Diatom cells are a promising system for green synthesis of nanomaterials like metallic nanoparticles (NPs), nanostructured polymers and other nanomaterials. The production of NPs is achieved today by using methods like attrition or pyrolysis. The cost and the toxic substances often used in these common methods of NPs synthesis limit their applications. Therefore, NPs biosynthesis by diatom cultures, which can be done at ambient CO2 concentrations, temperature and pressure, offers a sustainable alternative solution.
In this work, we examined the formation of silver NPs (AgNPs) by the diatom Phaeodactylum tricornutum cultivated at 25°C for a period of 8 days. Using this approach, diatom cultures were either grown throughout the duration of the experiment in an artificial seawater (ASW)-f/2 medium enriched with 1 ppm Ag+ or grown in an ASW-f/2 medium where similar silver ion concentrations were added on experimental day 4. We found that 1 ppm Ag+ reduces the P. tricornutum growth by up to 50% as compared with the control. Moreover, scanning electron microscopy (SEM) in combination with Energy-Dispersive X-ray (EDX) showed the presence of AgNPs nanoparticles with different sizes and chemical composition associated with the diatom frustules and extracellular polymeric substances.