Shape-selected synthesis, characterization and optical properties of KMnF3 micropolyhedra, microspheres and hollow microspheres

Zhang

ACS Appl. Mater. Interfaces

2013

In this work, the uniform bundle-shaped microtubes composed of six half-pipes are synthesized for the first time in hydrothermal solutions via an intentional delayed phase transition pathway induced by Mn(2+) doping. The structural and kinetic factors that govern the phase and shape evolution of NaYF4 microcrystals have been carefully studied, and the influences of Mn(2+) to RE(3+) ratio, the amount of trisodium citrate, and the pH value in conjunction with the intrinsic character of RE(3+) ions on the phase and shape evolution are systematically discussed. It is found that the proper Mn(2+) to RE(3+) ratio is mainly responsible for delayed phase transition process and induces interior density gradient of solid aggregate for creating hollow bundle-shaped microtubes. While the amount of trisodium citrate and the pH value are the keys for the shape control of the NaYF4 microcrystals such as prismatic microtubes, prismatic short rods, thin plates, and particles. The up and downconversion emissions were obtained independent of whether α- or β-NaYF4:Er(3+)/Yb(3+) samples doped with Mn(2+), but the significant tuning of output color was only obtained in cube NaYF4 nanoparticles rather than in hexagonal microtubes via adjusting the amount of Mn(2+) ions. These spectral measurements and EDX analyses indicate that the distribution or concentration of Mn(2+) in hexagonal phase solid solution has changed, which supports Ostwald ripening growth mechanism and rules out agglomeration or oriented attachment growth mechanism. We designed crystal growth mode by simply addition of dopant may provide a versatile approach for fabricating a wide range of hollow nano/microcrystals and thus bring us a clearer understanding on the interaction between the dopant reagents and the nano/microcrystals.

Section: Resultsmentioning

confidence: 82%

Section: ■ Results and Discussionmentioning

confidence: 99%

Formation of Bundle-Shaped β-NaYF₄ Upconversion Microtubes via Ostwald Ripening

Zhang

ACS Appl. Mater. Interfaces

2013

Part. Part. Syst. Charact.

“…However, KMnF 3 microcrystals shaped as polyhedra, spheres, or hollow spheres were prepared by Sheng et al using a hydrothermal method (60 °C). Their morphology depended on the reaction conditions.…”

Section: Halide Perovskite Nanoparticlesmentioning

confidence: 99%

Organometal Halide Perovskites: Bulk Low-Dimension Materials and Nanoparticles

González‐Carrero

Galian

Pérez‐Prieto

2015

155

Organometal halide perovskites (hybrid perovskites) contain an anionic metal-halogen-semiconducting framework and charge-compensating organic cations. As hybrid materials, they combine useful properties of both organic and inorganic materials, such as plastic mechanical properties and good electronic mobility related to organic and inorganic material, respectively. They are prepared from abundant and low cost starting compounds. The perovskite stoichiometry is associated with the dimensionality of its inorganic framework, which can vary from three to zero, 3D consisting of corner-sharing MX 6 octahedra, and 0D consisting of isolated octahedra. Small-sized organic cations can fi t into the MX 6 octahedra of the 3D framework and in all dimensions organic cations surround the inorganic framework. Regarding the low dimensionality in the material, this refers to at least one of its dimensions being shorter than approximately 100 nanometers. These materials should be considered as genuine nanomaterials or as bulk materials depending on whether they have three or less than three dimensions on the nanoscale, respectively. In principle, hybrid perovskite nanoparticles can be prepared with different shapes and with inorganic framework dimensionalities varying from 0D to 3D, and this also applies to the bulk material. This report is mainly focused on the unique properties of organometal halide perovskite nanoparticles.

Caesium manganese fluoride cubic-perovskite nanoparticles – synthesis, luminescence and magnetic properties

Fellner

Lauria

2023

J Sol-Gel Sci Technol

Lead halide perovskite materials have outstanding optical properties such as color purity and efficient fluorescence in the visible spectrum. However, the toxicity of lead makes the synthesis, processing, use and disposal of such materials hazardous for humans and the environment. Therefore, the exploration of different perovskite materials containing the transition metal Mn(II) and fluoride anions might lead to more appealing alternatives towards more sustainable and environmentally friendly functional materials. Nanocrystals primarily consisting of cubic CsMnF3 – a polymorph so far only reported at pressures of 3 × 104 bar – were synthesized from manganese(II) acetate and caesium fluoride precursors using a heating-up approach in high boiling organic solvents. The concentration of defects could be tuned by changing the amount of fluorinating precursor CsF, with more defects produced when an excess of CsF was used in the synthesis. The structure, morphology, optical and magnetic properties of the product nanoparticles were studied. Due to their X-ray sensitized fluorescence, likely caused by defects in the crystal structure, these materials are promising for potential applications in dosimetry. Graphical Abstract CsMnF3 nanocrystals were synthesized by a heating-up method using stoichiometric or excess quantities of the fluoride precursor CsF to control the concentration of defects (CMF and CMF-d). The obtained nanoparticles exhibited X-ray sensitized luminescence, enhanced by a factor of up to 3.75 after irradiation with X-rays for 2 h.