Preparation and optimization of biomimetic materials simulating solar spectrum reflection characteristics of natural leaves

Solar spectrum reflection characteristics of natural leaves are caused by the absorption and scattering processes of incident radiation in the leaves. To realize hyperspectral camouflage in the background of vegetation, two types of biomimetic materials are prepared. One type utilizes Cr2O3 particles to simultaneously simulate the absorption characteristics in the visible light band and the scattering characteristics in the solar spectrum band and is named as COG-BM. The other type contains chlorophyll and TiO2 particles to simulate the absorption and scattering characteristics in the above two bands, respectively, and is named as CH/TD-BM. The measured results show that both can simulate the solar spectrum reflection characteristics of the leaves approximately. In order to optimize the bionic performance, the reflectance predicting model was constructed with Lorenz–Mie scattering and four-flux theories. The simulation results show that with the increase in particle volume fraction, the reflectance of COG-BM in the visible light band is maintained at almost the same level as that of the leaves because of the simultaneous increase in absorption and scattering coefficients. Nevertheless, the reflectance of CH/TD-BM increases significantly, because the absorption coefficient of CH/TD-BM is constant with the increase in the particle volume fraction, and the scattering coefficient enhances remarkably. More interestingly, with the increase in particle size, the near-infrared plateau of COG-BM and CH/TD-BM is closer to horizontal, exhibiting greater similarity to the natural leaves. Moreover, the water absorption characteristics at 1450 and 1940 nm become more significant with the increase in water content.