title: Stimuli-Responsive Shapeshifting Mesoporous Silica Nanoparticles.
abstract: Stimuli-responsive materials have attracted great interest in catalysis, sensing, and drug delivery applications and are typically constituted by soft components. We present a one-pot synthetic method for a type of inorganic silica-based shape change material that is responsive to water vapor exposure. After the wetting treatment, the cross-sectional shape of aminated mesoporous silica nanoparticles (MSNs) with hexagonal pore lattice changed from hexagonal to six-angle-star, accompanied by the loss of periodic mesostructural order. Nitrogen sorption measurements suggested that the wetting treatment induced a shrinkage of mesopores resulting in a broad size distribution and decreased mesopore volume. Solid-state (29)Si nuclear magnetic resonance (NMR) spectroscopy of samples after wetting treatment displayed a higher degree of silica condensation, indicating that the shape change was associated with the formation of more siloxane bonds within the silica matrix. On the basis of material characterization results, a mechanism for the observed anisotropic shrinkage is suggested based on a buckling deformation induced by capillary forces in the presence of a threshold amount of water vapor available beyond a humidity of about 50%. The work presented here may open a path toward novel stimuli-responsive materials based on inorganic components.
authors.forename: Yao
authors.initials: Y
authors.lastname: Sun
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sai
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Spoth
authors.forename: Kwan Wee
authors.initials: KW
authors.lastname: Tan
authors.affiliation: Department of Chemistry, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Werner-Zwanziger
authors.affiliation: Department of Chemistry, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Josef
authors.initials: J
authors.lastname: Zwanziger
authors.affiliation: Kavli Institute at Cornell for Nanoscale Science , Ithaca, New York 14853, United States.
authors.forename: Sol M
authors.initials: SM
authors.lastname: Gruner
authors.affiliation: Kavli Institute at Cornell for Nanoscale Science , Ithaca, New York 14853, United States.
authors.forename: Lena F
authors.initials: LF
authors.lastname: Kourkoutis
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wiesner
mesh_terms: D016503:Drug Delivery Systems; D006801:Humans; D006813:Humidity; D009682:Magnetic Resonance Spectroscopy; D053758:Nanoparticles / Q000737:chemistry*; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide
keywords: capillary force; mesoporous silica; nanoparticles; shape change; stimuli-responsive