ZrO2, CaCO3, and Fe4[Fe(CN)6]3 Hollow Nanospheres via Gelatin‐stabilized Microemulsions

Abstract

AbstractZrO2, CaCO3, and Fe4[Fe(CN)6]3 hollow nanospheres are prepared via gelatin‐stabilized microemulsions. ZrO2 and CaCO3 hollow spheres exhibit outer diameters of 10–20 nm, a thickness of the sphere wall of 4 nm and an inner cavity diameter of 6–12 nm; Fe4[Fe(CN)6]3 is with outer diameters of 50–60 nm, a wall thickness of 15 nm, and an inner cavity diameter of 25–30 nm. The hollow nanospheres turn out as readily crystalline although prepared at room‐temperature. Gelatin increases the viscosity of the polar micelle phase and thereby reduces the diffusion in the water phase. This measure is essential to obtain hollow spheres and to avoid the formation of massive nanoparticles. All as‐prepared hollow nanospheres are characterized by different electron microscopic techniques (STEM, HRTEM), infrared spectroscopy (FT‐IR), thermogravimetry (TG), and X‐ray diffraction (XRD). In the case of ZrO2, the hollow sphere structure is even maintained after thermal removal of gelatin at 600 °C. Moreover, CO2 sorption analysis shows reversible CO2 uptake of 96 mg·g–1 (80 bar, 50°°C) at a specific surface area of 98 m2·g–1. As the adsorption of N2 is much lower (17 mg·g–1 at 80 bar, 50°°C), the ZrO2 hollow nanospheres can be interesting for CO2‐N2 separation as well as catalytical reactions with CO2. All hollow nanospheres, and especially CaCO3, can become relevant for drug delivery and release.