Synthesis of highly spherical calcium carbonate nanoparticles using air nanobubbles as additives

Ultrasamll nanoparticles that simultaneously exhibit narrow size distribution and high circularity are key to enabling multifunctional applications in optoelectronic systems, integrated circuits and robots. Calcium carbonate (CaCO3) nanoparticles are typical nanomaterials with various shapes and sizes have found applications in both science and technology, while controlled synthetic approaches toward nanoparticles with high circularity remain challenging. Herein, we report the synthesis of spherical CaCO3 using air nanobubbles as additives in reactive precipitation. Air nanobubbles (<100 nm, stable >5 days) were generated via a rotating packed bed. During precipitation, these nanobubbles acted as immobile impurities, directing crystal growth. This yielded spherical CaCO3 nanoparticles (6.89±0.75 nm) with calcite structure and exceptional circularity (0.97). In situ liquid-phase TEM revealed the nanobubbles' role in inducing anomalous growth, providing deep insight into spherical nanoparticle synthesis for diverse applications.

同时兼具窄尺寸分布与高圆度的超小纳米颗粒，是支撑光电子系统、集成电路与机器人领域实现多功能应用的核心要素。碳酸钙（Calcium carbonate, CaCO₃）纳米颗粒是一类形貌与尺寸多样的典型纳米材料，已在科学研究与工程技术领域获得广泛应用，但开发制备高圆度纳米颗粒的可控合成方法仍颇具挑战。本研究采用反应沉淀法，以空气纳米气泡作为添加剂，成功合成了球形碳酸钙纳米颗粒。通过旋转填充床技术制备得到尺寸<100 nm、稳定时长超过5天的空气纳米气泡。在沉淀反应过程中，这类纳米气泡可作为非移动性杂质模板，引导晶体生长行为，最终得到具备方解石晶体结构、圆度高达0.97的球形碳酸钙纳米颗粒，其粒径为6.89±0.75 nm。通过原位液相透射电子显微镜（Transmission Electron Microscopy, TEM）观测，揭示了纳米气泡诱导异常晶体生长的作用机制，为面向多领域应用的球形纳米颗粒合成提供了深刻的理论见解。