Abstract
The purpose of this study was to describe the synthesis, characterization, and functionalization of b-NaYF4:30%Yb/0.5%Tm upconverting nanocrystals for use as nanofillers in a dental adhesive and microscopically evaluate the interface between the particles and a commercial adhesive. The upconverting nanoparticles were synthesized and purified by thermal decomposition, and their chemical composition determined by energy dispersive X-Ray spectroscopy. The crystalline structure was characterized using X-Ray diffraction and morphology and size were observed with scanning and transmission electron microscopy. Upconverting emission was evaluated by spectrophotometry irradiating the particles with a 975 nm diode laser. Particles were functionalized with polyacrylic acid and the success was confirmed by measurement of Zeta Potential and transmission electron microscopy. The results of X-ray diffraction found a pure hexagonal phase crystalline pattern. Scanning electron microscopy showed uniform dispersion of hexagonal-shaped particles of approximately 150 nm. Upconversion emission was observed in 344 nm, 361 nm, 450 nm, 474nm, 646 nm, 803 nm. Functionalization success was confirmed by formation of a stable aqueous colloid with a Zeta potential of -29.5mV and the absence of voids in the particle-adhesive interface on the transmission electron microscopy images. The reported synthesis and functionalization process produced upconverting nanoparticles emitting photons within the blue spectral region (450 nm and 474 nm).
Highlights
Fluorescent emissions usually follow the Stoke shift principle, where the excitation energy has a higher electron potential than the emitted energy.[1]
The upconverting nanoparticles were synthesized and purified by thermal decomposition, and their chemical composition determined by energy dispersive X-Ray spectroscopy
Particles were functionalized with polyacrylic acid and the success was confirmed by measurement of Zeta Potential and transmission electron microscopy
Summary
Fluorescent emissions usually follow the Stoke shift principle, where the excitation energy has a higher electron potential (occurs at shorter wavelengths) than the emitted energy (occurring at longer wavelengths).[1]. The UC effect observed for sodium yttrium fluoride (NaYF4) crystals doped with Yb+3 and Tm+3 can be described as a three- and four-photon energy transfer upconversion process[1] resulting in visible light emission between 450 and 500 nm when exposed to 975 nm infrared (IR) excitation,[3,6,7] that has high penetration through materials.[2]
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