Near-Infrared-to-Blue Upconversion in Colloidal BaYF₅:Tm³⁺, Yb³⁺ Nanocrystals

Abstract

Tetragonal barium yttrium fluoride (BaYF 5 ) nanocrystals doped with 0.5 mol % Tm 3+ and 15 mol % Yb 3+ (BaYF 5 :Tm 3+ , Yb 3+ ) were synthesized using the thermal decomposition method yielding rectangularshaped nanocrystals (15 nm × 5 nm) that can (up)convert near-infrared light to higher energies such as blue, via a process known as upconversion. The upconversion spectrum of the BaYF 5 :Tm 3+ , Yb 3+ nanocrystals, following excitation with 980 nm, revealed that the upconverted blue emission from the 1 G 4 f 3 H 6 transition was more intense than the infrared 3 H 4 f 3 H 6 emission at high excitation densities (90 W/cm 2 ) contrary to what is normally observed for Tm 3+ /Yb 3+ codoped nanomaterials. On the other hand, the infrared emission dominates at lower excitation densities (15 W/cm 2 ) demonstrating a lack of excited Yb 3+ ions to carry on the upconversion beyond the 3 H 4 excited state to the 1 G 4 excited state. A saturation of the upconversion process was observed in the power dependence studies at excitation densities above 57 W/cm 2 , causing a deviation in the expected number of photons required for the upconversion process. The upconversion properties of BaYF 5 :Tm 3+ , Yb 3+ nanocrystals are elucidated and discussed.

Synthesis process and luminescence properties of Tm3+ in AWO4 (A=Ca, Sr, Ba) blue phosphors

“…A procedure for the sample synthesis is typically described as follows: 0. 25 is polytungstate species). A well-controlled amount of NaOH solution was then added with magnetic stirring to pH 9 to form a little white precipitate (white precipitate is monotungstate species) [30,31].…”

“…At present, AWO 4 were reported to be efficient luminescent hosts for rare earth [20][21][22][23]. Tm 3+ ion is widely used as activator of blue emission corresponding to its 1 D 2 → 3 F 4 and 1 G 4 → 3 H 6 transitions [24][25][26][27][28][29]. Their luminescence spectra consist of several very narrow bands, which make them effective luminescent centers.…”

“…Their luminescence spectra consist of several very narrow bands, which make them effective luminescent centers. These investigations of Tm 3+ -doped materials mainly focused on host matrix, such as fluorides [25], phosphates [27], and vanandates [28]. However, to the best of our knowledge, there is no study that has been devoted to the luminescence properties of AWO 4 :Tm phosphors.…”

Lanthanide doped upconverting colloidal CaF2 nanoparticles prepared by a single-step hydrothermal method: toward efficient materials with near infrared-to-near infrared upconversion emission

“…This is a well known behavior commonly found for realistic upconversion systems under large pump absorption. 23 A saturation behavior has also been found for other upconverting fluoride 4 hosts. The knowledge of the power density value for which saturation begins is of valuable importance for practical applications.…”

Color-tunable upconversion luminescence of Yb3+, Er3+, and Tm3+ tri-doped ferroelectric BaTiO3 materials

“…Owing to their abundant ladder-like energy levels, trivalent lanthanide ions, such as Er 3þ , Tm 3þ , Eu 3þ , and Pr 3þ , have been extensively studied as activator ions for UC processes. 5 Up to now, several trivalent lanthanide-doped UC materials have demonstrated that the tuning of UC multicolor can cover the whole visible light region by adjusting relative intensity of three primary colors red-green-blue (RGB). 6 In particular, by precise control of the combination and concentration of Ln 3þ ions, one may obtain efficient and singlephased white-light emitting phosphors.…”