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Posted: Jun 25, 2014
Eco-friendly versatile nanocapsules developed
(Nanowerk News) This new technology suggests a possible application of eco-friendly solvents that can address environmental, safety and economic issues all at once. Since various kinds of metal nanoparticles can be employed on the surface of polymer nanocapsules, it is also potentially useful for other applications in the field of nano-medicine and bioimaging.
Hollow polymer nanocapsules (PNs) made of cucurbit-uril (CB) serve as a versatile platform since various metal nanoparticles (NPs) can be introduced on the surface. They allow for a controlled synthesis, prevent self-aggregation, and provide high stability and dispersibility. Pd@CB-PNs show outstanding properties as heterogeneous catalysts in C-C and C-N bond-forming reactions in water.
The researchers have found that using polymer nanocapsules made of cucurbituril and metal salts can serve as a versatile platform where equal sized metal nanoparticles can be evenly distributed on the surface of the polymer nanocapsules. Cucurbituril has properties which strongly and selectively recognize organic and inorganic chemical species. This makes it possible to use it as a protecting agent which can stabilize metal nanoparticles by preventing them from clustering together. The metal-nanoparticle-decorated polymer nanocapsules exhibit the following properties in water: high stability for up to 6 months; high dispersibility; excellent catalytic activity; and reusability in carbon-carbon and carbon-nitrogen bond-forming reactions with 100% conversion efficiency.
Even though metal nanoparticles are variously used in industrial, pharmaceutical and agricultural (fertilizer) applications as a catalyst, toxic liquids such as toluene and hexane are usually used as solvents in the carbon-carbon and carbon-nitrogen bond-forming reactions. These toxic liquid solvents raise many issues for concern including environmental pollution, high cost of disposal, health problems and poisoning during the disposal process.
However, this new technology is able to replace those toxic liquids as it allows carbon-carbon and carbon-nitrogen bond-formation with the use of metal nanoparticles as a catalyst, which has high stability in environmentally preferable solvents such as water.
“The research results demonstrated that this new technology shows high stability, dispersibility, catalytic activity, and reusability in water, which other existing metal nanoparticles on solid supports have not been able to do," says Kimoon Kim, director of the Center for Self-assembly and Complexity at IBS. "It is important as it presents new possible applications in green solvents or bioimaging and nanomedicine fields.”