Controlled preparation of micro–nano hierarchical hollow calcium carbonate microspheres by pressurized-CO 2 carbonization and their CaCO 3 :Eu 3+ photoluminescence properties

Herein, calcium carbonate hollow microspheres with a micro–nano hierarchical structure were successfully synthesized using disodium salt of ethylenediaminetetraacetic acid (EDTA-2Na) as an additive, by bubbling pressurized carbon dioxide and calcium hydroxide at 120 °C. The products were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis (TGA), fluorescence analysis, and X-ray fluorescence spectrometry. Characterization results showed that the hollow calcium carbonate microspheres were 4–6 μm in diameter and the micro–nano hierarchical structure with a 100 nm wall thickness assembled into cubic shape nanoparticles. The obtained microspheres were uniformly dispersed and exhibited an 18.79 m 2 g −1 surface area. Upon increasing the preparation temperature, the morphology of the microspheres changed from a hollow sphere to a hollow ellipsoid, while with an increasing EDTA content, the size of the product decreased. Fluorescence analysis results showed that with an increasing Eu 3+ content in the obtained hollow microspheres of CaCO 3 :Eu 3+ , the excitation and emission spectra and the photoluminescence intensity of the product increased achieving maximum luminescence intensity at 4% content.