Dynamics of Water Confined on the Surface of Titania and Cassiterite Nanoparticles
- PDF / 305,445 Bytes
- 10 Pages / 432 x 648 pts Page_size
- 59 Downloads / 186 Views
Dynamics of Water Confined on the Surface of Titania and Cassiterite Nanoparticles Nancy L. Ross,1 Elinor C. Spencer,1 Andrey A. Levchenko,2 Alexander I. Kolesnikov,3 Douglas L. Abernathy,3 Juliana Boerio-Goates,4 Brian F. Woodfield,4 Alexandra Navrotsky,5 Guangshe Li,6 Wei Wang,7 David J. Wesolowski7 1 Dept. of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, U.S.A. 2 Setaram Inc., 8430 Central Ave., Suite C and 3D, Newark, California 94560 3 Neutron Scattering Sciences Division, Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, U.S.A. 4 Dept. of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 5 Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, California 95616, U.S.A. 6 State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Science, Fuzhou 350002, P. R. China. 7 Chemical Science Division, Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, U.S.A. ABSTRACT We present low-temperature inelastic neutron scattering spectra collected on two metal oxide nanoparticle systems, isostructural TiO2 rutile and SnO2 cassiterite, between 0-550 meV. Data were collected on samples with varying levels of water coverage, and in the case of SnO2, particles of different sizes. This study provides a comprehensive understanding of the structure and dynamics of the water confined on the surface of these particles. The translational movement of water confined on the surface of these nanoparticles is suppressed relative to that in ice-Ih and water molecules on the surface of rutile nanoparticles are more strongly restrained that molecules residing on the surface of cassiterite nanoparticles. The INS spectra also indicate that the hydrogen bond network within the hydration layers on rutile is more perturbed than for water on cassiterite. This result is indicative of stronger water-surface interactions between water on the rutile nanoparticles than for water confined on the surface of cassiterite nanoparticles. These differences are consistent with the recently reported differences in the surface energy of these two nanoparticle systems. INTRODUCTION Metal oxide nanoparticles have potential application in a number of important fields such as catalysis, environmental remediation, energy conversion and sensor technology.1-4 The existence of hydration layers on their surface can play a critical role in stabilizing the nanoparticle5-7, yet the dynamics and physical properties of water are altered with respect to bulk by confining it to nanoscale domains, surfaces, or interfaces.8,9 Thus the development of stable nanoparticles for practical uses requires that the properties of these hydration layers be assessed. The large incoherent neutron scattering cross-section of hydrogen relative to transition metals and the absence of selection rules ensures that inelastic neutron scattering (INS) techniques are ideal for probing the dynamics of the nanoparticle hydration layers
Data Loading...
