Critical roles of cationic surfactants in the preparation of colloidal mesostructured silica nanoparticles: control of mesostructure, particle size, and dispersion.

Mesoporous silica nanoparticles are promising materials for various applications, such as drug delivery and catalysis, but the functional roles of surfactants in the formation and preparation of mesostructured silica nanoparticles (MSN-as) remain to be seen. It was confirmed that the molar ratio of cationic surfactants to Si of alkoxysilanes (Surf/Si) can affect the degree of mesostructure formation (i.e., whether the mesochannels formed inside the nanoparticles actually pass through the outer surface of the particles), the particle diameter, and the dispersibility of MSN-as. Wormhole-like mesostructures formed with low Surf/Si ratios; however, the mesopores did not pass through the outer surface of the particles completely. At high Surf/Si ratios, the mesostructures extended. The particle diameter was 100 nm or larger at low Surf/Si ratios, and the primary particle diameter decreased as the Surf/Si ratio increased. This was because the surfactants enhanced the dispersity of the alkoxysilanes in water and the hydrolysis rate of the alkoxysilanes became faster, leading to an increased nucleation as compared to the particle growth. Moreover, primary particles aggregated at low Surf/Si ratios because of the hydrophobic interactions among the surfactants that were not involved in the mesostructure formation but were adsorbed onto the nanoparticles. At high Surf/Si ratios, the surfactant micelles were adsorbed on the surface of primary particles (admicelles), resulting in the dispersion of the particles due to electrostatic repulsion. In particular, molar ratios of 0.13 or higher were quite effective for the preparation of highly dispersed MSN-as. Surfactants played important roles in the mesostructure formation, decreasing the particle diameters, and the dispersibility of the particles. All of these factors were considerably affected by the Surf/Si ratio. The results suggested novel opportunities to control various colloidal mesostructured nanoparticles from the aspects of composition, structure, and morphology and will also be useful in the development of novel methods to prepare nanomaterials in various fields.

[1]  J. Mitchell,et al.  Mesoporous silica nanoparticles in nanotechnology , 2013, Critical reviews in biotechnology.

[2]  Y. Yamauchi,et al.  Preparation of aqueous colloidal mesostructured and mesoporous silica nanoparticles with controlled particle size in a very wide range from 20 nm to 700 nm. , 2013, Nanoscale.

[3]  V. Valtchev,et al.  Porous nanosized particles: preparation, properties, and applications. , 2013, Chemical reviews.

[4]  Jianlin Shi,et al.  In Vivo Bio‐Safety Evaluations and Diagnostic/Therapeutic Applications of Chemically Designed Mesoporous Silica Nanoparticles , 2013, Advanced materials.

[5]  Cecilia Sahlgren,et al.  Mesoporous silica nanoparticles in medicine--recent advances. , 2013, Advanced drug delivery reviews.

[6]  B. Lebeau,et al.  Ecodesign of ordered mesoporous silica materials. , 2013, Chemical Society reviews.

[7]  Si-Han Wu,et al.  Synthesis of mesoporous silica nanoparticles. , 2013, Chemical Society reviews.

[8]  Jing Wei,et al.  Large-pore ordered mesoporous materials templated from non-Pluronic amphiphilic block copolymers. , 2013, Chemical Society reviews.

[9]  S. Che,et al.  Anionic surfactant templated mesoporous silicas (AMSs). , 2013, Chemical Society reviews.

[10]  K. Lam,et al.  Facile large-scale synthesis of monodisperse mesoporous silica nanospheres with tunable pore structure. , 2013, Journal of the American Chemical Society.

[11]  Eric C. Carnes,et al.  Mesoporous silica nanoparticle nanocarriers: biofunctionality and biocompatibility. , 2013, Accounts of chemical research.

[12]  A. Elaissari,et al.  Silica-based nanoparticles for biomedical applications. , 2012, Drug discovery today.

[13]  J. Fraser Stoddart,et al.  Mesoporous Silica Nanoparticles in Biomedical Applications , 2012 .

[14]  G. Somorjai,et al.  Colloid chemistry of nanocatalysts: a molecular view. , 2012, Journal of colloid and interface science.

[15]  T. Tatsumi,et al.  Amino-functionalized mesoporous silica as base catalyst and adsorbent , 2012 .

[16]  Jun Lin,et al.  Functionalized mesoporous silica materials for controlled drug delivery. , 2012, Chemical Society reviews.

[17]  Y. Yamauchi,et al.  Preparation of Colloidal Mesoporous Silica Nanoparticles with Different Diameters and Their Unique Degradation Behavior in Static Aqueous Systems , 2012 .

[18]  Juan L. Vivero-Escoto,et al.  Silica-based nanoprobes for biomedical imaging and theranostic applications. , 2012, Chemical Society reviews.

[19]  K. Wu,et al.  Controlling physical features of mesoporous silica nanoparticles (MSNs) for emerging applications , 2012 .

[20]  Katie R. Hurley,et al.  Ultrastable, redispersible, small, and highly organomodified mesoporous silica nanotherapeutics. , 2011, Journal of the American Chemical Society.

[21]  T. Hyeon,et al.  Multifunctional mesoporous silica nanocomposite nanoparticles for theranostic applications. , 2011, Accounts of chemical research.

[22]  Courtney R. Thomas,et al.  Mechanized silica nanoparticles: a new frontier in theranostic nanomedicine. , 2011, Accounts of chemical research.

[23]  S. Arai,et al.  Aqueous colloidal mesoporous nanoparticles with ethenylene-bridged silsesquioxane frameworks. , 2011, Journal of the American Chemical Society.

[24]  Yasuto Hoshikawa,et al.  Mesoporous Silica Nanoparticles with Remarkable Stability and Dispersibility for Antireflective Coatings , 2010 .

[25]  Y. Yamauchi,et al.  Dialysis process for the removal of surfactants to form colloidal mesoporous silica nanoparticles. , 2009, Chemical communications.

[26]  C. Bain,et al.  Adsorption of CTAB on hydrophilic silica studied by linear and nonlinear optical spectroscopy. , 2008, Journal of the American Chemical Society.

[27]  Li Wang,et al.  Ethanol-Induced Formation of Silver Nanoparticle Aggregates for Highly Active SERS Substrates and Application in DNA Detection , 2008 .

[28]  A. Palmqvist,et al.  Particle Size Control of Colloidal Suspensions of Mesostructured Silica , 2008 .

[29]  Ying Wan,et al.  On the controllable soft-templating approach to mesoporous silicates. , 2007, Chemical reviews.

[30]  T. Bein,et al.  Colloidal Suspensions of Nanometer‐Sized Mesoporous Silica , 2007 .

[31]  D. Myers Solid Surfaces and Dispersions , 2005 .

[32]  H. Imai,et al.  Grain size control of mesoporous silica and formation of bimodal pore structures. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[33]  Xu Li,et al.  Pore structure characterization of large-pore periodic mesoporous organosilicas synthesized with varying SiO , 2004 .

[34]  E. Vansant,et al.  Plugged Hexagonal Templated Silica (PHTS): An In-Depth Study of the Structural Characteristics , 2004 .

[35]  R Atkin,et al.  Mechanism of cationic surfactant adsorption at the solid-aqueous interface. , 2003, Advances in colloid and interface science.

[36]  M. Jaroniec,et al.  Characterization of regular and plugged SBA-15 silicas by using adsorption and inverse carbon replication and explanation of the plug formation mechanism , 2003 .

[37]  B. Weckhuysen,et al.  Plugged hexagonal templated silica: a unique micro- and mesoporous composite material with internal silica nanocapsules. , 2002, Chemical communications.

[38]  P. Amorós,et al.  Generalised syntheses of ordered mesoporous oxides: the atrane route , 2000 .

[39]  J. Lu,et al.  Structure of an octadecyltrimethylammonium bromide layer at the air/water interface determined by neutron reflection : systematic errors in reflectivity measurements , 1993 .

[40]  C. Brinker,et al.  Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing , 1990 .

[41]  C. L. Frye,et al.  Pentacoordinate silicon compounds. V. Novel silatrane chemistry , 1971 .

[42]  Huan Meng,et al.  Mesoporous silica nanoparticles: A multifunctional nano therapeutic system. , 2013, Integrative biology : quantitative biosciences from nano to macro.

[43]  W. Stöber,et al.  Controlled growth of monodisperse silica spheres in the micron size range , 1968 .