Novel fabrication of NIR-vis upconversion NaYF4:Ln (Ln = Yb, Er, Tm) crystal layers by a flux coating method

Abstract

High quality upconverting NaYF 4 :Ln (Ln ¼ Yb, Er, Tm) crystal layers were successfully fabricated directly onto glass substrates at a relatively low temperature of 350 C by a novel two-step flux coating method. First, mixed pastes of solute (NaF and YF 3 ) and dopants (LnF 3 ) were coated on glass substrates by simple bar-coating, and then flux pastes (NaNO 3 or NaNO 3 -NaF) were coated onto the dopant-containing solute layer. After the two-step coating, raw material-coated substrates were heated at 350 or 400 C in an electric furnace. To remove the remaining flux, the crystal layers were washed with warm water. Finally, high quality, nanotextured NaYF 4 :Ln crystal layers with good adhesion were directly grown onto the glass substrates. These crystal layers consisted of densely packed idiomorphic NaYF 4 :Ln crystals. In particular, individual NaYF 4 :Ln crystals were typically shaped as hexagonal prisms. The NaYF 4 :Ln crystal phases depended strongly on the heating conditions, i.e., temperature and time. The NaNO 3 and NaNO 3 -NaF fluxes were effective for the growth of highquality idiomorphic NaYF 4 :Ln crystals. Additionally, the upconversion fluorescence properties of NaYF 4 :Ln crystal layers were controlled by changing dopant types and ratios. The NaYF 4 :10%Yb,1% Er, NaYF 4 :50%Yb,1%Er, NaYF 4 :20%Yb,1%Tm and NaYbF 4 :1%Er crystal layers emitted green, orange, blue and red fluorescences, respectively, under 980 nm laser irradiation.

Flux growth of honeycomb-like β-NaYF4:Yb3+, Er3+/Tm3+ crystals with multicolor upconversion luminescence

“…3. These emission spectra are similar to those for Yb 3 þ ,Er 3 þ or Yb 3 þ ,Tm 3 þ co-doped hexagonal NaYF 4 nanocrystals, microtubes microrods and microprism reported previously [15][16][17][20][21][22]. In Fig.…”

“…In Fig. 3(1) for the b-NaYF 4 :20%Yb 3 þ , 2%Er 3 þ sample, the dominated red emission centered at 653 nm originates from the 4 F 9/2 -4 I 15/2 transition, and the green emission at 520 nm and 539 nm can be assigned to 2 H 11/2 -4 I 15/2 , and 4 S 3/2 -4 I 15/2 transitions [15,16,20]. In Fig.…”

“…Up to now, several techniques have been employed for synthesis of b-NaYF 4 , such as solid reaction [8], coprecipitation [12], hydrothermal [13,14], flux cooling methods [15][16][17]. Comparing with other methods, the flux cooling method is a facile mass production method with inexpensive equipment, low environment loads and high crystalline.…”

Shape‐Controlled Synthesis of Monodispersed Ultrasmall CaGd3F11 Nanocrystals for Potential Dual‐Modal Probes

“…Figure 5 shows the emission spectra of the obtained nanocrystals doped with 10 % Yb/1 % Er and 15 % Yb/5 % Er under 980 nm excitation at room temperature. All four spectra show the characteristic emitting peaks of the Er 3+ ions centered at 405, 520, 540, and 655 nm; these values are assigned to the transitions of 2 H 9/2 → 4 I 15/2 , 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 , and 4 F 9/2 → 4 I 15/2 , respectively 19. Furthermore, the green emission peaks (520 and 540 nm) were significantly higher than the red emission peaks (650 nm) on the spectra.…”

Lanthanide Doped Near Infrared Active Upconversion Nanophosphors: Fundamental Concepts, Synthesis Strategies, and Technological Applications

“…In addition to the applications mentioned in above sections, the UCNPs have been extended to anticounterfeiting, fingerprint detection, lighting, transparent displays, solar cells, photoisomerization, and photoswitching applications as well. Various UCNP systems and their applications are tabulated in Table 4 .…”