Page 146 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 7
7% Eu3+ doping, excited at 248 nm. All spectra were normalized at the same level. The measuring conditions were referred to reported values in the literature.25
Moreover, we also expanded this method to prepare Ln3+ co-doped nanophosphors. Figure 7.9 shows typical emission spectra of yttria nanoparticles doped with various ratios of Eu3+ and Tb3+ (Eu:Tb=2:1, 1:1, 1:2). It is clearly shown that by varying the doping concentrations of Eu3+ and Tb3+ ions, the obtained nanophosphors exhibit characteristic emission peaks of Eu3+ (612 nm) and Tb3+ (543 nm, 550 nm) with tunable intensities. In this manner we can prepare Ln3+ co-doped nanophosphors of controllable photoluminescence properties.
Figure 7.9 Typical photoluminescence emission spectra of Eu3+ and Tb3+ doped/co-doped yttria nanophosphors. All spectra were normalized at the same level.
7.4 Conclusions
In summary, by proceeding the plasma-assisted process for the synthesis of yttrium oxide nanoparticles (Chapter 6), this chapter presents the demonstration of lanthanide (Ln=Eu, Tb, Dy, Tm) doped/co-doped nanophosphors synthesis through the plasma-electrochemical process. High quality crystalline nanophosphors of tunable photoluminescence properties can be obtained from merely an electrolyte solution of mixed Ln(NO3)3·6H2O salts. Instead of adding extra chemicals (solvents, stabilizers or surfactants) to suppress the vigorous and inhomogeneous hydrolyzing reactions driven by supersaturated alkali precipitants, this method exploits water as a “soft” OH- source to maintain a mild hydrolysing condition. By designing Eu3+ doped yttria phosphors as a proof-of-concept model study, it is revealed that heat-treatment during annealing step can improve the luminescent efficiency, while the Eu3+ concentration shows an initial positive but a final quenching effect. The developed plasma assisted technique overcomes formidable obstacles encountered in current methods for
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