title: Functionalized organosilica microspheres via a novel emulsion-based route.
abstract: Thiol-functionalized organosilica microspheres were synthesized via a two-step process: (1) acid-catalyzed hydrolysis and condensation of 3-mercaptopropyltrimethoxysilane (MPTMS), followed by (2) base-catalyzed condensation, which led to the rapid formation of emulsion droplets with a narrow size distribution. These droplets continued to condense to form solid microspheres. Solution (29)Si NMR and optical microscopy were applied to study the mechanism of this novel synthetic route. Solid-state (29)Si NMR, SEM, zeta potential titration, and Coulter counter measurements were used to study the bulk and surface properties and to determine the particle size distributions of the final microspheres. Compared to conventional Stöber silica particles, these microspheres were shown to have a lower degree of cross-linking (average degree of condensation, r = 1.25), a larger average size (up to 6 microm), and a higher isoelectric point (pH = 4.4). Confocal microscopy of dye-labeled microspheres showed an even distribution of dye molecules throughout the interior, characteristic of a readily accessible and permeable organosilica network. These findings have implications for the production of functionalized solid supports for use in catalysis and biological applications, such as optically encoded carriers for combinatorial synthesis.
authors.affiliation: Centre for Nanotechnology and Biomaterials, Department of Chemistry, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Chris R
authors.initials: CR
authors.lastname: Miller
authors.forename: Robert
authors.initials: R
authors.lastname: Vogel
authors.forename: Peter P T
authors.initials: PP
authors.lastname: Surawski
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Jack
authors.forename: Simon R
authors.initials: SR
authors.lastname: Corrie
authors.forename: Matt
authors.initials: M
authors.lastname: Trau
mesh_terms: D004396:Coloring Agents / Q000737:chemistry; D004655:Emulsions; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D009930:Organic Chemicals / Q000737:chemistry*; D011199:Potentiometry; D012822:Silicon Dioxide; D012996:Solutions
chemical_list: D004396:Coloring Agents; D004655:Emulsions; D009930:Organic Chemicals; D012996:Solutions; D012822:Silicon Dioxide