The Use of Diatoms in the Synthesis of New 3D Micro-Nanostructured Composites (SiO 2 /CaCO 3 /C org /NdVO 4 NPs and SiO 2 /CaO/C org /NdVO 4 NPs) Exhibiting an Intense Anti-Stokes Photoluminescence.

New 3D micro-nanostructured composite materials have been synthesised. These materials comprise SiO 2 /CaCO 3 /C org /NdVO 4 NPs and SiO 2 /CaO/C org /NdVO 4 NPs, exhibiting strong upconversion luminescence. The synthesis was accomplished by metabolically doping diatom cells with neodymium and vanadium. Subsequently, the biomass of these doped diatoms was subjected to pyrolysis at 800 °C. The morphology, structure, and physicochemical properties of the doped diatom biomass as well as dried (SiO 2 /CaCO 3 /C org /NdVO 4 NPs) and pyrolysed (SiO 2 /CaO/C org /NdVO 4 NPs) samples were characterised using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), thermal analysis (TG), and fluorescence spectroscopy (FS). Studies have shown that the surface of diatom shells is covered with trigonal prismatic nanocrystallites (nanoparticles) of NdVO 4 with dimensions of 30-40 nm, forming the crystallite clusters in the form of single-layer irregular flakes. The synthesised composites produced intense anti-Stokes fluorescent emission in the visible region under xenon lamp excitation in the near-infrared (λ ex = 800 nm) at room temperature in an ambient atmosphere. Such materials could be attractive for applications in solar spectrum conversion, optical sensing, biosensors, or photocatalysts.