Page 142 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 7
Spectral decomposition of Eu3d5/2 suggests the existence of Eu2O3 nanoparticles and Eu2+ component, reflected by the significant peak at 1131.4 eV and the shake down satellite peak at 1125.2 eV.18,19 The deconvolution of O1s bands further confirms the above results. The two prominent peaks at 529.1 eV and 531.7 eV are typical O-Y bindings that widely existed in Y2O3 nanoparticles,18 while the subpeak at 530.7 eV is due to O-Eu binding.15 Moreover, the small peak at 533.2 eV originates from impurities such as O-C compounds or O-H species.17 Therefore, it is revealed that products mainly consist of Y2O3:Eu3+, although minor impurities were formed on their surface, in agreement with the EDX and FTIR results.
The spectral downshift behavior of both the solid Y2O3/Y2O3:5%Eu3+ sample and their aqueous solution is examined under the UV radiation (254nm). Strong red-orange fluorescent emissions are clearly visible from the Y2O3:Eu3+ sample when excited by the UV source, in contrast to the non-emissive Y2O3 particles (Figure 7.6). The result reveals the downshifting nature of the obtained Y2O3:5%Eu3+ nanophosphors. This property will allow the Y2O3:Eu3+ nanocomposites to be used in many practical applications, such as solid/liquid illumination, security-printing area, bio-imaging and other related areas.
Figure 7.6 Typical photographs of the synthesized Y2O3 and Y2O3:5%Eu samples (a) in the solid form and (b) the aqueous solution (b) under room light and UV irradiation (254 nm)
Afterwards, the influence of heat treatment and dopant concentration on the photoluminescence properties are investigated. Figure 7.7(a) shows the XRD patterns of Y2O3:Eu3+ nanoparticles with different Eu3+ doping concentrations (1-9 mol%). All the diffractions peaks are well indexed to the cubic Y2O3 (JCPDS card #41-1105), regardless of the Eu3+ concentration, indicating Eu3+ cations have been effectively doped into the Y2O3 lattice.13 Moreover, the influence of the calcination temperature on Y2O3:5%Eu3+ is investigated. All peaks are characteristic of the cubic crystalline structure, inferring the crystal structure has not been affected (Figure 7.7(b)). An apparent narrowing trend of the
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