Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Nanomaterials Tuesday Sessions
       Session NM-TuP

Paper NM-TuP21
Pulsed Laser Assisted Synthesis of NaLa(MoO4)2:Ho3+/Tm3+/Yb3+ Nanocrystals and their White Upconversion Luminescence

Tuesday, December 9, 2014, 4:00 pm, Room Mauka

Session: Nanomaterials Poster Session
Presenter: Jeong Ho Ryu, Korea National University of Transportation, Korea
Authors: J.H. Ryu, Korea National University of Transportation, Korea
J.-I. Lee, Korea National University of Transportation, Korea
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In recent years, lanthanide ion doped upconversion (UC) luminescence from near infra-red radiation to visible or UV light has received many attention for their various applications in phosphors, solar cell, flat-panel displays, scintillators, solid state lasers and fluorescent bio-medicals. In the fields of industries, it is required that UC luminescent materials should be engineered to emit wide ranges of white colors. Also, high chemical, physical and mechanical stabilities should be achieved through engineering UC materials. Although multi-color UC luminescence with high efficiency was reported using lanthanide doped fluorides emitting bright blue emission of Tm3+ and green or red of Er3+ under laser excitation (980 nm), fluorides can decompose easily with moisture in air which makes the application difficult in the fields of industries. Conventionally, solid state reaction, precipitation, hydrothermal and sol-gel methods were used for synthesis of nanocrystalline NaLa(MoO4)2 particles However, those methods need long processing time and steps for fabrication. Also, chemical additives in procedure may be incorporated to NaLa(MoO4)2 particles as impurities, which results in bad influence to human body clinically. One novel technique for fabrication of NaLa(MoO4)2 nanocrystals is pulsed laser ablation (PLA) in liquid medium. PLA of solid target in liquid has been a promising technique for producing nanocrystals for analytical and bioanalytical applications as well as the rapid synthesis of complex materials because the experimental procedure is simple and above all, chemical additive is unnecessary. However, to date, there is little report on the preparation of upconverting NaLa(MoO4)2 nanocrystals by laser ablation in liquid medium. In this study, we report a novel synthetic approach to produce Ho3+, Tm3+, Yb3+ tri-doped NaLa(MoO4)2 nanocrystals using PLA in liquid medium without any surfactant. The fabricated NaLa(MoO4)2:Ho3+/Tm3+/Yb3+ nanocrystals were characterized in terms of their crystallinity, microstructure and white upconverting property. Moreover, the laser ablation process was discussed by a thermally induced explosive ejection mechanism.