Monodisperse mesoporous silica nanoparticles of distinct topology

Leilei Luo; Yucang Liang; Egil Sev Erichsen; Reiner Anwander

doi:10.1016/j.jcis.2017.01.107

Monodisperse mesoporous silica nanoparticles of distinct topology

J Colloid Interface Sci. 2017 Jun 1:495:84-93. doi: 10.1016/j.jcis.2017.01.107. Epub 2017 Jan 31.

Authors

Leilei Luo¹, Yucang Liang², Egil Sev Erichsen³, Reiner Anwander⁴

Affiliations

¹ Institut für Anorganische Chemie, Universität Tübingen, Auf der Morgenstelle 18, Tübingen 72076, Germany.
² Institut für Anorganische Chemie, Universität Tübingen, Auf der Morgenstelle 18, Tübingen 72076, Germany. Electronic address: yucang.liang@uni-tuebingen.de.
³ Laboratory for Electron Microscopy, University of Bergen, Allégaten 41, Bergen 5007, Norway.
⁴ Institut für Anorganische Chemie, Universität Tübingen, Auf der Morgenstelle 18, Tübingen 72076, Germany. Electronic address: reiner.anwander@uni-tuebingen.de.

PMID: 28189113
DOI: 10.1016/j.jcis.2017.01.107

Abstract

Monodisperse and uniform high-quality MCM(Mobil Composition of Matter)-48-type CMSNs (Cubic Mesoporous Silica Nanoparticles) are readily prepared by simply optimizing the molar ratio of ethanol and surfactant in the system TEOS-CTAB-NaOH-H₂O-EtOH (TEOS=tetraethyl orthosilicate, CTAB=cetyltrimethylammonium bromide, EtOH=ethanol). In the absence of ethanol only hexagonal mesoporous silica with ellipsoidal and spherical morphology are obtained. The presence of ethanol drives a mesophase transformation from hexagonal to mixed hexagonal/cubic, further to purely cubic, and finally to a mixed cubic/lamellar. This is accompanied by a morphology evolution involving a mixture of ellipses/spheres, regular rods, uniform spheres, and finally a mixture of spheres/flakes. Preserving the three-dimensional (3D) cubic MCM-48 structure, use of a small amount of ethanol is beneficial to the improvement of the monodispersity of the CMSNs. Moreover, the quality of the CMSNs can also be controlled by changing the surfactant concentration or adjusting the stirring rate. All MSNs were characterized using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and N₂ physisorption, indicating highly long-range ordered pore arrays, high specific surface areas (max. 1173 m²g^-1) as well as high pore volumes (max. 1.14 cm³g^-1). The monodispersity of the CMSNs was verified by statistical particle size distribution from SEM (scanning electron microscopy)/TEM (transmission electron microscopy) images and DLS (dynamic light scattering). The mesophase transformation can be rationalized on the basis of an ethanol-driven change of the surfactant packing structure and charge matching at the surfactant/silicate interface. The corresponding morphology evolution can be elucidated by an ethanol-controlled hydrolysis rate of TEOS and degree of condensation of oligomeric silicate species via a nucleation and growth process.

Keywords: MCM-48; Mesoporous silica; Monodispersity; Morphology; Nanoparticles; Topology.

Publication types

Research Support, Non-U.S. Gov't