Ultrasonic spray pyrolysis for the synthesis of fluorophore nanoparticles: fluorescent, phosphorescent, and luminescent systems

Ultrasonic spray pyrolysis (USP) is a continuous, atmospheric-pressure aerosol process that converts liquid precursor solutions into solid nanoparticles through ultrasonic atomisation followed by thermal treatment in a tube furnace. The method offers compositional flexibility, single-step composite formation, scalability through parallelisation, and a lower capital cost than flame spray pyrolysis and batch solution routes. USP has been used to produce noble-metal nanoparticles, metal-oxide nanoparticles, semiconductor quantum dots, porous carbon microspheres, doped wide-bandgap semiconductor oxide thin films, and single-step phosphor–matrix composites such as YVO 4 :Eu 3+ in γ -Al 2 O 3 . This review covers nanoscale fluorophores, including inorganic semiconductor/metal-halide nanocrystals, carbon-based fluorophores, lanthanide-doped inorganic phosphors, and emerging 0D quantum dots derived from layered parent materials, and assesses their synthetic feasibility for USP. Three target material types emerge as direct extensions of demonstrated capability (rare-earth-doped oxide nanophosphors, persistent luminescent nanoparticles, room-temperature phosphorescent carbon-dot–matrix composites), five as plausible extensions requiring moderate adaptation (fluorescent carbon dots, graphitic carbon nitride quantum dots, doped semiconductor oxide nanoparticles, I–III–VI 2 ternary chalcogenide quantum dots, Mn 2+ doped II–VI nanocrystals), and several as not addressable by USP under current understanding. Persistent technical issues in controlling the size, residence time, and carbonisation degree of carbon-based materials are identified, along with proven solutions from the inorganic literature.