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Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

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ABSTRACT

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure.

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The influence of anatase TiO2 primary particle size on dispersion zeta potential. Solution IS is 0.001 M. Inset shows the titania nanoparticle dispersion isoelectric point (IEP) as a function of primary particle size.
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Figure 5: The influence of anatase TiO2 primary particle size on dispersion zeta potential. Solution IS is 0.001 M. Inset shows the titania nanoparticle dispersion isoelectric point (IEP) as a function of primary particle size.

Mentions: The influence of primary particle size on the titania dispersion isoelectric point was tested using laboratory synthesized TiO2 nanoparticles. Anatase TiO2 samples of different sizes (6, 16, 26, 38, 53, and 104 nm) were tested using solutions with an IS of 0.001 M. As shown in Figure 5, the IEP of anatase TiO2 was found to be a function of primary particle size. When primary particle size increased from 6 to 104 nm, the IEP decreased from 6.0 to 3.8. It has been reported that different isoelectric points can be obtained for the same material depending on the synthesis method and experimental procedure [45,48,49]. This might explain why 27-nm TiO2 (P25) has an IEP of 6.2 while laboratory synthesized 26-nm TiO2 has an IEP of 5.2 (their crystal phases are also different, which will be addressed later). However, these six samples were prepared using the same synthesis technique, and the experimental procedures were the same. In addition, there was evidence suggesting that hematite nanoparticle IEP might vary with particle size [33], though only three sizes were examined in that study.


Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
The influence of anatase TiO2 primary particle size on dispersion zeta potential. Solution IS is 0.001 M. Inset shows the titania nanoparticle dispersion isoelectric point (IEP) as a function of primary particle size.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211333&req=5

Figure 5: The influence of anatase TiO2 primary particle size on dispersion zeta potential. Solution IS is 0.001 M. Inset shows the titania nanoparticle dispersion isoelectric point (IEP) as a function of primary particle size.
Mentions: The influence of primary particle size on the titania dispersion isoelectric point was tested using laboratory synthesized TiO2 nanoparticles. Anatase TiO2 samples of different sizes (6, 16, 26, 38, 53, and 104 nm) were tested using solutions with an IS of 0.001 M. As shown in Figure 5, the IEP of anatase TiO2 was found to be a function of primary particle size. When primary particle size increased from 6 to 104 nm, the IEP decreased from 6.0 to 3.8. It has been reported that different isoelectric points can be obtained for the same material depending on the synthesis method and experimental procedure [45,48,49]. This might explain why 27-nm TiO2 (P25) has an IEP of 6.2 while laboratory synthesized 26-nm TiO2 has an IEP of 5.2 (their crystal phases are also different, which will be addressed later). However, these six samples were prepared using the same synthesis technique, and the experimental procedures were the same. In addition, there was evidence suggesting that hematite nanoparticle IEP might vary with particle size [33], though only three sizes were examined in that study.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure.

No MeSH data available.