NANOCAPSULE · Nanoengineered Chemical Synthesis Inside Restricted Volume of Nano- and Microsized Polyelectrolyte Capsules

Final Activity Report Summary - NANOCAPSULE (Nanoengineered chemical synthesis inside restricted volume of nano- and microsized polyelectrolyte capsules)

Polyelectrolyte capsules were used as templates for the in-situ synthesis of inorganic nanoparticles. The concentration and size of nanoparticles grown within the coatings can be tuned by the number of loading cycles, reaction conditions, and diameter of the capsule. We show that nanoparticles of different nature (nano-Ag, LaPO4:Eu, hydroxyapatite) can be synthesised via the nanoreactor scheme, where corresponding metal ions are loaded into the capsule lumen and then subsequently reacted with the second reagent in solution. UV-vis spectroscopy and direct observation by transmission electron microscopy confirm that the nanoparticles are well-dispersed within the capsule shell and lumen. Developed approach of nanoparticle synthesis selectively in the polyelectrolyte shell illustrates perspectives to explore these capsules as microreactors for spatially restricted (bio-) inorganic synthesis and mimicking biomineralisation processes occurred in nature. Nanomaterial synthesised in a confined multifunctional microreactor has several advantages: (i) absence of particle aggregates, (ii) amorphous or metastable crystal phases, (iii) unique composite inorganic/inorganic and inorganic/organic structure. Iron oxide nanoparticle/polymer microcapsules containing different quantity of iron oxide nanoparticles were made by spatially-confined synthesis on iron oxide inside polyelectrolyte shell. Microwave radiation leads to a permeability increase of both as prepared and thermally treated polyelectrolyte capsules with three, four and five Fe3O4 nanoparticle layers in the shell. The EPR spectra of microcapsules containing magnetite nanoparticles confirmed their high sensitivity on microwave irradiation. Microwave radiation initiates nanoparticle expulsion from the shell followed by formation of shell defects or full destruction and, as a consequence, provide remotely controlled release of the encapsulated materials. A novel approach for encapsulation of hydrophobic materials into a hydrophilic multifunctional shell is presented here based on combining ultrasonic technique and layer-by-layer protocol. Polyglutamate/polyethyleneimine(PEI) /polyacrylic acid(PAA) and polyglutamate/PEI/PAA/silver nanocontainers loaded with hydrophobic dye 5,10,15,20-tetraphenylporphin dissolved in toluene were fabricated. About 600 nm, uniform, stable and monodisperse polyglutamate/PEI/PAA nanocontainers were obtained. With sodium dodecyl sulfate as surfactant the amount of nanocontainers, their monodispersity and stability can be increased dramatically. The simple technology is full of prospect in medical application especially in drug delivery since the core of the nanocontainer might contain a great variety of water-insoluble drugs and the outer polyelectrolyte shell may have controlled permeability and desired multifunctionality. Sonochemical approach was effectively applied to prepare aqueous dispersion of air-filled nanostructured quartz silica shells from surface-engineered amorphous silica nanoparticles. The nonequilibrium nature of the cavitation process and high temperature and pressure in the cavitation microbubble can lead to the specific conditions at the cavitation interface resulting in partial crystallisation of the amorphous silica nanoparticles producing the quartz phase and in a high degree of interconnection between silica nanoparticles in the microsphere shell. The very high stability of the silica shells against collapse and aggregation is determined by the hydrophobic nature of the silica nanoparticles. Because of shell thickness and its high density caused by sintering of silica nanoparticles, the gas (liquid) permeability over the shell is practically limited making the prolonged life time of air-filled nanostructured silica shells. A new concept of an electrode system able to self-regulate the quantity of the materials (fuels) involved in the electrochemical process was demonstrated basing on the polyelectrolyte capsules modified with nanoparticles. Composite polyelectrolyte capsules incorporated into polypyrrole film can be reversibly reloaded by changing electric potential of the polypyrrole.

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