Single-benzene-based fluorophores (SBFs) represent a highly versatile class of minimalistic light-emitting molecules. They exhibit tunable photophysical properties and are biocompatible when they are integrated with biological systems. Thanks to their minimal design and versatile light emission, they are attractive molecules used as fluorescent sensors and as bioimaging probes. Here, we report the design, single-step synthesis, purification, and characterization of three photoluminescent SBF derivatives together with the study of their interactions with model diatom microalgae Thalassiosira weissflogii. The different candidates (bearing (i) a hydrophobic tail chain, (ii) a triethoxysilyl group, and (iii) an amino acid residue) demonstrate distinct interactions with different cellular structures of living diatoms, exhibiting promising characteristics to develop selective bioimaging probes. Moreover, two SBF candidates were found to exert a positive effect on diatom photosynthetic efficiency with an enhancement in biomass production, potentially working as exogenous antennae. Future developments would include the incorporation of these easily accessible dyes in bioimaging, environmental biosensing, and bioengineering aimed at increasing photosynthetic efficiency.