Pholsoinduced crystallization of calcium carbonate (CaCO3), which was based on the photodecarboxylation of ketoprolen (KP, 2-(3-benzoylphyenyl)propionic acid) under alkaline conditions of p1-1 8.4 and 10 was studied for preparation of CaCO3 composite particles in single-digit micrometer-sizes. In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVA(PS), degree of saponification: 86.5-89.0 mol%) was used as a precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. After the UV irradiation for 50 min, calcite spheroids in single-digit micrometer-sizes were obtained as major products at pH 8.4. The obtained calcite spheroids contained organic components of about 10 wt%. The comparison of the characteristics of the CaCO3 obtained at pH 8.4 and 10 suggests that the nucleation and crystallization of both vaterite and calcite continuously took place in a moderated supersaturation owing to the CO2 hydration equilibrium as long as he photoclecarboxylation of Kr continued. Consequently, the aggregation-based crystal growth in he presence of PVA(PS) seemed to enable the formation of the spheroidal composites of calcite in single-digit micrometer-sizes. (C) 2015 Elsevier B.V. All rights reserved.