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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 electrolyte type (monovalent vs. divalent) on TiO2 (P25) dispersion properties at a the same solution ionic strength and b the same electrolyte molar concentration.
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Figure 2: The influence of electrolyte type (monovalent vs. divalent) on TiO2 (P25) dispersion properties at a the same solution ionic strength and b the same electrolyte molar concentration.

Mentions: If an electrolyte does not generate ions that can be specifically absorbed by titania nanoparticles, its influence on dispersion properties can be quantified through its contribution to solution ionic strength. TiO2 (P25) was dispersed in both monovalent NaCl and divalent MgCl2 solutions either at the same ionic strength (Figure 2a) or at the same electrolyte molar concentration (Figure 2b). The solution pH (~5.5) was lower than TiO2 (P25) IEP such that positive zeta potentials were observed in both cases. When the same IS was used, dispersions using NaCl and MgCl2 did not show any significant difference in zeta potential and hydrodynamic size. The trends of zeta potential and hydrodynamic size as a function of IS were the same as described earlier. When the same molar concentration was used, the solution IS using divalent MgCl2 was twice as high as the IS using monovalent NaCl. Consequently, titania dispersion using MgCl2 had lower zeta potential and higher hydrodynamic diameter compared to a dispersion using NaCl of the same molar concentration.


Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
The influence of electrolyte type (monovalent vs. divalent) on TiO2 (P25) dispersion properties at a the same solution ionic strength and b the same electrolyte molar concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: The influence of electrolyte type (monovalent vs. divalent) on TiO2 (P25) dispersion properties at a the same solution ionic strength and b the same electrolyte molar concentration.
Mentions: If an electrolyte does not generate ions that can be specifically absorbed by titania nanoparticles, its influence on dispersion properties can be quantified through its contribution to solution ionic strength. TiO2 (P25) was dispersed in both monovalent NaCl and divalent MgCl2 solutions either at the same ionic strength (Figure 2a) or at the same electrolyte molar concentration (Figure 2b). The solution pH (~5.5) was lower than TiO2 (P25) IEP such that positive zeta potentials were observed in both cases. When the same IS was used, dispersions using NaCl and MgCl2 did not show any significant difference in zeta potential and hydrodynamic size. The trends of zeta potential and hydrodynamic size as a function of IS were the same as described earlier. When the same molar concentration was used, the solution IS using divalent MgCl2 was twice as high as the IS using monovalent NaCl. Consequently, titania dispersion using MgCl2 had lower zeta potential and higher hydrodynamic diameter compared to a dispersion using NaCl of the same molar concentration.

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.