Light-emitting biosilica by in vivo functionalization of phaeodactylum tricornutum diatom microalgae with organometallic complexes

In vivo incorporation of a series of organometallic photoluminescent complexes in Phaeodactylum tricornutum diatom shells (frustules) is investigated as a biotechnological route to luminescent biosilica nanostructures. [Ir(ppy)2bpy]+[PF6]-, [(2,2?-bipyridine)bis(2- phenylpyridinato)iridium(III) hexafluorophosphate], [Ru(bpy)3]2+ 2[PF6]-, [tris(2,2?-bipyridine)ruthenium(II) hexafluorophosphate], AlQ3 (tris-(8-hydroxyquinoline)aluminum), and ZnQ2 (bis-8-hydroxyquinoline-zinc) are used as model complexes to explore the potentiality and generality of the investigated process. The luminescent complexes are added to the diatom culture, and the resulting luminescent silica nanostructures are isolated by an acid-oxidative treatment that removes the organic cell matter without altering both frustule morphology and photoluminescence of incorporated emitters. Results show that, except for ZnQ2, the protocol successfully leads to the incorporation of complexes into the biosilica. The spontaneous self-adhering ability of both bare and doped Phaeodactylum tricornutum cells on conductive indium tin oxide (ITO)-coated glass slides is observed, which can be exploited to generate dielectric biofilms of living microorganisms with luminescent silica shells. In general, this protocol can be envisaged as a profitable route to new functional nanostructured materials for photonics, sensing, or biomedicine via in vivo chemical modification of diatom frustules with organometallic emitters.