RESUMO
Colloidosomes, also known as Pickering emulsion capsules, have attracted attention for encapsulation of hydrophilic and hydrophobic actives. However, current preparation methods are limited to single core structures and require the use of modified/engineered nanoparticles for forming the shell. Here, we report a fast, simple, and versatile method for producing multi-oil core silica colloidosomes via salt-driven assembly of purely hydrophilic commercial nanoparticles dispersed within an oil-in-water-in-oil (O/W/O) double emulsion template. The internal structure and overall diameter of the capsules can be adjusted by altering the primary and secondary emulsification conditions. With this approach, 7-35 µm diameter multicore colloidosomes containing 0.9-4.2 µm large oil cores were produced. The capsules can easily be functionalized depending on the type of nanoparticles used in the preparation process. Here, metal oxide nanoparticles, such as Fe3O4, TiO2, and ZnO, were successfully incorporated within the structure, conferring specific functional properties (i.e., magnetism and photocatalysis) to the final microcapsules. These capsules can also be ruptured by using ultrasound, enabling easy access to the internal core environments. Therefore, we believe this work offers a promising approach for producing multicore colloidosomes with adjustable structure and functionalities for the encapsulation of hydrophobic actives.
RESUMO
HYPOTHESIS: A green approach for producing magnetic photocatalysts via direct agglomeration of commercial nanoparticles in emulsion is shown. Aggregation is attributed to charge screening by salt addition which reduces stabilising repulsive forces between particles, and different nanoparticles (TiO2, Fe3O4 and SiO2) serve to imbue the final agglomerates with desired adsorption, photodegradation and magnetic properties. EXPERIMENT: Titania doped magnetic silica microbeads (TiO2/Fe3O4/SiO2) were produced at room temperature by CaCl2-induced aggregation of nanoparticles in a reverse emulsion template. The beads were characterized using optical microscopy, SEM, STEM, EDX and zeta potential measurements. The adsorption and photocatalytic properties of the system as well as its reusability were investigated using Rhodamine B and Methylene Blue as model pollutants. RESULTS: Magnetically responsive beads approximately 3-9 µm in diameter incorporating SiO2, TiO2 and Fe3O4 nanoparticles were produced. Adsorption and photodegradation properties of the beads were confirmed by bleaching solutions of Rhodamine B, Methylene Blue as well as mixtures of both dyes. Reusability of the beads after magnetic separation was demonstrated, exhibiting a dye removal efficiency greater than 93% per cycle for three consecutive cycles of UV-light irradiation. This method is simpler than conventional sol-gel methods and offers a green and easy to implement approach for producing structured functional materials.