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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.

No MeSH data available.


The influence of nanoparticle surface area (mass concentration) on TiO2 (P25) dispersion characteristics: a pH; b zeta potential and hydrodynamic diameter. Solvent is DI water.
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Figure 3: The influence of nanoparticle surface area (mass concentration) on TiO2 (P25) dispersion characteristics: a pH; b zeta potential and hydrodynamic diameter. Solvent is DI water.

Mentions: Titania nanoparticle surface area in the dispersion affects both solution pH and dispersion properties. TiO2 (P25) nanoparticles with mass concentrations of 15, 25, 50, 150, and 500 μg/ml were dispersed in DI water. As the size of the particles in the sample is the same, the particle surface area is proportional to the particle mass concentration. As shown in Figure 3a, solution pH decreased as the particle surface area increased. When TiO2 nanoparticle is dispersed in water, its surface is covered by the hydroxyl group and extra hydrogen ions are produced (Eq. 1). Consequently, the solution pH decreases as more hydrogen ions are generated due to the increase in titania particle surface area. When particle mass concentration was increased from 15 to 500 μg/ml, the pH of the solution decreased from 5.7 to 5.1. Solution pH also became farther shifted from the TiO2 (P25) isoelectric point (6.2). Therefore, the dispersion zeta potential increased from 29 to 38 mV (Figure 3b). Though higher mass concentration often leads to larger hydrodynamic diameters, the average hydrodynamic diameter decreased from 756 to 412 nm, because the associated increase in the zeta potential (increase in repulsive force) prevented agglomeration. If the particle concentration is increased further, an increase in the average hydrodynamic diameter is expected, since the frequency of particle collision is a strong function of particle number concentration [54,55].


Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
The influence of nanoparticle surface area (mass concentration) on TiO2 (P25) dispersion characteristics: a pH; b zeta potential and hydrodynamic diameter. Solvent is DI water.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: The influence of nanoparticle surface area (mass concentration) on TiO2 (P25) dispersion characteristics: a pH; b zeta potential and hydrodynamic diameter. Solvent is DI water.
Mentions: Titania nanoparticle surface area in the dispersion affects both solution pH and dispersion properties. TiO2 (P25) nanoparticles with mass concentrations of 15, 25, 50, 150, and 500 μg/ml were dispersed in DI water. As the size of the particles in the sample is the same, the particle surface area is proportional to the particle mass concentration. As shown in Figure 3a, solution pH decreased as the particle surface area increased. When TiO2 nanoparticle is dispersed in water, its surface is covered by the hydroxyl group and extra hydrogen ions are produced (Eq. 1). Consequently, the solution pH decreases as more hydrogen ions are generated due to the increase in titania particle surface area. When particle mass concentration was increased from 15 to 500 μg/ml, the pH of the solution decreased from 5.7 to 5.1. Solution pH also became farther shifted from the TiO2 (P25) isoelectric point (6.2). Therefore, the dispersion zeta potential increased from 29 to 38 mV (Figure 3b). Though higher mass concentration often leads to larger hydrodynamic diameters, the average hydrodynamic diameter decreased from 756 to 412 nm, because the associated increase in the zeta potential (increase in repulsive force) prevented agglomeration. If the particle concentration is increased further, an increase in the average hydrodynamic diameter is expected, since the frequency of particle collision is a strong function of particle number concentration [54,55].

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.