Accepted Manuscript Preparation of core–shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method Hirotaka Ishii, Takaaki Ikuno, Atsushi Shimojima, Tatsuya Okubo PII: DOI: Reference:
S0021-9797(15)00103-4 http://dx.doi.org/10.1016/j.jcis.2015.01.057 YJCIS 20199
To appear in:
Journal of Colloid and Interface Science
Received Date: Accepted Date:
20 November 2014 21 January 2015
Please cite this article as: H. Ishii, T. Ikuno, A. Shimojima, T. Okubo, Preparation of core–shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method, Journal of Colloid and Interface Science (2015), doi: http://dx.doi.org/10.1016/j.jcis.2015.01.057
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Preparation of core–shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method Hirotaka Ishii, Takaaki Ikuno, Atsushi Shimojima†, and Tatsuya Okubo*
Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, [email protected] †Present address: Department of Applied Chemistry, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
Abstract Core–shell structured mesoporous silica nanoparticles (MSNs) with different pore characteristics in the cores and shells have been prepared by the regrowth method.
Adding a
silica source to a dispersion of presynthesized silica–surfactant composite nanoparticles with two-dimensional hexagonal mesostructures results in regrowth in preference to generation of new particles. Core–shell MSNs with bimodal porosities are easily obtained by adding a pore-expanding agent, 1,3,5-trimethylbenzene, in either the core or shell formation step. Detailed characterization of the core–shell MSNs reveals that the shells consist of disordered arrangements of relatively large or small pores and that the pore sizes in the cores change when the shells formed. Core–shell MSNs will be useful for controlling the release rates of the encapsulated guest molecules and for protecting internal pores from being plugged by other species.
Keywords: Mesoporous silica nanoparticles, core–shell structure, pore size control
1. Introduction Mesoporous silica nanoparticles (MSNs) have received considerable attention because of their wide range of potential applications such as catalysis, adsorption, drug delivery systems, 1
bioimaging, and anti-reflective coatings [1–6]. MSNs with tunable sizes and internal pore structures have been prepared by the reactions at low surfactant concentrations [7], by adding diols [8], by using different types of base catalysts [9–11], by using dual surfactants [12,13], and by the reactions in biphasic emulsion systems [10,11].
Organically modified MSNs
have also been prepared using organoalkoxysilanes as precursors [13–16]. core–shell structures are very important in advanced applications [17].
MSNs with
Core–shell MSNs
with metal and metal oxide cores have been prepared for use as nanocatalysts [18,19] and nanocarriers [3]. Selective functionalization of the inner and outer regions of the MSNs with different organosilanes has been achieved by the co-condensation method [20]. Core–shell nanoparticles can also be used for producing hollow MSNs by selective etching of the cores [21–23]. Core–shell MSNs with bimodal pore size distributions, i.e., with different pore sizes in cores and shells, are crucial in several applications. For example, relatively large pores increase the porosity of MSNs used as fillers in anti-reflective coatings [6], but they allow the polymer matrix to infiltrate the mesopores; this can be ameliorated using core–shell MSNs with smaller pores in the shell. Such core–shell MSNs are also useful as drug carriers for controlling the release rate while maintaining a high drug loading capacity. There have been a few studies on the successful preparation of such core–shell MSNs using the dual-templating method.
Areva et al. reported aerosol-assisted synthesis of core–shell
MSNs with a bimodal pore structure using a nonionic PEO-PPO-PEO-type triblock copolymer (F127) and cationic fluorocarbon surfactant as a co-template [24].
Niu et al.
synthesized core–shell structured MSNs with large pores in the cores and both large and small pores in the shells using an amphiphilic block copolymer (polystyrene-b-poly(acrylic acid)) and cetyltrimethylammonium bromide (CTAB) [25]. Most recently, Shen et al. reported the preparation of dendritic MSNs with radial mesopores, where the pore size of each generation can be adjusted using varied hydrophobic solvents in the oil–water biphasic systems [26]. Nonetheless, the variation of the pore characteristics of bimodal MSNs has been still limited. In addition, the previous methods have not been able to produce monodispersed MSNs of 2
diameters less than 100 nm that are desired for applications in drug delivery systems and nanocoatings. In this study, we demonstrate the preparation of relatively small (
S0021-9797(15)00103-4 http://dx.doi.org/10.1016/j.jcis.2015.01.057 YJCIS 20199
To appear in:
Journal of Colloid and Interface Science
Received Date: Accepted Date:
20 November 2014 21 January 2015
Please cite this article as: H. Ishii, T. Ikuno, A. Shimojima, T. Okubo, Preparation of core–shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method, Journal of Colloid and Interface Science (2015), doi: http://dx.doi.org/10.1016/j.jcis.2015.01.057
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Preparation of core–shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method Hirotaka Ishii, Takaaki Ikuno, Atsushi Shimojima†, and Tatsuya Okubo*
Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, [email protected] †Present address: Department of Applied Chemistry, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
Abstract Core–shell structured mesoporous silica nanoparticles (MSNs) with different pore characteristics in the cores and shells have been prepared by the regrowth method.
Adding a
silica source to a dispersion of presynthesized silica–surfactant composite nanoparticles with two-dimensional hexagonal mesostructures results in regrowth in preference to generation of new particles. Core–shell MSNs with bimodal porosities are easily obtained by adding a pore-expanding agent, 1,3,5-trimethylbenzene, in either the core or shell formation step. Detailed characterization of the core–shell MSNs reveals that the shells consist of disordered arrangements of relatively large or small pores and that the pore sizes in the cores change when the shells formed. Core–shell MSNs will be useful for controlling the release rates of the encapsulated guest molecules and for protecting internal pores from being plugged by other species.
Keywords: Mesoporous silica nanoparticles, core–shell structure, pore size control
1. Introduction Mesoporous silica nanoparticles (MSNs) have received considerable attention because of their wide range of potential applications such as catalysis, adsorption, drug delivery systems, 1
bioimaging, and anti-reflective coatings [1–6]. MSNs with tunable sizes and internal pore structures have been prepared by the reactions at low surfactant concentrations [7], by adding diols [8], by using different types of base catalysts [9–11], by using dual surfactants [12,13], and by the reactions in biphasic emulsion systems [10,11].
Organically modified MSNs
have also been prepared using organoalkoxysilanes as precursors [13–16]. core–shell structures are very important in advanced applications [17].
MSNs with
Core–shell MSNs
with metal and metal oxide cores have been prepared for use as nanocatalysts [18,19] and nanocarriers [3]. Selective functionalization of the inner and outer regions of the MSNs with different organosilanes has been achieved by the co-condensation method [20]. Core–shell nanoparticles can also be used for producing hollow MSNs by selective etching of the cores [21–23]. Core–shell MSNs with bimodal pore size distributions, i.e., with different pore sizes in cores and shells, are crucial in several applications. For example, relatively large pores increase the porosity of MSNs used as fillers in anti-reflective coatings [6], but they allow the polymer matrix to infiltrate the mesopores; this can be ameliorated using core–shell MSNs with smaller pores in the shell. Such core–shell MSNs are also useful as drug carriers for controlling the release rate while maintaining a high drug loading capacity. There have been a few studies on the successful preparation of such core–shell MSNs using the dual-templating method.
Areva et al. reported aerosol-assisted synthesis of core–shell
MSNs with a bimodal pore structure using a nonionic PEO-PPO-PEO-type triblock copolymer (F127) and cationic fluorocarbon surfactant as a co-template [24].
Niu et al.
synthesized core–shell structured MSNs with large pores in the cores and both large and small pores in the shells using an amphiphilic block copolymer (polystyrene-b-poly(acrylic acid)) and cetyltrimethylammonium bromide (CTAB) [25]. Most recently, Shen et al. reported the preparation of dendritic MSNs with radial mesopores, where the pore size of each generation can be adjusted using varied hydrophobic solvents in the oil–water biphasic systems [26]. Nonetheless, the variation of the pore characteristics of bimodal MSNs has been still limited. In addition, the previous methods have not been able to produce monodispersed MSNs of 2
diameters less than 100 nm that are desired for applications in drug delivery systems and nanocoatings. In this study, we demonstrate the preparation of relatively small (
