Diatom photonic crystals with augmented fluorescence emission by Purcell enhancement [Invited]

Emission control in photonic crystal structures has attracted enormous interest in the past two decades. Diatoms, the single-cell algae with their frustules inherently possessing periodic photonic crystal features, offer an alternative to artificially fabricated photonic crystals. In this study, we investigated augmented fluorescence emission due to the Purcell effect by incorporating fluorescent dye BP405 onto diatom Pinnularia sp. frustules. We numerically reconstructed a three-dimensional model of the frustule and simulated Purcell enhancement, which showed that fluorescence dye molecules adsorbed at various locations of the frustule can experience both enhanced fluorescence emission and color change. We experimentally observed enhanced fluorescence emission intensity as well as red shift of the fluorescence spectra, which agrees well with our numerical simulation. A deeper insight into the contributory factors was traced through a series of control experimental studies using BP405 on diatomaceous earth, with filter paper, and using R6G with fluorescence emission outside of the Purcell effect region, indicating the dominant role of photonic crystal structures in altering emission behavior. Our investigation confirms the Purcell effect from diatom photonic crystals to augmented fluorescence emission, which may open a new route toward synthesizing artificially engineered solid-state light-emitting materials.