Abstract
Anisotropic magnetic nanoparticles with a mesoporous silica shell have the combined merits of a magnetic core and a robust shell. Preparation of magnetically guidable core–shell nanostructures with a robust silica shell that contains well-defined, large, radially aligned silica pores is challenging, and hence this has rarely been described in detail. Herein, a dynamic soft-templating strategy is developed to controllably synthesize hierarchical, dual-mesoporous silica shells on diverse core nanoparticles, in terms of nanoparticle shape (i.e., spherical, chainlike, and disclike), magnetic properties (i.e., hard magnetic and superparamagnetic), and dimensions (i.e., from 3 nm to submicrometers). The developed interfacial coassembly method allows easy design of applicable silica shells containing tunable pore geometries with pore sizes ranging from below 5 nm to above 40 nm, with a specific surface area of 577 m2 g–1 and pore volume of 1.817 cm3 g–1. These are the highest values reported for magnetically guidable anisotropic nanoparticles. The versatility of the method is shown by transfer of the coating procedure to core particles as diverse as spherical superparamagnetic nanoparticles and their clusters as well as by ferromagnetic 3 nm thick hexaferrite nanoplatelets. This method can serve as a general approach for the fabrication of well-designed mesoporous silica coatings on a wide variety of core nanoparticles.
Highlights
Organized and well-defined mesoporous materials are desired support for applications as diverse as those ranging from catalysis, energy harvesting, and water and soil remediation to medical applications such as targeted drug delivery.[1−3] Frequently, mesoporous materials have been designed to carry large amounts of functional molecules, ions, or catalysts on the basis of their inherent high surface area and large pore size and volume.[4]
This study reveals the effects of each of the individual synthesis parameters on growth of these radially aligned silica pores on the surface of the magnetic nanochains, including for surfactant concentration, type and amount of catalyst and organic solvent, amount of silica precursor, reaction temperature and time, and stirring intensity
A general procedure was developed for synthesis of the mesoporous silica shell on all three types of core nanoparticles used in this study
Summary
Organized and well-defined mesoporous materials are desired support for applications as diverse as those ranging from catalysis, energy harvesting, and water and soil remediation to medical applications such as targeted drug delivery.[1−3] Frequently, mesoporous materials have been designed to carry large amounts (by weight) of functional molecules, ions, or catalysts on the basis of their inherent high surface area and large pore size and volume.[4] Among the different porous materials available, such as zeolites, metal− organic frameworks, and nanocarbons, mesoporous silica-based nanoarchitectures represent the first choice for many applications. Hard templating is limited to preformed templates, and removal of the solid colloids is usually very challenging and time-
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