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

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.


The influence of solution ionic strength (IS) and pH on TiO2 (P25) dispersion properties: a zeta potential; b hydrodynamic diameter.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211333&req=5

Figure 1: The influence of solution ionic strength (IS) and pH on TiO2 (P25) dispersion properties: a zeta potential; b hydrodynamic diameter.

Mentions: The effect of solution pH and ionic strength (IS) on the zeta potential and hydrodynamic size is shown in Figure 1. The IEP for TiO2 (P25) is approximately 6.2, which is consistent with those reported in other studies [15,48,49]. Since NaCl is an inert electrolyte for TiO2 dispersion (no specific adsorption of Na+ or Cl- by the titania nanoparticle), the IEP remains the same at different ionic strengths obtained by varying the NaCl concentration [41,50]. When pH is different from pHIEP, an increase in IS reduces the dispersion zeta potential by compressing the electrical double layer. This is consistent with previous tests [15,51,52] and predictions of classical colloidal theory [53]. Solution pH affects the dispersion hydrodynamic diameter by changing the particle surface charge. Near IEP, significant agglomeration takes place; large flocs were observed, as the particle surface charge is close to zero and attractive van der Waals forces are dominant. When the pH is significantly different from IEP for titania, the absolute value of zeta potential becomes higher and the hydrodynamic size becomes smaller. Solution IS changes the dispersion hydrodynamic diameter by changing both zeta potential and electrical double layer thickness. Higher solution IS leads to a smaller electrical double layer thickness, weaker electrostatic repulsive force, and subsequently larger hydrodynamic size. The smallest hydrodynamic size observed was ~200 nm, when the solution IS was 0.001 M and pH was lower than 4.0 or higher than 8.2.


Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
The influence of solution ionic strength (IS) and pH on TiO2 (P25) dispersion properties: a zeta potential; b hydrodynamic diameter.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: The influence of solution ionic strength (IS) and pH on TiO2 (P25) dispersion properties: a zeta potential; b hydrodynamic diameter.
Mentions: The effect of solution pH and ionic strength (IS) on the zeta potential and hydrodynamic size is shown in Figure 1. The IEP for TiO2 (P25) is approximately 6.2, which is consistent with those reported in other studies [15,48,49]. Since NaCl is an inert electrolyte for TiO2 dispersion (no specific adsorption of Na+ or Cl- by the titania nanoparticle), the IEP remains the same at different ionic strengths obtained by varying the NaCl concentration [41,50]. When pH is different from pHIEP, an increase in IS reduces the dispersion zeta potential by compressing the electrical double layer. This is consistent with previous tests [15,51,52] and predictions of classical colloidal theory [53]. Solution pH affects the dispersion hydrodynamic diameter by changing the particle surface charge. Near IEP, significant agglomeration takes place; large flocs were observed, as the particle surface charge is close to zero and attractive van der Waals forces are dominant. When the pH is significantly different from IEP for titania, the absolute value of zeta potential becomes higher and the hydrodynamic size becomes smaller. Solution IS changes the dispersion hydrodynamic diameter by changing both zeta potential and electrical double layer thickness. Higher solution IS leads to a smaller electrical double layer thickness, weaker electrostatic repulsive force, and subsequently larger hydrodynamic size. The smallest hydrodynamic size observed was ~200 nm, when the solution IS was 0.001 M and pH was lower than 4.0 or higher than 8.2.

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.