Controlled Synthesis of Chlorophylls-Cu Doped Guanine Crystals with Long-Term Photothermal Stability and Its Application as Camouflage Materials

Biogenic guanine crystals widely distributed in organisms form ordered multi-level micro- and nano- structures and function as optical materials including reflectors, imaging mirrors, and photonic crystals for manipulating light. It is difficult to design green camouflage materials based on chlorophylls due to its poor photo and thermal stability under natural environment. Herein, a functional green camouflage biomimetic material based on chlorophyll derivative chlorophylls-Cu occluded into the crystal lattices of single crystalline anhydrous guanine microplates was designed, which exhibit high reflectivity and strong depolarization feature in the visible and near infrared range. The doping content of Chl–Cu in the guanine crystals can be varied and thus the color of the Chl–Cu doped guanine crystals can be well controlled from light green to dark green with the increase of the doping content of Chl–Cu in the guanine crystals. The color of the obtained Chl–Cu doped anhydrous guanine (Chl–Cu–AG) crystals is very similar to the color of green vegetation. And the green color of the Chl–Cu–AG crystals does not have obvious change after 30 days under photothermal treatment under 60 °C, indicating the long term photothermal stability of the camouflage biomimetic Chl–Cu–AG. This is the first time to report the photothermal stability of chlorophylls based green camouflage biomimetic materials, which have potential application as camouflage material.