Visible-near-infrared reflectance spectra of Cr2O3-based biomimetic leaves: A combined spectroscopic ellipsometry and first-principles study

The quest for biomimetic materials that emulate the solar spectral response of green plants has garnered substantial attention. Herein, we combined density-functional theory with on-site Coulomb corrections and spectroscopic ellipsometry to obtain the complex dielectric functions of chromium oxide (Cr 2 O 3 ) pigment and polyurethane (PU) binder, respectively. Based on the Lorenz-Mie scattering theory and two-flux method considering anisotropic scattering, we systematically studied the regulatory mechanism of particle structural parameters on the reflectance spectrum of the biomimetic coating. The results show that optimizing the structural parameters of Cr 2 O 3 particles reproduces the canonical vegetation features in the visible-near-infrared region. Coating reflectance decreases monotonically with both increasing particle volume fraction and larger mean radius. Additionally, the slope of red edge can be independently tuned by the particle size distribution, i.e. a larger proportion of small particles steepens the red-edge slope. This study provides a theoretical basis and data support for further optimizing the similarity between biomimetic coatings and natural vegetation in terms of their hyperspectral images in the visible-near infrared spectral range.