A General Strategy\nfor Controllable Preparation of\nNano-CaCO<sub>3</sub>

Controllable\npreparation of inorganic nanomaterials with\nspecific\nmorphology and structure is very important for their applications\nin various fields. Herein, a general strategy was proposed to controllably\nsynthesize nano-CaCO<sub>3</sub> via a water-in-oil microemulsion\nmethod in the rotating packed bed reactor. By tuning key parameters,\nnano-CaCO<sub>3</sub> with four primarily analyzed morphologies, including\nspherical, spindle-like, clustered, or linear formations, can be selectively\nobtained. The diameters of the nanospheres are adjustable within the\nrange of 4–20 nm, and the lengths of the nanowires can be tuned\nfrom 100 to 800 nm. Notably, nano-CaCO<sub>3</sub> with four crystal\nforms, amorphous, vaterite, aragonite, and calcite, can also be controllably\nsynthesized. Importantly, these prepared nano-CaCO<sub>3</sub> have\nexcellent dispersity, which can be well-dispersed in dozens of types\nof liquid media to form transparent or semitransparent nanodispersions.\nThis work provides a general method for producing nanomaterials, enabling\nprecise control over the desired morphology and structure and ensuring\ncommendable dispersibility, which can greatly foster broader preparations\nand applications of nanomaterials in the fields.