Sustainable and surfactant-free high-throughput synthesis of highly dispersible zirconia nanocrystals

Herein, a cost-effective and tailored synthesis route for the preparation of cubic ZrO$_2$ nanocrystals with high dispersibility (up to 45% by weight in H$_2$O) is reported. The procedure is straightforward and produces uniform 2–3 nm particles of a high yield of up to 98% when applying microwave dielectric heating as a “green” method. Furthermore, it can be applied to a wide range of batch sizes (from 0.5 to 20 g ZrO$_2$), which makes it interesting for industrial applications, and also lends itself to the preparation of yttria-stabilized ZrO$_2$ nanocrystals with varying doping levels. Overall, the paper aims at unravelling all relevant reaction steps by means of nuclear magnetic resonance and gas chromatography-mass spectrometry. Two innovative synthesis routes are presented, which have not been considered in previous studies. Both the microstructure and chemical composition of the nanoparticles were analyzed via electron microscopy, X-ray diffraction and dynamic light scattering as well as Raman, X-ray absorption and X-ray photoelectron spectroscopy. Besides, it is demonstrated that alcoholic ZrO$_2$ dispersions are highly suited for the preparation of nanoscale materials with different morphologies, including fibers as well as ordered mesoporous and macroporous thin films and powders. Collectively, this work provides a blueprint for the fabrication of high-quality nanoparticles and structured materials thereof and is likely to trigger further research in the field of solution-processed metal oxides