Inducing transparency in the films of highly scattering particles

TL;DR

This paper presents a method to reduce optical scattering in films made of rough colloidal particles by hybridizing them with smaller particles or quantum dots, enabling transparent coatings and optical applications.

Contribution

The study introduces a novel approach to suppress scattering in rough colloidal films using hybridization with smaller particles or quantum dots, enhancing their optical transparency.

Findings

Hybridization with smaller PS particles prevents aggregation.

Decreasing spatial refractive index variation reduces scattering.

Films can achieve transparency suitable for optical applications.

Abstract

Today colloids are employed in various products from creams and coatings to electronics. The ability to control their chemical, optical, or electronic features by controlling their size and shape explains why these materials are so widely employed. Nevertheless, altering some of these properties may also lead to some undesired side effects, one of which is an increase in optical scattering upon concentration. Here, we address this strong scattering issue in films made of colloids with high surface roughness. We focus on raspberry type polymeric particles made of a spherical polystyrene core decorated by small hemispherical domains of acrylate. Owing to their surface charge and model roughness, aqueous dispersions of these particles display an unusual stability against aggregation. Under certain angles, their solid films display a brilliant red color due to Bragg scattering but otherwise appear completely white on account of`strong scattering. To suppress the scattering and induce transparency, we prepared films by hybridizing them either with oppositely-charged PS-particles that fit the length-scale of the raspberry roughness or with quantum dots. We report that the smaller PS-particles prevent raspberry particle aggregation in solid films and suppress scattering by decreasing the spatial variation of the refractive index. We believe that the results presented here provide a simple strategy to suppress strong scattering of rough particles and allow for their utilization in optical coatings, cosmetics, or photonics.