Biological Kerker effect boosts light collection efficiency in plants

TL;DR

This study reveals how alpine plants utilize the Kerker effect through CaCO3 nanoparticles to enhance light collection efficiency, combining experimental and numerical analysis of natural and synthetic particles.

Contribution

It demonstrates that plants can naturally engineer light scattering via multipole interference, revealing a bioinspired mechanism for efficient light collection.

Findings

Directional light scattering in vaterite nanospherulites

Generalized Kerker condition observed in natural and synthetic particles

Enhanced light collection efficiency in alpine plant leaves

Abstract

Being the polymorphs of calcium carbonate (CaCO3), vaterite and calcite have attracted a great deal of attention as promising biomaterials for drug delivery and tissue engineering applications. Furthermore, they are important biogenic minerals, enabling living organisms to reach specific functions. In nature, vaterite and calcite monocrystals typically form self-assembled polycrystal micro- and nanoparticles, also referred to as spherulites. Here, we demonstrate that alpine plants belonging to the Saxifraga genus can tailor light scattering channels and utilize multipole interference effect to improve light collection efficiency via producing CaCO3 polycrystal nanoparticles on the margins of their leaves. To provide a clear physical background behind this concept, we study optical properties of artificially synthesized vaterite nanospherulites and reveal the phenomenon of directional light scattering. Darkfield spectroscopy measurements are supported by a comprehensive numerical analysis, accounting for the complex microstructure of particles. We demonstrate the appearance of generalized Kerker condition, where several higher order multipoles interfere constructively in the forward direction, governing the interaction phenomenon. As a result, highly directive forward light scattering from vaterite nanospherulites is observed in the entire visible range. Furthermore, ex vivo studies of microstructure and optical properties of leaves for the alpine plants Saxifraga 'Southside Seedling' and Saxifraga Paniculata Ria are performed and underlined the importance of Kerker effect for these living organisms. Our results pave the way for a bioinspired strategy of efficient light collection by selfassembled polycrystal CaCO3 nanoparticles via tailoring light propagation directly to the photosynthetic tissue with minimal losses to undesired scattering channels.