Ion-exchanged zeolite for simulating the Vis-NIR spectra characteristics of natural leaves

The development of materials that simulate the visible and near-infrared (Vis-NIR) spectral characteristics of vegetation is crucial in the field of biomimetic camouflage. In this research, a novel spectral simulation material based on ion-exchanged zeolites has been synthesized, designed to simulate the spectral characteristics of green and yellow foliage. The structure and microscopic morphology of ion-exchanged zeolite was checked by XRD, FTIR, SEM techniques. Also, N₂ physisorption analyses and UV–Vis–NIR spectroscopy were use to analyzed the effect of ion exchange concentration on its water vapor adsorption capacity and spectral reflectance. The introduction of metal cations can mimic the absorption of different pigments in visible bands in plant leaves. Meanwhile, the analysis shows that exchange with chromium and iron cations resulted in a maximum increase in specific surface area to 604 and 582 m²/g, respectively, and consequently the increase in water adsorption capacity with approximately the same rate (13.1 %, 9.3 %), which further enhances the similarity of the near-infrared spectra. Subsequently, bionic coatings were prepared using ion-exchanged zeolites as pigments, and the spectral correlation coefficient of the Vis-NIR spectrum between bionic coatings and green and yellow leaves reached 0.95 and 0.96, which effectively solved the problem of accurately simulating the same color and spectrum as vegetation in the 400–2500 nm wavelength range.