Effects of multiple scattering on angle-independent structural color in disordered colloidal materials

Area of Science:

• Colloidal science
• Optics
• Materials science

Background:

• Disordered colloidal sphere packings exhibit angle-independent structural color.
• Single-scattering models accurately predict peak positions, indicating short-range correlations are key.
• However, these models fail to reproduce spectral broadening and enhanced low-wavelength reflectance.

Purpose of the Study:

• To investigate the discrepancies between single-scattering models and experimental observations of structural color in colloidal sphere packings.
• To understand the physical mechanisms responsible for spectral peak broadening and increased low-wavelength reflectance.
• To explore how these scattering phenomena affect color saturation and potential applications.

Main Methods:

• Combined experimental measurements of reflectance spectra with theoretical modeling.
• Analyzed light scattering pathways, including total internal reflection and multiple scattering events.
• Investigated the wavelength dependence of individual particle scattering cross sections.

Main Results:

• Multiple scattering, particularly involving total internal reflection, significantly broadens the main reflectance peak.
• High reflectance at low wavelengths is attributed to increased scattering cross sections and multiple scattering.
• These effects collectively reduce the saturation of the observed structural color.

Conclusions:

• Single-scattering models are insufficient for quantitatively predicting the full reflectance spectrum and color saturation.
• Multiple scattering phenomena are crucial for understanding the observed spectral features.
• Despite limitations, single-scattering models can guide the design of colloidal materials to enhance color saturation by minimizing multiple scattering.