSH data available.


Related in: MedlinePlus

Double-logarithmic plots of the out-of-plane cuts of the 2D intensity as a function of the qy component of the scattering vector. For clarity, the curves are shifted along the intensity axis. The dashed line indicates the resolution limit of the μGISAXS experiment. Colored lines are the fits, from unified fit model, for determining the prominent in-plane length scales, corresponding to the scattering data in black below them. From bottom to top, the curves correspond to samples from 2% TTIP (cyan), 2% BCP (polymer, green), 1% HCl (purple), 2% HCl (blue), and 3%HCl (red) concentration compositions in each graph. Upper graph (a) is for as-prepared, middle (b) is for heated at 450 °C, bottom graph (c) is for heated at 1,000 °C samples
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Fig4: Double-logarithmic plots of the out-of-plane cuts of the 2D intensity as a function of the qy component of the scattering vector. For clarity, the curves are shifted along the intensity axis. The dashed line indicates the resolution limit of the μGISAXS experiment. Colored lines are the fits, from unified fit model, for determining the prominent in-plane length scales, corresponding to the scattering data in black below them. From bottom to top, the curves correspond to samples from 2% TTIP (cyan), 2% BCP (polymer, green), 1% HCl (purple), 2% HCl (blue), and 3%HCl (red) concentration compositions in each graph. Upper graph (a) is for as-prepared, middle (b) is for heated at 450 °C, bottom graph (c) is for heated at 1,000 °C samples

Mentions: The structural stability of the particles was investigated by increasing the heating temperature further to 1,000 °C. The particle diameters, averaged from the SEM images, are in the range of 14–40 nm for the 1% HCl sample (in Fig. 3a), 12–48 nm for 2% HCl sample (in Fig. 3b), 11–42 nm for 3% HCl sample (in Fig. 3c), 12–48 nm for 2% TTIP sample (in Fig. 3d), and 10–20 nm for 2% polymer (in Fig. 3e, scale bars correspond to 200 nm). These high magnification images give information on the smallest structures; however, the overall homogeneity of the film still remains unclear. For as-prepared films, microscopy did not provide much information since the softness of the polymer at room temperature and the low electron density difference between Ti and Si prevent high-resolution imaging. Moreover, microscopy techniques are restricted to an investigation in the micrometer square range and to the sample surface. For investigating the lateral structure of titania particles inside the films (thickness of 30 ± 10 nm) and the uniformity of the titania morphology in the nanocomposite film, we performed μGISAXS measurements at the beamline BW4 in HASYLAB at DESY, Hamburg [26, 30]. In general, μGISAXS scattering patterns yield structural information averaged over the illuminated sample spots. In our case, this sample spot was of a size of 56,992 μm2 (1,781 × 32 μm). This is a consequence of the enlarged footprint at the chosen incident angle of 0.74°. The out-of-plane cuts at an exit angle equal to the critical angle of titania, αc = 0.28°, were selected to obtain an averaged structure information about the percolating titania structures in a range from several nanometers up to ∼190 nm. For a closer data analysis, the out-of-plane cuts were fitted according to the unified fit model [31–33]. This model was successfully applied to various scattering experiments in transmission geometry for different applications [31, 32, 34–38]. We used the unified fit model to investigate the morphology of our titania structures in our previous investigations already [17, 39, 40]. This model describes the structure of the material in terms of structural levels, ranging from single particles to clusters. Each structural level contains a Guinier regime which describes the size and a power law regime giving the integral properties of the structure. The Porod regime provides information about the surface and mass fractality of the individual structure. Thus, it is possible to differentiate between smooth and jagged primary particle structures and between crystal-like and disordered secondary cluster structures. Figure 4 shows the out-of-plane cuts together with fits which are overlaid on experimental data for as-prepared, heated at 450 and 1,000 °C, samples.Fig. 3


Morphology and photoluminescence study of titania nanoparticles.

Memesa M, Lenz S, Emmerling SG, Nett S, Perlich J, Müller-Buschbaum P, Gutmann JS - Colloid Polym Sci (2011)

Double-logarithmic plots of the out-of-plane cuts of the 2D intensity as a function of the qy component of the scattering vector. For clarity, the curves are shifted along the intensity axis. The dashed line indicates the resolution limit of the μGISAXS experiment. Colored lines are the fits, from unified fit model, for determining the prominent in-plane length scales, corresponding to the scattering data in black below them. From bottom to top, the curves correspond to samples from 2% TTIP (cyan), 2% BCP (polymer, green), 1% HCl (purple), 2% HCl (blue), and 3%HCl (red) concentration compositions in each graph. Upper graph (a) is for as-prepared, middle (b) is for heated at 450 °C, bottom graph (c) is for heated at 1,000 °C samples
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3102206&req=5

Fig4: Double-logarithmic plots of the out-of-plane cuts of the 2D intensity as a function of the qy component of the scattering vector. For clarity, the curves are shifted along the intensity axis. The dashed line indicates the resolution limit of the μGISAXS experiment. Colored lines are the fits, from unified fit model, for determining the prominent in-plane length scales, corresponding to the scattering data in black below them. From bottom to top, the curves correspond to samples from 2% TTIP (cyan), 2% BCP (polymer, green), 1% HCl (purple), 2% HCl (blue), and 3%HCl (red) concentration compositions in each graph. Upper graph (a) is for as-prepared, middle (b) is for heated at 450 °C, bottom graph (c) is for heated at 1,000 °C samples
Mentions: The structural stability of the particles was investigated by increasing the heating temperature further to 1,000 °C. The particle diameters, averaged from the SEM images, are in the range of 14–40 nm for the 1% HCl sample (in Fig. 3a), 12–48 nm for 2% HCl sample (in Fig. 3b), 11–42 nm for 3% HCl sample (in Fig. 3c), 12–48 nm for 2% TTIP sample (in Fig. 3d), and 10–20 nm for 2% polymer (in Fig. 3e, scale bars correspond to 200 nm). These high magnification images give information on the smallest structures; however, the overall homogeneity of the film still remains unclear. For as-prepared films, microscopy did not provide much information since the softness of the polymer at room temperature and the low electron density difference between Ti and Si prevent high-resolution imaging. Moreover, microscopy techniques are restricted to an investigation in the micrometer square range and to the sample surface. For investigating the lateral structure of titania particles inside the films (thickness of 30 ± 10 nm) and the uniformity of the titania morphology in the nanocomposite film, we performed μGISAXS measurements at the beamline BW4 in HASYLAB at DESY, Hamburg [26, 30]. In general, μGISAXS scattering patterns yield structural information averaged over the illuminated sample spots. In our case, this sample spot was of a size of 56,992 μm2 (1,781 × 32 μm). This is a consequence of the enlarged footprint at the chosen incident angle of 0.74°. The out-of-plane cuts at an exit angle equal to the critical angle of titania, αc = 0.28°, were selected to obtain an averaged structure information about the percolating titania structures in a range from several nanometers up to ∼190 nm. For a closer data analysis, the out-of-plane cuts were fitted according to the unified fit model [31–33]. This model was successfully applied to various scattering experiments in transmission geometry for different applications [31, 32, 34–38]. We used the unified fit model to investigate the morphology of our titania structures in our previous investigations already [17, 39, 40]. This model describes the structure of the material in terms of structural levels, ranging from single particles to clusters. Each structural level contains a Guinier regime which describes the size and a power law regime giving the integral properties of the structure. The Porod regime provides information about the surface and mass fractality of the individual structure. Thus, it is possible to differentiate between smooth and jagged primary particle structures and between crystal-like and disordered secondary cluster structures. Figure 4 shows the out-of-plane cuts together with fits which are overlaid on experimental data for as-prepared, heated at 450 and 1,000 °C, samples.Fig. 3

Bottom Line: The sol-gel components-hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer-are varied to investigate their effect on the resulting titania morphology.The interplay among the sol-gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities.Smaller sized titania particles, (∼13-20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies.

View Article: PubMed Central - PubMed

ABSTRACT
Titania nanoparticles are prepared by sol-gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)-block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol-gel components-hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer-are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol-gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13-20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies.

No MeSH data available.


Related in: MedlinePlus