Halloysite nanotubes as biomimetic nanoreactors

The reaction of urease-catalyzed deposition of CaCO3 from an aqueous solution containing CaCl2 and urea is taken as a model reaction to demonstrate the possibility of carrying out biomineralization processes inside halloysite nanotubes. Hollow lumen of urease-loaded halloysite nanotubes before CaCO3 precipitation. Synthesized CaCO3 completely fills inner halloysite lumens and exhibits metastable vaterite phase. The technique can find application as means of fabricating complex inorganic core/shell-type nanomaterials composed of two completely different substances ensuing from biomineralization reaction. The use of halloysite lumens with nanoscale volume as biomimetic nanoreactors provides possibilities for studying crystal engineering and fundamental aspects of biomineralization process. The results show that the increase in solution pH due to ammonia production during enzymatic reaction changed the absorption parameters of bremcresol purple.