High Refractive Index Crystalline Colloidal Arrays

University of Pittsburgh researchers have developed a new composite material and a process for synthesizing highly monodisperse zinc sulfide and polystyrene composite particles. These particles self-assemble into crystalline colloidal arrays (CCAs) that Bragg-diffract light in the visible and near-infrared (NIR) regions. With a high refractive index of about 2, these materials have potential applications in coatings, filters, and photonic crystal sensors and devices. This innovation could revolutionize the fields of materials science and optical device engineering.

Description

The invention involves the synthesis of highly monodisperse zinc sulfide (ZnS) particles coated with a highly charged polymer shell, enabling their self-assembly into CCAs. The process includes the direct precipitation of ZnS in ethylene glycol, where thioacetamide (TAA) reacts with water to produce reactive sulfur ions that form monodisperse particles. The particle size can be fine-tuned to diffract light in the visible region by adjusting the concentrations of nitric acid and water. These particles are further coated with a sulfonated polystyrene/divinylbenzene (PS/DVB) shell, enhancing their self-assembly into CCAs.

Applications

- Coatings and Paints
- Filters
- Hydrogel Sensors
- Cosmetics
- Photonic Devices

Advantages

This invention offers several advantages over currently available technology. The high refractive index (about 2) of the CCAs is not currently available in the literature, providing significantly higher diffraction efficiencies that enable the fabrication of ultrathin films for coatings and sensor applications. Additionally, ZnS is a non-toxic material, and the ability to fine-tune particle size for specific optical properties enhances its versatility. The robust synthesis process also allows for potential large-scale production.

Invention Readiness

The invention is at an advanced stage of development. Researchers have successfully synthesized monodisperse, high refractive index materials and coated them with a highly charged polymer shell. Experimental details include the synthesis of ZnS particles through the reaction of thioacetamide with water in ethylene glycol, producing monodisperse particles with sizes ranging from 18 nm to over 2 µm. The particles are then coated with a sulfonated PS/DVB shell, enabling their self-assembly into CCAs. The materials have been tested for their ability to form CCAs and demonstrate high diffraction efficiencies, with detailed characterization of particle size and optical properties.

IP Status

https://patents.google.com/patent/WO2008016606A2