title: Control and formation mechanism of extended nanochannel geometry in colloidal mesoporous silica particles.
abstract: A large class of colloidal multi-micron mesoporous silica particles have well-defined cylindrical nanopores, nanochannels which self-assembled in the templated sol-gel process. These particles are of broad interest in photonics, for timed drug release, enzyme stabilization, separation and filtration technologies, catalysis, etc. Although the pore geometry and mechanism of pore formation of such particles has been widely investigated at the nanoscale, their pore geometry and its formation mechanism at a larger (extended) scale is still under debate. The extended geometry of nanochannels is paramount for all aforementioned applications because it defines accessibility of nanochannels, and subsequently, kinetics of interaction of the nanochannel content with the particle surrounding. Here we present both experimental and theoretical investigation of the extended geometry and its formation mechanism in colloidal multi-micron mesoporous silica particles. We demonstrate that disordered (and consequently, well accessible) nanochannels in the initially formed colloidal particles gradually align and form extended self-sealed channels. This knowledge allows to control the percentage of disordered versus self-sealed nanochannels, which defines accessibility of nanochannels in such particles. We further show that the observed aligning the channels is in agreement with theory; it is thermodynamically favored as it decreases the Gibbs free energy of the particles. Besides the practical use of the obtained results, developing a fundamental understanding of the mechanisms of morphogenesis of complex geometry of nanopores will open doors to efficient and controllable synthesis that will, in turn, further fuel the practical utilization of these particles.
authors.affiliation: Department of Mechanical Engineering, Tufts University, 200 College ave., Medford, MA 02155, USA. igor.sokolov@tufts.edu and Department of Biomedical Engineering, Department of Physics, Tufts University, 547 Boston ave., Medford, MA 02155, USA and Department of Physics, Tufts University, 547 Boston ave., Medford, MA 02155, USA.
authors.forename: I
authors.identifier: http://orcid.org/0000-0001-6260-4326
authors.initials: I
authors.lastname: Sokolov
authors.affiliation: Department of Mechanical Engineering, Tufts University, 200 College ave., Medford, MA 02155, USA. igor.sokolov@tufts.edu.
authors.forename: V
authors.initials: V
authors.lastname: Kalaparthi
authors.affiliation: Department of Mechanical Engineering, Tufts University, 200 College ave., Medford, MA 02155, USA. igor.sokolov@tufts.edu and Air Force Civil Engineer Center, Tyndall AFB, Panama City, FL, USA.
authors.forename: D O
authors.initials: DO
authors.lastname: Volkov
authors.affiliation: Department of Mechanical Engineering, Tufts University, 200 College ave., Medford, MA 02155, USA. igor.sokolov@tufts.edu.
authors.forename: S
authors.initials: S
authors.lastname: Palantavida
authors.affiliation: Department of Chemistry, Moscow State University, Moscow 119899, Russia and Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, 6 bd du Maréchal Juin, 14050 CAEN Cedex 4, France.
authors.forename: N E
authors.initials: NE
authors.lastname: Mordvinova
authors.affiliation: Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, 6 bd du Maréchal Juin, 14050 CAEN Cedex 4, France.
authors.forename: O I
authors.initials: OI
authors.lastname: Lebedev
authors.affiliation: Air Force Civil Engineer Center, Tyndall AFB, Panama City, FL, USA.
authors.forename: J
authors.initials: J
authors.lastname: Owens