Citric Acid Adsorption on TiO2 Nanoparticles in Aqueous Suspensions at Acidic and Circumneutral pH: Surface Coverage, Surface Speciation, and Its Impact on Nanoparticle−Nanoparticle Interactions
- 4 October 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 132 (42), 14986-14994
- https://doi.org/10.1021/ja106091q
Abstract
Citric acid plays an important role as a stabilizer in several nanomaterial syntheses and is a common organic acid found in nature. Here, the adsorption of citric acid onto TiO(2) anatase nanoparticles with a particle diameter of ca. 4 nm is investigated at circumneutral and acidic pHs. This study focuses on both the details of the surface chemistry of citric acid on TiO(2), including measurements of surface coverage and speciation, and its impact on nanoparticle behavior. Using macroscopic and molecular-based probes, citric acid adsorption and nanoparticle interactions are measured with quantitative solution phase adsorption measurements, attenuated total reflection-FTIR spectroscopy, dynamic light scattering techniques, and zeta-potential measurements as a function of solution pH. The results show that surface coverage is a function of pH and decreases with increasing pH. Surface speciation differs from the bulk solution and is time dependent. After equilibration, the fully deprotonated citrate ion is present on the surface regardless of the highly acidic solution pH indicating pK(a) values of surface adsorbed species are lower than those in solution. Nanoparticle interactions are also probed through measurements of aggregation and the data show that these interactions are complex and depend on the detailed interplay between bulk solution pH and surface chemistry.Keywords
This publication has 34 references indexed in Scilit:
- Instability of Cationic Gold Nanoparticle Bioconjugates: The Role of Citrate IonsJournal of the American Chemical Society, 2010
- Nanorod Dissolution Quenched in the Aggregated StateLangmuir, 2009
- Molecular Structures of Citrate and Tricarballylate Adsorbed on α-FeOOH Particles in Aqueous SuspensionsLangmuir, 2009
- Adsorption of Organic Acids on TiO2 Nanoparticles: Effects of pH, Nanoparticle Size, and Nanoparticle AggregationLangmuir, 2008
- Mechanistic Study of Photomediated Triangular Silver Nanoprism GrowthJournal of the American Chemical Society, 2008
- Inhalation Exposure Study of Titanium Dioxide Nanoparticles with a Primary Particle Size of 2 to 5 nmEnvironmental Health Perspectives, 2007
- Characterization and Surface-Reactivity of Nanocrystalline Anatase in Aqueous SolutionsLangmuir, 2006
- Infrared spectra of oxalate, malonate and succinate adsorbed on the aqueous surface of rutile, anatase and lepidocrocite measured with in situ ATR-FTIRJournal of Electron Spectroscopy and Related Phenomena, 2006
- Dissolution Kinetics of Titanium Dioxide Nanoparticles: The Observation of an Unusual Kinetic Size EffectThe Journal of Physical Chemistry B, 2006
- Adsorption of Organic Matter at Mineral/Water Interfaces. 6. Effect of Inner-Sphere versus Outer-Sphere Adsorption on Colloidal StabilityLangmuir, 2005