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 TiO2 crystal phase on dispersion zeta potential. Solution IS is 0.001 M.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: The influence of TiO2 crystal phase on dispersion zeta potential. Solution IS is 0.001 M.

Mentions: The influence of titania crystal phase on dispersion isoelectric points was also examined using laboratory synthesized samples. Three 38-nm TiO2 samples with different anatase percentages (100, 49, and 36%; remainder being rutile) and one 102-nm rutile (100%) TiO2 sample were tested using solutions with IS of 0.001 M. For the three same sized TiO2 with different crystal structures, their dispersion isoelectric points (~4.8) were similar to each other (Figure 7). The IEP of 102-nm rutile TiO2 was lower than pH 3 such that the crossing point was not measured when pH range of 3–11 was used. The observation that the IEP of TiO2 at the same size is rather insensitive to the crystal structure is consistent with reports in the previous literature [49]. There are two possible factors accounting for the low IEP of the 102-nm rutile TiO2 sample. If the observed size-dependent IEP trend for anatase TiO2 is also valid for rutile TiO2, one would expect than 102-nm rutile has a lower IEP than that of 38-nm rutile. In addition, Figure 5 shows that 104-nm anatase TiO2 has an IEP of 3.8, while IEP of rutile with similar size (102 nm) is lower than pH 3. This might be related to the synthesis methods used—anatase TiO2 was directly synthesized using a flame aerosol reactor, while rutile TiO2 was prepared by annealing flame-synthesized 53-nm anatase TiO2 at 850°C using a furnace. Other studies [41,45] also found that metal oxides synthesized using different methods may have different isoelectric points.


Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
The influence of TiO2 crystal phase on dispersion zeta potential. Solution IS is 0.001 M.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: The influence of TiO2 crystal phase on dispersion zeta potential. Solution IS is 0.001 M.
Mentions: The influence of titania crystal phase on dispersion isoelectric points was also examined using laboratory synthesized samples. Three 38-nm TiO2 samples with different anatase percentages (100, 49, and 36%; remainder being rutile) and one 102-nm rutile (100%) TiO2 sample were tested using solutions with IS of 0.001 M. For the three same sized TiO2 with different crystal structures, their dispersion isoelectric points (~4.8) were similar to each other (Figure 7). The IEP of 102-nm rutile TiO2 was lower than pH 3 such that the crossing point was not measured when pH range of 3–11 was used. The observation that the IEP of TiO2 at the same size is rather insensitive to the crystal structure is consistent with reports in the previous literature [49]. There are two possible factors accounting for the low IEP of the 102-nm rutile TiO2 sample. If the observed size-dependent IEP trend for anatase TiO2 is also valid for rutile TiO2, one would expect than 102-nm rutile has a lower IEP than that of 38-nm rutile. In addition, Figure 5 shows that 104-nm anatase TiO2 has an IEP of 3.8, while IEP of rutile with similar size (102 nm) is lower than pH 3. This might be related to the synthesis methods used—anatase TiO2 was directly synthesized using a flame aerosol reactor, while rutile TiO2 was prepared by annealing flame-synthesized 53-nm anatase TiO2 at 850°C using a furnace. Other studies [41,45] also found that metal oxides synthesized using different methods may have different isoelectric points.

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.