Browsing by Author "Schiller, TL"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Organization of mixed dimethyldioctadecylammonium and choline modifiers on the surface of synthetic hectorite
    (Academic Press Inc Elsevier Science, 2013-11-01) Andriani, Y; Jack, KS; Gilbert, EP; Edwards, GA; Schiller, TL; Strounina, E; Osman, AF; Martin, DJ
    Understanding the nature of mixed surfactant self-assembly on the surface of organoclays is an important step toward optimizing their performance in polymer nanocomposites and for other potential applications, where selective surface interactions are crucial. In segmented thermoplastic polyurethane nanocomposite systems, dual-modified organoclays have shown significantly better performance compared to their single-modified counterparts. Until now, we had not fully characterized the physical chemistry of these dual-modified layered silicates, but had hypothesized that the enhanced composite performance arises due to some degree of nanoscale phase separation on the nanofiller surface, which enables enhanced compatibilization and more specific and inclusive interactions with the nanoscale hard and soft domains in these thermoplastic elastomers. This work examines the organization of quaternary alkyl ammonium compounds on the surface of Lucentite SWN using X-ray diffraction (XRD), thermogravimetric analysis (TGA), attenuated total reflectance Fourier-transfer infrared (ATR FT-IR), C-13 cross-polarization (CP)/magic angle spinning (MAS) nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS). When used in combination with choline, dimethyldioctadecylammonium (DMDO) was observed to self-assemble into discontinuous hydrophobic domains. The inner part of these hydrophobic domains was essentially unaffected by the choline (CC); however, surfactant intermixing was observed either at the periphery or throughout the choline-rich phase surrounding those domains. © 2013, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Synthesis and characterization of dual radiolabeled layered double hydroxide nanoparticles for use in in vitro and in vivo nanotoxicology studies
    (American Chemical Society, 2010-01-21) Musumeci, AW; Schiller, TL; Xu, ZP; Minchin, RF; Martin, DJ; Smith, SV
    Layered double hydroxide (LDH) nanomaterials are currently the focus of intense scientific interest due to their potential application in drug and gene delivery research. However, the emerging field of nanotoxicology requires the development of new and more sensitive methodologies to follow the in vivo delivery kinetics as well as the persistence and bioaccumulation of the LDH carriers subsequent to delivery of the payload to the target area. Radioisotopic labeling offers very high detection sensitivity (<10−14 moles) and straightforward quantitation with respect to other labeling techniques. We have shown that incorporation of naturally occurring Co2+ and Ga3+ cations into the LDH structure has a negligible effect on the physiochemical properties of the pristine nanoparticles. Radiolabeling through dual isomorphous substitution of 57Co2+ and 67Ga3+ into the LDH structure offers the utility to accurately track and also follow the structural dissolution of these nanomaterials over a range of biologically relevant pHs. Radiolabeled-LDH kinetic release profiles in conjunction with transmission electron microscopy and X-ray diffraction studies have revealed that the bulk dissolution of LDH occurs with no preferential leaching of the 57Co2+ or 67Ga3+ metal species from the crystal structure. Furthermore, the present study clearly demonstrates how radiolabeling methodologies described here may be adapted for use in other similar clay systems and allow for the first time noninvasive imaging and monitoring of the fate of nanoparticles. © 2010, American Chemical Society