Synthesis of hollow silica nanospheres with a microemulsion as the template

摘要

We demonstrate a sol-gel approach, using a water-in-oil microemulsion as the template, for the synthesis of hollow and yolk/shell silica nanospheres, which can encapsulate pre-formed hydrophobic nanoparticles, and we then explore these multifunctional hollow nanospheres in cell-labeling applications.rnHollow spherical silica nanoparticles are a class of nano-materials with potential applications in catalysis, separation, cell-labeling and drug delivery. The encapsulation of agents of various functionalities, such as photoactive, magnetic or catalytic properties, inside the hollow spheres would increase their potential applications. Hollow particles have been prepared from many templates, such as polystyrene spheres, emulsion droplets or vesicular structures. However, most of them are above 200 nm in size as in emulsion or vesicle templates. The large size is usually not effective for biomedical applications since cell uptake is limited. Another important requirement in biomedical application of nanoparticles is their aqueous suspensibility. For silica materials, the easy silica condensation reaction during the sol-gel process or calcination poses problems in making the particles sticking to each other to form bigger particles. Often, the high temperature removal of the template poses problems in solution suspension or destruction of encapsulated agents. Furthermore, after the hollow spheres are made, encapsulations of bigger agents such as enzymes or nanoparticles are usually difficult unless very delicate ship-in-bottle syntheses can be designed.