Eunhyea Chung

Publications (2)9.6 Total impact

• Article: Interaction of silica nanoparticles with a flat silica surface through neutron reflectometry.

  Eunhyea Chung, Sotira Yiacoumi, Candice Halbert, John Ankner, Wei Wang, Changwoo Kim, Costas Tsouris
  [show abstract] [hide abstract]
  ABSTRACT: Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.
  Environmental Science & Technology 03/2012; 46(8):4532-8. · 4.80 Impact Factor
• Article: Photosensitized oxidation of emerging organic pollutants by tetrakis C₆₀ aminofullerene-derivatized silica under visible light irradiation.

  Jaesang Lee, Seokwon Hong, Yuri Mackeyev, Changha Lee, Eunhyea Chung, Lon J Wilson, Jae-Hong Kim, Pedro J J Alvarez
  [show abstract] [hide abstract]
  ABSTRACT: We recently reported that C(60) aminofullerenes immobilized on silica support (aminoC(60)/silica) efficiently produce singlet oxygen ((1)O(2)) and inactivate virus and bacteria under visible light irradiation. (1) We herein evaluate this new photocatalyst for oxidative degradation of 11 emerging organic contaminants, including pharmaceuticals such as acetaminophen, carbamazepine, cimetidine, propranolol, ranitidine, sulfisoxazole, and trimethoprim, and endocrine disruptors such as bisphenol A and pentachlorophenol. Tetrakis aminoC(60)/silica degraded pharmaceuticals under visible light irradiation faster than common semiconductor photocatalysts such as platinized WO(3) and carbon-doped TiO(2). Furthermore, aminoC(60)/silica exhibited high target-specificity without significant interference by natural organic matter. AminoC(60)/silica was more efficient than unsupported (water-suspended) C(60) aminofullerene. This was attributed to kinetically enhanced (1)O(2) production after immobilization, which reduces agglomeration of the photocatalyst, and to adsorption of pharmaceuticals onto the silica support, which increases exposure to (1)O(2) near photocatalytic sites. Removal efficiency increased with pH for contaminants with a phenolic moiety, such as bisphenol A and acetaminophen, because the electron-rich phenolates that form at alkaline pH are more vulnerable to singlet oxygenation.
  Environmental Science & Technology 11/2011; 45(24):10598-604. · 4.80 Impact Factor