Elastic Guanine-Based Single Crystals with Optical Waveguiding Properties: Toward Tailored Bioinspired Materials

Abstract

Flexible organic crystalline materials exhibiting both mechanical and optical properties have received significant attention due to their potential applications in flexible optical devices. Despite numerous examples reported in recent years, the use of organic salts or biologically related molecules for constructing such materials remains relatively scarce. We investigate the elastic bending ability of both guaninium chloride dihydrate single crystals and a novel material formed by this guanine salt doped with acridine orange in its acidic form. Even though the presence of the dye does not induce significant changes in the host crystalline structure, our findings reveal an unexpected increase in the maximum elastic strain from 1.06% in the guanine-based material to 1.50% when intracrystalline acridine orange is present. Emission lifetime and absorption coefficient in the doped crystals showed their optical quality and their ability to act as light guides, even under bent geometries with optical loss coefficients of 19.5 and 12.2 dB/mm, respectively (reference values of the straight crystals). Thus, these results shed light on the intriguing colored biomaterials observed in various organisms, such as geckos, spiders, and fishes, where structural coloration alone cannot account for the observed phenomena. Our results underscore the potential of guaninium chloride dihydrate as a versatile platform for developing bioinspired materials with tailored mechanical and optical properties through judicious choice of dopants.