Pr³⁺:BaY₂F₈ Crystal Nanoparticles (24 nm) Produced by High-Energy Ball Milling: Spectroscopic Characterization and Comparison with Bulk Properties

Abstract

Nanocrystals (NC) of Pr 3+ :BaY 2 F 8 with average diameter of 24 nm have been successfully prepared by highenergy ball milling. The method is versatile, easily scalable, and does not require the use of surfactants or catalysts. NC were prepared starting from high quality single crystal pieces, and their spectroscopic features are analyzed and compared with those of a single bulk crystal. Under 445 nm excitation, we recorded the 10 K and room temperature emission spectra of the two samples. The spectra show the same peak positions and width, and this means that the milling process does not introduce substantial modifications to the crystal structure. Besides, there are strong differences in the relative intensity of the lines emitted toward different lower lying levels in the two samples. In particular, the high-energy transitions seem to be hyper intense in the NC with respect to the bulk sample. On the contrary, the emission lines that end at excited levels are less intense in the NC. In addition, the time evolution of the 3 P 0 decay shows striking differences between the nanosized materials and the bulk sample. Despite the exponential decay of the latter luminescence (τ = 43 μs), NC possess a strong nonlinear component with a lifetime much shorter than in the bulk. Calculations show that nearly 89% of the excited ions contribute to the short-time decay, which is attributed to ions residing near the NC surface.

Preparation of rare-earth doped NaYF4 luminescent nanoparticles by a high-energy ball milling process

“…It involves production of nanoscale particles from bulk or microcrystalline powder via mechanical or laser-assisted treatment. [44][45][46][47] By combining impact and friction, mechanical milling can be used both for activation of solid-state reactions and formation of new compounds, as well as for milling of bulk materials to nanoscale. 48 Besides, this "green" and versatile approach is implemented under ambient conditions not requiring high temperatures and pressures.…”

“…Previously, the high-energy ball milling method has been successfully applied both for mechanochemical synthesis of various binary and MF x -RF 3 (M = Li-K; Ca-Ba) complex fluorides from individual components [56][57][58][59][60][61] and PL fluoride NPs produced by nanodispergation of complex micropowders. 44,45,[62][63][64][65] At the same time, the energy-and time-consuming milling process often leads to formation of highly polydisperse NPs and product contamination with materials of the attritor/mill. In addition, the fluorides show a tendency to mechanohydrolysis, thus complicating the large scale fabrication of relevant NPs.…”

YF3:RE3+ (RE = Dy, Tb, Eu) Sub-microstructures: Controllable Morphology, Tunable Multicolor, and Thermal Properties

“…In the field of modern materials science and technology, controlling the size, phase, shape, and dimensionality of inorganic nano/microparticles remains the key issue and research focus, due to its potential applications in many fields, including nanoelectronics, information storage, catalysis, biosensors, clinical therapy, and bioimaging. − To date, a number of synthesis techniques have been developed to synthesize nano/microcrystals with uniform phase, dimension, and morphology, such as the solid-state combinatorial chemistry method, the molten-salt approach, hydrothermal and solvothermal techniques, the sol–gel route, and chemical vapor synthesis. , Among all the methods, the hydrothermal method is considered as the most effective and convenient way to control the morphologies and architectures of inorganic materials . Moreover, the hydrothermal treatment is relatively mild, and it is simple and easy to obtain a large amount of products.…”

Controlling the Morphology and Size of GdF3:RE3+ (RE = Dy, Tb, and Sm) by pH Value: Growth Mechanism, Energy Transfer, and Luminescent Properties

“…In recent years, there has been great interest in studying and developing rare earth (RE) luminescence materials on account of their potential applications, such as liquid lasers, photoelectric devices, nanolabels, multimodality bioimaging contrast agents, television tubes, mobile telephone screens, fluorescent lamps, and the promising white light-emitting diodes. − Among all kinds of RE luminescence materials, RE fluoride (such as GdF 3 ) luminescence materials have many excellent properties, for instance, long lifetime, lower energy consumption, high luminous efficiency, and environmentally friendliness, and so on. − Therefore, GdF 3 is considered to be a prominent luminescent host material.…”