title: Silicon impurity release and surface transformation of TiO2 anatase and rutile nanoparticles in water environments.
abstract: Surface transformation can affect the stability, reactivity, and toxicity of titanium dioxide (TiO2) nanoparticles (NPs) in water environments. Herein, we investigated the release kinetics of Si impurity frequently introduced during NP synthesis and the resulting effect on TiO2 NP transformation in aqueous solutions. The release of Si increased from 2 h to 19 d at three pHs with the order: pH 11.2 ≥ pH 2.4 > pH 8.2. The Si release process followed parabolic kinetics which is similar to diffusion controlled dissolution of minerals, and the release magnitude followed the order: 10 × 40 nm rutile > 50 nm anatase > 30 × 40 nm rutile. FTIR data indicated preferential dissolving of less polymerized Si species on NP surface. Surface potential and particle size of TiO2 NPs remained almost constant during the 42-day monitoring, implying the unaffected stability and transport of these NPs by the incongruent dissolution of impurities.
authors.affiliation: National Research Council, 919 Kerr Research Drive, Ada, OK 74820, United States. Electronic address: liux@seas.wustl.edu.
authors.forename: Xuyang
authors.initials: X
authors.lastname: Liu
authors.forename: Gexin
authors.initials: G
authors.lastname: Chen
authors.forename: Justin G
authors.initials: JG
authors.lastname: Erwin
authors.forename: Chunming
authors.initials: C
authors.lastname: Su
mesh_terms: D004784:Environmental Monitoring; D007700:Kinetics; D008956:Models, Chemical; D053758:Nanoparticles / Q000032:analysis* / Q000737:chemistry; D010316:Particle Size; D012825:Silicon / Q000032:analysis / Q000737:chemistry*; D014025:Titanium / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D012825:Silicon
keywords: Impurity release; Incongruent dissolution; Silicon; TiO(2) nanoparticles; Transformation