Ultraviolet upconversion enhancement in triply doped NaYF4:Tm3+, Yb3+ particles: The role of Nd3+ or Gd3+ Co-doping

• Published in: Optical materials Vol. 58; pp. 67 - 75
• Main Authors: Pokhrel, Madhab, Valdes, Carolina, Mao, Yuanbing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2016
• Subjects: Doping; Gadolinium (Gd3+); NaYF4; Neodymium (Nd3+); Ultraviolet; Upconversion; Neodymium (Nd3+); Upconversion; Ultraviolet; NaYF4; Gadolinium (Gd3+); Doping
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2016.05.020

Upconversion (UC) particles are currently under intensive investigation, normally for their visible instead of ultraviolet (UV) light luminescence under near-infrared (NIR) irradiation. As a commonly studied host, NaYF4 in particular is known to have low phonon energy and high UC efficiency. Here, we present our work on enhancing UC luminescence in the UV region by adding a third dopant into a binary-doped NaYF4:Yb3+,Tm3+ host. More specifically, neodymium (Nd3+) or gadolinium (Gd3+) ions was co-doped into parent NaYF4:20mol%Yb3+,0.5mol%Tm3+ UC particles to enhance their UV UC luminescence. Experimental results demonstrated that these particles exhibited the highest degree of UV UC enhancements when co-doped with 0.05mol% Nd3+ or 2.0mol% Gd3+, expanding the potential of this type of materials into many possible applications by directly converting NIR irradiation into UV light. Fundamentally, the UV UC emission dependence of these triply doped NaYF4:Yb3+,Tm3+ particles with different Nd3+ and Gd3+ doping concentrations was investigated in terms of ground state absorption, excited state absorption and energy transfer UC mechanisms. Deep UV upconversion emissions centered at 311 nm from the NaYF4:20mol%Yb3+,0.5mol%Tm3+,ymol%Gd3+ sample (left) and 289 nm from the NaYF4:20mol%Yb3+,0.5mol%Tm3+,xmol%Nd3+ sample (right) under 980 nm excitation resulted from the energy transfer circulation within the Yb3+,Tm3+,Gd3+ and Yb3+,Tm3+,Nd3+ systems as illustrated at the center. [Display omitted] •Enhanced UV UC luminescence by adding a 3rd dopant into NaYF4:Yb3+,Tm3+ host.•Highest degree of UV UC enhancements exhibited with 0.05mol% Nd3+ or 2.0mol% Gd3+.•Demonstrated higher UV UC performance plus a better fundamental understanding.•Expanding potential applications by directly converting NIR light into UV light.