One-step synthesis and luminescence properties of tetragonal double tungstates nanocrystals

Abstract

A versatile one-step thermolysis protocol is demonstrated to produce a uniform dispersion of tetragonal double tungstates NaRE(WO4)2 (RE = rare earth) nanocrystals (NCs). Oriented attachment in the [001] direction occurred. Doping with luminescent RE(3+) ions resulted in highly luminescent NCs showing characteristic line emission of the dopant as well as a blue emission assigned to surface adsorbed organic species.

Facile hydrothermal crystallization of NaLn(WO4)2 (Ln=La-Lu, and Y), phase/morphology evolution, and photoluminescence

“…The decay curve can be fitted with the single exponential equation of I = A exp (-t/τ) + B in each case, where τ is the fluorescence lifetime, t the delay time, I the relative intensity, and A and B are constants [50]. The results of fitting yielded the lifetime of ~0.90 ms for both the as-synthesized and 600 °C calcined NaEu(WO 4 ) 2 under 395 nm excitation (Table 1), which is longer than the 0.49 and 0.54 ms reported for the 4.9 at% Eu 3+ doped NaGd(WO 4 ) 2 single crystal and 10 at% Eu 3+ doped NaLa(WO 4 ) 2 microcrystals (λ ex =394 nm, λ em =610 nm), respectively [5,51]. The similar lifetime values of ~0.75/0.79 ms were determined dipole transition (593 nm), as also observed by Wang et al [44][45][46].…”

“…and the unique luminescence properties inherited from the tungstate group [5]. A handful of methodologies have been successfully employed for Ln tungstate synthesis [6,7], but some important issues still need to be addressed.…”

“…The hydrothermal route generally shows substantial advantages over the aforementioned techniques in that it allows better control of the crystallite size, size distribution, particle morphology, and composition of the product, and is thus one of the most commonly used techniques for Ln tungstate preparation [6,11]. In addition, various chelates and surfactants (such as citric acid, ethylene diamine tetraacetic acid (EDTA), cetyltrimethyl ammonium bromide (CTAB), polyvinylpyrrolidone (PVP), ethylene glycol (EG), and oleic acid) have been tested to regulate the morphology of the hydrothermal product [2,5,6]. Through hydrothermal reaction at 200 °C for 24 hours in the presence of a small amount of EDTA-2Na, Liu et al [12] obtained a product that can be transformed into NaLa(WO 4 ) 2 microspindles by annealing at 600 °C for 2 hours.…”

Controllable synthesis and luminescent properties of rare earth doped Gd2(MoO4)3 nanoplates

“…Compared with traditional luminescent materials, such as semiconductor quntuam dots (QDs) [10] and organic fluorescent dyes, the RE ion-doped materials have narrow emission bands, lower photobleaching and longer fluorescence lifetimes. As is known to all, lanthanide compound NCs are composed of fluorides [11,12], oxides [13,14], molybdates [15], tungstates [16][17][18], vanadates [19,20], phosphates and so on [21]. As a group of inorganic new rare earth luminescent materials, due to its stability light spectrum, superior luminescent performance, good color change effect and the typical activation characteristics, molybdates have shown great application potential on luminescence materials.…”

Photonic Effects for Magnetic Dipole Transitions

“…A similar trend is observed for the core–shell NCs with longer luminescence lifetimes (7.0 ms vs 6.1 ms in core NCs in diethyl ether, Figure 2b) as the inert shell suppresses quenching by MPR. 27,28 Also, there is a stronger deviation from single exponential decay for Eu 3+ in the core-only NCs. This deviation can be appreciated by comparing the fit residuals that show a systematic deviation for the initial part of the core-only decay curves.…”