title: Outset of the Morphology of Nanostructured Silica Particles during Nucleation Followed by Ultrasmall-Angle X-ray Scattering.
abstract: Nucleation and growth of SBA-15 silica nanostructured particles with well-defined morphologies has been followed with time by small-angle X-ray scattering (SAXS) and ultrasmall-angle X-ray scattering (USAXS), using synchrotron radiation. Three different morphologies have been compared: platelets, toroids, and rods. SEM observations of the particles confirm that two key physical parameters control the morphology: the temperature and the stirring of the solution. USAXS curves demonstrate that primary particles with a defined shape are present very early in the reaction mixture, immediately after a very fast nucleation step. This nucleation step is detected at 10 min (56 °C) or 15 min (50 °C) after the addition of the silica precursor. The main finding is that the USAXS signal is different for each type of morphology, and we demonstrate that the difference is related to the shape of the particles, showing characteristic form factors for the different morphologies (platelet, toroid, and rod). Moreover, the size of the mesocrystal domains is correlated directly with the particle dimensions and shape. When stirred, aggregation between primary particles is detected even after 12 min (56 °C). The platelet morphology is promoted by constant stirring of the solution, through an oriented aggregation step between primary particles. In contrast, toroids and rods are only stabilized under static conditions. However, for toroids, aggregation is detected almost immediately after nucleation.
authors.affiliation: Laboratoire de Physique de Solides, CNRS, Université Paris-Sud, Université Paris-Saclay , 91400 Orsay, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Schmitt
authors.affiliation: Physical Chemistry, Lund University , P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kjellman
authors.affiliation: ID2 beamline, ESRF , 71 avenue des Martyrs, F-38043 Grenoble, France.
authors.forename: Paweł
authors.initials: P
authors.lastname: Kwaśniewski
authors.affiliation: SWING beamline, Synchrotron Soleil , BP 48, F-91192 Gif-sur-Yvette, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Meneau
authors.affiliation: Department of Chemistry and iNANO Interdisciplinary Nanoscience Center, Århus University , DK-8000 Århus, Denmark.
authors.forename: Jan Skov
authors.initials: JS
authors.lastname: Pedersen
authors.affiliation: Department of Chemistry, University of Bath , Bath BA2 7AY, United Kingdom.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Edler
authors.affiliation: Department of Physics and Astronomy, Ångström Laboratory, Uppsala University , P.O. Box 516, SE-751 21 Uppsala, Sweden.
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Rennie
authors.affiliation: Physical Chemistry, Lund University , P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Viveka
authors.initials: V
authors.lastname: Alfredsson
authors.affiliation: Laboratoire de Physique de Solides, CNRS, Université Paris-Sud, Université Paris-Saclay , 91400 Orsay, France.
authors.forename: Marianne
authors.initials: M
authors.lastname: Impéror-Clerc