(255a) Microfluidic Synthesis of Titania Microparticles with Tunable Morphologies

Metal oxide microparticles, particularly titania (TiO₂), have attracted substantial attention for widespread utilization in a variety of applications ranging from photocatalysis to electrochemistry¹ due to unique intrinsic physicochemical and optoelectronic properties, including a moderate band gap and good charge transfer characteristics. Over the last three decades, various synthetic methods have been employed in titania synthesis, including solvothermal, sol-gel, emulsion, templating, and microfluidics.² However, the above methods each present different challenges for synthesizing high-quality monodisperse titania microspheres, including size limitations (≤3 μm), polydispersity, or complicated/labor-intensive synthetic methods.

In this work, we present a microfluidic strategy for facile, controlled synthesis of highly monodisperse titania microparticles with tunable morphology and phase composition, while achieving record-breaking surface areas for micron-sized particles.^2,3 The flow reactor is comprised of readily available off-the-shelf components and features a flow-focusing configuration. The developed microfluidic reactor enables continuous microparticle formation with excellent control over microparticle size, surface area, morphology, and crystallinity through the implementation of in-line photo crosslinking of a sacrificial polymeric scaffold. The combination of in-line photocuring and utilization of a polar aprotic solvent as the continuous phase in the microfluidic reactor enables excellent control over process-structure-properties of in flow-synthesized titania microparticles which were previously inaccessible due to the presence of water- and air-sensitive precursors. The available range of precursor compositions in the developed microfluidic synthesis strategy enables on-demand manufacturing of a wide variety of microparticle morphologies, including hollow shell, yolk-shell, macroporous, and dense microspheres, as well as surface areas as high as 360 m²g^-1 with diameters ranging from 5 to 250 μm.

1 T. Zhao et al. Nano Energy, 2016, 26, 16–25.

2 Z. S. Campbell et al. Chem. Mater., 2018, 30, 8948–8958.

3 Z. S. Campbell et al. RSC Adv., 2020, 10, 8340–8347.