Wavelength-commensurate anatase TiO\_2 particles for ro-bust and functional Mie resonances across the visible and near infrared

TL;DR

This paper presents a simple synthesis method for anatase TiO₂ particles with controlled size and monodispersity, enabling robust Mie resonances across visible and near-infrared spectra for applications in sensing and photonics.

Contribution

It introduces a UV-assisted thermal hydrolysis route to produce anatase TiO₂ particles with desired optical properties, advancing the synthesis and application of earth-abundant Mie resonators.

Findings

Particles exhibit intense, tunable Mie resonances across visible and near-infrared

Method produces monodisperse anatase TiO₂ particles with size standard deviation ≤ 5%

Enables label-free detection of biomolecules with broadband optical response

Abstract

Earth-abundant materials exhibiting Mie resonances across the visible and near-infrared offer opportunities for efficient and sustainable sensing, thermal regulation, and sunlight harvesting. For anatase TiO$_2$, a broadband optical and abundant material, Mie calculations indicate that robust resonances require size tunability and monodispersity (standard deviation, $\lesssim$ 5\%) over an extended range (0.5-2 $\mu$m) not yet experimentally covered, while maintaining a refractive index above 2 to ensure optical contrast, for example with biomolecules. Here, we demonstrate that a simple UV-assisted thermal hydrolysis route yields anatase particles that meet all these criteria and remain aqueous-processable. Consequently, the materials display intense and modulable Mie resonances across the visible/near-infrared regions (including biological windows), outperforming previous results that were limited by size. Strong optical resonances combined with ambient-temperature processability enable robust, broadband, label-free detection of transparent biomolecules. Our insights advance precise synthesis and Mie-based photonics of an earth-abundant material, and indicate the potential for cost-effective and rapid-on-demand integration via printing technologies, further enhanced by anatase's biocompatibility and photochemical properties.