a b s t r a c tWe have shown that Ca(OH) 2 solution is a natural stabilizer for CaCO 3 particles. We designed a CO 2 bubbling crystallization reactor to produce nano-CaCO 3 particles in homogenous size distribution without aggregation. In the experimental set-up, the crystallization region was separated from the stabilization region. The produced nanoparticles were removed from the crystallization region into the stabilization region before aggregation or crystal growth. It was shown that rice-like hollow nano-CaCO 3 particles in about 250 nm in size were produced with almost monodispersed size distribution. The particles started to dissolve through their edges as CO 2 bubbles were injected, which opened-up the pores inside the particles. At the late stages of crystallization, the open pores were closed as a result of dissolution-recrystallization of the newly synthesized CaCO 3 particles. These particles were stable in Ca(OH) 2 solution and no aggregation was detected. The present methodology can be used in drug encapsulation into inorganic CaCO 3 particles for cancer treatment with some modifications.

h i g h l i g h t s• We showed that the Ca(OH) 2 solution is a natural stabilized for the newly synthesized nano-CaCO 3 particles.• A new methodlogy was introduced to produce stable hollow nano-CaCO 3 particles.• This methodlogy can be modified for drug loading within inorganic CaCO 3 particles.