Dual Laser Study of Non‐Degenerate Two Wavelength Upconversion Demonstrated in Sensitizer‐Free NaYF₄:Pr Nanoparticles

Abstract

Understanding the upconversion pathways of a rare‐earth dopant is crucial to furthering the use of that material, either toward applications in imaging or elsewhere. This work outlines a new analysis approach that consists of using two synchronized widely‐tunable laser sources to explore the properties of upconverting materials. By examining sensitizer‐free rare‐earth nanoparticles based on a matrix of hexagonal sodium yttrium tetrafluoride (β‐NaYF4) doped with praseodymium but no ytterbium sensitizer, a “non‐degenerate” two‐color upconversion fluorescence at a combined excitation of 1020–850 nm is shown. This insight demonstrates the ability of this technique to locate and interrogate novel upconversion pathways. The dopant level of the nanoparticles could be modified without altering other factors, such as the particle's shape or size, that would also change optical properties and this allows investigation of the dopant‐level dependency of the optical properties. The approach also allows exploration of the time delay domain between the arrival times of the two non‐degenerate excitation pulses, which allows modulation of the brightness from the visible light emissions. This work opens up the parameter space for the systematic synthesis and characterization of new materials with non‐degenerate upconversion emission.

A multi-color persistent luminescent phosphor β-NaYF4:RE3+ (RE = Sm, Tb, Dy, Pr) for dynamic anti-counterfeiting

“…44 Specifically, the strongest blue emission at 492 nm is attributed to the 3 P 0 → 3 H 4 transition and the red emission at 614 nm is ascribed to the 3 P 0 → 3 H 6 transition. 45,46 As exhibited in the CIE diagram and digital photos in Fig. 5b, multi-color emissions can be easily realized by X-rays irradiating the β-NaYF 4 :RE 3+ samples.…”

Effect of oxygen pressure on stoichiometric transfer in laser ablation of Pr3+ doped Gd2O3–Ga2O3 binary system

“…28 Pr 3+ doped materials were produced a nondegenerate two wavelength upconversion excitation pathway of 1020 and 850 nm leading to visible light emission. 29 In our previous work focused on the plasma characterization during the GGG crystal ablation, we found a strong dependence of the plasma properties on the partial oxygen pressure. Depending on the oxygen pressure, the ratio of emission from [Gd] and [Ga] in plasma varied from 3:5 to 1:1 and GGP crystal could be fabricated on the perovskite substrate.…”

Enhanced two-step two-frequency upconversion luminescence in a core/shell/shell nanostructure

“…Many excellent works on TSTF UCNPs have been reported [37][38][39][40][41] . For example, Chen et al 37 demonstrated that enhanced UCL intensity in NaYF 4 :1%Er nanoparticles were realized by 790 & 1520 nm excitation.…”

“…[37][38][39][40][41] For example, Chen et al37 demonstrated that enhanced UCL intensity in NaYF 4 :1%Er nanoparticles was achieved by 790 & 1520 nm excitation. Li et al 38 demonstrated that enhanced red emission in Gd 2 MoO 6 :Er/Yb nanoparticles co-doped WO 6 6À and La 3+ was achieved by 980 & 1550 nm excitation.…”