Preparation and Characterization of Upconversion Luminescent NaYF4:Yb3+, Er3+ (Tm3+)/PMMA Bulk Transparent Nanocomposites Through In Situ Photopolymerization

The in situ photopolymerization method was applied to synthesize bulk nanocomposites consisting of hydrophobic NaYF 4:Yb 3+, Er 3+ (Tm 3+ ) nanoparticles as the filler and poly(methyl methacrylate) (PMMA) as the host material. The oleic acid stabilized NaYF 4:Yb 3+, Er 3+ (Tm 3+ ) nanoparticles and NaYF 4:Yb 3+, Er 3+ (Tm 3+ )/PMMA nanocomposites have been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), the thermogravimetric analysis (TGA), flexural tests, UV/vis transmission spectra, upconversion photoluminescence spectra, and luminescence decays. The well-crystallized NaYF 4:Yb 3+, Er 3+ (Tm 3+ ) nanoparticles are spherical with a mean diameter of 40 nm. The obtained solid NaYF 4:Yb 3+, Er 3+ (Tm 3+ )/PMMA nanocomposites have similar mechanical properties to that of pure polymer. NaYF 4:Yb 3+, Er 3+ /PMMA and NaYF 4:Yb 3+, Tm 3+ /PMMA nanocomposites are transparent in the visible spectral region and exhibit strong green and blue upconversion photoluminescence upon 980 nm laser excitation due to the integration of luminescent NaYF 4:Yb 3+, Er 3+ and NaYF 4:Yb 3+, Tm 3+ nanoparticles, respectively.