Spectacular natural optical phenomena are produced by highly reflective assemblies of organic crystals. Here we show how the tapetum reflector in a shrimp eye is constructed from arrays of spherical isoxanthopterin nanoparticles and relate the particle properties to their optical function. The nanoparticles are composed of single-crystal isoxanthopterin nanoplates arranged in concentric lamellae around a hollow core. The spherulitic birefringence of the nanoparticles, which originates from the radial alignment of the plates, results in a significant enhancement of the back-scattering. This enables the organism to maximize the reflectivity of the ultrathin tapetum, which functions to increase the eye’s sensitivity and preserve visual acuity. The particle size, core/shell ratio and packing are also controlled to optimize the intensity and spectral properties of the tapetum back-scattering. This system offers inspiration for the design of photonic crystals constructed from spherically symmetric birefringent particles for use in ultrathin reflectors and as non-iridescent pigments.

壮观的自然光学现象是由有机晶体的高反射组件产生的。在这里，我们展示了虾眼中的绒毡层反射器是如何由球形异黄蝶呤纳米颗粒阵列构成的，并将颗粒特性与其光学功能联系起来。纳米粒子由单晶异黄蝶呤纳米片组成，这些纳米片以同心薄片排列在空心周围。源自板的径向排列的纳米颗粒的球晶双折射导致后向散射的显着增强。这使有机体能够最大限度地提高超薄绒毡层的反射率，从而提高眼睛的敏感性并保持视力。粒径，还控制核/壳比和填充以优化绒毡层背向散射的强度和光谱特性。该系统为设计由球对称双折射粒子构成的光子晶体提供了灵感，用于超薄反射器和非虹彩颜料。