Study On Intense Fluorescent Metal Oxide Nanoparticles And Their Polymer Hybrid Films

The coordinated metal oxide(europium oxide,terbium oxide,zinc oxide and alumina) ethanol colloids,coordinated metal oxide/polymer organic colloids and their hybrid films were prepared by folused pulsed laser ablation at the interface of metal oxide target submerged in flowing liquid containing ligands,where the polymers used in hybrid films are PMMA(polymethyl methacrylate)and PS(polystyrene),respectively.High resolution transmission electron microscopy(HRTEM),transmission electron microscopy(TEM), UV-Vis spectrum,Fourier transform infrared spectroscopy(FT-IR),fluorescence spectrum,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),combined thermalgravity-Fourier transform infrared spectroscopy(TG-FTIR)were used to study the influence of experimental conditions on emission intensity of the coordinated metal oxide organic colloids,the structure and properties of the coordinated metal oxide nanoparticles and fluorescence properties of the coordinated metal oxide/polymer hybrid films.It is found that the coordinated europium oxide ethanol colloids and its polymer hybrid films with surface Eu³⁺ions of the Eu₂O₃ nanoparticles coordinated by TTA(trifluorothenoylacetone) and phen(1,10-phenanthroline)can emit Eu³⁺characteristic red fluorescence under ultraviolet radiations;the coordinated terbium oxide ethanol colloids with surface metal ions of the Tb₂O₃ nanoparticles coordinated by acac(acetylacetone)and 2,2'-bipy (2,2'-bipyridyl)can emit Tb³⁺characteristic green fluorescence under ultraviolet radiations,and the coordinated terbium oxide/polymer hybrid films have an intense wide emission band at near ultraviolet region.The coordinated ZnO and Al₂O₃ ethanol colloids with surface metal ions of metal oxide nanoparticles coordinated by 8-hydroxyquinoline can emit intense green fluorescence under UV radiations,and their emission peaks locate at 555 and 513 nm,respectively.The emission peaks of the coordinated ZnO and Al₂O₃/polymer hybrid films locate at 508-520 nm.The experiments show ligands in the flowing liquids can coordinate with the surface metal ions of the metal oxide nanoparticles producted by pulsed laser ablation and form coordinated metal oxide nanoparticles with the core of metal oxide crystalline and outlayer of ligands coordinated with surface metal ions of the nanoparticles,which reduces the reactive activity of the nanoparticles and aggregrated ability.The average diameter of the embryonic metal oxide nanoparticles is from several nano meters to 20 nm.The coordinated metal oxide nanoparticles can self-fabricate into bigger particles with regular shape,accompanying with change of emission intensity.Because the polymer molecular can enwrap the coordinated metal oxide nanoparticles and keep them from outside atmosphere,the coordinated metal oxide/polymer colloids and their hybrid films have very stable chemical property;their emission intensity will not change even though the hybrid films have been deposited at moist atmosphere for several monthes.Because of strong interaction between metal oxide nanoparticles and polymer,the thermal stability of the coordinated metal oxide/poymer hybrid films is higher than that of relative pure polymers.The fluorescence mechanism of the coordinated europium oxide and terbium oxide is ligands absorb ultraviolet light, produce emission with good efficiency via intramolecular energy transferr from ligands to Eu³⁺or Tb³⁺ions and then Eu³⁺or Tb³⁺ions emit characteristic fluorescence.As polymer can also transfer absorbed energy to rare earth ions,the coordinated metal oxide/polymer have much high fluorescence intensity.The mechanism of the coordinated ZnO and Al₂O₃ colloids and their hybrid films is 8-hydroxyquinoline disturbed by centered Zn²⁺or Al³⁺ ions emits photons.