Nanowires represent a class of quasi-one-dimensional materials, in which carrier motion is restricted in two directions so that they usually exhibit significant photochemical, photophysical, and electron-transport properties which differ from that of bulk or nanoparticle materials.[1±11] In the last decade, many important materials have been prepared in the form of nanorods or nanowires to generate some unexpected properties[2±5] based on which, many new potential applications have been explored. For example, wellcontrolled and monodisperse CdSe nanorods can be used in solar cells,[2] and can form liquid-crystal phases with orientational order and positional disorder in organic solvents;[3] single-crystalline, well-defined ZnO nanowires can serve as natural resonance cavities, and well-aligned ZnO nanowire arrays may serve as room-temperature ultraviolet nanolasers.[4] Along with chemical composition and crystal structure, shape and dimensionality are now regarded as particularly important factors that influence the chemical and/or physical properties of materials. As a consequence of their unique electronic structures and the numerous transition modes involving the 4f shell of their ions, lanthanide compounds usually have outstanding optical, electrical, and magnetic properties,[12±22] and have been widely used as high-quality phosphors,[12] up-conversion materials,[13] catalysts,[14] and time-resolved fluorescence (TRF) labels for biological detection.[15] There have been extensive studies regarding lanthanide chemistry at bulk or atomic levels,[16±19] and the synthesis of lanthanide monothiooxides,[20] lanthanide-doped oxides or sulfides, organolanthanide compounds, the complexation behavior of lanthanide ions or atoms,[16,17] and the emission phenomena from lanthanides when bound to biomolecules (including calcium-binding proteins and nucleic acids).[18,19] Very recently, the synthesis of lanthanide oxide[21] and fluoride[22] nanoparticles with enhanced luminescence and photomagnetic properties has also been reported. However, to the best of our knowledge, few studies have focused on the synthesis of nanowires or nanorods of lanthaniderelated compounds. Such materials would be of great significance because of the possible novel properties induced by their reduced dimensionality. Herein, we report the synthesis of lanthanide hydroxide nanowires (La(OH)3, Pr(OH)3, Nd(OH)3, Sm(OH)3, Eu(OH)3, Gd(OH)3, Dy(OH)3, Tb(OH)3, Ho(OH)3, Tm(OH)3, and YbOOH) through a facile solution-based hydrothermal synthetic pathway. The synthesis of Ln(OH)3 nanowires was based on the preparation of colloidal Ln(OH)3 at room temperature, with subsequent hydrothermal treatment at 180 8C for about 12 h. Figure 1A shows typical XRD patterns for La(OH)3 nanowires. All of the reflections could be readily indexed to the hexagonal phase (space group P63/m (no. 176)) of La(OH)3

Synthesis and Characterization of Lanthanide Hydroxide Single‐Crystal Nanowires

Three-dimensional flowerlike Lu2O3 and Lu2O3:Ln3+ (Ln = Eu, Tb, Dy, Pr, Sm, Er, Ho, Tm) microarchitectures have been successfully synthesized via ethylene glycol (EG)-mediated hydrothermal method followed by a subsequent heat treatment process. X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectra, thermogravimetric and differential thermal analysis, elemental analysis, inductively coupled plasma atomic absorption spectrometric analysis, ion chromatogram analysis, X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy, photoluminescence spectra as well kinetic decays, and cathodoluminescence spectra were used to characterize the samples. Hydrothermal temperature, EG, and CH3COONa play critical roles in the formation of the lutetium oxide precursor microflowers. The reaction mechanism and the self-assembly evolution process have been proposed. The as-formed lutetium oxide precursor could transform to Lu2O3 with their original flower...

Self-Assembled 3D Flowerlike Lu2O3 and Lu2O3:Ln3+ (Ln = Eu, Tb, Dy, Pr, Sm, Er, Ho, Tm) Microarchitectures: Ethylene Glycol-Mediated Hydrothermal Synthesis and Luminescent Properties

Platelike high-quality ${\mathrm{NaYbS}}_{2}$ rhombohedral single crystals with lateral dimensions of a few mm have been grown and investigated in great detail by bulk methods such as magnetization and specific heat, but also by local probes such as nuclear magnetic resonance (NMR), electron-spin resonance (ESR), muon-spin relaxation ($\ensuremath{\mu}\mathrm{SR}$), and inelastic neutron scattering over a wide field and temperature range Our single-crystal studies clearly evidence a strongly anisotropic quasi-two-dimensional magnetism and an emerging spin-orbit entangled ${J}_{\mathrm{eff}}=\frac{1}{2}$ state of Yb towards low temperatures together with an absence of long-range magnetic order down to 260 mK In particular, the clear and narrow Yb ESR lines together with narrow $^{23}\mathrm{Na}$ NMR lines evidence an absence of inherent structural distortions in the system, which is in strong contrast to the related spin-liquid candidate ${\mathrm{YbMgGaO}}_{4}$ falling within the same space group $R\overline{3}m$ This identifies ${\mathrm{NaYbS}}_{2}$ as a rather pure spin-$\frac{1}{2}$ triangular-lattice magnet and a putative quantum spin liquid

/pdf/naybs-2-a-planar-spin-1-2-triangular-lattice-magnet-and-41ptml3kor.pdf

NaYbS 2 : A planar spin- 1 2 triangular-lattice magnet and putative spin liquid

Large-scale GdVO4:Eu3+ nanowires with diameters of about 15 nm and lengths of several micrometers were achieved by a facile hydrothermal method in the presence of disodium ethylenediamine tetraacetate (Na2H2L). The influences of several parameters, such as pH value, reaction temperature, and molar ratio of Na2H2L to Gd3+ on the final products were investigated. The formation mechanism of the as-obtained GdVO4:Eu3+ nanowires is proposed on the basis of time-dependent experiments. It is found that the organic additive Na2H2L, which acts as a shape modifier, has a dynamic effect by adjusting the growth rates of different facets, resulting in the formation of the GdVO4:Eu3+ nanowires. The luminescent spectrum of GdVO4:Eu3+ nanowires shows the strong characteristic dominant emission of the Eu3+ ions at 614 nm.

Facile Hydrothermal Synthesis and Luminescent Properties of Large-Scale GdVO4:Eu3+ Nanowires

Solvothermal synthesis of La(OH)3 sol and microwave radiation drying of La(OH)3 nanorods were employed for the first time to synthesize La2O3 nanorods with diameters around 10 nm and lengths up to 200 nm. The resulting products were characterized with XRD, TEM and HRTEM. Microwave radiation drying was found to be more effective to maintain the morphologies of nanorods than conventional drying.

https://iopscience.iop.org/article/10.1088/0957-4484/15/9/027/pdf

Sol–solvothermal synthesis and microwave evolution of La(OH)3 nanorods to La2O3 nanorods

Ternary alkali-metal–rare-earth-metal sulfides, MRES2(M = Li, Na, K; RE = Y, La–Yb) were prepared by heating RECL3and M2S under an H2S–N2 atmosphere at 750–800 °C for 10 min. The ternary sulfides form thin, mostly coloured plates. The structures were characterised by X-ray powder diffraction, which revealed high-temperature cubic modifications for LiHoS2 and LiErS2. The disordered cubic form (NaCl type) was observed for LiLnS2(Ln = Pr–Er) and NaLnS2(Ln = La–Nd), while the ordered rhombohedral form (α-NaFeO2 type) was observed for LiYbS2, NaLnS2(Sm–Yb) and KLnS2(La–Yb). Alkali-metal–rare-earth-metal sulfides may also be synthesized from the rare-earth-metal chloride and alkali-metal halide under comparable conditions. Similarly, thermolysis of the rare-earth-metal sesquisulfide (γ-RE2S3), oxysulfide (RE2O2S) or oxychloride (REOCL) with M2S or MCI in an atmosphere of H2S-N2 gives MRES2. The materials were characterised by powder X-ray diffraction, scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDXA), Raman, infrared, magnetic moments and microanalysis.

John P. Cotter

Papers

New routes to alkali-metal–rare-earth-metal sulfides