title: A New Insight into Growth Mechanism and Kinetics of Mesoporous Silica Nanoparticles by in Situ Small Angle X-ray Scattering.
abstract: The growth mechanism and kinetics of mesoporous silica nanoparticles (MSNs) were investigated for the first time by using a synchrotron time-resolved small-angle X-ray scattering (SAXS) analysis. The synchrotron SAXS offers unsurpassed time resolution and the ability to detect structural changes of nanometer sized objects, which are beneficial for the understanding of the growth mechanism of small MSNs (∼20 nm). The Porod invariant was used to quantify the conversion of tetraethyl orthosilicate (TEOS) in silica during MSN formation, and the growth kinetics were investigated at different solution pH and temperature through calculating the scattering invariant as a function of reaction time. The growth of MSNs was found to be accelerated at high temperature and high pH, resulting in a higher rate of silica formation. Modeling SAXS data of micelles, where a well-defined electrostatic interaction is assumed, determines the size and shape of hexadecyltrimethylammonium bromide (CTAB) micelles before and after the addition of TEOS. The results suggested that the micelle size increases and the micelle shape changes from ellipsoid to spherical, which might be attributed to the solubilization of TEOS in the hydrophobic core of CTAB micelles. A new "swelling-shrinking" mechanism is proposed. The mechanism provides new insights into understanding MSN growth for the formation of functional mesoporous materials exhibiting controlled morphologies. The SAXS analyses were correlated to the structure of CTAB micelles and chemical reaction of TEOS. This study has provided critical information to an understanding of the growth kinetics and mechanism of MSNs.
authors.affiliation: †Institute for Frontier Materials, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Yi
authors.affiliation: †Institute for Frontier Materials, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: Ludovic F
authors.initials: LF
authors.lastname: Dumée
authors.affiliation: ‡Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234, Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Garvey
authors.affiliation: †Institute for Frontier Materials, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: Chunfang
authors.initials: C
authors.lastname: Feng
authors.affiliation: †Institute for Frontier Materials, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: Fenghua
authors.initials: F
authors.lastname: She
authors.affiliation: §Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: James E
authors.initials: JE
authors.lastname: Rookes
authors.affiliation: ∥Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3169, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Mudie
authors.affiliation: §Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Cahill
authors.affiliation: †Institute for Frontier Materials, Deakin University, Geelong Campus at Waurn Ponds, Geelong, Victoria 3216, Australia.
authors.forename: Lingxue
authors.initials: L
authors.lastname: Kong
mesh_terms: D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D016062:Porosity; D053838:Scattering, Small Angle; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D012822:Silicon Dioxide